Modification of the Electron-Deficient Core on Unfused-Ring Acceptors Enabling High Open-Circuit Voltage of Organic Solar Cells

Unfused-ring acceptors with different electron-deficient central units, dithieno[3,2-f:2 ',3 '-h]quinoxaline (KS40) and dithieno[3,2-e:2 ',3 '-g]-2,1,3-benzoxadiazole (KS41) are synthesized and characterized. When blended with PM6, KS40 with a weaker electron-accepting quinoxaline exhibits a much higher open-circuit voltage (VOC) of 0.945 V. As a result, the KS40-based device achieves a power conversion efficiency (PCE) of 12.2%. PM6:KS41-based devices, in contrast, afford improved charge mobilities as well as suppressed recombination behavior, which eventually leads to an improvement in the fill factor (72.4%). Consequently, the device is able to achieve a PCE of 11.6%. Unfused-ring acceptors with different electron-deficient central cores (quinoxaline (KS40) and benzoxadiazole (KS41) units) lead to higher open-circuit voltages (VOCs) for organic solar cells, and the KS40-based device achieves a champion power conversion efficiency of 12%.image (c) 2024 WILEY-VCH GmbH