Chemical Texturing Used to Reduce The Reflectance of the Multi-Crystalline Silicon Wafer For Improving Optical Properties and Solar Cell Efficiency

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Generally, HF and HNO 3 are using the mc-Si wafer acid texturization process and it is toxic chemical acids. In this work, H 2 O 2 is used instead of HNO 3 because of H 2 O 2 less toxic chemical compared to HNO 3 . In this work, we have used the different types of chemical acids in different ratios for etching. Here, we have used HF: H 2 O 2 : CH 3 COOH=3:2:2, HF: H 2 O 2 : KMnO 4 =3:2:0.2 M and HF: H 2 O 2 : HNO 3 : KMnO 4 =3:2:2:0.2M for etching with the etching time of 60 sec. The HF: H 2 O 2 : KMnO 4 =3:2:0.2M gives the better results as obtained from optical microscope, UV- Visible reflectance studies and X-ray diffraction (XRD) studies. The etched mc-Silicon wafer surface was analyzed by the optical microscope and Scanning Electron Microscope (SEM). The FTIR results indicate the reduction of oxidation in the etched samples. Moreover, the HF: H 2 O 2 : KMnO 4 =3:2:0.2M textured wafers have the advantages of lower reflectance and increased etching of the mc-Silicon wafer. Electronic Materials and Devices Acid and base Texturization Multicrystalline silicon Light trapping Solar cell Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Introduction Surface reflections are considered as a key process to achieve higher efficiencies in solar cells. Mc-Silicon has occupied larger percent of the silicon solar cell market due to its low cost. However, the effective surface texturing in mc-Silicon is a challenging task for solar cell application. The different type of chemical textures was used for the etching process. Acid mediated texture on etching is a key technology to fabricate mc-Silicon for solar cell application. Because, it is a cost effective technique to get high efficiency. The different types of etching process were used to reduce the light reflectance. Reactive Ion Etching (RIE) [ 1 ], Metal-catalyzed chemical etching (MACE) [ 2 ], Plasma texturing, plasma-less atmospheric pressure dry [ 3 ] and acidic texturing [ 4 ] were used to reduce the reflectance in mc-Silicon wafer. RIE and MACE methods give less than 5% reflectance. But, these are inadmissible in the photovoltaic field due to low throughput and process complexity [ 4 ]. These are also expensive etching methods. The chemical etching is most widely used to remove unbounded molecule and impurities. In general, alkaline solution based anisotropic etching was adopted for the single crystalline - silicon and in the case of mc-silicon the acid solution based isotropic etching has been performed. Usually, random sized pyramid structures are obtained in c-silicon and “worm like” structures are obtained in mc-Silicon. More specifically, the texturization of the (100) oriented C- Silicon wafers have already been commercialized based on alkali or isopropyl alcohol etching process [ 5 ]. Mc-Silicon is different from c-Silicon. Randomly oriented crystalline grains make the grain boundaries and it is unavoidable in the mc-Silicon. Mechanical etching and laser etching textures gave regular microstructure surface. But, it reduces photoelectric conversion. Further, it is highly expensive and not suitable for mass production [ 8 ]. Acidic etching is a key technology on Texturing the mc-Silicon wafer to reducing the reflectance of the wafer. In addition, it gives higher efficiency, increasing the optical path length and it is least expensive method. Sheng et al., [ 9 ] have investigated the crystal orientation and crystalline peak intensity of the etched silicon wafers. The X-ray diffractogram result indicates that the crystalline peak intensity of the etched silicon wafer is slightly shifted to lower 2θ compared to without etched wafer. Shuai Z et al., [ 10 ] have optimized chemical etching (MCCE) of the mc-Silicon wafers with different orientation with both alkali and metal-catalyzed chemical etching. Gangopadhyay et al., [ 11 ] have analyzed the different ratios of sodium hydroxide–sodium hypochlorite (NaOH–NaOCl) texturing solution with mc-Silicon. They have showed the formation of Si-Cl bonds through the FTIR imaging and the bonds have improved the quality of the diffused junction. In this paper, the reaction behavior of the mc-Silicon in HF –H 2 O 2 – CH 3 COOH/ KMnO 4 / HNO 3 –KMnO 4 etching mixtures is studied and the appropriate composition of the texturing reaction mixture was found. It is obtaining the effective isotropic surface texture of mc-Silicon solar cells in a short time of 60 secs and it is helpful in improving the optical properties. The weight loss, reducing the reflection, surface morphology and crystal structure of the mc-Silicon wafer were determined by using the digital micrometre, UV-Vis-NIR Spectrophotometer, optical microscope and X-Ray diffractometer (XRD), respectively. The etching mechanism is studied for different grains of mc-Silicon wafers. The reduction of the oxidation is also studied by using FTIR. Experimental Section The random small size mc-Silicon wafers are cut from the commercial P-type multi-crystalline silicon wafers with 180-micron thickness. Before processing, the wafers were cleaned in RCA1 and the experiment was carried out in HF –H 2 O 2 – CH 3 COOH/ KMnO 4 / HNO 3 –KMnO 4 solutions. After etching, the mc-Silicon wafers are placed in deionized water for 1 minute. The weight of the wafer was taken before and after etching process. The different type of chemical etching solutions and the result of improved solar cell efficiency are shown in Table.1. It is indicating that the texturization of mc-Silicon wafer is leading to a significant reduction in reflectivity and gives high values of short circuit current [ 12 ]. The surface morphology of the mc-Silicon wafers was studied using Scanning Electron Microscopy (SEM) QUANTA 200 3D Dual Beam (FEI) and CMM-23 COSLAB Microscope. The crystal structure and orientation were studied using Analytical Empyrean X-ray diffractometer (XRD) with CuK α radiation ((λ = 1.5406 Å). UV-Vis-NIR spectrophotometer (Lamda 35, PerkinElmer) was used to measure the surface reflectivity. Table. 1. Literature survey of few chemical etching rates, the steps of the chemical etching process and the results of the efficiency. S.no Cleaning before etching Etchant Name Acid ratio Cleaning after etching Result 1 RCA1 cleaning Other method: (Mechanical etching Laser etching) (2014) Isotropic Etching HF + HNO 3 + H 2 SO 4 1: 1.6: 8.2 = 60 sec (Time) HF + HNO 3 + CH 3 COOH 2: 3 : 6 = 60 sec (Time) Double distilled water 14.7 % Conversion efficiency 2 HF + HNO 3 + H 2 O 3: 1: 2 = 60 sec (Time) (2017) Isotropic Etching KMnO 4 = 2.5 M HF = 4.5 M Time = 10 Minutes NH 4 OH and H 2 O 2 Time = 90 sec After rinsed in DI water 18.3% Power Conversion efficiency 3 Acetone & HF = 7.5 M (2010) Isotropic Etching KMnO 4 = 0.2 M HF = 11.0 M HNO 3 = 0.2M Different ratio etching (Time = 1 min / 120 min /180 minutes) Double distilled water Porous silicon 4 KOH + IPA + H 2 O 80*C for 3 minutes (2014) Isotropic Etching HF + HNO 3 + CH 3 COOH/H 2 O (7:1:2) Time one minute (15:2.5:1) Time 60 sec (10:1:1) Time 60 minutes Double distilled water 22% Conversion efficiency 2.1 Etching mechanism and Etching of mc-Silicon wafers Mc-Silicon wafers with lower reflectance and lower recombination defects enhances the solar cell conversion efficiency. This can be obtained by chemical etching process with low cost. The wet chemical etching process is used for the removal of metal impurities from texturing of the silicon wafer and silicon materials. Acid texturing in a mc-Silicon wafer has been performed using a Hydrofluoric (HF) and Hydrogen peroxide (HNO 3 ). The general etching mechanism is of two steps: (1) the SiO 2 is formed by nitric acid on the surface of the mc-Silicon wafer and then (2) SiO 2 is removed from the wafer surface via water-soluble complexes formed by HF [ 13 ]. The HNO₃ produces an SiO 2 layer 3Si + 4HNO 3 →3SiO 2 + 4NO + 2H 2 O (1) It is dissolved by HF SiO 2 + 6HF →H 2 SiF 6 + 2H 2 O (2) The overall reaction is: 3Si + 4HNO 3 + 18HF → 3H 2 SiF 6 + 4NO + 2H 2 O (3) The described mechanism of silicon dissolution is an electrochemical process on the silicon surface. In this process, holes (h+) were injected in the valence band of the semiconductor by HNO 3 at local cathodic sites, followed by the formation of a SiO 2 layer which is dissolved by HF at local anodic sites. The formation of SiO 2 layers was confirmed by the X-ray Photoelectron Spectroscopy studies [ 14 ]. M. Steinert et al have [ 15 ] studied silicon etching process using HNO 3 -rich HF/HNO 3 using XPS. The higher nitrite concentration reduces the etching rate slightly and lower nitrite concentration increases the etching rate linearly. Stirring is also increasing the etching rate. In this work, Hydrogen peroxide (H 2 O 2 ) was used instead of the nitric acid (HNO₃) and etching mechanism of these combinations is as follows: The H 2 O 2 produces an SiO 2 layer 3Si + 2H 2 O 2 →SiO 2 + 2H 2 O (4) It is dissolved by HF SiO 2 + 6HF →H 2 SiF 6 + 2H 2 O (5) The overall reaction is: Si + 2H 2 O 2 + 6HF → H 2 SiF 6 + 4H 2 O (6) The electrochemical process works just like conventional operations. The mc-Silicon wafers were cleaned in RCA-1 process at 10 minutes and the purpose of the cleaning was to remove the organic residue on the silicon wafer surfaces. It is placed in deionized water for a few seconds. Three set of chemicals with different volume and molar ratios were selected for etching process at room temperature and etching duration was 60 sec. The first set of etching chemical solution is HF-H 2 O 2 -CH 3 COOH with volume ratio of 3:2:2, second set of chemical solution is HF-H 2 O 2 -KMnO 4 with volume and mole ratio of 3:2:0.2M, third set of chemical solution is HNO 3 -HF-H 2 O 2 -KMnO 4 with volume and mole ratio of 3:2:2:0.2M. the combination of the HF and HNO 3 were optimized to remove residual surface strain. Results And Discussion 3.1 Reflectance of the mc-Silicon wafers The acid etching is sufficient to create isotropic surface texture of the wafer and to avoid the saw damages. The reflectance of the mc-Silicon textured surfaces are investigated from wavelength between 300–1000 nm and shown in Figure.1. Three set of etched samples and reference silicon sample reflectance results were compared and shown in Figure.1. It is clearly seen that Set-2 (HF-H 2 O 2 -KMnO 4 ) chemical ratio reduces the reflectivity and the reduction up to 12.5 %. The Set- 2 chemical ratios in etching process strongly influences the effective reflectance. It has higher light absorbance compared to other chemical textured wafers since, the higher light absorbance leads to increase the solar cell efficiency. Kulesza et al., have optimized [ 12 ] the time efficient texturization of mc-Silicon in the HF/HNO 3 solution and its effect on the optoelectonic parameters of the solar cells. The optimal chemical etching ratio has increased the solar cell efficiency up to 13.9 %. 3.2 Crystalline structure of the grain orientation Figure. 2 shows the XRD pattern before and after chemically etching the samples. The crystalline structure of the wafers is investigated by using Analytical Empyrean X-ray diffractometer (XRD) with CuK α radiation ((λ = 1.5406 Å). The XRD pattern of silicon wafer shows the characteristic peak 28.40 and 56.10 (JCPDS file 271402) which correspond to (111) and (311). From the Fig. 2(a), HF: H 2 O 2 : CH 3 COOH etched wafer gives slight peak shift to a lower value of 2θ in the (311) orientations. Sheng et al., [ 18 ] have optimized the mixture solution of HF: HNO 3 : CH 3 COOH with different time and concentration. From the Fig. 2(b), HF: H 2 O 2 : KMnO 4 etched wafer gives higher intensity in the (111) orientations and lower light reflection. Zou et al., [ 17 ] have done the alkali and Ag- MCCE etching of the (111) orientated mc-Silicon wafers expose dark appearance owing to the excellent light-trapping ability with Pyramid structure. From the Fig. 2(c), HF: H 2 O 2 :HNO 3 : KMnO 4 etched wafer gives higher intensity in the (311) orientations and appear shiny. This refers to the higher inter planer spacing values of the atomic layers in silicon. In XRD results, the etched silicon wafers have given the higher intensity with slight peak shift in lower 2θ angle side. The X-ray diffraction (XRD) result of HF: H 2 O 2 :KMnO 4 indicates that the crystalline peak intensity of the etched mc-Silicon is higher than non- etched wafer and HF: H 2 O 2 : CH 3 COOH = 3:2:2 etched results indicates the peak shift slightly to lower 2θ. Moreover, the HF: H 2 O 2 :KMnO 4 = 3:2:0.2M textured wafers have the advantages of lower reflectance and increased etching of the mc-Silicon wafer. 3.3 Surface morphology of the mc-Silicon wafers: The surface structures of the etched mc-Silicon wafers were investigated by using an optical microscope and SEM. Figure. 3, shows the changes occurred on the mc-Silicon wafers after etching by using an optical microscope at a resolution of 500X. Different etched patterns were produced by using three different chemical etching solution in the silicon surface. The comparison in results, the surface structures are considerably changed by using HF:H 2 O 2 : KMnO 4 chemical solution. This chemical solution induces the small size uneven worm-like trenches and it has given lower reflectance compared to other two chemical solutions etched samples. The HF: H 2 O 2 :HNO 3 : KMnO 4 chemical solution induces the medium size worm-like trenches structures. The HF: H 2 O 2 : CH 3 COOH chemical solution gives very small size worm-like trenches structures and it has given slightly lower reflectance compared to non-etched wafer. An optimization of the three different textured solutions were helpful to achieving lower reflectance. The SEM images of silicon wafer surface are shown in Figure.4. The saw damage has been removed and the mc-Silicon defects have disappeared by the etching process. Images show the formation of oval pits smoothened surface after etching the wafers at in HF/ H 2 O 2 /CH 3 COOH and HF/H 2 O 2 / KMnO 4 textured solutions. HF/ H 2 O 2 /CH 3 COOH gives 3–6 µm size oval pits and HF/H 2 O 2 / KMnO 4 textured solutions gives 2–4 µm size oval pits which are shown in figure.5. HF/H 2 O 2 / KMnO 4 results is reduced loss of weight compared to HF/ H 2 O 2 /CH 3 COOH textured solution and it is shown in Table.2. Kulesza et al have performed [ 12 ] the time efficient texturization process with HF/HNO 3 solutions. They reported that this etching process is improving the optoelectronic parameters of the solar cell. Higher concentration of HF/ HNO 3 results in the formation of round pits with varying diameters. Optimized etching solution gives lower reflectance and higher efficiency. HF/H 2 O 2 / KMnO 4 textured solution led to formation of round pits in some places and MnO 4 is glazed. The solution HF/H 2 O 2 / KMnO 4 / HNO 3 is causing more corrosion and it is shown in Figure.6. It reduces more weight and it is shown in Table.2. The HF/H 2 O 2 / KMnO 4 solution is showing the optimal oval pit structure with the lowest reflectance. Table. 2 Weight of wafer before and after chemical etching Chemical Etchant Before etching (g) After etching for 60 sec (g) Loss of Weight (g) HF + H 2 O 2 + CH 3 COOH 0.14708 0.14675 0.00033 HF + H 2 O 2 + KMnO 4 0.14903 0.14890 0.00013 HF + H 2 O 2 + HNO 3 + KMnO 4 0.22467 0.22420 0.00040 3.4 FTIR Studies for Analysing impurities : Wet etching of the mc- Silicon wafers is a critical step in the solar cell making process. Optimized wet etching process improves the optical properties [ 19 , 20 ]. The recombination properties of mc-Silicon solar cells are more complex owing to the structural defects, point defects and interaction among defects. Oxygen segregation in structural defects affects electrical activity and further complicates it. Pizzini et al., [ 21 ] confirmed an oxygen segregation in the structural defects and they showed its influence on dislocation electrical activity. IR absorption spectroscopy is an important tool to study the nature of HF etched silicon. Reduction of oxidation is confirmed in three different textured solutions and it is shown in the IR spectrum of Figure.7. The peak position of Si–O–Si bonds at 1107 cm − 1 and its reflectance are decreased in Figure.7. The combination of HF/ H 2 O 2 /CH 3 COOH etching solution significantly decreases the Si–O–Si reflectance. The combination of HF/H 2 O 2 / KMnO 4 reduces the Si–O–Si reflectance and C-H reflectance. The combination of HF/H 2 O 2 / KMnO 4 / HNO 3 greatly decreases the Si–O–Si reflectance and C-H reflectance compared to the combination of HF/H 2 O 2 / KMnO 4 . But, the combination of HF/H 2 O 2 / KMnO 4 / HNO 3 is causing more corrosion and it is more reflecting the light source. Conclusion Acid texturization based on HF: H 2 O 2 : (CH 3 COOH or KMnO 4 or KMnO 4 :HNO 3 ) mixture was demonstrated. The result of the two mixtures solutions HF: H 2 O 2 : (CH 3 COOH or KMnO 4 ) were led to formation of round pits with different diameter in the single step and HF: H 2 O 2 : KMnO 4 :HNO 3 texturization solution has given uneven surface. Silicon wafers engraved with HF: H 2 O 2 : KMnO 4 have high optoelectronic parameters. HF: H 2 O 2 : KMnO 4 solution gives high intensity in the (111) orientations and lower reflectance compared to other two solutions. It reduced the oxidation (Si–O–Si) reflectance and improved the electrical activity. The reduced surface reflectance and reduced oxidation were reducing the surface recombination loss and increasing the short circuit current (J sc ). In solar cell making process, HF: H 2 O 2 : KMnO 4 based textured wafer can give higher conversion efficiency. Declarations Funding This work was supported by the Department of science and technology Government of India (Order No. DST/TMD/CERI/RES/2020/7(c)dated on 31/12/2020). Conflicts of interest/Competing interests Not applicable Availability of data and material Not applicable Code availability Not applicable Authors' contributions All the authors are equal contribution in the manuscript. Madhesh Raji - Writing - Original Draft Kesavan Venkatachalam- Formal Analysis, Investigation, Srinivasan Manikkam- Supervision Ramasamy Perumalsamy - review & editing Disclosure of potential conflicts of interest Not applicable Research involving Human Participants and/or Animals Not applicable Acknowledgements This work was supported by the Department of science and technology Government of India (Order No. DST/TMD/CERI/RES/2020/7(c)dated on 31/12/2020). Compliance with ethical standards This study involving human participants were in accordance with the ethical standards of the institutional and/or national research committee. Consent to participate Informed consent was obtained from all individual participants included in the study Consent for Publication Consent for publication was obtained from all individual participants included in the study References Ying Z, Liao M, Yang X, Han C, Li J, Li J, Li Y, Gao P, Ye J (2016) High-performance black multicrystalline silicon solar cells by a highly simplified metal-catalyzed chemical etching method. IEEE J Photovolt 6(4):888–893 Yang W, Shen H, Jiang Y, Tang Q, Raza A, Gao K (2019) Formation of Inverted Pyramid-Like Submicron Structures on Multicrystalline Silicon Using Nitric Acid as Oxidant in Metal Assisted Chemical Etching Process. physica status solidi (a), 216(4), p.1800636 Kafle B, Ridoy AI, Saint-Cast P, Clochard L, Duffy E, Duncker K, Petter K, Hofmann M, Rentsch J, 2018, August. Atmospheric pressure dry texturing enabling 20% conversion efficiency on multicrystalline silicon PERC solar cells. 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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-934808","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":54537079,"identity":"d871bcd3-6c75-487b-a136-db2040920564","order_by":0,"name":"Madhesh Raji","email":"","orcid":"","institution":"Sri Sivasubramaniya Nadar College of Engineering","correspondingAuthor":false,"prefix":"","firstName":"Madhesh","middleName":"","lastName":"Raji","suffix":""},{"id":54537080,"identity":"31d9ed48-7fbd-4e7f-8861-f26bdead1fab","order_by":1,"name":"Kesavan Venkatachalam","email":"","orcid":"","institution":"Sri Sivasubramaniya Nadar College of Engineering","correspondingAuthor":false,"prefix":"","firstName":"Kesavan","middleName":"","lastName":"Venkatachalam","suffix":""},{"id":54537081,"identity":"37f36bf9-d65a-4774-8b20-7a1f1bd187b4","order_by":2,"name":"Srinivasan Manikkam","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA4ElEQVRIie3PMQrCMBSA4YRAugRdLVV6hUL35ioNXbs5SYcqhbjkBt4jF8jQpTgLLq2CewehQgcTXZzaugnmH5I35CMJADbbTwa3IH4Pu1qvZDaZEACLwOx48mUEALwwwyjxD4rXdR9R6im+uafREgPUXE4DJDiyfcB4wsSM8fNKJvphOAzTIUIgX7Atiokezq5EmhDsDRFfaBL3OTVk7cp8nIDKEKyg0AS2Uo2TwBDGSyYqWHhQlgSjkb/4wrm5XZ9RRzhN+5AZnTtFcx182GeIvNapx02w++a0zWaz/U1P6wY/mACmc0gAAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0003-2112-0338","institution":"Sri Sivasubramaniya Nadar College of Engineering","correspondingAuthor":true,"prefix":"","firstName":"Srinivasan","middleName":"","lastName":"Manikkam","suffix":""},{"id":54537082,"identity":"96ce6147-aad9-4b6c-a5f0-d61491c73d22","order_by":3,"name":"Ramasamy Perumal","email":"","orcid":"","institution":"Sri Sivasubramaniya Nadar College of Engineering","correspondingAuthor":false,"prefix":"","firstName":"Ramasamy","middleName":"","lastName":"Perumal","suffix":""}],"badges":[],"createdAt":"2021-09-24 14:41:54","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-934808/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-934808/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":14558858,"identity":"a44f46be-89f4-4118-a9f0-e2645af2a5af","added_by":"auto","created_at":"2021-10-15 16:13:25","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":18361,"visible":true,"origin":"","legend":"Comparison of the measured reflectance for the non- etching wafer (Reference) and etched wafers with 60 secs. ","description":"","filename":"fig1.png","url":"https://assets-eu.researchsquare.com/files/rs-934808/v1/5ce2bcb767c6159e43670790.png"},{"id":14559050,"identity":"29cb4636-0657-467a-960e-29f4b13cd9cc","added_by":"auto","created_at":"2021-10-15 16:16:25","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":40400,"visible":true,"origin":"","legend":"XRD pattern comparison of before and after etched wafers: (a) HF + H2O2 + CH3COOH, (b) HF + H2O2 + KMnO4 and (c) HF + H2O2 + HNO3 + KMnO4. ","description":"","filename":"fig2.png","url":"https://assets-eu.researchsquare.com/files/rs-934808/v1/2a7f633957a913a373d79c99.png"},{"id":14559051,"identity":"4e87097a-5d01-4adb-933d-767fbcf62675","added_by":"auto","created_at":"2021-10-15 16:16:25","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1628224,"visible":true,"origin":"","legend":"Optical microscopic images for reference wafer and etched wafers: (a) Reference wafer, (b) HF + H2O2 + CH3COOH, (c) HF + H2O2 + KMnO4, and (d) HF + H2O2 + HNO3 + KMnO4 etched wafers.","description":"","filename":"fig3.png","url":"https://assets-eu.researchsquare.com/files/rs-934808/v1/8fb3ea2b5a4f1412359e87bb.png"},{"id":14558862,"identity":"81b1b3dc-be65-4a0b-9931-ea121a9dc0e1","added_by":"auto","created_at":"2021-10-15 16:13:25","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":883350,"visible":true,"origin":"","legend":"SEM images for reference wafer and etched wafers: (a) Reference wafer, (b) HF + H2O2 + CH3COOH, (c) HF + H2O2 + KMnO4, and (d) HF + H2O2 + HNO3 + KMnO4 etched wafers.","description":"","filename":"fig4.png","url":"https://assets-eu.researchsquare.com/files/rs-934808/v1/8796c7b4c48390711634781d.png"},{"id":14558864,"identity":"83e14070-7614-4921-95e2-6e077d47dea8","added_by":"auto","created_at":"2021-10-15 16:13:25","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":377129,"visible":true,"origin":"","legend":"SEM images for etched wafers: (a) HF + H2O2 + CH3COOH and (b) HF + H2O2 + KMnO4 etched wafers.","description":"","filename":"fig5.png","url":"https://assets-eu.researchsquare.com/files/rs-934808/v1/b33d925cf69f6796be559990.png"},{"id":14558861,"identity":"83984f09-a08a-416c-96bf-837967f99535","added_by":"auto","created_at":"2021-10-15 16:13:25","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":463481,"visible":true,"origin":"","legend":"SEM images for reference wafer and etched wafer: (a) Reference wafer and (b) HF + H2O2 + HNO3 + KMnO4 etched wafer.","description":"","filename":"fig6.png","url":"https://assets-eu.researchsquare.com/files/rs-934808/v1/80a968cd56924ffae86b39d8.png"},{"id":14558859,"identity":"adce23ac-4aba-4e72-823a-9d6579bea7ab","added_by":"auto","created_at":"2021-10-15 16:13:25","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":58065,"visible":true,"origin":"","legend":"FTIR spectrum comparison of before and after etched wafers: (a) HF + H2O2 + CH3COOH, (b) HF + H2O2 + KMnO4 and (c) HF + H2O2 + HNO3 + KMnO4. ","description":"","filename":"fig7.png","url":"https://assets-eu.researchsquare.com/files/rs-934808/v1/3f4278f39f8c811a45aae6bc.png"},{"id":16727482,"identity":"2199d440-4513-4ebf-84c5-1efead859574","added_by":"auto","created_at":"2021-12-23 21:14:44","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3720426,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-934808/v1/c33a3339-720e-4036-bd7f-34e9d7a12cdd.pdf"}],"financialInterests":"","formattedTitle":"\u003cp\u003eChemical Texturing Used to Reduce The Reflectance of the Multi-Crystalline Silicon Wafer For Improving Optical Properties and Solar Cell Efficiency\u003c/p\u003e","fulltext":[{"header":"Introduction","content":"\u003cp\u003eSurface reflections are considered as a key process to achieve higher efficiencies in solar cells. Mc-Silicon has occupied larger percent of the silicon solar cell market due to its low cost. However, the effective surface texturing in mc-Silicon is a challenging task for solar cell application. The different type of chemical textures was used for the etching process. Acid mediated texture on etching is a key technology to fabricate mc-Silicon for solar cell application. Because, it is a cost effective technique to get high efficiency. The different types of etching process were used to reduce the light reflectance. Reactive Ion Etching (RIE) [\u003cspan class=\"CitationRef\"\u003e1\u003c/span\u003e], Metal-catalyzed chemical etching (MACE) [\u003cspan class=\"CitationRef\"\u003e2\u003c/span\u003e], Plasma texturing, plasma-less atmospheric pressure dry [\u003cspan class=\"CitationRef\"\u003e3\u003c/span\u003e] and acidic texturing [\u003cspan class=\"CitationRef\"\u003e4\u003c/span\u003e] were used to reduce the reflectance in mc-Silicon wafer. RIE and MACE methods give less than 5% reflectance. But, these are inadmissible in the photovoltaic field due to low throughput and process complexity [\u003cspan class=\"CitationRef\"\u003e4\u003c/span\u003e]. These are also expensive etching methods. The chemical etching is most widely used to remove unbounded molecule and impurities. In general, alkaline solution based anisotropic etching was adopted for the single crystalline - silicon and in the case of mc-silicon the acid solution based isotropic etching has been performed. Usually, random sized pyramid structures are obtained in c-silicon and \u0026ldquo;worm like\u0026rdquo; structures are obtained in mc-Silicon. More specifically, the texturization of the (100) oriented C- Silicon wafers have already been commercialized based on alkali or isopropyl alcohol etching process [\u003cspan class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e\n\u003cp\u003eMc-Silicon is different from c-Silicon. Randomly oriented crystalline grains make the grain boundaries and it is unavoidable in the mc-Silicon. Mechanical etching and laser etching textures gave regular microstructure surface. But, it reduces photoelectric conversion. Further, it is highly expensive and not suitable for mass production [\u003cspan class=\"CitationRef\"\u003e8\u003c/span\u003e]. Acidic etching is a key technology on Texturing the mc-Silicon wafer to reducing the reflectance of the wafer. In addition, it gives higher efficiency, increasing the optical path length and it is least expensive method. Sheng et al., [\u003cspan class=\"CitationRef\"\u003e9\u003c/span\u003e] have investigated the crystal orientation and crystalline peak intensity of the etched silicon wafers. The X-ray diffractogram result indicates that the crystalline peak intensity of the etched silicon wafer is slightly shifted to lower 2\u0026theta; compared to without etched wafer. Shuai Z et al., [\u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e] have optimized chemical etching (MCCE) of the mc-Silicon wafers with different orientation with both alkali and metal-catalyzed chemical etching.\u003c/p\u003e\n\u003cp\u003eGangopadhyay et al., [\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e] have analyzed the different ratios of sodium hydroxide\u0026ndash;sodium hypochlorite (NaOH\u0026ndash;NaOCl) texturing solution with mc-Silicon. They have showed the formation of Si-Cl bonds through the FTIR imaging and the bonds have improved the quality of the diffused junction.\u003c/p\u003e\n\u003cp\u003eIn this paper, the reaction behavior of the mc-Silicon in HF \u0026ndash;H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e\u0026ndash; CH\u003csub\u003e3\u003c/sub\u003eCOOH/ KMnO\u003csub\u003e4\u003c/sub\u003e/ HNO\u003csub\u003e3\u003c/sub\u003e\u0026ndash;KMnO\u003csub\u003e4\u003c/sub\u003e etching mixtures is studied and the appropriate composition of the texturing reaction mixture was found. It is obtaining the effective isotropic surface texture of mc-Silicon solar cells in a short time of 60 secs and it is helpful in improving the optical properties. The weight loss, reducing the reflection, surface morphology and crystal structure of the mc-Silicon wafer were determined by using the digital micrometre, UV-Vis-NIR Spectrophotometer, optical microscope and X-Ray diffractometer (XRD), respectively. The etching mechanism is studied for different grains of mc-Silicon wafers. The reduction of the oxidation is also studied by using FTIR.\u003c/p\u003e"},{"header":"Experimental Section","content":"\u003cp\u003eThe random small size mc-Silicon wafers are cut from the commercial P-type multi-crystalline silicon wafers with 180-micron thickness. Before processing, the wafers were cleaned in RCA1 and the experiment was carried out in HF \u0026ndash;H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e\u0026ndash; CH\u003csub\u003e3\u003c/sub\u003eCOOH/ KMnO\u003csub\u003e4\u003c/sub\u003e/ HNO\u003csub\u003e3\u003c/sub\u003e\u0026ndash;KMnO\u003csub\u003e4\u003c/sub\u003e solutions. After etching, the mc-Silicon wafers are placed in deionized water for 1 minute. The weight of the wafer was taken before and after etching process. The different type of chemical etching solutions and the result of improved solar cell efficiency are shown in Table.1. It is indicating that the texturization of mc-Silicon wafer is leading to a significant reduction in reflectivity and gives high values of short circuit current [\u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e]. The surface morphology of the mc-Silicon wafers was studied using Scanning Electron Microscopy (SEM) QUANTA 200 3D Dual Beam (FEI) and CMM-23 COSLAB Microscope. The crystal structure and orientation were studied using Analytical Empyrean X-ray diffractometer (XRD) with CuK\u003csub\u003e\u0026alpha;\u003c/sub\u003e radiation ((\u0026lambda;\u0026thinsp;=\u0026thinsp;1.5406 \u0026Aring;). UV-Vis-NIR spectrophotometer (Lamda 35, PerkinElmer) was used to measure the surface reflectivity.\u003c/p\u003e\n\u003cp\u003eTable. 1. Literature survey of few chemical etching rates, the steps of the chemical etching process and the results of the efficiency.\u0026nbsp;\u003c/p\u003e\n\u003ctable border=\"1\" cellpadding=\"0\" cellspacing=\"0\" width=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"7.603305785123967%\"\u003e\n \u003cp\u003eS.no\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"22.644628099173552%\"\u003e\n \u003cp\u003eCleaning before etching\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.223140495867769%\"\u003e\n \u003cp\u003eEtchant Name\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"24.793388429752067%\"\u003e\n \u003cp\u003eAcid ratio\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"16.198347107438018%\"\u003e\n \u003cp\u003eCleaning after etching\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"15.537190082644628%\"\u003e\n \u003cp\u003eResult\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"7.603305785123967%\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"22.644628099173552%\"\u003e\n \u003cp\u003eRCA1 cleaning\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eOther method:\u003c/p\u003e\n \u003cp\u003e(Mechanical etching\u003c/p\u003e\n \u003cp\u003eLaser etching)\u003c/p\u003e\n \u003cp\u003e(2014)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.223140495867769%\"\u003e\n \u003cp\u003eIsotropic Etching\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"24.793388429752067%\"\u003e\n \u003cp\u003eHF + HNO\u003csub\u003e3\u003c/sub\u003e + H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;1: 1.6: 8.2 = 60 sec (Time)\u003c/p\u003e\n \u003cp\u003eHF + HNO\u003csub\u003e3\u003c/sub\u003e + CH\u003csub\u003e3\u003c/sub\u003eCOOH \u0026nbsp; \u0026nbsp;2: 3 : 6 = 60 sec (Time)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"16.198347107438018%\"\u003e\n \u003cp\u003eDouble distilled water\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"15.537190082644628%\"\u003e\n \u003cp\u003e14.7 % Conversion efficiency\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"7.603305785123967%\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"22.644628099173552%\"\u003e\n \u003cp\u003eHF + HNO\u003csub\u003e3\u003c/sub\u003e + H\u003csub\u003e2\u003c/sub\u003eO \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;3: 1: 2 = 60 sec (Time) \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;(2017)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.223140495867769%\"\u003e\n \u003cp\u003eIsotropic Etching\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"24.793388429752067%\"\u003e\n \u003cp\u003eKMnO\u003csub\u003e4\u003c/sub\u003e = 2.5 M \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; HF = 4.5 M \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Time = 10 Minutes\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"16.198347107438018%\"\u003e\n \u003cp\u003eNH\u003csub\u003e4\u003c/sub\u003eOH and H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Time = 90 sec After rinsed in DI water\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"15.537190082644628%\"\u003e\n \u003cp\u003e18.3% Power Conversion efficiency\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"7.603305785123967%\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"22.644628099173552%\"\u003e\n \u003cp\u003eAcetone \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026amp; HF = 7.5 M \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;(2010)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.223140495867769%\"\u003e\n \u003cp\u003eIsotropic Etching\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"24.793388429752067%\"\u003e\n \u003cp\u003eKMnO\u003csub\u003e4\u003c/sub\u003e = 0.2 M \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; HF = 11.0 M \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; HNO\u003csub\u003e3\u003c/sub\u003e = 0.2M\u003c/p\u003e\n \u003cp\u003eDifferent ratio etching (Time = 1 min / 120 min /180 minutes)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"16.198347107438018%\"\u003e\n \u003cp\u003eDouble distilled water\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"15.537190082644628%\"\u003e\n \u003cp\u003ePorous silicon\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"7.603305785123967%\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"22.644628099173552%\"\u003e\n \u003cp\u003eKOH + IPA + H\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e\n \u003cp\u003e80*C for 3 minutes\u003c/p\u003e\n \u003cp\u003e(2014)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.223140495867769%\"\u003e\n \u003cp\u003eIsotropic Etching\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"24.793388429752067%\"\u003e\n \u003cp\u003eHF + HNO\u003csub\u003e3\u003c/sub\u003e + CH\u003csub\u003e3\u003c/sub\u003eCOOH/H\u003csub\u003e2\u003c/sub\u003eO (7:1:2) Time one minute\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e(15:2.5:1) Time 60 sec\u003c/p\u003e\n \u003cp\u003e(10:1:1) Time 60 minutes\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"16.198347107438018%\"\u003e\n \u003cp\u003eDouble distilled water\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"15.537190082644628%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e22% Conversion efficiency\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003e2.1 Etching mechanism and Etching of mc-Silicon wafers\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eMc-Silicon wafers with lower reflectance and lower recombination defects enhances the solar cell conversion efficiency. This can be obtained by chemical etching process with low cost. The wet chemical etching process is used for the removal of metal impurities from texturing of the silicon wafer and silicon materials. Acid texturing in a mc-Silicon wafer has been performed using a Hydrofluoric (HF) and Hydrogen peroxide (HNO\u003csub\u003e3\u003c/sub\u003e). The general etching mechanism is of two steps: (1) the SiO\u003csub\u003e2\u003c/sub\u003e is formed by nitric acid on the surface of the mc-Silicon wafer and then (2) SiO\u003csub\u003e2\u003c/sub\u003e is removed from the wafer surface via water-soluble complexes formed by HF [\u003cspan class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e\n\u003cp\u003eThe HNO₃ produces an SiO\u003csub\u003e2\u003c/sub\u003e layer\u003c/p\u003e\n\u003cp\u003e3Si\u0026thinsp;+\u0026thinsp;4HNO\u003csub\u003e3\u003c/sub\u003e \u0026rarr;3SiO\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;4NO\u0026thinsp;+\u0026thinsp;2H\u003csub\u003e2\u003c/sub\u003eO (1)\u003c/p\u003e\n\u003cp\u003eIt is dissolved by HF\u003c/p\u003e\n\u003cp\u003eSiO\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;6HF \u0026rarr;H\u003csub\u003e2\u003c/sub\u003eSiF\u003csub\u003e6\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;2H\u003csub\u003e2\u003c/sub\u003eO (2)\u003c/p\u003e\n\u003cp\u003eThe overall reaction is:\u003c/p\u003e\n\u003cp\u003e3Si\u0026thinsp;+\u0026thinsp;4HNO\u003csub\u003e3\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;18HF \u0026rarr; 3H\u003csub\u003e2\u003c/sub\u003eSiF\u003csub\u003e6\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;4NO\u0026thinsp;+\u0026thinsp;2H\u003csub\u003e2\u003c/sub\u003eO (3)\u003c/p\u003e\n\u003cp\u003eThe described mechanism of silicon dissolution is an electrochemical process on the silicon surface. In this process, holes (h+) were injected in the valence band of the semiconductor by HNO\u003csub\u003e3\u003c/sub\u003e at local cathodic sites, followed by the formation of a SiO\u003csub\u003e2\u003c/sub\u003e layer which is dissolved by HF at local anodic sites. The formation of SiO\u003csub\u003e2\u003c/sub\u003e layers was confirmed by the X-ray Photoelectron Spectroscopy studies [\u003cspan class=\"CitationRef\"\u003e14\u003c/span\u003e]. M. Steinert et al have [\u003cspan class=\"CitationRef\"\u003e15\u003c/span\u003e] studied silicon etching process using HNO\u003csub\u003e3\u003c/sub\u003e-rich HF/HNO\u003csub\u003e3\u003c/sub\u003e using XPS. The higher nitrite concentration reduces the etching rate slightly and lower nitrite concentration increases the etching rate linearly. Stirring is also increasing the etching rate. In this work, Hydrogen peroxide (H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e) was used instead of the nitric acid (HNO₃) and etching mechanism of these combinations is as follows:\u003c/p\u003e\n\u003cp\u003eThe H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e produces an SiO\u003csub\u003e2\u003c/sub\u003e layer\u003c/p\u003e\n\u003cp\u003e3Si\u0026thinsp;+\u0026thinsp;2H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e \u0026rarr;SiO\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;2H\u003csub\u003e2\u003c/sub\u003eO (4)\u003c/p\u003e\n\u003cp\u003eIt is dissolved by HF\u003c/p\u003e\n\u003cp\u003eSiO\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;6HF \u0026rarr;H\u003csub\u003e2\u003c/sub\u003eSiF\u003csub\u003e6\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;2H\u003csub\u003e2\u003c/sub\u003eO (5)\u003c/p\u003e\n\u003cp\u003eThe overall reaction is:\u003c/p\u003e\n\u003cp\u003eSi\u0026thinsp;+\u0026thinsp;2H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;6HF \u0026rarr; H\u003csub\u003e2\u003c/sub\u003eSiF\u003csub\u003e6\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;4H\u003csub\u003e2\u003c/sub\u003eO (6)\u003c/p\u003e\n\u003cp\u003eThe electrochemical process works just like conventional operations. The mc-Silicon wafers were cleaned in RCA-1 process at 10 minutes and the purpose of the cleaning was to remove the organic residue on the silicon wafer surfaces. It is placed in deionized water for a few seconds. Three set of chemicals with different volume and molar ratios were selected for etching process at room temperature and etching duration was 60 sec. The first set of etching chemical solution is HF-H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e-CH\u003csub\u003e3\u003c/sub\u003eCOOH with volume ratio of 3:2:2, second set of chemical solution is HF-H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e-KMnO\u003csub\u003e4\u003c/sub\u003e with volume and mole ratio of 3:2:0.2M, third set of chemical solution is HNO\u003csub\u003e3\u003c/sub\u003e-HF-H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e-KMnO\u003csub\u003e4\u003c/sub\u003e with volume and mole ratio of 3:2:2:0.2M. the combination of the HF and HNO\u003csub\u003e3\u003c/sub\u003e were optimized to remove residual surface strain.\u003c/p\u003e"},{"header":"Results And Discussion","content":"\u003cp\u003e\u003cstrong\u003e3.1 Reflectance of the mc-Silicon wafers\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe acid etching is sufficient to create isotropic surface texture of the wafer and to avoid the saw damages. The reflectance of the mc-Silicon textured surfaces are investigated from wavelength between 300\u0026ndash;1000 nm and shown in Figure.1. Three set of etched samples and reference silicon sample reflectance results were compared and shown in Figure.1. It is clearly seen that Set-2 (HF-H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e-KMnO\u003csub\u003e4\u003c/sub\u003e) chemical ratio reduces the reflectivity and the reduction up to 12.5 %. The Set- 2 chemical ratios in etching process strongly influences the effective reflectance. It has higher light absorbance compared to other chemical textured wafers since, the higher light absorbance leads to increase the solar cell efficiency. Kulesza et al., have optimized [\u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e] the time efficient texturization of mc-Silicon in the HF/HNO\u003csub\u003e3\u003c/sub\u003e solution and its effect on the optoelectonic parameters of the solar cells. The optimal chemical etching ratio has increased the solar cell efficiency up to 13.9 %.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.2 Crystalline structure of the grain orientation\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFigure. 2 shows the XRD pattern before and after chemically etching the samples. The crystalline structure of the wafers is investigated by using Analytical Empyrean X-ray diffractometer (XRD) with CuK\u003csub\u003e\u0026alpha;\u003c/sub\u003e radiation ((\u0026lambda;\u0026thinsp;=\u0026thinsp;1.5406 \u0026Aring;). The XRD pattern of silicon wafer shows the characteristic peak 28.40 and 56.10 (JCPDS file 271402) which correspond to (111) and (311). From the Fig. 2(a), HF: H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e: CH\u003csub\u003e3\u003c/sub\u003eCOOH etched wafer gives slight peak shift to a lower value of 2\u0026theta; in the (311) orientations. Sheng et al., [\u003cspan class=\"CitationRef\"\u003e18\u003c/span\u003e] have optimized the mixture solution of HF: HNO\u003csub\u003e3\u003c/sub\u003e: CH\u003csub\u003e3\u003c/sub\u003eCOOH with different time and concentration. From the Fig.\u0026nbsp;2(b), HF: H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e: KMnO\u003csub\u003e4\u003c/sub\u003e etched wafer gives higher intensity in the (111) orientations and lower light reflection. Zou et al., [\u003cspan class=\"CitationRef\"\u003e17\u003c/span\u003e] have done the alkali and Ag- MCCE etching of the (111) orientated mc-Silicon wafers expose dark appearance owing to the excellent light-trapping ability with Pyramid structure. From the Fig.\u0026nbsp;2(c), HF: H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e:HNO\u003csub\u003e3\u003c/sub\u003e: KMnO\u003csub\u003e4\u003c/sub\u003e etched wafer gives higher intensity in the (311) orientations and appear shiny. This refers to the higher inter planer spacing values of the atomic layers in silicon. In XRD results, the etched silicon wafers have given the higher intensity with slight peak shift in lower 2\u0026theta; angle side. The X-ray diffraction (XRD) result of HF: H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e:KMnO\u003csub\u003e4\u003c/sub\u003e indicates that the crystalline peak intensity of the etched mc-Silicon is higher than non- etched wafer and HF: H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e: CH\u003csub\u003e3\u003c/sub\u003eCOOH\u0026thinsp;=\u0026thinsp;3:2:2 etched results indicates the peak shift slightly to lower 2\u0026theta;. Moreover, the HF: H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e:KMnO\u003csub\u003e4\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;3:2:0.2M textured wafers have the advantages of lower reflectance and increased etching of the mc-Silicon wafer.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.3 Surface morphology of the mc-Silicon wafers:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe surface structures of the etched mc-Silicon wafers were investigated by using an optical microscope and SEM. Figure. 3, shows the changes occurred on the mc-Silicon wafers after etching by using an optical microscope at a resolution of 500X. Different etched patterns were produced by using three different chemical etching solution in the silicon surface. The comparison in results, the surface structures are considerably changed by using HF:H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e: KMnO\u003csub\u003e4\u003c/sub\u003e chemical solution. This chemical solution induces the small size uneven worm-like trenches and it has given lower reflectance compared to other two chemical solutions etched samples. The HF: H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e:HNO\u003csub\u003e3\u003c/sub\u003e: KMnO\u003csub\u003e4\u003c/sub\u003e chemical solution induces the medium size worm-like trenches structures. The HF: H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e: CH\u003csub\u003e3\u003c/sub\u003eCOOH chemical solution gives very small size worm-like trenches structures and it has given slightly lower reflectance compared to non-etched wafer.\u003c/p\u003e\n\u003cp\u003eAn optimization of the three different textured solutions were helpful to achieving lower reflectance. The SEM images of silicon wafer surface are shown in Figure.4. The saw damage has been removed and the mc-Silicon defects have disappeared by the etching process. Images show the formation of oval pits smoothened surface after etching the wafers at in HF/ H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e/CH\u003csub\u003e3\u003c/sub\u003eCOOH and HF/H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e/ KMnO\u003csub\u003e4\u003c/sub\u003e textured solutions. HF/ H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e/CH\u003csub\u003e3\u003c/sub\u003eCOOH gives 3\u0026ndash;6 \u0026micro;m size oval pits and HF/H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e/ KMnO\u003csub\u003e4\u003c/sub\u003e textured solutions gives 2\u0026ndash;4 \u0026micro;m size oval pits which are shown in figure.5. HF/H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e/ KMnO\u003csub\u003e4\u003c/sub\u003e results is reduced loss of weight compared to HF/ H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e/CH\u003csub\u003e3\u003c/sub\u003eCOOH textured solution and it is shown in Table.2.\u003c/p\u003e\n\u003cp\u003eKulesza et al have performed [\u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e] the time efficient texturization process with HF/HNO\u003csub\u003e3\u003c/sub\u003e solutions. They reported that this etching process is improving the optoelectronic parameters of the solar cell. Higher concentration of HF/ HNO\u003csub\u003e3\u003c/sub\u003e results in the formation of round pits with varying diameters. Optimized etching solution gives lower reflectance and higher efficiency. HF/H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e/ KMnO\u003csub\u003e4\u003c/sub\u003e textured solution led to formation of round pits in some places and MnO\u003csub\u003e4\u003c/sub\u003e is glazed. The solution HF/H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e/ KMnO\u003csub\u003e4\u003c/sub\u003e/ HNO\u003csub\u003e3\u003c/sub\u003e is causing more corrosion and it is shown in Figure.6. It reduces more weight and it is shown in Table.2. The HF/H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e/ KMnO\u003csub\u003e4\u003c/sub\u003e solution is showing the optimal oval pit structure with the lowest reflectance.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable. 2 Weight of wafer before and after chemical etching\u003c/strong\u003e\u003c/p\u003e\n \u003ctable border=\"1\" cellpadding=\"0\" cellspacing=\"0\" width=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"33.94342762063228%\"\u003e\n \u003cp\u003eChemical Etchant\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"23.62728785357737%\"\u003e\n \u003cp\u003eBefore etching (g)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"22.462562396006657%\"\u003e\n \u003cp\u003eAfter etching for 60 sec (g)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"19.966722129783694%\"\u003e\n \u003cp\u003eLoss of Weight (g)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"33.94342762063228%\"\u003e\n \u003cp\u003eHF + H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e + CH\u003csub\u003e3\u003c/sub\u003eCOOH\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"23.62728785357737%\"\u003e\n \u003cp\u003e0.14708\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"22.462562396006657%\"\u003e\n \u003cp\u003e0.14675\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"19.966722129783694%\"\u003e\n \u003cp\u003e0.00033\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"33.94342762063228%\"\u003e\n \u003cp\u003eHF + H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e + KMnO\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"23.62728785357737%\"\u003e\n \u003cp\u003e0.14903\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"22.462562396006657%\"\u003e\n \u003cp\u003e0.14890\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"19.966722129783694%\"\u003e\n \u003cp\u003e0.00013\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"33.94342762063228%\"\u003e\n \u003cp\u003eHF + H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e + HNO\u003csub\u003e3\u003c/sub\u003e + KMnO\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"23.62728785357737%\"\u003e\n \u003cp\u003e0.22467\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"22.462562396006657%\"\u003e\n \u003cp\u003e0.22420\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"19.966722129783694%\"\u003e\n \u003cp\u003e0.00040\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003e3.4 FTIR Studies for Analysing impurities\u003c/strong\u003e:\u003c/p\u003e\n\u003cp\u003eWet etching of the mc- Silicon wafers is a critical step in the solar cell making process. Optimized wet etching process improves the optical properties [\u003cspan class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e20\u003c/span\u003e]. The recombination properties of mc-Silicon solar cells are more complex owing to the structural defects, point defects and interaction among defects. Oxygen segregation in structural defects affects electrical activity and further complicates it. Pizzini et al., [\u003cspan class=\"CitationRef\"\u003e21\u003c/span\u003e] confirmed an oxygen segregation in the structural defects and they showed its influence on dislocation electrical activity. IR absorption spectroscopy is an important tool to study the nature of HF etched silicon. Reduction of oxidation is confirmed in three different textured solutions and it is shown in the IR spectrum of Figure.7. The peak position of Si\u0026ndash;O\u0026ndash;Si bonds at 1107 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and its reflectance are decreased in Figure.7. The combination of HF/ H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e/CH\u003csub\u003e3\u003c/sub\u003eCOOH etching solution significantly decreases the Si\u0026ndash;O\u0026ndash;Si reflectance. The combination of HF/H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e/ KMnO\u003csub\u003e4\u003c/sub\u003e reduces the Si\u0026ndash;O\u0026ndash;Si reflectance and C-H reflectance. The combination of HF/H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e/ KMnO\u003csub\u003e4\u003c/sub\u003e/ HNO\u003csub\u003e3\u003c/sub\u003e greatly decreases the Si\u0026ndash;O\u0026ndash;Si reflectance and C-H reflectance compared to the combination of HF/H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e/ KMnO\u003csub\u003e4\u003c/sub\u003e. But, the combination of HF/H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e/ KMnO\u003csub\u003e4\u003c/sub\u003e/ HNO\u003csub\u003e3\u003c/sub\u003e is causing more corrosion and it is more reflecting the light source.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eAcid texturization based on HF: H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e: (CH\u003csub\u003e3\u003c/sub\u003eCOOH or KMnO\u003csub\u003e4\u003c/sub\u003e or KMnO\u003csub\u003e4\u003c/sub\u003e:HNO\u003csub\u003e3\u003c/sub\u003e) mixture was demonstrated. The result of the two mixtures solutions HF: H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e: (CH\u003csub\u003e3\u003c/sub\u003eCOOH or KMnO\u003csub\u003e4\u003c/sub\u003e) were led to formation of round pits with different diameter in the single step and HF: H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e: KMnO\u003csub\u003e4\u003c/sub\u003e:HNO\u003csub\u003e3\u003c/sub\u003e texturization solution has given uneven surface. Silicon wafers engraved with HF: H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e: KMnO\u003csub\u003e4\u003c/sub\u003e have high optoelectronic parameters. HF: H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e: KMnO\u003csub\u003e4\u003c/sub\u003e solution gives high intensity in the (111) orientations and lower reflectance compared to other two solutions. It reduced the oxidation (Si\u0026ndash;O\u0026ndash;Si) reflectance and improved the electrical activity. The reduced surface reflectance and reduced oxidation were reducing the surface recombination loss and increasing the short circuit current (J\u003csub\u003esc\u003c/sub\u003e). In solar cell making process, HF: H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e: KMnO\u003csub\u003e4\u003c/sub\u003e based textured wafer can give higher conversion efficiency.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eFunding\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the Department of science and technology Government of India (Order No. DST/TMD/CERI/RES/2020/7(c)dated on 31/12/2020).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflicts of interest/Competing interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and material\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCode availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026apos; contributions\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll the authors are equal contribution in the manuscript.\u003c/p\u003e\n\u003col\u003e\n \u003cli\u003eMadhesh Raji - Writing - Original Draft\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eKesavan Venkatachalam- Formal Analysis, Investigation,\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eSrinivasan Manikkam- Supervision \u0026nbsp;\u003c/li\u003e\n \u003cli\u003eRamasamy Perumalsamy - review \u0026amp; editing\u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003e\u003cstrong\u003eDisclosure of potential conflicts of interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResearch involving Human Participants and/or Animals\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the Department of science and technology Government of India (Order No. DST/TMD/CERI/RES/2020/7(c)dated on 31/12/2020).\u0026nbsp;\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eCompliance with ethical standards\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study involving human participants were in accordance with the ethical standards of the institutional and/or national research committee.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eInformed consent was obtained from all individual participants included in the study\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for Publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eConsent for publication was obtained from all individual participants included in the study\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eYing Z, Liao M, Yang X, Han C, Li J, Li J, Li Y, Gao P, Ye J (2016) High-performance black multicrystalline silicon solar cells by a highly simplified metal-catalyzed chemical etching method. 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Journal of Sustainability Science Management 15(2):6\u0026ndash;11\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMartin PM (2010) Surface preparation for film and coating deposition processes Handbook. of Deposition Technologies for Films and Coatings\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003e19Arias M, Brice\u0026ntilde;o M, Marzo A, Z\u0026aacute;rate A (2019) Optical and electrical properties of silicon solar cells by wet chemical etching. J Chil Chem Soc 64(1):4268\u0026ndash;4274\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePizzini S, Gandolfi A, Farina S, Branciforti M (1990) LBIC analysis of the electrical activity of dislocations in CZ silicon. Materials Science Engineering: B 7(1\u0026ndash;2):69\u0026ndash;82\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Acid and base Texturization, Multicrystalline silicon, Light trapping, Solar cell","lastPublishedDoi":"10.21203/rs.3.rs-934808/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-934808/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe aim of this work is to improve the optical properties in the multi-crystalline silicon (mc-Si) by acid texturization.\u0026nbsp;Generally, HF and HNO\u003csub\u003e3 \u003c/sub\u003eare using the mc-Si wafer acid texturization process and it is toxic chemical acids. In this work, H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2 \u003c/sub\u003eis used instead of HNO\u003csub\u003e3\u003c/sub\u003e because of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2 \u003c/sub\u003eless toxic chemical compared to HNO\u003csub\u003e3\u003c/sub\u003e. In this work, we have used the different types of chemical acids in different ratios for etching. Here, we have used HF: H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e: CH\u003csub\u003e3\u003c/sub\u003eCOOH=3:2:2, HF: H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e: KMnO\u003csub\u003e4\u003c/sub\u003e =3:2:0.2 M and HF: H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e: HNO\u003csub\u003e3\u003c/sub\u003e: KMnO\u003csub\u003e4\u003c/sub\u003e =3:2:2:0.2M for etching with the etching time of 60 sec. The HF: H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e: KMnO\u003csub\u003e4\u003c/sub\u003e =3:2:0.2M gives the better results as obtained from optical microscope, UV- Visible reflectance studies and X-ray diffraction (XRD) studies. The etched mc-Silicon wafer surface was analyzed by the optical microscope and Scanning Electron Microscope (SEM). The FTIR results indicate the reduction of oxidation in the etched samples. Moreover, the HF: H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e: KMnO\u003csub\u003e4\u003c/sub\u003e =3:2:0.2M textured wafers have the advantages of lower reflectance and increased etching of the mc-Silicon wafer.\u003c/p\u003e","manuscriptTitle":"Chemical Texturing Used to Reduce The Reflectance of the Multi-Crystalline Silicon Wafer For Improving Optical Properties and Solar Cell Efficiency","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2021-10-15 16:13:23","doi":"10.21203/rs.3.rs-934808/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"67cb1dd7-fd21-4f08-8feb-c17deab21f93","owner":[],"postedDate":"October 15th, 2021","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":7868703,"name":"Electronic Materials and Devices"}],"tags":[],"updatedAt":"2021-12-23T21:14:35+00:00","versionOfRecord":[],"versionCreatedAt":"2021-10-15 16:13:23","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-934808","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-934808","identity":"rs-934808","version":["v1"]},"buildId":"J0_U0BvcaRcwD8yVFaRlm","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}