Giant variable-range hopping conductance in polar solvent and sulfuric acid-treated poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS)

The electrical transport mechanism of sulfuric acid (SA) treated PEDOT:PSS films prepared from a PEDOT:PSS solution with dimethyl sulfoxide (DMSO) or ethylene glycol (EG) as an additive was studied. The SA treatment increased the electrical conductivity; the maximum conductivity at room temperature was 2622 S cm −1 . X-ray diffraction (XRD) patterns indicate that all the SA-treated samples consist of crystallites and amorphous regions. Assuming that the electrical conductivity of such a heterogeneous sample can be expressed as the sum of metallic band conduction and Mott variable-range hopping (VRH) conduction, the electrical conductivity of the SA-treated film in the range 21–301 K was decomposed into metallic band conductivity and VRH conductivity. The VRH conductivity is larger than the metallic band conductivity. Hall effect measurements indicate that delocalized band carriers are generated upon SA treatment. Giant VRH conductivities probably originate from hopping between energy bands in the crystallites and localized electronic levels.