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

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.