A diode to darkness
Unlike incandescent bulbs, light emitting diodes (LEDs) do not have a filament that is heated to create light. They are illuminated by the movement of electrons in a semiconductor material (diode). Since electricity is directly turned into light, LEDs waste less energy as heat. They also consume less energy than CFLs that use mercury vapour to produce light.
LED was first made commercially available in the US in 1960s by placing gallium, arsenic and phosphate on a silicon chip. It had low lighting efficiency and was used as an indicator. White LEDs were introduced in India for lighting five years ago. Philips, OSRAM, Cree and Nichia are the only makers of the patented LED chip. The chip is packaged into an electric component fitted with heat sinks and a lens to concentrate light in a direction. This is then made into a fixture.