Chelating Coordination Regulates Perovskite Crystallization and Defect Passivation in Sn–Pb Perovskite Solar Cells

ABSTRACT Tin‐lead (Sn‐Pb) perovskite (TLP) serve as potential narrow‐bandgap absorbers for photovoltaics; unfortunately, issues such as uncontrolled crystallization, Sn 2+ oxidation, and interfacial defects continue to limit device efficiency and stability. In this study, we present a chelating coordination strategy at buried and top perovskite interface utilizing ethylenediamine diacetate (EDDA) to synergistically regulate perovskite crystallization and defect passivation in TLP. Post‐treatment of PEDOT:PSS using EDDA mitigates surface acidity and reduces insulating PSS‐rich domains through ionic exchange, thereby shifting the buried interface potential. The carboxylate (─COO − ) groups of EDDA coordinate with undercoordinated Pb 2+ /Sn 2+ cations, while the ─NH 3 + groups form hydrogen bonds in TLP. These interactions at buried interface reduce nucleation concentration and promote homogeneous and orderly (100)‐facet crystal growth across TLP films. The chemical polishing of the TLP top surface inhibits the Sn 2+ oxidation, reduces defects and facilitates more efficient charge extraction. As a result, the Target devices demonstrate a power conversion efficiency (PCE) of 23.30% (0.09 cm 2 ), with an enhanced open‐circuit voltage of 0.877 V and a fill factor of 81.81%. Importantly, the Target device shows high stability for 300 s under continuous sunlight at maximum power point tracking and maintains 90% efficiency after 1800 h of storage in N 2 .