Light emitting diode

Description

A small, solid, semiconducting crystals that produces light from electricity. Light emitting diodes, or LEDs, were first invented by General Electric in 1962. The light is emitted at a very narrow range of wavelengths by the transition of electrons between energy levels. These early red light emitting LEDs emitted low levels of light and were used in displays, sensors, and electronic equipment. In the 1990s, blue (450 nm), blue-green, violet, ultraviolet and and white LEDs were developed by Shuji Nakamura in Japan based on InGaN/AlGaN. These blue LEDS produce a light density which is about 100 times higher. These GaN based LEDs are being used for traffic lights, car headlights, TV displays, copiers, and scanners. Because of their efficiency, these LEDs provide 50-70% energy savings when used to replace indoor lightbulbs and fluorescent tubes.

Synonyms and Related Terms

LED

Physical and Chemical Properties

Lifetimes estimated at 10,000 hours

Resources and Citations

• GE Lighting: www.gelighting.com/na/institute/ul_last100.html - gives date of first diode as 1962

• Eurotechnology.com on Blue LEDs at http://www.eurotechnology.com/bluelaser/blueslide15.html