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

Unfused‐ring acceptors (UFAs) 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) were synthesized and characterized. When blended with PM6, KS40 with a weaker electron accepting Quinoxaline exhibited a much higher open‐circuit voltage ( V OC ) of 0.945 V. As a result, the KS40‐based device achieved a power conversion efficiency (PCE) of 12.2%. PM6:KS41 based devices, on the other hand, afforded improved charge mobilities as well as suppressed recombination behavior, which eventually led to an improvement in the fill factor (FF, 72.4%). Consequently, the device was able to achieve a PCE of 11.6%. This article is protected by copyright. All rights reserved.