Self-Passivation at the SnO2/Perovskite Interface

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 (VIact). Unlike the typical defects of accelerating the charge recombination and reducing efficiency, this distinctive VIact facilitates charge transfer and decelerates nonradiative recombination by passivating the potential trap states. Additionally, the benign VIact 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, VIact 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.