ISOTOPIC EFFECTS IN CATION-INJECTED ELECTROCHROMIC FILMS

The elucidation of the role that injected cations play in the creation of electrochromic (EC) color centers in hydrated WO3 films is present ed. The electron and cation contributions to the lattice distortion up on film coloration have been evaluated. The evolution of the fundament al absorption edge and vibrational bands of crystalline hydrate films of the WO3 . n(H2O) (n = 2, 1/3) was monitored in situ in a spectroele ctrochemical cell during the coloration process by visible and Fourier transform Raman spectroscopy. The electrochromic performance and film stability were studied using cyclic voltammetry and spectroelectroche mistry. Isotopic effects of blue shift of the fundamental absorption e dge and vibrational band shifts upon film coloration with H+ and D+ ca tions at the same charge density have been found, The analysis of vibr ational band shifts during electrochromic coloration with H+ and D+ ca tions indicates that along with the lattice polarization induced by in jected electrons forming polarons, a strong lattice distortion generat ed by inserted cations is occurring as well. An explanation of the ori gin of the blue shift of optical gap energy upon coloration by three d ifferent effects of the electronic structure rearrangement is proposed .