One‐Step Side‐Chain Cleaving and In Situ Doping of Open‐Shell Thermoelectric Polymers

ABSTRACT Open‐shell conjugated polymers are promising thermoelectric (TE) materials due to their intrinsic pro‐quinoid structure and radical characteristics. Nevertheless, the charge transport properties of these polymers are often limited by structural disorder and air sensitivity. In this work, we developed a one‐step “cleaving and doping” strategy to achieve highly conductive side‐chain‐free open‐shell polymers. The treatment of solid films of three benzo[1,2‐c;4,5‐c’]bisthiadiazole (BBT)‐based open‐shell polymers, namely PBBTSi‐T, PBBTSi‐2T, and PBBTSi‐TVT, with trifluoromethanesulfonic acid (TfOH) effectively cleaved the insulating silane side chains while simultaneously doping the polymer backbone in situ. This one‐step process yields a highly ordered molecular packing and efficient doping without any additional dopants, thereby synergistically optimizing carrier mobility and carrier concentration of films. The side‐chain‐free polymer, PBBT‐2T, reaches a maximum conductivity of 358.5 S cm −1 and a maximum power factor of 41.4 µW m −1 K −2 . These values rank among the highest ever reported for open‐shell polymers. Moreover, the resulting films exhibit excellent stability in air and at elevated temperatures. This study demonstrates a powerful approach for achieving high‐performance and stable open‐shell TE polymers.