Synergistic Molecular Modulation via Coordination and Hydrogen Bonding for Efficient Perovskite and Tandem Solar Cells

ABSTRACT Molecular additives offer a powerful route to control crystallization kinetics and homogenize component distribution in perovskite semiconductors. However, additives that integrate Pb‐related coordination and hydrogen‐bonding functionalities within a single molecular framework to jointly regulate crystallization evolution and defect chemistry remain largely underexplored. Herein, we introduce 4,4’‐(phenylphosphoryl)dibenzoic acid (PPDBA) as a multifunctional molecular modulator that combines P═O and ─COOH groups within a single framework. Compared with P═O‐only reference molecule triphenylphosphine oxide (TPPO), PPDBA expands the interaction scope by coupling Pb‐related coordination involving P═O/─COOH functionalities with additional ─COOH‐assisted hydrogen bonding toward organic cations. These cooperative interactions facilitate intermediate‐phase evolution modulation, crystallization retardation, and the formation of uniform perovskite films with reduced residual PbI 2 . In addition, PPDBA preferentially enriches near the perovskite surface, where it contributes to defect passivation and improved carrier extraction. Consequently, PPDBA‐treated 1.55 eV PSCs achieve a power conversion efficiency of 26.31% with exceptional stability. The universality of the strategy is further demonstrated by high efficiencies of 23.50% and 19.13% PCEs for 1.68 and 1.84 eV wide‐bandgap PSCs, respectively. Beyond single‐junctions, PPDBA enables high‐performance tandems, delivering 33.05% (certified 32.65%) in perovskite/silicon and 26.11% in perovskite/organic architectures. This work provides a molecular design blueprint for high‐performance, durable perovskite‐based photovoltaics.