SOLID STATE LIGHTING TABLE OF CONTENTS: Abstract History Introduction Definition: LED Mechanism Types of LEDs Available colors in LEDs Manufacturing the White LEDs LED Fabrication process Lowering the operating temperature Reduction of heat emission Advantages Limiting Factors Applications Conclusion Bibliography
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Just as transistors replaced vacuum tubes 50 years ago, and just as flat panel
displays are now replacing CRT monitors and televisions, solid state lighting will likely
take the place of incandescent and fluorescent lamps used for applications in general
illumination.
High power Light emitting diodes (LEDs) have begun to differentiate themselves
from their more common cousins the indicator LED. Today these LEDs are designed to
generate 10-100 lm per LED with efficiencies that surpass incandescent and halogen
bulbs. The term "solid state" refers commonly to light emitted by sol
electroluminescence, as opposed to incandescent bulbs (which use thermal radiation) or
fluorescent tubes. Compared to incandescent lighting, SSL creates visible light with
reduced heat generation or parasitic energy dissipation. Most common "white" LEDs
convert blue light from a solid-state device to an (approximate) white light spectrum
using photoluminescence, the same principle used in conventional fluorescent tubes.
Lighting uses 19 % of worldwide electrical energy; this could be reduced by 75 % if all
existing lighting were replaced by solid state lighting. SSL has been identified not only to
fill the efficiency gap but also to replace environmentally unfriendly com
fluorescence lamps and the associated problem of Mercury disposal. The LED is a
basically a small area source, often with extra optics added to the chip that shapes its
radiation pattern. The specific wavelength or color emitted by the LED depends on the
materials used to make the diode. It depends on the composition and condition of the
semi conducting of material used, and can be infrared, visible or near ultraviolet. We
demonstrate record performance and reliability for high power colored LEDs and showresults from the worlds first 100-plus lumen white LED lamp, the solid state equivalent
of Thomas Edison’s 20-W incandescent light bulb approximately one century later.
Solid-state lighting (SSL) refers to a type of lighting that uses semiconductor light-
emitting diodes (LEDs), organic light-emitting diodes (OLED), or polymer light-emitting
diodes (PLED) as sources of illumination rather than electrical filaments, plasma (used in
arc lamps such as fluorescent lamps), or gas.
History:
Oil lamp Incandescent bulbs Fluorescence &
discharge
The first known report of a light-emitting solid-state diode was made in 1907 by
the British experimenter H. J. Round. However, no practical use was made of the
discovery for several decades. Independently, Oleg Vladimirovich Losev published
"Luminous carborundum [silicon carbide] detector and detection with crystals" in the
Russian journal Telegrafiya Telefoniya bez Provodov (Wireless Telegraphy
Telephony). Losev's work languished for decades.
The first practical LED was invented by Nick Holonyak, Jr., in 1962 while he was
at General Electric Company. The first LEDs became commercially available in late
1960s, and were red. They were commonly used as replacements for incandescent
indicators, and in seven-segment displays, first in expensive equipment such
laboratory and electronics test equipment, then later in such appliances as TVs, radios,telephones, calculators, and even watches. These red LEDs were bright enough only for
use as indicators, as the light output was not enough to illuminate an area. Later, other
colors became widely available and also appeared in appliances and equipment. As the
LED materials technology became more advanced, the light output was increased, and
LEDs became bright enough to be used for illumination.