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KMID : 1059520220660030209
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Journal of the Korean Chemical Society
2022 Volume.66 No. 3 p.209 ~ p.217
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Improvement of Bleaching Performance of Photosensitive Electrochromic Device by the Additive of TEMPOL
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Song Seung-Han
Park Hee-Sung
Cho Churl-Hee
Hong Sung-Jun
Han Chi-Hwan
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Abstract
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We have developed photosensitive electrochromic smart windows that does not require any transparent conducting oxide (TCO) substrate. In our previous study, we demonstrated that a flexible film-type device made with a low temperature curing WO3 sol and TiO2 sol could show a reversible and rapid switching between colored and bleached state via incorporation of platinum catalysts on the surface of WO3 layer. However, when these devices were exposed to sunlight over 4 hour, it was confirmed that they did not return to fully bleached state in the darkened state due to their overcoloring process. In this study, we added 4-hydroxy-(2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPOL) as an additive to the electrolyte of photosensitive electrochromic device to effectively prevent the undesired overcoloring process. The resulting device with TEMPOL indeed did not undergo excessive coloration and showed great reversibility even after being exposed to sunlight for over 4 hours. Various concentrations of TEMPOL were applied to compare changes in the visible transmittance and coloring/bleaching kinetics of devices. In terms of energetic point of view, we proposed a plausible mechanism of TEMPOL to prevent excessive coloration.
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KEYWORD
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Smart window, Fast bleaching, Pt catalyst, 4-hydroxy TEMPO (TEMPOL), Photochromic device
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