Generation and Clearance of Superoxide Radicals at Buried Interfaces of Perovskites with Different Crystal Structures.

One of the most notorious issues with classic perovskite (MAPbI) is its rapid degradation caused by generating superoxide radicals (O ) on its surface under light and oxygen environments (light/O). The differences in O generation rate and tolerance to O among perovskite with different structures are pending. For the first time it is validated through solid-electron paramagnetic resonance (EPR) that MAPbI and CsFAMAPbI (PVSK) crystals can generate O in an air atmosphere. The rapid degradation of perovskite buried interfaces caused by O dominates the nonexposed air aging process of SnO-based perovskite film, and the degradation rate of MAPbI film is faster than that of PVSK film. The fullerene pyridine derivatives (COPD), which function as a buffer layer between SnO and PVSK to scavenge O and prevent degradation at the buried interface of the PVSK film, reduce the density of defect states, and accelerate the transmission of photogenerated electrons. The photoelectric conversion efficiency (PCE) of perovskite solar cells (PSCs) optimizes with COPD increased from 21.15% to 23.11% while significantly improving the stability in light/O. This work reveals the hidden degradation of perovskite-buried interfaces caused by O and explores efficient ways for perovskite to resist O .