6
Knowledge Corner
Sep 2015
By Shoucheng Dong
(IAS Junior Fellow and Research Assistant Professor of Chemistry, HKUST)
ORGANIC LIGHT EMITTING DIODE (OLED):
THE
DISPLAY TECHNOLOGY
Imagine a large flat-screen TV that can be pasted onto a
wall like a piece of wallpaper. This was once a futuristic
concept but is fast becoming a practical reality. A flexible
55” OLED TV with a thickness that measures only 0.97
mm has recently been showcased in the market. This TV
is so thin and light that it can be mounted on any surface
with hardly any effort like sticking a strip of magnetic pad
on a refrigerator. OLED, which stands for organic light
emitting diode, was first invented by IAS Bank of East
Asia Professor Ching W. Tang some 30 years ago when
he was working at the Kodak Research Laboratories.
Today, OLED displays can be found in a wide range of
consumer products, including smartphones, tablets, TVs,
and trendier wearable electronics. Widely acclaimed
because of its many differentiating features, OLED is
gaining ground in the display industry with the potential
to be the next-generation display technology.
OLED is a semiconductor device capable of producing
light very efficiently. Unlike conventional LED, which is
based on inorganic semiconductors, OLED utilizes a
stack of thin organic films to transport charges (electrons
and holes) and produce light via electron-hole
recombination. The color of the light and the efficiency
of its production are primarily determined by localizing
the electron-hole recombination in the emitter layer,
which is one of the layers in the stack. This localization
can be largely effected by engineering suitable
“heterojunction” interfaces between the various layers.
By “doping” the emitting layer with highly luminescent
molecules, the light emission from OLED can be tuned
in wavelength and bandwidth throughout the visible
spectrum. Thus, it is relatively simple to produce highly
saturated RGB primary colors that are necessary for
display applications. In addition, OLED can be driven
OLED utilizes a stack of thin organic films to transport charges (electrons
and holes) and produce light via electron-hole recombination.
