Ultrathin quantum dot LED that can be folded freely as paper
The new device can be folded into complex 3D structures such as
butterflies, airplanes, and pyramids

Date:
September 27, 2021
Source:
Institute for Basic Science
Summary:
Scientists have unveiled an ultrathin quantum dot LED that can
be folded as freely as paper. The new device can be folded into
complex 3D structures such as butterflies, airplanes, and pyramids.



FULL STORY ========================================================================== Quantum dot light-emitting diode (QLED), which employs quantum dots
as a light- emitting material, has attracted significant attention
as a promising alternative for next-generation display technologies,
owing to its outstanding electroluminescence properties. Since it does
not require any bulky components such as backlight units, QLED displays
can potentially be manufactured into an ultrathin form factor. A joint
research team led by KIM Dae-Hyeong (Professor at Seoul National
University) and HYEON Taeghwan (Distinguished professor at Seoul
National University) from the Center for Nanoparticle Research within
the Institute for Basic Science has previously unveiled a prototype
QLED back in 2015. The device had a thickness of only 3 micrometers,
which is only one- thirtieth of that of human hair. Due to such an
extremely reduced thickness, the ultrathin QLED exhibited outstanding mechanical flexibility, which allowed it to be readily applicable in
various wearable devices, such as electronic tattoos.


========================================================================== Recently, the team further advanced this technology and developed
a foldable variant of the ultrathin QLED, inspired by the ancient
art of paper folding known as origami. The IBS researchers reported three-dimensional foldable QLEDs, which can be freely transformed into
various user-customized 3D structures, such as butterflies, airplanes,
and pyramids. Considering the rising popularity of foldable smartphones,
the advancement of foldable display technology is gaining greater
importance. It is expected this technology can provide unprecedented opportunities for next-generation electronics with user- customized
form factors with complex structures, as well as allowing for dynamic three-dimensional display of visual information.

The researchers endowed foldability to the conventional planar QLED
via a new fabrication process that can partially etch the epoxy
film deposited on the QLED surface without damaging the underlying
QLED. Using a power-controllable carbon dioxide pulsed laser and
the silver-aluminum alloy-based etch-stop layers, the etching depth
can be precisely controlled. As the laser-etched part of the device is relatively thinner than the surrounding region, it is possible to etch out deformation lines along which the device can be folded like origami paper.

Based on the selective laser-etching technique, researchers were
able to precisely control the radius of curvature down to less than
50 micrometers.

Under such a small curvature radius, the fold line resembles a sharp
edge with no visible curvature. By using mechanical simulation to
carefully engineer the device, researchers were able to minimize
the strain loaded on the light- emitting components. The entire QLED
including the crease region (a fold line) was able to maintain a stable light-emitting performance even when after it was repeatedly folded 500
times. The technology was applied to fabricate 3D foldable QLEDs with
various complex shapes such as butterflies, airplanes, and pyramids.

"We were able to build a 3D foldable QLED that can be freely folded
just like a paper artwork," said KIM Dae-Hyeong, the vice-director of
the Center for Nanoparticle Research. He also said, "By fabricating
the passively driven, 3D foldable QLED arrays composed of 64 individual
pixels, we have shown the possibility of developing displays with greater complexity in the future." HYEON Taeghwan, the director of the Center
for Nanoparticle Research, states that "Through the technology reported
in this research, paper-like QLEDs that can be folded into various complex structures have been successfully fabricated. Who knows when the day will
come when electronic paper with a display unit can replace real paper?" ========================================================================== Story Source: Materials provided by Institute_for_Basic_Science. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Dong Chan Kim, Huiwon Yun, Junhee Kim, Hyojin Seung, Won Seok Yu,
Ja Hoon
Koo, Jiwoong Yang, Ji Hoon Kim, Taeghwan Hyeon, Dae-Hyeong
Kim. Three- dimensional foldable quantum dot light-emitting
diodes. Nature Electronics, 2021; 4 (9): 671 DOI:
10.1038/s41928-021-00643-4 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/09/210927110513.htm

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