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 SnO2, was developed to passivate charged defects and regulate the electronic properties at the KF-SnO2/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 SnO2 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-SnO2-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-SnO2 in the scalable fabrication process, demonstrating that 8 × 4 cm2 flexible perovskite solar modules (active area of 26.0 cm2) achieved an efficiency of 14.26%. This highlights the benefits of KF-based interface engineering for advancing the upscaling and high-performance PSCs.