Near colorless all-solid-state switchable mirror based on magnesium-titanium thin film

Abstract

Magnesium-titanium (Mg–Ti) thin film was applied to all-solid-state switchable mirror by magnetron sputtering. Mg–Ti thin film works as an anodic electrochromic material of optical switching layer of the device. For clear transparency and durability of the device, a composition of Mg–Ti thin film was optimized. Though a maximum transmittance at transparent state of the device decreased with increasing titanium content in the film, the device showed fast recovery speed to reflective state. The transmittance at a wavelength of 670nm of the device with Mg0.88Ti0.12 was reached from 0.1% (reflective state) to 36% (transparent state) within 15s by applying voltage. The reflectance was also reduced from 57% to 20% within 10s. The transparent state of the device with Mg0.88Ti0.12 thin film showed almost colorless state with a chromaticity coordinates of x=0.335 and y=0.336. In the viewpoint of transmittance and durability, the authors found that the device with Mg0.88Ti0.12 thin film was the most suitable for practical application.