Selective Bidentate Coordination Reconstructs Residual PbI₂ to Homogenize Interfacial Energetics in Perovskite Solar...

Spatially heterogeneous interfacial energetics, often originating from residual lead iodide (PbI₂), represent a fundamental bottleneck to both the efficiency and operational stability of perovskite photovoltaics. Conventional PbI₂ passivation strategies based on monodentate ligands or highly polar solvents either interact weakly with PbI₂ or undesirably perturb the underlying three-dimensional perovskite lattice. Here, we report a diammonium bidentate strategy that selectively reconstructs residual PbI₂ into corner-sharing PbI₆ octahedra while preserving the bulk perovskite. Enabled by dual-site coordination, a newly designed thiophene-based bidentate ligand (MeXT) stabilizes PbI₆ units during passivation and establishes spatially homogeneous interfacial energetics. Perovskite solar cells incorporating MeXT achieve 26.19% power conversion efficiency and retain over 80% of their initial efficiency after 1000 h of continuous 1-sun illumination at 75 °C. This dual-anchor coordination passivation strategy establishes a general design principle for selectively treating residual PbI₂ and creating electronically coherent and operationally stable interfaces in perovskite photovoltaics.