Using the ink with the nanoparticles of Prussian blue-type complex, we have developed electrochromic devices by using a transparent electrode onto which fine metal wires have been printed. The devices realize high transmittance and reflectance without lowering response speed. The electrochromic device also reduces the amount of the rare metal, indium.

The fine metal wires were formed by printing with gold nanoparticle ink using the super inkjet method, an original technology of AIST. The developed electrochromic devices display a color change from white to yellow when a voltage of 1.5 V or less is applied. When white, the reflectance exceeds 55 % in most of the visible light region. The realized response speed is approximately eight times higher than when fine metal wires are not applied. No significant drop in speed was observed even after 1,000 cycles. This technology is expected to be effective in the production of larger area light-control glass, electronic paper, and other devices using electrochromic devices.