Hydrazine Hydrochloride Derivatives Balance Precursor Coordination in Tin‐Based Perovskite Solutions

Abstract Tin halide perovskites are promising alternatives to lead‐based counterparts for photovoltaics, owing to their analogous electronic configurations, eco‐friendliness, and high charge carrier mobilities. However, their performance and reproducibility are limited by degradations in precursor solutions, solids, and devices, as well as defects arising from rapid and uncontrolled crystallization. While extensive research into solvent and additive engineering of precursor solutions has significantly enhanced the performance of Sn and Sn─Pb perovskite solar cells, the precise working mechanisms at the molecular level remain ambiguous. This study combines computational and experimental methods to elucidate the role of hydrazine‐hydrochloride‐based additives, specifically benzylhydrazine hydrochloride (BHC), in Sn‐containing perovskite precursor solutions. BHC enhances the coordinative interactions among dimethyl sulfoxide, tin‐diiodide, and formamidinium iodide, effectively mitigating the oxidation susceptibility of Sn(II) and stabilizing the precursor solution. Additionally, BHC facilitates halide exchange between I − and Cl − , thus reducing the SnI 4 content and improving crystallization dynamics. Experimental results reveal that BHC incorporation enhances both stability and power conversion efficiency of the Sn─Pb‐perovskite solar cells. This study provides critical insights into the design of advanced perovskite additives for high‐performance photovoltaic applications.