Significant Enhancement in the Thermoelectric Properties of PEDOT:PSS Films through a Treatment with Organic Solutions of Inorganic Salts

Conducting polymers have promising thermoelectric application because they have many advantages including abundant elements, mechanical flexibility, and nontoxicity. The thermoelectric properties of conducting polymers strongly depend on their chemical structure and microstructure. Here, we report a novel and facile method to significantly enhance the thermoelectric properties of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films through a treatment with organic solutions of inorganic salts. N,N-Dimethylformamide (DMF) and a common inorganic salt like zinc chloride (ZnCl2) are used as the solvent and solute of the solutions, respectively. The treatments can significantly increase both the Seebeck coefficient and electrical conductivity of the PEDOT:PSS films The thermoelectric properties of the PEDOT:PSS films are sensitive to the experimental conditions, such as the salt concentration, treatment temperature, and the cation of the salts. After treatment at the optimal experimental conditions, the PEDOT:PSS films can exhibit a Seebeck coefficient of 26.1 mu V/K and an electrical conductivity of over 1400 S/cm at room temperature. The corresponding power factor is 98.2 mu W/(m.K-2) The mechanism for the enhancement in the thermoelectric properties is attributed to the segregation of some PSSH chains from PEDOT:PSS and the conformation change of PEDOT chains as a result of the synergetic effects of inorganic salts and DMF.