Electrochromic device

An electrochromic device, which comprises:

• a light transmission variable structure interposed between a first base layer and a second base layer,
• wherein the light transmission variable structure comprises a first chromic layer and a second chromic layer,
• the first chromic layer comprises a reducing chromic material,
• the second chromic layer comprises an oxidizing chromic material, and
• the value of c as defined in the following Equation 1 is 1.0 to 1.6:
• c=T2/T1×b/a [Equation 1]
• in Equation 1, T1 (coloring time) is the time (s) for which the transmittance of visible light changes from 65% to 15% when an electric power of 3V is applied to the electrochromic device, T2 (decoloring time) is the time (s) for which the transmittance of visible light changes from 15% to 65% when the current direction is reversed after the coloring time is measured, a is the thickness (nm) of the first chromic layer, and b is the thickness (nm) of the second chromic layer,
• wherein the b/a value is 1.5 to 2.2,
• wherein the electrochromic device further comprises a first barrier layer interposed between the first base layer and the light transmission variable structure;
• and a second barrier layer interposed between the second base layer and the light transmission variable structure, and
• wherein the first barrier layer and the second barrier layer each comprise two or more layers.