Poly(3,4-ethylenedioxythiophene): Chemical Synthesis, Transport Properties, and Thermoelectric Devices

Since their discovery in the seventies, conducting polymers have been chemically designed to acquire specific optical and electrical properties for various applications. Poly(3,4-ethylenedioxythiophene) (PEDOT) is among the most successful polymers as indicated by approximate to 12 000 articles mentioning it to date. PEDOT is found as transparent polymer electrodes in solar cells and light-emitting diodes, as printed electrodes in transistors, and as the main component of electrochromic displays, supercapacitors, and electrochemical transistors. For around seven years, PEDOT has been classified as the first thermoelectric polymer that converts heat flow into electricity. This has triggered a renewed interest in the scientific community, with about 400 publications including the keyword "PEDOT" and "thermoelectric." Among the topics covered by those scientific works are: i) the optimization of the thermoelectric properties, ii) understanding of the interplay between electrical properties and morphology, iii) the origin of the Seebeck coefficient, iv) the characterization of its thermal conductivity; and v) the design of thermoelectric devices. This work aims to be a pedagogical introduction to PEDOT but also to review the state-of-the art of its thermoelectric properties and thermoelectric devices. Hopefully, this work will inspire scientists to find chemical design rules to bring organic thermoelectrics beyond PEDOT.