An efficient star-shaped fused-ring electron acceptor with C3h-symmetric core via thieno 3,2-bthiophene extending conjugation strategy

摘要

The thieno[3,2-b]thiophene (TT) unit is a classic building block to construct high-performance fused-ring electron acceptors (FREAs) for organic solar cells (OSCs). In this work, a star-shaped FREA BTTCTT-ICF basedonanew C3h-symmetric fused-ring core BTTCTT was designed and synthesized by introducing the TT unit to extend the p-conjugation. Due to its strong electron-donating ability and efficient p-electron delocalization, BTTCTT-ICF exhibited a narrow optical bandgap of 1.54 eV and a high absorption extinction coefficient of 3.6 105 M1 cm1 . The blend film of BTTCTT-ICF and the wide bandgap polymer PM6 produced a complementary absorption and a broad EQE spectral range covering 300 to 850 nm. When treated via thermal annealing, the PM6:BTTCTT-ICF blend film exhibited more ordered molecular packing and a suitable phase morphology, which improved its charge mobility and device efficiency. Consequently, the PM6:BTTCTT-ICF-based inverted device achieved the best power conversion efficiency (PCE) of 10.39% with a high short-circuit current density (Jsc)of16.77mAcm2 , open-circuit voltage (Voc)of0.91Vandfill factor (FF) of 68.08%. Our results demonstrate that the extension of the star-shaped fused-ring core by TT units is a rational and effective strategy for achieving highly efficient star-shaped FREAs.