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

ABSTRACT 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.