Functionalizing triptycene to create 3D high-performance non-fullerene acceptors.

ABSTRACT

Non-fullerene acceptors have been widely investigated for organic solar cells (OSCs). In particular, fused-ring electron acceptors (FREAs), composed of two strongly electron-withdrawing end groups connected by a planar fused-ring core, have been successfully applied to develop high-performance OSCs (>16%). In this work, we proposed two novel 3D FREAs named BFT-3D and BFTT-3D, which can reduce the formation of crystalline domains and increase the interface with donors to promote exciton separation. These 3D FREAs consist of three strongly electron-withdrawing end groups linked by a central triptycene hub to form a three-bladed propeller nanostructure. In comparison with high-performance FREA (ITOIC-2F), these FREAs have stronger absorption intensity and smaller exciton binding energy. These findings demonstrated that these three-bladed propeller-shaped FREAs can absorb abundant energy from sunlight to generate excitons, easily separate excitons to free electrons and holes, and reduce the recombination of excitons. In addition, the electron mobility of BFT-3D (8.4 × 10-4 cm2 V-1 s-1) is higher than that of BFTT-3D (1.0 × 10-4 cm2 V-1 s-1), which indicated that the appropriate 3D core structure was conducive to the electron mobility of the three-bladed propeller-shaped FREAs. It can effectively improve the current density to enhance the performance of OSCs. These findings will provide new perspectives for experimental scientists to synthesize high-performance FREAs.