LED

What is LED?

LED or light emitting diode is an example of an Optoelectronic junction device, which implies that it is used as an electrical to optical or an optical to electrical transducer. It works on the effect of suitable voltage being applied to the diode which leads to the generation of light in the form of photons. It is implemented over a heavily doped p-n junction diode by fabricating a transparent window on top of it which allows the generated light to be emitted out of the diode.

LED

Working principle of LED

We can define a LED or light-emitting diode as a two-lead semiconductor light source. When a forward bias voltage is applied to a diode both electrons and holes move in opposite directions where they are minority carriers i.e. electrons move from n-side to p-side and holes move from p-side to n-side. Due to this movement, the equilibrium is disturbed and consequently the concentration of minority carriers at the boundary of the junction increases. Because of this excess presence of minority carriers at the boundary junction, they combine with majority carriers and this combination releases energy in the form of photons. The photons that are emitted have energy equal to or greater than the band gap energy for the diode and hence they are able to escape from it in the form of light.

The intensity of the light emitted is directly proportional to the intensity of the bias voltage being applied to the diode. However after reaching a peak value, on further increase in the bias voltage the emitted light intensity decreases. Therefore it is necessary to apply the bias in such a manner that maximum efficiency is obtained.

Uses of LED

LEDs are used in a wide variety of applications, including optical communication, alarm and security systems, remote controlled operations, robotics etc. It finds usage in many such areas because of its long lasting capability, low power requirements, swift response time and fast switching capabilities. Some common LED uses are given in the points below.

  • Used for tv backlighting
  • It is used for smartphone backlighting
  • Uses in displays
  • Used in automotive
  • LEDs used in the dimming of lights

Types of LED

There various types of LED or light-emitting diode which are made of semiconductors and are classified into different categories according to the properties of LED. Check the different types of LED given below.

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

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Practise This Question

A block of mass 'm' is hanging to a string in an elevator. The elevator is moving up with an acceleration 'a'. What will be the tension in the string?