Chlorinated Carbon-Bridged and Silicon-Bridged Carbazole-Based Nonfullerene Acceptors Manifest Synergistic Enhancement in Ternary Organic Solar Cell with Efficiency over 15%

Herein, two novel nonfullerene acceptors (NFAs), DTCC-4Cl and DTSiC-4Cl, are synthesized by end-capping dithienocyclopentacarbazole (DTCC) and dithieno-silolocarbazole (DTSiC) cores with chlorinated IC (2Cl-IC) units, respectively. With the better-known advantage of having the extraordinary sigma*-pi* conjugation of silole unit embedded in the DTSiC core, DTSiC-4Cl manifests upshifted lowest unoccupied molecular orbital (LUMO), blue-shifted absorption, and increased pi-pi interaction in comparison with DTCC-4Cl. Furthermore, to elucidate the effect of bridging atoms on the photovoltaic performance, T1 is selected as the polymer donor to be blended with DTCC-4Cl and DTSiC-4Cl. T1:DTCC-4Cl-based devices exhibit a fine power conversion efficiency (PCE) of 14.43% and T1:DTSiC-4Cl-based devices exhibit a comparable PCE of 14.46%. Interestingly, the T1:DTSiC-4Cl-based devices demonstrate an additive-free feature, which is worthy of further applications. From the perspective of constructing high-performance ternary devices, DTCC-4Cl is expected to possess excellent compatibility with DTSiC-4Cl owing to its structural similarity. As anticipated, the ternary T1:DTSiC-4Cl:DTCC-4Cl-based device outperforms the binary T1:DTCC-4Cl and T1:DTSiC-4Cl-based devices, affording a decent PCE of 15.04% with aV(OC)of 0.97 V, aJ(SC) of 20.80 mA cm(-2), and an FF of 74.55% without any additive.