LED TECHNOLOGY
LED basics – from technological background to historical facts
Basic principle of a LED (light emitting diode)
Several layers of semi-conducting material.
Emits light in a particular colour.
Two material systems used.
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.
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.
The history of the LED
1907
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".
1921
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.
1935
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.
1951
The development of a transistor marks a scientific step forward in semiconductor physics. It is now possible to explain light emission.
1962
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.
1971
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.
1993
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.
1995
The first LED with white light from luminescence conversion is presented and is launched on the market two years later.
2006
The first light-emitting diodes with 100 lumens per watt are produced. This efficiency can be outmatched only by gas discharge lamps.
2010
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.
Advantages of LED technology
Low power consumption
High efficiency level
Long lifetime
Smallest possible dimensions
High resistance to switching cycles
Immediate light at switching on
Wide operating temperature range
High impact and vibration resistance
Mercury-free
The Application of LED Technology in Daily Life
Status indicators and displays: for example these little lights on the kitchen or movile phones
Message displays
Traffic lights and signals
Screens for TV and for mobile phones too
Brake lights and many lights in the cars
Residential lighting> is becoming more and more common because itis cheaper
Outdoor lighting> for the same reason iis very used for example in donosti the council changed the christmas lights to leds to
Flashlight
Factors having an influence on reliability and operating life of the individual LED
-Temperature:
Production of light brings heat.
Heat has negative effect on lifespan.
LED work's best in cooler conditions.
-Mechanical effect:
Causes of occurrence of mechanical forces can be versatile.
LED exposure to this can negatively influence it's operating life.
-Power consumption:
Every LED and LED module can be operated within a specific current range.
-LIghts:
Housing design plays an important role
-Dampness:
LED is very good in structure.
But it is very easy to break. It isn’t very thick.
-Chemicals:
There are some chemical negative effect that can cause the malfuncion of the led. As corrosive atmosphere because of the sulfur dioxide . The climate of the coast because it is very salty.
Swimming pools with medium chloride content
