Multifunctional Molecular Bridge Strategy for Efficient and UV-Resilient Perovskite Solar Cells

Nonradiative recombination originating from the defect-rich SnO2/perovskite buried contact and the absorber interior imposes a major constraint on photovoltaic output and device durability. Here, ethylenediaminetetraacetic acid dipotassium salt (EDTA-2K) is inserted as a molecular bridge that modifies the chemical environment and electronic structure on both sides of this buried junction. Its multiple binding sites coordinate with undercoordinated Sn4+ on SnO2 and Pb2+ in the perovskite. In parallel, K+ supplied by EDTA-2K combines with iodide to form KI, while the remaining functional groups interact with halides through hydrogen bonding; together, these effects impede halide migration. This concerted regulation lowers the defect density, relaxes interfacial strain, guides perovskite growth, and produces a more favorable depth distribution of residual PbI2. It also improves interfacial energy alignment and electron extraction. Employing poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) for hole transport enabled the best-performing cell to achieve a power conversion efficiency (PCE) of 24.32%. Following 3000 h of storage, the remaining efficiency exceeds 95% of the starting value; a separate 500 h test under intense ultraviolet (UV) light in ambient air leaves 94.77% of the original PCE. The proposed interfacial architecture thus combines high photovoltaic performance with pronounced resistance to UV-induced aging.