CONSTANT PHASE-ANGLE BEHAVIOR OF SNO2 WO3 THIN-FILM ELECTRODES IN ANHYDROUS LICLO4-PROPYLENE CARBONATE ELECTROLYTE/

Electrochromism in WO3 evaporated thin films can be used in many pract ical devices. These systems are made of tungsten trioxide vacuum evapo rated onto transparent and conductive substrates, ie fluorine doped ti n oxide (SnO2:F) or indium-tin oxide (ITO). In this study, impedance s pectroscopy is used to characterize the bilayered electrode. A constan t phase angle (CPA) behavior in the low frequency range and a pseudo-c apacitive-resistive parallel electrical circuit at intermediate freque ncy are observed. The influence on the impedance data of the amplitude of the ac signal, the cell temperature and the electrode geometry is studied. This approach allows us to present an electrical model for th ese bilayered non-colored electrodes.