Effective ionic Seebeck component suppression in mixed ion-electron conductor via chemical treatment

By employing time-dependent open-circuit voltage measurement, we demonstrate that a redundant ionic Seebeck component in the mixed ion-electron conducting polymer PEDOT:PSS can be suppressed by simple chemical treatments. The suppression of ionic Seebeck can be attributed to both increase in electronic conductivity and reduction in ionic conductivity, which results in a significant increase in the ratio of electronic-to-ionic conductivity. The thermogravimetric analysis and thickness swelling test confirm that PEDOT:PSS film becomes less or non-hygroscopic after treatment. Low hygroscopicity in the PEDOT:PSS film effectively cuts off the moisture-assisted ion conducting channel, consequently the ionic conductivity becomes extremely low and the ionic Seebeck component is suppressed even at a high humidity (90% RH) condition. The chemical treatment turns out to be a highly promising method to eliminate ionic Seebeck component in the mixed ion-electron conducting polymers and thus to generate consistent thermovoltage for the practical thermoelectric application.