Multifunctional Molecular Bridge for Synergistic Interfacial Regulation Toward Efficient Perovskite Solar Cells

The performance of self‐assembled monolayers (SAMs) in perovskite solar cells (PSCs) is frequently hindered by molecular aggregation, poor interfacial wettability, and high buried‐interface defect density. Herein, we introduce 4‐carboxyphenylboronic acid (CPBA) as a multifunctional molecular bridge to synergistically engineer the buried interface through co‐assembly with Me‐4PACz. CPBA anchors its carboxylic groups onto the NiO x substrate, refining SAM morphology and enhancing wettability, while its exposed boronic acid (‐B(OH) 2 ) groups multifunctionally passivate perovskite interfacial defects via Lewis acid‐base coordination and hydrogen bonding, and its strong molecular dipole optimizes energy‐level alignment for efficient hole extraction. Moreover, CPBA modulates perovskite crystallization kinetics, yielding high‐quality films with enlarged grains and reduced grain‐boundary defects. Consequently, CPBA‐modified PSCs achieved a power conversion efficiency of 26.02%, with an open‐circuit voltage of 1.191 V and a fill factor of 83.67%. Unencapsulated devices maintained 91% of their initial efficiency after 1800 h of storage and 88% after 1300 h of thermal aging at 65°C. This molecular‐bridging strategy provides a robust pathway toward efficient and durable perovskite photovoltaics.