Multi-Bonding Molecular Interface Bridges Enable Synergistic Defect Passivation, Strain Relaxation, and Accelerated Electron Extraction in Perovskite Solar Cells

Buried interfacial defects, residual strain, and unfavorable energy-level alignment collectively limit charge extraction and induce nonradiative recombination losses in high-performance perovskite solar cells (PSCs). Here, we report a multifunctional molecular-bridge strategy based on 2-amino-3-hydroxybutanoic acid (AHBA) for simultaneous regulation of the SnO₂/perovskite buried interface. Benefiting from its synergistic amino, hydroxyl, and carboxyl functional groups, AHBA establishes a cross-linked interfacial interaction network through coordinated bonding and hydrogen-bonding interactions, enabling bilateral defect passivation, interfacial strain relaxation, and accelerated electron extraction. The resulting interface exhibits reduced trap density, optimized energy-level alignment, enhanced crystallographic ordering, and suppressed nonradiative recombination. Ultrafast transient absorption spectroscopy reveals a charge-carrier extraction time of only 3.5 ps, demonstrating markedly accelerated interfacial charge transfer. The reconstructed electronic landscape further promotes efficient carrier collection and long-range transport, leading to a champion power conversion efficiency of 26.32% with a fill factor of 85.69% and significantly reduced hysteresis. In addition, the target sample devices retain over 90% of their initial efficiency after 2000 h of storage under ambient conditions and exhibit substantially enhanced thermal stability. This work establishes a molecular-level design principle that couples defect passivation, strain management, and carrier-dynamics engineering, providing a versatile route toward highly efficient and durable perovskite photovoltaics.