Interfacial Distribution Effects of Potassium Fluoride on Enhancing Performance and UV Stability of Perovskite Solar Cells

Perovskite photovoltaics offer a promising solution for lightweight power generation for near-space applications. The key factors including device efficiency and long-term ultraviolet (UV) light stability are essential for ensuring the sustainability of energy harvesting devices, yet to be further improved for perovskite solar cells (PSCs). In this work, a synergetic interface modification strategy, utilizing potassium fluoride (KF) as the modifier in SnO 2, was developed to passivate charged defects and regulate the electronic properties at the KF-SnO 2 /perovskite interface. The optimization impacts of KF were systematically revealed by examining the spatial distribution of its binary ionic components and related coordination effects at the contact interface. The K + ions can migrate into the bulk perovskite serve to passivate the grain boundaries and stabilize the lattice structure, while F – ions prefer to retain within the SnO 2 layer to tailor the interfacial properties. The KF modification collectively contributes to significant improvements in defect passivation, energetic alignment, suppression of nonradiative recombination, and UV resistance of PSCs. As a result, the KF-SnO 2 -based PSCs achieved an efficiency of 23.17%, retaining more than 90% of the original efficiency after over 1000 h of continuous UV-light illumination or 350 h of operation under one sun illumination. Furthermore, we validated the compatibility of KF-SnO 2 in the scalable fabrication process, demonstrating that 8 × 4 cm 2 flexible perovskite solar modules (active area of 26.0 cm 2 ) achieved an efficiency of 14.26%. This highlights the benefits of KF-based interface engineering for advancing the upscaling and high-performance PSCs.