Yonsei, Korea Univ. teams develop foldable transistors for smart devices

By Kim Bo-eun

Yonsei University Professor Cho Jeong-ho, left, and Korea University Professor Woo Han-young / Courtesy of Yonsei University

Teams at Yonsei University and Korea University have co-developed foldable transistors for flexible smart devices, the schools said Thursday. The two teams, led by Yonsei University Professor of Chemical and Biomolecular Engineering Cho Jeong-ho and Korea University Professor of Chemistry Woo Han-young, respectively, published an article together about their latest development in the journal, Science Advances.

The article introduces the completely foldable, polymer thin-film transistors. The authors state that the electrical performance of the transistors is maintained without noticeable degradation even after extreme folding. The article suggests that the proposed fabrication strategy can further be applied to various semiconducting polymers for foldable electronics.

There have been advances in stretchable or deformable electronics ― from rudimentary flexible devices to bendable, rollable and foldable devices ― in recent decades with growth in the demand for enhanced device portability and usability.

The development of electrical components that can withstand extreme environments has become a critical task, given that foldable electronics are required to have exceptionally high mechanical stability. Conventional metallic electrodes, such as copper, aluminum, silver and gold electrodes, exhibit excellent electrical conductivity, but their rigidity and brittleness hampers their application to foldable electronics. Conducting polymers have been proposed and widely used as alternatives to conventional metallic electrodes, because of their mechanical robustness.

Conducting polymers are an excellent platform for foldable electronics, but achieving the mechanical stability of the structure of an electronic device has remained a challenging task. The adhesion at the interfaces between the component layers of an electronic device is affected by the repeated folding and unfolding of the device.

An electronic device's component layers include an electrode, a semiconductor and an insulator. The electrode and semiconductor interfaces are critical because charge transport occurs across these layers. Therefore, it is crucial to improve the mechanical stability of the electrode and semiconductor interface under physical states of flexion. Existing studies had been unable to achieve any enhancement of this mechanical stability.

"This study presents technology for manufacturing semiconductor polymers for flexible smart devices that are not only flexible but completely foldable," Cho was cited as saying in a press release.

The study was supported through various research funds at the National Research Foundation of Korea and Yonsei University.