Modulating Perovskite Crystallization via Multisite Bonding for Enhanced Solar Cell Performance

Uncontrolled crystallization kinetics and intrinsic defects in perovskite films critically limit photovoltaic performance. Herein, we introduce a multisite bonding strategy using bidentate ligand N,N ‐Diethyl‐1,2‐ethanediamine dihydrochloride (DED) to simultaneously modulate crystallization dynamics and suppress defects. The dual amine groups of DED establish a bidentate configuration that coordinates undercoordinated Pb 2+ ions and I − vacancies and forms hydrogen bonds with FA + cations. In situ characterization reveals this synergistic interplay suppresses the nucleation kinetics and retards the rapid FAI–PbI 2 reaction, thereby extending the crystallization window to facilitate lattice strain release and enhance crystalline quality. Consequently, this multisite bonding function improves the lattice stress, decreases the density of defect states, extends carrier lifetime, and mitigates nonradiative recombination. Optimized devices achieve a champion PCE of 25.19% with minimal hysteresis while exhibiting exceptional stability, retaining 90.3% initial efficiency after 2000 h ambient aging and 92.1% after 600 h under maximum power point tracking. This work demonstrates the potential of bidentate ligand‐mediated multisite bonding for developing efficient and operationally stable perovskite photovoltaics.