Two nonlinear ?-conjugated polymerized small molecular acceptors containing thiophene or 3,4-Difluorothiophene linkage unit for all-polymer solar cells

Recently, lots of high-performance linear pi-conjugated polymer acceptors based on the strategy of polymerizing small-molecule acceptors have been developed. However, there very few reports on nonlinear pi-conjugated polymer acceptors for all-polymer solar cells. Here, we explored and synthesized two nonlinear pi-conjugated polymer acceptors, named TZ1 or TZ2, respectively. Compared with the nonfluorinated polymer acceptor TZ1, the fluorinated polymer acceptor TZ2 presents lower energy level and better molecular aggregation. After blending with PM6, the TZ2-based device displayed more efficient exciton dissociation, higher charge carries mobilities and less charge recombination, leading to its higher Jsc of 14.94 mA cm-2. As a result, the TZ2-based device achieved a PCE of 7.41%, higher than the TZ1-based device (4.06%). Our results provide a new strategy to develop nonlinear pi-conjugated polymer acceptors and demonstrate the selection of suitable bridges is of importance for the construction of nonlinear pi-conjugated polymer acceptors.

Automated summary

Recently, high-performance linear pi-conjugated polymer acceptors have been developed by polymerizing small-molecule acceptors. However, there is a lack of reports on nonlinear pi-conjugated polymer acceptors for all-polymer solar cells. In this study, we synthesized two nonlinear pi-conjugated polymer acceptors, TZ1 and TZ2, and found that the fluorinated polymer acceptor TZ2 exhibited better performance than the nonfluorinated polymer acceptor TZ1. The TZ2-based device achieved a higher power conversion efficiency (PCE) of 7.41% compared to the TZ1-based device (4.06%), demonstrating the importance of suitable bridge selection in the construction of nonlinear pi-conjugated polymer acceptors.