OLED: An Efficient Solid-State Lighting Technology

ORGANIC LIGHT EMITTING DIODE

OLED: The LC material is inherently a transparent
material, but it has a property where its optical
OLED’s are simple solid-state devices
axis can be rotated by applying an electric field
(more of an LED) comprised of very thin films of
across the material.
organic compounds in the electro-luminescent
layer. These organic compounds have a special
property of creating light when electricity is
applied to it. The organic compounds are
designed to be in between two electrodes. Out of

FIGURE 2: WORKING OF LCD

When the LC material optical axis is made
to align with the two polarizers’ axis, light will
pass through the second polarizer. On the other
hand, if the optical axis is rotated 90 degrees,
light will be polarized by the first polarizer,
rotated by the LC material and blocked by the
these one of the electrodes should be transparent. second polarizer.
FIGURE 1: OLED LIMITATIONS OF LCD:
They have been developed for applications in flat The polarizers and the LC material absorb
panel displays that provide visual imagery which light. On a typical monochrome LCD display the
is easy to read, vibrant in colors and less polarizers alone absorb 50% of the incident light.
consuming of power. On an active matrix displayTFT layer, the light
throughput may be as low as 5% of the incident
LCD:
light. Such low light output efficiency requires
LCD is a non-emissive display device. This with a LC based displays to have a powerful
means that they do not emit light on their own. backside or ambient light illumination to achieve
Thus, an LCD operates on the basis of either sufficient brightness. This causes LCD’s to be
passing or blocking light that is produced by an bulky and power hungry.The LC cells are in front
external light Source. Applying an electric field are relatively thin and their operation relatively
across an LCD cell controls its transparency or power efficient. It is the backside light that takes
reflectivity. A cell blocking (absorbing) light will up most space as well as power. In fact with the
thus be seen as black and a cell passing advent of low power microprocessors, the LCD
(reflecting) light will be seen as white. For a color module is the primary cause of short battery life
displays, there are color filters added in front of in notebook computers.
each of the cells and a single pixel is represented
by three cells, each responsible for the basic Moreover, the optical properties of the LC
colors: red, green and blue. material and the polarizer also causes what is
The basic physical structure of a LCD known as the viewing angle effect. The effect is
cell is shown in figure2.The liquid crystal (LC) such that when a user is not directly in front of
material is sandwiched between two polarizers the display, the image can disappear or sometime
and two glass plates (or between one glass plate seem to invert (dark images become light and
light images become dark).
and one Thin Film Transistor (TFT) layers).The
polarizers are integral to the working of the cell.
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EVOLUTION OF OLED: For an Organic LED, organic layer
corresponding to the p-type material is called the
The discovery of the electroluminescence
hole-transport layer (HTL) and similarly the layer
property in organic materials in 1950s is
corresponding to the n-type material is called the
considered to be the stepping stone of OLED.
electron-transport layer (ETL). In Figure 3, Alq3
is the ETL and TPD is the HTL.
Later in 1960, a scientist called Martin
Pope discovered an ohmic, dark injecting Similar to doped silicon, when ETL and
electrode contact to organic nature of crystals. HTL materials are placed to create a junction, the
With this he was also able to explain the work energy bands equilibrates to maintain continuity
functions for both the holes and electrons while across the structure. When a potential difference
injecting electrode contacts. These dark injecting is applied across the structure, a drift current
holes and electrons formed to be the base for an flows through the structure. The injected carries
OLED device. The technique was further recombination at the junction consists of both
experimented with DC electroluminescence under thermal and optical recombination, which emits
different conditions. Later it was found that photons.
electroluminescent materials can also act as
doped insulators. Thus came the discovery of a
double injection induced OLED device.

The first proper OLED was manufactured in 1980
by Dr.Ching W Tang and Steven Van Slyke. The
OLED had a double layer structure. When the
holes and electrons were transported separately
and when combined together produced a light in FIGURE 4:
the organic layer centre. This light was produced OPTICAL RECOMBINATION IN OLED
at a very low operating voltage with high
Figure 4 shows optical recombination from the
efficiency.
energy band perspective. Note that LUMO is a
Now more research is being done with the
short form for Lowest Unoccupied Molecular
application of OLED on polymer so as to obtain a
Orbital, which corresponds to the conduction
higher efficiency OLED.
band in the energy diagram of doped silicon, and
ORGANIC LED STRUCTURE:
HOMO is a short form for Highest Occupied
The p-n junction of oled is made from an organic Molecular Orbital, which corresponds to the
compound such as: Alq3 (Aluminum tris (8- valence band in the energy diagram of doped
hydroxyquinoline)) and diamine (TPD). The silicon.
molecular structure of some typical organic
Since an OLED emits light through a
materials used are shown.
recombination process, it does not suffer from the
viewing angle limitation like an LC based device.
Note that for any device to become a viable
candidate for use in flat panel displays it has to be
able to demonstrate high brightness, good power
efficiency, good color saturation and sufficient
lifetime. Reasonable lower limits specifications
for any candidate device should include the
following: brightness of ~ 100cd/m 2operating
FIGURE 3: MOLECULAR STRUCTURE OF
voltage of 5-15V.
ORGANIC MATERIALS

2


COMPONENTS IN AN OLED: The substrate is used to support the
OLED. The anode is used to inject more holes
The components in an OLED differ according to
when there is a path of current. The conducting
the number of layers of the organic material.
layer is used to carry the holes from the anode.
There is a basic single layer OLED, two layer and
also three layer OLED’s. As the number of layers The cathode is used to produce electrons when
increase the efficiency of the device also current flows through its path. The emissive layer
increases. The increase in layers also helps in is the section where the light is produced. This
injecting charges at the electrodes and thus helps layer is used to carry the electrons form the
in blocking a charge from being dumped after cathode.
reaching the opposite electrode.
Any type of OLED consists of the following WORKING OF OLED:
components.Emissive layer, Conducting layer, Before going on to the detailed
Substrate, Anode and Cathode terminals. explanation of its working, it is important to
know how the emissive layers and conducting
layers are added to the substrate. There are
mainly three basic methods for this operation.
They are:-

Inkjet Printing Technique – This is the cheapest
and most commonly used technique. The method
is same as the paper printing mechanism where
the organic layers are sprayed onto the substrates.
FIGURE 5: COMPONENTS OF OLED This method is also highly efficient and they can
As the emissive layer and the conducting layer is be used for printing very large displays like
made up of organic molecules (both being billboards and also big TV screens.
different), OLED is considered to be an organic
semi-conductor, and hence its name. The organic Organic Vapour Phase Deposition (OVPD) – This
molecules have the property of conducting is also an efficient technique which can be carried
electricity and their conducting levels can be out at a low cost. A cooled substrate is being hit
varied form that of an insulator to a conductor. by the organic molecules, which was evaporated
in a low pressure, high temperature chamber. The
The emissive layer used in an OLED is made up
of organic plastic molecules, out of which the gas is carried onto the substrate with the help of a
most commonly used is polyfluorene. The carrier gas.
conducting layer is also an organic molecule, and
the commonly used component is polyaniline.The Vacuum Thermal Evaporation (VTE)-This
substrate most commonly used may be a plastic, method is also commonly known as vacuum
foil or even glass.The anode component should deposition method. This operation is carried out
be transparent. Usually indium tin oxide is used. by gently heating the organic molecules so that
This material is transparent to visible light. It also they evaporate and subside on the substrates. As
has a great work function which helps in injecting the heating method is complicated and the
holes into the different layers. The cathode strictness of parameters should be highly
component depends on the type of OLED accurate, this method is economical as well.
required. Even a transparent cathode can be used. After the organic material has been applied to the
Usually metals like calcium and aluminium used
substrate the real working of the OLED begins.
because they have lesser work functions than
OLEDs emit light in a similar manner to LEDs,
anodes which helps in injecting electrons into the
through a process called electrophosphorescence
different layers.

3


The battery or power supply of the device
containing the OLED applies a voltage across the
OLED.

1. Cathode (−), 2. Emissive Layer, 3. Emission FIGURE 7: VARIATION OF I-V
of radiation, 4. Conductive Layer, 5. Anode (+) CHARACTERISTIC WITH TEMPERATURE
FIGURE 6: WORKING OF OLED Besides temperature, the I-V characteristic
Electrical current flows from the cathode also depends strongly on the type of
to the anode through the organic layers (an anode/cathode used in the device as well as the
electrical current is a flow of electrons). The thickness of the organic active Electro
cathode gives electrons to the emissive layer of Luminescence (EL) layer. The particular Figure
organic molecules.The anode removes electrons shows the I-V characteristic variation with the
from the conductive layer of organic molecules. thickness of the organic layer.
(This is the equivalent to giving electron holes to
the conductive layer). At the boundary between
the emissive and the conductive layers, electrons
find electron holes. When an electron finds an
electron hole, the electron fills the hole (it falls
into an energy level of the atom that is missing an
electron). When this happens, the electron gives
up energy in the form of a photon of light. The
OLED emits light. FIGURE 8: VARIATION OF I-V
The color of the light depends on the type CHARACTERISTIC WITH THICKNESS
of organic molecule in the emissive layer.
Manufacturers place several types of organic MODERN TECHNOLOGIES IN OLED’S
films on the same OLED to make color displays. (1)High Efficiency Materials:
The intensity or brightness of the light depends These materials emit light through
on the amount of electrical current applied. The the process of electrophosphorescence. In
more the current, the brighter the light. traditional OLEDs, the light emission is based
I-V CHARACTERISTIC VARIATION: on fluorescence, a transition from a singlet
The I-V characteristics of OLED is also excited state of a material. According to
varying with time. Several factors contribute to theoretical and experimental estimation, the
the I-V characteristic variation. The first and upper limit of efficiency of an OLED doped
foremost is temperature. The I-V characteristic with fluorescent material, is approximately
depends quite strongly on the operating 25%.
temperature. The I-V characteristic variation pose With our electro phosphorescent
a challenge to the control of OLED based materials used as a dopant, which exploits both
displays as the I-V operating points have to be singlet and triplet excited states, this upper
shifted depending on the operating temperature as limit is virtually eliminated. We are equipped
shown in figure 7. with the potential of 100% efficiency.

4


We are working towards the In an active matrix OLED display
commercialization of electro phosphorescent (AMOLED), information is sent to the transistor
devices by optimizing the device efficiency, in each pixel, telling it how bright the pixel
color purity and device storage and operation should shine. The TFT then stores this
durabilities. information and continuously controls the
current flowing through the OLED. In this way
the OLED is operating all the time, avoiding the
need for the very high currents necessary in a
passive matrix display.
The new high efficiency material systems
are ideally suited for use in active matrix OLED
displays, and their high efficiencies should result
in greatly reduced power consumption.

This type of OLED is suitable for high
resolution and large size display. Though the
manufacturing process is the same, the anode
FIGURE 9: TRIPLET EMITTER layers have a Thin-film transistor (TFT) plane in
Such a process is facilitated by the parallel to it so as to form a matrix. This helps in
development and modification of charge switching each pixel to it’s on or off state as
transport materials, charge blocking materials desired, thus forming an image. This is the least
and luminescent materials, and their power consuming type among others and also has
incorporation into devices. In addition to the quicker refresh rates which makes them suitable
fabrication of high quality devices, UDC is also for video as well.
committed to a high standard of device testing.
(3)Passive Matrix OLED (PMOLED):
Our scientists and engineers have custom
developed sophisticated test hardware and Passive Matrix displays consist of an
software for this purpose. array of picture elements, or pixels, deposited on
(2)Active Matrix OLED (AMOLED): a patterned substrate in a matrix of rows and
columns.
In an active matrix display, the array
is still divided into a series of row and column
lines, with each pixel formed at the intersection
of a row and column line. However, each pixel
now consists of an organic light emitting diode
(OLED) in series with a thin film transistor
(TFT). The TFT is a switch that can control the
amount of current flowing through the OLED.

FIGURE 11: PMOLED
In an OLED display, each pixel is an
organic light emitting diode, formed at the
intersection of each column and row line. The
first OLED displays, like the first LCD, are
addressed as a passive matrix. This means that to
illuminate any particular pixel, electrical signals
FIGURE 10: AMOLED are applied to the row line and column line (the
intersection of which defines the pixel).
5


The more current pumped through each FOLEDs are organic light emitting devices
pixel diode, the brighter the pixel looks to our built on flexible substrates. Flat panel displays
eyes.The design of this type of OLED makes have traditionally been fabricated on glass
them more suitable for small screen devices like substrates because of structural and/or processing
cell phones, MP3 players and so on. Though this constraints. Flexible materials have significant
type is less power consuming than an LCD and performance advantages over traditional glass
LED (even if connected to other external substrates.
circuitry’s), it is the most power consuming
FOLEDs Offer Revolutionary Features for
comparative to other OLED’s.
Displays:
This type is very easy to make as strips of (i)Flexibility: For the first time, FOLEDs may
anode and cathode are kept perpendicular to each be made on a wide variety of substrates that
other. When they are both intersected light is range from optically-clear plastic films to
produced. As there are strips of anode and reflective metal foils. These materials provide
cathode, current is applied to the selected strips the ability to conform, bend or roll a display
and is applied to them. This helps in determining into any shape. This means that a FOLED
the on or off pixels. display may be laminated onto a helmet face
shield, a military uniform shirtsleeve, an
(4)Inverted OLED:
aircraft cockpit instrument panel or an
automotive windshield.

(ii)Ultra-lightweight, thin form: The use of thin
plastic substrates will also significantly reduce
the weight of flat panel displays in cell phones,
portable computers and, especially, large-area
televisions-on-the-wall. For example, the
weight of a display in a laptop may be
significantly reduced by using FOLED
FIGURE 12: INVERTED OLED technology.

This type uses a bottom cathode, which is
(iii)Durability: FOLEDs will also generally be
connected to the drain end of an n-channel TFT
less breakable, more impact resistant and more
backplane. This method is usually used for
durable compared to their glass-based
producing low cost OLED with little applications.
counterpart.
(5)Foldable OLED (FOLED): (iv)Cost-effective processing: OLEDs are
projected to have full-production level cost
advantage over most flat panel displays. With
the advent of FOLED technology, the prospect
of roll-to-roll processing is created. To this end,
our research partners have demonstrated a
continuous organic vapor phase deposition
(OVPD) process for large-area roll-to-roll
OLED processing. While continuous web
FOLED processing requires further
development, this process may provide the
FIGURE 13: FOLDABLE OLED basis for very low-cost, mass production.

6


This type is mainly used in devices which
have more chance of breaking. As this material is
strong it reduces breakage and therefore is used in
cell phones, computer chips, GPS devices and
PDA’s. They are also flexible, durable and
lightweight. As its name explains, these OLED’s
are foldable and can also be connected to clothes.
They use different types of substrates like flexible
metallic foils, plastics and so on.

(6)Top Emitting OLED:
This type of OLED is integrated with a
transistor backplane that is not transparent. Such
devices are suitable for matrix applications like FIGURE 15: TRANSPARENT OLED
smart cards. The substrate used for this device is
This device has a good contrast even in
of the opaque/reflective type. As a transparent
bright sunlight so it is applicable in head-up
substrate is used the electrode used is either semi-
displays, mobile phones, smart windows and so
transparent or fully transparent. Otherwise the
on. In this device, the entire anode, cathode and
light will not pass through the transparent
the substrate are transparent. When they are in the
substrate.
off position, they become almost completely
transparent as their substrate. This type of OLED
can be included in both the active and passive
matrix categories. As they have transparent
parameters on both the sides, they can create
displays that are top as well as bottom emitting.

(8)White OLED:
White OLEDs emit white light that is
brighter, more uniform and more energy efficient
than that emitted by fluorescent lights. White
FIGURE 14: TOP EMITTING OLED OLEDs also have the true-color qualities
(7)Transparent OLED: of incandescent lighting. Because OLEDs can be
made in large sheets, they can replace fluorescent
The Transparent OLED (TOLED) uses a lights that are currently used in homes and
proprietary transparent contact to create displays buildings. Their use could potentially reduce
that can be made to be top-only emitting, bottom- energy costs for lighting.
only emitting, or both top and bottom emitting
(transparent). TOLEDs can greatly improve
contrast, making it much easier to view displays
in bright sunlight. Because TOLEDs are 70%
transparent when turned off, they may be
integrated into car windshields, architectural
windows, and eyewear. Their transparency
enables TOLEDs to be used with metal, foils,
silicon wafers and other opaque substrates for FIGURE 16: WHITE OLED
top-emitting devices.

7


This device creates the brightest light of all. This device uses the composite colours as
They are manufactured in large sheets. Thus they sub pixels and also on top of each other. This
can easily replace fluorescent lamps. They are causes the reduction in pixel gap and also an
also cost-effective and also consumes less power. increase in colour depth. Thus they are being
(9)Stacked OLED (SOLED): introduced as television displays.

The Stacked OLED (SOLED) uses (10)ORGANIC LASERS:
Universal Display Corporation's award-
An organic laser is a solid-state
winning, novel pixel architecture that is based
device based on organic materials and
on stacking the red, green, and blue subpixels
structures similar to those used in UDC's
on top of one another instead of next to one
display technologies. An optically-pumped
another as is commonly done in CRTs and
organic laser demonstrates five key laser
LCDs. This improves display resolution up to
characteristics: spatial coherence, a clear
three-fold and enhances full-color quality.
threshold, strongly polarized light emission,
SOLEDs may provide the high resolution
spectral line narrowing, and the existence of
needed for wireless worldwide-web
laser cavity modes. To realize commercial
applications.
potential, the key technical challenge today is
to demonstrate a mechanism for the electrical
pumping of these lasers.
The use of small-molecule organic
materials opens the door to an entirely new
class of light emitters for diode lasers. These
organic lasers may offer:
a) Greater color variety
b) Tunability
c) Further miniaturization
FIGURE 17: STACKED OLED
d) Easier processing
SOLED DISPLAY:
e) Lower cost in a host of end uses
A SOLED display consists of an
ORGANIC VAPOUR PHASE DEPOSITION:
array of vertically-stacked TOLED sub-pixels.
To separately tune color and brightness, each The OVPD production process
of the red, green and blue (R-G-B) sub-pixel utilizes a carrier gas stream in a hot walled
elements is individually controlled. By reactor at very low pressure to precisely deposit
adjusting the ratio of currents in the three the thin layers of organic materials used in
elements, color is tuned. By varying the total OLED displays. Conventional OLED
current through the stack, brightness is varied. fabrication equipment evaporates the organic
By modulating the pulse width, gray scale is molecules at high temperature and pressure.
achieved. With this SOLED architecture, each OVPD offers the ability to precisely control the
pixel can, in principle, provide full color. multi-source deposition required for full-color
Universal Display Corporation's SOLED OLED displays. The OVPD design should also
technology may be the first demonstration of be adaptable to the rapid, uniform deposition of
an vertically-integrated structure where organics on large-area substrates and for roll-
intensity, color and gray scale can be to-roll processing. The technology, Organic
independently tuned to achieve high-resolution Vapour Phase Deposition can enable low cost,
full-color. precise, high throughput process for fabricating
OLEDs.

8


ADVANTAGES OF OLED: 7.Efficient in Energy: OLED displays consumes
less energy as compared to LCD displays and
The different manufacturing process of other display screens. No backlight is required in
OLEDs lends itself to several advantages over these screens which is the biggest OLED
flat-panel displays made with LCD technology. advantage for use in portable gadgets.

1. Lower cost in the future: OLEDs can be 8.Good for Eyes: Another great advantage of
printed onto any suitable substrate by an inkjet OLED is that it pts less stains on eyes and hence
printer or even by screen printing,[52] theoretically are eye soothening. These screens provide better
making them cheaper to produce than LCD or viewing experience because they have better
plasma displays. However, fabrication of the contrast, brightness and color aspects.
OLED substrate is more costly than that of a TFT
LCD, until mass production methods lower cost 9.Self luminous: The OLED is self luminous i.e.
through scalability. it creates the required light energy on its own. It
does not require any external source for creating
2. Light weight & flexible plastic substrates: light like LCD.
OLED displays can be fabricated on flexible
plastic substrates leading to the possibility of 10.Environmental drawbacks: There are no
Organic light-emitting diode roll-up display being environmental drawbacks while using OLED as it
fabricated or other new applications such as roll- uses organic materials.
up displays embedded in fabrics or clothing. As
the substrate used can be flexible such as PET, 11.Power in-take: OLED does not require any
the displays may be produced inexpensively. power in take when turned off.

3. Wider viewing angles & improved 12.Durability: Another great advantage of OLED
brightness: OLEDs can enable a greater artificial is that it is more durable than traditional screens.
contrast ratio (both dynamic range and static, There chance of getting broken is comparitively
measured in purely dark conditions) and viewing less to LCD screens and other displays.
angle compared to LCDs because OLED pixels
directly emit light. OLED pixel colours appear DISADVANTAGES OF OLED:
correct and unshifted, even as the viewing angle
approaches 90 degrees from normal. 1.Lifespan: The biggest technical problem for
OLEDs was the limited lifetime of the organic
4. Better power efficiency: LCDs filter the light materials. In particular, blue OLEDs historically
emitted from a backlight, allowing a small have had a lifetime of around 14,000 hours to half
fraction of light through so they cannot show true original brightness (five years at 8 hours a day)
black, while an inactive OLED element does not when used for flat-panel displays. This is lower
produce light or consume power. than the typical lifetime of LCD, LED or PDP
technology—each currently rated for about
5. Response time: OLEDs can also have a faster 25,000 - 40,000 hours to half brightness,
response time than standard LCD screens. depending on manufacturer and model.
Whereas LCD displays are capable of a 1 ms
response time or less offering a frame rate of 2.Color balance issues: Additionally, as the
1,000 Hz or higher, an OLED can theoretically OLED material used to produce blue light
degrades significantly more rapidly than the
have less than 0.01 ms response time enabling materials that produce other colors, blue light
100,000 Hz refresh rates. output will decrease relative to the other colors of
light. This differential color output change will
6.Slimmer: The biggest adavantage of OLED change the color balance of the display and is
screen is that it is slimmer than LCD display. much more noticeable than a decrease in overall
While LCD and Plasma displays could be few luminance. This can be partially avoided by
inches thick, OLED advantage is that it is only adjusting colour balance but this may require
few millimeters thick. advanced control circuits.

9


3.Efficiency of blue OLEDs: Improvements to
the efficiency and lifetime of blue OLEDs is vital
to the success of OLEDs as replacements for
LCD technology. Considerable research has been
invested in developing blue OLEDs with high
external quantum efficiency as well as a deeper
blue color.

4.Water damage: Water can damage the organic
materials of the displays. Therefore, improved
sealing processes are important for practical
FIGURE 18: MOBILE WITH OLED
manufacturing. Water damage may especially
DISPLAY
limit the longevity of more flexible displays.
16) Smart goggles/helmets for scuba divers,
5.UV sensitivity: OLED displays can be motorcycle riders
damaged by prolonged exposure to UV light. 17) Medical test equipment
PRODUCT CONCEPTS 18) Wide area, full-motion video camcorders
Universal Display Corporation has only 19) Global positioning systems (GPS)
begun to imagine what our OLED technology 20) Integrated computer displaying eyewear
can create in the way of products for our world 21) Rugged military portable communication
and our future. The technology has the potential devices
to not only improve existing products, but also ORGANIC FUTURE
to create exciting, new product possibilities, for The first products using organic displays
example: are already being introduced into the market
1) Low-power, bright, colorful cell phones place. And while it is always difficult to predict
2) Full color, high-resolution, personal when and what future products will be
communicators introduced, many manufacturers are now
3) Wrist-mounted, featherweight, rugged PDAs working to introduce cell phones and personal
4) Wearable, form-fitting, electronic displays digital assistants with OLED displays within the
5) Full-color, high resolution, portable Internet next one or two years. The ultimate goal of
devices and palm size computers using high-efficiency, phosphorescence, flexible
6) High-contrast automotive instrument and OLED displays in lap top computers and even
windshield displays for home video applications may be no more
7) Heads-up instrumentation for aircraft and than a few years into future.
automobiles
8) Automobile light systems without bulbs
9) Flexible, lightweight, thin, durable, and
highly efficient laptop screens
10) Roll-up, electronic, daily-refreshable
newspaper
11) Ultra-lightweight, wall-size television
monitor
12) Office windows, walls and partitions that FIGURE 19: IDENTITY CARD WITH OLED
double as computer screens DISPLAY
13) Color-changing lighting panels and light However, there remains much to be done
walls for home and office if organics are to establish a foothold in the
14) Low-cost organic lasers display market. Achieving higher efficiencies,
15) Computer-controlled, electronic shelf pricing lower operating voltages, and lower device life
for supermarkets and retail stores times are all challenges still to be met.
10


Given the aggressive worldwide efforts REFERENCES:
in this area, emissive organic thin films have an 1. "Brief OLED history". Comboled Project
excellent chance of becoming the technology of 2. "Organic electroluminescent diodes".
choice for the next generation of high-
Applied Physics Letters
resolution, high-efficiency flat panel displays.
3. Electronic processes in organic crystals
and polymers, 2nd ed., by M. Pope
4. Wikipedia.com

FIGURE 20: OLED DISPLAY
In addition to displays, there are many
other opportunities for application of organic
thin-film semiconductors, but to date these have
remained largely untapped. Recent results in
organic electronic technology that may soon find
commercial outlets in display black planes and
other low-cost electronics.

FIGURE 21: WATCH WITH OLED DISPLAY

CONCLUSION:
OLEDs offer many advantages over both
LEDs and LCDs. They are thinner, lighter and
more flexible than the crystalline layers in an
LED or LCD. They have large fields of view as
they produce their own light.
Research and development in the field of
OLEDs is proceeding rapidly and may lead to
future applications in heads up displays,
automotive dash boards, billboard type displays
etc. Because OLEDs refresh faster than LCDs, a
device with OLED display could change
information almost in real time. Video images
could be much more realistic and constantly
updated.

11

OLED: An Efficient Solid-State Lighting Technology

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