The University of Tokyo has successfully developed high-speed and low-power organic transistor printing technology to help future low-cost, lightweight wearable display technology

On October 12, it is understood that the University of Tokyo in Japan used a special U-shaped metal film pattern to develop a method of printing organic semiconductor thin films on a special surface with high solution repellency, promoting the development of organic thin film transistor liquid crystal screens. development to help realize low-cost, large-area, lightweight and wearable electronics in the future. The research results were published in Science Advances.

For 10 years, smartphone and computer screens have been based on Display technology consisting of thin-film transistors. These are inorganic transistors that require very little power and have well-proven capabilities due to their widespread adoption, but have limitations.

Optical microscope image of an organic thin-film transistor etched in gold Source: ©2020 Kitahara Same below

The idea of ​​organic thin-film transistors is not new, but so far, industry and academia have not figured out whether it is possible to print such a device, thereby enabling a revolution in design. Tatsuo Hasegawa, Kitahara and their team from the Department of Applied Physics have figured out how to print thin films of organic semiconductors on a special surface that is highly solution repellant, or “freeze-dried”. This means that normally, the surface repels the material needed to print transistor structures, which seems counterintuitive. But the hydrophobic surface is responsible for creating the transistor structure, and fine-tuning it can achieve high performance.

Gyo Kitahara, a doctoral student in the Department of Applied Physics at the University of Tokyo, said, “We explore new ways to improve thin-film transistors, such as new designs or new manufacturing methods. For example, organic thin-film transistors have a bright future in liquid crystal display devices. Compared to inorganic classes, we expect organic classes to play a role in low-cost, large-area, lightweight, and wearable electronics, especially through the use of printing-based production techniques.”

Time series of microscope images showing stages of printing microstructures

To overcome repulsion, Kitahara said, “We took advantage of a fluid property, which you probably see every time you wash your hands with soap, that soap bubbles hold their shape by reducing the surface tension of the liquid. We speculate that despite the repulsive force, But the soap film mechanism should be effective for forming thin liquid layers on hydrophobic surfaces. By forming thin liquid layers during printing, solid semiconductor thin films can be formed and grown.”

“After trial and error, we finally found that using a special U-shaped metal film pattern seemed to work well for uniform growth of the film due to its ability to form a thin liquid layer on the freeze-dried surface,” Kitahara said.

With this innovation, other researchers can continue to expand the size of this approach, building on the team’s findings. With the proliferation of large, flexible or wearable devices, the Hasegawa team dreams of seeing the real and virtual worlds merge in ways we’ve never seen before.