| 초록 |
Electrochromic (EC) phenomena refer to a reversible optical change of a specific material during the electrochemical reactions. Since the EC properties of tungsten oxides were reported by S. K. Deb in 1969, EC devices have been studied extensively because they exhibit high color contrast and low voltage consumption. These features provide the basis for their applications in smart window, rear-view mirrors, information displays, and optical shutters. There are several parameters to evaluate the EC properties of materials and devices such as coloration efficiency, response time, life time, and memory effect. Among them, the memory effect is designated as color retention time under voltage-off condition, which can be utilized as an index of energy saving in the field of smart windows. On the other hand, it can be commonsensically accepted that using memory effects instead of voltage retention for the coloring (or bleaching) maintenance influences the life time of EC materials, since the voltage retention after the fully polarized surface of EC materials can induce the degradation. In general, organic EC materials have fast coloration speed under low voltage condition, but short cycle time during EC reactions. In this study, therefore, we investigate the EC long-term cyclability of P3HT [poly (3-hexyl thiophene)] by controlling voltage retention time. Furthermore, we estimate the optimal retention time for the redox reactions under consideration of memory effect at P3HT. This method using the memory effect suggests an easy way to maximize the long-term cyclialbity of EC materials. |
