Strong Nonradiative Recombination Induced by Pronounced Lone‐Pair Electron Expression Following Deprotonation in Aziridinium Lead Iodide Perovskites

Deprotonation of organic cations in hybrid perovskites generates nitrogen‐site hydrogen vacancies that activate lone‐pair electrons and induce configuration‐dependent nonradiative losses. Here, we introduce a novel cyclic A‐site organic cation, aziridinium, into the APbI 3 perovskite lattice and establish a direct structure–function correlation between the molecular configuration of the organic cation and the lone‐pair electron activity associated with nitrogen‐site hydrogen vacancies defects. Compared with conventional formamidinium and methylammonium cations, the geometrically constrained, distorted coordination environment of aziridinium promotes facile deprotonation, resulting in a higher tendency for nitrogen‐site hydrogen vacancies formation. The deprotonated aziridinium species exhibit markedly enhanced lone‐pair electron activity, acting as strong Lewis bases that perturb the local PbI 6 octahedra by detaching Pb 2+ ions and forming stable Pb–AZ dimers. These defect complexes serve as highly efficient nonradiative recombination centers, yielding an ultrahigh carrier capture coefficient of 10 −5 cm 3 s −1 . This work reveals the decisive influence of A‐site cation chemistry on defect energetics and recombination kinetics, emphasizing the necessity of simultaneously optimizing iodide stoichiometry and aziridinium incorporation to suppress nonradiative losses in aziridinium‐based halide perovskites.