An international joint research team has succeeded in developing a new technology to make a smart window that can automatically block light at night and becomes transparent in the morning by responding to light.
Dr. Ko Doo-hyun from the Korea Institute of Science and Technology announced on Oct. 22 that a joint research team composed of Korean and British researchers successfully developed a material that can automatically receive or block visible light based on the presence of ultraviolet light, and a smart window that combines this material and a solar cell.
The research team was able to make a new liquid crystal by combining a liquid crystal material with a helical structure and an azobenzene compound. Since the molecular structure of the azobenzene compound changes when exposed to light, the helical period of the liquid crystal can be controlled by light.
They attached each of two polarizing plates at the top and bottom of the liquid crystal. When it is dark, the helical period of liquid crystal molecules becomes very short. In contrast, when it is bright the period lengthens. When the helical period is short, the polarization state of the light that enters through the polarizing plate at the top does not change. Light is blocked by the polarizing plate at the bottom. When the helical period becomes long, the polarization state of the light does change. Light penetrates the polarizing plate at the bottom and reaches the inside.
The team was able to produce electricity using the penetrating light by linking a manufactured liquid crystal and a window-type solar cell. Visual light used in solar batteries was able to penetrate the window by controlling the helical period of the liquid crystal. Existing smart windows can receive and block sunlight, but an additional power supply is needed to operate equipment, or it must be operated manually.
Dr. Ko said, “We are planning to make efforts to commercialize the method by controlling the degree of transparency of smart windows. We are also going to produce smart windows in various colors.”
The research findings were first published online on Oct. 6 by Advanced Energy Materials, a monthly scientific journal published by Wiley-VCH.