The thermoelectric performance of poly(3,4-ethylenedioxythiophene) complexed with a poly(4-styrenesulfonic acid) (PEDOT:PSS) film was enhanced by a three-step process. First, ultrafiltration was applied to remove non-complexed PSS from PEDOT:PSS grains. The ultrafiltration treatment leads to an improvement in the power factor (S2σ) from 54.9 to 83.2 μW m−1 K−2 and a decrease in the thermal conductivity (κ) from 0.330 to 0.170 W m−1 K−1. Second, the fully de-doped PEDOT:PSS solution was prepared by addition of hydrazine, which acted as a reducing agent. Third, the two PEDOT:PSS solutions (ultrafiltered and hydrazine-treated) were mixed in different ratios by simple ultrasonication blending without any post-treatment. The optimal S2σ value of 115.5 μW m−1 K−2 (∼10 times higher than that of the pristine PEDOT:PSS film) and ZT value of 0.2 were recorded at 33 wt% of the hydrazine-treated, ultrafiltered PEDOT:PSS in the blend.
