Multifunctional Pentafluorobenzoic Acid Boosts the Efficiency and Stability for Tin Halide Perovskite Solar Cells

Tin halide perovskite solar cells (TPSCs) have made remarkable breakthroughs in photovoltaic performance recently. However, the Sn²⁺/Sn⁴⁺ oxidation has limited the stability of TPSCs, which is related to many factors, including film crystallinity, hydrophobicity, etc. In this work, we report a multifunctional molecule of pentafluorobenzoic acid (PFBA) as an additive into tin halide perovskite to enhance the stability. The carboxyl and hydroxyl groups in PFBA effectively acted with SnI₂ through Lewis acid-base addition and hydrogen bonding, respectively, which effectively regulated the crystallization process of tin halide perovskite and reduced the lattice stress, thus avoiding defect-induced recombination centers in TPSCs. In addition, the hydrophobicity of the -F functional group in PFBA was conducive to improving the hydrophobicity of the tin halide perovskite film, thus alleviating the invasion of water and oxygen. Finally, the target device with PFBA obtained a power conversion efficiency (PCE) of 11.59% and maintained 88.00% of the initial PCE after aging 1500 h in a N₂ glovebox.