Revisiting the exposed surface characteristics on the stability and photoelectric properties of MAPbI3.

In this work, the stability and photoelectric properties of the MAI-terminated and PbI2-terminated of MAPbI3 (001) were thoroughly investigated using density functional theory calculation. To study the stability of exposed surface, adsorption energy of water molecules, ab initio molecular dynamics (AIMD), mean square displacement (MSD) and X-ray diffraction (XRD) were calculated. MSD of PbI2-terminated surface is greater by two orders of magnitude compared to MAI-terminated surface. For the photoelectric properties of MAPbI3, the bandgap, absorption coefficients, joint density of states (JDOS) and dielectric constants were investigated. The inhibitory effect of water on the photoelectric performance for PbI2-terminated surface is more significant than that of MAI-terminated surface. Although the photoelectric properties of water molecules adsorption on MAI-terminated surface is basically unchanged, the diffusion of water molecules reduces the photoelectric properties of MAPbI3. Overall, the stability and photoelectric properties of MAI-terminated surface are superior to PbI2-terminated surface. Therefore, we advocate paying attention to the exposed surface of MAPbI3 during the thin film production process and adjusting synthesis parameters to prepare MAI-terminated surface dominated thin film, which should substantially improve the performance of MAPbI3 in the application.