Free-standing thermoelectric nanocomposite based on PEDOT:PSS, Cu 12+ x Sb 4 S 13 , and MWCNTs

Conductive polymers are promising candidates for thermoelectric (TE) applications due to their lightweight, solution processability, and mechanical flexibility, making them ideal for flexible and portable TE devices. However, their thermoelectric performance remains limited compared to inorganic semiconductors.In this study, we developed PEDOT:PSS-based nanocomposites incorporating Cu12+xSb4S13 tetrahedrites (TH) and multiwalled carbon nanotubes (MWCNT) to enhance their thermoelectric properties. Tetrahedrites, synthesized via solvothermal method, exhibit ultra-low thermal conductivity (0.25 W·m-1·K-1 at 300 K) and a tunable Seebeck coefficient (150–400 μV·K-1). The combination of tetrahedrite’s high Seebeck coefficient and low thermal conductivity with the excellent electrical conductivity and mechanical properties of MWCNTs provides a synergistic strategy for improving PEDOT:PSS performance.Flexible, free-standing composite films were fabricated using a simple drop-casting technique. Structural and microstructural properties were systematically analyzed using a comprehensive set of techniques including XRD, FTIR, XPS, SEM, and TEM. For the first time, spatially resolved Seebeck coefficient measurements of polymer composite films were performed using Scanning Thermoelectric Microscopy (SThM), providing new insights into their thermoelectric homogeneity.The optimized composite containing 20% TH and 5% MWCNTs showed a more than twofold increase in power factor compared to pristine PEDOT:PSS, reaching approximately 49.5 μW·m-1·K-2 at room temperature. These findings provide valuable insights into the interplay between composition, microstructure, and thermoelectric performance, offering guidance for the design of efficient and flexible thermoelectric materials.Additionally, a prototype thermoelectric generator was fabricated using the best composite, demonstrating the potential of these materials for energy-harvesting applications.