An all-sol-gel electrochromic (EC) device was constructed of electrochromic WO3 and transparent Pt films, both deposited on conductive glass electrodes encapsulating a gel electrolyte with an I-3(-)/I- redox couple. WO3 films (200-400 nm) were deposited by the dip-coating technique from peroxopolytungstic acid sols. The films consisted of nanocrystalline WO3 grains of dimensions 20-30 nm having monoclinic structure. The gel redox I-3(-)/I- electrolyte, which was made via the sol-gel route, consisted of an organic phase (poly(propyleneglycol), PPG, M-W = 4000) covalently bonded via urea bridging groups to a silica phase. Gelation was performed with acetic or valeric acid.The functioning of the device was studied by the micro-resonance Raman spectroscopic technique, focusing the laser excitation line (lambda = 647 nm) on the electrolyte encapsulated in the EC device. Variation in the potential from - 2 to 2 V (scan rate 5 mV s(-1)) resulted in changes of the intensity of the symmetric stretching resonance Raman mode of I-3(-) ions (v(s)(I-3(-))) and was accompanied by variation in the background Rayleigh scattering, From this, we concluded that the intercalation/deintercalation of K+ ions in the WO3 film was accompanied by an increase/decrease in the I-3(-) ion concentrations and reversible dissociation/association of the KI microcrystallites existing in the redox electrolyte. (C) 2003 Elsevier B.V. All rights reserved.