Effect of solution pH value on thermoelectric performance of free-standing PEDOT:PSS films

• Conducting polymer PEDOT:PSS was used as an organic thermoelectric (TE) material.
• Low PH value (acidic condition) enhances the TE performance of PEDOT:PSS.
• High PH value (alkaline condition) decreases the TE performance of PEDOT:PSS.
• The recovery of TE performance after a second treatment with acid was studied.

Dependence of the thermoelectric (TE) performance of free-standing poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) composite films on the pH value in aqueous solution treated by acids and alkalis were systematically investigated. The TE performance can be enhanced by decreasing the pH value (acidic conditions), while it decreases rapidly with the increase in pH value (alkaline conditions). Carrier mobility and concentration, as well as morphology and structure characterizations of free-standing PEDOT:PSS films demonstrated that the pH value of the solution significantly affects their TE properties. With the maximum power factor of 1.35 W m−1 K−2 and the highest Seebeck coefficient of 40.7 μV/K, are promising organic thermoelectric materials.