Enhanced Thermoelectric Performance of Dithienopyrrole and Thienoisoindigo‐Based Conjugated Polymers by Introducing Thiophene Spacers

ABSTRACT Donor‐acceptor (D‐A) conjugated polymers hold significant potential as high‐potential thermoelectric (TE) materials due to their adjustable structures, efficient charge transport ability and tunable doping level. However, achieving a balance between the Seebeck coefficient ( S ) and electrical conductivity ( σ ) remains challenging. In this work, we employ thienoisoindigo (TIIG) as the acceptor and dithieno[3,2‐b:2',3'‐d]pyrrole (DTP) as the donor to construct two novel D‐A conjugated polymers for TE application. Through introducing thiophene (T) units as spacers between DTP and TIIG, PTIIG‐2T‐DTP enhances the planarity of conjugated backbones compared to PTIIG‐DTP. Moreover, PTIIG‐2T‐DTP film shows more compact packing between conjugated backbones, which improves the charge transport. Despite slightly lower doping efficiency, doped PTIIG‐2T‐DTP exhibits superior carrier mobility and conductivity to PTIIG‐DTP. Additionally, PTIIG‐2T‐DTP shows a higher Seebeck coefficient at same doping concentration. Ultimately, PTIIG‐2T‐DTP achieves a large power factor of 23.2 µWm −1 K −2 with σ of 120 S cm −1 which is much higher than that of PTIIG‐DTP. This work develops an effective polymer backbone engineering strategy for developing high‐performance D‐A conjugated TE polymers.