Numerical modeling to enhance the efficiency of experimentally fabricated Sb₂Se₃-based solar cell

Remarkable optical and electrical characteristics make antimony selenide (Sb₂Se₃) a potential absorber layer for heterojunction solar cells. In this work, a novel heterojunction Sb₂Se₃-based thin film solar cell using non-toxic tin sulfide (SnS₂) as buffer layer instead of toxic cadmium sulfide (CdS) is designed utilizing Solar Cell Capacitance Simulator in one-dimension (SCAPS-1D). To validate the simulation model, the results of experimentally fabricated glass/SnO₂:F(FTO)/CdS/Sb₂Se₃/Au solar cell structure with efficiency of 5.17% is reproduced in SCAPS. SnS₂ buffer layer provides better band alignment with the Sb₂Se₃ absorber than CdS buffer layer and improves efficiency. The device performance is optimized by altering thickness, doping concentration, bandgap, defect density, interface defect and capture cross-section for the different layers. The maximum efficiency obtained for the optimized FTO/SnS₂/Sb₂Se₃/Au photovoltaic structure is 12.31% when the Sb₂Se₃ absorber, SnS₂ buffer and FTO layer thickness are optimized at 0.4 µm, 0.03 µm, and 0.1 µm respectively and their doping are optimized at 10¹⁶ cm^-3, 10¹⁸ cm^-3 and 10²⁰ cm^-3 respectively. Addition of tin monosulfide (SnS) as back surface field (BSF) layer boosts the efficiency by decreasing carrier recombination and preventing electrons from reaching back contact due to proper band alignment formed at SnS/Sb₂Se₃ interface. The efficiency of 24.86% with V _OC = 0.94 V, J _SC = 31.98 mA cm^-2, and FF = 83.09% is obtained for the proposed FTO/SnS₂/Sb₂Se₃/SnS/Au photovoltaic structure with SnS BSF layer at thickness of 0.2 µm and doping of 10²⁰ cm^-3. Moreover, the impacts of operating temperature, parasitic resistance and back contact work function on the performance parameters of the designed solar cell are analyzed. These findings indicate that non-toxic SnS and SnS₂ can be utilized as a promising BSF and buffer layer respectively to produce cost-effective, environmental friendly and extremely efficient Sb₂Se₃-based thin film solar cell.