Charge coloration dynamics of electrochromic amorphous tungsten oxide studied by simultaneous electrochemical and color impedance measurements

The coloration mechanisms in electrochromic (EC) systems can be probed by comparing the dynamics of electrical and optical responses. In this paper, linear frequency-dependent responses an amorphous tungsten oxide thin film were measured simultaneously a combination two techniques$\text{---}$that is, electrochemical impedance spectroscopy (EIS) so-called color (CIS). This was done at different bias potentials, which associated with intercalation levels. Equivalent circuit fitting to EIS spectra used extract Faradaic components participating total response. latter assigned intermediate adsorption step before diffusion electron-ion couple film. A quantity denoted complex capacitance is compared capacitance$\text{---}$in particular, their expressions are related processes. low levels followed both phenomena. Conversely, contribution dominant high one seemed negligible case. For perfectly synchronized responses, expected differ only multiplying factor. case levels, apart from small deviations frequencies. clear departure behavior observed as level increased. techniques, presented work, help understanding EC materials various conditions$\text{---}$for example, wavelengths.