Electrochemically tuning the thermoelectric performance of flexible polythiophene films by ionic liquid.

• Precise modulation of TE properties of PTh films by electrochemical doping. • The PF and σ of doped films were increased by 130 % and 315 %, respectively. • ILs is used instead of organic solvents in the electrochemical doping system. • The PTh film has excellent flexibility and metallic luster. As one of the new generations of green energy materials, thermoelectric materials enable the direct conversion of heat and electric energy, thus alleviating the pressure of energy crisis and environmental pollution. Organic thermoelectric (TE) materials can be used as candidate materials for flexible wearable electronic devices due to their low toxicity, low cost, and lightweight, among others. In this work, free-standing polythiophene (PTh) film was obtained by electrochemical deposition using boron trifluoride diethyl etherate (BFEE) as the electrolyte, and the prepared films were processed electrochemically in [EMIM]BF 4 ionic liquid. The UV–Visible absorption spectroscopy of PTh films at different constant potentials from -0.2 to 1.0 V illustrated that electrochemical treatment could modulate the doping states of the PTh film. The power factor and electrical conductivity of the PTh film treated at 0.4 V reached the maximum values of 2.91 S cm−1 and 2.59 μW m−1 K−2, respectively, an improvement of 315% and 130% compared with the pristine film. The results indicate that electrochemically doped is an effective method for modulating the thermoelectric performance of polymer films, providing enlightenment for obtaining high-performance organic thermoelectric material henceforth. [ABSTRACT FROM AUTHOR]