Fluoro- and Amino-Functionalized Conjugated Polymers as Electron Transport Materials for Perovskite Solar Cells with Improved Efficiency and Stability.

We report here novel bifunctionalized electron transport materials (ETMs) that can improve the efficiency and stability of perovskite solar cells (PVSCs) simultaneously. By functionalizing n-type conjugated polymers with fluoro and amino side chains, PN, PN-F25%, and PN-F50% with varied contents of fluoro and amino side chains are prepared. It is found that the amino side chains in ETMs efficiently improve the interface contact and electron collection of PVSCs, with improved power conversion efficiency from 14.0% for PC61BM-based devices to more than 17% for PN- and PN-F25%-based devices. Moreover, the fluoro side chains endow these polymers with excellent hydrophobic properties, which largely enhance their water-resistance capabilities. ETMs with the increased content of fluoro side chains can substantially improve the water resistance of perovskite layers, with a significant improvement in the stability of PVSCs. Our results indicate that the fluoro- and amino-bifunctionalized strategy is a promising method to design ETMs for high-performance and stable PVSCs.