Optimization of the thermoelectric performance of PEDOT:PSS–tetrahedrite (Cu12+xSb4S13) nanocomposites

• Innovative PEDOT:PSS–tetrahedrite composites were successfully developed for thermoelectric applications. • Novel solvothermal synthesis of Cu 12+x Sb 4 S 13 tetrahedrite using 1-(2-aminoethyl)piperazine resulted in ultra-low thermal conductivity (0.25 W·m −1 ·K −1 at 300 K) and a tunable Seebeck coefficient (150–400 μV·K −1 ) was applied. • Flexible composite processing : materials were fabricated as thin films (drop-coating) and pressed pellets (PECS at 393 K), with TH volume fractions ranging from 2 % to 98 %. • Enhanced thermoelectric properties : incorporation of TH nanoparticles increased the Seebeck coefficient while reducing thermal conductivity, reaching a ZT value of 0.12 at 473 K for Vf = 85.7 % . • Tailored shaping and improved mechanical robustness : pastes enable flexible shaping before pressing, allowing customized designs for thermoelectric devices. The unique properties of conductive polymers, such as flexibility, ease of processing, and low toxicity, make them highly promising for thermoelectric applications. A key strategy to enhance their thermoelectric performance while preserving these advantages is the development of polymer-inorganic composites. In this study, we introduce an innovative approach to both material composition and processing by designing PEDOT:PSS-based composites incorporating Cu 12+x Sb 4 S 13 tetrahedrite (TH) nanoparticles. The TH phase, synthesized via our recently developed solvothermal method using 1-(2-aminoethyl)piperazine as a solvent, exhibits ultra-low thermal conductivity (0.25 W·m −1 ·K −1 at 300 K) and a tunable Seebeck coefficient (150–400 μV·K −1 ), depending on Cu content. The composites were fabricated with TH volume fractions ranging from 2 % to 98 %. Initially prepared as pastes, they were subsequently shaped and consolidated into pellets using pulsed electric current sintering (PECS) at 393 K. For comparison, thin films with a higher polymer content were produced via drop-coating onto glass substrates. The incorporation of TH nanoparticles led to a simultaneous increase in the Seebeck coefficient and a reduction in thermal conductivity. The highest ZT value of 0.12 was achieved at 473 K for a composite containing 85.7 % TH by volume. These results demonstrate the potential of PEDOT:PSS-tetrahedrite composites as non-brittle, mechanically robust thermoelectric materials with versatile processing options for specialized applications.