Doping-undoping process electrochromic devices

An electrochromic display (BCD) is a thin solid state device that changes color reversibly when subjected to a small electrical potential. Since the doping processes of certain conducting polymers are accompanied by changes in the color, this effect has been conveniently exploited in the realization of BCD devices. Thin films of a conducting polymer polythiophene, for example, are red in the doped state and deep blue in the undoped state. 

The device by Corradini et al uses an ITO counter-electrode at which occurs, without significant colour change, an electrochemical process that is presumably due to lithium ion insertion and involves up to ca. 7.5mCcm [29]. Figure 7.7 shows the transmittance in the visible and IR regions of the electrochromic-electrode in the undoped and doped states as well as of the ITO counter-electrode before and after lithium insertion. 

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