Blocked Proton-Coupled Electron Transfer Stabilizes Buried Interface in Air-Processed Inverted Perovskite Solar Cells

Nickel oxide/self-assembled monolayer (NiO_x/SAM) composites have emerged as benchmark hole transport layers for high-efficiency inverted perovskite solar cells (PSCs). However, the coupled interfacial degradation mechanism in NiO_x/SAM/perovskite systems remains ambiguous, which still restricts device stability. In this study, we identify a previously unrecognized proton-coupled electron transfer (PCET) induced buried-interface degradation pathway, in which the protons released from SAM accelerates the redox reaction between NiO_x and I^-, especially under high-temperature and UV-irradiation operation conditions. To block this coupled degradation pathway, we incorporate 1-methylimidazole into the SAM, which suppresses the proton transfer through capturing the protons and impedes the electron transfer through reducing the formation of I^- vacancies, thereby blocking the interfacial PCET process from both perspective of proton and electron. Besides, the proton-capture treatment by 1-methylimidazole can enhance the anchoring of SAM at the NiO_x substrate, which promotes the interface hole transfer and also contributes to the interfacial stability. Consequently, the resulting PSCs, fabricated in ambient air, achieved a power conversion efficiency exceeding 26.3% with an enhanced operational stability by retaining >90% initial efficiency after 2000 h of maximum power point tracking at ∼50°C.