One-step post-treatment boosts thermoelectric properties of PEDOT:PSS flexible thin films

Developing high-performance poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) significantly widens the practical applications of flexible organic thermoelectric devices, while the water-based co-solvent dopants and/or post-treatments are still rarely studied so far. Here, we develop a one-step post-treatment to improve the power factor of PEDOT:PSS films by using a water-based solution, which is composed of co-solvent (polar solvent dimethylacetamide (DMAC) and deionized water) and organic reducing agent L-ascorbic acid (LAA). The 80 vol.% DMAC solution significantly boosts the room-temperature electrical conductivity of the films from 5 to 964 S cm(-1), while the Seebeck coefficient can be further enhanced from 18.7 to 25 mu V K-1 by treating with 0.5 mol L-1 LAA, contributing to a significantly improved power factor of 55.3 mu W m(-1) K-2. The boosted electrical conductivity is ascribed to the separated PEDOT and PSS phases triggered by the high dielectric constant and polarity of DMAC; while the improved Seebeck coefficient is attributed to the reduced oxidation degree of PEDOT from the reducing agent LAA, both confirmed by the comprehensive structural and morphological characterizations. Furthermore, a maximum power factor of 64.4 mu W m(-1) K-2 can be achieved at 360 K and the observed temperature-dependent electrical transport behavior can be well explained by the Mott variable range hopping model. Besides, a flexible thermoelectric device, assembled by the as-fabricated PEDOT:PSS films, exhibits a maximum output power of similar to 23 nW at a temperature difference of 25 K, indicating the potential for applying to low-grade wearable electronics. (C) 2022 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

This study develops a one-step post-treatment method using a water-based solution to improve the power factor of PEDOT:PSS films. By using a DMAC solution and LAA reducing agent, the electrical conductivity and Seebeck coefficient of the films are enhanced, resulting in an improved power factor. The research also demonstrates a flexible thermoelectric device assembled with PEDOT:PSS films showing high output power at a temperature difference of 25 K.