LED Technology : Light Emitting Diode
A Light Emitting Diode (LED) is a two-lead semiconductor light source. It is a basic pn-junction diode, which emits light when activated. When a suitable voltage is applied to the leads, electrons are able to recombine with electron 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.
Appearing as practical electronic components in 1962,[8]
the earliest LEDs emitted low-intensity infrared light. Infrared LEDs
are still frequently used as transmitting elements in remote-control
circuits, such as those in remote controls for a wide variety of
consumer electronics. The first visible-light LEDs were also of low
intensity, and limited to red. Modern LEDs are available across the visible, ultraviolet, and infrared wavelengths, with very high brightness.
Early LEDs were often used as indicator lamps for electronic devices,
replacing small incandescent bulbs. They were soon packaged into
numeric readouts in the form of seven-segment displays, and were commonly seen in digital clocks. Recent developments in LEDs permit them to be used in environmental
and task lighting. LEDs have many advantages over incandescent light
sources including lower energy consumption, longer lifetime, improved
physical robustness, smaller size, and faster switching. Light-emitting
diodes are now used in applications as diverse as aviation lighting, automotive headlamps, advertising, general lighting, traffic signals,
and camera flashes. However, LEDs powerful enough for room lighting are
still relatively expensive, and require more precise current and heat
management than compact fluorescent lamp sources of comparable output.
LEDs have allowed new text, video displays, and sensors to be
developed, while their high switching rates are also useful in advanced
communications technology. On October 7, 2014, the Nobel Prize in Physics was awarded to Isamu Akasaki, Hiroshi Amano and Shuji Nakamura
for "the invention of efficient blue light-emitting diodes which has
enabled bright and energy-saving white light sources" or, less formally,
LED lamps.
Text Source: WikiPedia
