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

Abstract 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 (Na 2 SO 3 ) and formamide (CH 3 NO) 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 CH 3 NO reduces the excessive insulating PSS and thereby increases the electrical conductivity, while Na 2 SO 3 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.