Ionic Liquid Engineering Induced Hydrogen‐Bond Networks for Efficient Wide‐Bandgap Perovskite Photovoltaics

Wide‐bandgap (WBG, ~1.67 eV) inverted perovskite solar cells (PSCs) are highly promising for tandem photovoltaics, yet their performance is still constrained by defect‐induced nonradiative recombination and uncontrolled crystallization kinetics. Herein, we introduce a multifunctional ionic liquid, N ‐butylsulfonate pyridinium hydrogensulfate (BSPH), to simultaneously regulate crystallization kinetics and defect chemistry in WBG perovskites. Owing to its amphiphilic molecular architecture containing sulfonate, hydrogen sulfate, and pyridinium moieties, BSPH establishes dynamic multisite interactions with perovskite precursors. BSPH not only coordinates strongly with undercoordinated Pb 2+ species, but also forms extensive electrostatic and hydrogen‐bonding interactions with FA + cations and halide ions, creating a stabilized intermediate‐state network during film formation. It effectively suppresses rapid crystallization and regulates crystallization kinetics. Furthermore, the coupled hydrogen‐bond networks and electrostatic interactions effectively suppress ion migration and defect formation, leading to reduced trap‐state density, suppressed nonradiative recombination, and prolonged carrier lifetime. As a result, the optimized PSC achieves a champion power conversion efficiency of 23.72% and retains over 84.5% of its initial efficiency after 600 h maximum power point tracking. This work highlights ionic‐liquid molecular engineering as an effective strategy for cooperative crystallization regulation and defect management in high‐performance WBG PSCs.