A comprehensive theoretical investigation of lead-free mixed antimony-bismuth halide double perovskite (Cs₂AgBi₀.₇₅Sb₀.₂₅Br₆) solar cell using SCAPS-1D

Abstract The environmental hazards associated with lead (Pb)-based double perovskite solar cells (DPSCs) have intensified the search for efficient, lead-free alternatives. The toxicity of Pb in efficient double perovskite solar cells presents significant environmental challenges, limiting large-scale manufacturing. This study presents a comprehensive theoretical investigation of a Pb-free mixed antimony-bismuth halide double perovskite, Cs₂AgBi₀.₇₅Sb₀.₂₅Br₆, as a promising absorber material for next-generation, non-toxic solar cells. Using the SCAPS-1D solar cell capacitance one-dimensional simulator, we systematically optimize device architecture by varying the thickness and material composition of electron transport layers (ETLs) and hole transport layers (HTLs), as well as the absorber layer properties. Key parameters such as absorber doping concentration, interface and bulk defect densities, and absorber bandgap are correlated with photovoltaic performance metrics including short circuit current ( $${J}_{sc}$$ J sc ), open circuit voltage ( $${V}_{oc}$$ V oc ), power conversion efficiency (PCE) and fill factor (FF). The simulation outcomes indicate that the most suitable choices for the optimized ETL is Cd0.5Zn0.5S and HTL is CuSCN. Further enhancements are demonstrated by tuning temperature, managing parasitic resistances, and adjusting the absorber’s dielectric permittivity. The study also highlights the critical influence of the back electrode work function, with carbon electrodes yielding the highest efficiency. The optimized device configuration FTO/Cd₀.₅Zn₀.₅S/Cs₂AgBi₀.₇₅Sb₀.₂₅Br₆/CuSCN/C achieves a simulated $${V}_{oc}$$ V oc of 1.22 V, $${J}_{sc}$$ J sc of 20.23 mA/cm2, FF of 88.88%, and a PCE of 21.99%. The favorable optical and physical properties observed in Cs2AgBi0.75Sb0.25Br6 showcase its potential, encouraging further research into hybrid halide double perovskites for photovoltaic applications and other optoelectronic fields. These findings underscore the significant potential of Cs₂AgBi₀.₇₅Sb₀.₂₅Br₆ for high-performance, lead-free DPSCs, paving the way for environmentally sustainable and efficient photovoltaic technologies.