High-performance thermoelectric PEDOT:PSS fiber bundles via rational ionic liquid treatment

• A new strategy involving the addition of MMIM:DCA and dual post-treatment is applied in PEDOT:PSS fiber bundle. • High power factor of 91.8 μW m −1 K −2 is achieved at 25 °C. • Comprehensive micro/nanostructural characterizations confirm the outstanding performance. • A p-n fiber-based TED is designed to evaluate the application potential of the fibers. • At a Δ T of 25 K, the device exhibited a high power density of up to 36.76 μW cm −2 . Rapid growth of wearable technology generates increasing demand for lightweight and elastic energy harvesting systems. Among them, conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) shows great potential for lightweight and flexible thermoelectric generators. However, the practical applications of PEDOT:PSS have been restricted by the low Seebeck coefficient and power factor. Here, PEDOT:PSS/1,3-dimethylimidazolium dicyanamide (MMIM:DCA) fiber bundles with enhanced thermoelectric performance have been fabricated by optimizing the content of ionic liquids (ILs), and the duration of dual post-treatment with H 2 SO 4 and NaBH 4 . The as-prepared fiber bundles exhibit a high power factor of 91.8 μW/m K −2 at 298 K. Detailed characterizations confirm that the phase separation and structural rearrangement of the polymer chains triggered by ILs ensure high charge carrier mobility, resulting in increased electrical conductivity. Meanwhile, the strong binding of DCA − to the PEDOT structure, combined with the hydrophilicity and potent reducing effect of MMIM + , synergistically alters the oxidation state of PEDOT, leading to an enhanced Seebeck coefficient. Moreover, the assembled flexible fiber bundle thermoelectric devices exhibit superior performance and usability, which show an output power density of 36.76 μW cm −2 with a temperature gradient of 25 K. This work offers valuable insights into the development of high-performance organic thermoelectric materials via the modulation of polymer chains.