1
OLED
ABSTRACT
Over the time there are many changes came into the field of output/display devices. In this field
first came the small led displays which can show only the numeric contents. Then came the
heavy jumbo CRTs (Cathode Ray Tubes) which are used till now. But the main problem with
CRT is they are very heavy & we couldn’t carry them from one place to another. The result of
this CRT is very nice & clear but they are very heavy & bulky & also required quiet large area
than anything else. Then came the very compact LCDs (Liquefied Crystal Displays). They are
very lighter in weight as well as easy to carry from one place to the other. But the main problem
with the LCDs is we can get the perfect result in the some particular direction. If we see from
any other direction it will not display the perfect display. To overcome this problems of CRTs &
LCDs the scientist of Universal Laboratories, Florida, United States & Eastman Kodak Company
both started their research work in that direction & the outcome of their efforts is the new
generation of display technologies named OLED (Organic Light Emitting Diode) Technology. In
the flat panel display zone unlike traditional Liquid-Crystal Displays OLEDs are self luminous &
do not require any kind of backlighting. This eliminates the need for bulky & environmentally
undesirable mercury lamps and yields a thinner, more compact display. Unlike other flat panel
displays OLED has a wide viewing angle (up to 160 degrees), even in bright light. Their low
power consumption (only 2 to 10 volts) provides for maximum efficiency and helps minimize
heat and electric interference in electronic devices. Because of this combination of these features,
OLED displays communicate more information in a more engaging way while adding less
weight and taking up less space. Their application in numerous devices is not only a future
possibility but a current reality.

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LIST OF FIGURES
Figure 1. Demonstration of flexible OLED device 9
Figure 2. Structure of OLED 12
Figure 3. Triplet state 14
Figure 4. Two different way of decay 15
Figure 5. Single organic layer 16
Figure 6. Two organic layer 17
Figure 7. Multilayer organic light emitting diode 17
Figure 8. Recombination region 19
Figure 9. Layer sequence and energy level diagram for OLED 21
Figure 10. OLED Passive matrix 23

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Figure 11. OLED Active matrix 24
Figure 12. OLED Transparent structure 25
Figure 13. OLED Top emitting structure 26
Figure 14. Foldable OLED 26
Figure 15. White OLED 27
Figure 16. Samsung galaxy round 33
Figure 17. Blackberry Q30 33
Figure 18. Sony XEL-1,World first OLED TV 33
Figure 19. Kodak LS633 34
Figure 20. Turn light flaps 34
Figure 21. Wallpaper lighting 35
Figure 22. Scroll laptop 35
Figure 23. Toshiba ultra thin flexible OLED 35

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LIST OF TABLES
Table 1: Comparison of organic OLED and LCD 28

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TABLE OF CONTENTS
Page no.
Certificate..........................................................................................................................ii
Abstract ............................................................................................................................iii
Acknowledgment..............................................................................................................iv
List of Figure ....................................................................................................................vii
List of Table ......................................................................................................................ix
(1) Introduction………………………………………………………………………....8
(2) History……………………………………………………………………………….10
(3) Components of an OLED…………………………………………………………..12
(4) Working Operation………………………………………………………………....14
(5) Types of OLED……………………………………………………………………..22
(6) OLED and LCD comparison…………………........................................................28
(7) Advantages………………………………………………………………………….30
(8) Disadvantages…………………………………………………………………….....31
(9) Current and future OLED Applications………………………………………….33
(10) Efficiency of OLED………………………………………………………………..36
(11) The Organic Future………………………………………………………………..37
(12) Conclusion……………………………………………………………………….....38
References………………………………………………………………………….39

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INTRODUCTION
Scientific research in the area of semiconducting organic materials as the active substance in
light emitting diodes (LEDs) has increased immensely during the last four decades. Organic
semiconductors was first reported in the 60:s and then the materials were only considered to be
merely a scientific curiosity. (They are named organic because they consist primarily of carbon,
hydrogen and oxygen.). However when it was recognized in the eighties that many of them are
photoconductive under visible light, industrial interests were attracted. Many major electronic
companies, such as Philips and Pioneer, are today investing a considerable amount of money in
the science of organic electronic and optoelectronic devices. The major reason for the big
attention to these devices is that they possibly could be much more efficient than today’s
components when it comes to power consumption and produced light. Common light emitters
today, Light Emitting Diodes (LEDs) and ordinary light bulbs consume more power than organic
diodes do. And the strive to decrease power consumption is always something of matter. Other
reasons for the industrial attention are i.e. that eventually organic full color displays will replace
today’s liquid crystal displays (LCDs) used in laptop computers and may even one day replace
our ordinary CRT-screens.
Organic light-emitting devices (OLEDs) operate on the principle of converting
electrical energy into light, a phenomenon known as electroluminescence. They exploit the
properties of certain organic materials which emit light when an electric current passes through
them. In its simplest form, an OLED consists of a layer of this luminescent material sandwiched
between two electrodes. When an electric current is passed between the electrodes, through the
organic layer, light is emitted with a colour that depends on the particular material used. In order
to observe the light emitted by an OLED, at least one of the electrodes must be transparent.
When OLEDs are used as pixels in flat panel displays they have some advantages
over backlit active-matrix LCD displays - greater viewing angle, lighter weight, and quicker
response. Since only the part of the display that is actually lit up consumes power, the most
efficient OLEDs available today use less power.

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Figure.1 Demonstration of a flexible OLED device
Based on these advantages, OLEDs have been proposed for a wide range of display
applications including magnified micro displays, wearable, head-mounted computers, digital
cameras, personal digital assistants, smart pagers, virtual reality games, and mobile phones as
well as medical, automotive, and other industrial applications.

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HISTORY
The first observations of electroluminescence in organic materials were in the early 1950s by
André Bernanose and co-workers at the Nancy-Université, France. They applied high-
voltage alternating current (AC) fields in air to materials such as acridine orange, either
deposited on or dissolved in cellulose or cellophane thin films. The proposed mechanism was
either direct excitation of the dye molecules or excitation of electrons.
In 1960, Martin Pope and co-workers at New York University developed ohmic dark-
injecting electrode contacts to organic crystals. They further described the necessary energetic
requirements (work functions) for hole and electron injecting electrode contacts. These contacts
are the basis of charge injection in all modern OLED devices. Pope's group also first observed
direct current (DC) electroluminescence under vacuum on a pure single crystal of anthracene and
on anthracene crystals doped with tetracene in 1963 using a small area silver electrode at 400 V.
The proposed mechanism was field-accelerated electron excitation of molecular fluorescence.
Pope's group reported in 1965 that in the absence of an external electric field, the
electroluminescence in anthracene crystals is caused by the recombination of a thermalized
electron and hole, and that the conducting level of anthracene is higher in energy than the exciton
energy level. Also in 1965, W. Helfrich and W. G. Schneider of the National Research
Council in Canada produced double injection recombination electroluminescence for the first
time in an anthracene single crystal using hole and electron injecting electrodes, the forerunner
of modern double injection devices. In the same year, Dow Chemical researchers patented a
method of preparing electroluminescent cells using high voltage (500–1500 V) AC-driven (100–
3000 Hz) electrically insulated one millimeter thin layers of a melted phosphor consisting of
ground anthracene powder, tetracene, and graphite powder. Their proposed mechanism
involved electronic excitation at the contacts between the graphite particles and the anthracene
molecules.
Electroluminescence from polymer films was first observed by Roger Partridge at
the National Physical Laboratory in the United Kingdom. The device consisted of a film of
poly(n-vinylcarbazole) up to 2.2 micrometers thick located between two charge injecting
electrodes. The results of the project were patented in 1975 and published in 1983.

9
The first diode device was reported at Eastman Kodak by Ching W. Tang and Steven
Van Slyke in 1987. This device used a novel two-layer structure with separate hole transporting
and electron transporting layers such that recombination and light emission occurred in the
middle of the organic layer. This resulted in a reduction in operating voltage and improvements
in efficiency and led to the current era of OLED research and device production.
Research into polymer electroluminescence culminated in 1990 with J. H. Burroughes et
al. at the Cavendish Laboratory in Cambridge reporting a high efficiency green light-emitting
polymer based device using 100 nm thick films of poly(p-phenylene vinylene).

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COMPONENTS OF AN OLED
The components in an OLED differ according to the number of layers of the organic material.
There is a basic single layer OLED, two layer and also three layer OLED’s. As the number of
layers increase the efficiency of the device also increases. The increase in layers also helps in
injecting charges at the electrodes and thus helps in blocking a charge from being dumped after
reaching the opposite electrode. Any type of OLED consists of the following components.
1. An emissive layer
2. A conducting layer
3. A substrate
4. Anode and cathode terminals.
Figure.2 Stucture of OLED
 Substrate- The substrate supports the OLED.
Example: clear plastic, glass, foil.

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 Anode- The anode removes electrons when current flows through the device.
Example: indium tin oxide
 Organic layers- These layers are made of organic molecules or polymers.
o Conductive layer- This layer is made of organic plastic molecules that
send electrons out from the anode.
Example: polyaniline, polystyrene
o Emissive layer- This layer is made of organic plastic molecules
(different ones from the conducting layer) that transport electrons from
the cathode; this is where light is made.
Example: polyfluorine, Alq3
 Cathode- The cathode injects electrons when a current flows through the device. (It may
or may not be transparent depending on the device)
Example: Mg, Al, Ba, Ca

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WORKING OPERATION
The organic light emitting diode (OLED) is a p-n diode, in which charge-carriers (e-h pairs)
recombine to emit photons in an organic layer. The thickness of this layer is approximately 100
nm (experiments have shown that 70 nm is an optimal thickness). When an electron and a hole
recombine, an excited state called an exciton is formed. Depending on the spin of the e-h pair,
the excitation is either a singlet or a triplet. An electron can have two different spins, spin up and
spin down. When the spin of two particles is the same, they are said to be in a spin-paired, or a
triplet state, and when the spin is opposite they are in a spin-paired singlet state.
Figure.3 Triplet State
On the average, one singlet and three triplets are formed for every four electron-hole pairs, and
this is a big inefficiency in the operation of the diodes. A singlet state decays very quickly,
within a few nanoseconds, and thereby emits a photon in a process called fluorescence. A triplet
state, however, is much more long-lived (1 ms - 1 s), and generally just produce heat. One
method of improving the performance is to add a phosphorescent material to one of the layers in

13
the OLED. This is done by adding a heavy metal such as iridium or platinum. The excitation can
then transfer its energy to a phosphorescent molecule which in turn emits a photon. It is however
a problem that few phosphorescent materials are efficient emitters at room temperature.
Figure.4 Two different ways of decay
There have been devices manufactured which transforms both singlet and triplet states in a host
to a singlet state in the fluorescent dye. This is done by using a phosphorescent compound which
both the singlets and triplets transfer their energy to, after which the compound transfer its
energy to a fluorescent material which then emits light.
Using one organic layer has some problems associated with it. The electrodes energy
levels have to be matched very closely, otherwise the electron and hole currents will not be
properly balanced. This leads to a waste in energy since charges can then pass the entire structure

14
without recombining, and this lowers the efficiency of the device. With two organic layers, the
situation improves dramatically. Now the different layers can be optimized for the electrons and
holes respectively. The charges are blocked at the interface of the materials, and “waits” there for
a “partner”.
Figure.5 Single Organic layer
Considerably better balance can be achieved by using two organic layers one of which is
matched to the anode and transports holes with the other optimized for electron injection and
transport. Each sign of charge is blocked at the interface between the two organic layers and tend
to "wait" there until a partner is found.
Recombination therefore occurs with the excitation forming in the organic material
with the lower energy gap. The fact that it forms near the interface is also beneficial in
preventing quenching of the luminescence that can occur when the excitation is near one of the
electrodes.

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Figure.6 Two Organic layers
Another improvement is to introduce a third material specifically chosen for its
luminescent efficiency. Now the three organic materials can be separately optimized for electron
transport, for hole transport and for luminescence.
Figure.7 Multilayer organic light emitting diode
The principle of operation of organic light emitting diodes (OLEDs) is similar to that of
inorganic light emitting diodes (LEDs). Holes and electrons are injected from opposite contacts
into the organic layer sequence and transported to the emitter layer. Recombination leads to the
formation of singlet excitons that decay radiatively. In more detail, electroluminescence of

16
organic thin film devices can be divided into five processes that are important for device
operation:
(a) Injection: Electrons are injected from a low work function metal con-tact, e. g. Ca or Mg.
The latter is usually chosen for reasons of stability. A wide-gap transparent indium-tin-oxide
(ITO) or polyaniline thin film is used for hole injection. In addition, the efficiency of carrier
injection can be improved by choosing organic hole and electron injection layers with a low
HOMO (high occupied molecular orbital) or high LUMO (lowest unoccupied molecular orbital)
level, respectively.
(b) Transport: In contrast to inorganic semiconductors, high p- or n-conducting organic thin
films can only rarely be obtained by doping. Therefore, preferentially hole or electron
transporting organic compounds with sufficient mobility have to be used to transport the charge
carriers to the re-combination site. Since carriers of opposite polarity also migrate to some
extent, a minimum thickness is necessary to prevent non-radiative recombination at the opposite
contact. Thin electron or hole blocking layers can be inserted to improve the selective carrier
transport.
(c) Recombination: The efficiency of electron-hole recombination leading to the creation of
singlet excitons is mainly influenced by the overlap of electron and hole densities that originate
from carrier injection into the emitter layer. Recombination of filled traps and free carriers may
also attribute to the formation of excited states. Energy barriers for electrons and holes to both
sides of the emitter layer allow to spatially confine and improve the recombination process.
(d) Migration and (e) decay: Singlet excitons will migrate with an average diffusion length of
about 20 nm followed by a radiative or non-radiative decay. Embedding the emitter layer into
transport layers with higher singlet excitation energies leads to a confinement of the singlet
excitons and avoids non-radiative decay paths. Doping of the emitter layer with organic dye
molecules allows to transfer energy from the host to the guest molecule in order to tune the
emission wavelength or to increase the luminous efficiency.

17
When biased, charge is injected into the highest occupied molecular
orbital (HOMO) at the anode (positive), and the lowest unoccupied molecular orbital (LUMO) at
the cathode (negative), and these injected charges (referred to as “holes” and “electrons,”
respectively) migrate in the applied field until two charges of opposite polarity encounter each
other, at which point they annihilate and produce a radiative state emitting photons with energy
hf =Eg . The energy gap is the difference between the HOMO and LUMO level of the emitting
layer, and it is largely responsible for the observed color of the light.
Figure.8 Recombination Region

18

19
Figure.9 Layer sequences and energy level diagrams for OLEDs with (a) single layer,
(b) single hetero structure, (c) double hetero structure, and (d)multiplayer structure
with separate hole and electron injection and transport layers.

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TYPES OF OLED
There are several types of OLEDs:
 Passive-matrix OLED
 Active-matrix OLED
 Transparent OLED
 Top-emitting OLED
 Foldable OLED
 White OLED
Passive-matrix OLED (PMOLED)
PMOLEDs have strips of cathode, organic layers and strips of anode. The anode strips are
arranged perpendicular to the cathode strips. The intersections of the cathode and anode make up
the pixels where light is emitted. External circuitry applies current to selected strips of anode and
cathode, determining which pixels get turned on and which pixels remain off. Again, the
brightness of each pixel is proportional to the amount of applied current.
PMOLEDs are easy to make, but they consume more power than other types of OLED, mainly
due to the power needed for the external circuitry. PMOLEDs are most efficient for text and
icons and are best suited for small screens (2- to 3-inch diagonal) such as those you find in CELL
PHONES, PDA’s and MP3 Players. Even with the external circuitry, passive-matrix OLEDs
consume less battery power than the LCDs that currently power these devices.

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Figure.10 OLED Passive Matrix
Active-matrix OLED (AMOLED)
AMOLEDs have full layers of cathode, organic molecules and anode, but the anode layer
overlays a thin film transistor (TFT) array that forms a matrix. The TFT array itself is the
circuitry that determines which pixels get turned on to form an image.
AMOLEDs consume less power than PMOLEDs because the TFT array requires less
power than external circuitry, so they are efficient for large displays. AMOLEDs also have faster
refresh rates suitable for video. The best uses for AMOLEDs are computer monitors, large-
screen TVs and electronic signs or billboards.

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Figure.11 OLED Active Matrix
Transparent OLED
Transparent OLEDs have only transparent components (substrate, cathode and anode) and,
when turned off, are up to 85 percent as transparent as their substrate. When a transparent OLED
display is turned on, it allows light to pass in both directions. A transparent OLED display can be
either active- or passive-matrix. This technology can be used for heads-up displays.

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Figure.12 OLED Transparent Structure
Top-emitting OLED
Top-emitting OLEDs have a substrate that is either opaque or reflective. They are best suited to
active-matrix design. Manufacturers may use top-emitting OLED displays in SMART CARDS

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Figure.13 OLED Top-Emitting Structure
Foldable OLED
Foldable OLEDs have substrates made of very flexible metallic foils or plastics. Foldable
OLEDs are very lightweight and durable. Their use in devices such as cell phones and PDAs can
reduce breakage, a major cause for return or repair. Potentially, foldable OLED displays can be
attached to fabrics to create "smart" clothing, such as outdoor survival clothing with an
integrated computer chip, cell phone, GPS receiver and OLED display sewn into it.
Figure.14 Foldable OLED

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White OLED
White OLEDs emit white light that is brighter, more uniform and more energy efficient than that
emitted by fluorescent lights. White OLEDs also have the true-color qualities of incandescent
lighting. Because OLEDs can be made in large sheets, they can replace fluorescent lights that are
currently used in homes and buildings. Their use could potentially reduce energy costs for
lighting.
Figure.15 White OLED

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ORGANIC LED AND LIQUID CRSYTAL DISPLAY
COMPARISON
Organic LED panel Liquid Crystal Panel
A luminous form Self emission of light Back light or outside light is
necessary
Consumption of Electric
power
It is lowered to about mW
though it is a little higher
than the reflection type
liquid crystal panel
It is abundant when back light
is used
Colour Indication form The fluorescent material
of RGB is arranged in
order and or a colour filter
is used.
A colour filter is used.
High brightness 100 cd/m2 6 cd/m2
The dimension of the panel Several-inches type in the
future to about 10-inch
type.Goal
It is produced to 28-inch type in
the future to 30-inch type.Goal
Contrast 100:14 6:1
The thickness of the panel It is thin with a little over
1mm
When back light is used it is
thick with 5mm.
The mass of panel It becomes light weight
more than 1gm more than
the liquid crystal panel in
the case of one for
portable telephone
With the one for the portable
telephone.10 gm weak degree.
Answer time Several us Several ns
A wide use of temperature
range
86 *C ~ -40 *C ~ -10 *C
The corner of the view Horizontal 180 * Horizontal 120* ~ 170*

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ADVANTAGES OF OLED
The different manufacturing process of OLEDs lends itself to several advantages over flat-panel
displays made with LCD technology.
 Lower cost in the future: OLEDs can be printed onto any suitable substrate by an inkjet
printer or even by screen printing, theoretically making them cheaper to produce than
LCD or plasma display. However, fabrication of the OLED substrate is more costly than
that of a TFT LCD, until mass production methods lower cost through scalability.
 Light weight & flexible plastic substrates: OLED displays can be fabricated on flexible
plastic substrates leading to the possibility of flexible organic light-emitting diodes being
fabricated or other new applications such as roll-up displays embedded in fabrics or
clothing.
 Wider viewing angles & improved brightness: OLEDs can enable a greater artificial
contrast ratio (both dynamic range and static, measured in purely dark conditions) and
viewing angle compared to LCDs because OLED pixels directly emit light.
 Better power efficiency: LCDs filter the light emitted from a back light
 Response time: OLEDs can also have a faster response time than standard LCD screens.

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DISADVANTAGES OF OLED
OLED seem to be the perfect technology for all types of displays; however, they do have some
problems, including:

 Outdoor performance: As an emissive display technology, OLEDs rely completely
upon converting electricity to light, unlike most LCDs which are to some extent reflective
 Power consumption: While an OLED will consume around 40% of the power of an
LCD displaying an image
 Screen burn-in: Unlike displays with a common light source, the brightness of each
OLED pixel fades depending on the content displayed. The varied lifespan of the organic
dyes can cause a discrepancy between red, green, and blue intensity. This leads to image
persistence, also known as burn in
 UV sensitivity: OLED displays can be damaged by prolonged exposure to UV light. The
most pronounced example of this can be seen with a near UV laser (such as a Bluray
pointer) and can damage the display almost instantly with more than 20mW leading to
dim or dead spots where the beam is focused.
 Lifetime - While red and green OLED films have longer lifetimes (46,000 to 230,000
hours), blue organics currently have much shorter lifetimes (up to around 14,000 hours
 Manufacturing - Manufacturing processes are expensive right now.
 Color balance issues: Additionally, as the OLED material used to produce blue light
degrades significantly more rapidly than the materials that produce other colors, blue

29
light output will decrease relative to the other colors of light. This differential color
output change will change the color balance of the display and is much more noticeable
than a decrease in overall luminance.
 Water damage: Water can damage the organic materials of the displays. Therefore,
improved sealing processes are important for practical manufacturing. Water damage
may especially limit the longevity of more flexible displays.

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CURRENT AND FUTURE OLED APPLICATIONS
Currently, OLEDs are used in small screen devices like cell phones, digital cameras etc.
Some examples of OLED applications are as follows:
 Mobile Phones- Mobile phones were the first to adopt AMOLED displays and is the
largest market for OLEDs today.
Figure.16 Samsung Galaxy Round Figure.17 Blackberry Q30
 OLED TVs- OLED TVs had begun shipping in 2013 but their prices are still very high.
Figure.18 Sony XEL-1, world’s 1st OLED TV
 Digital Cameras- Several compact and high-end cameras use AMOLED displays that
offer rich colors and high contrast and brightness. Kodak was the first to release a digital
camera with an OLED display in March 2003, the EasyShare LS633.

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Figure.19 Kodak LS633
 OLED Lamps- OLED lamps are currently very expensive, but already several
companies are offering these in the premium lighting category.
Figure.20 Turn lights flaps
 Other devices- OLEDs are also used in wrist watches, headsets, car audio systems,
remote controllers, digital photo frames and many other kinds of devices.
Future uses of OLED-
 Wallpaper lighting defining new ways to light a space

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Figure.21 Wallpaper Lighting
 Scroll Laptop
Figure.22 Scroll Laptop
 Rollable OLED television
Figure.23 Toshiba ultra thin flexible OLED

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Efficiency of OLED
Recent advantages in boosting the efficiency of OLED light emission have led to the possibility
that OLEDs will find early uses in many battery-powered electronic appliances such as cell
phones, game boys and personal digital assistants. Typical external quantum efficiencies of
OLEDs made using a single fluorescent material that both conducts electrons and radiates
photons are greater than 1 percent. But by using guest-host organic material systems where the
radiative guest fluorescent or phosphorescent dye molecule is doped at low concentration into a
conducting molecular host thin film, the efficiency can be substantially increased to 10 percent
or higher for phosphorescence or up to approximately 3 percent for fluorescence.
Currently, efficiencies of the best doped OLEDs exceed that of incandescent light bulbs.
Efficiencies of 20 lumens per watt have been reported for yellow-green-emitting polymer
devices and 40 lm/W for a typical incandescent light bulb. It is reasonable to that of
fluorescent room lighting will be achieved by using phosphorescent OLEDs.
The green device which shows highest efficiency is based on factris(2-phenylpyridine)
iridium[Ir(PPY)3],a green electro phosphorescent material. Thus phosphorescent emission
originates from a long-lived triplet state.

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The Organic Future
The first products using organic displays are already being introduced into the market place. And while it
is always difficult to predict when and what future products will be introduced, many manufacturers are
now working to introduce cell phones and personal digital assistants with OLED displays within the next
one or two years. The ultimate goal of using high-efficiency, phosphorescent, flexible OLED displays in
lap top computers and even for home video applications may be no more than a few years into future.
However, there remains much to be done if organics are to establish a foothold in the display
market. Achieving higher efficiencies, lower operating voltages, and lower device life times are
all challenges still to be met. But, given the aggressive worldwide efforts in this area, emissive
organic thin films have an excellent chance of becoming the technology of choice for the next
generation of high-resolution, high-efficiency flat panel displays.
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.

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CONCLUSION
Performance of organic LEDs depend upon many parameters such as electron and hole
mobility, magnitude of applied field, nature of hole and electron transport layers and excited
life-times. Organic materials are poised as never before to transform the world IF circuit and
display technology. Major electronics firms are betting that the future holds tremendous
opportunity for the low cost and sometimes surprisingly high performance offered by organic
electronic and optoelectronic devices.
Organic Light Emitting Diodes are evolving as the next generation of light
sources. Presently researchers have been going on to develop a 1.5 emitting device. This
wavelength is of special interest for telecommunications as it is the low-loss wavelength for
optical fibre communications. Organic full-colour displays may eventually replace liquid crystal
displays for use with lap top and even desktop computers. Researches are going on this subject
and it is sure that OLED will emerge as future solid state light source.

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