Synergistic halogenation of backbone and end group for high-performance non-fused acceptors based organic solar cells

Non-fused small molecule acceptors based on organic solar cells have the potential to realize low-cost and large-scale industrialized production, benefited by their intrinsic simple synthesized procedures and high yield. However, it is still a challenge to acquire high-performance organic solar cells through the structural adjustment of the non-fused small molecule acceptors. In this work, a synergistic halogenation strategy both in the backbone and in the end group was used to address this issue. Four novel non-fused acceptors, namely BDTC-4F, F-BDTC-4F, and F-BDTC-4Cl were designed and synthesized with much simpler procedures with similar backbone structures but different halogen atoms modification both in the side chains of the backbones and end groups. After device optimization, the resulting OSCs based on F-BDTC-4Cl yield a good efficiency of 10.28%, with an enhanced fill factor (FF) of 63.8%, short-circuit current density (JSC) of 19.28 mA cm−2 and open-circuit voltage (VOC) of 0.836 V, which is higher than that of the BDTC-4F- (9.70%), BDTC-4Cl- (9.42%), and F-BDTC-4F- (8.84%) based devices. The results demonstrate an improved photovoltaic performance from simple structure modification and synthetically inexpensive could be achieved by rational halogenation of non-fused acceptors.