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

ABSTRACT 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 SnO 2 /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.