The history of the LED
For over 30 years, LEDs have been used in various areas of application, whether for industrial systems, hi-fi equipment, car lights or advertising. LED technical development continues to stride ahead. In the course of recent years, the white LEDs’ luminous efficacy has increased to a startling 130 lumens per watt and more. This is a trend that will continue into the future. In addition, the physical effect of electroluminescence was discovered more than 100 years ago.
In LED chips, electromagnetic radiation in the form of light is emitted by applying a certain voltage.
| A short glance back over 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”. Since, however, he was working mainly on a new direction-finding system for marine transport, this discovery initially is forgotten. |
| 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. |