Controlling Electrostatic Interaction in PEDOT:PSS to Overcome Thermoelectric Tradeoff Relation

A high power factor must be achieved to improve the thermoelectric (TE) output of organic TE materials though the tradeoff between electrical conductivity and the Seebeck coefficient is a serious obstacle to the further development of these materials. Here, systematic control of the electrostatic interaction between a conducting polymer and a dopant induces a positive deviation from this TE tradeoff relation so that the electrical conductivity and the Seebeck coefficient simultaneously increase. Upon reduction of the electrostatic interaction, substantial changes in the film morphology, chain conformation, and crystalline ordering are observed, all of which critically affect the TE charge transport. As a result, the electrostatic interaction control is found to be an effective strategy to enhance the power factor, overcoming the tradeoff between TE parameters. Adapting this strategy to poly(3,4‐ethylenedioxythiophene):polystyrene‐sulfonate results in a remarkable power factor (=700.2 µW m−1 K−2 ) and figure of merit ZT (=0.25). The electrostatic interaction in poly(3,4‐ethylenedioxythiophene):polystyrene‐sulfonate (PEDOT:PSS) is systematically controlled by adding small‐molecule anions of different physical properties. This system facilitates effective charge transport and controls the oxidation level of PEDOT:PSS, which enhances the thermoelectric (TE) power factor to 700.2 µW m−1 K−2 by overcoming the TE tradeoff relation between the electrical conductivity and the Seebeck coefficient.