Principle of Electrochromism


 
Electrochromic device for light transmittance modulation (© Fraunhofer ISC).

Electrochromism involves electroactive materials that show a reversible colour change when a small DC voltage is applied. The potential causes redox reactions to take place in the electrochromic and ion storage layers, a process which is accompanied by ion migration across the ion-conducting layer to achieve charge compensation. The material and physical composition of 
electrochromic devices can vary strongly.
   
Colour change of an all-plastic electrochromic device. Left picture: Blue-coloured state; Right picture: Transparent state.
Flexibility of an all-plastic electrochromic device.

All photographs by courtesy of CIDETEC, San Sebastian, Spain.