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.