Bifunctional Buried Interface Modification Strategy for Stable and Efficient Perovskite Solar Cells

Interfacial instability caused by formamidinium (FA + ) deprotonation at the NiO X /self-assembled monolayer (SAM)/perovskite buried interface remains a major obstacle to achieving both high efficiency and long-term stability in inverted perovskite solar cells (PSCs). Here, a bifunctional hybrid-SAM strategy is developed for buried-interface stabilization by introducing 2-bromopyridine-5-boronic acid (Br-N-BOH) into [2-(3,6-dimethoxy-9 H -carbazol-9-yl)ethyl]phosphonic acid (Me-4PACz). Br-N-BOH stabilizes FA + through two cooperative effects: strong hydrogen-bonding interactions that suppress cation deprotonation and enhanced intermolecular interactions that improve SAM uniformity and reduce locally exposed perovskite/NiO X contact. These combined effects strengthen the chemical robustness of the buried interface. The resulting interfacial optimization further suppresses nonradiative recombination and facilitates charge extraction through a more homogeneous SAM distribution and an optimized work function. As a result, the inverted PSCs achieve a power conversion efficiency of 25.4%, together with substantially improved operational and thermal stability. This work establishes an effective molecular strategy for buried-interface stabilization in efficient and stable inverted PSCs.