Effect of SWCNT, ferrocene, and cobalt oxide on the thermoelectric performance of PEDOT:PSS-based composite films

Abstract In this study, PEDOT:PSS-based thermoelectric composites were fabricated using a multi-component doping strategy incorporating single-walled carbon nanotubes (SWCNTs), ferrocene, and cobalt oxide. The novelty of this work lies in the synergistic combination of polymer, carbon nanostructures, and metal oxide additives, which has been rarely explored in polymer thermoelectrics. Four samples were prepared—undoped PEDOT:PSS, PEDOT:PSS–SWCNT, PEDOT:PSS–ferrocene–cobalt oxide, and PEDOT:PSS–SWCNT–ferrocene–cobalt oxide—to systematically investigate the effects of each dopant and their combination on thermoelectric performance. Structural and compositional integrity of the composites was confirmed by Raman spectroscopy, which verified the presence of SWCNTs, cobalt oxide, and the PEDOT:PSS matrix. Electrical conductivity increased significantly with SWCNT incorporation, reaching ~ 139.6 S/m in the fully doped sample. All composites exhibited positive Seebeck coefficients, confirming p-type behavior, while thermal conductivity remained within the typical polymer range (57.4–199.0 mW/m·K). The multi-component doping led to a dramatic improvement in the figure of merit (zT), reaching 3.158 × 10⁻ 4 —nearly 90 times higher than pristine PEDOT:PSS. These results demonstrate that tailored multi-dopant engineering is a promising route for tuning the thermoelectric properties of polymer-based composites, providing insights for the development of flexible and high-performance thermoelectric materials.