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OLED stands for Organic Light Emitting Diode. It can be
called as ‘organic cousins’ of LEDs. As the name suggests,
the word “organic” signifies the presence of organic
emissive layer sandwiched between the cathode and the
Types of OLEDs:
1: Small Molecule OLED
2: Polymer OLED
Lighting applications that use LEDs and OLEDs, or
light emitting polymers are commonly referred to as
solid-state lighting (SSL). In OLED, whole solid
surface acts as the light source.
The basic OLED cell structure consists of a stack of
thin organic layers sandwiched between a
transparent anode and a metallic cathode, which are
in turn sandwiched between a glass top plate (seal)
and a glass bottom plate (substrate) . The organic
layers comprise a hole-injection layer, a hole-
transport layer, an emissive layer and an electron-
This can be understood by these figures:
When a voltage is applied to the electrodes the charges start
moving in the device under the influence of the electric field.
Electrons leave the cathode and holes move from the anode in
opposite direction. The recombination of this charges leads to the
creation of a photon with a frequency given by the energy gap (E =
hν) between the LUMO(Lowest unoccupied Molecular Orbital)
and HOMO(Highest Occupied Molecular Orbital) levels of the
Therefore, the electrical power applied to the electrodes is
transformed into light.
In short, when electric current is applied to the two conductors, a
bright, electro-luminescent light is produced directly from organic
Different materials and dopants can be used to generate different
colours and the combination of them allows building up a white
light source. Here is the Figure:
Like their LED counterparts, OLEDs produce light by the
recombination of electrons and holes. In the case of the OLED,
when a voltage is applied across the device, electrons are
injected at the cathode and provide electrons to the emissive
layer(s). The conductive layer provides electrons to the anode,
leaving “holes” within the layer. These holes migrate to the
emissive layer where they recombine with the excess electrons.
As the electrons drop into the holes, they release energy in the
form of light. The color of the light emitted depends on the
composition of the organic emissive layer. Multiple layers (for
example red, green and blue) can be combined in one device to
produce any desired color including white.
• The famous AMOLED (Active Matrix OLED) display
used in smart phones (mainly Samsung and HTC).
• PMOLED(Passive Matrix OLED) displays are used in
mp3 players or secondary displays on cell phones.
• Transparent Displays: Samsung unveiled their new
development in International Consumer Electronic
Show 2010, the Transparent OLED Laptop. This is the
world’s first largest transparent OLED prototype.
People took great interest in this development for its
unique and stylish transparent look. Here are some
pictures of this Laptop:
• Flexible Displays: Using OLEDs, it is also
possible to create Flexible Displays:
•Sony showed off a full-screen laptop (pictured
below), bendable e-reader, and Walkman bracelet
concepts, all based around flexible
OLED technology and built with "flexible
bioplastics," along with the flexible display that
going to power them all when they hit the
Organic LEDs aren't just limited to screens:
They're also used for general illumination since they're
energy efficient, more so than many of today's other light
sources. They can also illuminate large areas. One application
could entail using transparent sheets to turn windows into
lamps at night. Already, OLEDs are used for backlighting
small LCD screens.
OLEDs in Future Cars:
Smart Dashboard Displays;
Windshields transparent OLEDs;
Internal and External Lighting;
Back window alerts and messaging.
OLED can also be used to treat skin
cancer and acne. A UK team is
developing wearable OLED stickers
that will cure skin ailments on the go.
Many skin cancers are currently
treated by a combo of light and
drugs (called photodynamic therapy)
but current light sources are large
and the therapy requires lengthy
hospital visits. Lumicure Ltd. is
looking to use OLED in the treatment
instead. The OLEDs would be
attached to sticking plaster that can
be placed on the diseased skin. Not
only will it be comfortable, the patient
could possibly do the therapy from
home. Named: OLED bandage.
Being self-luminous, they require no backlighting. By
contrast, LCDs require either an external light source
(reflective type) or a fluorescent or LED backlight. No
backlighting means OLED displays are smaller in size, use
less power, weigh less and cost less.
In summary, OLED displays have:
High brightness and contrast
Ultra-wide viewing angle
No backlight required
Thin, compact form factor
Fast response time and higher refresh rate
Low power consumption
OLED displays can be made very thin, making them very
attractive for televisions and computer monitor applications.
Colour capability: It is possible to fabricate Flexible: It is
possible to make OLED displays flexible by using the right
materials and processes.
Very thin: OLED displays that can generate all colours.
Power consumption: The power consumed by an OLED
display is generally less than that of an LCD when including
the backlight required. This is only true for backgrounds that
are dark, or partially dark.
Bright images: OLED displays can provide a higher
contrast ratio than that obtainable with an LCD.
Wide viewing angle: With many displays, the colour
becomes distorted and the image less saturated as the
viewing angle increases. Colours displayed by OLEDs
appear correct, even up to viewing angles approaching 90°.
Fast response time: As LCDs depend upon charges being
held in the individual pixels, they can have a slow response time.
OLEDs are very much faster. A typical OLED can have a
response time of less than 0.01ms.
The First OLED TV. . .
Sony Bravia XEL-1 is the world’s first OLED TV that is only 3mm thick. It
features 960×540 resolution, 1,000,000:1 contrast ratio, 16:9 aspect ratio
and support for Dolby Digital. Sony’s unique Super Top Emission technology
intensifies brightness and efficiency.
What’s great about Sony Bravia XEL-1 is that it only consumes up to 40
percent less power than a conventional 20 inch LCD panels. Another great
feature includes the Screen Tilt Feature, it allows you to tilt it up to 70
degree to accommodate different viewing positions.
Sony XEL-1 OLED TV is priced at $2,499.99.
Moreover, OLEDs are also used in wrist watches, headsets,
remote controls, display of audio systems, digital photoframes
and many other kind of electronic devices.
Kodak was the first to release a digital camera LS633
with an OLED display in March,2003.
Moreover, the companies Huawei, LG, Sensics Natalia,
Lenovo, Olympus, Panasonic and many more have also
contributed towards it.
Water can easily damage an OLED screen. They are
highly moisture sensitive.
Cost of production is still high. An OLED screen costs
more than an LCD screen of similar size. This is more
an issue for large screen HDTVs than for portable devices
that have smaller screens.
In summary, OLED is the screen technology of the
future. As manufacturing processes improve and
production cost becomes cheaper more and more
LCD displays with be replaced with OLED displays.