Enhancement of Conductivity and Thermoelectric Property of PEDOT:PSS via Acid Doping and Single Post‐Treatment for Flexible Power Generator

Abstract Poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is a promising thermoelectric (TE) material. Nonetheless, its practical application is hindered by the poor TE properties of the pristine PEDOT:PSS and complicated treatment procedures. Enhancing its electrical conductivity is a key step for the improvement of TE properties. Here, a simple method is introduced to enhance the conductivity by adding sulfonic acid into the PEDOT:PSS solution. A systematic study of representative sulfonic acids with various functional groups suggests that steric effect induced by the functional groups has remarkable impact on the conductivity. The highest conductivity of 1996 S cm−1 is observed in benzenesulfonic acid‐doped PEDOT:PSS films. The doped PEDOT:PSS films are further treated with dimethyl sulfoxide and hydrazine successively or synchronously to tune the oxidation level. A maximum power factor (PF) of 203.1 µW m−1 K−2 is obtained. The high PF of treated PEDOT:PSS allows the realization of a flexible thermoelectric generator, which can generate 4.6 mV thermovoltage when attached on human skin. It also shows a good linear response with the increase of temperature difference; thus, it can be potentially used as a flexible thermal sensor. The facile fabrication process and good TE performance provide PEDOT:PSS an opportunity in wearable electronics.