Organic Light Emitting Diodes (OLED)
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#1
07-04-2009, 11:40 PM


Definition

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 60Confused and then the materials where 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 todays 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 todays 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 color 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.
Based on these advantages, OLEDs have been proposed for a wide range of display applications including magnified microdisplays, 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.

OLED Versus LED

Electronically, OLED is similar to old-fashioned LEDs -- put a low voltage across them and they glow. But that's as far as the similarity goes: instead of being made out of semiconducting metals, OLEDs are made from polymers, plastics or other carbon-containing compounds. These can be made very cheaply and turned into devices without all the expensive palaver that goes with semiconductor fabrication.

Light-emitting diodes, based upon semiconductors such as Gallium Arsenide, Gallium Phosphide, and, most recently, Gallium Nitride, have been around since the late '50s. They are mostly used as indicator lamps, although they were used in calculators before liquid crystals, and are used in large advertising signs, where they are valued for very long life and high brightness. Such crystalline LEDs are not inexpensive, and it is very difficult to integrate them into small high-resolution displays.
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lakshmi1988
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#2
12-07-2009, 10:07 PM

can yu send me the full report for the topic -Organic light emitting diodes
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electronix
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26-07-2009, 06:05 PM

i want a full report and an abstract will also do.
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Akkaprojectreport
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03-02-2010, 04:03 PM

(26-07-2009, 06:05 PM)electronix Wrote: i want a full report and an abstract will also do.
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seminarbuddy
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03-02-2010, 07:01 PM

A N organic light-emitting diode (OLED) is a special type of light-emitting diode (LED). An OLED is composed of an undoped organic layer that is sandwiched between two
electrodes. Electrons and holes are injected from either side of the electrode which drift due to the applied electric field. excitons are formed when electrons and holes meet at the bulk or the interface. These excitons will decay to produce light emission. based on the materials used for OLEDs, they can be divided into twoclasses: small-molecular OLEDs and polymer light-emitting diodes (PLEDs). Generally, an OLED refers to small-molecular OLED.

II. SMALL-MOLECULAR ORGANIC LIGHT-EMITTING DIODES
a) Device structure:
A small-molecular OLED consists of one organic layer or multiple organic layers between two electrodes. A one organic layer device is called a single layer device. The
organic material must serve all the three main functions: electron transport, hole transport and emission. multiple organic layers in the OLED structure result in high efficiency because there is no surplus uncombined electrons.
The three layers in a typical OLED are:
1)employs an electron transport layer (ETL),
2) a hole transport layer
3)Emissive layer

b) Electrodes
one electrode should be transparent to allow the emission of light from the
device. indium-tin-oxide (ITO) is commonly used for this purpose. for anodes are Al, Ma, Ca, etc are used.

c)Materials
The typically used n-type materials for ETL are Alq3, PBD,
etc. And the generally used p-type materials for HTL are NPB
and TPD, etc.

d)Fabrications
polymers are usually deposited by dissolving an organic solvent followed by spin-coating,
drop-casting, ink-jet printing or roll-to-roll web coating. This is because they have high molecular weights and cannot be fabricated using conventional methods.

APPLICATIONS AND CHALLENGES
1)Solid-State Lighting:
the power efficiency of an OLED has already achieved 30-60
lm/W in the laboratory Therefore, OLED will be a good
candidate for the new generation of the solid-state lighting.

2)Flat-Panel Displays
OLED displays offer higher contrast, truer colors, higher
brightness, wider viewing angles, better temperature tolerance,
and faster response times than LC displays, which make it have
the potential to be the next-generation of the display device.
OLED displays do not have to be back-lit. Thusthey have the potential
thinner, lighter and more flexible than conventional LC
displays. It can be also used in large screens and flexible.

Full report download:


.pdf   OLED.pdf (Size: 476.56 KB / Downloads: 411)
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03-02-2010, 07:06 PM

see
topicideashow-to-Organic-light-emitting-diode-OLED-seminar and presentation-report
topicideashow-to-Organic-LED-full-report for more information on Organic Light Emitting Diodes (OLED)
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11-05-2012, 01:28 PM

Organic Light Emitting Diodes (OLED)



.pdf   organic-light-emitting-diodes.pdf (Size: 445.67 KB / Downloads: 22)

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 60Confused and then the materials
where 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 todays 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 todays 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 color 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.
Organic Light Emitting Diodes bestneo.com
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.
Based on these advantages, OLEDs have been proposed for a wide range of
display applications including magnified microdisplays, 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.
Organic Light Emitting Diodes bestneo.com

OLED Versus LED

Electronically, OLED is similar to old-fashioned LEDs -- put a low voltage across
them and they glow. But that's as far as the similarity goes: instead of being made out of
semiconducting metals, OLEDs are made from polymers, plastics or other carboncontaining
compounds. These can be made very cheaply and turned into devices without
all the expensive palaver that goes with semiconductor fabrication.
Light-emitting diodes, based upon semiconductors such as Gallium Arsenide,
Gallium Phosphide, and, most recently, Gallium Nitride, have been around since the late
'50s. They are mostly used as indicator lamps, although they were used in calculators
before liquid crystals, and are used in large advertising signs, where they are valued for
very long life and high brightness. Such crystalline LEDs are not inexpensive, and it is
very difficult to integrate them into small high-resolution displays.
The operation of an LED is based upon the fact that semiconductors can be of two
types, p-type or n-type, depending upon whether dopants pull electrons out of the crystal,
forming "holes", or add electrons. An LED is formed when p-type and n-type materials
are joined. When a voltage is applied, causing electrons to flow through the structure,
electrons flow into the p-type material, and holes flow into the n-type material. An
electron-hole combination is unstable; there is too much potential energy to be released.
As a result, they combine and release the energy in the form of light. This can be a very
efficient way to convert electricity to light.
There is a wide class of organic compounds, called conjugated organics or
conjugated polymers, which have many of the characteristics of semiconductors. They
have energy gaps of about the same magnitude, they are poor conductors without
dopants, and they can be doped to conduct by electrons (n-type) or holes (p-type).
Organic Light Emitting Diodes bestneo.com
Initially, these materials were used as photoconductors, to replace inorganic
semiconductor photoconductors, such as selenium, in copiers. About fifteen years ago it
was discovered that, just as with crystalline semiconductors, p-type and n-type organic
materials can be combined to make light-emitting diodes whereby a current passing
through a simple layered structure produces visible light with high efficiency.
Since light-emitting diodes, as their name suggests, actually generate their own
light while using very little battery power, they have long been viewed as an obviously
better way to create displays. Unfortunately, while conventional L.E.D.'s work well in
giant screens and advertising displays like those in Times Square, they cannot easily be
used to create small, high-resolution screens for portable computers.
OLED is an emissive display technology based on thin organic light-emitting
films. Like conventional inorganic light emitting diodes (LED), OLED requires a lowdrive
voltage to produce bright visible light. But unlike discrete LEDs, which have
crystalline origins, thin film-based OLEDs have area emitters that can easily be patterned
to produce flat-panel displays. Because OLEDs are self-luminous, backlights are not
required as in liquid-crystal displays (LCDs). OLEDs have very low power requirements
and are thin, bright and efficient.
Because crystalline order is not required, organic materials, both molecular and
polymeric, can be deposited far more cheaply than the inorganic semiconductors of
conventional LED’s. Patterning is also easier, and may even be accomplished by
techniques borrowed from the printing industry. Displays can be prepared on flexible,
transparent substrates such as plastic. These characteristics form the basis for a display
technology that can eventually replace even paper, providing the same resolution and
reading comfort in a long-lived, fully reusable (and eventually recyclable) digital
medium.
Organic Light Emitting Diodes bestneo.com
Also OLEDs are much more efficient than todays 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, To tell something about
the efficiency of components we will use the concept of Quantum Efficiency (QE), which
is defined as the relation between photons produced and electrons injected. To achieve a
high QE for a light bulb it would be necessary to change the relation between produced
heat and produced light. To increase the QE for a LED it is necessary to limit the
absorption of the photons produced. It has been generally observed that organic devices
can and will produce high quantum efficiencies than organic diodes do.
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