Self-Segregated Buried-Interface Regulation Resolves Kinetic-Environmental Coupling for Ambient Flexible Perovskite Solar Cells.

Ambient fabrication of flexible perovskite solar cells is fundamentally limited by a detrimental kinetic-environmental coupling at the buried interface, where moisture ingress and nonoptimal crystallization mutually compromise film quality-yet the underlying mechanism remains elusive. Using dual-side in situ photoluminescence, we overturn the conventional top-down model by revealing simultaneous nucleation at both gas-liquid and liquid-solid interfaces during antisolvent-assisted solution processing, but find that outward solvent evaporation delays α-phase conversion at the buried interface relative to the surface, creating kinetic mismatch that exacerbates moisture attack and defect accumulation. To address these kinetic and environmental constraints, we design a self-segregating multifunctional molecule, 2-[(3-trifluoromethyl)phenyl]amino-3-pyridinecarboxylic acid (NFA), which spontaneously enriches at the buried interface to synchronize dual-interface crystallization while simultaneously passivating defects, optimizing energy-level alignment, and constructing a hydrophobic barrier against moisture ingress. Consequently, this self-segregated kinetic-environmental regulation yields record ambient flexible photovoltaic performance with power-conversion efficiencies of 24.84% (0.09 cm2, certified at 23.75%) and 21.46% on mini-modules (13.8 cm2). The optimized devices maintain 96.26% of their starting efficiency following 1000 h damp aging at 85 ± 5% RH. Our work establishes self-segregated interfacial regulation as a rational route to address kinetic and environmental constraints in scalable flexible photovoltaics.