A cycling plastic electrochromic device (not to scale) is illustrated below.

The outer two layers on each side of the device make up the flexible transparent conductive substrates. Typically, a substrate is transparent non-conductive plastic on which a transparent conductor is applied. Transparent conductive plastic substrates, such as indium-tin-oxide on polyethylene terephthalate, are commercially available.

Sandwiched between the transparent conductors are the Positive Electrochromic Layer, the Ion-Conducting Adhesive, and the Negative Electrochromic Layer. The electrochromic layers are where the color changes occur. These layers can be continuous coatings, printed patterns, or individually addressed pixels. When a small voltage is applied to the device, cations are removed from the Positive Electrochromic Layer and injected into the Negative Electrochromic Layer. As a result, both electrochromic layers color deeply.  When the voltage is reversed, cations are removed from the Negative Electrochromic Layer and injected into the Positive Electrochromic Layer. Both electrochromic layers  clear. The Ion-Conducting Adhesive allows the passage of cations, but prevents the passage of electrons so that the device does not short circuit electrically. The tint of the electrochromic device can be adjusted by setting the applied voltage.

Cycling Electrochromic Device