Hydrazinylbenzoic Acid Bifunctional Groups Synergistically Regulate the Crystallization of Wide‐Bandgap Perovskites for Efficient and Stable Solar Cells

Fabricating high‐quality wide‐bandgap (WBG) perovskite solar cells (PSCs) with a bandgap of approximately 1.68 eV is critical for realizing efficient tandem photovoltaics. However, these WBG PSCs frequently suffer from substantial open‐circuit voltage ( V OC ) losses and poor operational stability, primarily owing to uncontrolled perovskite crystallization and abundant defects in films. In this study, hydrazinylbenzoic acid (HBA), containing hydrazinyl and carboxyl groups, is employed as an additive to perovskite precursors. Through synergistic effects featuring strong coordination of both functional groups with Pb 2+ , HBA effectively regulates perovskite crystallization by accelerating nucleation and retarding crystal growth, yielding films with substantially enlarged grain size, reduced defect densities, and increased defect formation energy, thus suppressing non‐radiative recombination. Moreover, the hydrazinyl group can reduce photogenerated I 2 back to I − , effectively mitigating detrimental light‐induced halide segregation in the film. Consequently, the optimized HBA‐incorporated WBG PSCs achieve a remarkable power conversion efficiency (PCE) of 23.6% with an impressive V OC of 1.272 V, corresponding to considerably reduced V OC losses of 0.408 V. Under continuous maximum‐power‐point tracking for 797 h, the HBA device retains 90.9% of its initial PCE, vastly outperforming the reference device, which retains only 55.9%, and highlighting its superior operational stability.