Electrocoloration curve analysis in WO3 thin films

An analytical expression for electrochromic coloration of WO3 amorphous thi n films is proposed based on a semiclassical equation for harmonic oscillat or and in the Smakula's formula. The coloration efficiency (eta) as a funct ion of the photon energy (hv) of the light-beam chosen to determine the cha nge in the optical density with the amount of injected electrical charge in to the film, was deduced in the range 0.5-3.0 eV (400-2500 nm). Given the o scillator strength constant value and the refraction index as a function of hv, eta can be determined, with good approximation, for any value of the p hoton energy in the range 0.5-3.0 eV. The usefulness of the method is demon strated on data obtained from the literature. (C) 2001 Elsevier Science B.V . All rights reserved.