Korean researchers have developed an organic light-emitting diode (OLED) panel that can be rolled up like a newspaper and remains highly efficient despite repeated bending, paving the way for the potential application of OLED to wearable monitors or body-worn sensors.

The joint research team led by Yoo Seung-hyup, a professor at the School of Electrical Engineering of KAIST, and Lee Tae-woo, a professor at Dept. of Materials Science and Engineering of POSTECH, announced on Thursday they developed a highly efficient, flexible OLED panel that endures repeated bending stresses using graphene, which is called the “dream material.”

Currently, flexible OLED technology is used in curved edges of a smartphone and TVs, but they are not truly flexible because their shape is fixed. Flexible OLEDs must be robust enough to meet the real-life demands of end-users and therefore scientists have looked for solutions to maintain OLED performance even after hundreds or thousands of times of folding and unfolding to make a monitor that could be attached to clothes or foldable into a pocket or bag.

The research team applied a stack structure consisting of multiple layers of titanium oxides, graphenes and conductive polymers to OLED in order to overcome limitations of light transmission. The resilient titanium oxide can endure a four times higher strain compared with existing transparent oxide electrodes.

They also succeeded in increasing the display brightness by maximizing resonance within OLED. Resonance is a phenomenon that shows a strong response to specific frequency windows and laser is a good example of resonance.

“If we use an appropriate level of resonance in OLED, it is possible to improve not only efficiency but also the color gamut,” said Professor Yoo.

By Won Ho-sup

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