Design and Numerical Analysis of Thin Film Solar Cells Based on Cu₂ZnSn (SₓSe₁₋ₓ)₄ with SnO₂ TCO and ZnS Buffer

Due to their earth-abundance, direct and adjustable bandgap in the range of visible light, and lower fabrication cost on large areas, Cu2ZnSn(SxSe1-x)4 semiconductors, commonly known as kesterite, are gaining recognition as potential materials for affordable, environment‐friendly, and high‐efficiency thin‐film photovoltaics. In this work, we numerically investigated the performance parameters of a single-heterojunction solar cell using Cu2ZnSnS4 (CZTS) / Cu2ZnSnSe4 (CZTSe) absorber layer and ZnS buffer layer, with SnO2 transparent conducting oxide (TCO) under a range of operating conditions and cell parameters. Maximum efficiency of 20.68% was obtained for a 5.5 µm absorber layer with 0.01 µm ZnS buffer layer for Cu2ZnSnSe4 solar cell, and 22.86% was obtained for a 6 µm thick Cu2ZnSnS4 absorber layer with 0.03 µm ZnS layer at room temperature and standard irradiance. The increase of irradiance to thrice the standard value led to 1% and 5% increase in efficiency for CZTS and CZTSe cells, respectively. Efficiency increased by 39% and 6.6% when the front surface was textured at an angle of 90° for CZTS and CZTSe cells, respectively. The CZTS and CZTSe based solar cells with optimized thickness and 90° textured front surface with three times the standard irradiation, showed 25.59 % and 21.52 % efficiency with open circuit voltage 1045 mV and 579.4 mV and short circuit current 85.84 mA/cm2 and 140.7 mA/cm2, respectively. The proposed architecture in this study will help produce next-generation solar cells that are both economical and energy-efficient.