Design and Performance Evaluation of Lead-Free Cesium Gold Bismuth Chloride Perovskite Solar Cells with Tunable Transport Layers

All-inorganic double perovskites, such as cesium gold bismuth chloride (Cs2AuBiCl6), have emerged as stable and environmentally friendly alternatives to lead-based perovskites. The Solar Cell Capacitance Simulator (SCAPS-1D) was used in this study to simulate a planar perovskite solar cell using absorber Cs2AuBiCl6. To enhance the device performance, different electron transport materials (ZnSe, [6,6]-phenyl C61 butyric acid methyl ester (PC60BM), SrTiO3 (STO), CeO2, CdS, and indium gallium zinc oxide (IGZO)) and hole transport materials (TiS2, TaS2, NiS2, HfS2, CuSbS2, and MoS2) were investigated. The work systematically examines the influence of material selection on photovoltaic characteristics, including current density–voltage (J–V) and quantum efficiency (QE) responses, layer thickness, defect states, interface defects, and doping concentration. Among the evaluated structures, the configuration with ZnSe as the electron transport material (ETM) and NiS2 as the hole transport material (HTM) demonstrated the highest performance, yielding a Voc of 0.7669 V, Jsc of 42.679 mA/cm2, a fill factor (FF) of 81.13%, and a power conversion efficiency (PCE) of 26.56%. Furthermore, the optimized double perovskite achieves competitive efficiencies with TiS2 reaching 26.03%, TaS2 reaching 25.83%, HfS2 reaching 25.85%, CuSbS2 reaching 19.47%, and MoS2 reaching 26.20%. These findings highlight Cs2AuBiCl6 as a promising lead-free absorber for achieving high efficiency, stability, and sustainability in next-generation perovskite solar cells.