Multifunctional Interfacial Passivation via Cooperative Coordination and Hydrogen Bonding for Highly Efficient and Stable Inverted Perovskite Solar Cells

ABSTRACT Interfacial defects and unfavorable energy‐level alignment at the perovskite/electron transport layer (ETL) interface remain critical bottlenecks that constrain the efficiency and operational stability of inverted perovskite solar cells (PSCs). Here, a multifunctional interfacial passivation strategy based on 4,6‐dihydroxy‐2‐mercaptopyrimidine (TBA) is developed to simultaneously regulate defect states and interfacial energetics. Benefiting from its dual hydroxyl and thiol functionalities, TBA establishes strong multidentate coordination with undercoordinated Pb 2+ ions while simultaneously forming robust hydrogen bonds with formamidinium (FA + ) cations, enabling site‐selective anchoring at the perovskite surface. This cooperative coordination–hydrogen‐bonding interaction effectively reduces interfacial trap density, suppresses nonradiative recombination, and optimizes energy‐level alignment at the perovskite/ETL interface. Consequently, inverted PSCs incorporating TBA achieve a champion power conversion efficiency (PCE) of 25.31%, accompanied by an enhanced open‐circuit voltage and negligible J–V hysteresis. Furthermore, TBA‐modified devices exhibit substantially improved thermal and operational stability, retaining 90.4% of their initial efficiency after 1000 h of maximum power point tracking at 45°C under a nitrogen atmosphere. This work highlights the effectiveness of multifunctional molecular passivation for simultaneously advancing the efficiency and durability of inverted perovskite solar cells.