Enhanced Thermoelectric Performance of a Donor–Acceptor-Based Two-Dimensional Conjugated Polymer with High Crystallinity

Introducing two-dimensional (2D) conjugated structures to polymers is a feasible way for the design of functionalized polymers due to their good planarity, high electron/hole mobility, thermal stabilities, and so forth. However, the current development of thermoelectric polymers is mainly restricted to the limited modification of the one-dimensional conjugated polymers. Herein, a novel donor–acceptor based 2D conjugated polymer, P(BDTTT-DPP), was designed and synthesized for the enhancement of thermoelectric properties. Compared to the one-dimensional conjugated polymer P(BDT-DPP), P(BDTTT-DPP) showed a higher doping level when doped with the p-type FeCl3 dopant. After doping with 20 mg/mL FeCl3 for 15 min, the optimal power factor of P(BDTTT-DPP) was obtained to be 6.50 μW m–1 K–2 at room temperature, which is 26 times higher than that of P(BDT-DPP). The studies of film morphology and packing structure analysis further indicated that the π–π stacking (010) distance of P(BDTTT-DPP) was maintained after the doping process, and the longer lamellar stacking distance allowed the FeCl3 dopants to efficiently incorporate between the lamellar domains compared to that of P(BDT-DPP), which is favorable to the crystallinity and electron transferability. The results of our work provide valuable insights into the development of donor–acceptor based 2D conjugated polymer for high-performance organic thermoelectric materials.