Role of anionic surfactant addition in improving thermoelectric properties of PEDOT:PSS free-standing films

Abstract

Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) has recently gained interest as a potential candidate for small-scale thermoelectric conversion because of the facile doping, solution processability, and flexibility. However, the practical applications of PEDOT:PSS are limited by its comparatively low figure of merit (ZT) compared with inorganic thermoelectric materials. Herein, to further improve the thermoelectric properties of PEDOT:PSS, we investigated the role of the addition of surfactants, sodium dodecyl sulfate, sodium dodecyl benzenesulfonate (SDBS) or Triton X-100, to the PEDOT:PSS free-standing films on their thermoelectric properties. We showed that the addition of the surfactant improved the film crystallinity, significantly improving the electrical conductivity. The highest conductivity was obtained for anionic surfactant SDBS at a 0.94 wt% concentration. Moreover, the inclusion of the surfactant reduced the thermal conductivity while maintaining a relatively constant Seebeck coefficient, consequently improving the ZT value. Furthermore, a flexible thermoelectric device crafted from the as-fabricated PEDOT:PSS/SDBS sheets was developed to explore the potential applications of wearable electronics using low-grade thermal energy. Overall, we indicate the significance of surfactants in enhancing the thermoelectric properties of free-standing PEDOT:PSS films in this study.