Light Emitting Diode

A light releasing diode is an electric component that emits light when the electric current flows through it. It is a light source based on semiconductors. When current passes through the LED, the electrons recombine with holes emitting light in the process. It is a specific type of diode having similar characteristics as the p-n junction diode. This means that an LED allows the flow of current in its forward direction while it blocks the flow in the reverse direction. Light-emitting diodes are built using a weak layer of heavily doped semiconductor material. Based on the semiconductor material used and the amount of doping, an LED will emit a colored light at a particular spectral wavelength when forward biased.

Working of Light Emitting Diode

The holes lie in the valence band, while the free electrons are in the conduction band. When there is a forward bias in the p-n junction, the electron which is a part of the n-type semiconductor material would overrun the p-n junction and join with the holes in the p-type semiconductor material. Therefore, regarding the holes, the free electrons would be at the higher energy bands.

The figure demonstrates the elementary process principle When this movement of free electron and hole takes place, there is a change in the energy level as the voltage drops from the conduction band to the valance band. There is a release of energy due to the motion of the electron. In standard diodes, the release of energy is in the manner of heat. But in LED the release of energy in the form of photons would emit light energy. The entire process is known as electroluminescence, and the diodes are known as a light-emitting diode.
In LED, energy discharged in light form hinges on the forbidden energy gap. One could manipulate the wavelength of the light produced. Therefore, from its wavelength, the light color and its visibility cannot be controlled. The color and wavelength of the light emitted can be determined by doping it with several impurities.

Types of LED

Miniature LEDs
High-Power LEDs
Flash LED
Bi and Tri-Colour
Red Green Blue LEDs
Alphanumeric LED
Lighting LED

Uses of LED

Used for TV back-lighting
Used in displays
Used in automotives
LEDs used in the dimming of lights