The electrochromic devices were constructed using electrochromic polymers coated on ITO separated by gel electrolyte from each other and have the ability of changing their optical properties as persistent and reversible response by the application of a voltage pulse. Gel electrolyte was prepared using tetrabutylammonium salts, acetonitrile, PMMA, and propylene carbonate. The electro-optical properties of the device were recorded in-situ under various applied potentials. Finally, square wave potential method was used to perform switching between the two colored states (reference and counter electrodes shorted together).
An ideal electrochromic device should switch between its different oxidation states with a certain response time and it should also be stable upon multiple switching. The charge passed at 95% of the full optical switch is selected to evaluate response time and the optical contrast since the color change has taken place mostly at that level and the last 5% of the color change is difficult to perceive with the naked eye. Another important parameter in the electrochromic device is the long cycle life.Coloration efficiency (CE) is a useful term for measuring the power efficiency of the electrochromic devices and can be calculated via optical density using the following equations;
where Qd is the injected/ejected charge during a redox step; Tcolored and Tbleached are the transmittance in the oxidized and neutral states, respectively.