Films of solid polymer electrolyte (spe) have been prepared by the photo-polymerization of the monomer: 2-hydroxyethylmethacrylate (HEMA) simultaneously accompanied by chemical crosslinking with neopentyl glycol which is dissolved in a liquid electrolyte, namely, 1 M LiClO4 in EC:PC binary solvent mixed in two different volume ratios. The spe films exhibit ionic conductivities greater than 10-3 S cm-1 at 25°C. Thermal and structural characteristics of the films have been determined by DSC and XRD, respectively. The electrochemical redox behavior of an electrochromic device (PWECD) fabricated with an electrodeposited tungsten oxide film as the primary electrode, a prussian blue film as the counter electrode and a poly(HEMA) based electrolyte film as well as that of the individual components of the device has been examined by cyclic voltammetry. Transmission modulation of ∼60% (λ = 650 nm) shown by the PWECD renders it to be a promising candidate for electrochromic window applications. © 2003 Elsevier Science B.V. All rights reserved.