Effects of one- and two-dimensional carbon hybridization of PEDOT:PSS on the power factor of polymer thermoelectric energy conversion devices

We investigated the thermoelectric properties of polymer composites based on a conducting polymer and carbon materials with various dimensionalities. PEDOT:PSS as a conducting polymer matrix was successfully hybridized with graphene sheets and multi-walled carbon nanotubes through in situ polymerization of 3,4-ethlyenedioxythiophene monomers in an aqueous solution in the presence of the carbon materials dispersed by using a polymeric dispersant. The hybrid structures of PEDOT:PSS, graphene, and carbon nanotubes in the composite showed an electrical conductivity, Seebeck coefficient, and power factor of 689 S cm^-1, 23.2 μV K^-1, and 37.08 μW mK^-2, respectively, values that are much higher than those of pristine PEDOT:PSS, PEDOT:PSS/graphene, or PEDOT:PSS/carbon-nanotube composites. The thermoelectric figure of merit increased from 0.017 in the pristine PEDOT:PSS to 0.031 in the composite, corresponding to an 80% enhancement. We believe that the enhanced thermoelectric performance comes from the synergic effects of multi-component systems with excellent electrical bridging and electronic coupling between PEDOT and carbon materials.