Tungsten oxide thin films prepared by a dip-coating process show great promise as the electrochromic layer in optically switchable windows. Current models describe the electrochemical response of electrochromic evaporated or anodized WO3 thin films, using conventional chronoamperometric theory applied to a two-dimensional electrode. Here, we place emphasis on electrochemical ion diffusion in and through a non-two-dimensional thin- film electrode using a liquid electrolyte, in order to characterize the current-time (i-t) and current-voltage response. In particular, these characteristics can be related to the thickness, surface roughness and microstructure of the film using fractal theory. Complimentary microstructural analyses of these films are carried out using electron and atomic force microscopic techniques, with particular attention focussed on the effects of ion intercalation on the microstructure of sol-gel deposited thin films.
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