Synchronous Doping Effects of Cathode Interlayers on Efficient Organic Solar Cells

An in-depth understanding of the role of cathode interlayers in nonfullerene organic solar cells (OSCs) is challenging due to ambiguous and complicated interfacial doping, which complicates molecular designs and hinders progress in optoelectronic performance. Herein, we describe synchronous doping effects (a combination of the cathode interlayer's self-doping and its doping on acceptors in the active layer) of cathode interlayers. The electronic nature of pi-conjugated cores in cathode interlayer materials has a negligible influence on nonfullerene acceptor doping but an obvious influence on their self-doping. A synchronous doping effect generated by the amine-substituted fullerene (C-60-N), with its electron-withdrawing C-60 core, facilitates interfacial charge transport and collection, affording a remarkable power conversion efficiency > 18% for PM6:L8-BO based OSCs, which is among the highest reported values for binary OSCs. This discovery of synchronous doping on interfacial modification provides new and useful molecular design guidelines for high-performance cathode modifiers in organic electronics.