Fluorine-Rich Pentafluorophenyl-Substituted Electron-Transport Interfacial Materials for Efficient Perovskite Solar Cells.

The strategic design of electron-transporting materials is crucial for improving charge extraction and stability in perovskite solar cells (PSCs); however, device performance is often limited by poor interfacial compatibility, which leads to inefficient charge transfer and reduced stability. To address these challenges, two new fluorinated electron-transport interfacial materials (ETIMs), namely TFP-Bp (1) and TFP-Pyr (2), were developed by incorporating hydrophobic fluorinated phenyl (FP) substituents onto biphenyl (Bp) and pyrene (Pyr) cores. Additionally, a non-fluorinated pyrene derivative, TP-Pyr (3), was synthesized as a structural analogue of TFP-Pyr (2) to elucidate the influence of fluorine substitution on interfacial properties and device performance. Single-crystal X-ray analysis of compounds 1 and 2 reveals that both molecules adopt markedly twisted conformations, which effectively suppress excessive aggregation. In addition, the fluorinated substituents enhance surface hydrophobicity and strengthen interfacial interactions with the perovskite layer, leading to improved film formation. The optimized devices based on TFP-Bp (1) and TFP-Pyr (2) deliver power conversion efficiencies (PCEs) of 21.07% and 21.50% for wide-bandgap PSCs, respectively, under one-sun illumination. Notably, excellent indoor performance is also achieved, with PCEs of 41.12% for TFP-Bp (1) and 43.34% for TFP-Pyr (2), demonstrating their strong potential as ETIM for indoor light applications.