Hiromi Hotta

Electrochromic switchable mirror glass with controllable reflectance

An electrochromic switchable mirror glass with controllable reflectance was developed. The conditions for fabricating InGaZnO4 (IGZO) thin film, which serves as a transparent conductor, were investigated. The mirror glass with IGZO thin film exhibited multiple colors arising from interference between multilayers. The mirror glass with IGZO thin film fabricated at a working pressure of 0.4 Pa showed high transmittance (63%) in the transparent state and low reflectance (16%) in the reflective state at a wavelength of 670 nm. Moreover, the developed mirror glass had low glare in the reflective state because the reflection of direct, bright light was reduced.

Electrochromic switchable mirror glass fabricated using adhesive electrolyte layer

We have developed a simple process for fabricating electrochromic switchable mirror glass using an adhesive electrolyte layer. The adhesive electrolyte layer was a mixture of polyethyleneimine electrolyte and polyvinyl butyral adhesive dissolved in gamma-butyrolactone. The device was formed from two substrates; the adhesive electrolyte layer was applied to one of the substrates before they were stuck together. The applied voltage required to change the state of the device was smaller than that of a conventional device with a solid electrolyte layer deposited by sputtering. Our method is simple, fast, and efficient and can be used to fabricate large devices.

Solution-Based Electrolyte Layer Suitable for Electrochromic Switchable Mirror

An electrochromic switchable mirror was fabricated using an electrolyte solution that does not contain water or acid. We chose a mixture of poly(ethylene imine) (as electrolyte) and tetrahydrofuran (as solvent) as an electrolyte solution and the solution was inserted between two substrates composed of functional materials. The state of the device was changeable using an applied voltage lower than that used in conventional devices, including a solid electrolyte thin film deposited by magnetron sputtering. Using this technique, large devices can also be easily fabricated. These switching characteristics are considered to be due to the proton-conductive properties of the electrolyte.

Degradation Analysis of Electrochromic Switchable Mirror Glass Based on Mg--Ni Thin Film at Constant Temperature and Relative Humidity

An electrochromic mirror glass that can be switched between reflective and transparent states by voltage application is presented. For the practical applications of such a device such as in energy-saving windows, optical devices, and electronic devices, the effects of environmental factors such as temperature and humidity on the optical switching properties of the device should be investigated in detail. In this work, the effects of constant temperature and relative humidity conditions on the device properties were studied. In particular, surface analysis studies were conducted. When these devices were kept at 40 °C and 60% relative humidity (RH), the speed of switching from the reflective state to the transparent state decreased with increasing time of storage in the bath. This reduced switching speed was related to the degradation of the surface metallic layers of the device, which could be observed by transmission electron microscopy (TEM) as an increase in surface roughness (Ra = 19.8 nm). Although the as-prepared device had a Mg4Ni optical switching layer approximately 40 nm in typical thickness, the degraded device exhibited an expanded layer of approximately 78 nm thickness. This increased thickness was associated with the change to the nonmetallic states of oxide and hydroxide from the metallic states of magnesium and nickel in the layer because of the adverse effects of the atmosphere.