Abstract
The present invention provides an electrochromic device which includes a first transparent electrode, a second transparent electrode, and a chitosan solution filled between the first and the second transparent electrodes. When a voltage is applied to the first and second transparent electrodes, the transparency of the first transparent electrode serving as a cathode is changed by the deposition of chitosan on a surface of the first transparent electrode. The present invention further provides a colouring and bleaching processes of the electrochromic device.