ELECTROCHROMIC AND PHOTOELECTROCHROMIC BEHAVIOR OF THIN WO3 FILMS PREPARED FROM QUANTUM-SIZE COLLOIDAL PARTICLES

Thin films of WO3 are cast from quantum size colloids onto an opticall y transparent electrode. These thin particulate films are found to exh ibit reversible electrochromic and photoelectrochromic effects. A blue coloration of the WO3 particulate film is seen when electrons are inj ected into the conduction band of WO3 by electrochemical or UV-excitat ion methods. The onset potential of the electrochromic effect is depen dent on the pH and corresponds to the flat band potential of WO3. Spec troelectrochemical and microwave absorption experiments suggest that t rapped electrons are the major species responsible for the blue colora tion of the WO3 particulate film.