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

Perovskite materials have shown ultra-sensitivity to atmospheres especially to O2, which is due to 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. Base on the oxygen effect, we finally identify 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 as well as identifying...