A strategy for enhancing phosphine oxide passivation capacity of perovskite solar cells by fluorination

Perovskite solar cells have experienced rapid development in the last few years due to their excellent photovoltaic properties, and their efficiency and stability have attracted widespread attention. Passivating interfacial defects has been universally recognized as an effective performance enhancement strategy for perovskite solar cells (PSCs), but most reported strategies often fail to simultaneously meet the requirements of efficiency and stability. This paper proposes to enhance the passivation function of phosphine oxide by fluorination. On the one hand, P=O is used to form coordination bonds with Pb2+ in perovskite. On the other hand, the strong hydrophobicity of F gives perovskite excellent moisture stability and can hydrogen bond to organic cations in the perovskite. Thanks to its strong chelation with the defect sites, it achieved optimized energy level arrangement, suppressed non-radiative recombination, and excellent operation stability. Consequently, the efficiency of the optimized device increased by 21.6% with a remarkable enhancement of 40 mV in VOC and remained more than 90% of its initial efficiency after aging in air environment for 1000 h, improving both efficiency and stability. This study demonstrates a promising functional modification strategy for constructing efficient, stable, and environmentally friendly PSCs.