Free-Standing PEDOT-PSS/Ca3Co4O9 Composite Films as Novel Thermoelectric Materials

Free-standing poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT- PSS)/Ca3Co4O9 composite films have been successfully prepared by mechanically blending Ca3Co4O9 powder and PEDOT-PSS solution (Baytron P) and casting the mixed solution on polypropylene (PP) film substrates. X-ray diffraction (XRD) and scanning electron microscopy (SEM) characterization indicated that the Ca3Co4O9 particles were in the shape of sheets and composited well together with PEDOT-PSS. Thermoelectric (TE) measurements revealed that the Seebeck coefficient can be improved by increasing the Ca3Co4O9 content in the composite films, with the largest enhancement being 24.8% compared with a free-standing PEDOT-PSS film. However, it is also shown that the power factor of the composite films decreases with increasing Ca3Co4O9 content, mainly due to the decline of electrical conductivity and the limited improvement of the Seebeck coefficient.