Optimization of Low-Cost Zinc Sulfide Antireflection Coating by Eco-Friendly Route for Large Area Multi-Crystalline Silicon Solar Cells

This study primarily aims at investigating the performance of large-area multi-crystalline silicon (mc-Si) solar cells through the optimization of zinc sulfide (ZnS), a cost-effective thin film antireflection coating (ARC) deposited using chemical bath deposition (CBD) technique. The films are deposited on NaOH-NaOCl polished mc-Si solar cells using a complexing agent, tri-sodium citrate that is non-toxic in nature. The antireflection properties of the films are optimized by varying the molar concentration of tri-sodium citrate, the deposition time, and the angle of substrate tilt during deposition. The molar concentration of tri-sodium citrate is varied from 0.10 to 0.40 M. The atomic force microscopy (AFM) analysis reveals that the film deposited at 0.30M tri-sodium citrate for one hour exhibits a uniform surface morphology with a root mean square (RMS) roughness of 2.97 nm. The optimized film demonstrates good uniformity (standard deviation <1), a high deposition rate, a refractive index of 2.35 and a minimum reflectance of 4% on mc-Si. Energy dispersive X-ray Analysis (EDAX) indicates that the stoichiometry of the optimized film is 0.71 which is very close to that of ZnS films deposited by other methods. The formation of the ZnS film is further confirmed by Fourier transform infrared spectroscopy (FTIR). Successful fabrication of solar cells with a power conversion efficiency of approximately 13.5% is demonstrated using the optimized ZnS ARC. This low-cost and eco-friendly CBD approach for ZnS thin-film deposition shows strong potential for large area mc-Si solar cell applications.