Electrochromic behavior of amorphous cobaltphthalocyanine thin films

Amorphous cobaltphthalocyanine thin films were prepared by vacuun evaporation, and their electrochromic behavior and voltammograms were examined in LiClO4, KNO3, KCl and MgCl2 aqueous electrolytes. The amorphous thin films prepared at the substrate temperature of −120°C, clearly exhibited electrochromism in LiClO4 and KNO3 aqueous electrolytes. The specimen films underwent five color transitions (from blue to red-violet, then to blue, then to green, then to yellow-green and then to blue) corresponding to the five peaks on the voltammograms in LiClO4 aqueous electrolyte. The amorphous films which were evaporated in low vacuum (1.33 × 10−1 Pa) exhibited electrochromism more clearly, compared to those evaporated in high vacuum (1.33 × 10−4 Pa). Because the former films are low in density, it is easy for anions to be injected and extracted in the films.