Self-doped conjugated polymers with electron-deficient quinone units for enhanced electron transport in highly efficient organic solar cells

Organic solar cells (OSCs) have attracted significant attention as a burgeoning flexible technology, owing to their advanced power conversion efficiencies. Moreover, interface materials play a crucial role in optimizing energy level alignment between the active layer and electrodes, thereby enhancing carrier extraction within the device and improving efficiency. However, current methodologies for fabricating electron-transport materials with superior mobility are still limited compared with those for hole-transport materials. In this study, a benzodifurandione (BFDO)-derived building block with quinone resonance property and strong electron-withdrawing capability was synthesized. Two conjugated polymers, namely PBFDO-F6N and PBFDO-F6N-Br, were prepared, both of which exhibited good electron mobility and exceptional interface modification capabilities. A comprehensive investigation of the interaction between the interface layer and the active layer revealed that PBFDO-F6N induced doping at the acceptor interface. Additionally, the high mobility of PBFDO-F6N facilitated efficient carrier extraction at the interface. Consequently, the application of PBFDO-F6N as the cathode interface layer for PM6:BTP-eC9-based OSC devices resulted in a remarkable efficiency of 18.11%. Moreover, the device efficiency remained at ∼96% even at a PBFDO-F6N interface thickness of 50 nm, demonstrating the great potential of this material for large-scale device preparation.