Light-emitting diode

"LED" redirects in this article. For other uses, see LED (disambiguation).
Light-emitting diode
RBG-LED. jpg
Red, pure green and blue LEDs of the 5mm diffused type
Type Passive, optoelectronic
Working principle Electroluminescence
Invented Oleg Losev (1927)[1][2][3]
James R. Biard (1961)[4]
Nick Holonyak (1962)[5]
First production 1968[6]
Electronic symbol
LED symbol. svg
Pin configuration anode and cathode


Parts of an LED. Although not directly labeled, the flat bottom surfaces of the anvil and post embedded inside the epoxy act as anchors, to prevent the conductors from being forcefully pulled out from mechanical strain or vibration.
Modern LED retrofit with E27 screw in base

A modern retrofit LED lamp with "bulb" shape, complete with aluminum heatsink, a light diffusing dome and E27 screw base, using a built-in power supply working on mains voltage
A light-emitting diode (LED) is a semiconductor light source.[7] LEDs are used as indicator lamps in many devices and are increasingly used for other lighting. Appearing as practical electronic components in 1962,[8] early LEDs emitted low-intensity red light, but modern versions are available across the visible, ultraviolet, and infrared wavelengths, with very high brightness.
When a light-emitting diode is switched on, electrons are able to recombine with holes within the device, releasing energy in the form of photons. This effect is called electroluminescence and the color of the light (corresponding to the energy of the photon) is determined by the energy band gap of the semiconductor. An LED is often small in area (less than 1 mm2), and integrated optical components may be used to shape its radiation pattern.[9] LEDs present many advantages over incandescent light sources including lower energy consumption, longer lifetime, improved physical robustness, smaller size, and faster switching. However, LEDs powerful enough for room lighting are relatively expensive and require more precise current and heat management than compact fluorescent lamp sources of comparable output.
Light-emitting diodes are used in applications as diverse as aviation lighting, digital microscopes, automotive lighting, advertising, general lighting, and traffic signals. LEDs have allowed new text, video displays, and sensors to be developed, while their high switching rates are also useful in advanced communications technology. Infrared LEDs are also used in the remote control units of many commercial products including televisions, DVD players and other domestic appliances. LEDs are also used in seven-segment display.