Electrochromism of mixed tungsten-vanadium oxide thin films grown by pulsed laser deposition

Mixed vanadium tungsten oxide thin films were grown in oxygen atmosphere using pulsed laser deposition. With the oxygen pressure fixed to an optimized value of 10 (-1) mbar, the influence of the substrate temperature and the film composition (i.e., vanadium content) on the electrochromism properties were studied. Whatever the film composition, films deposited on SnO2:F coated glass substrate were amorphous when deposited at room temperature while W-V-O (V<20%) films, deposited at 400C, exhibited X-ray characteristics similar to those of monoclinic WO3, suggesting a W1 - xVxO3-y solid solution. As a general trend, when V-based WO3 films cycle in protonic medium, both the cell capacity and the coloration efficiency decrease as the vanadium content increases. Upon very early cycling, a preferred reduction of the vanadium ions is observed with no further oxidation. Films containing a low amount of vanadium were more neutral in color than pure tungsten oxide. (C) 2001 The Electrochemical Society. All rights reserved.