A new exploration of the impact of different wide-bandgap S-chalcogenides Electron Transport Layers (ETL) on the performance of BaSi₂-based solar cells

Harvesting green energy from the solar spectrum requires an alternative semiconductor material to replace the traditionally used n-type Cadmium Sulfide (CdS) buffer layer in BaSi₂-based photovoltaics. This manuscript presents the study of BaSi₂-based single-junction solar cells using three different wide-bandgap S-chalcogenide Electron Transport Layers (ETL): Zn(O,S), SnS₂, and WS₂. Initially, structural, electronic, and optical characteristics were investigated using density functional theory (DFT), revealing optimal electronic band gaps of 1.3 eV for the BaSi₂ absorber and 2.14 eV for the WS₂ buffer layer. The optical properties, including dielectric function (ε), refractive index (n), conductivity (σ), absorption (α), reflectivity (R), and loss function (L) of the BaSi₂ absorber and WS₂ buffer layers, were thoroughly analyzed. Furthermore, a systematic study using the SCAPS-1D Simulator examined the impact of various physical parameters, such as layer thickness, doping concentration, and bulk and interface defect densities, on photovoltaic (PV) performance. The highest photoconversion efficiency (PCE) of 22.2% was achieved with the WS₂ buffer, with a V_OC of 0.76 V, a J_SC of 35.23 mA/cm², and a FF of 82.40%. Although, the PCE were found of 17% and 17.1% due to Zn(O,S) and SnS₂ buffer. This comprehensive study highlighted the strong potential of the WS₂ buffer layer for designing BaSi₂-based solar cells and outlined a pathway for fabricating green, high-efficiency, and economical BaSi₂-based heterojunction thin-film solar cells. Additionally, it explored the potential use of quantum dots as intermediate layers to enhance light absorption and carrier extraction in BaSi₂-based solar cells.