Metal Halide-Based Adsorption and Substitution at Halide Perovskite Surfaces: Study of CuBr2/CH3NH3PbI3

Metal halides have been incorporated in halide perovskite materials and demonstrated to effectively improve the perovskite solar cell performance. However, the detailed atomistic interactions between the metal halides and the halide perovskite materials, pertinent to the adsorption and substitution at the halide perovskite surfaces, remain to be elucidated. In this manuscript, we theoretically investigate the interaction between a representative metal halide additive CuBr2 and the halide perovskite materials CH3NH3PbI3, considering both adsorption and substitution scenarios of the metal halide on different perovskite surface terminations. The calculations suggest that the metal halides are capable of either adsorption or substitution at the perovskite surface, resulting in non-negligible impacts on the electronic and optical properties of the halide perovskite systems. Both adsorption and substitution are advised to be addressed in the additive/perovskite modeling process. The present study facilitates the fundamental understanding of additive and surface engineering of halide perovskite materials.