ELECTROCHROMISM IN TITANYL AND VANADYL PHTHALOCYANINE THIN-FILMS

The electrochromic behaviour of titanyl phthalocyanine [Ti(O)(pc)] and vanadyl phthalocyanine [V(O)(pc)] thin films are reported. These materials manifest a reversible electrochromic change when reduced, but upon oxidation they show evidence of immediate destructive breakdown. The behaviour of the films is discussed in relation to the alpha- and beta-phase structures of the films. It is found that the phase of [Ti(O)(pc)] changes during the electrochromic process owing to ion incorporation. This is the first report of an electrochromically induced phase change in metal phthalocyanine materials. The structure of the phase present in a metal phthalocyanine material is found to dictate whether or not it is electrochromic. If the structure is too closely packed to allow ion penetration, it will not be electrochromic. The implications of the irreversible oxidations are discussed in relation to the behaviour of metal bisphthalocyanine electrochromic materials.