Adsorption and Diffusion of Halogen Gas Molecules on CH 3 NH 3 PbI 3 Halide Perovskite Surfaces

The interactions between gas molecules and halide perovskite materials are important considerations for understanding the halide-perovskite-based devices. In this manuscript, we employ first principles calculations to investigate the adsorption of halogen gas molecules (I2, Br2, and Cl2) on the prototypical halide perovskite CH3NH3PbI3 surfaces. The calculations show that the halogen gas molecules reside stably on the halide perovskite surfaces with different terminations. The adsorption of the halogen gases presents additional empty states near the conduction band of the halide perovskite materials, altering the surface charge transfer properties. In addition, the diffusion of the halogen gas into the halide perovskite surfaces reveals a dissociation tendency of the halogen molecules in the halide perovskite materials. This study contributes to fundamental understanding of adsorption processes involving halide perovskite materials.