Tropaeline-O-Alkali-Pt-Graphite based H-Shaped Photogalvanics Cells: Current-potential stability & Hysteresis curve for solar energy conversion and storage

Tropaeline-O-Alkali-Pt-Graphite based H-Shaped Photogalvanics Cells: Current-potential stability & Hysteresis curve for solar energy conversion and storage | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Tropaeline-O-Alkali-Pt-Graphite based H-Shaped Photogalvanics Cells: Current-potential stability & Hysteresis curve for solar energy conversion and storage RAJENDRA KUMAR, Dr. POORAN KOLI This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7502096/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Solar energy can be harnessed and converted into power using various methods such as photo-galvanic cells. In this research, authors have investigated photo-galvanic cells based on Tropaeline-O sensitizer, oxalic acid reductant, Benzalkonium chloride surfactant, NaOH alkali, Pt and graphite electrodes in the H-shaped cell design covered by black PVC electrical tape for realizing further enhanced and stable electrical output of the cell. Observed electrical parameters of the cell are as maximum potential 680 mV, open-circuit potential (V oc ) 671 mV, maximum current 6500 µA, short-circuit current (i sc ) 1000 µA, and power 122.0 µW. The variation and stability of V oc and i sc over time has also been studied after fully charging the cell and keeping illumination of the cell on. The value of V oc and i sc has been found quite steady and stable for over a very long time, i.e., potential changes from 809 mV to 803 mV in 485 minutes, from 809 mV to 700 mV in 1448 minutes, and current changes from 1100 µA to 900 µA over 420 minutes. The forward direction curve and backward direction curve (current–potential) almost superimposes on each other giving almost negligible area of the hysteresis loop showing quite good stability (current-potential) of photo-galvanic system. H-Shape Photogalvanic cell Tropaeline-O Alkali Pt-Graphite Electrode current -potential stability & Hysteresis curve Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 1. Introduction Diminishing fossils fuels, continuously worsening climatic conditions, and uninterrupted rise in assured energy needs has necessitated development of alternative energy technologies like solar power techniques with storage [1]. Solar power can be harvested directly through the different solar power techniques such as the Organic solar cells [ 2, 3 ], perovskite cells [ 4-6 ], polymer cells [7], dye sensitized solar cells [8-11], photovoltaic cells [ 5 ], photogalvanic cells [12], etc. In this regard, the photogalvanic solar cells have some peculiar characteristics of both solar energy conversion and storage. Photogalvanic cells are based on the ‘photogalvanic effect’ (i.e., modified ‘Becquerel effect’), in whichthe electrode potential owes its origin to the photo-induced chemical process and shift in the redox equilibrium occurring in the bulk electrolyte [13]. Various studies have been reported on the optimal configuration and ultimate efficiencies of the photogalvanic cells [14]. Various dye/pigment sensitizers and other parameter based photogalvanic cells have been reported [ 15-39 ]. The dye/pigment sensitizers like Congo Red dye [15], Sudan-I dye [16], Naphthol Green B dye [17], Spinach extract ( chlorophyll ‘a’ ) [18-20], Fast Green FCF dye [21] , Methylene Blue dye [22], Direct Yellow-9 dye [23], Safranine-O dye [24,25], Brilliant Cresyl Blue dye [26], Methylene Blue dye [27], Metanil Yellow dye [28], Toluidine Blue dye [29], Rhodamine B [30], Indigo Carmine [31], [Cr 2 O 2 S 2 (1-Pipdtc) 2 (H 2 O) 2 ] inorganic dye [32], Sudan-I [33] , fast green FCF dye [34], Carmoisine ‘A’ dye [35], Titan Yellow dye [36], etc. have been explored in photogalvanics. Other parameter based photogalvanic cells like high energy throughput using photogalvanic solar techniques and environmentally benign chemical system [37], comparative photogalvanic study of various alkali materials in the transparent H-cell design [38], exploratory insight into the photogalvanics of the complete electrolyte and its individual chemical components [39], etc., have also been reported. A literature survey reveals that various chemical and physical variables are key determinants of the optimized and enhanced performance of the photogalvanic cells. The sensitizer material is the main constituent of the photogalvanic cells. The higher diffusion of the sensitizer molecules and the cost/conductivity/catalytic activity/redox property/robustness of the electrode materials is the key for having efficient solar energy harvesting process through the durable photogalvanic cells. The light absorbing dye materials having very low molecular weight and higher diffusivity with low cost and robust graphite counter electrodes have not received much attention of the researchers. Tropaeline-O dye (characterized by potentially higher diffusivity and photo-stability) is a low molecular weight material, and it has been widely used as an indicator in the Pb-C batteries [40]. Tropaeline-O dye with saturated calomel electrode (a delicate and costly electrode) has also found limited applications in photogalvanic cells with quite similar electrical parameters (potential 998 mV, current 3200 μA, and power 829.5 μW) at all illumination window sizes [41]. But, the saturated calomel electrode is a delicate and costly electrode (local cost ~35 USD/piece), and therefore, not suitable for fabrication of low cost and sustainable Tropaeline-O dye based photo-galvanic cells. So far reported studies on photogalvanic cells have exploited SCE/Combination electrodes as the counter electrodes. These electrodes are very delicate, non-durable and costly for realizing the efficient and durable photo-galvanic cells. Thus, to fill this research gap in the research area of photo-galvanic cells, the present study exploiting tropaeline-O dye sensitizer with low cost and robust graphite counter electrode has been undertaken.The literature survey also reveals that ‘the tropaeline-O dye sensitizer-Oxalic acid reductant- Benzalkonium chloride surfactant chemical couple’ with low cost and robust graphite counter electrode has not attracted the attention of photogalvanicists so far. It is also reported that the use of alkaline medium and small Pt electrodes is conducive for good electrical output of the photo-galvanic cells [1, 13, 15-22]. The efficacy of the graphite electrodes is extensively reported for dye-sensitized solar cells, i.e., a class of cells exploiting dye as sensitizers as in the photo-galvanic cells [42-47] . Therefore, the authors have used the combination of “The Tropaeline-O sensitizer, oxalic acid reductant, Benzalkonium chloride surfactant, NaOH alkali, H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm, total 30 ml electrolyte use) covered by RS PRO black PVC electrical tape, very small Pt working electrode (0.5 cm × 0.5 cm), and graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm)” for realizing further enhanced and stable electrical output. In present research, The Tropaeline-O sensitizer, oxalic acid reductant, Benzalkonium chloride surfactant, NaOH alkali, H-shaped tube and low cost and robust graphite counter electrode based photogalvanic chemical system has shown the optimum value of the cell’s electrical parameters, as follows; dark potential 389 mV, maximum potential (V max ) 680 mV, open-circuit potential (V oc ) 671 mV, maximum current (i max ) 6500 µA, short-circuit current (i sc ) 1000 µA, current at power point (i pp ) 1000 µA, potential at power point (V pp ) 122 mV, power at power point (P pp ) 122.0 µW, fill factor (FF) 0.18, and conversion efficiency (CE) 2.73 %. 2. Materials and Method 2.1. Materials used - The chemicals, Tropaeline-O dye, Oxalic acid, Benzalkonium Chloride, and NaOH have been used as photo-sensitizer, reductant, surfactant, and alkali medium, respectively Tropaeline-O dye: The characteristics of the Tropaeline-O dye (Loba Chemie Pvt. Ltd, Mumbai, India) are as, synonyms names -Acid Orange 6, Resorcinol Yellow; M.F. C 12 H 9 N 2 NaO 5 S; M.W. 316.27 gm/mol; physical state, orange to dark brown powder; soluble in water, alcohol; λ max 488 nm- 492 nm; pH transition range, 11.1 (yellow color) to 12.7 (red-orange color); C.I. No.14270; M.R.P. INR 708/5 gm (Indian Currency); used also as pH Indicator, etc. The Tropaelin-O dye ( Scheme-I ) has been used as an indicator to indicate the need for replacement of the Zn electrode on its consumption in the carbon-zinc batteries. The Tropaelin-O dye as indicator produces a bright red-orange color in a potassium hydroxide alkali solution showing that replacement is needed in a few weeks after the color signal is observed [40]. The Tropaeline-O (TPO) is an azo-aromatic dye susceptible to the microbial degradation (fungi induced) [48] and photo catalytic degradation seeing color change from greenish yellow color to orange color, red color, violet color and brown color [49]. Preparation of solution: M/500 Stock solution of the Tropaeline-O (TPO) has been prepared by weighing 0.07 gm of Tropaeline-O (TPO) compound and by dissolving it in 100 ml of the singly distilled water (Scheme II). Benzalkonium chloride (BAC): The characteristics of the Benzalkonium chloride (Ases Works Laboratory Chemical Davison, Jodhpur, Rajasthan, India); chemical formula [C 6 H 5 CH 2 N (CH 3 ) 2 RCl], R is mixture of the alkyls (R 8); Physical state pale yellow liquid; Soluble in water, etc. The Benzalkonium chloride (BAC) surfactant ( Scheme-III ) can be easily removed from waste water using its (BAC) oxidation in the aqueous solution by S 2 O 8 2- /Fe 2 + process. The microbial fuel cell system can be applied as bio-sensor for the toxicity test of BAC degradation products [50]. The BAC adversely affects the metabolism of the microbial organisms [50]. This property of the BAC is an additional advantage to be exploited once the BAC based PG electrolyte is exhausted and discarded for use as an antimicrobial agent. Oxalic acid: The characteristics of the Oxalic acid (Qualigens Fines Chemicals, Mumbai, India) are as, purity 99.5 % [maximum limits of impurities, sulfated ash 0.1 %, chloride (Cl -1 ) 0.005 %, sulfate (SO 4 -2 ) 0.02 %, heavy metals (Pb) and iron (Fe) 0.005 %); M.F. C 2 H 6 O 6 ; chemical formula (COOH) 2 .2 H 2 O; M.W. 126.06; white crystalline solid: soluble in water; aqueous solution colorless, etc. ( Scheme-IV ). Preparation of solution: M/10 Stock solution of the Benzalkonium chloride surfactant has been prepared by weighing 2.55 gm of Benzalkonium chloride surfactant compound and by dissolving it in 100 ml of the singly distilled water . Sodium hydroxide : The characteristics of the sodium hydroxide (Ases Works Laboratory Chemical Davison, Jodhpur, Rajasthan, India), chemical formula (NaOH), M.W. 40 gm/mol, purity 98 %, white solid, soluble in water, density 2.13 gm/cm 3 . The solutions of the all chemicals have been prepared in the singly distilled water. The stock solutions as M/500 Tropaeline-O dye sensitizer, M/100 Oxalic acid reductant, M/10 Benzalkonium Chloride surfactant, and 4M NaOH have been prepared, and stored in the amber colored vessels to protect them from the sunlight. 2.2. Apparatus used - The apparatus as the digital pH meter model no. 335 ( Systronics India Ltd., Ahmedabad, India) for measuring the potential in millivolt (mV), a platinum electrode as the negative terminal of the cell, a graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), as the positive terminal of the cell, H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm, total 30 ml electrolyte use) covered by RS PRO black PVC electrical tape, for accommodating the electrolyte and a 250 wattage incandescent tungsten filament bulb for getting artificial sunlight, and a HTC Instrument LX-101A Light Meter Luxmeter (accuracy: ± 5 percent of the reading) for measuring the sunlight intensity, have been used. The platinum electrode has been used as working electrode as the authenticated data exists on its efficacy in the photogalvanic cells [1]. It is chemically inert, and also very resistant to the corrosion. It is also readily available in a ready-to-use form and has robust ability to withstand the damage. 2.3. Method - The required volume of the electrolyte (consisting of the dye sensitizer, reductant, surfactant, alkali, water) is filled in the a H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm, total 30 ml electrolyte use) covered by RS PRO black PVC electrical tape, and both the electrodes (Pt and graphite) are dipped in the electrolyte solution. All the apparatus are connected in a circuit as shown in the schematic of the experimental set-up ( Fig.1 ). In the beginning, the circuit is kept open and the cell is placed in the dark condition to obtain a stable potential (dark potential-V dark ). After that the cell is charged by illuminating the electrolyte solution with the artificial sunlight while keeping the circuit open The value of photo-potential is noted at different time intervals. During the illumination, a highest potential called maximum potential (V max ) is obtained. Thereafter, a stable potential value called open-circuit potential-V oc (V oc is a bit lower than V max ) is obtained, and at this stage, the cell is considered as fully charged. Thereafter, the illumination of the cell is cut-off. After that the circuit is closed. The highest current obtained immediately on closing the circuit at resistance zero is noted and designated as maximum current (i max ). After some time the current acquires a quite stable value called short-circuit current (i sc ). The resistance of the circuit is changed by using the potentiometer. The i-V characteristic of the cell is studied (by varying the circuit resistance, zero current is obtainable at highest resistance) by varying the current value from i sc to zero value and noting the corresponding potential value. The highest product of the current and corresponding potential value is called power at power point (maximum power extractable from the cell, Ppp). The current and potential at power point are designated as current at power point (i pp ) and potential at power point (V pp ), respectively. The charging time (t) is calculated as, charging time = (time at which V voc is obtained)-(time at which illumination is started). The formula, (i pp ×V pp )/(i sc ×V oc ) and (i pp ×V pp ×FF×100%)/(A×P) has been used for calculation of the fill factor (FF) and conversion efficiency (CE), respectively. Where, ‘A’ and ‘P’ is Pt electrode area (cm 2 ) and average artificial sun intensity (3.24 mWcm -2 ), respectively. The power storage capacity of the cell is studied in terms of the half change time (t 0.5 ), which is defined as the time duration in which the power of the cell decreases to half of the maximum power during the extraction of power from the cell in dark at a characteristics external load (resistance). The initial pH of the solution taken in the cell has been calculated by formula, pH 14-pOH [15-32]. 3. Results & Discussions The overall performance of the 30 PG (photogalvanic) cells containing the Tropaeline-O dye as the photo-sensitizer, Benzalkonium chloride as surfactant and Oxalic acid as the reductant has been studied to get the optimum cell performance at an optimal value of the cell fabrication variables. 3.1. Study of potential variation with time during illumination of the cell, i-V characteristics, determination of maximum power extractible from the cell, power storage capacity 3.1.1. Potential variation with time during illumination Each photogalvanic cell having solutions of the Tropaeline-O dye sensitizer, oxalic acid reductant, benzalkonium chloride surfactant, and NaOH alkali is illuminated with the artificial sunlight intensity. Each cell has different amount of chemicals, but the pattern of change of the photo-potential with illumination time is same ( Fig.2 ), and the values of maximum potential (V max max)))) ) and open-circuit potential (V oc ) is different ( Table-1, 4-7). Table 1. Change of the cell potential with time during illumination of the cell for its charging Time (min.) # 1 2 3 7 8 9 11 14 15 22 Potential (mV) 389 388 395 430 503 553 675 680 (V max ) 677 671 (V oc ) # [Tropaeline-O]2.66 × 10 -5 M, [Benzalkonium chloride]2.21×10 -2 M, [Oxalic acid]9.9× 10 -4 M, pH 12.98 , Pt electrode size 0.5cm×0.5cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H -shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm) diffusion length (D L ) 4.0 cm, sunlight intensity 3.24 mWcm -2 3.1.2. i-V characteristics of the cell The model of the i-V characteristics of each cell is same ( Fig.3 ). The Fig. 4 shows inverse relation between current and potential during i–V characteristics study of the each cell. The i-V characteristics show that highest power is extractable from the cell at a characteristic current, potential and external load resistance ( Table 2 ). Table. 2. The change of the potential and power with the current of PG cell system (i-V characteristics of the cell during illumination). Current (µA) Potential (mV)* Power (µw) # Current (µA) Potential (mV)* Power (µw) # 1000(i sc ),(i pp ) 122(V pp ) 122.0(P pp ) $ 400 189 75.6 900 128 115.2 300 215 64.5 800 130 104.0 200 233 46.6 700 135 94.5 100 294 29.4 600 155 93.0 0 350 0 500 180 90.0 - - - Variation of the power and potential with current during i–V characteristics study; (a)current vs potential (a decreasing linear curve),(b)current vs power (a parabolic curve with maxima showing max. power 917.7 µw extractable from the cell at a characteristics external load resistance, # [Tropaeline-O]2.66 × 10 -5 M, [Benzalkonium chloride]2.21×10 -2 M, [Oxalic acid]9.9×10 -4 M, pH 12.98, Pt electrode size 0.5cm×0.5 cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm) diffusion length (D L ) 4.0 cm, sunlight intensity 3.24 mWcm -2 For this photogalvanic chemical system, the optimum value of the cell’s electrical parameters is as: dark potential 389 mV, maximum potential (V max ) 680 mV, open-circuit potential (V oc ) 671 mV, maximum current (i max ) 6500 µA, short-circuit current (i sc ) 1000 µA, current at power point (i pp ) 1000 µA, potential at power point (V pp ) 122 mV, power at power point (P pp ) 122.0 µW, fill factor (FF) 0.18, conversion efficiency (CE) 2.73 %. The optimal cell performance has been obtained at following optimum cell fabrication parameters: [Tropaeline-O] 2.66 × 10 -5 M, [Benzalkonium chloride] 2.21 × 10 -2 M, [Oxalic acid] 9.9 × 10 -4 M, pH 12.98, Pt electrode size 0.5 cm × 0.5 cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm) diffusion length (D L ) 4.0 cm, sunlight intensity 3.24 mWcm -2 , 20.90 o C room temperature, and pre-illuminated electrolyte solution temperature 21.0 o C. 3.1.3. Mechanism The photo-electrochemistry of the oxalic acid reductant solution alone, Benzalkonium chloride surfactant solution alone, and the electrolyte solution (having mixture of the dye, reductant, and alkali) has been studied in the cell to propose a most plausible mechanism (with the help of published literature) for the photo-generation of current. The illumination of the electrolyte solution having dye sensitizer along with the reductant and alkali shows development of the photo-potential and photo-current. The dark potential is also not due to the dye alone, but as a result of the contribution of reductant, and surfactant as well. On the basis of the published literature [2, 15-30] the most plausible mechanism for the photo-generation of the current using Tropaeline-O dye sensitizer (TPO)-Oxalic acid reductant-Pt-Graphite photogalvanic system is proposed as below- On illumination of the electrolyte containing the dye, the formation of excited state of the dye photo sensitizer Tropaeline-O molecule leave a vacancy in its ground state, This vacancy is filled by an electron donated to TPO molecule from the Oxalic acid OA reductant molecule leading to an excess electron in the higher energy state of the TPO molecule. This excess electron is transferred to Pt electrode (working electrode placed in the illuminated chamber) as accommodation of this excess electron is difficult as it causes high instability of TPO molecule. This excess electron moves through an external circuit to the graphite electrode (positive terminal of the cell), where it (electron) may be accepted by the dye molecule present in bulk electrode around the graphite to form the leuco/semi-form (of dye molecule).The dye molecule (leuco/semi-form) and reductant molecule (oxidized) combine to give original dye and reductant molecules [51]. The photogalvanic system based on the TPO-OA-BAC is estimated to be a cyclic light-induced power generator with several reversible cycles. The semi/leuco reduced states of the TPO molecules are the electro-active species in the Pt electrode region, and the TPO molecules itself are main electro-active species in cell graphite region [52]. This fact is also supported by the published work of Kaneko and Yamada [53]. That the leuco/or semi reduced form of the dyes, and the dyes itself are the main electro-active species at the illuminated working electrode and the non-illuminated graphite counter electrode, respectively [54]. The energy stored in the charge separated semi or leuco forms gets converted into the electrical energy by the so-called photogalvanic effect. The most plausible outlines of the mechanistic aspect of the photo-generation of the current is described as below (Also see Fig. 4)- Photo-processes occurring in the electrolyte and on the surface of the Pt electrode : TPO TPO*(S) TPO*(T) (in bulk electrolyte)….. (1) TPO*(T) + OA → TPOˉ (Leuco) + OA + (in bulk electrolyte)….. (2) TPOˉ (Leuco) → TPO + eˉ (Pt electrode) …. (3) Photo-processes occurring in the electrolyte of the graphite region: TPO + eˉ → TPOˉ (leuco) (graphite region) ….. (4) TPOˉ + OA + → TPO + OA (in bulk electrolyte) …. (5) Where, the OA, OA + , TPO*, TPOˉ and eˉ is oxalic acid reductant molecule,oxidized oxalic acid reductant molecule, excited state of the Tropaeline-O dye photosensitizer molecule, semi or leuco form of the Tropaeline-O dye photosensitizer molecule, and electron, respectively. The ISC, ‘T’ and ‘S’ are inter system crossing process, triplet excited state of Tropaeline-O molecule, and singlet excited state of the Tropaeline-O dye photosensitizer molecule, respectively. 3.1.4. Storage capacity of the cell The storage capacity of the cell has been observed as 440 minutes as half change time. The half change time is considered as the time duration in which the value of extracted power at a characteristics external load (resistance) from the cell reduces to the half of initial value (i.e., power at power point) in dark ( Table 3, Fig.5 ). The PG cells are characterized by their inherent power storage capacity. This power storage capacity may be attributed to the generation of the energy rich species like photo-excited sensitizer molecule and semi and /or leuco reduced forms of the sensitizer molecule. These energy rich species have certain average life time. After charging of the cell in sunlight, the illuminating source is cut-off. Thereafter, the power is extracted from the cell in dark conditions. Under dark conditions, the energy stored in the form of energy rich photo-excited species and semi/leuco species is retrieved by their deactivation in cell electrolyte to give current and power as electrical out-put. The kinetics of the photo-decay and deactivation of these excited species here is estimated to be of non-zero order [16]. Table 3. Storage capacity of the cell Time (min.) # Current (µA) Potential (mV) Power (µW) Time (min.) # Current (µA) Potential (mV) Power (µW) 0 1000 122 122 190 900 109 98.1 1 1000 125 125 205 850 108 91.8 2 1000 122 122 240 800 104 83.2 5 1000 121 121 280 800 101 80.8 20 1000 120 120 340 800 92 73.6 50 950 120 114 400 800 86 68.8 80 900 119 107.1 420 750 84 63.0 105 900 118 106.2 440 750 82 61.5(t 0.5 ) 130 900 117 105.3 450 750 81 60.75 150 900 115 103.5 455 750 80 60.50 170 900 112 100.8 - - - - # [Tropaeline-O]2.66 × 10 -5 M, [Benzalkonium chloride]2.21×10 -2 M, [Oxalic acid]9.9×10 -4 M, pH 12.98, Pt electrode size 0.5cm×0.5cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm), diffusion length (D L ) 4.0 cm, sunlight intensity 3.24 mWcm -2 3.2. Study of optimization of the cell performance The optimization of the cell performance has been studied by varying one cell fabrication variable and keeping value of other cell fabrication variables constant. 3.2.1. Effects of variation of the Tropaeline-O dye as photosensitizer on the PG Cells’ electrical performance The effect of variation of the dye Tropaeline-O as photosensitizer on the PG cells’ electrical performance has been studied by fabricating in all five cells. For each cell, the value of used Tropaeline-O dye concentration is different, but the value of other cell fabrication variables (other than Tropaeline-O dye concentration) is same. The highest photo-current is noted at an optimal concentration (i.e., 2.66 × 10 -5 M) of Tropaeline-O dye sensitizer ( Table 4 ). The relation between Tropaeline-O dye sensitizers’ concentration and corresponding current is shown by a parabolic curve with maxima showing highest current at corresponding dye concentration, i.e., optimized Tropaeline-O dye concentration value, 2.66 × 10 -5 M ( Fig.6). The most plausible explanation for the observed results may be attributed to the particle nature of the matter (dye material) and radiations (sunlight). At the lower concentration range of the dye tropaeline-O photo-sensitizer, there will be limited numbers of molecules of the photo-sensitizer for absorbing photons and subsequently donating electrons at the surface of working electrode (Pt electrode). At the higher concentration range of the dye Tropaeline-O photo-sensitizer, there will be large numbers of the molecules of the photo-sensitizer which would hinder the sunlight photons to reach nearby area of the working electrode. The PG cells are diffusion controlled devices in which excited sensitizer molecule, within their excited life, must reach working electrode for photo-generation of the current. The life time of excited species is very small so only limited sensitizer molecules get photo-excited (only those which are very close to Pt) reach Pt electrode. The sensitizer molecules far away from the Pt would not be able to reach (within their life time) Pt and therefore, such molecules would not be able to contribute to the photo-generation of the current from the cell. Table 4. Effects of variation of the Tropaeline-O dye photo-sensitizer concentration the PG Cell system Cell Parameters [Tropaeline-O]×10 -5 M # 0.25 0.30 0.35 0.399 0.45 V dark (mV) 710 512 386 389 394 V max (mV) 720 719 645 680 678 V oc (mV) 685 676 531 671 655 i max (mA) 6000 7500 7000 6500 9000 i eq or i sc (mA) 900 1000 1000 1000 1000 V pp (mV) 23 212 125 122 56 P pp (mW) 13.8 106.0 62.5 122.0 28 i pp (mA) 600 500 500 1000 500 t (min.) 17 15 15 22 30 CE (%) 0.03 1.20 0.76 2.73 0.14 FF 0.02 0.09 0.09 0.18 0.04 # [Benzalkonium chloride]2.21×10 -2 M, [Oxalic acid]9.9×10 -4 M, pH 12.98,Pt electrode size 0.5cm×0.5cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm) diffusion length (D L ) 4.0 cm, sunlight intensity 3.24 mWcm -2 3.2.2. Effects of variation of the Oxalic acid reductant concentration on the PG cells’ electrical performance The effect of the variation of the Oxalic acid reductant on the PG cells’ electrical performance has been studied by fabricating in all five cells. For each cell, the value of used Oxalic acid reductant concentration is different, but the value of other cell fabrication variables (other than Oxalic acid reductant concentration) is same. The highest photo-current is noted at an optimal concentration (i.e., 2.97 × 10 -3 M) of Oxalic acid reductant ( Table 5 ). The relation between Oxalic acid reductants’ concentration and corresponding current is shown by a parabolic curve with maxima showing highest current at corresponding Oxalic acid reductant concentration, i.e., optimized Oxalic acid reductant concentration value, 2.97 × 10 -3 M ( Fig.7). The most plausible explanation for the observed results may be attributed to the particle nature of the matter (Oxalic acid reductant material) and radiations (sunlight). At the lower concentration range of the Oxalic acid reductant, there will be limited numbers of molecules of the Oxalic acid reductant to reduce the limited number of dye molecules producing limited number of semi/leuco dye molecules. Subsequently, the limited number of semi/leuco dye molecules shall transfer limited numbers of electrons at the surface of working electrode (Pt electrode) leading to lower photo-current generation. The higher concentration of the reductant oxalic acid may inhibit the movement of molecule of the dye Tropaeline-O towards the electrodes in the desired time limit and may also increase back electron transfer from the molecule of dye Tropaeline-O to the reductant oxalic acid molecules. At the higher concentration range of the Oxalic acid reductant, there will be large numbers of the molecules of the Oxalic acid reductant which would hinder the sunlight photons to reach nearby area of the working electrode leading to the photo-excitation of limited numbers of the sensitizer molecules in the electrolyte adjacent to the working electrode. The recombination process (involving combination of the reduced dye molecule and the oxidized reductant molecule) disfavors the photo-generation of the current. At higher side of the reductant concentrations, this recombination process is facilitated causing reduced current generation. Table 5. Effects of variation of the Oxalic acid reductant concentration on PG Cell Cell Parameters [Oxalic acid]×10 - 3 M # 2.50 2.97 3.50 4.00 4.50 V dark (mV) 472 389 433 412 450 V max (mV) 695 388 704 668 680 V oc (mV) 640 680 680 664 662 i max (mA) 10000 6500 7000 8500 6000 i eq or i sc (mA) 700 1000 1000 700 600 V pp (mV) 129 122 222 373 19 P pp (mW) 51.6 122.0 111.0 113.7 11.40 i pp (mA) 400 1000 500 300 600 t (min.) 16 22 15 15 22 CE (%) 0.11 2.73 2.23 3.37 0.04 FF 0.73 0.18 0.16 0.24 0.02 # [Tropaeline-O]2.66 × 10 -5 M, [Benzalkonium chloride]2.21×10 -2 M, pH 12.98, Pt electrode size 0.5cm×0.5cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm) diffusion length (D L ) 4.0 cm, sunlight intensity 3.24 mWcm -2 3.2.3. Effects of variation of the Benzalkonium chloride surfactant concentration on the PG cells’ electrical performance The effect of the variation of the Benzalkonium chloride surfactant on the PG cells’ electrical performance has been studied by fabricating in all five cells. For each cell, the value of used Benzalkonium chloride surfactant concentration is different, but the value of other cell fabrication variables (other than Benzalkonium chloride concentration) is same. The highest photo-current is noted at an optimal concentration (i.e., 2.21 × 10 -2 M) of Benzalkonium chloride ( Table 6 ).The relation between Benzalkonium chloride concentration and corresponding current is shown by a parabolic curve with maxima showing highest current at corresponding Benzalkonium chloride concentration, i.e., optimized Benzalkonium chloride concentration value, 2.21 × 10 -2 M ( Fig.8). The most plausible explanation for the observed results may be attributed to the particle nature of the matter (Benzalkonium chloride material) and radiations (sunlight). At the lower concentration range of the Benzalkonium chloride, there will be limited numbers of molecules of the Benzalkonium chloride to solubilize the limited number of dye molecules producing limited number of semi/leuco dye molecules. Subsequently, the limited number of semi/leuco dye molecules shall transfer limited numbers of electrons at the surface of working electrode (Pt electrode) leading to lower photo-current generation. The higher concentration of the Benzalkonium chloride may inhibit the movement of molecule of the dye Tropaeline-O towards the electrodes in the desired time limit. At the higher concentration range of the Benzalkonium chloride, there will be large numbers of the molecules of the Benzalkonium chloride which would hinder the sunlight photons to reach nearby area of the working electrode leading to the photo-excitation of limited numbers of the sensitizer molecules in the electrolyte adjacent to the working electrode. It is a published study that surfactants have solublizing effect on the dyes molecules. The dye is most solubilized by the surfactants over their (surfactant’s) critical micelle concentration. Therefore, the dye solubility is estimated to increase linearly with increase in the surfactant concentration. This trend for rising dye solubility is reported for surfactant’s moderate concentrations only. The dye solubility is not further favored by increasing the surfactant concentrations, once the micelles have grown to a certain size. The dye solubility is adversely affected at very high surfactant concentrations owing to the formation of rod-like micelles with high increase in the viscosity [28, 55]. According to the second law of thermodynamics, the reversibility increases the efficiency of the thermodynamic processes. In present study, the dye sensitizer is reduced to make reduction couple Dye/Dye - (i.e., Tropaeline-O/Tropaeline-O - dye). Therefore, any factor increasing the reversibility of this reduction couple will also increase the cell efficiency. It is reported in a cyclic voltammetric study that the BAC surfactant increases the reversibility of the reduction couple of Co (II) to Co(I) in the [Co(II)(bpy) 3 ] 2+ dye sensitizer [56]. On the basis of this reported fact, the authors assume that the BAC may also have similar effect of increasing the reversibility of the Tropaeline-O/Tropaeline-O - dye reduction couple in the present study enhancing the electrical output of the PG cell. Table 6. Effects of variation of the Benzalkonium chloride surfactant concentration Cell Parameters [Benizalkonium chloride]×10 -2 M # 6.00 6.63 7.00 7.50 8.00 V dark (mV) 414 389 417 683 472 V max (mV) 678 680 705 698 690 V oc (mV) 658 671 685 650 658 i max (mA) 10000 6500 10000 11000 9000 i eq or i sc (mA) 900 1500 1000 900 1200 V pp (mV) 18 122 186 181 39 P pp (mW) 14.4 122.0 55.8 108.6 31.2 i pp (mA) 800 1000 300 600 800 t (min.) 15 22 12 20 15 CE (%) 0.04 2.73 0.56 2.48 0.15 FF 0.02 0.18 0.08 0.18 0.03 # [Tropae line-O ]2.66 × 10 -5 M, [ Oxalic acid]2.97×10 -3 M, pH 12.98, Pt electrode size 0.5cm×0.5cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm), diffusion length (D L ) 4.0 cm, sunlight intensity 3.24 mWcm -2 3.2.4. Effects of variation of alkalinity concentration on the PG cells’ electrical performance The effect of the variation of the alkalinity on the PG cells’ electrical performance has been studied by fabricating in all five cells. For each cell, the value of used alkalinity concentration is different, but the value of other cell fabrication variables (other than alkalinity concentration) is same. The highest photo-current is noted at an optimal concentration (i.e., 2.0 M; pH 12.98) of alkalinity ( Table 7 ). The relation between alkalinity concentration and corresponding current is shown by a parabolic curve with maxima showing highest current at corresponding alkalinity concentration, i.e., optimized alkalinity concentration value, 2.0 M ( Fig.9). The PG cell system works effectively in strongly alkaline conditions. The most plausible explanation for the observed results may be attributed to the (i) particle nature of the matter/radiations, and (ii) effect of alkali on the solubility, electron donating and ionic nature of the dye molecules. At the lower concentration range of the alkalinity, there will be limited numbers of molecules of the alkali to solubilize the limited number of dye molecules producing limited number of semi/leuco dye molecules. Subsequently, the limited number of semi/leuco dye molecules shall transfer limited numbers of electrons at the surface of working electrode (Pt electrode) leading to lower photo-current generation. The higher concentration of the alkalinity may inhibit the movement of molecule of the dye Tropaeline-O towards the electrodes in the desired time limit. According to the concept of second law of thermodynamics, the reversibility of the photo-processes is a desired feature of cells for getting the higher solar energy conversion efficiency. Therefore, the reductant molecules involved in the electron exchanges with sensitizer molecules are desired to be part of reversible changes for higher electrical output of the cell. But, at high concentration of the alkali solution (i.e., very high pH), the OH - may combine chemically with the oxidized state of the oxalic acid reductant molecule, intercepting the regeneration of its (reductant) original state. The solubility of the anionic azo dye tropaeline-O is estimated to be low at lower pH range and high at high pH range. The solubilization of dyes is high in higher pH range (11-14) leading to the increased output of the PG cells as a result of increased diffusion and decreased aggregation of the dye molecules. The dye Tropaeline-O is acidic and anionic in nature. At low pH range, the anionic form is assumed to be disfavored due to increasing protonation of the sulfonic group and nitrogen atoms of the dye molecules. The electron transferring tendency of the dye molecules to the working Pt electrode is adversely affected as a result of the availability of the lower number of anionic dye molecules leading to the lower current generation in the cell. The increased anionic nature facilitates its own contribution to current also. Under the conditions of higher pH rang, the redox potential of dye molecules is more negative favoring electron transfer from dye molecule to Pt. Table 7. Effects of variation of alkalinity concentration on the PG cells electrical performance Cell Parameters pH (Alkalinity) # 11.80 12.40 12.98 13.10 13.50 V dark (mV) 407 394 389 430 470 V max (mV) 719 663 680 740 749 V oc (mV) 702 660 671 710 746 i max (mA) 6000 6000 6500 7000 10000 i eq or i sc (mA) 1000 1100 1500 600 800 V pp (mV) 19 101 122 101 39 P pp (mW) 10.0 70.7 122.0 20.2 23.4 i pp (mA) 1000 700 1000 200 600 t (min.) 15 15 22 10 22 CE (%) 0.08 0.84 2.73 0.11 0.11 FF 0.04 0.09 0.18 0.04 0.03 # [Tropaeline-O]2.66 × 10 -5 M, [Benzalkonium chloride]2.21×10 -2 M, [Oxalic acid] 9.9×10 -4 M, Pt electrode size 0.5cm×0.5cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm), diffusion length (D L ) 4.0 cm, sunlight intensity 3.24 mWcm -2 3.2.5. Summary result of the optimization of cell fabrication variables and corresponding optimized electrical performance of the cell For this photogalvanic chemical system, the optimum value of the cell’s electrical parameters is as: dark potential 389 mV, maximum potential (V max ) 680 mV, open-circuit potential (V oc ) 671 mV, maximum current (i max ) 6500 µA, short-circuit current (i sc ) 1000 µA, current at power point (i pp ) 1000 µA, potential at power point (V pp ) 122 mV, power at power point (P pp ) 122.0 µW, fill factor (FF) 0.18, conversion efficiency (CE) 2.73 %. The optimal cell performance has been obtained at following optimum cell fabrication parameters: [Tropaeline-O] 2.66 x 10 -5 M, [Benzalkonium chloride] 2.21 × 10 -2 M, pH 13.72, [Oxalic acid] 0.99 × 10 -3 M, Pt electrode size 0.5 cm × 0.5 cm, Pt electrode size 0.5 cm × 0.5 cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm) diffusion length (D L ) 4.0 cm, sunlight intensity 3.24 mWcm -2 , 20.90 o C room temperature, and pre-illuminated electrolyte solution temperature 21.0 o C. 4. Study of the variation and stability of open-circuit potential (V oc ) & short-circuit current (i sc ) over time during illumination of the cell The variation and stability of the open-circuit potential (V oc ) and short-circuit current (i sc ) over time has been studied after fully charging the cell and keeping illumination of the cell on. The value of V oc and i sc has been found quite steady and stable for over a very long time, i.e., potential ~809 mV to 803 mV over ~485 minutes and current ~1100 µA-900 µA over ~420 minutes and 700 mV over 1448 minutes ( Table 8, Table 9, Fig. 10) . The steady state of the potential and current may be attributed to the establishment of the quasi-equilibrium of the photo-electrochemical processes occurring in the bulk of electrolyte and on the interface between electrolyte and electrode. On the illumination of the electrolyte, the photo-processes are irreversible and fast in the beginning leading to the abrupt rise in the photo-potential. After some time, the reverse processes gains momentum to establish the quasi-equilibrium leading to the corresponding equilibrium and steady state value of the cell potential. The steady state value of the cell current (i sc ) may also be attributed to the same nature of the quasi-equilibrium state of the photo-electrochemical processes. The quite steady and stable value of V oc and i sc over a very long time is indicative of the photo-stability of the Tropaeline-O dye based PG cells. The methodology and the nature of the observations used in the present study for showing the photo-stability of the PG cells is also supported by the published work of Cheng et al . [57]. In published study, Cheng et al. has studied current and potential over long time to observe a stable values inferring stability of the ruthenium dye based DSSCs cell. Table 8. Study of the variation and stability of open-circuit potential (V oc ) over time during illumination of the cell Time (min.) # Open-circuit potential (mV)* Time (min.) # Open-circuit potential (mV)* 1 409 16 807 1 410 50 806 2 415 90 805 3 426 240 804 4 430 360 803 7 450 390 803 15 809 400 803 *negative value, # [Tropaeline-O]2.66 × 10 -5 M, [Benzalkonium chloride]2.21×10 -2 M, [Oxalic acid]9.9×10 -4 M, Pt electrode size 0.5cm×0.5cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm), diffusion length (D L ) 4.0 cm, sunlight intensity 3.24 mWcm -2 Table 9. Study of the variation and stability of short-circuit current (i sc ) over time during illumination of the cell Time (min.) # Short-circuit current (µA) Time (min.) # Short-circuit current (µA) 1 1100 180 950 2 1100 210 950 4 1000 300 900 15 1000 310 900 30 1000 360 900 60 1000 390 900 85 1000 420 900 135 1000 1448 700 # [Tropaeline-O]2.66 × 10 -5 M, [Benzalkonium chloride]2.21×10 -2 M, [Oxalic acid]9.9×10 -4 M, Pt electrode size 0.5cm×0.5cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm), diffusion length (D L ) 4.0 cm, sunlight intensity 3.24 mWcm -2 3.2.6. E lectrical performance of the PG cells in the forward direction (i & V change) and backward direction (V & i change) ( Hysteresis curve) In present study, the electrical performances of the PG cell in both the forward direction and backward direction have been observed as almost same and historically quite repetitive ( Table 10, Fig. 11). The forward direction curve and backward direction curve almost superimposes on each other giving almost negligible area of the hysteresis loop showing quite good stability of the photo-galvanic system. The hysteresis observations on the stability aspect of the photogalvanic system are in line with the observations on the stability of photogalvanic system supported by the study on the steady state and stability of the current and potential. The hysteresis phenomenon is basically linked with the magnetism. Hysteresis curve is drawn by plotting a curve between two magnetic variables. One curve is drawn for change in value of one variable with change in value of other variables in forward direction, and another curve is drawn for change in value of one variable with change in value of other variables in backward direction. Both forward direction curve and backward direction curve taken together constitute the hysteresis curve. The large area of the hysteresis curve signifies the greater loss in the energy, the low stability of the system, and the lower memory capability of the system to restore history. The hysteresis curve (J-V curve) is reported for DSSCs [58]. It is reported that the photovoltaic performance parameters (Voc, j sc ) obtained in the normal sweep are smaller than that in the reverse sweep [59]. Prompted by this published study, the authors have determined hysteresis curve for PG cell as well by (i) first, slowly increasing external load resistance (changing from minimum to highest possible) value to get various current values in decreasing order with corresponding potential values in forward sweep, and (ii) thereafter, slowly decreasing external load resistance (changing from highest to minimum possible) to get various current values in increasing order with corresponding potential values in the backward sweep. The observed hysteresis curve (i-v curves of both forward and backward sweeps taken together) is a loop of two overlapping linear curves. This observation of hysteresis curve in present study is indicative of almost no energy loss in backward sweep. The values of the current and potential of backward sweep are almost equal to that in normal forward sweep. This way, the observation of the PG cells in present study is quite different than the work reported on DSSCs. Table 10 . Study of the electrical performance of the PG cells on the forward direction potential and backward direction potential reaction (Hysteresis curve) Current (µA) # Forward direction potential (mV) Backward direction potential (mV) Current (µA) # Forward direction potential (mV) Backward direction potential (mV) 1000 36 35 400 227 225 900 39 37 300 232 231 800 42 40 200 362 360 700 125 126 100 388 388 600 149 150 0 401 404 500 222 221 - - - # [Tropaeline-O]2.66 × 10 -5 M, [Benzalkonium chloride]2.21×10 -2 M, [Oxalic acid]9.9×10 -4 M, Pt electrode size 0.5cm×0.5cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm), diffusion length (D L ) 4.0 cm, sunlight intensity 3.24 mWcm -2 3.2.7. Photo-absorption and photo-stability of the Tropaeline-O dye sensitizer in pure form and in electrolyte The photo-stability of the dye sensitizer molecules greatly affects the electrical output and the life of the cell. Here, the dye photo-stability means the chemical stability of the dye molecule in the presence of other chemical reagents (reductant, surfactant, alkali, acid, etc.) and sunlight. The every dye molecule has a characteristics chemical and chromophoric structure (skeletal structure with substituent including active functional groups). This peculiar chromophoric and chemical structure of the dye molecules enables it to show a characteristics absorption and electron donor/acceptor property. As long as the chemical structure remains intact, the absorption and electron donor/acceptor property of the dye molecules remains unchanged ensuring stable photo-galvanic property of the photo-galvanic cells. As the chemical structure of the dye changes by way of group change and/or fragmentation, the dye will not be available for its original light absorption and electron-donor properties leading to the instability in the photo-galvanic property (i.e., generated current, potential, power; life of the cell; etc.) [60]. The photo-absorption property of the Tropaeline-O dye sensitizer in pure form and in electrolyte is shown in Fig.12, Fig.13, and Fig.14. The Tropaeline-O dye sensitizer is the main fabrication component of the cell as it is the light absorbing material. The light absorption property is characterized by the position and intensity of the UV-Visible spectral band. Therefore, the pre-illuminated and post-illuminated spectrum of the pure Tropaeline-O dye sensitizer has been studied in the aqueous medium as well as in the electrolyte. The UV-Visible spectra has been taken with the help of Single Beam UV-Visible Spectrophotometer-108 (Systronics, Ahmedabad, Gujarat, India) and cuvette cells [manufactured by Optiglass Ltd., UK; properties as the transmissions 82.3 % (at 200 nm), 84.3 % (at 220 nm) and 85 % (at 85 nm), and width 10 mm]. The 2.66 × 10 -5 M Tropaeline-O dye sample solution spectra has been determined by taking singly distilled water solvent in the reference cuvette cell. The pure aqueous solution of Tropaeline-O dye at 2.66×10 -5 M has been observed to show absorbance from the 200 nm to 900 nm. The dye shows favorable absorption property both in the UV region (wavelength maxima 360 nm, absorbance 2.69; 260 nm with 0.45 absorbance) as well in the visible region (wavelength maxima 430 nm, absorbance 1.54, molar extinction coefficient 57894 Mol -1 L cm -1 ). The published value of the wavelength maxima of aqueous solution of Tropaeline-O dye in visible region is 430 nm [61]. Boiko et al. has also reported two peaks at 345 nm and 420 nm, with diverse absorbance value, specified for Tropaeline-O in aqueous medium [59]. Boiko et al. has explained this phenomenon on the basis of conjugation effect of electron clouds in the double bond of chromophore groups of Tropaeline-O molecule. Thus, the observed wavelength maximum (at 360 nm in UV range and at 430 nm in visible range) of aqueous Tropaeline-O dye solution in the present study is also validated by the published literature. The similarity of observed and published data shows that the sample of dye used is a Tropaeline-O sensitizer. The absorption property of the Tropaeline-O sensitizer make it a suitable light absorbing material as it absorb in the most convenient spectral region (visible) of the sunlight. The post-illuminated spectra of the aqueous Tropaeline-O dye solution almost resemble that of pre-illuminated spectra except the disappearance of the absorption maxima of UV region after illumination. The band at wavelength maxima in visible region remains almost intact (with slight hyperchromic shift) on illumination showing that this Tropaeline-O dye is a good material for harvesting the sunlight in the visible region specifically at 430 nm. A bare look at the Fig.3 shows almost overlapping between pre-illuminated spectral curve and post-illuminated spectral curve (spectra obtained after three hours long illumination of electrolyte) showing robust photo-stability of the Tropaeline-O dye sensitizer. The stability of the dye sensitizer is the backbone of stable photo-galvanic cells producing stable current and potential over long time. Therefore, the observation of steady state potential ( Table 3.11 ), steady state current ( Table 3.12 ), and hysteresis curve ( Table 3.13 ) may be attributed to the good photo-stability of the Tropaeline-O dye sensitizer in the present study. sensitizer, oxalic acid reductant, BAC surfancatnt, and alkali in aqueous medium.The photo-absorption property of the Tropaeline-O dye sensitizer in the electrolyte solution is influenced by the alkali, surfactant, and reductant. Therefore, the pre-illuminated and post-illuminated spectrum of the Tropaeline-O dye sensitizer in the electrolyte has been studied to explain the opto-electrochemical phenomenon of the photo-galvanic cells in the present study. The 2.66×10 -5 M Tropaeline-O dye electrolyte solution sample spectra have been determined by taking reference solution in the reference cuvette cell. The spectra of dye alkali solution has been determined by taking sample solution (0.133 ml of M/500 Tropaeline-O, 0.99 ml of M/100 Oxalic acid, 2.21 ml of M/10 Benzalkonium chloride, 5 ml of 4M NaOH, and 1.66 ml of singly distilled water; total 10 ml solution) in sample cuvette cell and reference solution (0.99 ml of M/10 Oxalic acid, 2.21 ml of M/10 Benzalkonium chloride, 5 ml of 4M NaOH, and 1.8 ml of singly distilled water; total 10 ml solution) in reference cuvette cell. The electrolyte solution (having Tropaeline-O dye at 2.66×10 -5 M) has been observed to show absorbance from the 200 nm to 900 nm. The dye in the electrolyte solution shows favorable absorption property both in the UV region (band at 240 nm with absorbance 1.07; wavelength maxima band at 270 nm with absorbance 1.86) as well in the visible region (band at 400 nm with1.51 absorbance; wavelength maxima band at 495 nm with absorbance 1.36 & molar extinction coefficient 51127 Mol -1 L cm -1 ). The published value of the wavelength maxima of Tropaeline-O dye in visible region is 488 nm-492 nm (pH 13, 0.1 M NaOH alkali) and ≥ 500 nm (at 1% in 0.1 M NaOH, 1 cm cuvette) [62]. Thus, the observed wavelength maximum (at 495 nm in visible range) of Tropaeline-O dye at pH 13.11 in the present study is also validated by the published literature. The similarity of observed and published data in alkali medium also shows that the sample of dye used is a Tropaeline-O sensitizer. The absorption property of the Tropaeline-O sensitizer in alkali electrolyte solution make it a suitable light absorbing material as it (as part of electrolyte) absorb in the most convenient spectral region (visible) of the sunlight. Further, the wavelength maxima of the pure aqueous dye solution at 430 nm are batho-chromically shifted to 495 nm in alkali electrolyte ( Fig.13 ). This bathochromic shift may be attributed to the effect of electrolyte on the chemical structure of the dye. Authors attribute it to the formation of di-phenoxide anion structure (in the phenol moiety of dye, see Scheme-I ) as a result of alkali induced proton removal from the -OH groups of dye. The oxy anionic structure (O - ) being negatively charged work as a very strong auxochrome group to facilitate pie to pie electron transition in dye molecule leading to the bathochromic shift. The post-illuminated spectra of the aqueous Tropaeline-O dye electrolyte solution almost resemble that of pre-illuminated spectra of electrolyte except the disappearance of the absorption peaks of UV region after illumination. The band at wavelength maxima in visible region remains almost intact (with slight hypochromic shift) on illumination showing that this Tropaeline-O dye electrolyte is a good material for harvesting the sunlight in the visible region specifically at 495 nm. A bare look at the Fig.13 & Fig.14 shows almost no change in absorbance near 495 nm between pre-illuminated spectral curve and post-illuminated spectral curve (spectra obtained after three hours long illumination of electrolyte) showing robust photo-stability of the Tropaeline-O dye sensitizer with respect to its most favorable absorption wavelength. The stability of the dye sensitizer is the backbone of stable photo-galvanic cells producing stable current and potential over long time, and same also has been observed in alkali electrolyte. Therefore, the observation of steady state potential ( Table 11 ), steady state current ( Table 12 ), and hysteresis curve ( Table 13 ) produced by dye in electrolyte may be attributed to the good photo-stability of the Tropaeline-O dye sensitizer in the electrolyte also in the present study. It is pertinent to mention a reported study that the absorption peak at 430 nm gradually decreases and finally disappears; indicating photo-degradation (Fe-doped ZnO catalyzed 99.8. %) of the Tropaeline-O dye with time during three hours long illumination [61]. In present study, it is encouraging to note that there is no photo-degradation of dye during three hours long illumination. But, the authors estimate that the photo-degradation of the Tropaeline-O dye is imminent after very long time. Therefore, the knowledge of the likely photo-products is of utmost importance for long term use of the photo-galvanic cells based on the Tropaeline-O dye sensitizer. It is reported that the azo linkage is the most labile portion of an azo dye (Scheme-V) [42]. The linkage easily undergoes enzymatic breakdown, but thermal or photochemical breakdown may also take place. Degradation of azo dyes can be obtained by reduction or by oxidation. The reduction releases the colorless component amines [42]. In present study, the dye undergoes reduction giving inference of reductive cleavage. Thus, in present study, the likely photo-degradation products (phenolic fragment and sulfonic fragment) of the Tropaeline-O dye can be estimated as below (Scheme-VI)- The bands at 260 nm, 360 nm, and 430 nm in the UV-Visible spectra of pure aqueous dye (Tropaeline-O) may be attributed to its azo moeity, phenolic benzenoid moeity, and sulfonic benzenoid moiety, respectively ( Fig.3.12 ). The low energy transition band at 430 nm is facilitated by electron push-pull effect of the para substituted groups (electron withdrawing sulfonic group and electron donating azo group). Upon irradiation, the disappearance of band at 260 nm may be attributed to the photo-cleavage of azo linkage. Upon decay of dye, the p-C 6 H 4 (NH 2 )(SO 2 ONa) and m,p-dihydroxyaniline is formed, where the electron donating tendency of the NH 2 group is higher than that of the azo linkage. Therefore, in the p-C 6 H 4 (NH 2 )(SO 2 ONa) fragment, the push-pull effect is greater now to give relatively enhanced absorbance at 430 nm in post-illuminated spectra. Similarly, in the m,p-dihydroxyaniline fragment, the more powerful electron donating group NH 2 (having more electron donating tendecy than azo) also may be the reason for enhanced absorbance at 360 nm in the post-illumination spectra. The existence of the aromatic, photo-stable, and robust benzene chromophore moiety may be the reasons for the stability of the dye. Further, it is also pertinent to mention here that the degradation is not limited to the dye, but other chemicals as the BAC surfactant may also undergo degradation. It is reported that PS/Fe 2+ catalyzed BAC oxidative-degradation process produces intermediates (like benzene derivative fragments and hydro carbon fragments) and finally minerals like CO 2 , NH 3 , H 2 O, and Cl -1 [50] and authors also estimate same nature of photo-degradation products in present study. On the basis of the reported study on the degradation of the Tropaeline-O dye and BAC surfactant, it is certain that the present photogalvanic cells based on these chemicals (Tropaeline-O dye and BAC surfactant) are likely to see degradation. Therefore, it has to be seen that whether such cell having degraded chemicals would be able to supply energy in long term and also in conditions of no-sunlight during night hours and during cloudy hours in day time. On this aspect, authors have already given data on the power storage capacity of Tropaeline-O dye and BAC surfactant based cell providing power supply in the absence of the illumination ( Table 3 ). Further, the stability aspect is also shown in terms of stability of current and potential over long time for these Tropaeline-O dye and BAC surfactant based cells ( Table 11-13 ). Further, improvement in the Tropaeline-O dye and BAC surfactant based cells is also suggested by authors on the basis of the work reported by Rangel et al. [63]. It has been reported by Rangel et al. that a very fast light-to-dark or dark-to-light illuminating conditions can be changed for charging of the all solar cells. The abrupt changes in the illuminating conditions causes shifting in the cell process far away from equilibrium position of the photo-processes. This special type of illuminating the cell brings in a continuous redox reaction. It is reported that this continuous redox reaction not depends on the cell illumination (illumination is a main factor influencing the cell efficiency). Rangel et al. has reported that this continuous redox reaction in turn causes an electrochemical effect leading to the average current value and the oscillations observed under the dark conditions. The non-linear oscillations in the current signal are reported on a rapid transition from darkness to illumination conditions. Rangel et al. has reported that two mechanisms (photovoltaic and chemical) operate simultaneously in the cell. The generated current and potential by the dark chemical mechanism is less than that produced by the photovoltaic mechanism. But, the beauty of this dark chemical mechanism is that it is capable of producing some current/potential (although low in value) even after dye degradation [63]. Thus, with this discussions, the authors suggests future researchers to use the Rangel et al. reported concepts to enable the Tropaeline-O dye and BAC surfactant based cells usable in dark as well with durable utility. Scientists Shigehara et al. and Kamat et al. have reported the efficacy of the different electrodes as Pt-Pt, and SnO 2 -Pt [64, 65]. Therefore, the same (Pt-Pt, SnO 2 -Pt) may also be used for further improvement in the Tropaeline-O dye and BAC surfactant based photogalvanics. But, the high cost of the Pt-Pt is again a disadvantage paving way for the low cost electrodes like intercalation type electrode materials (graphite, graphene, carban nanostructure) and alloys, etc . [65]. The electric polarization of graphite is an obstacle for having more efficient anodic electrode [66]. The intercalation type electrode material lacks (i) the high energy density, (ii) the high theoretical specific capacity, and (iii) the diversity of materials available for use as cathodic for aqueous batteries [67]. Anodes as platinized titanium (Ti/Pt), less costly but behaving electrochemically same way as the platinum have been reported by Cotton et al. [68]. The present study also involves the aqueous medium based electrolyte. For the variety of aqueous batteries, the metal anodes (including alkali metals like Li and Na; and multivalent metals like Zn, Mg, Al, etc.) has been investigated successfully providing high energy density, (ii) the high theoretical specific capacity, and (iii) the diversity of materials available for use as cathode for aqueous batteries [67]. The drawback of the metallic electrodes is their reduced lifetime owing to sacrificial nature which depends on their shape, dimensions, and the current extracted. Thus, the protection of the sacrificial electrodes can be realized by having suitable shape and size, polarized drainage or amplified electric drainage technology [69] , and stabilization perspective of the metal anodes for aqueous batteries [67]. Given this reported fact, the future researchers may also focus on the use of the alkali metals and multivalent metals (having suitable shape and size, and polarized drainage or amplified electric drainage technology for their protection), and platinized titanium as anode materials for improving the present Tropaeline-O dye sensitizer and BAC based photogalvanics. One more important point regarding the illumination of the solar cells is that it sees a temperature rise. As far as the effect of temperature rise as a result of photo-illumination of the Tropaeline-O dye sensitizer based PG solar cells is concerned, it proves blessings in disguise. The temperature rise of about 10 o C (i.e., 29.8 o C-39.9 o C) is observed for the Tropaeline-O sensitizer based cell. This temperature rise facilitates higher thermal agitation, higher diffusion, higher solubility, and higher enthalpy leading to the favorable conditions for the higher value of cell current. The rise in the temperature increases the kinetic energy of the Tropaeolin-O molecule leading to its higher diffusion rate and the higher collision resulting increased photocatalytic solar energy conversion. Although, the very high temperature rise (˃ 40 o C) adversely affects the cell efficiency, but in the case of present photogalvanics, the maximum temperature of the electrolyte achievable is less than the 40 o C [70, 71]. 3.2.8. Comparison of results of the Tropaelinee-O dye sensitizer with similar studies Conventionally, the H-shaped glass tubes have been used to fabricate the PG cell. But, the recent study reported by Koli et al. on Congo Red dye sensitizer (M.W. 696.66, a diazo dye with –SO 2 O - Na + and –NH 2 groups) has shown that the use of simple cylindrical glass vessels is not only cheap but also more efficacious in power generation [72]. In present study, the Scholar have also used Pt electrode size 0.5 cm × 0.5 cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm) diffusion length (D L ) 4.0 cm, vessel for fabrication of the cell based on Tropaeline-O dye sensitizer (MW 316.27, azo dye with –SO 2 O - Na + and –OH groups), and have observed enhanced electrical output consistent with the reported study. However, the power output (power 122.0 μW, current 1000 μA) of present study is relatively good than that of the study reported (power 439 μW, current 2100 μA) [72]. The nature of the dye sensitizer is the main constituent influencing the electrical output of the PG cell. In present study, as observed in ( Table 8, Table 9, Fig. 10) the greater photo-stability of the Tropaeline-O dye sensitizer may be one of the reasons for good power (power 122.0 μW & current 1000 μA of present study) vis-à-vis the power reported (power 439 μW, current 2100 μA) [72]. The anionic nature of the sensitizer molecule also favors the electron exchange to working electrode (from the sensitizer molecule). The used Tropaeline-O dye sensitizer molecule in the present study has lower MW 316.27 and higher ionic nature (–SO 2 O - and –O - in alkali medium) than that for the Congo-red molecule (MW 696.66; –SO 2 O - in alkali medium), and this factor may also be the reason for the relatively higher electrical output in the current study. The efficient performance of the photogalvanic cells relies on in solution selective electrodes and dye solubility, with fast electron transfer thermodynamic and kinetics process. A new PG cell configuration based on the H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm) and low MW TPO dye has been exploited to favors the fast dye diffusion and consequently the thermodynamic and kinetic processes. Table.11 . Comparison of results of the H-shape vessel with higher volume of electrolyte and small volume of electrolyte S.N. Electrical parameters of the cells For H-vessel with higher volume of electrolyte # For H-vessel & small volume of electrolyte @ 1. i max 2700 µA 6500 µA 2. i sc 1600 µA 1000 µA 3. P pp 265.0µW 122.0 µW 4. CE 2.70 % 2.73% 5 FF 0.16 0.18 # Comparison of results of the H-vessel vessel with higher volume (62 ml) of electrolyte (for detail sees Ref. 57, table 2) and @ the H-vessel vessel with small volume (30 ml) of electrolyte . # [Congo red dye-photosensitizer]10.3×10 -5 M+[formaldehyde-reductant]1.76×10 -3 M+[SLS surfactant]1.32×10 -2 M, Pt(0.5cm×0.3cmelectrode, saturated calomel electrode (SCE). @) # [Tropaeline-O]2.66 × 10 -5 M, [Benzalkonium chloride]2.21×10 -2 M, [Oxalic acid]9.9×10 -4 M, Pt electrode size 0.5cm×0.5cm,graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm), diffusion length (D L ) 4.0 cm, sunlight intensity 3.24 mWcm -2 3.2.9. Peculiarity, electrical suitability, and future prospects of the graphite as counter electrode in PG cell The Pt is working as the anodic electrode terminal, and the graphite electrode is working as the cathodic electrode terminal (when Pt & graphite forms the two terminals of the cell) in the present study. The role of Pt as anode and Graphite as cathode may be attributed to the electronic configurations, stability of the naturally occurring electronic states, and the stability of the half filled and fully filled orbital The Pt is working as the anodic electrode terminal, and the graphite electrode is working as the cathodic electrode terminal (when Pt & graphite forms the two terminals of the cell) in the present study. The role of Pt as anode and Graphite as cathode may be attributed to the electronic configurations, stability of the naturally occurring electronic states, and the stability of the half filled and fully filled orbital. The electronic configuration of the Pt (A.N.78) is [Xe] 54 , 4f 14 , 5d 9 ,6s 1 , and this is the naturally occurring electronic state, i.e., natural Pt atom. It means, the Pt will tend to be in this natural neutral stable electronic state. The Pt is a very popular inert electrode, and this is enabled by its peculiar electronic configuration. In photogalvanic cells, the excited dye sensitizer molecule with excess electron sheds its electron to the Pt. It is because by taking the one electron from the dye, the Pt atom will have the stable fully and half filled orbital, i.e., 5d 10 , 6s 1 . But this state (having one excess electron) with 5d 10 & 6s 1 is not the most stable naturally occurring state of the Pt. Therefore, the Pt sheds excess electron to the external circuit leading to the flow of the current towards Pt terminal. Therefore, this peculiar electronic state makes the Pt as a good inert electrode providing the good electrical contact between electrolyte and the external circuit by causing good exchange of the electrons from the electrolyte to Pt to external circuit. The electronic configuration of the carbon (A.N. 6) is the 1s 2 , 2s 2 , 2p x 1 , 2p y 1 , 2p z 0 , and this is the naturally occurring electronic state, i.e., neutral carbon atom. It means, the carbon will tend to be in this natural neutral stable electronic state. The carbon is a very popular inert electrode, and this is enabled by its peculiar electronic configuration. On getting one electron from the external source, the carbon atom will have the stable fully and half filled orbital, i.e., 1s 2 , 2s 2 , 2p 3 . But this state (one negative charged) with 2p 3 is not the most stable naturally occurring state of the carbon. Therefore, the carbon sheds excess electron to the electrolyte (to dye). This way, the carbon acts as a good inert electron exchanger between external circuit and the electrolyte by taking electron from the circuit and giving this electron to the electrolyte. Further, there is also a one more aspect to be considered, and this is that the Pt is a metal, and the carbon is a non-metal. The metals basically have the property of giving the electrons. In view of this, it is justified that the Pt will give electrons to the external circuit and will behave as an anodic terminal, and the graphite will receive the electrons from the external circuit to act as a cathodic terminal. The absorbed photon energy is converted in to the electricity in the photogalvanic cell. The photogalvanic cells do not involves any chemical reaction in the electrolyte and on the surface of the electrodes for the photo-generation of the current. The electron movement from the reductant to excited dye to Pt to external circuit to graphite to dye to reductant takes place leading to the photo-generation of the current in photogalvanic cell. The electrodes are only for the electrical contact of electrolyte for completing the circuit. Therefore, the electrodes which are inert and have good electron exchange capacity shall be more suitable for the fabrication of the photogalvanic cell. In present case, the graphite electrode has all the property like inertness and good electron exchanger. As far as the SCE electrode is concerned, as used in the previously reported studies [2, 15-30] it is a reference electrode involving the chemical reaction [Hg 2 Cl 2 (s) + 2 e - = 2 Hg (liq.) + 2 Cl - (aq.)], and this reaction is not consistent with the only electron exchange requirement of the photogalvanic cells. Therefore, the graphite offers itself as a good counter electrode with the added advantages like (i) it is very cheap, and available at through away prices from the discarded dry cells, (ii) it is robust in making so can be handled without any fear of breaking, making it for durable use. The combination electrode/SCE is very costly and very delicate, so its handling is prone with fear of breaking making it unsuitable for the durable use. The Graphite counter electrode’s efficacy is also reported for the DSSCs with ~ 5.01 % efficiency. The electrochemical activity of this graphite counter electrode is further enhanced by using the SnO 2 modified graphite electrode, i.e., the optimized graphite/SnO 2 composite [42]. The transition metal modified graphite electrodes (i.e., carbides, Tungsten carbide) have also shown good efficiency in the DSSCs cells [43, 44] High conductivity and activity are highly desirable for the counter electrode. It is reported that the low cost and chemical converted graphene has high electrical conductivity (derived from the pristine grapheme) and good reduction activity for redox species (inherited from defects) making it a promising counter electrode for the dye sensitized solar cells [45]. Good efficiency is also reported by Jayaweera et al. for the DSSCs employing a graphite counter electrode made of an optimized graphite layer thickness of 250 μm [46]. At this thickness, the graphite catalytic activity is optimum showing optimum electrical output. Jayaweera et al. has reported that the amount of graphite in thin layer is insufficient to provide the required catalytic activity for the efficient reduction of electrolyte. On the contrary, the graphite resistance is higher for thick layers decreasing the current [46]. The role of various structures (graphite nanofibre-GNF, graphite nanosheet-GNS, graphite nanoball-GNB) of the graphite counter electrode is extensively reported for dye sensitized solar cells. Among these structures, the GNB is reported as the most effective counter electrode [47]. The DSSCs proven technology of the optimized layered graphite, SnO 2 composite counter electrode, metal carbides,GNB, and chemical converted grapheme is suggested for further improvement of the graphite counter electrode based photogalvanic cells. Therefore, the use of graphite/modified graphite is not only cheaper, safe, easy to fabricate, more productive in terms of the power output but also more eco-friendly. On this basis, we justify utility of the graphite over the SCE, and also suggest its use in PG in future research. The observations of the present research are also verified by publication in the ‘Journal of Electroanalytical Chemistry’. In this journal (where the scholar is a author), the reported facts are as follows- “The observed electrical output for the very cheap, robust, and durable graphite counter electrode-based cells was found better than that for the very costly, delicate, and short-lived combination electrode. The observed electrical output for the rectangular graphite counter electrode vs Pt anodic electrode was fund better than that for the cylindrical graphite counter electrode vs Pt anodic electrode. The observed electrical output for the very cheap, easily available and simple non-blackened glass boiling tube-based cells was found better than that for the costly, not-readily available, and sophisticated H-shaped glass tubebased cells. For H-shaped glass tube-based cells; power 908 μW, 750 μW, and 718 μW was observed for rectangular graphite, cylindrical graphite, and SCE component of combination electrode, respectively. Similarly, for simple non-blackened glass boiling tube based cells; power 1170 μW, 1080 μW, and 804 μW was observed for rectangular graphite cell, cylindrical graphite cell, and SCE component of combination electrode, respectively. It was observed that the use of cheap graphite and readily available boiling tubes provides an opportunity for simplified fabrication of economically more efficient cells with greatly enhanced electrical output for future studies” [73, 74]. 4. Conclusion The Tropaeline-O dye-Oxalic acid reductant-benzalkonium chloride based photogalvanic chemical system has been studied in the present work. H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm) diffusion length (D L ) 4.0 cm, very small Pt working electrode (0.5 cm × 0.5 cm), and graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm)as counter electrode have been exploited for solar energy conversion. The observed electrical output is as follows-current 1000 μA , power 122.0 μW, and 2.73 %. The variation and stability of the V oc and i sc over time has been studied after fully charging the cell and keeping illumination of the cell on. The value of V oc and i sc has been found quite steady and stable for graphite counter electrode over a very long time, i.e., V oc ~809 mVto 803 mVover ~385 minutes and current~ 1100 µA-900µA over ~420 minutes. The electrical performances of the Photogalvanic cells in both the forward direction and backward direction in hysteresis curve have been observed as almost same and historically quite repetitive showing the stability of TPO and graphite based PG cell. The spectral, long term current and potential, and hysteresis studies have shown quite good photo-stability of the Tropaeline-O dye sensitizer as the light absorbing material. In view of the results obtained in the present study, it may be concluded that the graphite counter electrode with the tropaeline-O, benzalkonium chloride, and oxalic acid system provides a good option for fabricating a durable PG cells for harvesting solar power with storage efficiently. For future, the modified graphite electrodes may be exploited for further improvement in the PG cells. Declarations Acknowledgements: The authors thank the Department of Chemistry, Jai Narain Vyas University, Jodhpur, Rajasthan (India) for providing the necessary laboratory facilities Conflict of interest: The authors declare no conflict of interest. Data availability statement: All the experimental data has already been incorporated in the manuscript & SI file. Funding Statement: There is no research funding for the research of this manuscript. 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Dynamics of the electric polarization and depolarization of graphite. Carbon. 172,83-95(2021). [67]. H. Wang, R. Tan, Z. Yang, Y. Feng, X. Duan, J. Ma. Stabilization Perspective on Metal Anodes for Aqueous Batteries. Advanced Energy Materials , 11(2),2000962 (2021). J. B. Cotton, E. C. Williams, A. H. Barber, British Patent. 877, 901, 1958. [69]. R. Juchniewicz, J. Jankowski, K. Darowicki, Cathodic and Anodic Protection . Materials Science and Technology. (2013). S.R. Raga, F.F.-Santiago. Temperature effects in dye-sensitized solar cells. Physical Chemistry Chemical Physics .15,2328-2336(2013) [71]. P. Koli. Sudan-I dye and Fructose chemicals based photogalvanic cells for electrochemical solar energy conversion and storage at low and artificial sun Intensity. Arabian Journal of Chemistry. 14,1878-5352 (2021). P. Koli, Y. Dayma, R. K Pareek, R. Kumar, M. Jonwal. Simplified photogalvanic cell design with promise for the enhanced solar electricity generation and storage. Energy Storage, e 287 (2021), DOI: 10.1002/est2.287. P. Koli, Y. Dayma, R. K. Pareek, Rajendra Kumar, M. Jonwal. Modified and simplified photogalvanic cells: Solar energy harvesting using bromo cresol green dye with different electrodes and cell dimensions. Journal of ElectroanalyticalChemistry .904 (2022) 115942. M Jonwal, P Koli, R Kumar. Natural surfactant fenugreek (Trigonella foenum-graecum) seeds based photogalvanic cell for solar energy conversion and storage. Results in Chemistry . 15, (2025)102220. Schemes Schemes I-VI are available in the Supplementary Files section. Additional Declarations No competing interests reported. Supplementary Files Schemes.docx Scheme: Scheme-I: Chemical structure of Tropaeline-O dye. (Scheme II): Tropaeline-O powder and its aqueous solution Scheme-III: Chemical structure of Benzalkonium chloride surfactant. Scheme-IV: Chemical structure of Oxalic acid reductant. Scheme-V: Reduction of azo dye Scheme-VI: Reduction of Tropaeline-O dye Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7502096","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":511471976,"identity":"0f8206df-b00e-423f-a949-93539cf0a1c1","order_by":0,"name":"RAJENDRA KUMAR","email":"data:image/png;base64,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","orcid":"","institution":"Jai Narain Vyas University","correspondingAuthor":true,"prefix":"","firstName":"RAJENDRA","middleName":"","lastName":"KUMAR","suffix":""},{"id":511471977,"identity":"00895978-7915-4dbf-a2de-aba72ec04eb5","order_by":1,"name":"Dr. POORAN KOLI","email":"","orcid":"","institution":"Jai Narain Vyas University","correspondingAuthor":false,"prefix":"Dr.","firstName":"POORAN","middleName":"","lastName":"KOLI","suffix":""}],"badges":[],"createdAt":"2025-08-31 17:23:08","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7502096/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7502096/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":90851003,"identity":"1c7cd3f3-742b-43c6-8f8e-473cafd0d4aa","added_by":"auto","created_at":"2025-09-09 03:08:39","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":74245,"visible":true,"origin":"","legend":"\u003cp\u003eA schematic of the experimental set-up for harvesting the solar energy using the photogalvanic cell.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7502096/v1/4eb8d24e0f1cc5f19d8b720f.png"},{"id":90851668,"identity":"fd7d7dc3-6e85-427a-8be8-3c9b222f84cd","added_by":"auto","created_at":"2025-09-09 03:24:39","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":26366,"visible":true,"origin":"","legend":"\u003cp\u003eChange of the cell potential with time during illumination of the cell for its \u003csup\u003e\u003cem\u003e#\u003c/em\u003e\u003c/sup\u003e\u003cem\u003e[Tropaeline-O]2.66×10\u003c/em\u003e\u003csup\u003e\u003cem\u003e-5\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eM, [Benzalkonium chloride]2.21×10\u003c/em\u003e\u003csup\u003e\u003cem\u003e-2\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eM, [Oxalic acid]9.9×10\u003c/em\u003e\u003csup\u003e\u003cem\u003e-4\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eM, pH 12.98,Pt electrode size 0.5cm×0.5cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5cm, length 13.0 cm and bridge length 3.5 cm) diffusion length (D\u003c/em\u003e\u003csub\u003e\u003cem\u003eL\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e) 4.0cm, sunlight intensity 3.24 mWcm\u003c/em\u003e\u003csup\u003e\u003cem\u003e-2\u003c/em\u003e\u003c/sup\u003e\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7502096/v1/581910293cda2efefb6c9833.png"},{"id":90850476,"identity":"3333810a-59c4-4c79-9d8c-40c1fef0bdcf","added_by":"auto","created_at":"2025-09-09 03:00:39","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":37140,"visible":true,"origin":"","legend":"\u003cp\u003eThe change of the potential and power with the current of PG cell system \u003csup\u003e\u003cem\u003e#\u003c/em\u003e\u003c/sup\u003e\u003cem\u003e[Tropaeline-O]2.66×10\u003c/em\u003e\u003csup\u003e\u003cem\u003e-5\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eM, [Benzalkonium chloride]2.21×10\u003c/em\u003e\u003csup\u003e\u003cem\u003e-2\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eM, [Oxalic acid]9.9×10\u003c/em\u003e\u003csup\u003e\u003cem\u003e-4\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eM, pH 12.98,\u0026nbsp; Pt electrode size 0.5cm×0.5 cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm) diffusion length (D\u003c/em\u003e\u003csub\u003e\u003cem\u003eL\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e) 4.0 cm, sunlight intensity 3.24 mWcm\u003c/em\u003e\u003csup\u003e\u003cem\u003e-2\u003c/em\u003e\u003c/sup\u003e\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7502096/v1/83e15e855dca870d7f70cc3d.png"},{"id":90851206,"identity":"f30bbeae-3230-4405-beeb-8ed4862773dd","added_by":"auto","created_at":"2025-09-09 03:16:39","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":72956,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic of the most plausible mechanism for the photo-generation of the current using TPO dye sensitizer photogalvanic system\u003cstrong\u003e; \u003c/strong\u003e\u003cem\u003eWhere, the OA, OA\u003c/em\u003e\u003csup\u003e\u003cem\u003e+\u003c/em\u003e\u003c/sup\u003e\u003cem\u003e, TPO*, TPOˉ, hѵ, eˉ, Pt, and \u003c/em\u003egraphite\u003cem\u003e is oxalic acid reductant molecule, oxidized oxalic acid reductant molecule, excited state of the Tropaeline-O dye photosensitizer molecule, semi or leuco form of the Tropaeline-O dye photosensitizer molecule,\u003c/em\u003e \u003cem\u003ephoton, electron, working electrode, and counter electrode, respectively.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-7502096/v1/82e3adc94ba1d16a68a8aa28.png"},{"id":90851204,"identity":"a8933b48-2e84-408e-9530-be24a6789ff4","added_by":"auto","created_at":"2025-09-09 03:16:39","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":42123,"visible":true,"origin":"","legend":"\u003cp\u003eStorage capacity of the cell\u003csup\u003e\u003cem\u003e#\u003c/em\u003e\u003c/sup\u003e\u003cem\u003e[Tropaeline-O]2.66×10\u003c/em\u003e\u003csup\u003e\u003cem\u003e-5\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eM, [Benzalkonium chloride]2.21×10\u003c/em\u003e\u003csup\u003e\u003cem\u003e-2\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eM, [Oxalic acid]9.9×10\u003c/em\u003e\u003csup\u003e\u003cem\u003e-4\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eM, pH 12.98, Pt electrode size 0.5cm×0.5 cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm) diffusion length (D\u003c/em\u003e\u003csub\u003e\u003cem\u003eL\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e) 4.0 cm, sunlight intensity 3.24 mWcm\u003c/em\u003e\u003csup\u003e\u003cem\u003e-2\u003c/em\u003e\u003c/sup\u003e\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-7502096/v1/19c0eb546b24d3e128f68edb.png"},{"id":90851006,"identity":"46c5a04d-c7d9-43a6-806b-dbf4f684e8fd","added_by":"auto","created_at":"2025-09-09 03:08:39","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":36725,"visible":true,"origin":"","legend":"\u003cp\u003eVariation of the power and photocurrent with the concentration of Tropaeline-O dye sensitizer\u003csup\u003e\u003cstrong\u003e#\u003c/strong\u003e\u003c/sup\u003e;\u003cem\u003e(a)concentration of dye Tropaeline-O vs current (parabolic shaped curve),(b)concentration of dye Tropaeline-O vs power (parabolic shaped curve\u003c/em\u003e\u003csup\u003e\u003cem\u003e#\u003c/em\u003e\u003c/sup\u003e\u003cem\u003e[Benzalkonium chloride]2.21×10\u003c/em\u003e\u003csup\u003e\u003cem\u003e-2\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eM, [Oxalic acid]9.9×10\u003c/em\u003e\u003csup\u003e\u003cem\u003e-4\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eM, pH 12.98, Pt electrode size 0.5cm×0.5cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm), diffusion length (D\u003c/em\u003e\u003csub\u003e\u003cem\u003eL\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e) 4.0 cm, sunlight intensity 3.24 mWcm\u003c/em\u003e\u003csup\u003e\u003cem\u003e-2\u003c/em\u003e\u003c/sup\u003e\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-7502096/v1/3101d45a12a3e9691f2f31eb.png"},{"id":90851007,"identity":"96334dc6-45b3-48af-b5df-16bb1b65dbbb","added_by":"auto","created_at":"2025-09-09 03:08:39","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":36395,"visible":true,"origin":"","legend":"\u003cp\u003eVariation of the power and photocurrent with the concentration of Oxalic acid reductant\u003csup\u003e\u003cstrong\u003e#\u003c/strong\u003e\u003c/sup\u003e;\u003cem\u003e(a) concentration of reductant Oxalic acid vs current (parabolic shaped curve),(b) concentration of reductant Oxalic acid vs power (parabolic shaped curve;\u003c/em\u003e\u003csup\u003e\u003cem\u003e#\u003c/em\u003e\u003c/sup\u003e\u003cem\u003e[Tropaeline-O]2.66×10\u003c/em\u003e\u003csup\u003e\u003cem\u003e-5\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eM, [Benzalkonium chloride]2.21×10\u003c/em\u003e\u003csup\u003e\u003cem\u003e-2\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eM,, pH 12.98, Pt electrode size 0.5cm×0.5cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm), diffusion length (D\u003c/em\u003e\u003csub\u003e\u003cem\u003eL\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e) 4.0 cm, sunlight intensity 3.24 mWcm\u003c/em\u003e\u003csup\u003e\u003cem\u003e-2\u003c/em\u003e\u003c/sup\u003e\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-7502096/v1/4a1f5ec05bd53e9860990a83.png"},{"id":90851209,"identity":"e72cea75-9226-4e07-ae58-d1a0d88a7e06","added_by":"auto","created_at":"2025-09-09 03:16:39","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":39191,"visible":true,"origin":"","legend":"\u003cp\u003eVariation of the power and photocurrent with the concentration of Benzalkonium chloride surfactant\u003csup\u003e#\u003c/sup\u003e;\u003cem\u003e(a)concentration of surfactant Benzalkonium chloride vs current (parabolic shaped curve),(b) concentration of surfactant Benzalkonium chloride vs power (parabolic shaped curve).\u003c/em\u003e\u003csup\u003e\u003cem\u003e#\u003c/em\u003e\u003c/sup\u003e\u003cem\u003e[Tropaeline-O]2.66×10\u003c/em\u003e\u003csup\u003e\u003cem\u003e-5\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eM, [Oxalic acid]2.97×10\u003c/em\u003e\u003csup\u003e\u003cem\u003e-3\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eM, pH 12.98, \u0026nbsp;Pt electrode size 0.5 cm ×0.5cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm), diffusion length (D\u003c/em\u003e\u003csub\u003e\u003cem\u003eL\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e) 4.0 cm, sunlight intensity 3.24 mWcm\u003c/em\u003e\u003csup\u003e\u003cem\u003e-2\u003c/em\u003e\u003c/sup\u003e\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-7502096/v1/ddece14443ae5dd80bca4292.png"},{"id":90850482,"identity":"71e820e4-a14f-40fa-aaee-81beaf66c451","added_by":"auto","created_at":"2025-09-09 03:00:39","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":37717,"visible":true,"origin":"","legend":"\u003cp\u003eVariation of the power and photocurrent with the concentration of alkali (pH)\u003csup\u003e#\u003c/sup\u003e\u003cem\u003e(a) concentration of alkali (pH) vs current (parabolic shaped curve),(b) concentration of alkali (pH) vs power (parabolic shaped curve). \u003c/em\u003e\u003csup\u003e\u003cem\u003e#\u003c/em\u003e\u003c/sup\u003e\u003cem\u003e[Tropaeline-O] 2.66 × 10\u003c/em\u003e\u003csup\u003e\u003cem\u003e-5\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eM, [Benzalkonium chloride]2.21×10\u003c/em\u003e\u003csup\u003e\u003cem\u003e-2\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eM, [Oxalic acid]9.9×10\u003c/em\u003e\u003csup\u003e\u003cem\u003e-4\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eM, Pt electrode size 0.5cm×0.5cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm), diffusion length (D\u003c/em\u003e\u003csub\u003e\u003cem\u003eL\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e) 4.0 cm, sunlight intensity 3.24 mWcm\u003c/em\u003e\u003csup\u003e\u003cem\u003e-2\u003c/em\u003e\u003c/sup\u003e\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-7502096/v1/62d389e518dd80afea9b6472.png"},{"id":90851012,"identity":"9f1ea787-1d43-4d75-ba20-b55e7acac6cf","added_by":"auto","created_at":"2025-09-09 03:08:39","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":27370,"visible":true,"origin":"","legend":"\u003cp\u003eStudy of the variation and stability of V\u003csub\u003eoc\u003c/sub\u003e \u0026amp; i\u003csub\u003esc \u003c/sub\u003eover time during illumination of the cell\u003csup\u003e#\u003c/sup\u003e;(a) stability of open-circuit potential (V\u003csub\u003eoc\u003c/sub\u003e) vs time,\u003cem\u003e \u003c/em\u003e(b) short-circuit current (i\u003csub\u003esc\u003c/sub\u003e) vs time.\u003csup\u003e\u003cem\u003e#\u003c/em\u003e\u003c/sup\u003e\u003cem\u003e[Tropaeline-O]2.66×10\u003c/em\u003e\u003csup\u003e\u003cem\u003e-5\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eM, [Benzalkonium chloride]2.21×10\u003c/em\u003e\u003csup\u003e\u003cem\u003e-2\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eM, [Oxalic acid]9.9×10\u003c/em\u003e\u003csup\u003e\u003cem\u003e-4\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eM, Pt electrode size 0.5cm×0.5cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm), diffusion length (D\u003c/em\u003e\u003csub\u003e\u003cem\u003eL\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e) 4.0 cm, sunlight intensity 3.24 mWcm\u003c/em\u003e\u003csup\u003e\u003cem\u003e-2\u003c/em\u003e\u003c/sup\u003e\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-7502096/v1/be6f2af817567301ad04d1d1.png"},{"id":90850489,"identity":"3a3e6485-e1b7-4122-bfb0-4011e8fece5e","added_by":"auto","created_at":"2025-09-09 03:00:39","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":42038,"visible":true,"origin":"","legend":"\u003cp\u003eStudy of the electrical performance of the PG cells on the forward direction potential and backward direction potential reaction (Hysteresis curve)\u003csup\u003e\u003cem\u003e#\u003c/em\u003e\u003c/sup\u003e\u003cem\u003e[Tropaeline-O] 2.66×10\u003c/em\u003e\u003csup\u003e\u003cem\u003e-5\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eM, [Benzalkonium chloride]2.21×10\u003c/em\u003e\u003csup\u003e\u003cem\u003e-2\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eM, [Oxalic acid]9.9×10\u003c/em\u003e\u003csup\u003e\u003cem\u003e-4\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eM, Pt electrode size 0.5cm×0.5cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5cm), diffusion length (D\u003c/em\u003e\u003csub\u003e\u003cem\u003eL\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e) 4.0 cm, sunlight intensity 3.24 mWcm\u003c/em\u003e\u003csup\u003e\u003cem\u003e-2\u003c/em\u003e\u003c/sup\u003e\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-7502096/v1/b0eb77aadbf820d7690edf9b.png"},{"id":90851210,"identity":"d5ac3f43-ab39-4fb5-982d-7d7676d35c33","added_by":"auto","created_at":"2025-09-09 03:16:39","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":36197,"visible":true,"origin":"","legend":"\u003cp\u003eSpectra of pure dye aqua solution;\u003csup\u003e\u003cstrong\u003e#\u003c/strong\u003e\u003c/sup\u003e(a) Pre-illumination spectra (at 19.4 \u003csup\u003e0\u003c/sup\u003eC),(b) Post-illumination spectra after three hours long illumination.\u003csup\u003e\u003cem\u003e#\u003c/em\u003e\u003c/sup\u003e\u003cem\u003e[Tropaeline-O]2.66×10\u003c/em\u003e\u003csup\u003e\u003cem\u003e-5\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eM, Saturated Calomel Electrode as reference electrode\u003c/em\u003e\u003cem\u003e\u003cstrong\u003e,\u003c/strong\u003e\u003c/em\u003e\u003cem\u003e Pt electrode size 0.5cm×0.5cm, diffusion length (D\u003c/em\u003e\u003csub\u003e\u003cem\u003eL\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e) 0.5 cm, artificial sunlight intensity 3.24 mWcm\u003c/em\u003e\u003csup\u003e\u003cem\u003e-2\u003c/em\u003e\u003c/sup\u003e\u003cem\u003e.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"12.png","url":"https://assets-eu.researchsquare.com/files/rs-7502096/v1/88af5baa0e2cf7becd18cde2.png"},{"id":90851017,"identity":"6b20f929-75cf-4e0b-828e-6c9a28d6c4f5","added_by":"auto","created_at":"2025-09-09 03:08:39","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":38207,"visible":true,"origin":"","legend":"\u003cp\u003eSpectra of Tropaeline-O dye alkali solution;\u003csup\u003e\u003cstrong\u003e#\u003c/strong\u003e\u003c/sup\u003e(c) Pre-illumination spectra of the\u003cem\u003e \u003c/em\u003eTropaeline-O dye alkali solution\u003cem\u003e \u003c/em\u003esolution,\u003cem\u003e(d) \u003c/em\u003ePost-illumination Spectra of\u003cem\u003e \u003c/em\u003eTropaeline-O dye alkali solution after three hours long illumination\u003cem\u003e.\u003c/em\u003e\u003csup\u003e\u003cem\u003e\u003cstrong\u003e#\u003c/strong\u003e\u003c/em\u003e\u003c/sup\u003e\u003cem\u003e[Tropaeline-O]2.66×10\u003c/em\u003e\u003csup\u003e\u003cem\u003e-5\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eM, [Benzalkonium chloride]2.21×10\u003c/em\u003e\u003csup\u003e\u003cem\u003e-2\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eM, pH 13.11, [Oxalic acid]1.5×10\u003c/em\u003e\u003csup\u003e\u003cem\u003e-3\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eM, Saturated Calomel Electrode as reference electrode\u003c/em\u003e\u003cem\u003e\u003cstrong\u003e,\u003c/strong\u003e\u003c/em\u003e\u003cem\u003e Pt electrode size 0.5cm×0.5cm, diffusion length (D\u003c/em\u003e\u003csub\u003e\u003cem\u003eL\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e) 0.5 cm, artificial sunlight intensity 3.24 mWcm\u003c/em\u003e\u003csup\u003e\u003cem\u003e-2\u003c/em\u003e\u003c/sup\u003e\u003cem\u003e.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"13.png","url":"https://assets-eu.researchsquare.com/files/rs-7502096/v1/e3dbaad55b44a04d99698aed.png"},{"id":90851674,"identity":"161c0306-1a4e-444c-b064-0fc407a12a1e","added_by":"auto","created_at":"2025-09-09 03:24:39","extension":"png","order_by":14,"title":"Figure 14","display":"","copyAsset":false,"role":"figure","size":51256,"visible":true,"origin":"","legend":"\u003cp\u003eComparison of spectra: a consolidated spectra of Tropaeline-O dye in aqueous solution\u003csup\u003e# \u003c/sup\u003eand Tropaeline-O dye in alkali electrolyte solution**,(a)Pre-illumination Spectra of pure dye aqua solution, (b) post-illumination spectra of pure dye aqua solution, (c) pre-illumination spectra of Tropaeline-O dye in alkali electrolyte solution, and (d) Post-illumination spectra of Tropaeline-O dye in alkali electrolyte solution\u003cem\u003e.\u003c/em\u003e\u003csup\u003e\u003cem\u003e#\u003c/em\u003e\u003c/sup\u003e\u003cem\u003e[Tropaeline-O]2.66×10\u003c/em\u003e\u003csup\u003e\u003cem\u003e-5\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eM;\u003c/em\u003e\u003csup\u003e\u003cem\u003e\u003cstrong\u003e**\u003c/strong\u003e\u003c/em\u003e\u003c/sup\u003e\u003cem\u003e[Tropaeline-O]2.66×10\u003c/em\u003e\u003csup\u003e\u003cem\u003e-5\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eM, [Benzalkonium chloride]2.21×10\u003c/em\u003e\u003csup\u003e\u003cem\u003e-2\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eM, [Oxalic acid]1.5×10\u003c/em\u003e\u003csup\u003e\u003cem\u003e-3\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eM, pH 13.11, illuminated with artificial sunlight intensity 3.24 mWcm\u003c/em\u003e\u003csup\u003e\u003cem\u003e-2\u003c/em\u003e\u003c/sup\u003e\u003cem\u003e.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"14.png","url":"https://assets-eu.researchsquare.com/files/rs-7502096/v1/080c49e398076d4136bd394f.png"},{"id":91801812,"identity":"b7437e0b-aba3-4ea9-9b14-29599b52fb7d","added_by":"auto","created_at":"2025-09-21 22:16:32","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3025865,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7502096/v1/4e262c6d-145f-4ec8-a5ef-57d391cc2dd7.pdf"},{"id":90850481,"identity":"89394b13-cd12-4bb4-8faa-1f8563493c81","added_by":"auto","created_at":"2025-09-09 03:00:39","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":292388,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eScheme\u003c/strong\u003e:\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eScheme-I\u003c/strong\u003e: Chemical structure of Tropaeline-O dye.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e(Scheme II): \u003c/strong\u003eTropaeline-O powder and its aqueous solution\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eScheme-III:\u003c/strong\u003e Chemical structure of Benzalkonium chloride surfactant.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eScheme-IV:\u003c/strong\u003e Chemical structure of Oxalic acid reductant.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eScheme-V\u003c/strong\u003e:\u003cstrong\u003e \u003c/strong\u003eReduction of azo dye\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eScheme-VI\u003c/strong\u003e:\u003cstrong\u003e \u003c/strong\u003eReduction of Tropaeline-O dye\u003c/p\u003e","description":"","filename":"Schemes.docx","url":"https://assets-eu.researchsquare.com/files/rs-7502096/v1/874005fa5a1d9f0db120991a.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Tropaeline-O-Alkali-Pt-Graphite based H-Shaped Photogalvanics Cells: Current-potential stability \u0026 Hysteresis curve for solar energy conversion and storage","fulltext":[{"header":"1. Introduction ","content":"\u003cp\u003eDiminishing fossils fuels, continuously worsening climatic conditions, and uninterrupted rise in assured energy needs has necessitated development of alternative energy technologies like solar power techniques with storage \u003cstrong\u003e[1].\u003c/strong\u003e Solar power can be harvested directly through the different solar power techniques such as the Organic solar cells [\u003cstrong\u003e2, 3\u003c/strong\u003e], perovskite cells [\u003cstrong\u003e4-6\u003c/strong\u003e], polymer cells \u003cstrong\u003e[7],\u003c/strong\u003e dye sensitized solar cells \u003cstrong\u003e[8-11],\u0026nbsp;\u003c/strong\u003ephotovoltaic cells [\u003cstrong\u003e5\u003c/strong\u003e],\u0026nbsp;photogalvanic cells \u003cstrong\u003e[12],\u003c/strong\u003e etc. In this regard, the photogalvanic solar cells have some peculiar characteristics of both solar energy conversion and storage. Photogalvanic cells are based on the \u003cem\u003e‘photogalvanic effect’ (i.e., modified ‘Becquerel effect’),\u0026nbsp;\u003c/em\u003ein whichthe electrode potential owes its origin to the photo-induced chemical process and shift in the redox equilibrium occurring in the bulk electrolyte\u003cstrong\u003e\u0026nbsp;[13].\u003c/strong\u003e Various studies have been reported on the optimal configuration and ultimate efficiencies of the photogalvanic cells \u003cstrong\u003e[14].\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eVarious dye/pigment sensitizers and other parameter based photogalvanic cells have been reported [\u003cstrong\u003e15-39\u003c/strong\u003e]. The dye/pigment sensitizers like\u0026nbsp;Congo Red dye \u003cstrong\u003e[15],\u003c/strong\u003e Sudan-I dye \u003cstrong\u003e[16],\u003c/strong\u003e Naphthol Green B dye \u003cstrong\u003e[17],\u003c/strong\u003e Spinach extract (\u003cem\u003echlorophyll ‘a’\u003c/em\u003e) \u003cstrong\u003e[18-20],\u0026nbsp;\u003c/strong\u003eFast Green FCF dye \u003cstrong\u003e[21]\u003c/strong\u003e\u003cstrong\u003e,\u003c/strong\u003e Methylene Blue dye \u003cstrong\u003e[22],\u003c/strong\u003e Direct Yellow-9 dye \u003cstrong\u003e[23],\u003c/strong\u003e Safranine-O dye \u003cstrong\u003e[24,25],\u003c/strong\u003e Brilliant Cresyl Blue dye \u003cstrong\u003e[26],\u003c/strong\u003e Methylene Blue dye \u003cstrong\u003e[27],\u003c/strong\u003e Metanil Yellow dye \u003cstrong\u003e[28],\u0026nbsp;\u003c/strong\u003eToluidine Blue dye \u003cstrong\u003e[29],\u003c/strong\u003e Rhodamine B \u003cstrong\u003e[30],\u003c/strong\u003e Indigo Carmine \u003cstrong\u003e[31],\u003c/strong\u003e [Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003eS\u003csub\u003e2\u003c/sub\u003e(1-Pipdtc)\u003csub\u003e2\u003c/sub\u003e(H\u003csub\u003e2\u003c/sub\u003eO)\u003csub\u003e2\u003c/sub\u003e] inorganic dye \u003cstrong\u003e[32],\u003c/strong\u003e Sudan-I\u0026nbsp;\u003cstrong\u003e[33]\u003c/strong\u003e,\u0026nbsp;fast green FCF dye\u0026nbsp;\u003cstrong\u003e[34],\u003c/strong\u003e Carmoisine ‘A’ dye \u003cstrong\u003e[35],\u003c/strong\u003e Titan Yellow dye \u003cstrong\u003e[36],\u003c/strong\u003e\u0026nbsp; \u0026nbsp;etc. have been explored in photogalvanics. \u0026nbsp;Other parameter based photogalvanic cells like\u0026nbsp;high energy throughput using photogalvanic solar techniques and environmentally benign chemical system \u003cstrong\u003e[37],\u003c/strong\u003e comparative photogalvanic study of various alkali materials in the transparent H-cell design \u003cstrong\u003e[38],\u0026nbsp;\u003c/strong\u003eexploratory insight into\u0026nbsp;the\u0026nbsp;photogalvanics of\u0026nbsp;the\u0026nbsp;complete electrolyte and\u0026nbsp;its individual chemical components\u0026nbsp;\u003cstrong\u003e[39],\u0026nbsp;\u003c/strong\u003eetc., have also been reported.\u003c/p\u003e\n\u003cp\u003eA literature survey reveals that various chemical and physical variables are key determinants of the optimized and enhanced performance of the photogalvanic cells. The sensitizer material is the main constituent of the photogalvanic cells. The higher diffusion of the sensitizer molecules and the cost/conductivity/catalytic activity/redox property/robustness of the electrode materials is the key for having efficient solar energy harvesting process through the durable photogalvanic cells. The light absorbing dye materials having very low molecular weight and higher diffusivity with low cost and robust graphite counter electrodes have not received much attention of the researchers. Tropaeline-O dye (characterized by potentially higher diffusivity and photo-stability) is a low molecular weight material, and it has been widely used as an indicator in the Pb-C batteries \u003cstrong\u003e[40].\u0026nbsp;\u003c/strong\u003eTropaeline-O dye with saturated calomel electrode (a delicate and costly electrode) has also found limited applications in photogalvanic cells with quite similar electrical parameters (potential 998 mV, current 3200 μA, and power 829.5 μW) at all illumination window sizes \u003cstrong\u003e[41].\u003c/strong\u003eBut, the saturated calomel electrode is a delicate and costly electrode (local cost ~35 USD/piece), and therefore, not suitable for fabrication of low cost and sustainable Tropaeline-O dye based photo-galvanic cells.\u003c/p\u003e\n\u003cp\u003eSo far reported studies on photogalvanic cells have exploited SCE/Combination electrodes as the counter electrodes. These electrodes are very delicate, non-durable and costly for realizing the efficient and durable photo-galvanic cells. Thus, to fill this research gap in the research area of photo-galvanic cells, the present study exploiting tropaeline-O dye sensitizer with low cost and robust graphite counter electrode has been undertaken.The literature survey also reveals that ‘the tropaeline-O dye sensitizer-Oxalic acid reductant- Benzalkonium chloride surfactant chemical couple’ with low cost and robust graphite counter electrode has not attracted the attention of photogalvanicists so far. It is also reported that the use of alkaline medium and small Pt electrodes is conducive for good electrical output of the photo-galvanic cells\u003cstrong\u003e\u0026nbsp;[1, 13, 15-22].\u003c/strong\u003e The efficacy of the graphite electrodes is extensively reported for dye-sensitized solar cells, i.e., a class of cells exploiting dye as sensitizers as in the photo-galvanic cells \u003cstrong\u003e[42-47]\u003c/strong\u003e. Therefore, the authors have used the combination of “The Tropaeline-O sensitizer, oxalic acid reductant, Benzalkonium chloride surfactant, NaOH alkali, H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm, total 30 ml electrolyte use) covered by RS PRO black PVC electrical tape, very small Pt working electrode (0.5 cm × 0.5 cm), and graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm)” for realizing further enhanced and stable electrical output. In present research, The Tropaeline-O sensitizer, oxalic acid reductant, Benzalkonium chloride surfactant, NaOH alkali, H-shaped tube and\u0026nbsp;low cost and robust graphite counter electrode based photogalvanic chemical system has shown the optimum value of the cell’s electrical parameters, as follows; dark potential 389 mV, maximum potential (V\u003csub\u003emax\u003c/sub\u003e) 680 mV, open-circuit potential (V\u003csub\u003eoc\u003c/sub\u003e) 671 mV, maximum current (i\u003csub\u003emax\u003c/sub\u003e) 6500 µA, short-circuit current (i\u003csub\u003esc\u003c/sub\u003e) 1000 µA, current at power point (i\u003csub\u003epp\u003c/sub\u003e) 1000 µA, potential at power point (V\u003csub\u003epp\u003c/sub\u003e) 122 mV, power at power point (P\u003csub\u003epp\u003c/sub\u003e) 122.0 µW, fill factor (FF) 0.18, and conversion efficiency (CE) 2.73 %.\u0026nbsp;\u003c/p\u003e"},{"header":"2. Materials and Method","content":"\u003cp\u003e\u003cstrong\u003e\u003cem\u003e2.1. Materials used\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e-\u003c/strong\u003e The chemicals, Tropaeline-O dye, Oxalic acid, Benzalkonium Chloride, and NaOH have been used as photo-sensitizer, reductant, surfactant, and alkali medium, respectively\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eTropaeline-O dye:\u003c/em\u003e\u003c/strong\u003e The characteristics of the Tropaeline-O dye \u003cem\u003e(Loba Chemie Pvt. Ltd, Mumbai, India)\u003c/em\u003e\u0026nbsp; are as, synonyms names -Acid Orange 6, Resorcinol Yellow; M.F. C\u003csub\u003e12\u003c/sub\u003eH\u003csub\u003e9\u003c/sub\u003eN\u003csub\u003e2\u003c/sub\u003eNaO\u003csub\u003e5\u003c/sub\u003eS; M.W. 316.27 gm/mol; physical state,\u0026nbsp;orange to dark brown powder; soluble in water, alcohol;\u0026nbsp;\u0026lambda;\u003csub\u003emax\u003c/sub\u003e 488 nm- 492 nm; pH transition range, 11.1 (yellow color) to 12.7 (red-orange color); C.I. No.14270; M.R.P.\u0026nbsp;INR 708/5 gm (Indian Currency); used also as pH Indicator, etc.\u003c/p\u003e\n\u003cp\u003eThe Tropaelin-O dye (\u003cstrong\u003eScheme-I\u003c/strong\u003e) has been used as an indicator to indicate the need for replacement of the Zn electrode on its consumption in the carbon-zinc batteries. The Tropaelin-O dye as indicator produces a bright red-orange color in a potassium hydroxide alkali solution showing that replacement is needed in a few weeks after the color signal is observed \u003cstrong\u003e[40].\u003c/strong\u003e The Tropaeline-O (TPO) is an azo-aromatic dye susceptible to the microbial degradation (fungi induced) \u003cstrong\u003e[48]\u003c/strong\u003e and photo catalytic degradation seeing color change from greenish yellow color to orange color, red color, violet color and brown color \u003cstrong\u003e[49].\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003ePreparation of solution: M/500 Stock solution of the Tropaeline-O (TPO) has been prepared by weighing 0.07 gm of Tropaeline-O (TPO) compound and by dissolving it in 100 ml of the singly distilled water\u003cstrong\u003e\u0026nbsp;(Scheme II).\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eBenzalkonium chloride (BAC):\u003c/em\u003e\u003c/strong\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003eThe characteristics of the Benzalkonium chloride \u003cem\u003e(Ases Works Laboratory Chemical Davison, Jodhpur, Rajasthan, India);\u003c/em\u003e chemical formula [C\u003csub\u003e6\u003c/sub\u003eH\u003csub\u003e5\u003c/sub\u003eCH\u003csub\u003e2\u003c/sub\u003eN (CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003eRCl], R is mixture of the alkyls (R 8);\u0026nbsp;Physical state\u0026nbsp;pale yellow liquid; Soluble in water, etc. The Benzalkonium chloride (BAC) surfactant (\u003cstrong\u003eScheme-III\u003c/strong\u003e) can be easily removed from waste water using its (BAC)\u0026nbsp;oxidation in the aqueous solution by S\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e8\u003c/sub\u003e\u003csup\u003e2-\u003c/sup\u003e/Fe\u003csup\u003e2 +\u003c/sup\u003e process. The microbial fuel cell system can be applied as bio-sensor for the toxicity test of BAC degradation products\u0026nbsp;\u003cstrong\u003e[50].\u003c/strong\u003e The BAC adversely affects the metabolism of the microbial organisms\u0026nbsp;\u003cstrong\u003e[50].\u003c/strong\u003e This property of the BAC is an additional advantage to be exploited once the BAC based PG electrolyte is exhausted and discarded for use as an antimicrobial agent.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eOxalic acid:\u003c/em\u003e\u003c/strong\u003e The characteristics of the Oxalic acid \u003cem\u003e(Qualigens Fines Chemicals, Mumbai, India)\u003c/em\u003e\u0026nbsp; are as, \u0026nbsp; purity 99.5\u0026nbsp;% [maximum limits of impurities, sulfated ash 0.1 %, chloride (Cl\u003csup\u003e-1\u003c/sup\u003e) 0.005 %, sulfate (SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e-2\u003c/sup\u003e) 0.02 %, heavy metals (Pb) and iron (Fe) 0.005 %);\u0026nbsp;M.F.\u0026nbsp;\u003ca href=\"https://pubchem.ncbi.nlm.nih.gov/#query=C2H6O6\" title=\"Find all compounds that have this formula\"\u003eC\u003csub\u003e2\u003c/sub\u003eH\u003csub\u003e6\u003c/sub\u003eO\u003csub\u003e6\u003c/sub\u003e\u003c/a\u003e; chemical formula\u0026nbsp;(COOH)\u003csub\u003e2\u003c/sub\u003e.2\u0026nbsp;H\u003csub\u003e2\u003c/sub\u003eO; M.W. 126.06; white crystalline solid: soluble in water; aqueous solution colorless, etc. (\u003cstrong\u003eScheme-IV\u003c/strong\u003e).\u003c/p\u003e\n\u003cp\u003ePreparation of solution: M/10 Stock solution of the Benzalkonium chloride surfactant has been prepared by weighing 2.55 gm of Benzalkonium chloride surfactant compound and by dissolving it in 100 ml of the singly distilled water\u003cstrong\u003e.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eSodium hydroxide\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e:\u003c/strong\u003e The characteristics of the sodium hydroxide \u003cem\u003e(Ases Works Laboratory Chemical Davison, Jodhpur, Rajasthan, India),\u003c/em\u003e chemical formula (NaOH), M.W. 40 gm/mol, purity 98 %, white solid, soluble in water, density 2.13 gm/cm\u003csup\u003e3\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eThe solutions of the all chemicals have been prepared in the singly distilled water. The stock solutions as M/500 Tropaeline-O dye sensitizer, M/100 Oxalic acid reductant, M/10 Benzalkonium Chloride surfactant, and 4M NaOH have been prepared, and stored in the amber colored vessels to protect them from the sunlight.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e2.2.\u0026nbsp;Apparatus used\u003c/em\u003e-\u0026nbsp;The apparatus as the\u0026nbsp;digital pH meter model no. 335 (\u003cem\u003eSystronics India Ltd., Ahmedabad, India)\u003c/em\u003e for measuring the potential in millivolt (mV), a platinum electrode as the negative terminal of the cell, a graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), as the positive terminal of the cell, H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm, total 30 ml electrolyte use) covered by RS PRO black PVC electrical tape, for accommodating the electrolyte and a 250 wattage incandescent tungsten filament bulb for getting artificial sunlight, and a HTC Instrument LX-101A Light Meter Luxmeter (accuracy: \u0026plusmn; 5 percent of the reading) for measuring the sunlight intensity, have been used. The platinum electrode has been used as working electrode as the authenticated data exists on its efficacy in the photogalvanic cells\u0026nbsp;[1].\u0026nbsp;It is chemically inert, and also very resistant to the corrosion. It is also readily available in a ready-to-use form and has robust ability to withstand the damage.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2.3.\u003cem\u003e\u0026nbsp;Method\u003c/em\u003e-\u0026nbsp;\u003c/strong\u003eThe\u0026nbsp;required volume of the electrolyte (consisting of the dye sensitizer, reductant, surfactant, alkali, water) is filled in the a H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm, total 30 ml electrolyte use) covered by RS PRO black PVC electrical tape, and both the electrodes (Pt and graphite) are dipped in the electrolyte solution. All the apparatus are connected in a circuit as shown in the schematic of the experimental set-up (\u003cstrong\u003eFig.1\u003c/strong\u003e).\u003c/p\u003e\n\u003cp\u003eIn the beginning, the circuit is kept open and the cell is placed in the dark condition to obtain a stable potential (dark potential-V\u003csub\u003edark\u003c/sub\u003e). After that the cell is charged by illuminating the electrolyte solution with the artificial sunlight while keeping the circuit open \u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe value of photo-potential is noted at different time intervals. During the illumination, a highest potential called maximum potential (V\u003csub\u003emax\u003c/sub\u003e) is obtained. Thereafter, a stable potential value called open-circuit potential-V\u003csub\u003eoc\u003c/sub\u003e (V\u003csub\u003eoc\u003c/sub\u003e is a bit lower than V\u003csub\u003emax\u003c/sub\u003e) is obtained, and at this stage, the cell is considered as fully charged. Thereafter, the illumination of the cell is cut-off.\u003c/p\u003e\n\u003cp\u003eAfter that the circuit is closed. The highest current obtained immediately on closing the circuit at resistance zero is noted and designated as maximum current (i\u003csub\u003emax\u003c/sub\u003e). After some time the current acquires a quite stable value called short-circuit current (i\u003csub\u003esc\u003c/sub\u003e).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe resistance of the circuit is changed by using the potentiometer. The i-V characteristic of the cell is studied (by varying the circuit resistance, zero current is obtainable at highest resistance) by varying the current value from i\u003csub\u003esc\u0026nbsp;\u003c/sub\u003eto zero value and noting the corresponding potential value. The highest product of the current and corresponding potential value is called power at power point (maximum power extractable from the cell, Ppp). The current and potential at power point are designated as current at power point (i\u003csub\u003epp\u003c/sub\u003e) and potential at power point (V\u003csub\u003epp\u003c/sub\u003e), respectively.\u003c/p\u003e\n\u003cp\u003eThe charging time (t) is calculated as, charging time = (time at which\u0026nbsp;\u003cem\u003eV\u003csub\u003evoc\u003c/sub\u003e\u003c/em\u003e is obtained)-(time at which illumination is started). The formula, (i\u003csub\u003epp\u003c/sub\u003e\u0026times;V\u003csub\u003epp\u003c/sub\u003e)/(i\u003csub\u003esc\u003c/sub\u003e\u0026times;V\u003csub\u003eoc\u003c/sub\u003e) and (i\u003csub\u003epp\u003c/sub\u003e\u0026times;V\u003csub\u003epp\u003c/sub\u003e\u0026times;FF\u0026times;100%)/(A\u0026times;P) has been used for calculation of the fill factor (FF) and conversion efficiency (CE), respectively. Where, \u0026lsquo;A\u0026rsquo; and \u0026lsquo;P\u0026rsquo; is Pt electrode area (cm\u003csup\u003e2\u003c/sup\u003e) and average artificial sun intensity\u0026nbsp;(3.24 mWcm\u003csup\u003e-2\u003c/sup\u003e), respectively. The power storage capacity of the cell is studied in terms of the half change time (t\u003csub\u003e0.5\u003c/sub\u003e), which is defined as the time duration in which the power of the cell decreases to half of the maximum power during the extraction of power from the cell in dark at a characteristics external load (resistance). The initial pH of the solution taken in the cell has been calculated by formula, pH 14-pOH \u003cstrong\u003e[15-32].\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e"},{"header":"3. Results \u0026 Discussions","content":"\u003cp\u003eThe overall performance of the 30 PG (photogalvanic) cells containing the Tropaeline-O dye as the photo-sensitizer, Benzalkonium chloride as surfactant and Oxalic acid as the reductant has been studied to get the optimum cell performance at an optimal value of the cell fabrication variables.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003e3.1. Study of potential variation with time during illumination of the cell, i-V characteristics, determination of maximum power extractible from the cell, power storage capacity\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003e3.1.1. Potential variation with time during illumination\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eEach photogalvanic cell having solutions of the Tropaeline-O\u0026nbsp;dye sensitizer, oxalic acid reductant, benzalkonium chloride surfactant, and NaOH alkali is illuminated with the artificial sunlight intensity. \u0026nbsp;Each cell has different amount of chemicals, but the pattern of change of the photo-potential with illumination time is same (\u003cstrong\u003eFig.2\u003c/strong\u003e), and the values of maximum potential (V\u003csub\u003emax\u003cs\u003emax))))\u0026nbsp;\u003c/s\u003e\u003c/sub\u003e) and open-circuit potential (V\u003csub\u003eoc\u003c/sub\u003e) is different (\u003cstrong\u003eTable-1, 4-7).\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1.\u003c/strong\u003e Change of the cell potential with time during illumination of the cell for its charging\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 78px;\"\u003e\n \u003cp\u003eTime (min.)\u003csup\u003e#\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 40px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 40px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 45px;\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 42px;\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 42px;\"\u003e\n \u003cp\u003e9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 48px;\"\u003e\n \u003cp\u003e11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp\u003e14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 45px;\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e22\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 78px;\"\u003e\n \u003cp\u003ePotential (mV)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e389\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 40px;\"\u003e\n \u003cp\u003e388\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 40px;\"\u003e\n \u003cp\u003e395\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 45px;\"\u003e\n \u003cp\u003e430\u003csup\u003e\u0026nbsp;\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 42px;\"\u003e\n \u003cp\u003e503\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 42px;\"\u003e\n \u003cp\u003e553\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 48px;\"\u003e\n \u003cp\u003e675\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp\u003e680\u003c/p\u003e\n \u003cp\u003e(V\u003csub\u003emax\u003c/sub\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 45px;\"\u003e\n \u003cp\u003e677\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e671\u003c/p\u003e\n \u003cp\u003e(V\u003csub\u003eoc\u003c/sub\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"11\" valign=\"top\" style=\"width: 541px;\"\u003e\n \u003cp\u003e\u003cem\u003e\u003csup\u003e#\u003c/sup\u003e\u003c/em\u003e\u003cem\u003e[Tropaeline-O]2.66\u003c/em\u003e\u003cem\u003e\u0026times;\u003c/em\u003e\u003cem\u003e10\u003csup\u003e-5\u003c/sup\u003eM,\u0026nbsp;\u003c/em\u003e\u003cem\u003e[Benzalkonium chloride]2.21\u0026times;10\u003csup\u003e-2\u003c/sup\u003eM, [Oxalic acid]9.9\u0026times; 10\u003csup\u003e-4\u003c/sup\u003eM, pH 12.98\u003c/em\u003e\u003cem\u003e, Pt electrode size 0.5cm\u0026times;0.5cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm),\u0026nbsp;\u003c/em\u003eH\u003cem\u003e-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm) diffusion length (D\u003csub\u003eL\u003c/sub\u003e) 4.0\u003c/em\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003cem\u003ecm, sunlight intensity 3.24\u0026nbsp;mWcm\u003csup\u003e-2\u003c/sup\u003e\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003e3.1.2. i-V characteristics\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003cem\u003eof the cell\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe model of the i-V characteristics of each cell is same (\u003cstrong\u003eFig.3\u003c/strong\u003e). The Fig. 4 shows\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003einverse relation between current and potential during i\u0026ndash;V characteristics study of the each cell. The i-V characteristics show that highest power is extractable from the cell at a characteristic current, potential and external load resistance (\u003cstrong\u003eTable 2\u003c/strong\u003e).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable. 2.\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eThe change of the potential and power with the current of PG cell system (i-V characteristics of the cell during illumination).\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"538\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eCurrent\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003e(\u0026micro;A)\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 81px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003ePotential\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003e(mV)*\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003ePower\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003e(\u0026micro;w)\u003csup\u003e#\u003c/sup\u003e\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 78px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eCurrent\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003e(\u0026micro;A)\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 84px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003ePotential\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003e(mV)*\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003ePower\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003e(\u0026micro;w)\u003csup\u003e#\u003c/sup\u003e\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003e1000(i\u003csub\u003esc\u003c/sub\u003e),(i\u003csub\u003epp\u003c/sub\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 81px;\"\u003e\n \u003cp\u003e122(V\u003csub\u003epp\u003c/sub\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003e122.0(P\u003csub\u003epp\u003c/sub\u003e)\u003csup\u003e$\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 78px;\"\u003e\n \u003cp\u003e400\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 84px;\"\u003e\n \u003cp\u003e189\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003e75.6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003e900\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 81px;\"\u003e\n \u003cp\u003e128\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003e115.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 78px;\"\u003e\n \u003cp\u003e300\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 84px;\"\u003e\n \u003cp\u003e215\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003e64.5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003e800\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 81px;\"\u003e\n \u003cp\u003e130\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003e104.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 78px;\"\u003e\n \u003cp\u003e200\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 84px;\"\u003e\n \u003cp\u003e233\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003e46.6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003e700\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 81px;\"\u003e\n \u003cp\u003e135\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003e94.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 78px;\"\u003e\n \u003cp\u003e100\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 84px;\"\u003e\n \u003cp\u003e294\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003e29.4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003e600\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 81px;\"\u003e\n \u003cp\u003e155\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003e93.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 78px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 84px;\"\u003e\n \u003cp\u003e350\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003e500\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 81px;\"\u003e\n \u003cp\u003e180\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003e90.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 78px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 84px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"6\" valign=\"top\" style=\"width: 538px;\"\u003e\n \u003cp\u003eVariation of the power and potential with current during i\u0026ndash;V characteristics study;\u003cem\u003e(a)current vs potential (a decreasing linear curve),(b)current vs power (a parabolic curve with maxima showing max. power 917.7\u003c/em\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003cem\u003e\u0026micro;w extractable from the cell at a characteristics external load resistance,\u003csup\u003e#\u003c/sup\u003e\u003c/em\u003e\u003cem\u003e[Tropaeline-O]2.66\u003c/em\u003e\u003cem\u003e\u0026times;\u003c/em\u003e\u003cem\u003e10\u003csup\u003e-5\u003c/sup\u003eM,\u0026nbsp;\u003c/em\u003e\u003cem\u003e[Benzalkonium chloride]2.21\u0026times;10\u003csup\u003e-2\u003c/sup\u003eM, [Oxalic acid]9.9\u0026times;10\u003csup\u003e-4\u003c/sup\u003eM, pH 12.98,\u0026nbsp;\u003c/em\u003e\u003cem\u003ePt electrode size 0.5cm\u0026times;0.5 cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm) diffusion length (D\u003csub\u003eL\u003c/sub\u003e) 4.0\u003c/em\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003cem\u003ecm, sunlight\u0026nbsp;intensity 3.24 mWcm\u003csup\u003e-2\u003c/sup\u003e\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eFor this photogalvanic chemical system, the optimum value of the cell\u0026rsquo;s electrical parameters is as: dark potential 389 mV, maximum potential (V\u003csub\u003emax\u003c/sub\u003e) 680 mV, open-circuit potential (V\u003csub\u003eoc\u003c/sub\u003e) 671 mV, maximum current (i\u003csub\u003emax\u003c/sub\u003e) 6500 \u0026micro;A, short-circuit current (i\u003csub\u003esc\u003c/sub\u003e) 1000 \u0026micro;A, current at power point (i\u003csub\u003epp\u003c/sub\u003e) 1000 \u0026micro;A, potential at power point (V\u003csub\u003epp\u003c/sub\u003e) 122 mV, power at power point (P\u003csub\u003epp\u003c/sub\u003e) 122.0 \u0026micro;W, fill factor (FF) 0.18, conversion efficiency (CE) 2.73 %. The optimal cell performance has been obtained at following optimum cell fabrication parameters:\u003cem\u003e\u0026nbsp;\u003c/em\u003e[Tropaeline-O] 2.66 \u0026times; 10\u003csup\u003e-5\u0026nbsp;\u003c/sup\u003eM, [Benzalkonium chloride] 2.21 \u0026times; 10\u003csup\u003e-2\u0026nbsp;\u003c/sup\u003eM, [Oxalic acid] 9.9 \u0026times; 10\u003csup\u003e-4\u0026nbsp;\u003c/sup\u003eM, pH 12.98, \u0026nbsp;Pt electrode size 0.5 cm \u0026times; 0.5 cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm) diffusion length (D\u003csub\u003eL\u003c/sub\u003e) 4.0 cm, sunlight intensity 3.24 mWcm\u003csup\u003e-2\u003c/sup\u003e, 20.90 \u003csup\u003eo\u003c/sup\u003eC room temperature, and pre-illuminated electrolyte solution temperature 21.0 \u003csup\u003eo\u003c/sup\u003eC.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003e3.1.3. Mechanism\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe photo-electrochemistry of the oxalic acid reductant solution alone, Benzalkonium chloride surfactant solution alone, and the electrolyte solution (having mixture of the dye, reductant, and alkali) has been studied in the cell to propose a most plausible mechanism (with the help of published literature) for the photo-generation of current. The illumination of the electrolyte solution having dye sensitizer along with the reductant and alkali shows development of the\u0026nbsp;photo-potential and photo-current. The dark potential is also not due to the dye alone, but as a result of the contribution of reductant, and surfactant as well.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eOn the basis of the published literature \u003cstrong\u003e[2, 15-30]\u003c/strong\u003e the most plausible mechanism for the photo-generation of the current using Tropaeline-O dye sensitizer (TPO)-Oxalic acid reductant-Pt-Graphite photogalvanic system is proposed as below-\u003c/p\u003e\n\u003cp\u003eOn illumination of the electrolyte containing the dye, the formation of excited state of the dye photo sensitizer Tropaeline-O molecule\u0026nbsp;leave a vacancy in its ground state, This vacancy is filled by an electron donated to TPO molecule from the Oxalic acid OA reductant molecule leading to an excess\u0026nbsp;electron in the higher energy state of the TPO molecule. This excess electron is transferred to Pt electrode (working electrode placed in the illuminated chamber) as accommodation of this excess electron is difficult as it causes high instability of TPO molecule. \u0026nbsp;This excess electron moves through an external circuit to the graphite electrode (positive terminal of the cell), where it (electron) may be accepted by the dye molecule present in bulk electrode around the graphite to form the leuco/semi-form (of dye molecule).The dye molecule (leuco/semi-form) and reductant molecule (oxidized) combine to give original dye and reductant molecules \u003cstrong\u003e[51].\u0026nbsp;\u003c/strong\u003eThe photogalvanic system based on the TPO-OA-BAC is estimated to be a cyclic light-induced power generator with several reversible cycles. The semi/leuco reduced states of the TPO molecules are the electro-active species in the Pt electrode region, and the TPO molecules itself are main electro-active species in cell graphite region \u003cstrong\u003e[52].\u003c/strong\u003e This fact is also supported by the published work of Kaneko and Yamada \u003cstrong\u003e[53].\u003c/strong\u003e That the leuco/or semi reduced form of the dyes, and the dyes itself are the main electro-active species at the illuminated working electrode and the non-illuminated graphite counter electrode, respectively \u003cstrong\u003e[54].\u003c/strong\u003e The energy stored in the charge separated semi or leuco forms gets converted into the electrical energy by the so-called photogalvanic effect. The most plausible outlines of the mechanistic aspect of the photo-generation of the current is described as below \u003cstrong\u003e(Also see Fig. 4)-\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003ePhoto-processes occurring in the electrolyte and on the surface of the Pt electrode\u003c/em\u003e\u003c/strong\u003e\u003cem\u003e:\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eTPO\u0026nbsp;\u0026nbsp;TPO*(S) \u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;TPO*(T) \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;(in bulk electrolyte)\u0026hellip;.. (1)\u003c/p\u003e\n\u003cp\u003eTPO*(T) + OA \u0026rarr; TPOˉ (Leuco) + OA\u003csup\u003e+ \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u003c/sup\u003e(in bulk electrolyte)\u0026hellip;.. (2)\u003c/p\u003e\n\u003cp\u003eTPOˉ (Leuco) \u0026nbsp; \u0026rarr; TPO + eˉ \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;(Pt electrode) \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026hellip;. (3)\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003ePhoto-processes occurring in the electrolyte of the\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003egraphite\u003cem\u003e\u0026nbsp;region:\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTPO + eˉ \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026rarr; TPOˉ (leuco) \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;(graphite region) \u0026nbsp; \u0026nbsp;\u0026hellip;.. \u0026nbsp;(4)\u003c/p\u003e\n\u003cp\u003eTPOˉ + OA\u003csup\u003e+\u003c/sup\u003e \u0026rarr; TPO + OA \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; (in bulk electrolyte) \u0026hellip;. (5)\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eWhere, the OA, OA\u003csup\u003e+\u003c/sup\u003e, TPO*, TPOˉ and eˉ is oxalic acid reductant molecule,oxidized oxalic acid reductant molecule, excited state of the Tropaeline-O dye photosensitizer molecule, semi or leuco form of the Tropaeline-O dye photosensitizer molecule, and electron, respectively. The ISC, \u0026lsquo;T\u0026rsquo; and \u0026lsquo;S\u0026rsquo; are inter system crossing process, triplet excited state of Tropaeline-O molecule, and singlet excited state of the Tropaeline-O dye photosensitizer molecule, respectively.\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003e3.1.4. Storage capacity of the cell\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe storage capacity of the cell has been observed as 440 minutes as half change time. The half change time is considered as the time duration in which the value of extracted power at a characteristics external load (resistance) from the cell reduces to the half of initial value (i.e., power at power point) in dark (\u003cstrong\u003eTable 3, Fig.5\u003c/strong\u003e).\u0026nbsp;The PG cells are characterized by their inherent power storage capacity. This power storage capacity may be attributed to the generation of the energy rich species like photo-excited sensitizer molecule and semi and /or leuco reduced forms of the sensitizer molecule. These energy rich species have certain average life time. After charging of the cell in sunlight, the illuminating source is cut-off. Thereafter, the power is extracted from the cell in dark conditions. Under dark conditions, the energy stored in the form of energy rich photo-excited species and semi/leuco species is retrieved by their deactivation in cell electrolyte to give current and power as electrical out-put. The kinetics of the photo-decay and deactivation of these excited species here is estimated to be of non-zero order \u003cstrong\u003e[16].\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 3.\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003eStorage capacity of the cell\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"547\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTime (min.)\u003csup\u003e#\u003c/sup\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 71px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eCurrent\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(\u0026micro;A)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePotential\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;(mV)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 58px;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePower\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(\u0026micro;W)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTime (min.)\u003c/strong\u003e\u003csup\u003e#\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 70px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eCurrent\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(\u0026micro;A)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePotential\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;(mV)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 73px;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePower\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(\u0026micro;W)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 71px;\"\u003e\n \u003cp\u003e1000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e122\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 58px;\"\u003e\n \u003cp\u003e122\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e190\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 70px;\"\u003e\n \u003cp\u003e900\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e109\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 73px;\"\u003e\n \u003cp\u003e98.1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 71px;\"\u003e\n \u003cp\u003e1000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e125\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 58px;\"\u003e\n \u003cp\u003e125\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e205\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 70px;\"\u003e\n \u003cp\u003e850\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e108\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 73px;\"\u003e\n \u003cp\u003e91.8\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 71px;\"\u003e\n \u003cp\u003e1000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e122\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 58px;\"\u003e\n \u003cp\u003e122\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e240\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 70px;\"\u003e\n \u003cp\u003e800\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e104\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 73px;\"\u003e\n \u003cp\u003e83.2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 71px;\"\u003e\n \u003cp\u003e1000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e121\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 58px;\"\u003e\n \u003cp\u003e121\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e280\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 70px;\"\u003e\n \u003cp\u003e800\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e101\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 73px;\"\u003e\n \u003cp\u003e80.8\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 71px;\"\u003e\n \u003cp\u003e1000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e120\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 58px;\"\u003e\n \u003cp\u003e120\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e340\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 70px;\"\u003e\n \u003cp\u003e800\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e92\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 73px;\"\u003e\n \u003cp\u003e73.6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 71px;\"\u003e\n \u003cp\u003e950\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e120\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 58px;\"\u003e\n \u003cp\u003e114\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e400\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 70px;\"\u003e\n \u003cp\u003e800\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e86\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 73px;\"\u003e\n \u003cp\u003e68.8\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e80\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 71px;\"\u003e\n \u003cp\u003e900\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e119\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 58px;\"\u003e\n \u003cp\u003e107.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e420\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 70px;\"\u003e\n \u003cp\u003e750\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 73px;\"\u003e\n \u003cp\u003e63.0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e105\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 71px;\"\u003e\n \u003cp\u003e900\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e118\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 58px;\"\u003e\n \u003cp\u003e106.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e440\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 70px;\"\u003e\n \u003cp\u003e750\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e82\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 73px;\"\u003e\n \u003cp\u003e61.5(t\u003csub\u003e0.5\u003c/sub\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e130\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 71px;\"\u003e\n \u003cp\u003e900\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e117\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 58px;\"\u003e\n \u003cp\u003e105.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e450\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 70px;\"\u003e\n \u003cp\u003e750\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e81\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 73px;\"\u003e\n \u003cp\u003e60.75\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e150\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 71px;\"\u003e\n \u003cp\u003e900\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e115\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 58px;\"\u003e\n \u003cp\u003e103.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e455\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 70px;\"\u003e\n \u003cp\u003e750\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e80\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 73px;\"\u003e\n \u003cp\u003e60.50\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e170\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 71px;\"\u003e\n \u003cp\u003e900\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e112\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 58px;\"\u003e\n \u003cp\u003e100.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 70px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 73px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"8\" valign=\"top\" style=\"width: 547px;\"\u003e\n \u003cp\u003e\u003cem\u003e\u003csup\u003e#\u003c/sup\u003e\u003c/em\u003e\u003cem\u003e[Tropaeline-O]2.66\u003c/em\u003e\u003cem\u003e\u0026times;\u003c/em\u003e\u003cem\u003e10\u003csup\u003e-5\u003c/sup\u003eM,\u0026nbsp;\u003c/em\u003e\u003cem\u003e[Benzalkonium chloride]2.21\u0026times;10\u003csup\u003e-2\u003c/sup\u003eM, [Oxalic acid]9.9\u0026times;10\u003csup\u003e-4\u0026nbsp;\u003c/sup\u003eM, pH 12.98, Pt electrode size 0.5cm\u0026times;0.5cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm), diffusion length (D\u003csub\u003eL\u003c/sub\u003e) 4.0\u003c/em\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003cem\u003ecm, sunlight intensity 3.24 mWcm\u003csup\u003e-2\u003c/sup\u003e\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003e3.2. Study of optimization of the cell performance\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe optimization of the cell performance has been studied by varying one cell fabrication variable and keeping value of other cell fabrication variables constant.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003e3.2.1. Effects of variation of the Tropaeline-O dye as photosensitizer on the PG Cells\u0026rsquo; electrical performance\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe effect of variation of the dye Tropaeline-O as photosensitizer on the PG cells\u0026rsquo; electrical performance has been studied by fabricating in all five cells. For each cell, the value of used Tropaeline-O dye concentration is different, but the value of other cell fabrication variables (other than Tropaeline-O dye concentration) is same. The highest photo-current is noted at an optimal concentration (i.e., 2.66 \u0026times; 10\u003csup\u003e-5\u003c/sup\u003eM) of Tropaeline-O dye sensitizer (\u003cstrong\u003eTable 4\u003c/strong\u003e). The relation between Tropaeline-O dye sensitizers\u0026rsquo; concentration and corresponding current is shown by a parabolic curve with maxima showing highest current at corresponding dye concentration, i.e., optimized Tropaeline-O dye concentration value, 2.66 \u0026times; 10\u003csup\u003e-5\u003c/sup\u003e M (\u003cstrong\u003eFig.6).\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eThe most plausible explanation for the observed results may be attributed to the particle nature of the matter (dye material) and radiations (sunlight). At the lower concentration range of the dye tropaeline-O photo-sensitizer, there will be limited numbers of molecules of the photo-sensitizer for absorbing photons and subsequently donating electrons at the surface of working electrode (Pt electrode). At the higher concentration range of the dye Tropaeline-O photo-sensitizer, there will be large numbers of the molecules of the photo-sensitizer which would hinder the sunlight photons to reach nearby area of the working electrode. The PG cells are diffusion controlled devices in which excited sensitizer molecule, within their excited life, must reach working electrode for photo-generation of the current. The life time of excited species is very small so only limited sensitizer molecules get photo-excited (only those which are very close to Pt) reach Pt electrode. The sensitizer molecules far away from the Pt would not be able to reach (within their life time) Pt and therefore, such molecules would not be able to contribute to the photo-generation of the current from the cell.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 4.\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eEffects of variation of the Tropaeline-O dye photo-sensitizer concentration the PG Cell system\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"535\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eCell \u0026nbsp; \u0026nbsp; \u0026nbsp;Parameters\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"5\" valign=\"top\" style=\"width: 380px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;[Tropaeline-O]\u0026times;10\u003csup\u003e-5\u0026nbsp;\u003c/sup\u003eM\u003csup\u003e#\u003c/sup\u003e \u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e0.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e0.30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e0.35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.399\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003e0.45\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eV\u003csub\u003edark\u003c/sub\u003e (mV)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e710\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e512\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e386\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e389\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003e394\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eV\u003csub\u003emax\u0026nbsp;\u003c/sub\u003e(mV)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e720\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e719\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e645\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e680\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003e678\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eV\u003csub\u003eoc\u003c/sub\u003e (mV)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e685\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e676\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e531\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e671\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003e655\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003ei\u003csub\u003emax \u0026nbsp;\u003c/sub\u003e(mA)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e6000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e7500\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e7000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e6500\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003e9000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003ei\u003csub\u003eeq\u0026nbsp;\u003c/sub\u003eor i\u003csub\u003esc\u003c/sub\u003e (mA)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e900\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e1000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e1000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e1000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003e1000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eV\u003csub\u003epp\u003c/sub\u003e (mV)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e212\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e125\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e122\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003e56\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eP\u003csub\u003epp\u003c/sub\u003e (mW)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e13.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e106.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e62.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e122.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003e28\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003ei\u003csub\u003epp\u003c/sub\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;(mA)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e600\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e500\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e500\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e1000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003e500\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003et (min.)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003e30\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eCE (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e1.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e0.76\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e2.73\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003e0.14\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eFF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e0.09\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e0.09\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003e0.04\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"6\" valign=\"top\" style=\"width: 535px;\"\u003e\n \u003cp\u003e\u003cem\u003e\u003csup\u003e#\u003c/sup\u003e\u003c/em\u003e\u003cem\u003e[Benzalkonium chloride]2.21\u0026times;10\u003csup\u003e-2\u003c/sup\u003eM, [Oxalic acid]9.9\u0026times;10\u003csup\u003e-4\u003c/sup\u003eM, pH 12.98,Pt electrode size 0.5cm\u0026times;0.5cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm),\u0026nbsp;\u003c/em\u003eH-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm)\u003cem\u003e\u0026nbsp;diffusion length (D\u003csub\u003eL\u003c/sub\u003e) 4.0\u003c/em\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003cem\u003ecm, sunlight intensity 3.24 mWcm\u003csup\u003e-2\u003c/sup\u003e\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003e3.2.2. Effects of variation of the Oxalic acid reductant concentration on the PG cells\u0026rsquo; electrical performance\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe effect of the variation of the Oxalic acid\u003cem\u003e\u0026nbsp;\u003c/em\u003ereductant on the PG cells\u0026rsquo; electrical performance has been studied by fabricating in all five cells. For each cell, the value of used Oxalic acid\u003cem\u003e\u0026nbsp;\u003c/em\u003ereductant concentration is different, but the value of other cell fabrication variables (other than Oxalic acid\u003cem\u003e\u0026nbsp;\u003c/em\u003ereductant concentration) is same. The highest photo-current is noted at an optimal concentration (i.e., 2.97 \u0026times; 10\u003csup\u003e-3\u003c/sup\u003e M) of Oxalic acid\u003cem\u003e\u0026nbsp;\u003c/em\u003ereductant (\u003cstrong\u003eTable 5\u003c/strong\u003e). The relation between Oxalic acid\u003cem\u003e\u0026nbsp;\u003c/em\u003ereductants\u0026rsquo; concentration and corresponding current is shown by a parabolic curve with maxima showing highest current at corresponding Oxalic acid\u003cem\u003e\u0026nbsp;\u003c/em\u003ereductant concentration, i.e., optimized Oxalic acid\u003cem\u003e\u0026nbsp;\u003c/em\u003ereductant concentration value, 2.97 \u0026times; 10\u003csup\u003e-3\u003c/sup\u003e M (\u003cstrong\u003eFig.7).\u0026nbsp;\u003c/strong\u003eThe most plausible explanation for the observed results may be attributed to the particle nature of the matter (Oxalic acid\u003cem\u003e\u0026nbsp;\u003c/em\u003ereductant material) and radiations (sunlight). At the lower concentration range of the Oxalic acid\u003cem\u003e\u0026nbsp;\u003c/em\u003ereductant, there will be limited numbers of molecules of the Oxalic acid\u003cem\u003e\u0026nbsp;\u003c/em\u003ereductant to reduce the limited number of dye molecules producing limited number of semi/leuco dye molecules. Subsequently, the limited number of semi/leuco dye molecules shall transfer limited numbers of electrons at the surface of working electrode (Pt electrode) leading to lower photo-current generation. The higher concentration of the reductant oxalic acid may inhibit the movement of molecule of the dye Tropaeline-O towards the electrodes in the desired time limit and may also increase back electron transfer from the molecule of dye Tropaeline-O to the reductant oxalic acid molecules. At the higher concentration range of the Oxalic acid\u003cem\u003e\u0026nbsp;\u003c/em\u003ereductant, there will be large numbers of the molecules of the Oxalic acid\u003cem\u003e\u0026nbsp;\u003c/em\u003ereductant which would hinder the sunlight photons to reach nearby area of the working electrode leading to the photo-excitation of limited numbers of the sensitizer molecules in the electrolyte adjacent to the working electrode. The recombination process (involving combination of the reduced dye molecule and the oxidized reductant molecule) disfavors the photo-generation of the current. At higher side of the reductant concentrations, this recombination process is facilitated causing reduced current generation.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 5.\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eEffects of variation of the Oxalic acid reductant concentration on PG Cell\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"526\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" valign=\"top\" style=\"width: 158px;\"\u003e\n \u003cp\u003eCell \u0026nbsp; \u0026nbsp; \u0026nbsp;Parameters\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"5\" valign=\"top\" style=\"width: 368px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; [Oxalic acid]\u0026times;10\u003csup\u003e- 3\u003c/sup\u003eM\u003csup\u003e#\u0026nbsp;\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 73px;\"\u003e\n \u003cp\u003e2.50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003e2.97\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003e3.50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e4.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e4.50\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 158px;\"\u003e\n \u003cp\u003eV\u003csub\u003edark\u003c/sub\u003e (mV)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 73px;\"\u003e\n \u003cp\u003e472\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003e389\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003e433\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e412\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e450\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 158px;\"\u003e\n \u003cp\u003eV\u003csub\u003emax\u0026nbsp;\u003c/sub\u003e(mV)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 73px;\"\u003e\n \u003cp\u003e695\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003e388\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003e704\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e668\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e680\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 158px;\"\u003e\n \u003cp\u003eV\u003csub\u003eoc\u003c/sub\u003e (mV)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 73px;\"\u003e\n \u003cp\u003e640\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003e680\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003e680\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e664\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e662\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 158px;\"\u003e\n \u003cp\u003ei\u003csub\u003emax \u0026nbsp;\u003c/sub\u003e(mA)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 73px;\"\u003e\n \u003cp\u003e10000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003e6500\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003e7000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e8500\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e6000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 158px;\"\u003e\n \u003cp\u003ei\u003csub\u003eeq\u0026nbsp;\u003c/sub\u003eor i\u003csub\u003esc\u003c/sub\u003e (mA)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 73px;\"\u003e\n \u003cp\u003e700\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003e1000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003e1000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e700\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e600\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 158px;\"\u003e\n \u003cp\u003eV\u003csub\u003epp\u003c/sub\u003e (mV)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 73px;\"\u003e\n \u003cp\u003e129\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003e122\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003e222\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e373\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e19\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 158px;\"\u003e\n \u003cp\u003eP\u003csub\u003epp\u003c/sub\u003e (mW)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 73px;\"\u003e\n \u003cp\u003e51.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003e122.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003e111.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e113.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e11.40\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 158px;\"\u003e\n \u003cp\u003ei\u003csub\u003epp\u003c/sub\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;(mA)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 73px;\"\u003e\n \u003cp\u003e400\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003e1000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003e500\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e300\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e600\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 158px;\"\u003e\n \u003cp\u003et \u0026nbsp;(min.)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 73px;\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003e22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e22\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 158px;\"\u003e\n \u003cp\u003eCE (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 73px;\"\u003e\n \u003cp\u003e0.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003e2.73\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003e2.23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e3.37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e0.04\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 158px;\"\u003e\n \u003cp\u003eFF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 73px;\"\u003e\n \u003cp\u003e0.73\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003e0.18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003e0.16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e0.24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"6\" valign=\"top\" style=\"width: 526px;\"\u003e\n \u003cp\u003e\u003cem\u003e\u003csup\u003e#\u003c/sup\u003e\u003c/em\u003e\u003cem\u003e[Tropaeline-O]2.66\u003c/em\u003e\u003cem\u003e\u0026times;\u003c/em\u003e\u003cem\u003e10\u003csup\u003e-5\u003c/sup\u003eM,\u0026nbsp;\u003c/em\u003e\u003cem\u003e[Benzalkonium chloride]2.21\u0026times;10\u003csup\u003e-2\u003c/sup\u003eM, pH 12.98, Pt electrode size 0.5cm\u0026times;0.5cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm),\u0026nbsp;\u003c/em\u003eH-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm)\u003cem\u003e\u0026nbsp;diffusion length (D\u003csub\u003eL\u003c/sub\u003e) 4.0\u003c/em\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003cem\u003ecm, sunlight intensity 3.24 mWcm\u003csup\u003e-2\u003c/sup\u003e\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003e3.2.3. Effects of variation of the Benzalkonium chloride surfactant concentration on the PG cells\u0026rsquo; electrical performance\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe effect of the variation of the Benzalkonium chloride surfactant\u003cstrong\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/strong\u003eon the PG cells\u0026rsquo; electrical performance has been studied by fabricating in all five cells. For each cell, the value of used Benzalkonium chloride surfactant\u003cstrong\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/strong\u003econcentration is different, but the value of other cell fabrication variables (other than Benzalkonium chloride concentration) is same. The highest photo-current is noted at an optimal concentration (i.e., 2.21 \u0026times; 10\u003csup\u003e-2\u003c/sup\u003e M) of Benzalkonium chloride (\u003cstrong\u003eTable 6\u003c/strong\u003e).The relation between Benzalkonium chloride concentration and corresponding current is shown by a parabolic curve with maxima showing highest current at corresponding Benzalkonium chloride concentration, i.e., optimized Benzalkonium chloride concentration value, 2.21 \u0026times; 10\u003csup\u003e-2\u003c/sup\u003e M (\u003cstrong\u003eFig.8).\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eThe most plausible explanation for the observed results may be attributed to the particle nature of the matter (Benzalkonium chloride material) and radiations (sunlight). At the lower concentration range of the Benzalkonium chloride, there will be limited numbers of molecules of the Benzalkonium chloride to solubilize the limited number of dye molecules producing limited number of semi/leuco dye molecules. Subsequently, the limited number of semi/leuco dye molecules shall transfer limited numbers of electrons at the surface of working electrode (Pt electrode) leading to lower photo-current generation. The higher concentration of the Benzalkonium chloride may inhibit the movement of molecule of the dye Tropaeline-O towards the electrodes in the desired time limit. At the higher concentration range of the Benzalkonium chloride, there will be large numbers of the molecules of the Benzalkonium chloride which would hinder the sunlight photons to reach nearby area of the working electrode leading to the photo-excitation of limited numbers of the sensitizer molecules in the electrolyte adjacent to the working electrode.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIt is a published study that surfactants have solublizing effect on the dyes molecules. The dye is most solubilized by the surfactants over their (surfactant\u0026rsquo;s) critical micelle concentration. Therefore, the dye solubility is estimated to increase linearly with increase in the surfactant concentration. This trend for rising dye solubility is reported for surfactant\u0026rsquo;s moderate concentrations only. The dye solubility is not further favored by increasing the surfactant concentrations, once the micelles have grown to a certain size. The dye solubility is adversely affected at very high surfactant concentrations owing to the formation of rod-like micelles with high increase in the viscosity \u003cstrong\u003e[28, 55].\u003c/strong\u003e According to the second law of thermodynamics, the reversibility increases the efficiency of the thermodynamic processes. In present study, the dye sensitizer is reduced to make reduction couple Dye/Dye\u003csup\u003e-\u003c/sup\u003e (i.e., Tropaeline-O/Tropaeline-O\u003csup\u003e-\u0026nbsp;\u003c/sup\u003edye). Therefore, any factor increasing the reversibility of this reduction couple will also increase the cell efficiency. It is reported in a cyclic voltammetric \u0026nbsp;study that the BAC surfactant increases the reversibility of the reduction couple of Co (II) to Co(I) in the [Co(II)(bpy)\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e2+\u003c/sup\u003e dye sensitizer \u003cstrong\u003e[56].\u003c/strong\u003e On the basis of this reported fact, the authors assume that the BAC may also have similar effect of increasing the reversibility of the Tropaeline-O/Tropaeline-O\u003csup\u003e-\u0026nbsp;\u003c/sup\u003edye reduction couple in the present study enhancing the electrical output of the PG cell.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 6.\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eEffects of variation of the Benzalkonium chloride surfactant concentration\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"519\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eCell \u0026nbsp; Parameters\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"5\" valign=\"top\" style=\"width: 363px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; [Benizalkonium chloride]\u0026times;10\u003csup\u003e-2\u003c/sup\u003eM\u003csup\u003e#\u003c/sup\u003e \u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e6.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e6.63\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e7.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e7.50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e8.00\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eV\u003csub\u003edark\u003c/sub\u003e (mV)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e414\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e389\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e417\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e683\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e472\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eV\u003csub\u003emax\u0026nbsp;\u003c/sub\u003e(mV)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e678\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e680\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e705\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e698\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e690\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eV\u003csub\u003eoc\u003c/sub\u003e (mV)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e658\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e671\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e685\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e650\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e658\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003ei\u003csub\u003emax \u0026nbsp;\u003c/sub\u003e(mA)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e10000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e6500\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e10000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e11000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e9000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003ei\u003csub\u003eeq\u0026nbsp;\u003c/sub\u003eor i\u003csub\u003esc\u003c/sub\u003e (mA)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e900\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e1500\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e1000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e900\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e1200\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eV\u003csub\u003epp\u003c/sub\u003e (mV)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e122\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e186\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e181\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e39\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eP\u003csub\u003epp\u003c/sub\u003e (mW)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e14.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e122.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e55.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e108.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e31.2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003ei\u003csub\u003epp\u003c/sub\u003e\u0026nbsp; (mA)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e800\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e1000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e300\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e600\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e800\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003et \u0026nbsp;(min.)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eCE (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e0.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e2.73\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e0.56\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e2.48\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e0.15\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eFF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e0.18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e0.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"6\" valign=\"top\" style=\"width: 519px;\"\u003e\n \u003cp\u003e\u003cem\u003e\u003csup\u003e#\u003c/sup\u003e\u003c/em\u003e\u003cem\u003e[Tropae\u003c/em\u003e\u003cem\u003eline-O\u003c/em\u003e\u003cem\u003e]2.66\u003c/em\u003e\u003cem\u003e\u0026times;\u003c/em\u003e\u003cem\u003e10\u003csup\u003e-5\u003c/sup\u003eM, [\u003c/em\u003e\u003cem\u003eOxalic acid]2.97\u0026times;10\u003csup\u003e-3\u003c/sup\u003eM, pH 12.98, Pt electrode size 0.5cm\u0026times;0.5cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm), diffusion length (D\u003csub\u003eL\u003c/sub\u003e) 4.0\u003c/em\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003cem\u003ecm, sunlight intensity 3.24 mWcm\u003csup\u003e-2\u003c/sup\u003e\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cem\u003e3.2.4. Effects of variation of alkalinity concentration on the PG cells\u0026rsquo; electrical performance\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe effect of the variation of the alkalinity on the PG cells\u0026rsquo; electrical performance has been\u0026nbsp;studied by fabricating in all five cells. For each cell, the value of used alkalinity\u003cstrong\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/strong\u003econcentration is different, but the value of other cell fabrication variables (other than alkalinity concentration) is same. The highest photo-current is noted at an optimal concentration (i.e., 2.0 M; pH 12.98) of alkalinity (\u003cstrong\u003eTable 7\u003c/strong\u003e). The relation between alkalinity concentration and corresponding current is shown by a parabolic curve with maxima showing highest current at corresponding alkalinity concentration, i.e., optimized alkalinity concentration value, 2.0 M (\u003cstrong\u003eFig.9).\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eThe PG cell system works effectively in strongly alkaline conditions. The most plausible explanation for the observed results may be attributed to the (i) particle nature of the matter/radiations, and (ii) effect of alkali on the solubility, electron donating and ionic nature of the dye molecules. At the lower concentration range of the alkalinity, there will be limited numbers of molecules of the alkali to solubilize the limited number of dye molecules producing limited number of semi/leuco dye molecules. Subsequently, the limited number of semi/leuco dye molecules shall transfer limited numbers of electrons at the surface of working electrode (Pt electrode) leading to lower photo-current generation. The higher concentration of the alkalinity may inhibit the movement of molecule of the dye Tropaeline-O towards the electrodes in the desired time limit. According to the concept of second law of thermodynamics, the reversibility of the photo-processes is a desired feature of cells for getting the higher solar energy conversion efficiency. Therefore, the reductant molecules involved in the electron exchanges with sensitizer molecules are desired to be part of reversible changes for higher electrical output of the cell. But, at high concentration of the alkali solution (i.e., very high pH), the OH\u003csup\u003e-\u003c/sup\u003e may combine chemically with the oxidized state of the oxalic acid reductant molecule, intercepting the regeneration of its (reductant) original state. The solubility of the anionic azo dye tropaeline-O is estimated to be low at lower pH range and high at high pH range. The solubilization of dyes is high in higher pH range (11-14) leading to the increased output of the PG cells as a result of increased diffusion and decreased aggregation of the dye molecules. The dye Tropaeline-O is acidic and anionic in nature. At low pH range, the anionic form is assumed to be disfavored due to increasing protonation of the sulfonic group and nitrogen atoms of the dye molecules. The electron transferring tendency of the dye molecules to the working Pt electrode is adversely affected as a result of the availability of the lower number of anionic dye molecules leading to the lower current generation in the cell. The increased anionic nature facilitates its own contribution to current also. Under the conditions of higher pH rang, the redox potential of dye molecules is more negative favoring electron transfer from dye molecule to Pt.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 7.\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eEffects of variation of alkalinity concentration on the PG cells electrical performance\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"519\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eCell \u0026nbsp; \u0026nbsp; \u0026nbsp;Parameters\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"5\" valign=\"top\" style=\"width: 363px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;pH (Alkalinity)\u003csup\u003e#\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e11.80\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e12.40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e12.98\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e13.10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e13.50\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eV\u003csub\u003edark\u003c/sub\u003e (mV)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e407\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e394\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e389\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e430\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e470\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eV\u003csub\u003emax\u0026nbsp;\u003c/sub\u003e(mV)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e719\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e663\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e680\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e740\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e749\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eV\u003csub\u003eoc\u003c/sub\u003e (mV)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e702\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e660\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e671\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e710\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e746\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003ei\u003csub\u003emax \u0026nbsp;\u003c/sub\u003e(mA)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e6000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e6000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e6500\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e7000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e10000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003ei\u003csub\u003eeq\u0026nbsp;\u003c/sub\u003eor i\u003csub\u003esc\u003c/sub\u003e (mA)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e1000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e1100\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e1500\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e600\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e800\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eV\u003csub\u003epp\u003c/sub\u003e (mV)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e101\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e122\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e101\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e39\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eP\u003csub\u003epp\u003c/sub\u003e (mW)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e10.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e70.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e122.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e20.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e23.4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003ei\u003csub\u003epp\u003c/sub\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;(mA)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e1000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e700\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e1000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e200\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e600\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003et \u0026nbsp;(min.)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e22\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eCE (%) \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e0.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e0.84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e2.73\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e0.11\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eFF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 72px;\"\u003e\n \u003cp\u003e0.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e0.09\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 74px;\"\u003e\n \u003cp\u003e0.18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"6\" valign=\"top\" style=\"width: 519px;\"\u003e\n \u003cp\u003e\u003cem\u003e\u003csup\u003e#\u003c/sup\u003e\u003c/em\u003e\u003cem\u003e[Tropaeline-O]2.66\u003c/em\u003e\u003cem\u003e\u0026times;\u003c/em\u003e\u003cem\u003e10\u003csup\u003e-5\u003c/sup\u003eM,\u0026nbsp;\u003c/em\u003e\u003cem\u003e[Benzalkonium chloride]2.21\u0026times;10\u003csup\u003e-2\u003c/sup\u003eM, [Oxalic acid] 9.9\u0026times;10\u003csup\u003e-4\u003c/sup\u003eM, Pt electrode size 0.5cm\u0026times;0.5cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm), diffusion length (D\u003csub\u003eL\u003c/sub\u003e) 4.0\u003c/em\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003cem\u003ecm, sunlight intensity 3.24 mWcm\u003csup\u003e-2\u003c/sup\u003e\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003e3.2.5. Summary result of the optimization of cell fabrication variables and corresponding optimized electrical performance of the cell\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFor this photogalvanic chemical system, the optimum value of the cell\u0026rsquo;s electrical parameters is as: dark potential 389 mV, maximum potential (V\u003csub\u003emax\u003c/sub\u003e) 680 mV, open-circuit potential (V\u003csub\u003eoc\u003c/sub\u003e) 671 mV, maximum current (i\u003csub\u003emax\u003c/sub\u003e) 6500 \u0026micro;A, short-circuit current (i\u003csub\u003esc\u003c/sub\u003e) 1000 \u0026micro;A, current at power point (i\u003csub\u003epp\u003c/sub\u003e) 1000 \u0026micro;A, potential at power point (V\u003csub\u003epp\u003c/sub\u003e) 122 mV, power at power point (P\u003csub\u003epp\u003c/sub\u003e) 122.0 \u0026micro;W, fill factor (FF) 0.18, conversion efficiency (CE) 2.73 %. The optimal cell performance has been obtained at following optimum cell fabrication parameters:\u003cstrong\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e[Tropaeline-O] 2.66 x 10\u003csup\u003e-5\u0026nbsp;\u003c/sup\u003eM, [Benzalkonium chloride] 2.21 \u0026times; 10\u003csup\u003e-2\u0026nbsp;\u003c/sup\u003eM, pH 13.72, [Oxalic acid] 0.99 \u0026times; 10\u003csup\u003e-3\u0026nbsp;\u003c/sup\u003eM, Pt electrode size 0.5 cm \u0026times; 0.5 cm, Pt electrode size 0.5 cm \u0026times; 0.5 cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm) diffusion length (D\u003csub\u003eL\u003c/sub\u003e) 4.0 cm, sunlight intensity 3.24 mWcm\u003csup\u003e-2\u003c/sup\u003e, 20.90 \u003csup\u003eo\u003c/sup\u003eC room temperature, and pre-illuminated electrolyte solution temperature 21.0 \u003csup\u003eo\u003c/sup\u003eC.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003e4.\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u003cem\u003eStudy\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u003cem\u003eof the variation and stability of open-circuit potential (V\u003csub\u003eoc\u003c/sub\u003e) \u0026amp; short-circuit current (i\u003csub\u003esc\u003c/sub\u003e)\u003csub\u003e\u0026nbsp;\u003c/sub\u003eover time during illumination of the cell\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe variation and stability of the open-circuit potential (V\u003csub\u003eoc\u003c/sub\u003e) and short-circuit current (i\u003csub\u003esc\u003c/sub\u003e) over time has been studied after fully charging the cell and keeping illumination of the cell on. The value of V\u003csub\u003eoc\u003c/sub\u003e and i\u003csub\u003esc\u003c/sub\u003e has been found quite steady and stable for over a very long time, i.e., potential ~809 mV\u003csub\u003e\u0026nbsp;\u003c/sub\u003eto 803 mV\u003csub\u003e\u0026nbsp;\u003c/sub\u003eover ~485 minutes\u0026nbsp;and current\u003csub\u003e\u0026nbsp;\u003c/sub\u003e~1100 \u0026micro;A-900\u003csub\u003e\u0026nbsp;\u003c/sub\u003e\u0026micro;A over ~420 minutes and\u0026nbsp;700 mV over 1448 minutes (\u003cstrong\u003eTable 8, Table 9, Fig. 10)\u003c/strong\u003e. The steady state of the potential and current may be attributed to the establishment of the quasi-equilibrium of the photo-electrochemical processes occurring in the bulk of electrolyte and on the interface between electrolyte and electrode. On the illumination of the electrolyte, the photo-processes are irreversible and fast in the beginning leading to the abrupt rise in the photo-potential. After some time, the reverse processes gains momentum to establish the quasi-equilibrium leading to the corresponding equilibrium and steady state value of the cell potential. The steady state value of the cell current (i\u003csub\u003esc\u003c/sub\u003e) may also be attributed to the same nature of the quasi-equilibrium state of the photo-electrochemical processes.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe quite steady and stable value of V\u003csub\u003eoc\u003c/sub\u003e and i\u003csub\u003esc\u003c/sub\u003e over a very long time is indicative of the photo-stability of the Tropaeline-O dye based PG cells. The methodology and the nature of the observations used in the present study for showing the photo-stability of the PG cells is also supported by the published work of Cheng \u003cem\u003eet al\u003c/em\u003e\u003cstrong\u003e. [57].\u003c/strong\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003eIn published study, Cheng \u003cem\u003eet al.\u003c/em\u003e has studied current and potential over long time to observe a stable values inferring stability of the ruthenium dye based DSSCs cell.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 8.\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eStudy of the variation and stability of open-circuit potential (V\u003csub\u003eoc\u003c/sub\u003e) over time during illumination of the cell\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 146px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eTime\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003e(min.)\u003csup\u003e#\u003c/sup\u003e\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 165px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eOpen-circuit\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003epotential\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003e(mV)*\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 144px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eTime\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003e(min.)\u003csup\u003e#\u003c/sup\u003e\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 138px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eOpen-circuit potential\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003e(mV)*\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 146px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 165px;\"\u003e\n \u003cp\u003e409\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 144px;\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 138px;\"\u003e\n \u003cp\u003e807\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 146px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 165px;\"\u003e\n \u003cp\u003e410\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 144px;\"\u003e\n \u003cp\u003e50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 138px;\"\u003e\n \u003cp\u003e806\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 146px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 165px;\"\u003e\n \u003cp\u003e415\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 144px;\"\u003e\n \u003cp\u003e90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 138px;\"\u003e\n \u003cp\u003e805\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 146px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 165px;\"\u003e\n \u003cp\u003e426\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 144px;\"\u003e\n \u003cp\u003e240\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 138px;\"\u003e\n \u003cp\u003e804\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 146px;\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 165px;\"\u003e\n \u003cp\u003e430\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 144px;\"\u003e\n \u003cp\u003e360\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 138px;\"\u003e\n \u003cp\u003e803\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 146px;\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 165px;\"\u003e\n \u003cp\u003e450\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 144px;\"\u003e\n \u003cp\u003e390\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 138px;\"\u003e\n \u003cp\u003e803\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 146px;\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 165px;\"\u003e\n \u003cp\u003e809\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 144px;\"\u003e\n \u003cp\u003e400\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 138px;\"\u003e\n \u003cp\u003e803\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"4\" valign=\"top\" style=\"width: 593px;\"\u003e\n \u003cp\u003e\u003cem\u003e*negative value,\u003csup\u003e#\u003c/sup\u003e\u003c/em\u003e\u003cem\u003e[Tropaeline-O]2.66\u003c/em\u003e\u003cem\u003e\u0026times;\u003c/em\u003e\u003cem\u003e10\u003csup\u003e-5\u003c/sup\u003eM,\u0026nbsp;\u003c/em\u003e\u003cem\u003e[Benzalkonium chloride]2.21\u0026times;10\u003csup\u003e-2\u003c/sup\u003eM, [Oxalic acid]9.9\u0026times;10\u003csup\u003e-4\u003c/sup\u003eM, Pt electrode size 0.5cm\u0026times;0.5cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm), diffusion length (D\u003csub\u003eL\u003c/sub\u003e) 4.0\u003c/em\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003cem\u003ecm, sunlight intensity 3.24 mWcm\u003csup\u003e-2\u003c/sup\u003e\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003eTable 9.\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eStudy of the variation and stability of \u003cem\u003eshort-circuit current (i\u003csub\u003esc\u003c/sub\u003e)\u0026nbsp;\u003c/em\u003eover time during illumination of the cell\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 115px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eTime\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003e(min.)\u003csup\u003e#\u003c/sup\u003e\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 174px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eShort-circuit current\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003e(\u0026micro;A)\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 102px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eTime\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003e(min.)\u003csup\u003e#\u003c/sup\u003e\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 174px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eShort-circuit current (\u0026micro;A)\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 115px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 174px;\"\u003e\n \u003cp\u003e1100\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 102px;\"\u003e\n \u003cp\u003e180\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 174px;\"\u003e\n \u003cp\u003e950\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 115px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 174px;\"\u003e\n \u003cp\u003e1100\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 102px;\"\u003e\n \u003cp\u003e210\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 174px;\"\u003e\n \u003cp\u003e950\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 115px;\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 174px;\"\u003e\n \u003cp\u003e1000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 102px;\"\u003e\n \u003cp\u003e300\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 174px;\"\u003e\n \u003cp\u003e900\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 115px;\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 174px;\"\u003e\n \u003cp\u003e1000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 102px;\"\u003e\n \u003cp\u003e310\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 174px;\"\u003e\n \u003cp\u003e900\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 115px;\"\u003e\n \u003cp\u003e30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 174px;\"\u003e\n \u003cp\u003e1000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 102px;\"\u003e\n \u003cp\u003e360\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 174px;\"\u003e\n \u003cp\u003e900\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 115px;\"\u003e\n \u003cp\u003e60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 174px;\"\u003e\n \u003cp\u003e1000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 102px;\"\u003e\n \u003cp\u003e390\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 174px;\"\u003e\n \u003cp\u003e900\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 115px;\"\u003e\n \u003cp\u003e85\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 174px;\"\u003e\n \u003cp\u003e1000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 102px;\"\u003e\n \u003cp\u003e420\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 174px;\"\u003e\n \u003cp\u003e900\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 115px;\"\u003e\n \u003cp\u003e135\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 174px;\"\u003e\n \u003cp\u003e1000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 102px;\"\u003e\n \u003cp\u003e1448\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 174px;\"\u003e\n \u003cp\u003e700\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"4\" valign=\"top\" style=\"width: 565px;\"\u003e\n \u003cp\u003e\u003cem\u003e\u003csup\u003e#\u003c/sup\u003e\u003c/em\u003e\u003cem\u003e[Tropaeline-O]2.66\u003c/em\u003e\u003cem\u003e\u0026times;\u003c/em\u003e\u003cem\u003e10\u003csup\u003e-5\u003c/sup\u003eM,\u0026nbsp;\u003c/em\u003e\u003cem\u003e[Benzalkonium chloride]2.21\u0026times;10\u003csup\u003e-2\u003c/sup\u003eM, [Oxalic acid]9.9\u0026times;10\u003csup\u003e-4\u0026nbsp;\u003c/sup\u003eM, Pt electrode size 0.5cm\u0026times;0.5cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm), diffusion length (D\u003csub\u003eL\u003c/sub\u003e) 4.0\u003c/em\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003cem\u003ecm, sunlight intensity 3.24 mWcm\u003csup\u003e-2\u003c/sup\u003e\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003e3.2.6.\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u003cem\u003eE\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u003cem\u003electrical performance of the PG cells in the forward direction (i \u0026amp; V change) and backward direction (V \u0026amp; i change) (\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u003cem\u003eHysteresis curve)\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIn present study, the electrical performances of the PG cell in both the forward direction and backward direction have been observed as almost same and historically quite repetitive (\u003cstrong\u003eTable 10, Fig. 11).\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eThe forward direction curve and backward direction curve almost superimposes on each other giving almost negligible area of the hysteresis loop showing quite good stability of the photo-galvanic system. The hysteresis observations on the stability aspect of the photogalvanic system are in line with the observations on the stability of photogalvanic system supported by the study on the steady state and stability of the current and potential.\u003c/p\u003e\n\u003cp\u003eThe hysteresis phenomenon is basically linked with the magnetism. Hysteresis curve is drawn by plotting a curve between two magnetic variables. One curve is drawn for change in value of one variable with change in value of other variables in forward direction, and another curve is drawn for change in value of one variable with change in value of other variables in backward direction. Both forward direction curve and backward direction curve taken together constitute the hysteresis curve. The large area of the hysteresis curve signifies the greater loss in the energy, the low stability of the system, and the lower memory capability of the system to restore history. The hysteresis curve (J-V curve) is reported for DSSCs \u003cstrong\u003e[58].\u003c/strong\u003e It is reported that the photovoltaic performance parameters (Voc, j\u003csub\u003esc\u003c/sub\u003e) obtained in the normal sweep are smaller than that in the reverse sweep \u003cstrong\u003e[59].\u003c/strong\u003e Prompted by this published study, the authors have determined hysteresis curve for PG cell as well by (i) first, slowly increasing external load resistance (changing from minimum to highest possible) value to get various current values in decreasing order with corresponding potential values in forward sweep, and (ii) thereafter, slowly decreasing external load resistance (changing from highest to minimum possible) to get various current values in increasing order with corresponding potential values in the backward sweep. The observed hysteresis curve (i-v curves of both forward and backward sweeps taken together) is a loop of two overlapping linear curves. This observation of hysteresis curve in present study is indicative of almost no energy loss in backward sweep. The values of the current and potential of backward sweep are almost equal to that in normal forward sweep. This way, the observation of the PG cells in present study is quite different than the work reported on DSSCs.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 10\u003c/strong\u003e\u003cstrong\u003e.\u0026nbsp;\u003c/strong\u003eStudy of the electrical performance of the PG cells on the forward direction potential and backward direction potential reaction (Hysteresis curve)\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"541\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 79px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eCurrent (\u0026micro;A)\u003csup\u003e#\u003c/sup\u003e\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eForward\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003edirection\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003epotential (mV)\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 102px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eBackward\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003edirection\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003epotential\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003e(mV) \u0026nbsp;\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eCurrent\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003e(\u0026micro;A)\u003csup\u003e#\u003c/sup\u003e\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eForward direction\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003epotential (mV)\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eBackward direction\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003epotential (mV) \u0026nbsp;\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 79px;\"\u003e\n \u003cp\u003e1000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e36\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 102px;\"\u003e\n \u003cp\u003e35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e400\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e227\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e225\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 79px;\"\u003e\n \u003cp\u003e900\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e39\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 102px;\"\u003e\n \u003cp\u003e37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e300\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e232\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e231\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 79px;\"\u003e\n \u003cp\u003e800\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e42\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 102px;\"\u003e\n \u003cp\u003e40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e200\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e362\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e360\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 79px;\"\u003e\n \u003cp\u003e700\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e125\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 102px;\"\u003e\n \u003cp\u003e126\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e100\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e388\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e388\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 79px;\"\u003e\n \u003cp\u003e600\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e149\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 102px;\"\u003e\n \u003cp\u003e150\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e401\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e404\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 79px;\"\u003e\n \u003cp\u003e500\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e222\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 102px;\"\u003e\n \u003cp\u003e221\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cem\u003e\u003csup\u003e#\u003c/sup\u003e\u003c/em\u003e\u003cem\u003e[Tropaeline-O]2.66\u003c/em\u003e\u003cem\u003e\u0026times;\u003c/em\u003e\u003cem\u003e10\u003csup\u003e-5\u003c/sup\u003eM,\u0026nbsp;\u003c/em\u003e\u003cem\u003e[Benzalkonium chloride]2.21\u0026times;10\u003csup\u003e-2\u003c/sup\u003eM, [Oxalic acid]9.9\u0026times;10\u003csup\u003e-4\u0026nbsp;\u003c/sup\u003eM, Pt electrode size 0.5cm\u0026times;0.5cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm), diffusion length (D\u003csub\u003eL\u003c/sub\u003e) 4.0\u003c/em\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003cem\u003ecm, sunlight intensity 3.24 mWcm\u003csup\u003e-2\u003c/sup\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003e3.2.7.\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u003cem\u003ePhoto-absorption and photo-stability of the\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u003cem\u003eTropaeline-O dye sensitizer in pure form and in electrolyte\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe photo-stability of the dye sensitizer molecules greatly affects the electrical output and the life of the cell. Here, the dye photo-stability means the chemical stability of the dye molecule in the presence of other chemical reagents (reductant, surfactant, alkali, acid, etc.) and sunlight. The every dye molecule has a characteristics chemical and chromophoric structure (skeletal structure with substituent including active functional groups). This peculiar chromophoric and chemical structure of the dye molecules enables it to show a characteristics absorption and electron donor/acceptor property. As long as the chemical structure remains intact, the absorption and electron donor/acceptor property of the dye molecules remains unchanged ensuring stable photo-galvanic property of the photo-galvanic cells. As the chemical structure of the dye changes by way of group change and/or fragmentation, the dye will not be available for its original light absorption and electron-donor properties leading to the instability in the photo-galvanic property (i.e., generated current, potential, power; life of the cell; etc.) \u003cstrong\u003e[60].\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe photo-absorption property of the Tropaeline-O dye sensitizer in pure form and in electrolyte is shown in \u003cstrong\u003eFig.12, Fig.13, and Fig.14.\u003c/strong\u003e The Tropaeline-O dye sensitizer is the main fabrication component of the cell as it is the light absorbing material. The light absorption property is characterized by the position and intensity of the UV-Visible spectral band. Therefore, the pre-illuminated and post-illuminated spectrum of the pure Tropaeline-O dye sensitizer has been studied in the aqueous medium as well as in the electrolyte. The UV-Visible spectra has been taken with the help of Single Beam UV-Visible Spectrophotometer-108 (Systronics, Ahmedabad, Gujarat, India) and cuvette cells [manufactured by Optiglass Ltd., UK; properties as the transmissions 82.3 % (at 200 nm), 84.3 % (at 220 nm) and 85 % (at 85 nm), and width 10 mm].\u003cem\u003e\u0026nbsp;\u003c/em\u003eThe 2.66 \u0026times; 10\u003csup\u003e-5\u0026nbsp;\u003c/sup\u003eM Tropaeline-O dye sample solution spectra has been determined by taking singly distilled water solvent in the reference cuvette cell.\u003c/p\u003e\n\u003cp\u003eThe pure aqueous solution of\u0026nbsp;Tropaeline-O dye at 2.66\u0026times;10\u003csup\u003e-5\u0026nbsp;\u003c/sup\u003eM has been observed to show absorbance from the 200 nm to 900 nm. The dye shows favorable absorption property both in the UV region (wavelength maxima 360 nm, absorbance 2.69; 260 nm with 0.45 absorbance) as well in the visible region (wavelength maxima 430 nm, absorbance 1.54,\u0026nbsp;molar extinction coefficient 57894 Mol\u003csup\u003e-1\u0026nbsp;\u003c/sup\u003eL cm\u003csup\u003e-1\u003c/sup\u003e).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe published value of the wavelength maxima of aqueous solution of\u0026nbsp;Tropaeline-O dye in visible region is 430 nm \u003cstrong\u003e[61].\u0026nbsp;\u003c/strong\u003eBoiko \u003cem\u003eet al.\u003c/em\u003e has also reported two peaks at 345 nm and 420 nm, with diverse absorbance value, specified for Tropaeline-O in aqueous medium\u003cstrong\u003e\u0026nbsp;[59].\u0026nbsp;\u003c/strong\u003eBoiko \u003cem\u003eet al.\u003c/em\u003e has explained this phenomenon on the basis of conjugation effect of electron clouds in the double bond of chromophore groups of Tropaeline-O molecule. Thus, the observed wavelength maximum (at 360 nm in UV range and at 430 nm in visible range) of aqueous Tropaeline-O dye solution in the present study is also validated by the published literature. The similarity of observed and published data shows that the sample of dye used is a Tropaeline-O sensitizer. The absorption property of the Tropaeline-O sensitizer make it a suitable light absorbing material as it absorb in the most convenient spectral region (visible) of the sunlight.\u003c/p\u003e\n\u003cp\u003eThe post-illuminated spectra of the aqueous\u0026nbsp;Tropaeline-O dye solution almost resemble that of pre-illuminated spectra except the disappearance of the absorption maxima of UV region after illumination. The band at wavelength maxima in visible region remains almost intact (with slight hyperchromic shift) on illumination showing that this Tropaeline-O dye is a good material for harvesting the sunlight in the visible region specifically at 430 nm. A bare look at the Fig.3 shows almost overlapping between pre-illuminated spectral curve and post-illuminated spectral curve (spectra obtained after three hours long illumination of electrolyte) showing robust photo-stability of the Tropaeline-O dye sensitizer. The stability of the dye sensitizer is the backbone of stable photo-galvanic cells producing stable current and potential over long time. Therefore, the observation of steady state potential (\u003cstrong\u003eTable 3.11\u003c/strong\u003e), steady state current (\u003cstrong\u003eTable 3.12\u003c/strong\u003e), and hysteresis curve (\u003cstrong\u003eTable 3.13\u003c/strong\u003e) may be attributed to the good photo-stability of the Tropaeline-O dye sensitizer in the present study.\u003c/p\u003e\n\u003cp\u003esensitizer, oxalic acid reductant, BAC surfancatnt, and alkali in aqueous medium.The photo-absorption property of the Tropaeline-O dye sensitizer in the electrolyte solution is influenced by the alkali, surfactant, and reductant. Therefore, the pre-illuminated and post-illuminated spectrum of the Tropaeline-O dye sensitizer in the electrolyte has been studied to explain the opto-electrochemical phenomenon of the photo-galvanic cells in the present study.\u003cem\u003e\u0026nbsp;\u003c/em\u003eThe 2.66\u0026times;10\u003csup\u003e-5\u0026nbsp;\u003c/sup\u003eM Tropaeline-O dye electrolyte solution sample spectra have been determined by taking reference solution in the reference cuvette cell. The spectra of dye alkali solution has been determined by taking sample solution (0.133 ml of M/500 Tropaeline-O, 0.99 ml of M/100 Oxalic acid, 2.21 ml of M/10 Benzalkonium chloride, 5 ml of 4M NaOH, and 1.66 ml of singly distilled water; total 10 ml solution) in sample cuvette cell and reference solution (0.99 ml of M/10 Oxalic acid, 2.21 ml of M/10 \u0026nbsp;Benzalkonium chloride, 5 ml of 4M NaOH, and 1.8 ml of singly distilled water; total 10 ml solution) in reference cuvette cell.\u003c/p\u003e\n\u003cp\u003eThe electrolyte solution (having Tropaeline-O dye at 2.66\u0026times;10\u003csup\u003e-5\u003c/sup\u003e M) has been observed to show absorbance from the 200 nm to 900 nm. The dye in the electrolyte solution shows favorable absorption property both in the UV region (band at 240 nm with absorbance 1.07; wavelength maxima band at 270 nm with absorbance 1.86) as well in the visible region (band at 400 nm with1.51 absorbance; wavelength maxima band at 495 nm with absorbance 1.36 \u0026amp; molar extinction coefficient 51127 Mol\u003csup\u003e-1\u0026nbsp;\u003c/sup\u003eL cm\u003csup\u003e-1\u003c/sup\u003e). The published value of the wavelength maxima of Tropaeline-O dye in visible region is 488 nm-492 nm (pH 13, 0.1 M NaOH alkali) and \u0026ge; 500 nm (at 1% in 0.1 M NaOH, 1 cm cuvette) \u003cstrong\u003e[62].\u003c/strong\u003e Thus, the observed wavelength maximum (at 495 nm in visible range) of Tropaeline-O dye at pH 13.11 in the present study is also validated by the published literature. The similarity of observed and published data in alkali medium also shows that the sample of dye used is a Tropaeline-O sensitizer. The absorption property of the Tropaeline-O sensitizer in alkali electrolyte solution make it a suitable light absorbing material as it (as part of electrolyte) absorb in the most convenient spectral region (visible) of the sunlight. Further, the wavelength maxima of the pure aqueous dye solution at 430 nm are batho-chromically shifted to 495 nm in alkali electrolyte (\u003cstrong\u003eFig.13\u003c/strong\u003e). This bathochromic shift may be attributed to the effect of electrolyte on the chemical structure of the dye. Authors attribute it to the formation of di-phenoxide anion structure (in the phenol moiety of dye, \u003cstrong\u003esee Scheme-I\u003c/strong\u003e) as a result of alkali induced proton removal from the -OH groups of dye. The oxy anionic structure (O\u003csup\u003e-\u003c/sup\u003e) being negatively charged work as a very strong auxochrome group to facilitate pie to pie electron transition in dye molecule leading to the bathochromic shift.\u003c/p\u003e\n\u003cp\u003eThe post-illuminated spectra of the aqueous Tropaeline-O dye electrolyte solution almost resemble that of pre-illuminated spectra of electrolyte except the disappearance of the absorption peaks of UV region after illumination. The band at wavelength maxima in visible region remains almost intact (with slight hypochromic shift) on illumination showing that this Tropaeline-O dye electrolyte is a good material for harvesting the sunlight in the visible region specifically at 495 nm. A bare look at the \u003cstrong\u003eFig.13 \u0026amp; Fig.14\u003c/strong\u003e shows almost no change in absorbance near 495 nm between pre-illuminated spectral curve and post-illuminated spectral curve (spectra obtained after three hours long illumination of electrolyte) showing robust photo-stability of the Tropaeline-O dye sensitizer with respect to its most favorable absorption wavelength. The stability of the dye sensitizer is the backbone of stable photo-galvanic cells producing stable current and potential over long time, and same also has been observed in alkali electrolyte. Therefore, the observation of steady state potential (\u003cstrong\u003eTable 11\u003c/strong\u003e), steady state current (\u003cstrong\u003eTable 12\u003c/strong\u003e), and hysteresis curve (\u003cstrong\u003eTable 13\u003c/strong\u003e) produced by dye in electrolyte may be attributed to the good photo-stability of the Tropaeline-O dye sensitizer in the electrolyte also in the present study. It is pertinent to mention a reported study that the absorption peak at 430 nm gradually decreases and finally disappears; indicating photo-degradation (Fe-doped ZnO catalyzed 99.8. %) of the Tropaeline-O dye with time during three hours long illumination \u003cstrong\u003e[61].\u003c/strong\u003e In present study, it is encouraging to note that there is no photo-degradation of dye during three hours long illumination.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eBut, the authors estimate that the photo-degradation of the Tropaeline-O dye is imminent after very long time. Therefore, the knowledge of the likely photo-products is of utmost importance for long term use of the photo-galvanic cells based on the Tropaeline-O dye sensitizer. It is reported that the azo linkage is the most labile portion of an azo dye \u003cstrong\u003e(Scheme-V)\u003c/strong\u003e \u003cstrong\u003e[42].\u003c/strong\u003e The linkage easily undergoes enzymatic breakdown, but thermal or photochemical breakdown may also take place. Degradation of azo dyes can be obtained by reduction or by oxidation. The reduction releases the colorless component amines \u003cstrong\u003e[42].\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIn present study, the dye undergoes reduction giving inference of reductive cleavage. Thus, in present study, the likely photo-degradation products (phenolic fragment and sulfonic fragment) of the Tropaeline-O dye can be estimated as below (Scheme-VI)-\u003c/p\u003e\n\u003cp\u003eThe bands at 260 nm, 360 nm, and 430 nm in the UV-Visible spectra of pure aqueous dye (Tropaeline-O) may be attributed to its azo moeity, phenolic benzenoid moeity, and sulfonic benzenoid moiety, respectively (\u003cstrong\u003eFig.3.12\u003c/strong\u003e). The low energy transition band at 430 nm is facilitated by electron push-pull effect of the para substituted groups (electron withdrawing sulfonic group and electron donating azo group). Upon irradiation, the disappearance of band at 260 nm may be attributed to the photo-cleavage of azo linkage. Upon decay of dye, the p-C\u003csub\u003e6\u003c/sub\u003eH\u003csub\u003e4\u0026nbsp;\u003c/sub\u003e(NH\u003csub\u003e2\u003c/sub\u003e)(SO\u003csub\u003e2\u003c/sub\u003eONa) and m,p-dihydroxyaniline is formed, where the electron donating tendency of the NH\u003csub\u003e2\u003c/sub\u003e group is higher than that of the azo linkage. Therefore, in the p-C\u003csub\u003e6\u003c/sub\u003eH\u003csub\u003e4\u0026nbsp;\u003c/sub\u003e(NH\u003csub\u003e2\u003c/sub\u003e)(SO\u003csub\u003e2\u003c/sub\u003eONa) fragment, the push-pull effect is greater now to give relatively enhanced absorbance at 430 nm in post-illuminated spectra. Similarly, in the m,p-dihydroxyaniline fragment, the more powerful electron donating group NH\u003csub\u003e2\u003c/sub\u003e (having more electron donating tendecy than azo) also may be the reason for enhanced absorbance at 360 nm in the post-illumination spectra. The existence of the aromatic, photo-stable, and robust benzene chromophore moiety may be the reasons for the stability of the dye.\u003c/p\u003e\n\u003cp\u003eFurther, it is also pertinent to mention here that the degradation is not limited to the dye, but other chemicals as the BAC surfactant may also undergo degradation. It is reported that PS/Fe\u003csup\u003e2+\u003c/sup\u003e catalyzed BAC oxidative-degradation process produces intermediates (like benzene derivative fragments and hydro carbon fragments) and finally minerals like CO\u003csub\u003e2\u003c/sub\u003e, NH\u003csub\u003e3\u003c/sub\u003e, H\u003csub\u003e2\u003c/sub\u003eO, and Cl\u003csup\u003e-1\u003c/sup\u003e \u003cstrong\u003e[50]\u003c/strong\u003e and authors also estimate same nature of photo-degradation products in present study.\u003c/p\u003e\n\u003cp\u003eOn the basis of the reported study on the degradation of the Tropaeline-O dye and BAC surfactant, it is certain that the present photogalvanic cells based on these chemicals (Tropaeline-O dye and BAC surfactant) are likely to see degradation. Therefore, it has to be seen that whether such cell having degraded chemicals would be able to supply energy in long term and also in conditions of no-sunlight during night hours and during cloudy hours in day time. On this aspect, authors have already given data on the power storage capacity of Tropaeline-O dye and BAC surfactant based cell providing power supply in the absence of the illumination (\u003cstrong\u003eTable 3\u003c/strong\u003e). Further, the stability aspect is also shown in terms of stability of current and potential over long time for these Tropaeline-O dye and BAC surfactant based cells (\u003cstrong\u003eTable 11-13\u003c/strong\u003e).\u0026nbsp;Further, improvement in the Tropaeline-O dye and BAC surfactant based cells is also suggested by authors on the basis of the work reported by Rangel \u003cem\u003eet al.\u0026nbsp;\u003c/em\u003e\u003cstrong\u003e[63].\u003c/strong\u003e It has been reported by Rangel \u003cem\u003eet\u0026nbsp;al.\u0026nbsp;\u003c/em\u003ethat a very fast\u003cem\u003e\u0026nbsp;\u003c/em\u003elight-to-dark or dark-to-light illuminating conditions can be changed for charging of the all solar cells. The abrupt changes in the illuminating conditions causes shifting in the cell process far away from equilibrium position of the photo-processes. This special type of illuminating the cell brings in a continuous redox reaction. It is reported that this continuous redox reaction not depends on the cell illumination (illumination is a main factor influencing the cell efficiency). Rangel \u003cem\u003eet al.\u0026nbsp;\u003c/em\u003ehas reported that this continuous redox reaction in turn causes an electrochemical effect leading to the average current value and the oscillations observed under the dark conditions. The non-linear oscillations in the current signal are reported on a rapid transition from darkness to illumination conditions. Rangel \u003cem\u003eet al.\u0026nbsp;\u003c/em\u003ehas reported that\u003cem\u003e\u0026nbsp;\u003c/em\u003etwo mechanisms (photovoltaic and chemical) operate simultaneously in the cell. The generated current and potential by the dark chemical mechanism is less than that produced by the photovoltaic mechanism. But, the beauty of this dark chemical mechanism is that it is capable of producing some current/potential (although low in value) even after dye degradation \u003cstrong\u003e[63].\u0026nbsp;\u003c/strong\u003eThus, with this discussions, the authors suggests future researchers to use the Rangel \u003cem\u003eet al.\u003c/em\u003e reported concepts to enable the Tropaeline-O dye and BAC surfactant based cells usable in dark as well with durable utility. Scientists Shigehara \u003cem\u003eet al.\u003c/em\u003e and Kamat \u003cem\u003eet al.\u003c/em\u003e have reported the efficacy of the different electrodes as Pt-Pt, and SnO\u003csub\u003e2\u003c/sub\u003e-Pt \u003cstrong\u003e[64, 65].\u003c/strong\u003e Therefore, the same (Pt-Pt, SnO\u003csub\u003e2\u003c/sub\u003e-Pt) may also be used for further improvement in the Tropaeline-O dye and BAC surfactant based photogalvanics. But, the high cost of the Pt-Pt is again a disadvantage paving way for the low cost electrodes like intercalation type electrode materials (graphite, graphene, carban nanostructure) and alloys, etc\u003cstrong\u003e.\u003c/strong\u003e \u003cstrong\u003e[65].\u003c/strong\u003e The electric polarization of graphite is an obstacle for having more efficient anodic electrode \u003cstrong\u003e[66].\u003c/strong\u003e The intercalation type electrode material lacks (i) the high energy density, (ii) the high theoretical specific capacity, and (iii) the diversity of materials available for use as cathodic for aqueous batteries \u003cstrong\u003e[67].\u003c/strong\u003e Anodes as platinized titanium (Ti/Pt), less costly but behaving electrochemically same way as the platinum have been reported by Cotton \u003cem\u003eet al.\u003c/em\u003e \u003cstrong\u003e[68].\u003c/strong\u003e The present study also involves the aqueous medium based electrolyte. For the variety of aqueous batteries, the metal anodes (including alkali metals like Li and Na; and multivalent metals like Zn, Mg, Al, etc.) has been investigated successfully providing high energy density, (ii) the high theoretical specific capacity, and (iii) the diversity of materials available for use as cathode for aqueous batteries \u003cstrong\u003e[67].\u003c/strong\u003e The drawback of the metallic electrodes is their reduced lifetime owing to sacrificial nature which depends on their shape, dimensions, and the current extracted. Thus, the protection of the sacrificial electrodes can be realized by having suitable shape and size, polarized drainage or amplified electric drainage technology \u003cstrong\u003e[69]\u003c/strong\u003e, and stabilization perspective of the metal anodes for aqueous batteries \u003cstrong\u003e[67].\u003c/strong\u003e Given this reported fact, the future researchers may also focus on the use of the alkali metals and multivalent metals (having suitable shape and size, and polarized drainage or amplified electric drainage technology for their protection), and platinized titanium as anode materials for improving the present Tropaeline-O dye sensitizer and BAC based photogalvanics.\u003c/p\u003e\n\u003cp\u003eOne more important point regarding the illumination of the solar cells is that it sees a temperature rise. As far as the effect of temperature rise as a result of photo-illumination of the Tropaeline-O dye sensitizer based PG solar cells is concerned, it proves blessings in disguise. The temperature rise of about 10 \u003csup\u003eo\u003c/sup\u003eC (i.e., 29.8 \u003csup\u003eo\u003c/sup\u003eC-39.9 \u003csup\u003eo\u003c/sup\u003eC) is observed for the Tropaeline-O sensitizer based cell. This temperature rise facilitates higher thermal agitation, higher diffusion, higher solubility, and higher enthalpy leading to the favorable conditions for the higher value of cell current. The rise in the temperature increases the kinetic energy of the Tropaeolin-O molecule leading to its higher diffusion rate and the higher collision resulting increased \u0026nbsp;photocatalytic solar energy conversion. Although, the very high temperature rise (˃ 40 \u003csup\u003eo\u003c/sup\u003eC) adversely affects the cell efficiency, but in the case of present photogalvanics, the maximum temperature of the electrolyte achievable is less than the 40 \u003csup\u003eo\u003c/sup\u003eC \u003cstrong\u003e[70, 71].\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003e3.2.8.\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u003cem\u003eComparison of results of the\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u003cem\u003eTropaelinee-O dye sensitizer with similar studies\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eConventionally, the H-shaped glass tubes have been used to fabricate the PG cell. But, the recent study reported by Koli \u003cem\u003eet al.\u0026nbsp;\u003c/em\u003eon Congo Red dye sensitizer (M.W. 696.66, a diazo dye with \u0026ndash;SO\u003csub\u003e2\u003c/sub\u003eO\u003csup\u003e-\u003c/sup\u003eNa\u003csup\u003e+\u003c/sup\u003e and \u0026ndash;NH\u003csub\u003e2\u003c/sub\u003e groups) has shown that the use of simple cylindrical glass vessels is not only cheap but also more efficacious in power generation\u003cstrong\u003e\u0026nbsp;[72].\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIn present study, the Scholar have also used Pt electrode size 0.5 cm \u0026times; 0.5 cm, graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm) diffusion length (D\u003csub\u003eL\u003c/sub\u003e) 4.0 cm, vessel for fabrication of the cell based on Tropaeline-O dye sensitizer (MW 316.27, azo dye with \u0026ndash;SO\u003csub\u003e2\u003c/sub\u003eO\u003csup\u003e-\u003c/sup\u003eNa\u003csup\u003e+\u003c/sup\u003e and \u0026ndash;OH groups), and have observed enhanced electrical output consistent with the reported study. However, the power output (power 122.0 \u0026mu;W, current 1000 \u0026mu;A) of present study is relatively good than that of the study reported (power 439 \u0026mu;W, current 2100 \u0026mu;A) \u003cstrong\u003e[72].\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe nature of the dye sensitizer is the main constituent influencing the electrical output of the PG cell. In present study, as observed in (\u003cstrong\u003eTable 8, Table 9, Fig. 10)\u003c/strong\u003e the greater photo-stability of the Tropaeline-O dye sensitizer may be one of the reasons for good power (power 122.0 \u0026mu;W \u0026amp; current 1000 \u0026mu;A of present study) vis-\u0026agrave;-vis the power reported (power 439 \u0026mu;W, current 2100 \u0026mu;A) \u003cstrong\u003e[72].\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe anionic nature of the sensitizer molecule also favors the electron exchange to working electrode (from the sensitizer molecule). The used Tropaeline-O dye sensitizer molecule in the present study has lower MW 316.27 and higher ionic nature (\u0026ndash;SO\u003csub\u003e2\u003c/sub\u003eO\u003csup\u003e-\u003c/sup\u003e and \u0026ndash;O\u003csup\u003e-\u0026nbsp;\u003c/sup\u003ein alkali medium) than that\u0026nbsp;for the Congo-red molecule (MW 696.66; \u0026ndash;SO\u003csub\u003e2\u003c/sub\u003eO\u003csup\u003e-\u003c/sup\u003e in alkali medium), and this factor may also be the reason for the relatively higher electrical output in the current study. The efficient performance of the photogalvanic cells relies on in solution selective electrodes and dye solubility, with fast electron transfer thermodynamic and kinetics process. A new PG cell configuration based on the H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm) and low MW TPO dye has been exploited to favors the fast dye diffusion and consequently the thermodynamic and kinetic processes.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eTable.11\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u003cem\u003e.\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003cem\u003eComparison of results of the H-shape\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u003cem\u003evessel with higher volume of electrolyte and small volume of electrolyte\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 43px;\"\u003e\n \u003cp\u003eS.N.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003eElectrical parameters of the cells\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 187px;\"\u003e\n \u003cp\u003eFor H-vessel with higher volume of electrolyte\u003csup\u003e#\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003eFor H-vessel \u0026amp; small volume of electrolyte\u003csup\u003e@\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 43px;\"\u003e\n \u003cp\u003e1.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003ei\u003csub\u003emax\u003c/sub\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 187px;\"\u003e\n \u003cp\u003e2700 \u0026micro;A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e6500 \u0026micro;A\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 43px;\"\u003e\n \u003cp\u003e2.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003ei\u003csub\u003esc\u003c/sub\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 187px;\"\u003e\n \u003cp\u003e1600 \u0026micro;A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e1000 \u0026micro;A\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 43px;\"\u003e\n \u003cp\u003e3.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003eP\u003csub\u003epp\u003c/sub\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 187px;\"\u003e\n \u003cp\u003e265.0\u0026micro;W\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e122.0 \u0026micro;W\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 43px;\"\u003e\n \u003cp\u003e4.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003eCE \u0026nbsp; \u0026nbsp;\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 187px;\"\u003e\n \u003cp\u003e2.70 %\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e2.73%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 43px;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003eFF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 187px;\"\u003e\n \u003cp\u003e0.16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e0.18\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"4\" valign=\"top\" style=\"width: 590px;\"\u003e\n \u003cp\u003e\u003csup\u003e#\u003c/sup\u003eComparison of results of the H-vessel vessel with higher volume (62 ml) of electrolyte (for detail sees Ref. 57, table 2) and \u003csup\u003e@\u0026nbsp;\u003c/sup\u003ethe H-vessel vessel with small volume (30 ml) of electrolyte\u003cem\u003e.\u003csup\u003e#\u003c/sup\u003e\u003c/em\u003e[Congo red dye-photosensitizer]10.3\u0026times;10\u003csup\u003e-5\u003c/sup\u003eM+[formaldehyde-reductant]1.76\u0026times;10\u003csup\u003e-3\u003c/sup\u003eM+[SLS surfactant]1.32\u0026times;10\u003csup\u003e-2\u003c/sup\u003eM, Pt(0.5cm\u0026times;0.3cmelectrode, saturated calomel electrode (SCE). @)\u003cem\u003e\u003csup\u003e#\u003c/sup\u003e\u003c/em\u003e\u003cem\u003e[Tropaeline-O]2.66\u003c/em\u003e\u003cem\u003e\u0026times;\u003c/em\u003e\u003cem\u003e10\u003csup\u003e-5\u003c/sup\u003eM,\u0026nbsp;\u003c/em\u003e\u003cem\u003e[Benzalkonium chloride]2.21\u0026times;10\u003csup\u003e-2\u003c/sup\u003eM, [Oxalic acid]9.9\u0026times;10\u003csup\u003e-4\u003c/sup\u003eM, Pt electrode size 0.5cm\u0026times;0.5cm,graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm), H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm), diffusion length (D\u003csub\u003eL\u003c/sub\u003e) 4.0\u003c/em\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003cem\u003ecm, sunlight intensity 3.24 mWcm\u003csup\u003e-2\u003c/sup\u003e\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003e3.2.9.\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u003cem\u003e\u0026nbsp;Peculiarity, electrical suitability, and future prospects of the graphite as counter electrode in PG cell\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe Pt is working as the anodic electrode terminal, and the graphite electrode is working as the cathodic electrode terminal (when Pt \u0026amp; graphite forms the two terminals of the cell) in the present study. The role of Pt as anode and Graphite as cathode may be attributed to the electronic configurations, stability of the naturally occurring electronic states, and the stability of the half filled and fully filled orbital\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe Pt is working as the anodic electrode terminal, and the graphite electrode is working as the cathodic electrode terminal (when Pt \u0026amp; graphite forms the two terminals of the cell) in the present study. The role of Pt as anode and Graphite as cathode may be attributed to the electronic configurations, stability of the naturally occurring electronic states, and the stability of the half filled and fully filled orbital. The electronic configuration of the Pt (A.N.78) is [Xe]\u003csub\u003e54\u003c/sub\u003e, 4f\u003csup\u003e14\u003c/sup\u003e, 5d\u003csup\u003e9\u003c/sup\u003e,6s\u003csup\u003e1\u003c/sup\u003e, and this is the naturally occurring electronic state, i.e., natural Pt atom. It means, the Pt will tend to be in this natural neutral stable electronic state. The Pt is a very popular inert electrode, and this is enabled by its peculiar electronic configuration. In photogalvanic cells, the excited dye sensitizer molecule with excess electron sheds its electron to the Pt. It is because by taking the one electron from the dye, the Pt atom will have the stable fully and half filled orbital, i.e., 5d\u003csup\u003e10\u003c/sup\u003e, 6s\u003csup\u003e1\u003c/sup\u003e. But this state (having one excess electron) with 5d\u003csup\u003e10\u003c/sup\u003e \u0026amp; 6s\u003csup\u003e1\u003c/sup\u003e is not the most stable naturally occurring state of the Pt. Therefore, the Pt sheds excess electron to the external circuit leading to the flow of the current towards Pt terminal. Therefore, this peculiar electronic state makes the Pt as a good inert electrode providing the good electrical contact between electrolyte and the external circuit by causing good exchange of the electrons from the electrolyte to Pt to external circuit.\u003c/p\u003e\n\u003cp\u003eThe electronic configuration of the carbon (A.N. 6) is the 1s\u003csup\u003e2\u003c/sup\u003e, 2s\u003csup\u003e2\u003c/sup\u003e, 2p\u003csub\u003ex\u003c/sub\u003e\u003csup\u003e1\u003c/sup\u003e, 2p\u003csub\u003ey\u003c/sub\u003e\u003csup\u003e1\u003c/sup\u003e, 2p\u003csub\u003ez\u003c/sub\u003e\u003csup\u003e0\u003c/sup\u003e, and this is the naturally occurring electronic state, i.e., neutral carbon atom. It means, the carbon will tend to be in this natural neutral stable electronic state. The carbon is a very popular inert electrode, and this is enabled by its peculiar electronic configuration. On getting one electron from the external source, the carbon atom will have the stable fully and half filled orbital, i.e., 1s\u003csup\u003e2\u003c/sup\u003e, 2s\u003csup\u003e2\u003c/sup\u003e, 2p\u003csup\u003e3\u003c/sup\u003e. But this state (one negative charged) with 2p\u003csup\u003e3\u003c/sup\u003e is not the most stable naturally occurring state of the carbon. Therefore, the carbon sheds excess electron to the electrolyte (to dye). This way, the carbon acts as a good inert electron exchanger between external circuit and the electrolyte by taking electron from the circuit and giving this electron to the electrolyte. Further, there is also a one more aspect to be considered, and this is that the Pt is a metal, and the carbon is a non-metal. The metals basically have the property of giving the electrons. In view of this, it is justified that the Pt will give electrons to the external circuit and will behave as an anodic terminal, and the graphite will receive the electrons from the external circuit to act as a cathodic terminal. The absorbed photon energy is converted in to the electricity in the photogalvanic cell. The photogalvanic cells do not involves any chemical reaction in the electrolyte and on the surface of the electrodes for the photo-generation of the current. The electron movement from the reductant to excited dye to Pt to external circuit to graphite to dye to reductant takes place leading to the photo-generation of the current in photogalvanic cell. The electrodes are only for the electrical contact of electrolyte for completing the circuit. Therefore, the electrodes which are inert and have good electron exchange capacity shall be more suitable for the fabrication of the photogalvanic cell. In present case, the graphite electrode has all the property like inertness and good electron exchanger. As far as the SCE electrode is concerned, as used in the previously reported studies\u0026nbsp;\u003cstrong\u003e[2, 15-30]\u003c/strong\u003e it is a reference electrode involving the chemical reaction [Hg\u003csub\u003e2\u003c/sub\u003eCl\u003csub\u003e2\u003c/sub\u003e(s) + 2 e\u003csup\u003e-\u003c/sup\u003e = 2 Hg (liq.) + 2 Cl\u003csup\u003e-\u003c/sup\u003e(aq.)], and this reaction is not consistent with the only electron exchange requirement of the photogalvanic cells. Therefore, the graphite offers itself as a good counter electrode with the added advantages like (i) it is very cheap, and available at through away prices from the discarded dry cells, (ii) it is robust in making so can be handled without any fear of breaking, making it for durable use. The combination electrode/SCE is very costly and very delicate, so its handling is prone with fear of breaking making it unsuitable for the durable use.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe Graphite counter electrode\u0026rsquo;s efficacy is also reported for the DSSCs with ~ 5.01 % efficiency. The electrochemical activity of this graphite counter electrode is further enhanced by using the SnO\u003csub\u003e2\u003c/sub\u003e modified graphite electrode, i.e.,\u0026nbsp;the optimized graphite/SnO\u003csub\u003e2\u003c/sub\u003e composite \u003cstrong\u003e[42].\u003c/strong\u003e The transition metal modified graphite electrodes (i.e., carbides, Tungsten carbide) have also shown good efficiency in the DSSCs cells \u003cstrong\u003e[43, 44]\u003c/strong\u003e High conductivity and activity are highly desirable for the counter electrode. It is reported that the low cost and chemical converted graphene has high electrical conductivity (derived from the pristine grapheme) and good reduction activity for redox species (inherited from defects) making it a promising counter electrode for the dye sensitized solar cells \u003cstrong\u003e[45].\u003c/strong\u003e Good efficiency is also reported by Jayaweera et al. for the DSSCs employing a graphite counter electrode made of an optimized graphite layer thickness of 250 \u0026mu;m \u003cstrong\u003e[46].\u003c/strong\u003e At this thickness, the graphite catalytic activity is optimum showing optimum electrical output. Jayaweera et al. has reported that the amount of graphite in thin layer is insufficient to provide the required catalytic activity for the efficient reduction of electrolyte. On the contrary, the graphite resistance is higher for thick layers decreasing the current \u003cstrong\u003e[46].\u003c/strong\u003e The role of various structures (graphite nanofibre-GNF, graphite nanosheet-GNS, graphite nanoball-GNB) of the graphite counter electrode is extensively reported for dye sensitized solar cells. Among these structures, the GNB is reported as the most effective counter electrode \u003cstrong\u003e[47].\u003c/strong\u003e The DSSCs proven technology of the optimized layered graphite, SnO\u003csub\u003e2\u003c/sub\u003e composite counter electrode, metal carbides,GNB,\u0026nbsp;and chemical converted grapheme\u0026nbsp;is suggested for further improvement of the graphite counter electrode based photogalvanic cells.\u003c/p\u003e\n\u003cp\u003eTherefore, the use of graphite/modified graphite is not only cheaper, safe, easy to fabricate, more productive in terms of the power output but also more eco-friendly. On this basis, we justify utility of the graphite over the SCE, and also suggest its use in PG in future research.\u003c/p\u003e\n\u003cp\u003eThe observations of the present research are also verified by publication in the \u0026lsquo;Journal of Electroanalytical Chemistry\u0026rsquo;. In this journal (where the scholar is a author), the reported facts are as follows-\u003c/p\u003e\n\u003cp\u003e\u0026ldquo;The observed electrical output for the very cheap, robust, and durable graphite counter electrode-based cells was found better than that for the very costly, delicate, and short-lived combination electrode. The observed electrical output for the rectangular graphite counter electrode vs Pt anodic electrode was fund better than that for the cylindrical graphite counter electrode vs Pt anodic electrode. The observed electrical output for the very cheap, easily available and simple non-blackened glass boiling tube-based cells was found better than that for the costly, not-readily available, and sophisticated H-shaped glass tubebased cells. For H-shaped glass tube-based cells; power 908 \u0026mu;W, 750 \u0026mu;W, and 718 \u0026mu;W was observed for rectangular graphite, cylindrical graphite, and SCE component of combination electrode, respectively. Similarly, for simple non-blackened glass boiling tube based cells; power 1170 \u0026mu;W, 1080 \u0026mu;W, and 804 \u0026mu;W was observed for rectangular graphite cell, cylindrical graphite cell, and SCE component of combination electrode, respectively. It was observed that the use of cheap graphite and readily available boiling tubes provides an opportunity for simplified fabrication of economically more efficient cells with greatly enhanced electrical output for future studies\u0026rdquo;\u003cstrong\u003e\u0026nbsp;[73, 74].\u003c/strong\u003e\u003c/p\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eThe\u0026nbsp;Tropaeline-O dye-Oxalic acid reductant-benzalkonium chloride based photogalvanic chemical system has been studied in the present work.\u0026nbsp;H-shaped tube (diameter 2.5 cm, length 13.0 cm and bridge length 3.5 cm) diffusion length (D\u003csub\u003eL\u003c/sub\u003e) 4.0 cm, very small Pt working electrode (0.5 cm × 0.5 cm), and graphite electrode (Rectangular shape, length 2.0 cm, width 0.4cm)as counter electrode have been exploited for solar energy conversion. The observed electrical output is as follows-current\u0026nbsp;1000\u0026nbsp;μA\u003csub\u003e,\u0026nbsp;\u003c/sub\u003epower\u0026nbsp;122.0 μW, and 2.73 %.\u0026nbsp;The variation and stability of the V\u003csub\u003eoc\u003c/sub\u003e and i\u003csub\u003esc\u003c/sub\u003e over time has been studied after fully charging the cell and keeping illumination of the cell on. The value of V\u003csub\u003eoc\u003c/sub\u003e and i\u003csub\u003esc\u003c/sub\u003e has been found quite steady and stable for graphite counter electrode over a very long time, i.e., V\u003csub\u003eoc\u003c/sub\u003e ~809 mVto 803 mVover ~385 minutes and current~ 1100 µA-900µA over ~420 minutes. The electrical performances of the Photogalvanic cells in both the forward direction and backward direction in hysteresis curve have been observed as almost same and historically quite repetitive showing the stability of TPO and graphite based PG cell. The spectral, long term current and potential, and hysteresis studies have shown quite good photo-stability of the Tropaeline-O dye sensitizer as the light absorbing material. In view of the results obtained in the present study, it may be concluded that the graphite counter electrode with the tropaeline-O, benzalkonium chloride, and oxalic acid system provides a good option for fabricating a durable PG cells for harvesting solar power with storage efficiently. For future, the modified graphite electrodes may be exploited for further improvement in the PG cells.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements:\u0026nbsp;\u003c/strong\u003eThe authors thank the Department of Chemistry, Jai Narain Vyas University, Jodhpur, Rajasthan (India) for providing the necessary laboratory facilities\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of interest:\u0026nbsp;\u003c/strong\u003eThe authors declare no conflict of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability statement:\u0026nbsp;\u003c/strong\u003eAll the experimental data has already been incorporated in the manuscript \u0026amp; SI file.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding Statement:\u0026nbsp;\u003c/strong\u003eThere is no research funding for the research of this manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor\u0026nbsp;contributions\u0026nbsp;statement:\u003c/strong\u003eAuthors, R.K. and P.K., have contributed equally to every aspect of this research work including the conception, design of the work, acquisition, analysis, interpretation of data, revision, etc. Additionally, the author P.K. has also contributed as a mentor, and supervisor of the research work. 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Natural surfactant fenugreek (Trigonella foenum-graecum) seeds based photogalvanic cell for solar energy conversion and storage. \u003cem\u003eResults in Chemistry\u003c/em\u003e. 15, (2025)102220.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Schemes","content":"\u003cp\u003eSchemes I-VI are available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"H-Shape Photogalvanic cell, Tropaeline-O, Alkali, Pt-Graphite Electrode, current -potential stability \u0026 Hysteresis curve","lastPublishedDoi":"10.21203/rs.3.rs-7502096/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7502096/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eSolar energy can be harnessed and converted into power using various methods such as photo-galvanic cells. In this research, authors have investigated photo-galvanic cells based on Tropaeline-O sensitizer, oxalic acid reductant, Benzalkonium chloride surfactant, NaOH alkali, Pt and graphite electrodes in the H-shaped cell design covered by black PVC electrical tape for realizing further enhanced and stable electrical output of the cell. Observed electrical parameters \u0026nbsp;of the cell are as maximum potential 680 mV, open-circuit potential (V\u003csub\u003eoc\u003c/sub\u003e) 671 mV, maximum current 6500 µA, short-circuit current (i\u003csub\u003esc\u003c/sub\u003e) 1000 µA, and power 122.0 µW. The variation and stability of V\u003csub\u003eoc\u003c/sub\u003e and i\u003csub\u003esc\u003c/sub\u003e over time has also been studied after fully charging the cell and keeping illumination of the cell on. The value of V\u003csub\u003eoc\u003c/sub\u003e and i\u003csub\u003esc\u003c/sub\u003e has been found quite steady and stable for over a very long time, i.e., potential changes from 809 mV\u003csub\u003e \u003c/sub\u003eto 803 mV\u003csub\u003e \u003c/sub\u003ein 485 minutes, from 809 mV\u003csub\u003e \u003c/sub\u003eto 700 mV in 1448 minutes, and current\u003csub\u003e \u003c/sub\u003echanges from 1100 µA to 900\u003csub\u003e \u003c/sub\u003eµA over 420 minutes. The forward direction curve and backward direction curve (current–potential) almost superimposes on each other giving almost negligible area of the hysteresis loop showing quite good stability (current-potential) \u0026nbsp;of photo-galvanic system.\u003c/p\u003e","manuscriptTitle":"Tropaeline-O-Alkali-Pt-Graphite based H-Shaped Photogalvanics Cells: Current-potential stability \u0026amp; Hysteresis curve for solar energy conversion and storage","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-09 03:00:34","doi":"10.21203/rs.3.rs-7502096/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"342cf120-fa35-482e-9b07-f3f22ceed40e","owner":[],"postedDate":"September 9th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-09-21T22:08:23+00:00","versionOfRecord":[],"versionCreatedAt":"2025-09-09 03:00:34","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7502096","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7502096","identity":"rs-7502096","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}