ISOTOPIC EFFECT IN EVOLUTION OF STRUCTURE AND OPTICAL GAP DURING ELECTROCHROMIC COLORATION OF WO3-CENTER-DOT-1 3(H2O) FILMS/

Evolution of the fundamental absorption edge and structure of WO3 . 1/ 3(H2O) films during electrochromic (EC) coloration with different cati ons has been studied in situ by optical and Fourier transform Raman sp ectroscopy to clarify the role of inserted cations. With EC coloration , different high-energy shifts of the optical gap have been observed i n the absorption spectra of the films coloured with H+ and D+ ions. Th e shift magnitude for coloration with H+ ions is about twice that for coloration with D+ ions at the same electron density. Analysis of the shifts of the vibration bands during EC coloration with H+ and D+ ions has shown that along with a lattice polarization induced by the injec ted electrons forming the polarons, a strong lattice distortion produc ed by inserted ions occurs as well. The large isotopic effect shows th at the electronic structure of WO-octahedra is very sensitive to ion-i nsertion, and the electron rearrangement depends not only on the charg e and radius of the inserted ions but also on their mass.