(LEDs) or Light-Emitting Diodes
A light-emitting diode (LED) is a specially made p-n junction diode (gallium arsenide phosphide (GaAsP) in which when current is made to flow in the forward direction, visible light is emitted from the region of the depletion layer.
The branch of science that deals with combines optics and electronics i.e. Optoelectronics
LED is a diode that will give off visible light when it is energized. In any forward-biased LED, free electrons cross the p-n junction and fall into holes and recombination takes place. As these electrons fall from a higher to a lower energy level, they radiate energy in the form of photons. In p-n junctions diode, some of this energy will be released as heat and some in the form of photons.
In LED there is an effect refer as electroluminescence, in this energy is radiated as light.
Photons with energy hv =Eg are emitted.
- Lower energy consumption i.e. voltage (1 to 2V) and currents (5 to 10 mA).
- Smaller size, faster switching.
- Longer lifetime, even more than 15 years.
- No heating issue.
- Available in different colors.
- LEDs are used in self-luminous seven-segment alpha-numeric displays of calculators and digital clocks and meters, signages, etc.
- They are rapidly replacing cathode ray tubes in solid-state video displays.
- Due to power consumption LEDs are used in traffic signals, handheld torches, and various indicator lamps in light motor vehicles and two-wheelers.
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