Theoretical design of 2D hybrid lead-free halide perovskites for photovoltaic applications

Two-dimensional hybrid halide perovskites are emerging as promising candidates for optoelectronic applications due to their enhanced environmental stability, tunable structure and bandgap, and high quantum efficiency. However, the risk of toxic lead leakage and inherent instability remain significant challenges for the large-scale commercialization of organic-inorganic halide perovskites. In this study, we conducted first-principles investigations into the optoelectronic properties of a series of two-dimensional hybrid lead-free halide perovskite materials, BAMX₂Y₂ (BA = C₄H₉NH₃⁺; M = Sb and Bi; X, YCl, Br, and I) and assessed their photovoltaic performances based on drift-diffusion simulations. The antimony-based compounds BASbI₄, BASbCl₂I₂, and BASbBr₂I₂ are predicted to have desired direct bandgaps within the optimal range and exhibit strong absorption capacity for visible light. Based on these favorable properties, we simulated the photovoltaic performance of thin-film solar cells based on these materials using the SCAPS-1D code, achieving high power conversion efficiencies of 26.15 %, 22.91 %, and 22.31 %, respectively. These results suggest that BASbI₄, BASbBr₂I₂, and BASbCl₂I₂ could serve as potential alternatives to lead-based halide perovskites in photovoltaic devices.