Improvement of electrical conductivity of poly(3,4-ethylenedioxythiophene) (PEDOT) thin film

In order to improve the electrical conductivity of in-situ polymerized poly(3,4-ethylenedioxythiophene) (PEDOT) thin film, we investigated the effect of doping level and co-dopant on the electrical conductivity. Doping level of PEDOT thin film was determined by X-ray photoelectron spectroscopy (XPS) and it was found that the higher doping level led to higher electrical conductivity. We also used several kinds of codopants such as methanesulfunic acid, naphthalenesulfonic acid and p-toluenesulfonic acid to increase the conductivity of PEDOT. When methanesulfonic acid was used as co-dopant, electrical conductivity of PEDOT thin film increased up to 1,500 S/cm. It is considered that the enhanced conductivity resulted from higher interchain conduction or more expanded chain structure due to small dopant size of methanesulfunic acid.