Melamine-Doped Cathode Interlayer Enables High-Efficiency Organic Solar Cells

Charge transport, extraction, and collection play important roles in the working process of organic solar cells (OSCs), and the interface engineering is one of the key factors to realize the high-throughput printing fabrication of OSCs. The structure design or doping of electrode interlayer materials can effectively suppress the recombination of carriers at the interface and improve the ohmic contact between the active layer and the electrodes, which is a useful method to achieve a high power conversion efficiency (PCE). Poly(9,9-bis(3′-(N,N-dimethyl)-N-ethylammoniumpropyl-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene))dibromide (PFN-Br) is a widely used alcohol-soluble cathode interlayer material. By doping PFN-Br with melamine (MA), the charge extraction efficiency and nongeminate recombination at the cathode interface are successfully optimized. Finally, the device efficiencies of PM6:Y6 and PM6:BTP-eC9 are increased to an amazing 17.44% and 18.58%, respectively. This work provides a new strategy for the fabrication of high-efficiency OSCs.