Quinoid‐Resonant Conducting Polymers Achieve High Electrical Conductivity over 4000 S cm(−1) for Thermoelectrics

New conducting polymers polythieno[3,4‐b]thiophene‐Tosylate (PTbT‐Tos) are prepared by solution casting polymerization. Through tuning the alkyl group of TbT, the electrical conductivity can be effectively enhanced from 0.0001 to 450 S cm(−1). Interestingly, the electrical conductivity of PTbT‐C1‐Tos increases significantly from 450 S cm(−1) at room temperature to 4444 S cm(−1) at 370 K, which is disparate from polyethylenedioxythiophene‐Tos exhibiting metallic conducting behavior. Quasi‐reversible phase transformation with temperature from 3D crystallites to lamellar‐stacking coincides with the increasing electrical conductivity of PTbT‐C1‐Tos with heating. Methyl‐substituted PTbT‐Tos with the best electrical property is further utilized for thermoelectrics and a power factor as high as 263 µW m(−1) K(−1) is obtained. It is believed that PTbT‐Tos will be a promising family of conducting polymers for solution‐processed organic electronics.