Study of PEDOT conductive polymer films by admittance measurements

▶ Microwave technique to measure the conductivity of PEDOT films. ▶ PEDOT conductivity depends on its mesoscopic scale structure and oxidation level. ▶ Raman spectroscopy and SEM analysis to study structure and morphology of PEDOT. ▶ Microwave measurements allow determination of the macroscopic scale conductivity. ▶ Microwave measurements overcome problems related to the local structural defects and inhomogeneities of PEDOT. In this paper we propose the use of a microwave technique to measure the conductivity of poly(3,4-ethylenedioxythiophene) (PEDOT) films. The PEDOT layers were prepared by electropolymerization from aqueous solutions using both poly(sodium 4-styrene sulphonate) (NaPSS) and sodium dodecyl sulphate (NaDS) acting as monomer solubilizer and dopant for the polymer. The conductive properties of a series of samples produced under different synthesis conditions and characterized by different structures have been investigated by microwave measurements in the frequency range from 40 MHz to 40 GHz by using a Corbino disc geometry. Such technique allows to estimate the mean conductivity of the polymer samples overcoming the limitations of the measuring configurations typically imposed by the conventional d.c. measurements. The morphology of PEDOT films and the structure of polymer chains were studied by scanning electron microscopy (SEM) and Raman spectroscopy, respectively. The correlated morphological, structural and microwave analysis enabled us to evidence several factors that affect the macroscopic scale conductivity of the polymer sample films and to identify the conditions for preparation of PEDOT films with functional properties relevant to technological applications.