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.