Conjugated Hydrazide-Mediated Precursor Coordination Regulation Enables Uniform Crystallization of Tin-Lead...

Narrow-bandgap tin-lead (Sn-Pb) mixed perovskites are important materials for advancing single-junction photovoltaics toward their theoretical efficiency limit. However, their inherent asynchronous crystallization triggers severe morphological inhomogeneity and generates a high defect density, which limits the performance and long-term stability of devices. Unlike conventional Lewis base strategies that predominantly focus on direct bonding effects for simple defect passivation, we propose a strategy for precursor colloidal regulation mediated by aromatic conjugated hydrazide derivatives. Extending the conjugation length of the hydrazide molecular framework established preferential coordination interactions between the additive and SnI₂ precursor. This preferential complexation alleviated the aggregation of perovskite clusters and inhibited the rapid precipitation of Sn species, while simultaneously suggesting a lowered apparent heterogeneous nucleation energy barrier on the substrate. This approach achieved uniform and balanced Sn/Pb crystallization kinetics, which enabled the formation of compact, pinhole-free perovskite films. The optimal device modified with 2-naphthoylhydrazine delivered a power conversion efficiency of 24.16%, along with significantly enhanced operational stability, which retained 88.2% of its initial efficiency after 1200 h of continuous illumination. This work offers novel insights into precisely regulating the crystallization of narrow-bandgap Sn-Pb perovskites to enable the development of efficient and stable perovskite photovoltaics.