Revealing Bifunctional Molecules Induced Adequate DMSO Extraction in Sequential Crystallization toward Efficient and Robust Flexible Perovskite Solar Cells

Abstract Flexible perovskite solar cells possess great application potential in both stationary and mobile photovoltaics because of their lightweight and bendable features. However, the poor crystallinity of perovskite and the fragility of the buried interface on flexible substrates with a rough surface and poor wettability result in efficiency and durability losses. Herein, the critical role of buried interface quality in governing dimethyl sulfoxide (DMSO) evaporation and the sequential crystallization kinetics is uncovered. A facile and effective strategy is implemented by adopting several bifunctional polar molecules with different groups, including 3‐aminopropanoic acid (APAC), 3‐iodo‐1‐propanol (IDPA), and 3‐iodopropionic acid (IDPAC), to modify the SnO 2 /perovskite interface. Multifunctional molecules bearing appropriate functional groups can concurrently passivate interfacial defects on both sides, which strongly adsorb DMSO molecules, enabling adequate solvent removal during crystallization and minimizing buried interfacial voids. This dual‐passivation strategy simultaneously yields stress‐relaxed flexible perovskite films while strengthening interfacial adhesion and charge transport properties. Consequently, IDPAC‐modified rigid cells achieve a champion efficiency up to 25.59% (certified 24.92%), while flexible devices exhibit a seductive efficiency of 24.90% (certified 24.39%) and retain 92% of the initial efficiency after bending 10 000 cycles with a radius of 5 mm.