PDI derivatives with functional active position as non-fullerene small molecule acceptors in organic solar cells: From different core linker to various conformation

Abstract BHJ OPVs have made significant progress due to the development of active layer materials and the improvements in device technology. PDIs as star acceptors in BHJ OPVs have been attracting much attention owing to strong absorption in the visible region, tunable energy level, high electron mobility and excellent stability. However, several shortcomings such as unsatisfactory solubility, large π-conjugated system and excessive self-aggregation hinder the developments of PDI monomer. In order to overcome the above disadvantages while maintaining the inherent advantages, an effective method is to construct twisted PDI structures by constraining two or more PDI units with a linker or core. To quantify the effects of twisted PDI structures at the microscopic level, it is of great significance to characterize macroscopic factors associated with PCEs. Moreover, some key guidelines for engineering and modifying PDI derivatives are listed, including tuning ΔLUMO and ΔHOMO within limits, keeping rigid or ring-fused PDI derivatives and twisting dihedral angle between PDI units reasonably. This review aims to briefly outline a conformational branch of twisted PDI structures as NF-SMAs, based on the different active positions of PDI unit. Furthermore, it also establishes the relationship of “active position → structure → property → device performance” in order to provide a well-designed strategy of NF-SMAs and further a D/A matching standard.