Properties of mixed-oxide MoO3/V2O5 electrochromic films coated from peroxo-polymolybdovanadate solutions

Peroxo-polymolybdovanadates with various mole ratios of Mo/V are formed by direct reaction of a mixture of metallic Mo and V with hydrogen peroxide solution. Homogeneous amorphous thin films about 0.4 mu m are fabricated on an ITO glass substrate by a spin-coating technique using the peroxo-polymolybdovanadate solutions. After heat-treatment at a desired temperature (80-120 degrees C) in air for 1 h, they show reversible electrochromism in an organic Li-electrolyte solution, and change color between greenish yellow and violet. The potential (E) versus composition (x, Li content per mole of MoyV1-yOz) diagrams for these mixed films could be approximated by two straight lines with different slopes, which suggests that in these films there are two kinds of sites with different site energies. The changes in electrochromism with heat-treatment are also discussed in relation to the micro-structure of the films.