Dual Post-Treatments Boost Thermoelectric Performance of PEDOT:PSS Films and Their Devices

Owing to intrinsically high electrical conductivity and low thermoelectric conductivity, poly(3,4-ethylenedioxithiophene):poly(styrenesulfonate) (PEDOT:PSS) shows promising thermoelectric properties. However, its relatively low power factor limits the practical applications of PEDOT:PSS. Here, unique dual post-treatments by sodium sulfite (Na₂SO₃) and formamide (CH₃NO) to boost the thermoelectric performance of flexible PEDOT:PSS films with an optimized power factor of 74.09 µW m^–1 K^–2 are used. Comprehensive characterizations confirm that CH₃NO reduces the excessive insulating PSS and thereby increases the electrical conductivity, while Na₂SO₃ lowers the reduction of the doping level of PEDOT, leading to an increased Seebeck coefficient. Furthermore, the rationally post-treated PEDOT:PSS films are assembled into a flexible thermoelectric device that exhibits an open-circuit voltage of 2.8 mV using the heat from the human arm and an output power density of 2.56 µW cm^–2 by a temperature difference of 25 K, indicating great potential for practical applications on sustainably charging low-grade wearable electronics.