Rationalization of Microstructure Modulation and Doping on the Enhancement Mechanism of Thermoelectric Properties of PEDOT:PSS

Abstract

As wearable electronic devices advance, there is a growing demand for stand-alone flexible thermoelectric materials and devices capable of harvesting low-grade thermal energy from human skin. The polar molecule DMSO is known to enhance the electrical properties of PEDOT, with the underlying mechanism believed to involve structural changes in PEDOT that improve carrier mobility, although carrier concentration has a more pronounced effect on conductivity. In this study, we examined the impact of varying DMSO concentrations on PEDOT. With the optimal addition of DMSO (10 vol.%), PSS and PEDOT were effectively separated, resulting in parallel lamellar microstructures that improved the continuity of the conductive network. Hall effect measurements showed significant increases in both carrier concentration and mobility. The PEDOT⁺ polaritons were arranged parallel to the lamellar structure, facilitating rapid charge transport along the molecular chains. This arrangement led to enhanced three-dimensional charge transfer, increased π-π conjugate stacking between microstructural layers, and a greater electron cloud density. The synergistic effect of these changes resulted in a three-fold increase in film conductivity. Additionally, lightly doping PEDOT with DMSO led to a 35% increase in the Seebeck coefficient with rising operating temperatures. The resulting free-standing, flexible films, characterized by low thermal conductivity and high electrical conductivity, are well-suited for use in miniature flexible sensors or wearable electronic devices.