Electrochromism is the reversible color change upon doping and dedoping. Recently, electrochromic devices (ECDs) have been actively pursued because of their various potential applications, such as electrochromic sunglasses, smart windows, data storage device, e-paper, and displays. In terms of the materials for these applications, fast response, and high color contrast, and stability are key elements to becoming a successful candidate. Further, to access the portable applications, lightness, flexibility, and low-power consumption are desired. To meet these needs, π-conjugated polymers(CPs) have intensively researched as a promising materials demonstrating a high coloration efficiency, fast response, and high reversibility.1 As these properties are influenced by not only the chemical structure of EC materials but also by the electrochromic reaction in a device, both factors are crucial. Of the various electrochromic CPs, the transmittance changes of the poly(3,4-propylenedioxythiophene) derivatives (PRs) having different side groups can reach high color contrast maintaining the high cycle stability. We synthesized several PRs for high color contrast and bistability.2 Further control on the potential at both working electrode and counter electrode, through charge balancing reactions, afforded ECDs with a high color contrast, long stability, and high bistability.3 Here, the optimum material combination for working electrode and counter electrode will be discussed along with charge balancing mechanism and demonstrate the application of the low-power consuming display into an automatic electrochromic windows.
1. P. M. Beaujuge and J. R. Reynolds, Chem. Rev., 2010, 110, 268-320.
2. H. Shin, S. Seo, C. Park, J. Na, M. Han and E. Kim, Energy. Environ. Sci., 2016, 9, 117-122.
3. Y. Kim, H. Shin, M. Han, S. Seo, W. Lee, J. Na, C. Park and E. Kim, Adv. Funct. Mater., 2017, 27, 1701192