Developed a Display That Remains Intact Even After Soaking and Crumpling in Water

KAIST-Nano Comprehensive Technology Institute Research Team
"Maintains 80% Luminance Even After 6 Hours in Water"

A display material that maintains performance even when soaked in water has been developed.

Cover of the international academic journal ACS Nano dated the 13th. A paper on flexible material OLEDs jointly developed by KAIST and the Institute for Nano Comprehensive Technology was published. Photo by KAIST

On the 31st, the Korea Advanced Institute of Science and Technology (KAIST) announced that a research team led by Professor Kyungcheol Choi from the Department of Electrical Engineering and Electronics, in collaboration with Dr. Lee Yonghee's team from the Nano Convergence Technology Institute, succeeded in developing a waterproof transparent flexible organic light-emitting diode (OLED) that emits light while showing the background even when exposed to water by utilizing MXene nanotechnology.

Transparent flexible displays, which are attracting much attention in various fields such as automotive displays, bio-healthcare, military, and fashion, are prone to breaking easily even with slight deformation. To address this, extensive research has been conducted on many transparent flexible conductive materials such as carbon nanotubes, graphene, silver nanowires, and conductive polymers.

Two-dimensional MXene materials are conductive materials with attractive properties such as high electrical conductivity, transparency, and large-scale productivity through solution processing. However, their electrical properties easily degrade due to moisture in the atmosphere or water, limiting their use in high-durability electronic devices. Consequently, systemization into matrix forms capable of information display had not been achieved.

The research team developed an environmentally robust, high-durability MXene-based OLED by employing an encapsulation strategy to prevent oxidation caused by moisture or oxygen. After analyzing the degradation mechanism of MXene’s electrical properties due to moisture, they designed an encapsulation thin film. By blocking moisture and introducing residual stress compensation technology to provide flexibility, they ultimately designed a double-layer encapsulation thin film structure. To enable washing without degradation even underwater, a thin plastic film with a thickness of several tens of micrometers (μm) was attached to the topmost layer.

Through this, the team developed MXene-based OLEDs in red (R), green (G), and blue (B) that emit luminance above 1,000 cd/m2, bright enough to be recognized by the human eye even under outdoor display conditions exposed to sunlight. For the red MXene-based OLED, they secured a storage lifetime of 2,000 hours in the atmosphere (maintaining 70% luminance), an operating lifetime of 1,500 hours in the atmosphere (maintaining 60% luminance), and flexibility capable of withstanding over 1,000 cycles at a low curvature radius of about 1.5 mm. Additionally, the performance was maintained (80% luminance retention) even after being submerged in water for 6 hours. Furthermore, by utilizing patterning technology, they fabricated MXene-based OLEDs in a passive-matrix form, demonstrating a transparent display capable of showing letters or shapes.

So-Young Jung, a doctoral candidate in the research team, said, “We focused on designing an encapsulation structure and process suitable for improving the reliability of MXene OLEDs,” adding, “By fabricating MXene OLEDs in a matrix type and displaying simple characters or models, we laid the foundation for applying MXene in the field of transparent displays.”

The research results were published online on April 5 in the international nanotechnology journal ACS Nano (IF 18.0) and appeared as the front cover paper on the 13th.

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