Interfacial interactions and properties of lead oxysalts passivated MAPbI₃ perovskites from first-principles calculations

The stability issue of organohalide lead perovskites in humid conditions is a key challenge to their commercial application in the photovoltaic field. In this study, density functional theory (DFT) and non-equilibrium Green's function (NEGF) calculations were employed to clarify the interfacial interactions and properties between the perovskite and its lead oxysalt passivation layers. It was found that internally-generated electric fields form at the interfaces and the photoexcited electrons transfer from the perovskite to the lead oxysalts side. The strong orbital hybridization at the interface accounted for electron-hole excitations, interface reconstruction, electron redistribution, and stability enhancement. Most importantly, the lead oxysalt-capped MAPbI(3) was found to be capable to withstand the reaction with atomic oxygen through passivating the under-coordinated anions. Theoretical studies reveal that the introduction of lead oxysalts can effectively protect MAPbI(3) from erosion. These findings illustrate the passivation mechanism of lead oxysalts to stabilize the efficiency of perovskite photovoltaic devices.