Thermoelectric Performance in Triplet‐Ground‐State Polymer Intrinsically Boosted by Enhanced Proquinoidal Characteristic

Abstract

Polymer thermoelectric materials featuring flexibility, lightness, and bio−friendliness have been paid increasing attention for waste heat recovery and energy generation. The dominant approach to optimizing the thermoelectric performance of most organic materials is chemical doping, which, however, is not always ideal for practical applications due to its tendency to involve intricate processing procedure and trigger material and device instability. The pursuit of single−component neutral thermoelectric materials without exogenous doping presents a compelling alternative. In this work, we designed and synthesized a high−spin polymer material, PBBT−TT, by simultaneously employing thieno[3,4−b]thiophene (TbT) and benzo[1,2−c:4,5−c′]bis[1,2,5]thiadiazole (BBT) units with pronounced proquinoidal characteristics, and its analogue, PBBT−T. Because of the enhanced quinoidal resonance, increased spin density, and strong intermolecular antiferromagnetic coupling, PBBT−TT exhibits high intrinsic electrical conductivity and Seebeck coefficient, which showcases an outstanding power factor of 26.1 μW m−1 K−2 without doping, surpassing other neutral organic conjugated polymer and radical conductors. Notably, PBBT−TT exhibits remarkable ambient stability, retaining its initial thermoelectric performance over a 120−day period. Our finding demonstrates that modulating the intermolecular spin interactions in open‐shell polymers through the introduction of strong proquinoidal units is an effective strategy for the development of doping−free, intrinsically high−performance polymer thermoelectric materials.