New Methodology of Organic Electrochemical Synthesis - Fundamentals and Applications of Organic Electrochemistry - page 305

coloured by the electrochemical reaction, the
given image and information remain even after
a power cut.
Figure 7.6 shows a typical electrochromic
device consisting of a sandwiched structure of
electrolyte containing a chromic compound
with anode and cathode plates. To visualize
colour changes, a transparent electrode should
be used for the electrochemical reaction. The
chromic compounds used need to have
reversible redox properties, i.e. their radical
anion or radical cation state should be stable.
They may be fixed on a transparent electrode to
avoid colour reducing once a coloured state is
generated at a counter electrode. As described
in section 5.8.6, the use of a stable doping state
and the reversible colour changes of conducting
polymers for electrochromic applications is very
convenient. In addition, film-forming property
of electropolymerized conducting polymers is
advantageous. Multicoloured electrochromic
devices are obtained by stacking each cell,
showing their individual colours.
Figure 7.6 Mechanism of electrochromic
device