Investigation of thermoelectric properties of high concentration PEDOT: PSS inks doped with graphene and multi-walled carbon nanotubes

The use of wearable technologies in various aspects of life, particularly in health and entertainment, is experiencing a remarkable increase. This intensity of usage brings with it the energy needs of these devices. Polymer-based thermoelectric generator solutions are one of the most emphasized issues in energy harvesting applications and stand out as a solution method. In this study, we introduce a high-concentration poly(3,4-ethylenedioxy-thiophene): polystyrene sulfonate (PEDOT: PSS)-based conductive polymer ink, which has been doped with graphene and multi-walled carbon nanotubes (MWCNT) for thermoelectric applications. We also explore the film properties derived from this ink. The fabrication process involves cryogenic freezing, lyophilization, and re-dispersion of a mixture of water and dimethyl sulfoxide (DMSO) with a commercial PEDOT: PSS aqueous solution, followed by the addition of specific additives. These added compounds have led to a significant increase in electrical conductivity, resulting in materials with high electrical conductivity levels ranging from 100 to 200 S/cm. Remarkably, even after subjecting the material to 100 bending cycles, no significant change in electrical conductivity was observed. All the materials produced exhibited p-type semiconductor properties, and the high concentration of PEDOT: PSS, along with the addition of graphene and multi-walled carbon nanotubes, notably enhanced the Seebeck coefficient, reaching a maximum of 25 μV K⁻1.