What is an LED? Definition, Types, Working Principle, and Uses

We all know, for a long time people used oil lamps, hurricanes to illuminate the night. At that time, the invention of the bulb gave a new direction to science. Now modern technology uses a lot of devices to generate light such as tungsten lamps, CFL, LEDs, etc. In all of them, the most efficient device to produce light is LED.

If you do not know much about it, this article is for you. Today, I am going to unlock the details of the LED. In this article, you will know -

1. What is an LED?
2. Symbol of LED
3. What are the types of LEDs?
4. How does LED work?
5. Uses of LEDs

What is an LED?

LED (light-emitting diode) is an electronic device made of semiconductors that emits light when an electric current is passed through it. The semiconductor used in LED carries a lot of electrons and holes. When current is passed through it, these electrons and holes recombine and release energy in the form of photons.

The semiconductors which are used in LEDs are made up of elements from group III and group V of the periodic table. For example gallium arsenide (GaAs) and gallium phosphide (GaP), etc.

Very popular semiconductor materials used to manufacture LEDs are:

1. Indium gallium nitride (InGaN) - Used in blue, green, and ultraviolet high-brightness LEDs
2. Aluminum gallium indium phosphide (AlGaInP) - Used in yellow, orange, and red high-brightness LEDs
3. Aluminum gallium arsenide (AlGaAs) - Used in red and infrared LEDs
4. Gallium phosphide (GaP) - Used in yellow and green LEDs

Symbol of LED

What is an LED

The symbol of the LED is similar to the symbol of the PN-junction diode. The difference between the symbol of the PN-junction diode and the symbol of the LED is that the LED only has two arrowheads and PN-junction does not have it. In LED, these two arrowheads are used to represent the emissions of light.

What are the types of LEDs?

LEDs come with different packages for different types of applications, like -

1. Miniature LED
2. High-power LED
3. AC-driven LED
4. LED's application-specific variations
a) Flashing LED
b) Bi-color LED
c) RGB Tri-color LED
d) Decorative-multicolor LED
e) Alphanumeric LED
f) Digital RGB LED
g) Filament LED
h) Chip-on-board arrays LED

How does LED work?

Light is a form of energy that is released from atoms. Light consists of many small energy packets that have momentum but no mass. In the atom, electrons move in orbit around the nucleus, and the electrons in different orbits have different amounts of energy. When electrons descend from a higher orbit to a lower one energy is released in the form of photons.

The same thing happens inside the LED. Actually, an LED is a type of PN-junction diode that uses a special type of semiconductor (such as gallium arsenide (GaAs) and gallium phosphide (GaP), etc). These special type of semiconductor is the cause to produce light.

These semiconductor used in LED carries a lot of electrons and holes. The holes in the semiconductor lie in the valence band, while the free electrons lie in the conduction band. When we apply a forward bias in the p-n junction, these electrons and holes recombine with each other and release energy in the form of photons.

If we talk about different colors of LEDs, then these different colors come from these LEDs due to the energy bandgap between the electrons and holes present in the semiconductor materials. The separation of the bands determines the energy of the photons emitted by the LED.

Different types of semiconductors have different energy bandgaps from which different types of photonic energy are emitted. These photonic energies determine the wavelength of the emitted light, and hence these different colors.

Uses of LEDs?

The quality of LED lights provides a wide range of benefits for design engineers. It provides high energy efficiency, a long life service, cold temperature operation, available in a wide range of colors, controllability, instant-on capability, No UV emissions or very little infrared, and design flexibility, etc. 

For all these qualities they are used in various fields of technology such as optical communication, alarm and security systems, remote-controlled operations, robotics, etc. These lights are also used in electronics (TV back-lighting, displays) and automotive industries.

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