In situ Polymerization‐Driven Dynamic Intermediate‐Phase Transition for Active Crystallization Modulation in Air‐Processed Flexible Perovskite Solar Cells

Abstract The commercialization of flexible perovskite solar cells (f‐PSCs) requires cost‐effective fabrication under ambient air, yet the moisture sensitivity of hygroscopic perovskites disrupts their crystalline phase and hampers photovoltaic performance. Here, an in situ polymerization‐driven dynamic intermediate‐phase transition ( is ‐DIPT) strategy is reported that stabilizes lead iodide (PbI 2 ) colloids and directs perovskite crystallization kinetics to mitigate moisture interference. Specifically, a polymerizable small‐molecule ligand, acryloyloxyethyltrimethyl ammonium chloride‐acrylamine (DAC‐AA), coordinates with PbI 2 to form a metastable PbI 2 ‐DAC‐DMF ( N , N ‐dimethylformamide) phase, which dynamically evolves into PbI 2 ‐DAC and PbI 2 ‐ is (DAC) adducts during the in situ polymerization. Such intermediate‐phase pre‐growth engineering minimizes the unfavorable PbI 2 ‐DMF complex and exerts thermodynamic and kinetic modulation over nucleation and crystal growth, favoring the growth of α‐phase perovskites. Accordingly, the champion f‐PSCs upon is ‐DIPT modification fabricated under ambient air conditions deliver efficiencies of 24.17% (0.092 cm 2 ) and 23.26% (1 cm 2 ). Moreover, the polymerized perovskites benefiting from a flexible polymer network decrease Young′s modulus and enhance mechanical robustness, maintaining 86.7% of their efficiency after experiencing 20 000 cycles with a 6 mm curvature radius.