Self-Passivation at the SnO2/Perovskite Interface

Abstract

Interfaces are crucial to the performance of solar cells, as they significantly affect charge transport. Using density functional theory and nonadiabatic molecular dynamics simulations, we reveal a self-passivation mechanism at the SnO₂/CH₃NH₃PbI₃ interface to enhance the stability and efficiency of the device, which is mainly attributed to a benign iodine vacancy (V_Iact). Unlike the typical defects of accelerating the charge recombination and reducing efficiency, this distinctive V_Iact facilitates charge transfer and decelerates nonradiative recombination by passivating the potential trap states. Additionally, the benign V_Iact at the interface reduces structural distortion and suppresses electron–vibration interactions, which in turn, extends the charge carrier lifetime and enhances the electron injection. Furthermore, V_Iact exhibits both thermodynamic and kinetics stability. Our findings rationalize the high performance of SnO₂-based perovskite solar cells and highlight the importance of the defect self-passivation strategy in optimizing interfacial properties for enhanced solar cell efficiency.