Plant‐Derived Multifunctional Molecular Bridges Enable High‐Efficiency Air‐Processed Flexible Perovskite Solar Cells via Nanoscale Dual Modulation

Flexible perovskite solar cells (f‐PSCs) hold immense promise for next‐generation wearable and portable photovoltaic applications, yet their commercialization is severely impeded by interfacial non‐radiative recombination and insufficient mechanical durability at the SnO 2 /perovskite interface. Here, we demonstrate a dual‐modulation molecular bridge strategy using the plant‐derived amino acid derivative potassium acetyl‐L‐lysinate (P‐AcL), deposited as an ultrathin interlayer on pre‐annealed SnO 2 films, to simultaneously address both challenges. P‐AcL forms robust bidentate carboxyl coordination and amino hydrogen‐bonding with SnO 2 films, passivating surface oxygen vacancies, optimizing interfacial energy alignment, and inhibiting buried‐interface thermal decomposition. Its long alkyl chain and amide groups extend toward the perovskite layer, dual‐anchoring undercoordinated Pb 2+ and iodide vacancy defects, releasing residual thermal stress, guiding high‐quality perovskite crystallization, and mitigating bending‐induced interfacial delamination. Benefiting from this synergy, air‐processed f‐PSCs (20% RH) achieve a champion power conversion efficiency of 25.21%, and retain >24% PCE even under 40% RH. The modified devices retain 85.6% and 90.2% of their initial PCE after 10 000 convex and concave bending cycles at a 5 mm radius, respectively, alongside improved light and thermal stability. This work provides a simple, green, scalable route toward high‐efficiency, stable flexible perovskite photovoltaics.