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Transcript of LED Technology
The French physicist Georges Destriau discovers light emission in zinc sulfide. In honor of the Russian physicist, he calls the effect "Lossew light". Today Georges Destriau is credited as the inventor of electroluminescence.
The development of a transistor marks a scientific step forward in semiconductor physics. It is now possible to explain light emission.
The first red luminescence diode (type GaAsP), developed by American Nick Holonyak, enters the market. This first LED in the visible wavelength area marks the birth of the industrially-produced LED.
The Englishman Henry Joseph Round discovers that inorganic materials can light up when an electric current is applied. In the same year, he publishes his discovery in the journal "Electrical World".
The Russian physicist Oleg Lossew again observes the "Round effect" of light emission. In the succeeding years, from 1927 to 1942, he examined and described
this phenomenon in greater detail.
The history of the LED
As a result of the development of new semiconductor materials, LEDs are produced in new colors: green, orange and yellow. The LED's performance and effectiveness continues to improve.
Japanese Shuji Nakamura develops the first brilliant blue LED and a very efficient LED in the green spectrum range (InGaN diode). Some time later he also designs a white LED.
The first LED with white light from luminescence conversion is presented and is launched on the market two years later.
The first light-emitting diodes with 100 lumens per watt are produced. This efficiency can be outmatched only by gas discharge lamps.
LEDs of a certain color with a gigantic luminous efficacy of 250 lumens per watt are already being developed under laboratory conditions. Progress continues to surge ahead. Today, further development towards OLED is seen as the technology of the future.
The Application of LED Technology in Daily Life
Traffic lights and signals
Screens for TV
Status indicators and displays
Origin of the LED technology - the Electroluminescence
One of few instances where conversion of electronic energy into visible light generates no heat.
Can result from charge injection.
Basic principle of a LED (light emitting diode)
Several layers of semi-conducting material.
Emits light in a particular colour.
Two material systems used.
Advantages of LED technology
Low power consumption
High efficiency level
Smallest possible dimensions
High resistance to switching cycles
Immediate light at switching on
Wide operating temperature range
High impact and vibration resistance
Factors having an influence on reliability and operating life of the individual LED
Production of light brings heat.
Heat has negative effect on lifespan.
LED work's best in cooler conditions.
Causes of occurrence of mechanical forces can be versatile.
LED exposure to this can negatively influence it's operating life.
Every LED and LED module can be operated within a specific current range.
LED is ideal in structure.
Vulnerable to dampness.
The following effects, among other things, have a negative effect on the operating life:
Corrosive atmosphere (air with high sulfur dioxide content)
Coastal climate with medium salt content
Swimming pools with medium chloride content
LED basics – from technological background to historical facts
The production of the LED light colors
The light emitted from a light-emitting diode has a specific wavelength and thus a specific color. The latter depends on the LED's semiconductor material.
LED – the technology of the future
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Housing design plays an important role .
by Omar Al Sallaq