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

One of the most notorious issues with classic perovskite (MAPbI₃) is its rapid degradation caused by generating superoxide radicals (O₂ ^•-) on its surface under light and oxygen environments (light/O₂). The differences in O₂ ^•- generation rate and tolerance to O₂ ^•- among perovskite with different structures are pending. For the first time it is validated through solid-electron paramagnetic resonance (EPR) that MAPbI₃ and Cs_0.175FA_0.75MA_0.075PbI₃ (PVSK) crystals can generate O₂ ^•- in an air atmosphere. The rapid degradation of perovskite buried interfaces caused by O₂ ^•- dominates the nonexposed air aging process of SnO₂-based perovskite film, and the degradation rate of MAPbI₃ film is faster than that of PVSK film. The fullerene pyridine derivatives (C₆₀OPD), which function as a buffer layer between SnO₂ and PVSK to scavenge O₂ ^•- 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 C₆₀OPD increased from 21.15% to 23.11% while significantly improving the stability in light/O₂. This work reveals the hidden degradation of perovskite-buried interfaces caused by O₂ ^•- and explores efficient ways for perovskite to resist O₂ ^•-.