(Invited) Investigation on Coloring/Self-Bleaching Mechanism in Photochromic Device Using Raman Spectroscopy

Abstract

Smart windows have been of great interest for a wide variety of energy saving application to control the penetration of solar energy into buildings by switching between a coloring and bleaching states. For dynamic transmittance control, various smart devices are developed, such as electrochromic (EC), photochromic (PC), and photoelectrochromic (PEC) devices. Although, the coloring/bleaching mechanisms of EC and PEC devices are well-known to achieve better smart window performance, it is still lacking information about coloration/decoloration mechanism in PC device. In this regards, unrevelling photochromic mechanism during coloring/self-bleaching could help to improve their performance to advance smart window application.In this talk, we investigate the coloring/self-bleaching mechanism using Raman spectroscopy. The Raman spectroscopy help to understand the photochromic mechanism upon light irradiation and self-bleaching stage. Our approach is based on the PC device, which is composed of the tungsten oxide (WO3) and titanium oxide (TiO2), and 5-methyl salicylic acid (5-MSA) as a cost effective ligand. The Raman spectroscopy allows us to understand the correlation between coloring/bleaching process and intercalation/deintercalation of Li ion. Figure 1