A light-emitting diode (LED) is a semiconductor light source. LEDs are used as indicator lamps in many devices and are increasingly used for general lighting. Appearing as practical electronic components in 1962, 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. LEDs have 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, automotive lighting, advertising, general lighting, and traffic signals.
Governments around the world have passed measures to phase out incandescent light bulbs for general lighting in favor of more energy-efficient lighting alternatives. Phase-out regulations effectively ban the manufacture, importation or sale of incandescent light bulbs for general lighting.
Global phase-out schedule of incandescent light bulbs:
Australia：Disallow most sales of Ban the production of incandescent light bulbs by 2009 and ban the use of incandescent light bulbs by 2010.
European Union：All member states of the EU agreed to a progressive phase-out of incandescent light bulbs by 2012.
Canada：On 31 December 2014 the import of 40- and 60-watt bulbs will be banned.
Taiwan：Taiwan banned production and, imports of incandescent lighting starting from 2012.
USA：America started to phase out traditional 100-watt incandescent light on Jan. 1, 2012.
Japan：Japan banned production and, imports of incandescent lighting starting from 2012.
Korea：Korea banned production, and imports of incandescent lighting starting from 2014.
China：China banned imports and sales of certain incandescent light bulbs started starting from October 2012.