Can Pb‐Free Halide Perovskites be Realized by Incorporating the Neutral or Anionic Molecule?

Abstract Exploring Pb‐free perovskite alternatives is a major challenge in the current photovoltaic field. Direct substitution of Pb with a non‐toxic cation usually lowers the structural or electronic dimension, thereby impacting the excellent photovoltaic properties of halide perovskites. In this work, Pb‐free halide perovskites by incorporating the anionic or neutral molecules on the A‐site of the perovskite lattice and assess the photovoltaic potential by first‐principles calculations is constructed. The Pb‐free perovskite CH 4 BiCl 3 is predicted to have a direct bandgap within the optimal range for photovoltaic application. Due to the same electronic configuration of B‐site Bi 3+ and Pb 2+ cations, the CH 4 BiCl 3 exhibits a similar electronic band structure with Pb‐based halide perovskites. The calculated effective masses and exciton binding energy of electron and hole indicate the high mobility of photogenerated carriers of CH 4 BiCl 3 . The excellent photovoltaic performance is demonstrated by calculating the spectroscopic limited maximum efficiency, which shows an efficiency of 30.9% for a typical thickness of 0.5 µm. The structural stability of cubic perovskite CH 4 BiCl 3 is further evaluated by computing the decomposition energy and ab initio molecular dynamics simulation, demonstrating the thermodynamic stability of CH 4 BiCl 3 at room temperature. These results can be a useful guide for exploring novel Pb‐free perovskite materials.