Electrochromic materials for electronic paper

Electrochromic materials have the possibility to change their colour reversibly when they are transformed in a differently charged state. By applying an external voltage, charged molecules move towards the electrodes where they accept or donate an electron, and obtain a different colour. When the external voltage is switched off, they return to their initial colour. Recently electrochromism has become very popular because of possible application in electronic paper. Important properties of electrochromic materials are switching time, diffusion and reaction speed. Electrical and optical measurements of electrochromic cells are presented.