Interactions in Electrodeposited Poly-3,4-Ethylenedioxythiophene-Tungsten Oxide Composite Films Studied with Spectroelectrochemistry

Cyclic voltammograms and optical absorption spectra of PEDOT/WO₃ composite films were recorded in order to identify possible interactions and modes of improved performance of the composite as compared to the single materials. Changes in the shape of redox peaks related to the W(VI)/W(V) couple in the CVs of WO₃ and the composite PEDOT/WO₃ films indicate electrostatic interactions between the negatively charged tungsten oxide species and the positively charged conducting polymer. Smaller peak separation suggests a more reversible redox process due to the presence of the conducting polymer matrix, accelerating electron transfer between tungsten ions. Electronic absorption spectra of the materials were analyzed with respect to changes of the shapes of the spectra and characteristic band positions. There are no noticeable changes in the position of the electronic absorption bands of the main chromophores in the electronic spectra of the composite film. Obviously, the interactions accelerating the redox performance do not show up in the optical spectra. This suggests that the existing electrostatic interactions in the composite do not significantly change the opto-electronic properties of components of the composite but resulted in the redistribution of fractions of polaron and bipolaron forms in the polymer.