Mechanisms of Oxygen Passivation on Surface Defects in MAPbI₃ Revealed by First-Principles Study

Perovskite materials have shown ultrasensitivity to atmospheres especially to O₂, which is due to the passivation effect of the surface defects. Identification of the chemical nature of the surface defects is thus of crucial importance for fundamental understanding of these materials, which is extremely difficult by experimental characterization. In this work, we systematically studied the adsorption of O₂ on all possible crystal defects on the (001) surface with three different possible terminations in CH₃NH₃PbI₃. High-precision electronic structures of these defects were obtained by employing the Heyd–Scuseria–Ernzerhof hybrid functional with spin-orbit coupling. Based on the oxygen effect, we finally identify that the vacancy defects of I and the interstitial defects of Pb are the two main surface defects responsible for the charge-carrier trapping. Our results provide suggestions for better controlling the properties of these materials, optimizing the fabrication processes of the devices, and identifying the nature of defects in other perovskite materials.