South Korean researchers at the Department of Materials Science and Engineering at the Korea Advanced Institute of Science and Technology (KAIST) have developed ultrathin and transparent oxide thin-film transistors (TFT) for an active-matrix backplane of a flexible display by using the inorganic-based laser lift-off (ILLO) method.

Like Us on Facebook

The team led by Professors Keon Jae Lee and Sang-Hee Ko Park of KAIST previously demonstrated the ILLO technology for energy-harvesting and flexible memory devices.

They fabricated a high-performance oxide TFT array on top of a sacrificial laser-reactive substrate. After laser irradiation from the backside of the substrate, only the oxide TFT arrays were separated from the sacrificial substrate as a result of reaction between laser and laser-reactive layer, and then subsequently transferred onto ultrathin plastics (4μm thickness).

Finally, the transferred ultrathin-oxide driving circuit for the flexible display was attached conformally to the surface of human skin to demonstrate the possibility of the wearable application. The attached oxide TFTs showed high optical transparency of 83% and mobility of 40 cm^2 V^(-1) s^(-1) even under several cycles of severe bending tests.

"By using our ILLO process, the technological barriers for high performance transparent flexible displays have been overcome at a relatively low cost by removing expensive polyimide substrates," said Professor Lee.

"Moreover, the high-quality oxide semiconductor can be easily transferred onto skin-like or any flexible substrate for wearable application."

The advent of the Internet of Things (IoT) has seen strong demand for wearable and transparent displays that can be applied to various fields such as augmented reality (AR) and skin-like thin flexible devices.

Previous flexible transparent displays, however, have posed tough challenges difficult to overcome. Among these are poor transparency and low electrical performance.

To improve the transparency and performance, past research efforts have used inorganic-based electronics, but the fundamental thermal instabilities of plastic substrates have hampered the high temperature process, an essential step necessary for the fabrication of high performance electronic devices.

TagsKorea Advanced Institute of Science and Technology, KAIST, inorganic-based laser lift-off (ILLO) method, Keon Jae Lee, Sang-Hee Ko Park