Investigating the influence of TCOs and tunneling dielectric layers on TOPCon solar cell performance

Investigating the influence of TCOs and tunneling dielectric layers on TOPCon solar cell performance | 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 Investigating the influence of TCOs and tunneling dielectric layers on TOPCon solar cell performance Rabia Saeed, Sofia Tahir, Shammas Mushtaq, Ahmed Ahmed Ibrahim, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6217606/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 23 Feb, 2026 Read the published version in Silicon → Version 1 posted 14 You are reading this latest preprint version Abstract The Tunnel Oxide Passivated Contact (TOPCon) solar cell represents an advanced iteration of the first-generation PERT solar cell, renowned for its high power conversion efficiency. Performance of the TOPCon solar cells relies on characteristics of the dielectric material from which the tunneling occurs. In this study, performance of the Tunnel Oxide Passivated Contact (TOPCon) solar cells and the impact of various transparent conducting oxides and tunnelling oxide layers on them were accessed. The study involved a detailed analysis of key parameters, such as the use of TCOs (FTO, AZO, ZnO, ITO) as a passivation layer and optically transparent electrodes, in combination with different alternative tunnelling oxide dielectric layers (SiO 2 , Al 2 O 3 , HfO 2 , ZrO 2 , and TiO 2 ) by using the AFORS-HET simulation software. The results showed that existence of an ultra-thin oxide layer with low interface states density (D it ≈ 1 × 10 9 cm − 2 eV − 1 ), and pinhole density (D ph < 1 × 10 − 6 ) suppressed carrier recombination at the rear surface. The optimum solar cell performance values were found to be V oc = 693 mV, J sc = 42.71 mA/cm 2 , FF = 88.39%, and packing conversion efficiency (PCE) = 26.16% with an Al 2 O 3 tunnel dielectric layer. TCOs tunnelling oxide AFORS-HET TOPCon pin hole density surface passivation 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 Figure 15 Figure 16 Figure 17 Figure 18 Figure 19 Figure 20 Figure 21 1. Introduction Photovoltaic energy generation is an environment friendly source of renewable energy production worldwide. Crystalline silicon (c-Si) is copious in the nature, cost-effective and highly efficient, making it a commonly used material for solar cell production. Currently, crystalline silicon solar cells account for over 95% of total photovoltaic production and become indispensable in photovoltaic (PV) industry [ 1 ]. The continuous advancements in c-Si photovoltaic technology are primarily driven by innovative approaches aimed at reducing costs and improving performance. Among these, tunnel oxide passivated contact (TOPCon) structure, utilizing doped polysilicon (poly-Si) junctions; have emerged as a particularly promising practical concept. The TOPCon structure has garnered significant attention for its ability to simultaneously passivate surfaces and facilitate carrier collection. This technology helps to prevent the undesired recombination that produce at direct metal/silicon interface of both at front/rear sides of PERC solar cells (SC). It uses a technique called passivating contact [ 2 ]. Crystalline silicon solar cells that are passivated with tunnel oxide contacts utilize tunnel oxide on the rear side to reduce the recombination rate [ 3 ]. At rear passivated contact side, TOPCon solar cell uses tunnel oxide layer of 1 nm thick that is a dynamic layer of the TOPCon solar cells. Foremost role of oxide tunneling is to give effective passivation in solar cell. An ultrathin SiO x layers were generally used as a carrier selective tunneling layers due of its good passivation abilities [ 4 ]. Al₂O₃ as the tunneling layer, also serves as a common alternative to SiOₓ in TOPCon solar cells owing its superior dielectric properties [ 5 ]. Using an extremely thin Al 2 O 3 layer as hole-selective tunnel layer on the p- TOPCon solar cells has shown better outcomes, by maximizing the efficiency to about 21.16% as well as showing less contact resistance of the 1.84 mΩ⋅cm 2 [ 6 ]. Various techniques, such as plasma-assisted oxidation, thermal oxidation, ozone oxidation, atomic layer deposition (ALD), and wet-chemical oxidation, can be used to deposit an excellent ultrathin oxide layer [ 7 ]. The fixed charge of the oxide significantly influences the surface recombination velocity (SRV), thus is essential to carefully select oxide for the passivation layer [ 8 ]. Additionally, fixed charge affects cell's efficiency in circumstances of suitable bulk doping type, large bulk lifetime and the resistivity. Therefore, it is important to choose the appropriate tunnel oxide dielectric material and its optimized thickness. This selection of an appropriate tunnel oxide layer for the use along with the p -TOPCon is significant in preventing recombination under maximum power point conditions, and this phenomenon is particularly important for TOPCon [ 9 ]. Recombination is loss of the charge carriers contributed to current or the voltage generated by solar cell. Recombination primarily occurs in surface and the bulk regions, and recombination current can possibly be reduced by passivating the rear side contact. To collect all photo-generated carriers, it is necessary to minimize surface and bulk recombination that can occur within the diffusion length [ 10 ]. In order to enhance commercial solar cells further, minimizing surface recombination losses is essential. Without the presence of light, emitter recombination current exceeds the base recombination current owing to the effects of energy bandgap narrowing, Auger recombination and elevated defect density in bulk region. Field effect surface passivation and interface density optimization are techniques that minimize charge of one carrier type via employing fixed value of the charge of the other type [ 11 ]. The effective mass of tunnelling oxide layer, dielectric constant, and the barrier heights of tunnel oxide passivated contacts are significant factors controlling the bulk and the lesser carrier tunnel currents in back side for both electrons and holes. Previous research has indicated a drift in silicon dioxide (SiO 2 ) tunnel layer thickness both the p / n -type bulk, showing that tunnel oxide thicknesses must be less the 2 nm for both p / n -type cells, respectively [ 12 ]. Limited research has been conducted to assess cell working efficiency alongside tunnel oxide layer thickness with impact of the various transparent conducting oxides [ 13 ]. Therefore, research on replacing SiO₂ with alternative materials is essential to enhance cell efficiency and to better understand the impact of different tunnel oxide on PCE of solar cell. A significant number of endeavors have concentrated on TOPCon solar cells made of n-type Si substrates; however certain experiments conducted on specific p-type Si substrates. It is believed p-type Silicon are currently dominant in Silicon solar cell industry[ 14 ]. Investigating the integration of the poly-Silicon passivated layer contacts with p-type Silicon substrate is crucial for commercializing this technology and research based on p -TOPCon solar cells [ 15 ]. Systematic numerical investigation is essential for more thorough understanding of crucial parameters which impact device functionality, such as doping concentration, thickness of oxide layer, n-Silicon layer feature, interface quality additionally the recombination parameters. Steinkemper et al. , presented a good illustration of how to analyse performance of TOPCon solar cells through numerical simulation, using two various n-Si materials such as (polycrystalline and the amorphous silicon) [ 16 , 17 ]. Their attention was directed toward carrier-selective electron connections based on tunnel oxides and emphasized the types of the materials and structures that are effective for TOPCon solar cells. The present study investigates the efficiency evaluations of TOPCon solar cells via changing dielectric materials, such as SiO 2 , Al 2 O 3 , TiO 2 , ZrO 2 , and the HfO 2 , as well as transparent conductive oxides of FTO, ZnO, AZO and ITO at the front side. These materials are the potential passivation candidates for TOPCon solar cells and are analysed by AFORS-HET (Automat for the Simulation of Hetero structures) [ 18 ]. Key distinction about this work is consideration and examination of the comprehensive parameters affecting device working performance, including factors like doping concentration, oxide thickness, carrier transport, pinhole density, trap density in oxide layer and the carrier lifetime. In conclusion, our study contributes to elucidating constrictions and challenges associated with prime parameters and will provide valuable understandings for advance development of the high-performance solar cells with tunnel oxide passivated contacts. 2. Modeling and the simulation setup The AFORS-HET V.2.5, HZB (Hahn-Meitner-Institute Berlin) has been developed as powerful and flexible numerical software for heterojunction configuration. [ 19 ]. In this study, we extensively analysed solar cells structure by incorporating tunnel oxide passivated contact structure. TOPCon solar cell configuration employed within this study given as follows: front electrode/front pyramid-textured TCOs/ n + -Si/ p -Si/tunnelling oxide layer/ p + -Si/rear side electrode. We described carrier transport from the dielectric tunnel oxide via considering thermionic emission with the help of thermionic field model as well as tunneling model. Optical absorption was explained through multiple reflections and coherence model. For electrical layers and the optical layers default parameters are commonly referenced in published research [ 9 ]. Here are the various parameters: t for thickness, Chi for electron affinity energy, SRV for surface recombination velocity, d k for relative dielectric constant, Na for acceptor concentration, N d for donor concentration, E g for band gap, m e ​ represents the relative effective mass of the electron, while m h denotes the relative effective mass of the hole,D ph pin hole density through the insulator layer (dimensionless). AFORS-HET, despite being 1-dimensional simulation software, can handle pinholes. In oxide film, pinholes are micro holes that act as leak channels for most carriers. Several research reports have been published in presence of the pinholes in ultrathin SiO x tunnel layer at different times [ 20 ], [ 21 ]. Through the pinholes, substantial fraction of carriers would be leak from the dielectric thin layer. However if pinholes are spread in a 2D dielectric, fraction of leaked carriers can be integrated. Therefore, leaked carrier percentage could be addressed as a 1D circumstance. Simulated cell structure is graphically represented in Fig. 21 , and Tables 1 and 2 presented the set parameters. Table 1 Parameters for the device simulation Designed structure layers Optimized parameter Ag t = 1 × 10 − 6 m SiN x t = 75 nm TCO (FTO, AZO, ZnO, ITO) t=(60,60,30,75) nm Front contact boundary w/o the absorption loss, standard texture surface (54.74°), flat band Front metal contact MS Schottky contact model, S p =10 6 cms − 1 ,S n =10 6 cms − 1 n -type silicon emitter layer t = 0.1µm, dk = 11.9,N d =3× 10 18 cm − 3 , N a =0 cm − 3 ,chi = 4.09eV,N c =1.23× 10 19 cm −3 ,E g =1.08eV, µ n = 185.5cm 2 V − 1 s − 1 ,µ p = 169.2cm 2 V − 1 s − 1 ,V e =1×10 7 cms −1 , rho = 2.4g, N v =1.17× 10 19 cm − 3 ,V h =1×10 7 cms −1 P -type silicon wafer layer t = 150 µm, dk = 11.9, N d =0 cm − 3 ,Na = 1.5× 10 17 cm − 3 , chi = 4.05eV,N c =2.8× 10 19 cm −3 ,E g =1.123eV, ,µ n = 594.6cm 2 V − 1 s − 1 ,µ p = 296.8 cm 2 V − 1 s − 1 ,V e =1×10 7 cms − 1 , rho = 2.4g ,V h =1×10 7 cm s − 1 ,N v =2.6× 10 19 cm −3 Back contact MS Schottky contact model, S p =10 6 cms − 1 S n =10 6 cms − 1 Rear contact boundary w/o the absorption loss, Plane surface, flat band Ag electrode t = 1 × 10 − 6 m Table 2 Tunneling properties for the various dielectric layers Parameters SiO 2 Al 2 O 3 HfO 2 ZrO 2 TiO 2 Electron tunneling mass(m e−ox ) 0.41m o 0.40 m o 0.11m o 0.28 m o 10 m o Hole tunneling mass(m h−ox ) 0.32 m e 0.35 m e 0.29 m e 0.28 m e 0.81 m e Band-gap(E g ) 9.00 eV 7.50 eV 5.80 eV 5.70 eV 3.2 eV Electron Affinity (χ) 0.90 eV 1.15 eV 2.04 eV 1.65 eV 1.58 eV Fixed charge(dielectric/Si interface + 1×10 12 cm − 3 -1×10 13 cm −3 + 2×10 12 cm −3 -1×10 11 cm −3 -5×10 8 cm − 3 3. Results and discussion 3.1 Optimization of TCO’s thickness and the doping concentration In the present work, carrier lifetime, pinhole density and interface trap density (D it ) deviation curves and the corresponding output parameters of TOPCon solar cell are illustrated. Initially, we modeled changes in cell working performance by varying thickness of the TCOs, and the results are shown in Figs. 1 , 2 , 3 , and 4 . We selected the optimized thickness value for various TCOs and then doping concentration was varied from 10 15 to 10 20 cm − 3 . The efficiency obtained was 24.22% at the 8×10 20 cm − 3 for the FTO, 24.32% at the 8×10 20 cm − 3 for the AZO, 25.49% at the 7×10 20 cm − 3 for the ZnO, and 25.56% at the 7×10 20 cm − 3 for ITO doping concentrations. The doping concentration significantly affected the efficiency of whole cell and maximum efficiency was achieved at high doping density. Indium tin oxide transparency is directly onto the silicon wafer, and transparent conductive oxide film at the front acts as an antireflection coating. Indium tin oxide (ITO) appeared as the better choice for the TCO materials due to its maximum transmission rate of above 80%, superior conductivity of 10 4 Ω −1 cm − 1 , low refractive index, low light absorption and high stability [ 22 ]. Reverse saturation current decreases when the doping concentration increases from reasonably minimum value of 10 15 cm − 3 ,resulting in a rise in open circuit voltage then eventually a rise in conversion efficiency. 3.2 Optimization of tunnel oxide layer’s thickness in TOPCon solar cell The main focus of this work is on various tunneling oxide layers in combination with different TCOs that are utilized to optimize cell performance. We simulated TOPCon solar cells by using different TCOs with tunneling oxide layers of SiO 2 , Al 2 O 3 , HfO 2 , ZrO 2 and TiO 2 . The oxide layer is an important part of TOPCon structure, as it can passivate dangling bonds on the surface of c-Silicon, thus reducing trap density. It is crucial to precisely control thickness of oxide layer to ensure proper tunneling effects. It is important to note that increasing tunnel oxide layer thickness will decrease tunneling efficiency. According to an insulator tunneling concept [ 23 , 24 ] equation for tunneling current is given as: \(\:{\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\varvec{J}}_{\varvec{t}\varvec{u}\varvec{n}\varvec{n}\varvec{e}\varvec{l}}=\frac{\varvec{q}{\varvec{n}}_{\varvec{i}\varvec{o}}^{2}{\varvec{v}}_{\varvec{t}\varvec{h}}}{{\varvec{N}}_{\varvec{e}\varvec{f}\varvec{f}}}\) e - \(\:\:\frac{2{\varvec{t}}_{\varvec{o}\varvec{x}}}{\varvec{ħ}}\sqrt{2\varvec{q}{\varvec{m}}_{\varvec{e}\varvec{f}\varvec{f},\varvec{o}\varvec{x}{\varvec{\varPhi\:}}_{\varvec{o}\varvec{x}}}}\) = \(\:\frac{\varvec{q}{\varvec{n}}_{\varvec{i}\varvec{o}}^{2}{\varvec{v}}_{\varvec{t}\varvec{h}}}{{\varvec{N}}_{\varvec{e}\varvec{f}\varvec{f}}}\) = \(\:{\varvec{P}}_{\varvec{t}\varvec{u}\varvec{n}\varvec{n}\varvec{e}\varvec{l}}\) (1 Here the J tunnel refers to the oxide tunneling current density, while n io denotes the charge carrier density in the intrinsic silicon, q represents the electronic charge, and V th indicates the thermal velocity of charge carriers holes for p-type and electrons for n-type materials, N eff is the effective charge carrier density, and m eff,ox stands for the effective mass of charge carriers in the oxide, specifically for holes in the case of hole tunneling and electrons in the case of electron tunneling, Φ Ox refers to the barrier height for the oxide, which varies depending on whether holes or electrons are the charge carriers, with the barrier height at the valence band for holes and at the conduction band for electrons ,t ox represents the thickness of the oxide and P tunnel is the tunnelling probability. Equation (1) clearly indicates the reducing the thickness of the insulator leads to an increase in tunnelling probability thus, higher tunnelling current. Meanwhile the insulator layer thickness is of minimum nanometres, thickness of tunnel oxide is changed from the range of 0.3 nm to the 2 nm to evaluate working efficiency corresponding to each tunnel oxide thickness. Initially, efficiency increases gradually, but as thickness of the tunnel layer increases, efficiency steadily reduces. The results are given in Figs. 5 , 6 , 7 and 8 . The conversion efficiency looks likely to decrease as a result of reduced current flow at 1.3 to 1.5 nm, giving maximum results. The current density, which directly impacts efficiency, is examined in relation to the oxide thickness. As thickness steadily rises, number of the charge carriers tunneling through interface layer also rises, leading to a rise in J sc (short-circuit current). However, further increases in oxide layer thickness can result in deficient diffusion length of the carriers tunneling through the oxide, leading to increased recombination and a decrease in J sc . Interestingly, the fill factor (FF) is initially maximum but falls steadily as the oxide thickness increases. Transparent conducting oxides (TCOs) are the semiconductors with wide bandgap (Eg) of 3.1 eV. Their properties are strongly influenced by deviations in stoichiometry, like oxygen deficit, the type and amount of the impurities present in host lattice. The characteristics of the tunnel dielectric materials containing tunnel masses, relative permittivity, the barrier height for the electrons/holes, and the fixed charge specific to every material. Solar cell performance is not well-known, particularly regarding thickness, doping concentration and the carrier lifetime etc. and thus being analyzed using numerical model by adjusting the properties and the tunnel dielectric thickness of every material. A novel understanding into the use of conventional tunnel oxide dielectric materials such as SiO 2 , ZrO 2 , and Al 2 O 3 , as well as potential materials like TiO 2 , HfO 2 and the TiO 2 is provided in the study. It also showed that the maximum dielectric tunnel oxide thickness for all materials can be calculated by effective mass of the majority charge carrier. Additionally, fixed charge influences the overall solar cell PCE under the settings of the maximum carrier lifetime, the suitable bulk doping density and the resistivity. Therefore, an optimization study is made for the selection of an appropriate tunnel oxide dielectric material. The TOPCon solar cell PCE was increased to 26.16 % by with Al 2 O 3 tunnel oxide layer as rear side tunnel passivation in cell structure. This enhancement is attributed to negative fixed charges in AlO x tunnel oxide, which provide further field-effective passivation by attracting holes to part near to the interface between the dielectric and c-Silicon. So, extraordinary quality passivation can be estimated while using the AlO x layer [27]. However a poor performance of TiO 2 can be attributed to a negative electron barrier at Si/TiO 2 interface, which hinders its function as a carrier selective contact. This results in a weakened back surface field effect on the thin silicon film, thereby degrading the cell efficiency. Among other materials, maximum performances are nearly identical, excluding for point where the fill factor drops, determined by tunnel barrier thickness. The TOPCon structure using HfO 2 demonstrates good performance at greater thickness due to its lesser band offset as compared to SiO 2 and ZrO 2 providing further transport channels through the insulating ultrathin oxide layer. 3.3: Effect of pinhole density and interface trap density through tunneling oxide layer It is observed that some pinholes exist in ultrathin oxide layer of TOPCon structure. In order to assess the influence of the tunnel oxide quality on total interface states and surface passivation, the pinhole density of the dielectric layer (D ph ) established in tunnel oxide layer was analyzed. Generation of pinholes in tunnel oxide is linked with oxidation method. In non-ideal silicon substrate, a higher number of the dislocation defects with the maximum diffusion coefficients accrue in dislocation sites that result in the formation of oxide pinholes. Additionally, rapid heating and cooling induce tensile and compressive stress, resulting in a large number of the pinholes in the SiO x tunnel layer and has a significantly lesser thermal expansion coefficient than bulk Si-doped poly-Silicon layer. It can be concluded that generation of the pinholes is primarily influenced by heating and cooling rate of TOPCon solar cell instead of the duration of the thermal treatment [28]. During the annealing process, impurity diffusion causes the breakdown of oxide integrity, resulting in the formation of pinholes, which are essentially microholes or microchannels through the tunnel oxide. Pinholes can lead to bulk carriers recombining and leaking at the interface, thereby reducing the efficiency of the cell [29]. In TOPCon solar cells it has been reported that quantum tunnelling is not sole process for the carrier transport and transport from the pinholes does exist. It is still uncertain whether transport through the pinholes is beneficial for the solar cell efficiency. In the case where the pinholes are advantageous for the solar structure, we need to determine the ideal amount of carrier transport from pinholes to maximize solar cell performance. Conversely, if transport via pinholes is detrimental to the structure efficiency, we need to establish tolerance level for transport from pinholes. To address this, we carried out an extensive simulation-based investigation of the transport of carriers in the TOPCon solar cell and investigated performance of solar cells as the function of the pinhole carrier transport. Figures 9, 10, 11, and 12 demonstrate the impact of pinhole density on the optimized solar cell parameters via the various TCOs and the tunneling layers after optimizing their thickness. When D ph is relatively small, V oc remains constant. However, with an increase in pinhole density D ph , J sc decreases. As D ph reaches large values; J sc slightly changed and selective carrier transport is significantly affected resulting in increased leakage current. This reduction in J sc ultimately leads to decreased overall efficiency [30]. Defect density is a crucial for quality of tunnel oxide and is often caused by the higher energy atom bombardment in the subsequent deposition method. In production of the TOPCon structure, various materials are essential to be processed, Furthermore, defects at the interface may arise. Excessive defects directly impact cell working performance, highlighting the necessity for optimizing D it . The interface trap density (D it ) values were integrated into AFORS-HET simulation software, and results are detailed in Figures 13, 14, 15, and 16. The effect of oxide tunnel layer quality on surface passivation and overall cell working efficiency was examined through the characteristics of interface trap density. The figures illustrate that as the total interface trap density (D it ) increased from the 1 × 10 9 cm −2 /eV to the 1 × 10 15 cm −2 /eV, both V oc and the J sc of the entire cell decreased [31]. Rapid decrease in V oc with an increase of the interface trap density is attributed to rise in recombination centres in the junction area and the subsequent increase in reverse saturation current density due to the majority of carriers being captured during the tunnelling process, thus impacting the value of V oc . When D it was at its minimum, more pronounced J sc , V oc , and the overall cell efficiency were attained. Figure 13, 14, 15 and 16 demonstrate that main factor influencing conversion efficiency was a V oc of 693 mV at lowest D it (1 × 10 9 cm −2 /eV), which correlated with a perfectly minimum oxide layer of the around 1.5 nm. Passivated emitter and rear contact solar cells (PERC), back side electrode is in direct contact with back surface field, allowing carriers on back side of the cell to pass through tunnelling mechanism in passivated contact to the AlO x layer. The tunnelling oxide, with a minimal D it value, enhances efficiency. When D it has a value about 1 × 10 9 cm −2 /eV at the less oxide layer of approximately 1.5 nm, maximum simulated value of J sc is 42.71 mA/cm 2 , J sc remains above 42.71 mA/cm 2 at D it value of the 1 × 10 9 cm −2 /eV, whereas it decreases to 20.45 mA/cm 2 when D it increases to 1 × 10 15 cm −2 /eV [32]. Controlling the impact of interface density on solar cell can be achieved via adjusting the oxide thickness in layer. Therefore, it is advisable to minimize D it while increasing the tunnel layer thickness to greater than 1 nm, especially as insufficient oxidation, inadequate cleaning, subpar ultra-clean space, and other factors can lead to an increase in interface density. 3.4: Impact of minority carrier lifetime of p-type Si-wafer with different tunneling oxide layers in TOPCon cell The data represented in Figures 17,18, 19 and 20 clearly indicate that the efficiency of cells with the TOPCon structure exhibits a more pronounced improvement as minority carrier lifetime for p-type wafer increases, in comparison to BSF cells. The graphs illustrate that improvement of efficiency TOPCon solar cells is directly related to a longer minority carrier lifetime of p-type silicon. It is essential for the wafer lifetime to be at least 100 μs to observe any significant performance improvement of the TOPCon structure over standard back surface field solar cells, with greater lifetime resulting in better performance enhancement. The ideal lifetime used in the TOPCon structure should be around 500 μs, owed to the poor back side surface passivation and high back rate of surface recombination velocity of 10 6 cm s −1 for the standard back surface field cell, as opposed to the better back surface recombination velocity of 10 3 cm s −1 for the TOPCon solar cells, considering interfacial fixed charge, that can be unfavorable for the p -type and beneficial for the n -type [30]. Figure depicts the superior performance of p -TOPCon structure with an Al 2 O 3 tunneling layer, attributed to existence of the fixed negative charges at solar Si/Al 2 O 3 interface. In n -TOPCon solar cells, fixed charges at Si/dielectric interface typically amount to +1 × 10 12 cm −3 , similar to SiO 2 . Conversely, in p -TOPCon solar cells, typical value for fixed charges at the Si/dielectric interface is -1 × 10 13 cm −3 , characteristic of Al 2 O 3 [33] and detailed in Table 2. A previous study highlighted the substantial impact of effective electron-hole pair propagation and direct carrier movement towards external circuits following illumination on outstanding efficiency of the TOPCon solar structure. To get maximum efficiency of the p -type TOPCon solar cells, it is essential to enhance optical confinement within absorbing layers, improve surface passivating properties of cells, and improve thin tunnel oxide layer and the doped poly-silicon layer to improve quality of surface passivation in the TOPCon solar cell. Notably, unabsorbed light passing from rear side of the metallic contact is reflected back into the solar cell's absorbing layer, thereby rising actual value both J sc (short-circuit current density) and the PCE (power conversion efficiency). 3.5 Optimized TOPCon solar cell device We have studied the impact of the different tunneling oxide layers in combination with different TCOs in the TOPCon solar cell and used optimized calculated parameters to model it with AFORS-HET software. In the final structure, we used a transparent conductive oxide ARC of ITO layer at the top, with 1.5 nm AlO x tunneling oxide layer. We were able to improve performance of our modeled TOPCon solar cell by achieving V oc = 693 mV, J sc =42.71 mA/cm 2 , FF=88.39%, Efficiency = 26.16 % and EQE =95 %. Figure 21 demonstrates the optimized structure’s JV curve and External Quantum Efficiency (EQE). Conclusion The effect of different transparent conductive oxides (TCOs) and tunneling oxide layers was studied to understand their impact on performance of TOPCon-based solar cells. TCOs act as surface passivation and the anti-reflective layer on front textured surface, reducing light reflection and surface recombination. This results in an increased the conversion efficiency of TOPCon solar cells. By optimizing tunnel dielectric materials such as SiO 2 , ZrO 2 , Al 2 O 3 , TiO 2 , and HfO 2 , we achieved superior results showing effective passivation and optical light capture in optimized TOPCon solar cell. Ultimately, we achieved best performance with ITO as TCO and AlO x as tunneling oxide layer. The present study showed that the use of p-type silicon with the Al 2 O 3 tunneling oxide layer and ITO as TCO enhanced the TOPCon solar cell performance to 26.16%. The findings offer valuable insights for the designing and the developing the cost-effective TOPCon solar cell with enhanced performance. Declarations Acknowledgements The authors would like to acknowledge the British Council for their funding under PAK-UK ICRG 2020 project (006327/D/ISB/008/2021) to create a research group of MS, Ph.D., and postdoctoral students and establishment of “Semiconductor Physics and Renewable Energy Laboratory” (SPREL) at Government College University Faisalabad Pakistan and authors would thanks the researchers supporting project number (RSPD2025R993), King Saud University, Riyadh, Saudi Arabia Funding The authors would like to acknowledge the British Council for their funding under PAK-UK ICRG 2020 project (006327/D/ISB/008/2021) to create a research group of MS, Ph.D., and postdoctoral students and establishment of “Semiconductor Physics and Renewable Energy Laboratory” (SPREL) at Government College University Faisalabad Pakistan and authors would thanks the researchers supporting project number (RSPD2025R993), King Saud University, Riyadh, Saudi Arabia No data sets were generated or analysied during the current study. Ethical approval All authors declare that the manuscript does not contain studies on human subjects, human data, or tissues, or animals. Competing interest The authors declare no competing interests. Author’s city detail Author’s name City Rabia Saeed Faisalabad, Pakistan Sofia Tahir Faisalabad, Pakistan Shammas Mushtaq Faisalabad, Pakistan Ahmed Ahmed Ibrahim Riyadh, Saudi Arabia Javed Iqbal Faisalabad, Pakistan Effat Yasin Faisalabad, Pakistan Qurat ul Ain Asif Faisalabad, Pakistan Kiran Mehmood Faisalabad, Pakistan References Masson G et al (2020) IEA PVPS report-trends in photovoltaic applications 2020. International Energy Agency, Paris, France Madumelu C et al Impact of Oxide Thickness, Emitter Sheet Resistance, and Polysilicon Doping Concentration on the Passivation Quality and Long-Term Stability of Topcon Solar Cells . Emitter Sheet Resistance, and Polysilicon Doping Concentration on the Passivation Quality and Long-Term Stability of Topcon Solar Cells Zhou J et al (2022) Computational Exploration Toward Tunnel Oxide Passivated Contact (TOPCon) Solar Cells: Tailoring Higher Efficiency. Adv Theory Simulations 5(4):2100570 Tao Y et al (2016) Large area tunnel oxide passivated rear contact n-type Si solar cells with 21.2% efficiency. Prog Photovoltaics Res Appl 24(6):830–835 Bonilla RS et al (2017) Dielectric surface passivation for silicon solar cells: A review. Phys status solidi (a) 214(7):1700293 Cheng H et al (2022) 21.16%-efficiency p-type TOPCon solar cell with ALD-Al2O3/MoOx/Ag as a hole-selective passivating contact. Sol Energy 247:171–176 Tong H et al (2018) A strong-oxidizing mixed acid derived high-quality silicon oxide tunneling layer for polysilicon passivated contact silicon solar cell. Sol Energy Mater Sol Cells 188:149–155 Schmidt J et al (2012) Advances in the surface passivation of silicon solar cells. Energy Procedia 15:30–39 Feldmann F et al (2014) Passivated rear contacts for high-efficiency n-type Si solar cells providing high interface passivation quality and excellent transport characteristics. Sol Energy Mater Sol Cells 120:270–274 Fell A et al (2018) Modeling edge recombination in silicon solar cells. IEEE J Photovolt 8(2):428–434 Glunz SW, Preu R, Biro D (2012) Crystalline silicon solar cells: state-of-the-art and future developments. Compr Renew energy 1:353–387 Sugiura T, Matsumoto S, Nakano N (2020) Numerical analysis of p-type and n-type based carrier-selective contact solar cells with tunneling oxide thickness and bulk properties. Jpn J Appl Phys 59(SG):SGGF03 Zhang Z et al (2018) Carrier transport through the ultrathin silicon-oxide layer in tunnel oxide passivated contact (TOPCon) c-Si solar cells. Sol Energy Mater Sol Cells 187:113–122 Feldmann F et al (2014) Efficient carrier-selective p-and n-contacts for Si solar cells. Sol Energy Mater Sol Cells 131:100–104 Richter A et al (2021) Design rules for high-efficiency both-sides-contacted silicon solar cells with balanced charge carrier transport and recombination losses. Nat Energy 6(4):429–438 Steinkemper H et al (2015) Numerical simulation of carrier-selective electron contacts featuring tunnel oxides. IEEE J Photovolt 5(5):1348–1356 Steinkemper H et al (2015) Theoretical investigation of carrier-selective contacts featuring tunnel oxides by means of numerical device simulation. Energy Procedia 77:195–201 Zeng Y et al (2017) Theoretical exploration towards high-efficiency tunnel oxide passivated carrier-selective contacts (TOPCon) solar cells. Sol Energy 155:654–660 Froitzheim A et al (2003) AFORS-HET: a computer-program for the simulation of heterojunction solar cells to be distributed for public use . in 3rd World Conference onPhotovoltaic Energy Conversion , Proceedings of. 2003. IEEE Brendel R, Peibst R (2016) Contact selectivity and efficiency in crystalline silicon photovoltaics. IEEE J Photovolt 6(6):1413–1420 Rienäcker M et al (2016) Junction resistivity of carrier-selective polysilicon on oxide junctions and its impact on solar cell performance. IEEE J Photovolt 7(1):11–18 Chavan GT et al (2023) A brief review of transparent conducting oxides (TCO): the influence of different deposition techniques on the efficiency of solar cells. Nanomaterials 13(7):1226 Richter A et al (2017) n-Type Si solar cells with passivating electron contact: Identifying sources for efficiency limitations by wafer thickness and resistivity variation. Sol Energy Mater Sol Cells 173:96–105 Matsumoto T et al (2017) Ultrathin SiO2 layer formed by the nitric acid oxidation of Si (NAOS) method to improve the thermal-SiO2/Si interface for crystalline Si solar cells. Appl Surf Sci 395:56–60 Kaur G et al (2020) Improved silicon oxide/polysilicon passivated contacts for high efficiency solar cells via optimized tunnel layer annealing. Sol Energy Mater Sol Cells 217:110720 Rajendran V et al (2024) Indium tin oxide thin film preparation and property relationship for humidity sensing: A review. Eng Rep 6(3):e12836 Lu L et al (2021) Dopant diffusion through ultrathin AlOx and AlOx/SiOx tunnel layer in TOPCon structure and its impact on the passivation quality on c-Si solar cells. Sol Energy Mater Sol Cells 223:110970 Yang Z et al (2021) Charge-carrier dynamics for silicon oxide tunneling junctions mediated by local pinholes. Cell Rep Phys Sci, 2(12) Lancaster K et al (2016) Study of pinhole conductivity at passivated carrier-selected contacts of silicon solar cells. Energy Procedia 92:116–121 Acharyya S et al (2022) Performance analysis of different dielectrics for solar cells with TOPCon structure. J Comput Electron 21(2):471–490 Khokhar MQ et al (2021) Improving passivation properties using a nano-crystalline silicon oxide layer for high-efficiency TOPCon cells. Infrared Phys Technol 115:103723 Li Y et al (2004) Preferential growth of semiconducting single-walled carbon nanotubes by a plasma enhanced CVD method. Nano Lett 4(2):317–321 Feldmann F et al (2014) Tunnel oxide passivated contacts as an alternative to partial rear contacts. Sol Energy Mater Sol Cells 131:46–50 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 23 Feb, 2026 Read the published version in Silicon → Version 1 posted Editorial decision: Revision requested 09 Jun, 2025 Reviews received at journal 23 May, 2025 Reviews received at journal 23 May, 2025 Reviews received at journal 21 May, 2025 Reviews received at journal 19 May, 2025 Reviewers agreed at journal 14 May, 2025 Reviewers agreed at journal 14 May, 2025 Reviewers agreed at journal 14 May, 2025 Reviewers agreed at journal 14 May, 2025 Reviewers agreed at journal 14 May, 2025 Reviewers invited by journal 14 May, 2025 Editor assigned by journal 06 Apr, 2025 Submission checks completed at journal 06 Apr, 2025 First submitted to journal 13 Mar, 2025 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-6217606","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":456428495,"identity":"0515f4c6-6b8e-48f4-84b9-28c0e96eb5fb","order_by":0,"name":"Rabia 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cells\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6217606/v1/8f369b775f09a3b6e7900542.png"},{"id":82894042,"identity":"ec459d29-242d-4b45-b1e1-ec17cbeb0f05","added_by":"auto","created_at":"2025-05-16 12:32:18","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":160775,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of AZO thickness and doping concentration on the performance of TOPCon solar cells\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6217606/v1/8b37a1f095e4574ada390d64.png"},{"id":82895207,"identity":"9ef5d5f1-150a-4b4f-99d3-949f984872f2","added_by":"auto","created_at":"2025-05-16 12:40:18","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":156090,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of the ZnO thickness and doping concentration on the performance of TOPCon solar cells\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6217606/v1/22f5e0312aaaf0d77d360062.png"},{"id":82894038,"identity":"698edfd2-3b2d-4dc2-a46d-4df5caf5bd96","added_by":"auto","created_at":"2025-05-16 12:32:18","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":168770,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of the ITO thickness and doping concentration on the performance TOPCon solar cells\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6217606/v1/90b6a9018f88899621f14a66.png"},{"id":82894059,"identity":"8fcf6a44-e45c-4296-81d7-13faa5f271cf","added_by":"auto","created_at":"2025-05-16 12:32:19","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":168762,"visible":true,"origin":"","legend":"\u003cp\u003eShows the effect of different tunneling oxide layer’s thickness with FTO as TCO on TOPCon SC parameters (a) V\u003csub\u003eoc\u003c/sub\u003e, (b) J\u003csub\u003esc\u003c/sub\u003e, (c) FF, and (d) PCE\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-6217606/v1/9234b77eae674d4a61ccb3e9.png"},{"id":82895209,"identity":"0145ab6e-9be7-42cc-ba14-6be8fece6df0","added_by":"auto","created_at":"2025-05-16 12:40:19","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":171262,"visible":true,"origin":"","legend":"\u003cp\u003eShows the effect of different tunneling oxide layer’s thickness with AZO as TCO on TOPCon SC parameters (a) V\u003csub\u003eoc\u003c/sub\u003e, (b) J\u003csub\u003esc\u003c/sub\u003e, (c) FF, and (d) PCE\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-6217606/v1/94a886a7c764f59463a369da.png"},{"id":82894045,"identity":"89cb0bfc-2624-428d-9f95-102fb6365164","added_by":"auto","created_at":"2025-05-16 12:32:19","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":166434,"visible":true,"origin":"","legend":"\u003cp\u003eShows the effect of different tunneling oxide layer’s thickness with ZnO as TCO on TOPCon SC parameters (a) V\u003csub\u003eoc\u003c/sub\u003e, (b) J\u003csub\u003esc\u003c/sub\u003e, (c) FF, and (d) PCE\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-6217606/v1/bf3e06559e8031da57c51f27.png"},{"id":82895213,"identity":"306a7a37-c0e9-49c2-82eb-68ec04683e9d","added_by":"auto","created_at":"2025-05-16 12:40:19","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":181833,"visible":true,"origin":"","legend":"\u003cp\u003eShows the effect of different tunneling oxide layer’s thickness with ITO as TCO on TOPCon SC parameters (a) V\u003csub\u003eoc\u003c/sub\u003e, (b) J\u003csub\u003esc\u003c/sub\u003e, (c) FF, and (d) PCE\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-6217606/v1/6fbc5e8b5bfdeaf7156bce8e.png"},{"id":82895521,"identity":"6be31caf-ff51-486a-8af0-a59c4cfb9484","added_by":"auto","created_at":"2025-05-16 12:48:19","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":130250,"visible":true,"origin":"","legend":"\u003cp\u003eShows the effect of pinhole density on TOPCon SC performance (a)V\u003csub\u003eoc\u003c/sub\u003e, (b)J\u003csub\u003esc\u003c/sub\u003e, (c) FF, and (d) PCE with different tunneling oxide layers and FTO used as TCO layer\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-6217606/v1/fbaa24b8dff66efc482bab6c.png"},{"id":82894056,"identity":"4cfe4454-a9cf-49d1-81db-e80f43e1ac26","added_by":"auto","created_at":"2025-05-16 12:32:19","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":123145,"visible":true,"origin":"","legend":"\u003cp\u003eShows the effect of pinhole density on TOPCon SC performance (a)V\u003csub\u003eoc\u003c/sub\u003e, (b)J\u003csub\u003esc\u003c/sub\u003e, (c) FF, and (d) PCE with different tunneling oxide layers and AZO used as TCO\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-6217606/v1/a59e5df4ca81b1cb15610ed6.png"},{"id":82894048,"identity":"93b5d0ee-8e6e-4c67-94ce-b95deb5b93f4","added_by":"auto","created_at":"2025-05-16 12:32:19","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":128705,"visible":true,"origin":"","legend":"\u003cp\u003eShows the effect of pinhole density on TOPCon SC performance (a)V\u003csub\u003eoc\u003c/sub\u003e, (b)J\u003csub\u003esc\u003c/sub\u003e, (c) FF, and (d) PCE with different tunneling oxide layers and ZnO \u0026nbsp;used as TCO\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-6217606/v1/21341f14fadd344db8088490.png"},{"id":82894050,"identity":"5b36ff9a-c261-4de5-95da-c8173539b41f","added_by":"auto","created_at":"2025-05-16 12:32:19","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":156667,"visible":true,"origin":"","legend":"\u003cp\u003eShows the effect of pinhole density on TOPCon SC performance (a)V\u003csub\u003eoc\u003c/sub\u003e, (b)J\u003csub\u003esc\u003c/sub\u003e, (c) FF, and (d) PCE with different tunneling oxide layers and ITO used as TCO\u003c/p\u003e","description":"","filename":"12.png","url":"https://assets-eu.researchsquare.com/files/rs-6217606/v1/17478aecce0c684a672c23fb.png"},{"id":82894054,"identity":"ca201fe0-27d2-48b6-a8db-60aa5ed8e79d","added_by":"auto","created_at":"2025-05-16 12:32:19","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":118828,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of interface trap density of different tunneling oxide layers with FTO used as TCO on TOPCon SC performance shows (a)Voc, (b)J\u003csub\u003esc\u003c/sub\u003e, (c) FF, and (d) PCE\u003c/p\u003e","description":"","filename":"13.png","url":"https://assets-eu.researchsquare.com/files/rs-6217606/v1/897e590ca4022a128cdd9385.png"},{"id":82894076,"identity":"7bada5d7-ac07-47cf-97fa-f8303163a6e4","added_by":"auto","created_at":"2025-05-16 12:32:19","extension":"png","order_by":14,"title":"Figure 14","display":"","copyAsset":false,"role":"figure","size":132322,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of interface trap density of different tunneling oxide layers with AZO used as TCO on TOPCon SC performance shows (a)Voc, (b)J\u003csub\u003esc\u003c/sub\u003e, (c) FF, and (d) PCE\u003c/p\u003e","description":"","filename":"14.png","url":"https://assets-eu.researchsquare.com/files/rs-6217606/v1/2430a6f5ef7b7fd502b1f475.png"},{"id":82895218,"identity":"a914452f-c653-43f9-ad2e-9e6d7a6adfe7","added_by":"auto","created_at":"2025-05-16 12:40:19","extension":"png","order_by":15,"title":"Figure 15","display":"","copyAsset":false,"role":"figure","size":139579,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of interface trap density of different tunneling oxide layers with ZnO used as TCO on TOPCon SC performance shows (a)Voc, (b)J\u003csub\u003esc\u003c/sub\u003e, (c) FF, and (d) PCE\u003c/p\u003e","description":"","filename":"15.png","url":"https://assets-eu.researchsquare.com/files/rs-6217606/v1/7f4b6cb37b69a52d068ecddb.png"},{"id":82895229,"identity":"14ed57a9-c4c8-45ad-a26b-ed807ef61c9f","added_by":"auto","created_at":"2025-05-16 12:40:20","extension":"png","order_by":16,"title":"Figure 16","display":"","copyAsset":false,"role":"figure","size":145243,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of interface trap density of different tunneling oxide layers with ITO used as TCO on TOPCon SC performance shows (a)Voc, (b)J\u003csub\u003esc\u003c/sub\u003e, (c) FF, and (d) PCE\u003c/p\u003e","description":"","filename":"16.png","url":"https://assets-eu.researchsquare.com/files/rs-6217606/v1/2e58146da6b2aaf06259d76c.png"},{"id":82894084,"identity":"7dd5ee27-30ed-4c0a-947f-147fb1287759","added_by":"auto","created_at":"2025-05-16 12:32:20","extension":"png","order_by":17,"title":"Figure 17","display":"","copyAsset":false,"role":"figure","size":127786,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of minority carrier life time in p-type silicon wafer with different tunneling oxide layers and FTO used as TCO on TOPCon SC performance shows (a)Voc, (b)J\u003csub\u003esc\u003c/sub\u003e, (c) FF, and (d) PCE \u0026nbsp;\u003c/p\u003e","description":"","filename":"17.png","url":"https://assets-eu.researchsquare.com/files/rs-6217606/v1/e65ba8aca2f7d62993bd26c1.png"},{"id":82895523,"identity":"4fc27995-6fb1-43f9-81ed-4775e7502a62","added_by":"auto","created_at":"2025-05-16 12:48:19","extension":"png","order_by":18,"title":"Figure 18","display":"","copyAsset":false,"role":"figure","size":137305,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of minority carrier life time in p-type silicon wafer with different tunneling oxide layers and AZO used as TCO on TOPCon SC performance shows (a)Voc, (b)J\u003csub\u003esc\u003c/sub\u003e, (c) FF, and (d) PCE\u003c/p\u003e","description":"","filename":"18.png","url":"https://assets-eu.researchsquare.com/files/rs-6217606/v1/90710dd4a777ffb54e906bf4.png"},{"id":82895221,"identity":"7ded223e-8e6e-46c8-92ce-6d0e670d71a4","added_by":"auto","created_at":"2025-05-16 12:40:19","extension":"png","order_by":19,"title":"Figure 19","display":"","copyAsset":false,"role":"figure","size":144266,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of minority carrier life time in p-type silicon wafer with different tunneling oxide layers and ZnO used as TCO on TOPCon SC performance shows (a)Voc, (b)J\u003csub\u003esc\u003c/sub\u003e, (c) FF, and (d) PCE\u003c/p\u003e","description":"","filename":"19.png","url":"https://assets-eu.researchsquare.com/files/rs-6217606/v1/07fe6f24092fdb9d5b0b2f4d.png"},{"id":82895233,"identity":"d76b68d1-e9bf-47ec-a50b-fc02b20960c8","added_by":"auto","created_at":"2025-05-16 12:40:20","extension":"png","order_by":20,"title":"Figure 20","display":"","copyAsset":false,"role":"figure","size":148105,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of minority carrier life time in p-type silicon wafer with different tunneling oxide layers and ITO used as TCO on TOPCon SC performance shows (a)Voc, (b)J\u003csub\u003esc\u003c/sub\u003e, (c) FF, and (d) PCE\u003c/p\u003e","description":"","filename":"20.png","url":"https://assets-eu.researchsquare.com/files/rs-6217606/v1/dae2e6adf4aae23ffc6f7605.png"},{"id":82894082,"identity":"b1916789-9153-4447-8d16-65dbe46811a8","added_by":"auto","created_at":"2025-05-16 12:32:20","extension":"png","order_by":21,"title":"Figure 21","display":"","copyAsset":false,"role":"figure","size":143806,"visible":true,"origin":"","legend":"\u003cp\u003e(A) EQE Curve and (B) J-V curve of the final TOPCon solar cell\u003c/p\u003e","description":"","filename":"21.png","url":"https://assets-eu.researchsquare.com/files/rs-6217606/v1/5f0d13e8bcc63ac250c957d7.png"},{"id":103765539,"identity":"9133a94a-4792-4f8d-b094-5d6b8aa0479c","added_by":"auto","created_at":"2026-03-02 16:03:41","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3500238,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6217606/v1/9bb6546d-f40e-40f3-b7e8-6decf67f439f.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Investigating the influence of TCOs and tunneling dielectric layers on TOPCon solar cell performance","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003ePhotovoltaic energy generation is an environment friendly source of renewable energy production worldwide. Crystalline silicon (c-Si) is copious in the nature, cost-effective and highly efficient, making it a commonly used material for solar cell production. Currently, crystalline silicon solar cells account for over 95% of total photovoltaic production and become indispensable in photovoltaic (PV) industry [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. The continuous advancements in c-Si photovoltaic technology are primarily driven by innovative approaches aimed at reducing costs and improving performance. Among these, tunnel oxide passivated contact (TOPCon) structure, utilizing doped polysilicon (poly-Si) junctions; have emerged as a particularly promising practical concept. The TOPCon structure has garnered significant attention for its ability to simultaneously passivate surfaces and facilitate carrier collection. This technology helps to prevent the undesired recombination that produce at direct metal/silicon interface of both at front/rear sides of PERC solar cells (SC). It uses a technique called passivating contact [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Crystalline silicon solar cells that are passivated with tunnel oxide contacts utilize tunnel oxide on the rear side to reduce the recombination rate [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. At rear passivated contact side, TOPCon solar cell uses tunnel oxide layer of 1 nm thick that is a dynamic layer of the TOPCon solar cells. Foremost role of oxide tunneling is to give effective passivation in solar cell. An ultrathin SiO\u003csub\u003ex\u003c/sub\u003e layers were generally used as a carrier selective tunneling layers due of its good passivation abilities [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Al₂O₃ as the tunneling layer, also serves as a common alternative to SiOₓ in TOPCon solar cells owing its superior dielectric properties [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Using an extremely thin Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e layer as hole-selective tunnel layer on the \u003cem\u003ep-\u003c/em\u003eTOPCon solar cells has shown better outcomes, by maximizing the efficiency to about 21.16% as well as showing less contact resistance of the 1.84 mΩ\u0026sdot;cm\u003csup\u003e2\u003c/sup\u003e [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Various techniques, such as plasma-assisted oxidation, thermal oxidation, ozone oxidation, atomic layer deposition (ALD), and wet-chemical oxidation, can be used to deposit an excellent ultrathin oxide layer [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. The fixed charge of the oxide significantly influences the surface recombination velocity (SRV), thus is essential to carefully select oxide for the passivation layer [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Additionally, fixed charge affects cell's efficiency in circumstances of suitable bulk doping type, large bulk lifetime and the resistivity. Therefore, it is important to choose the appropriate tunnel oxide dielectric material and its optimized thickness. This selection of an appropriate tunnel oxide layer for the use along with the \u003cem\u003ep\u003c/em\u003e-TOPCon is significant in preventing recombination under maximum power point conditions, and this phenomenon is particularly important for TOPCon [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Recombination is loss of the charge carriers contributed to current or the voltage generated by solar cell. Recombination primarily occurs in surface and the bulk regions, and recombination current can possibly be reduced by passivating the rear side contact. To collect all photo-generated carriers, it is necessary to minimize surface and bulk recombination that can occur within the diffusion length [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. In order to enhance commercial solar cells further, minimizing surface recombination losses is essential. Without the presence of light, emitter recombination current exceeds the base recombination current owing to the effects of energy bandgap narrowing, Auger recombination and elevated defect density in bulk region.\u003c/p\u003e \u003cp\u003eField effect surface passivation and interface density optimization are techniques that minimize charge of one carrier type via employing fixed value of the charge of the other type [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. The effective mass of tunnelling oxide layer, dielectric constant, and the barrier heights of tunnel oxide passivated contacts are significant factors controlling the bulk and the lesser carrier tunnel currents in back side for both electrons and holes. Previous research has indicated a drift in silicon dioxide (SiO\u003csub\u003e2\u003c/sub\u003e) tunnel layer thickness both the \u003cem\u003ep\u003c/em\u003e/\u003cem\u003en\u003c/em\u003e-type bulk, showing that tunnel oxide thicknesses must be less the 2 nm for both \u003cem\u003ep\u003c/em\u003e/\u003cem\u003en\u003c/em\u003e-type cells, respectively [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Limited research has been conducted to assess cell working efficiency alongside tunnel oxide layer thickness with impact of the various transparent conducting oxides [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Therefore, research on replacing SiO₂ with alternative materials is essential to enhance cell efficiency and to better understand the impact of different tunnel oxide on PCE of solar cell. A significant number of endeavors have concentrated on TOPCon solar cells made of n-type Si substrates; however certain experiments conducted on specific p-type Si substrates. It is believed p-type Silicon are currently dominant in Silicon solar cell industry[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Investigating the integration of the poly-Silicon passivated layer contacts with p-type Silicon substrate is crucial for commercializing this technology and research based on \u003cem\u003ep\u003c/em\u003e-TOPCon solar cells [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Systematic numerical investigation is essential for more thorough understanding of crucial parameters which impact device functionality, such as doping concentration, thickness of oxide layer, n-Silicon layer feature, interface quality additionally the recombination parameters. Steinkemper \u003cem\u003eet al.\u003c/em\u003e, presented a good illustration of how to analyse performance of TOPCon solar cells through numerical simulation, using two various n-Si materials such as (polycrystalline and the amorphous silicon) [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Their attention was directed toward carrier-selective electron connections based on tunnel oxides and emphasized the types of the materials and structures that are effective for TOPCon solar cells.\u003c/p\u003e \u003cp\u003eThe present study investigates the efficiency evaluations of TOPCon solar cells via changing dielectric materials, such as SiO\u003csub\u003e2\u003c/sub\u003e, Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, TiO\u003csub\u003e2\u003c/sub\u003e, ZrO\u003csub\u003e2\u003c/sub\u003e, and the HfO\u003csub\u003e2\u003c/sub\u003e, as well as transparent conductive oxides of FTO, ZnO, AZO and ITO at the front side. These materials are the potential passivation candidates for TOPCon solar cells and are analysed by AFORS-HET (Automat for the Simulation of Hetero structures) [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. Key distinction about this work is consideration and examination of the comprehensive parameters affecting device working performance, including factors like doping concentration, oxide thickness, carrier transport, pinhole density, trap density in oxide layer and the carrier lifetime. In conclusion, our study contributes to elucidating constrictions and challenges associated with prime parameters and will provide valuable understandings for advance development of the high-performance solar cells with tunnel oxide passivated contacts.\u003c/p\u003e"},{"header":"2. Modeling and the simulation setup","content":"\u003cp\u003eThe AFORS-HET V.2.5, HZB (Hahn-Meitner-Institute Berlin) has been developed as powerful and flexible numerical software for heterojunction configuration. [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. In this study, we extensively analysed solar cells structure by incorporating tunnel oxide passivated contact structure. TOPCon solar cell configuration employed within this study given as follows: front electrode/front pyramid-textured TCOs/\u003cem\u003en\u003c/em\u003e\u003csup\u003e+\u003c/sup\u003e-Si/\u003cem\u003ep\u003c/em\u003e-Si/tunnelling oxide layer/\u003cem\u003ep\u003c/em\u003e\u003csup\u003e+\u003c/sup\u003e-Si/rear side electrode. We described carrier transport from the dielectric tunnel oxide via considering thermionic emission with the help of thermionic field model as well as tunneling model. Optical absorption was explained through multiple reflections and coherence model.\u003c/p\u003e \u003cp\u003eFor electrical layers and the optical layers default parameters are commonly referenced in published research [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Here are the various parameters: t for thickness, Chi for electron affinity energy, SRV for surface recombination velocity, d\u003csub\u003ek\u003c/sub\u003e for relative dielectric constant, Na for acceptor concentration, N\u003csub\u003ed\u003c/sub\u003e for donor concentration, E\u003csub\u003eg\u003c/sub\u003e for band gap, m\u003csub\u003ee ​\u003c/sub\u003erepresents the relative effective mass of the electron, while m\u003csub\u003eh\u003c/sub\u003e denotes the relative effective mass of the hole,D\u003csub\u003eph\u003c/sub\u003e pin hole density through the insulator layer (dimensionless). AFORS-HET, despite being 1-dimensional simulation software, can handle pinholes. In oxide film, pinholes are micro holes that act as leak channels for most carriers. Several research reports have been published in presence of the pinholes in ultrathin SiO\u003csub\u003ex\u003c/sub\u003e tunnel layer at different times [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e], [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Through the pinholes, substantial fraction of carriers would be leak from the dielectric thin layer. However if pinholes are spread in a 2D dielectric, fraction of leaked carriers can be integrated. Therefore, leaked carrier percentage could be addressed as a 1D circumstance. Simulated cell structure is graphically represented in Fig.\u0026nbsp;\u003cspan refid=\"Fig21\" class=\"InternalRef\"\u003e21\u003c/span\u003e, and Tables\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and \u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e presented the set parameters.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eParameters for the device simulation\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDesigned structure layers\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eOptimized parameter\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003et\u0026thinsp;=\u0026thinsp;1\u0026nbsp;\u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e\u0026nbsp;m\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSiN\u003csub\u003ex\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003et\u0026thinsp;=\u0026thinsp;75 nm\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTCO (FTO, AZO, ZnO, ITO)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003et=(60,60,30,75) nm\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFront contact boundary\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ew/o the absorption loss, standard texture surface (54.74\u0026deg;), flat band\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFront metal contact\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMS Schottky contact model, S\u003csub\u003ep\u003c/sub\u003e=10\u003csup\u003e6\u003c/sup\u003e\u0026nbsp;cms\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e ,S\u003csub\u003en\u003c/sub\u003e=10\u003csup\u003e6\u003c/sup\u003e\u0026nbsp;cms\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003en\u003c/em\u003e-type silicon emitter layer\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003et\u0026thinsp;=\u0026thinsp;0.1\u0026micro;m, dk\u0026thinsp;=\u0026thinsp;11.9,N\u003csub\u003ed\u003c/sub\u003e=3\u0026times;\u0026nbsp;10\u003csup\u003e18\u003c/sup\u003e cm\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e, N\u003csub\u003ea\u003c/sub\u003e =0\u0026nbsp;cm\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e ,chi\u0026thinsp;=\u0026thinsp;4.09eV,N\u003csub\u003ec\u003c/sub\u003e=1.23\u0026times;\u0026nbsp;10\u003csup\u003e19\u003c/sup\u003ecm\u003csup\u003e\u0026minus;3\u003c/sup\u003e,E\u003csub\u003eg\u003c/sub\u003e=1.08eV, \u0026micro;\u003csub\u003en\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;185.5cm\u003csup\u003e2\u003c/sup\u003e\u0026nbsp;V\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u0026nbsp;s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e,\u0026micro;\u003csub\u003ep\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;169.2cm\u003csup\u003e2\u003c/sup\u003e\u0026nbsp;V\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u0026nbsp;s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e,V\u003csub\u003ee\u003c/sub\u003e=1\u0026times;10\u003csup\u003e7\u003c/sup\u003ecms\u003csup\u003e\u0026minus;1\u003c/sup\u003e, rho\u0026thinsp;=\u0026thinsp;2.4g, N\u003csub\u003ev\u003c/sub\u003e=1.17\u0026times;\u0026nbsp;10\u003csup\u003e19\u003c/sup\u003e cm\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e ,V\u003csub\u003eh\u003c/sub\u003e=1\u0026times;10\u003csup\u003e7\u003c/sup\u003ecms\u003csup\u003e\u0026minus;1\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e-type silicon wafer layer\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003et\u0026thinsp;=\u0026thinsp;150 \u0026micro;m, dk\u0026thinsp;=\u0026thinsp;11.9, N\u003csub\u003ed\u003c/sub\u003e=0\u0026nbsp;cm\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e,Na\u0026thinsp;=\u0026thinsp;1.5\u0026times;\u0026nbsp;10\u003csup\u003e17\u003c/sup\u003e cm\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e, chi\u0026thinsp;=\u0026thinsp;4.05eV,N\u003csub\u003ec\u003c/sub\u003e=2.8\u0026times;\u0026nbsp;10\u003csup\u003e19\u003c/sup\u003ecm\u003csup\u003e\u0026minus;3\u003c/sup\u003e,E\u003csub\u003eg\u003c/sub\u003e=1.123eV, ,\u0026micro;\u003csub\u003en\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;594.6cm\u003csup\u003e2\u003c/sup\u003e\u0026nbsp;V\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u0026nbsp;s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e,\u0026micro;\u003csub\u003ep\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;296.8 cm\u003csup\u003e2\u003c/sup\u003e\u0026nbsp;V\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u0026nbsp;s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e,V\u003csub\u003ee\u003c/sub\u003e=1\u0026times;10\u003csup\u003e7\u003c/sup\u003e cms\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, rho\u0026thinsp;=\u0026thinsp;2.4g ,V\u003csub\u003eh\u003c/sub\u003e=1\u0026times;10\u003csup\u003e7\u003c/sup\u003e cm s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e ,N\u003csub\u003ev\u003c/sub\u003e=2.6\u0026times;\u0026nbsp;10\u003csup\u003e19\u003c/sup\u003ecm\u003csup\u003e\u0026minus;3\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBack contact\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMS Schottky contact model, S\u003csub\u003ep\u003c/sub\u003e=10\u003csup\u003e6\u003c/sup\u003e\u0026nbsp;cms\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003eS\u003csub\u003en\u003c/sub\u003e=10\u003csup\u003e6\u003c/sup\u003e\u0026nbsp;cms\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRear contact boundary\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ew/o the absorption loss, Plane surface, flat band\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAg electrode\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003et\u0026thinsp;=\u0026thinsp;1\u0026nbsp;\u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e m\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eTunneling properties for the various dielectric layers\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSiO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eAl\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHfO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eZrO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eTiO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eElectron tunneling mass(m\u003csub\u003ee\u0026minus;ox\u003c/sub\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.41m\u003csub\u003eo\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.40 m\u003csub\u003eo\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.11m\u003csub\u003eo\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.28 m\u003csub\u003eo\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e10 m\u003csub\u003eo\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHole tunneling mass(m\u003csub\u003eh\u0026minus;ox\u003c/sub\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.32 m\u003csub\u003ee\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.35 m\u003csub\u003ee\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.29 m\u003csub\u003ee\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.28 m\u003csub\u003ee\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.81 m\u003csub\u003ee\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBand-gap(E\u003csub\u003eg\u003c/sub\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e9.00 eV\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.50 eV\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5.80 eV\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e5.70 eV\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3.2 eV\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eElectron Affinity (χ)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.90 eV\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.15 eV\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.04 eV\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.65 eV\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.58 eV\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFixed charge(dielectric/Si interface\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u0026thinsp;1\u0026times;10\u003csup\u003e12\u003c/sup\u003e cm\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-1\u0026times;10\u003csup\u003e13\u003c/sup\u003ecm\u003csup\u003e\u0026minus;3\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e+\u0026thinsp;2\u0026times;10\u003csup\u003e12\u003c/sup\u003ecm\u003csup\u003e\u0026minus;3\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-1\u0026times;10\u003csup\u003e11\u003c/sup\u003ecm\u003csup\u003e\u0026minus;3\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-5\u0026times;10\u003csup\u003e8\u003c/sup\u003e cm\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e"},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n \u003ch2\u003e3.1 Optimization of TCO\u0026rsquo;s thickness and the doping concentration\u003c/h2\u003e\n \u003cp\u003eIn the present work, carrier lifetime, pinhole density and interface trap density (D\u003csub\u003eit\u003c/sub\u003e) deviation curves and the corresponding output parameters of TOPCon solar cell are illustrated. Initially, we modeled changes in cell working performance by varying thickness of the TCOs, and the results are shown in Figs. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e, \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e, \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e, and \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e. We selected the optimized thickness value for various TCOs and then doping concentration was varied from 10\u003csup\u003e15\u003c/sup\u003e to 10\u003csup\u003e20\u003c/sup\u003e cm\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e. The efficiency obtained was 24.22% at the 8\u0026times;10\u003csup\u003e20\u003c/sup\u003e cm\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e for the FTO, 24.32% at the 8\u0026times;10\u003csup\u003e20\u003c/sup\u003e cm\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e for the AZO, 25.49% at the 7\u0026times;10\u003csup\u003e20\u003c/sup\u003e cm\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e for the ZnO, and 25.56% at the 7\u0026times;10\u003csup\u003e20\u003c/sup\u003e cm\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e for ITO doping concentrations. The doping concentration significantly affected the efficiency of whole cell and maximum efficiency was achieved at high doping density. Indium tin oxide transparency is directly onto the silicon wafer, and transparent conductive oxide film at the front acts as an antireflection coating. Indium tin oxide (ITO) appeared as the better choice for the TCO materials due to its maximum transmission rate of above 80%, superior conductivity of 10\u003csup\u003e4\u003c/sup\u003e Ω\u003csup\u003e\u0026minus;1\u003c/sup\u003e cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, low refractive index, low light absorption and high stability [\u003cspan class=\"CitationRef\"\u003e22\u003c/span\u003e]. Reverse saturation current decreases when the doping concentration increases from reasonably minimum value of 10\u003csup\u003e15\u003c/sup\u003e cm\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e,resulting in a rise in open circuit voltage then eventually a rise in conversion efficiency.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n \u003ch2\u003e3.2 Optimization of tunnel oxide layer\u0026rsquo;s thickness in TOPCon solar cell\u003c/h2\u003e\n \u003cp\u003eThe main focus of this work is on various tunneling oxide layers in combination with different TCOs that are utilized to optimize cell performance. We simulated TOPCon solar cells by using different TCOs with tunneling oxide layers of SiO\u003csub\u003e2\u003c/sub\u003e, Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, HfO\u003csub\u003e2\u003c/sub\u003e, ZrO\u003csub\u003e2\u003c/sub\u003e and TiO\u003csub\u003e2\u003c/sub\u003e. The oxide layer is an important part of TOPCon structure, as it can passivate dangling bonds on the surface of c-Silicon, thus reducing trap density. It is crucial to precisely control thickness of oxide layer to ensure proper tunneling effects. It is important to note that increasing tunnel oxide layer thickness will decrease tunneling efficiency. According to an insulator tunneling concept [\u003cspan class=\"CitationRef\"\u003e23\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e24\u003c/span\u003e] equation for tunneling current is given as:\u003c/p\u003e\n \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u0026nbsp;\u003cspan class=\"mathinline\"\u003e\\(\\:{\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\varvec{J}}_{\\varvec{t}\\varvec{u}\\varvec{n}\\varvec{n}\\varvec{e}\\varvec{l}}=\\frac{\\varvec{q}{\\varvec{n}}_{\\varvec{i}\\varvec{o}}^{2}{\\varvec{v}}_{\\varvec{t}\\varvec{h}}}{{\\varvec{N}}_{\\varvec{e}\\varvec{f}\\varvec{f}}}\\)\u003c/span\u003e\u0026nbsp;\u003c/span\u003e \u003cstrong\u003ee -\u003c/strong\u003e \u003cspan class=\"InlineEquation\"\u003e\u0026nbsp;\u003cspan class=\"mathinline\"\u003e\\(\\:\\:\\frac{2{\\varvec{t}}_{\\varvec{o}\\varvec{x}}}{\\varvec{ħ}}\\sqrt{2\\varvec{q}{\\varvec{m}}_{\\varvec{e}\\varvec{f}\\varvec{f},\\varvec{o}\\varvec{x}{\\varvec{\\varPhi\\:}}_{\\varvec{o}\\varvec{x}}}}\\)\u003c/span\u003e\u0026nbsp;\u003c/span\u003e \u003cstrong\u003e=\u003c/strong\u003e \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\frac{\\varvec{q}{\\varvec{n}}_{\\varvec{i}\\varvec{o}}^{2}{\\varvec{v}}_{\\varvec{t}\\varvec{h}}}{{\\varvec{N}}_{\\varvec{e}\\varvec{f}\\varvec{f}}}\\)\u003c/span\u003e\u003c/span\u003e \u003cstrong\u003e=\u003c/strong\u003e \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\varvec{P}}_{\\varvec{t}\\varvec{u}\\varvec{n}\\varvec{n}\\varvec{e}\\varvec{l}}\\)\u003c/span\u003e\u003c/span\u003e \u003cstrong\u003e(1\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003eHere the J\u003csub\u003etunnel\u003c/sub\u003e refers to the oxide tunneling current density, while n\u003csub\u003eio\u003c/sub\u003e denotes the charge carrier density in the intrinsic silicon, q represents the electronic charge, and V\u003csub\u003e\u003cem\u003eth\u003c/em\u003e\u003c/sub\u003e indicates the thermal velocity of charge carriers holes for p-type and electrons for n-type materials, N\u003csub\u003e\u003cem\u003eeff\u003c/em\u003e\u003c/sub\u003e is the effective charge carrier density, and m\u003csub\u003eeff,ox\u003c/sub\u003e stands for the effective mass of charge carriers in the oxide, specifically for holes in the case of hole tunneling and electrons in the case of electron tunneling, \u0026Phi;\u003csub\u003eOx\u003c/sub\u003e refers to the barrier height for the oxide, which varies depending on whether holes or electrons are the charge carriers, with the barrier height at the valence band for holes and at the conduction band for electrons ,t\u003csub\u003eox\u003c/sub\u003e represents the thickness of the oxide and P\u003csub\u003etunnel\u003c/sub\u003e is the tunnelling probability.\u003c/p\u003e\n \u003cp\u003eEquation (1) clearly indicates the reducing the thickness of the insulator leads to an increase in tunnelling probability thus, higher tunnelling current. Meanwhile the insulator layer thickness is of minimum nanometres, thickness of tunnel oxide is changed from the range of 0.3 nm to the 2 nm to evaluate working efficiency corresponding to each tunnel oxide thickness. Initially, efficiency increases gradually, but as thickness of the tunnel layer increases, efficiency steadily reduces. The results are given in Figs. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e, \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e, \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e and \u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e. The conversion efficiency looks likely to decrease as a result of reduced current flow at 1.3 to 1.5 nm, giving maximum results. The current density, which directly impacts efficiency, is examined in relation to the oxide thickness. As thickness steadily rises, number of the charge carriers tunneling through interface layer also rises, leading to a rise in J\u003csub\u003esc\u003c/sub\u003e (short-circuit current). However, further increases in oxide layer thickness can result in deficient diffusion length of the carriers tunneling through the oxide, leading to increased recombination and a decrease in J\u003csub\u003esc\u003c/sub\u003e. Interestingly, the fill factor (FF) is initially maximum but falls steadily as the oxide thickness increases.\u003c/p\u003e\n \u003cp\u003eTransparent conducting oxides (TCOs) are the semiconductors with wide bandgap (Eg) of 3.1 eV. Their properties are strongly influenced by deviations in stoichiometry, like oxygen deficit, the type and amount of the impurities present in host lattice.\u003c/p\u003e\n \u003cp\u003eThe characteristics of the tunnel dielectric materials containing tunnel masses, relative permittivity, the barrier height for the electrons/holes, and the fixed charge specific to every material. Solar cell performance is not well-known, particularly regarding thickness, doping concentration and the carrier lifetime etc. and thus being analyzed using numerical model by adjusting the properties and the tunnel dielectric thickness of every material. A novel understanding into the use of conventional tunnel oxide dielectric materials such as SiO\u003csub\u003e2\u003c/sub\u003e, ZrO\u003csub\u003e2\u003c/sub\u003e, and Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, as well as potential materials like TiO\u003csub\u003e2\u003c/sub\u003e, HfO\u003csub\u003e2\u0026nbsp;\u003c/sub\u003eand the TiO\u003csub\u003e2\u003c/sub\u003e is provided in the study. It also showed that the maximum dielectric tunnel oxide thickness for all materials can be calculated by effective mass of the majority charge carrier. Additionally, fixed charge influences the overall solar cell PCE under the settings of the maximum carrier lifetime, the suitable bulk doping density and the resistivity. Therefore, an optimization study is made for the selection of an appropriate tunnel oxide dielectric material.\u003c/p\u003e\n \u003cp\u003eThe TOPCon solar cell PCE was increased to 26.16 % by with Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e tunnel oxide layer as rear side tunnel passivation in cell structure. This enhancement is attributed to negative fixed charges in AlO\u003csub\u003ex\u003c/sub\u003e tunnel oxide, which provide further field-effective passivation by attracting holes to part near to the interface between the dielectric and c-Silicon. So, extraordinary quality passivation can be estimated while using the AlO\u003csub\u003ex\u0026nbsp;\u003c/sub\u003elayer [27]. However a poor performance of TiO\u003csub\u003e2\u0026nbsp;\u003c/sub\u003ecan be attributed to a negative electron barrier at Si/TiO\u003csub\u003e2\u003c/sub\u003e interface, which hinders its function as a carrier selective contact. This results in a weakened back surface field effect on the thin silicon film, thereby degrading the cell efficiency. Among other materials, maximum performances are nearly identical, excluding for point where the fill factor drops, determined by tunnel barrier thickness. The TOPCon structure using HfO\u003csub\u003e2\u003c/sub\u003e demonstrates good performance at greater thickness due to its lesser band offset as compared to SiO\u003csub\u003e2\u003c/sub\u003e and ZrO\u003csub\u003e2\u003c/sub\u003e providing further transport channels through the insulating ultrathin oxide layer.\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e3.3: Effect of pinhole density and interface trap density through tunneling oxide layer\u003c/strong\u003e\u003c/p\u003e\u0026nbsp;It is observed that some pinholes exist in ultrathin oxide layer of TOPCon structure. In order to assess the influence of the tunnel oxide quality on total interface states and surface passivation, the pinhole density of the dielectric layer (D\u003csub\u003eph\u003c/sub\u003e) established in tunnel oxide layer was analyzed. Generation of pinholes in tunnel oxide is linked with oxidation method. In non-ideal silicon substrate, a higher number of the dislocation defects with the maximum diffusion coefficients accrue in dislocation sites that result\u0026nbsp;in the formation of oxide pinholes. Additionally, rapid heating and cooling induce tensile and compressive stress, resulting in a large number of the pinholes in the SiO\u003csub\u003ex\u003c/sub\u003e tunnel layer and has a significantly lesser thermal expansion coefficient than bulk Si-doped poly-Silicon layer. It can be concluded that generation of the pinholes is primarily influenced by heating and cooling rate of TOPCon solar cell instead of the duration of the thermal treatment [28]. During the annealing process, impurity diffusion causes the breakdown of oxide integrity, resulting in the formation of pinholes, which are essentially microholes or microchannels through the tunnel oxide. Pinholes can lead to bulk carriers recombining and leaking at the interface, thereby reducing the efficiency of the cell [29].\n\u003c/div\u003e\n\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\n \u003cp\u003eIn TOPCon solar cells it has been reported that quantum tunnelling is not sole process for the carrier transport and transport from the pinholes does exist. It is still uncertain whether transport through the pinholes is beneficial for the solar cell efficiency.\u0026nbsp;In the case where the pinholes\u0026nbsp;are advantageous for the solar structure, we need to determine the ideal amount of carrier transport from pinholes to maximize solar cell performance. Conversely, if transport via pinholes is detrimental to the structure efficiency, we need to establish tolerance level for transport from pinholes. To address this, we carried out an extensive simulation-based investigation of\u0026nbsp;the transport of carriers in the TOPCon\u0026nbsp;solar cell and investigated performance of solar cells as the function of the pinhole carrier transport.\u003c/p\u003e\n \u003cp\u003eFigures 9, 10, 11, and 12 demonstrate the impact of pinhole density on the optimized solar cell parameters via the various TCOs and the tunneling layers after optimizing their thickness. When D\u003csub\u003eph\u003c/sub\u003e is relatively small, V\u003csub\u003eoc\u003c/sub\u003e remains constant. However, with an increase in pinhole density D\u003csub\u003eph\u003c/sub\u003e, J\u003csub\u003esc\u003c/sub\u003e decreases. As D\u003csub\u003eph\u003c/sub\u003e reaches large values; J\u003csub\u003esc\u003c/sub\u003e slightly changed and selective carrier transport is significantly affected resulting in increased leakage current. This reduction in J\u003csub\u003esc\u003c/sub\u003e ultimately leads to decreased overall efficiency [30].\u003c/p\u003e\n \u003cp\u003eDefect density is a crucial for quality of tunnel oxide and is often caused by the higher energy atom bombardment in the subsequent deposition method. In production of the TOPCon structure, various materials are essential to be processed,\u0026nbsp;Furthermore, defects at the interface may\u0026nbsp;arise. Excessive defects directly impact cell working performance, highlighting the necessity for optimizing D\u003csub\u003eit\u003c/sub\u003e.\u003c/p\u003e\n \u003cp\u003eThe interface trap density (D\u003csub\u003eit\u003c/sub\u003e) values were\u0026nbsp;integrated\u0026nbsp;into AFORS-HET simulation software, and results are detailed in Figures 13, 14, 15, and 16. The effect of oxide tunnel layer quality on surface passivation and overall cell working efficiency was examined through the characteristics of interface trap density. The figures illustrate that as the total interface trap density (D\u003csub\u003eit\u003c/sub\u003e) increased from the 1 \u0026times; 10\u003csup\u003e9\u003c/sup\u003e cm\u003csup\u003e\u0026minus;2\u003c/sup\u003e/eV to the 1 \u0026times; 10\u003csup\u003e15\u003c/sup\u003e cm\u003csup\u003e\u0026minus;2\u003c/sup\u003e/eV, both V\u003csub\u003eoc\u003c/sub\u003e and the J\u003csub\u003esc\u003c/sub\u003e of the entire cell decreased [31]. Rapid decrease in V\u003csub\u003eoc\u003c/sub\u003e with an increase of the interface trap density is attributed to rise in recombination centres in the junction area and the subsequent increase in reverse saturation current density due to the majority of carriers being captured during the tunnelling process, thus impacting the value of V\u003csub\u003eoc\u003c/sub\u003e. When D\u003csub\u003eit\u003c/sub\u003e was at its minimum, more pronounced J\u003csub\u003esc\u003c/sub\u003e, V\u003csub\u003eoc\u003c/sub\u003e, and the overall cell efficiency were attained. Figure\u0026nbsp;13, 14, 15 and 16 demonstrate that main factor influencing conversion efficiency was a V\u003csub\u003eoc\u003c/sub\u003e of 693 mV at lowest D\u003csub\u003eit\u003c/sub\u003e (1 \u0026times; 10\u003csup\u003e9\u003c/sup\u003e cm\u003csup\u003e\u0026minus;2\u003c/sup\u003e/eV), which correlated with a perfectly minimum oxide layer of the around 1.5 nm.\u003c/p\u003e\n \u003cp\u003ePassivated emitter and rear contact solar cells (PERC), back side electrode is in direct contact with back surface field, allowing carriers on back side of the cell to pass through tunnelling mechanism in passivated contact to the AlO\u003csub\u003ex\u003c/sub\u003e layer. The tunnelling oxide, with a minimal D\u003csub\u003eit\u003c/sub\u003e value, enhances efficiency. When D\u003csub\u003eit\u003c/sub\u003e has a value about 1 \u0026times; 10\u003csup\u003e9\u003c/sup\u003e cm\u003csup\u003e\u0026minus;2\u003c/sup\u003e/eV at the less oxide layer of approximately 1.5 nm, maximum simulated value of J\u003csub\u003esc\u003c/sub\u003e is 42.71 mA/cm\u003csup\u003e2\u003c/sup\u003e, J\u003csub\u003esc\u003c/sub\u003e remains above 42.71 mA/cm\u003csup\u003e2\u003c/sup\u003e at D\u003csub\u003eit\u003c/sub\u003e value of the 1 \u0026times; 10\u003csup\u003e9\u003c/sup\u003e cm\u003csup\u003e\u0026minus;2\u003c/sup\u003e/eV, whereas it decreases to 20.45 mA/cm\u003csup\u003e2\u003c/sup\u003e when D\u003csub\u003eit\u0026nbsp;\u003c/sub\u003eincreases to 1 \u0026times; 10\u003csup\u003e15\u003c/sup\u003e cm\u003csup\u003e\u0026minus;2\u003c/sup\u003e/eV [32]. Controlling the impact of interface density on \u0026nbsp;solar cell can be achieved via adjusting the oxide thickness in \u0026nbsp;layer. Therefore, it is advisable to minimize D\u003csub\u003eit\u003c/sub\u003e while increasing the tunnel layer thickness to greater than 1 nm, especially as insufficient oxidation, inadequate cleaning, subpar ultra-clean space, and other factors can lead to an increase in interface density. \u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e3.4:\u003c/strong\u003e \u003cstrong\u003eImpact of minority carrier lifetime of p-type Si-wafer with different tunneling oxide layers in TOPCon cell\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003eThe data represented in Figures 17,18, 19 and 20 clearly indicate that the efficiency of cells with the TOPCon structure exhibits a more pronounced improvement as minority carrier lifetime for p-type wafer increases, in comparison to BSF cells. The graphs illustrate that improvement of efficiency TOPCon solar cells is directly related to a longer minority carrier lifetime of p-type silicon. It is essential for the wafer lifetime to be at least 100 \u0026mu;s to observe any significant performance improvement of the TOPCon structure over standard back surface field solar cells, with greater lifetime resulting in better performance enhancement. The ideal lifetime used in the TOPCon structure should be around 500 \u0026mu;s, owed to the poor back side surface passivation and high back rate of surface recombination velocity of 10\u003csup\u003e6\u003c/sup\u003e cm s\u003csup\u003e\u0026minus;1\u003c/sup\u003e for the standard back surface field cell, as opposed to the better back surface recombination velocity of 10\u003csup\u003e3\u003c/sup\u003e cm s\u003csup\u003e\u0026minus;1\u003c/sup\u003e\u0026nbsp; for the TOPCon solar \u0026nbsp;cells, considering interfacial fixed charge, that can be unfavorable for the \u003cem\u003ep\u003c/em\u003e-type and beneficial for the \u003cem\u003en\u003c/em\u003e-type [30]. Figure depicts the superior performance of \u003cem\u003ep\u003c/em\u003e-TOPCon structure with an Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e tunneling layer, attributed to existence of the fixed negative charges at solar Si/Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e interface. In \u003cem\u003en\u003c/em\u003e-TOPCon solar cells, fixed charges at Si/dielectric interface typically amount to +1 \u0026times; 10\u003csup\u003e12\u003c/sup\u003e cm\u003csup\u003e\u0026minus;3\u003c/sup\u003e, similar to SiO\u003csub\u003e2\u003c/sub\u003e. Conversely, in \u003cem\u003ep\u003c/em\u003e-TOPCon solar cells, typical value for fixed charges at the Si/dielectric interface is -1 \u0026times; 10\u003csup\u003e13\u003c/sup\u003e cm\u003csup\u003e\u0026minus;3\u003c/sup\u003e, characteristic of Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e [33] and detailed in Table 2.\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eA previous study highlighted the substantial impact of effective electron-hole pair propagation and direct carrier movement towards external circuits following illumination on outstanding efficiency of the TOPCon solar structure. To get maximum efficiency of the \u003cem\u003ep\u003c/em\u003e-type TOPCon solar cells, it is essential to enhance optical confinement within absorbing layers, improve surface passivating properties of cells, and improve thin tunnel oxide layer and the doped poly-silicon layer to improve\u0026nbsp;quality of surface passivation in the TOPCon solar cell. Notably, unabsorbed light passing from rear side of the metallic contact is reflected back into the solar cell\u0026apos;s absorbing layer, thereby rising actual value both J\u003csub\u003esc\u003c/sub\u003e (short-circuit current density) and the PCE (power conversion efficiency).\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e3.5 Optimized TOPCon solar cell device\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003eWe have studied the impact of the different tunneling oxide layers in combination with different TCOs in the TOPCon solar cell and used optimized calculated parameters to model it with AFORS-HET software. In the final structure, we used a transparent conductive oxide \u0026nbsp;ARC of ITO layer at the top, with 1.5 nm AlO\u003csub\u003ex\u003c/sub\u003e tunneling oxide layer. We were able to improve performance of our modeled TOPCon solar cell by achieving V\u003csub\u003eoc\u003c/sub\u003e= 693 mV, J\u003csub\u003esc\u003c/sub\u003e=42.71 mA/cm\u003csup\u003e2\u003c/sup\u003e, FF=88.39%, Efficiency = 26.16 % and EQE =95 %. Figure 21 demonstrates the optimized structure\u0026rsquo;s JV curve and External Quantum Efficiency (EQE).\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThe effect of different transparent conductive oxides (TCOs) and tunneling oxide layers was studied to understand their impact on performance of TOPCon-based solar cells. TCOs act as surface passivation and the anti-reflective layer on front textured surface, reducing light reflection and surface recombination. This results in an increased the conversion efficiency of TOPCon solar cells. By optimizing tunnel dielectric materials such as SiO\u003csub\u003e2\u003c/sub\u003e, ZrO\u003csub\u003e2\u003c/sub\u003e, Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, TiO\u003csub\u003e2\u003c/sub\u003e, and HfO\u003csub\u003e2\u003c/sub\u003e, we achieved superior results showing effective passivation and optical light capture in optimized TOPCon solar cell. Ultimately, we achieved best performance with ITO as TCO and AlO\u003csub\u003ex\u003c/sub\u003e as tunneling oxide layer. The present study showed that the use of p-type silicon with the Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e tunneling oxide layer and ITO as TCO enhanced the TOPCon solar cell performance to 26.16%. The findings offer valuable insights for the designing and the developing the cost-effective TOPCon solar cell with enhanced performance.\u003c/p\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors would like to acknowledge the British Council for their funding under PAK-UK ICRG 2020 project (006327/D/ISB/008/2021) to create a research group of MS, Ph.D., and postdoctoral students and establishment of \u0026ldquo;Semiconductor Physics and Renewable Energy Laboratory\u0026rdquo; (SPREL) at Government College University Faisalabad Pakistan and authors would thanks the researchers supporting project number (RSPD2025R993), King Saud University, Riyadh, Saudi Arabia\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors would like to acknowledge the British Council for their funding under PAK-UK ICRG 2020 project (006327/D/ISB/008/2021) to create a research group of MS, Ph.D., and postdoctoral students and establishment of \u0026ldquo;Semiconductor Physics and Renewable Energy Laboratory\u0026rdquo; (SPREL) at Government College University Faisalabad Pakistan and authors would thanks the researchers supporting project number (RSPD2025R993), King Saud University, Riyadh, Saudi Arabia\u003c/p\u003e\n\u003cp\u003eNo data sets were generated or analysied during the current study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical approval\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors declare that the manuscript does not contain studies on human subjects, human data, or tissues, or animals.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interest\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor\u0026rsquo;s city detail\u003c/strong\u003e\u003c/p\u003e\n\u003cdiv\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eAuthor\u0026rsquo;s\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;name\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eCity\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003eRabia Saeed\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003eFaisalabad, Pakistan\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003eSofia Tahir\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003eFaisalabad, Pakistan\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003eShammas Mushtaq\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003eFaisalabad, Pakistan\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003eAhmed Ahmed Ibrahim\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003eRiyadh, Saudi Arabia\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003eJaved Iqbal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003eFaisalabad, Pakistan\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003eEffat Yasin\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003eFaisalabad, Pakistan\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003eQurat ul Ain Asif\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003eFaisalabad, Pakistan\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003eKiran Mehmood\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003eFaisalabad, Pakistan\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eMasson G et al (2020) IEA PVPS report-trends in photovoltaic applications 2020. International Energy Agency, Paris, France\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMadumelu C et al \u003cem\u003eImpact of Oxide Thickness, Emitter Sheet Resistance, and Polysilicon Doping Concentration on the Passivation Quality and Long-Term Stability of Topcon Solar Cells\u003c/em\u003e. Emitter Sheet Resistance, and Polysilicon Doping Concentration on the Passivation Quality and Long-Term Stability of Topcon Solar Cells\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhou J et al (2022) Computational Exploration Toward Tunnel Oxide Passivated Contact (TOPCon) Solar Cells: Tailoring Higher Efficiency. Adv Theory Simulations 5(4):2100570\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTao Y et al (2016) Large area tunnel oxide passivated rear contact n-type Si solar cells with 21.2% efficiency. Prog Photovoltaics Res Appl 24(6):830\u0026ndash;835\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBonilla RS et al (2017) Dielectric surface passivation for silicon solar cells: A review. Phys status solidi (a) 214(7):1700293\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCheng H et al (2022) 21.16%-efficiency p-type TOPCon solar cell with ALD-Al2O3/MoOx/Ag as a hole-selective passivating contact. Sol Energy 247:171\u0026ndash;176\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTong H et al (2018) A strong-oxidizing mixed acid derived high-quality silicon oxide tunneling layer for polysilicon passivated contact silicon solar cell. Sol Energy Mater Sol Cells 188:149\u0026ndash;155\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSchmidt J et al (2012) Advances in the surface passivation of silicon solar cells. Energy Procedia 15:30\u0026ndash;39\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFeldmann F et al (2014) Passivated rear contacts for high-efficiency n-type Si solar cells providing high interface passivation quality and excellent transport characteristics. Sol Energy Mater Sol Cells 120:270\u0026ndash;274\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFell A et al (2018) Modeling edge recombination in silicon solar cells. IEEE J Photovolt 8(2):428\u0026ndash;434\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGlunz SW, Preu R, Biro D (2012) Crystalline silicon solar cells: state-of-the-art and future developments. Compr Renew energy 1:353\u0026ndash;387\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSugiura T, Matsumoto S, Nakano N (2020) Numerical analysis of p-type and n-type based carrier-selective contact solar cells with tunneling oxide thickness and bulk properties. Jpn J Appl Phys 59(SG):SGGF03\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang Z et al (2018) Carrier transport through the ultrathin silicon-oxide layer in tunnel oxide passivated contact (TOPCon) c-Si solar cells. Sol Energy Mater Sol Cells 187:113\u0026ndash;122\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFeldmann F et al (2014) Efficient carrier-selective p-and n-contacts for Si solar cells. Sol Energy Mater Sol Cells 131:100\u0026ndash;104\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRichter A et al (2021) Design rules for high-efficiency both-sides-contacted silicon solar cells with balanced charge carrier transport and recombination losses. Nat Energy 6(4):429\u0026ndash;438\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSteinkemper H et al (2015) Numerical simulation of carrier-selective electron contacts featuring tunnel oxides. IEEE J Photovolt 5(5):1348\u0026ndash;1356\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSteinkemper H et al (2015) Theoretical investigation of carrier-selective contacts featuring tunnel oxides by means of numerical device simulation. Energy Procedia 77:195\u0026ndash;201\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZeng Y et al (2017) Theoretical exploration towards high-efficiency tunnel oxide passivated carrier-selective contacts (TOPCon) solar cells. Sol Energy 155:654\u0026ndash;660\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFroitzheim A et al (2003) \u003cem\u003eAFORS-HET: a computer-program for the simulation of heterojunction solar cells to be distributed for public use\u003c/em\u003e. in \u003cem\u003e3rd World Conference onPhotovoltaic Energy Conversion\u003c/em\u003e, Proceedings of. 2003. IEEE\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBrendel R, Peibst R (2016) Contact selectivity and efficiency in crystalline silicon photovoltaics. IEEE J Photovolt 6(6):1413\u0026ndash;1420\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRien\u0026auml;cker M et al (2016) Junction resistivity of carrier-selective polysilicon on oxide junctions and its impact on solar cell performance. IEEE J Photovolt 7(1):11\u0026ndash;18\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChavan GT et al (2023) A brief review of transparent conducting oxides (TCO): the influence of different deposition techniques on the efficiency of solar cells. Nanomaterials 13(7):1226\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRichter A et al (2017) n-Type Si solar cells with passivating electron contact: Identifying sources for efficiency limitations by wafer thickness and resistivity variation. Sol Energy Mater Sol Cells 173:96\u0026ndash;105\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMatsumoto T et al (2017) Ultrathin SiO2 layer formed by the nitric acid oxidation of Si (NAOS) method to improve the thermal-SiO2/Si interface for crystalline Si solar cells. Appl Surf Sci 395:56\u0026ndash;60\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKaur G et al (2020) Improved silicon oxide/polysilicon passivated contacts for high efficiency solar cells via optimized tunnel layer annealing. Sol Energy Mater Sol Cells 217:110720\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRajendran V et al (2024) Indium tin oxide thin film preparation and property relationship for humidity sensing: A review. Eng Rep 6(3):e12836\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLu L et al (2021) Dopant diffusion through ultrathin AlOx and AlOx/SiOx tunnel layer in TOPCon structure and its impact on the passivation quality on c-Si solar cells. Sol Energy Mater Sol Cells 223:110970\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYang Z et al (2021) Charge-carrier dynamics for silicon oxide tunneling junctions mediated by local pinholes. Cell Rep Phys Sci, 2(12)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLancaster K et al (2016) Study of pinhole conductivity at passivated carrier-selected contacts of silicon solar cells. Energy Procedia 92:116\u0026ndash;121\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAcharyya S et al (2022) Performance analysis of different dielectrics for solar cells with TOPCon structure. J Comput Electron 21(2):471\u0026ndash;490\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKhokhar MQ et al (2021) Improving passivation properties using a nano-crystalline silicon oxide layer for high-efficiency TOPCon cells. Infrared Phys Technol 115:103723\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi Y et al (2004) Preferential growth of semiconducting single-walled carbon nanotubes by a plasma enhanced CVD method. Nano Lett 4(2):317\u0026ndash;321\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFeldmann F et al (2014) Tunnel oxide passivated contacts as an alternative to partial rear contacts. Sol Energy Mater Sol Cells 131:46\u0026ndash;50\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"silicon","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scon","sideBox":"Learn more about [Silicon](https://www.springer.com/journal/12633)","snPcode":"12633","submissionUrl":"https://submission.nature.com/new-submission/12633/3","title":"Silicon","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"TCOs, tunnelling oxide, AFORS-HET, TOPCon, pin hole density, surface passivation","lastPublishedDoi":"10.21203/rs.3.rs-6217606/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6217606/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe Tunnel Oxide Passivated Contact (TOPCon) solar cell represents an advanced iteration of the first-generation PERT solar cell, renowned for its high power conversion efficiency. Performance of the TOPCon solar cells relies on characteristics of the dielectric material from which the tunneling occurs. In this study, performance of the Tunnel Oxide Passivated Contact (TOPCon) solar cells and the impact of various transparent conducting oxides and tunnelling oxide layers on them were accessed. The study involved a detailed analysis of key parameters, such as the use of TCOs (FTO, AZO, ZnO, ITO) as a passivation layer and optically transparent electrodes, in combination with different alternative tunnelling oxide dielectric layers (SiO\u003csub\u003e2\u003c/sub\u003e, Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, HfO\u003csub\u003e2\u003c/sub\u003e, ZrO\u003csub\u003e2\u003c/sub\u003e, and TiO\u003csub\u003e2\u003c/sub\u003e) by using the AFORS-HET simulation software. The results showed that existence of an ultra-thin oxide layer with low interface states density (D\u003csub\u003eit\u003c/sub\u003e \u003cb\u003e\u0026asymp;\u003c/b\u003e 1 \u003cb\u003e\u0026times;\u003c/b\u003e 10\u003csup\u003e9\u003c/sup\u003e cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e eV\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), and pinhole density (D\u003csub\u003eph\u003c/sub\u003e \u003cb\u003e\u0026lt;\u003c/b\u003e 1 \u003cb\u003e\u0026times;\u003c/b\u003e 10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e) suppressed carrier recombination at the rear surface. The optimum solar cell performance values were found to be V\u003csub\u003eoc\u003c/sub\u003e = 693 mV, J\u003csub\u003esc\u003c/sub\u003e = 42.71 mA/cm\u003csup\u003e2\u003c/sup\u003e, FF\u0026thinsp;=\u0026thinsp;88.39%, and packing conversion efficiency (PCE)\u0026thinsp;=\u0026thinsp;26.16% with an Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e tunnel dielectric layer.\u003c/p\u003e","manuscriptTitle":"Investigating the influence of TCOs and tunneling dielectric layers on TOPCon solar cell performance","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-05-16 12:32:13","doi":"10.21203/rs.3.rs-6217606/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-06-10T02:58:35+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-05-24T03:32:42+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-05-23T07:15:12+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-05-21T08:08:27+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-05-19T07:30:09+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"87840488856916225020670553659111411483","date":"2025-05-14T09:14:42+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"6278168584115871721367906937609598477","date":"2025-05-14T07:12:46+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"120632943849251874829273727657030959930","date":"2025-05-14T06:57:24+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"95818646934723780088378465528733928393","date":"2025-05-14T06:32:14+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"70796523186974655620704366182623384532","date":"2025-05-14T06:09:09+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-05-14T06:00:11+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-04-07T00:09:33+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-04-07T00:07:55+00:00","index":"","fulltext":""},{"type":"submitted","content":"Silicon","date":"2025-03-13T07:38:36+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"silicon","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scon","sideBox":"Learn more about [Silicon](https://www.springer.com/journal/12633)","snPcode":"12633","submissionUrl":"https://submission.nature.com/new-submission/12633/3","title":"Silicon","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"e2753d03-f366-4fc9-aff1-8956be67f61d","owner":[],"postedDate":"May 16th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-03-02T16:01:10+00:00","versionOfRecord":{"articleIdentity":"rs-6217606","link":"https://doi.org/10.1007/s12633-025-03637-5","journal":{"identity":"silicon","isVorOnly":false,"title":"Silicon"},"publishedOn":"2026-02-23 15:57:17","publishedOnDateReadable":"February 23rd, 2026"},"versionCreatedAt":"2025-05-16 12:32:13","video":"","vorDoi":"10.1007/s12633-025-03637-5","vorDoiUrl":"https://doi.org/10.1007/s12633-025-03637-5","workflowStages":[]},"version":"v1","identity":"rs-6217606","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6217606","identity":"rs-6217606","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}