Impact of chlorination on the properties of small-molecule donor for all-small-molecule organic solar cells

Abstract Chlorinated small-molecule DRTB-Cl was designed and synthesized for all-small-molecule organic solar cells (ASM-OSCs). DRTB-Cl and non-chlorinated DRTB were selected as the electron donors to construct ASM-OSCs with nonfullerene acceptor Y6. High efficiencies of 11.92% and 10.09% were achieved for DRTB-Cl:Y6- and DRTB:Y6-based devices after optimization, respectively. DRTB-Cl:Y6-based device showed higher open-circuit voltage (Voc), which was ascribed to the lower-lying highest occupied molecular orbital (HOMO) energy level of DRTB-Cl. Meanwhile, the better phase separation and more balanced charge mobility contributed to the higher fill factor (FF) for DRTB-Cl:Y6-based device.