Emitting Diodes (OLED)
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 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.
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.
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.
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.
You may also like this : Laser Communications, Solar Power Satellites, MIMO Wireless Channels, Fractal Robots, Stereoscopic Imaging, Ultra-Wideband, Home Networking, Digital Cinema, Face Recognition Technology, Universal Asynchronous Receiver Transmitter , Automatic Teller Machine , Wavelength Division Multiplexing , Object Oriented Concepts, Frequency Division Multiple Access , Real-Time Obstacle Avoidance, Delay Tolerant Networking , EDGE, Psychoacoustics , Integer Fast Fourier Transform, Worldwide Inter operatibility for Microwave Access , Code Division Multiple Access, Optical Coherence Tomography , Symbian OS , Home Networking , Guided Missiles , AC Performance Of Nanoelectronics , Acoustics , BiCMOS technology , Fuzzy based Washing Machine , Low Memory Color Image Zero Tree Coding , Stealth Fighter , Border Security Using Wireless Integrated Network Sensors , A Basic Touch-Sensor Screen System , GSM Security And Encryption, Design of 2-D Filters using a Parallel Processor Architecture , Software-Defined Radio , Smart Dust , Adaptive Blind Noise Suppression , An Efficient Algorithm for iris pattern , Significance of real-time transport Protocol in VOIP, Storage Area Networks , Quantum Information Technology , Money Pad, The Future Wallet, Buffer overflow attack , Robotic Surgery, Swarm intelligence & traffic Safety , Smart card , Cellular Through Remote Control Switch, Terrestrial Trunked Radio , HVAC,Electronics Seminar Reports, PPT and PDF.