LEDs (Light Emitting Diode)

A light-emitting diode (LED) is a semiconductor device that emits visible light when an electric current passes through it. The light is not particularly bright, but in most LEDs it is monochromatic, occurring at a single wavelength.

The material used in the semiconducting element of an LED determines its colour. The two main types of LEDs presently used for lighting systems are aluminium gallium indium phosphide (AlGaInP or AlInGaP) alloys for red, orange and yellow LEDs; and indium gallium nitride (InGaN) alloys for green, blue and white LEDs. Slight changes in the composition of these alloys change the colour of the emitted light. The output from an LED can range from red (at a wavelength of approximately 700 nanometers) to blue-violet (about 400 nanometers). Some LEDs emit infrared (IR) energy (830 nanometers or longer); such a device is known as an infrared-emitting diode (IRED).

Compared to most typical light sources used for lighting applications, LEDs still have relatively low light output, and therefore, will continue to be packaged into arrays and other configurations to be useful in such applications. At present, single white LED packages have reached nearly 100 lumens. Of course, the light output varies depending upon wavelength. LEDs are important because due to their efficiency and low energy, they are beginning to replace most conventional light sources. LEDs are incorporated into bulbs and fixtures for general lighting applications. Small in size, LEDs provide unique design opportunities. Some LED bulb solutions may physically resemble familiar light bulbs and better match the appearance of traditional light bulbs.

LEDs offer a tremendous opportunity for innovation in lighting form factors and fit a wider breadth of applications than traditional lighting technologies. LEDs use heat sinks to absorb the heat produced by the LED and dissipate it into the surrounding environment. This keeps LEDs from overheating and burning out. Thermal management is generally the single most important factor in the successful performance of an LED over its lifetime. The higher the temperature at which the LEDs are operated, the more quickly the light will degrade, and the shorter the useful life will be.