Hokkaido University Research Profiles

Nanotechnology / Materials

Semiconductor Devices That Display and Store Information Through Changes in Color and Conductivity

Can windowpanes and mirrors serve as memory devices?

We have developed new information display and storage devices by incorporating electrochromic materials, which are attracting attention as “electronic curtains,” into thin-film transistors and using the color change of colorless transparent ? black and the conductivity changes of insulator ? metal. Information can be displayed and stored on window glass and mirrors.

Content of research

With the spread of IoT, the amount of information that needs to be collected and stored continues to increase as not only personal computers but also various devices are connected to the internet. Current information storage devices use only electrical resistance changes in semiconductors, but with this research, we have developed a device that can use color changes in addition to electrical resistance changes for information display and storage. A three-terminal all-solid-state thin-film transistor structure was produced on a glass or plastic substrate with source, drain, and gate electrodes consisting of a laminate of an amorphous WO3 thin film (100 nm thick)/nanoporous glass thin film (300 nm)/polycrystalline NiO thin film (50 nm) and a transparent ITO thin film (20 nm). When a positive voltage of a few volts is applied between the gate and the source, the WO3 thin film changes to a dark blue color and simultaneously becomes metal, and when a negative voltage is applied, it returns to a colorless transparent insulator.

  • By applying voltage between the gate and the source, colorless transparent insulator can be switched to dark blue metal and vice versa.

Potential for social implementation

  • ・We consider that window glass and mirrors can be IoT devices, such as electronic curtains that automatically lower their transmittance at night, window glass that acquires, displays, and stores information such as weather forecasts in the morning via the internet, and mirrors that display the temperature and UV index.

Appealing points to industry and local governments

Information such as text and pictures can be displayed and stored on mirrors and window glass. Since information display and storage devices can be manufactured at room temperature, these can be produced on heat-sensitive plastics. Since information display and storage devices can be enlarged, these can be manufactured at low cost. In addition, once the information has been entered, the standby power is zero, which saves energy.

Intellectual property related to this research

PCT/JP2016/050206 「スイッチング装置」
(日本:特許第6629241号 米国:特許第10032892号 欧州:16735045.3)
PCT/JP2019/046479 「エレクトロクロミックトランジスタ、電子カーテン、情報表示記憶装置および防眩ミラー」