Doping and Thermoelectric Behaviors of Donor-Acceptor Polymers with Extended Planar Backbone

The design of a conjugated polymer backbone influences the charge transport and doping efficiency; however, the construction of the polymer backbone for maximized thermoelectric performance is still unclear. Herein, a novel synthesis of a donor-acceptor (D-A) conjugated polymer with an extended planar backbone, C6-ICPDPP, is reported for the investigation of the thermoelectric behavior. The C6-ICPDPP comprises a combination of fused heterocyclic compounds, both electron donor and acceptor groups, which show p-doping characteristics with FeCl 3 owing to the excellent planarization. The C6-ICPDPP films are formed from two types of solvents with different boiling points, both of which are doped with FeCl 3 , showing good thermoelectric properties; however, the thin-film structure, dopant diffusion, and thickness of the C6-ICPDPP films were different between the two solvents. With an increase in the doping concentration of FeCl 3 , the polarity of the majority charge carriers changes from positive to negative, indicating that the C6-ICPDPP exhibits both p- and n-type electrical behaviors with FeCl 3 doping. The optimized power factors are 1.32 µW/mK 2 (p-type) and 0.410 µW/mK 2 (n-type), respectively, which are consistent with the change in the polaronic features at the given FeCl 3 doping concentration. This study provides a design strategy for D-A conjugated polymers with extended planarization and electrical behavior suitable for organic thermoelectrics.