Eco-friendly bismuth halide chalcogenide perovskites for solar energy harvesting

The quest to eliminate lead (Pb) content in perovskite photovoltaic materials has significantly shifted focus towards identifying viable Pb-free alternatives. This study provides a comprehensive theoretical investigation of CH₃NH₃BiI₂Se and CH₃NH₃BiI₂S as Pb alternative candidates. Density Functional Theory (DFT) calculations and the solar cell capacitance simulator (SCAPS) were used. The DFT analysis reveals that both CH₃NH₃BiI₂Se and CH₃NH₃BiI₂S possess indirect band gaps of 1.35 eV and 1.39 eV, respectively. CH₃NH₃BiI₂Se demonstrates a higher absorption coefficient, stronger absorption in the UV-visible regions, a broader absorption spectrum and better charge carrier mobilities compared to CH₃NH₃BiI₂S. CH₃NH₃BiI₂Se and CH₃NH₃BiI₂S based solar cells which show 24.06% and 21.85% power conversion efficiencies (PCEs), respectively. This study emphasizes the potential of CH₃NH₃BiI₂Se as a promising bismuth mixed halide chalcogenide compound for the development of sustainable perovskite solar cells. The findings provide a foundation for the guided design of novel bismuth chalcogenide compounds for optoelectronic applications and experimental studies.