Enhancing the Performance of Perovskite Solar Cells through Interfacial Modification by Fluorinated 2D Perovskite

Despite achieving high power conversion efficiency (PCE), the large-scale commercialization of perovskite solar cells (PSCs) remains limited by the poor stability of three-dimensional (3D) perovskites. Here, a two-dimensional (2D) perovskite-based interface engineering strategy is employed to improve device stability. A thin capping layer of 2D perovskite, 4-fluorobenzylammonium lead bromide ((4-FBA) 2 PbBr 4 ) is deposited on the 3D mixed-cation methylammonium–formamidinium lead iodide (MAFAPbI 3 ) perovskite layer. The incorporation of this 2D layer significantly improves the film morphology, suppresses trap-state density, and enhances environmental robustness. The optimized 3D/2D hybrid device achieves PCEs of 18.40% under 1 sun and 34.54% under indoor LED illumination (1000 lux). Notably, the device exhibits enhanced stability, retaining 77.82% of its initial efficiency after thermal heating at 80 °C for 10 h and 55.32% after 30 days of storage under ambient air. These results highlight the efficacy of interfacial passivation engineering in developing high-performance and stable PSCs for both outdoor and indoor applications.