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.