Simultaneous Ultraviolet Conversion and Defect Passivation Stabilize Efficient and Operational Durable Perovskite Solar Cells

Abstract Despite the swift development in perovskite solar cells (PSCs), great concerns regarding environmental vulnerability propose a big challenge for their long‐term operational stability. Herein, a novel functionalized ultraviolet (UV) conversion small molecule, Coumarin 153 (C153), is judiciously introduced into perovskite precursor to effectively enhance device efficiency and operational stability against UV radiation. It is found that the uncoordinated Pb 2+ and A‐site vacancies of perovskite can be successfully fixed through Lewis acid–base coordination and hydrogen bonding upon C153 treatment, resulting in a stabilized structure with remarkably reduced intrinsic defects. Concurrently, the incremental visible light absorption derived from the down‐conversion effect of C153 molecules together with the optimized energy level arrangement contribute to the substantially enhanced photocurrent of the device. As a result, the resultant device delivers a champion efficiency of 24.73%, accompanied by greatly improved operational stability against environments, with retaining over 90% of initial PCE for ≈380, ≈1400, and 1710 h aging under continuous UV radiation, heating stress, and illumination, respectively. This work provides an effective and feasible strategy toward high‐efficiency and environment‐stable PSCs.