Compact Multifunctional Cation Regulating 1D/3D Heterointerface for High‐Performance Inverted Perovskite Solar Cells

Compositional disorder and insufficient passivation of defects remain major obstacles to simultaneously achieving high‐efficiency and long‐term stability in low‐dimensional perovskite‐containing inverted perovskite solar cells (PSCs). Here, we report a multifunctional short‐chain organic salt, 2‐hydrazino‐2‐imidazoline hydrobromide (HyImBr), for reconstructing a well‐defined one/three dimensional (1D/3D) heterostructure at the top interface. Owing to its compact molecular structure and abundant nitrogen‐containing functional groups, HyImBr simultaneously enables hydrogen bonding with A‐site cations/halides, coordination with undercoordinated Pb 2 + , and effective passivation of multiple types of defects, thereby reducing the overall defect‐state density. The reconstructed surface also releases local tensile strain and optimizes energy‐level alignment for efficient electron extraction. As a result, the HyImBr‐treated inverted PSC device delivers a champion power conversion efficiency of 26.11%, significantly outperforming the control device (23.51%) through simultaneous improvements in open‐circuit voltage and fill factor. The unencapsulated device retains 92.16% of its initial efficiency after 1100 h of storage in air. This work presents a molecular design strategy for constructing uniform, defect‐passivated, and oxidation‐resistant 1D/3D heterostructures, enabling efficient and stable photovoltaic devices.