Enhanced Thermoelectric Performance of PEDOT:PSS Films by Sequential Post‐Treatment with Formamide

Abstract This paper reports a series of sequential post‐treatments using a polar solvent formamide to enhance the thermoelectric performance of poly(3,4‐ethylenedioxythiophene) doped with poly(styrene sulfonate) anions (PEDOT:PSS). The electrical conductivity of PEDOT:PSS films significantly increases from 0.33 S cm −1 for the pristine film to ≈2929 S cm −1 for the treated film and meanwhile the Seebeck coefficient maintains as high as 17.4 µV K −1 , resulting in a power factor of 88.7 µW m −1 K −2 . Formamide is a polar solvent with a high boiling point of 210 °C and high dielectric constant of 109, and PSS has a good solubility in it. Post‐treatment with formamide causes not only the phase segregation of PEDOT and PSS but also the removal of insulating PSS, therefore leading to the reorientation of PEDOT chains and enhancement in mobility without altering the doping level considerably. The cross‐plane thermal conductivity also reduces from 0.54 to 0.19 W m −1 K −1 after the post‐treatment, leading to a figure of merit ( ZT ) value of 0.04 at room temperature.