1. Light Emitting Diode
DEPARTMENT OF PHYSICS
DR. SHYAMA PRASAD MUKHERJEE UNIVERSITY
(D.S.P.M.U) RANCHI
Bachelor of Science(Physics) sem-6
Presented by:
Pratik Bando
Premjeet kumar
Ritik Munda

2.  INTRODUCTION
 CONSTRUCTION
 WORKING
 TYPES
 APPLICATION
 ADVANTAGES & DISADVANTAGES
 CONCLUSION
Content

3. INTRODUCTION
 LED is an acronym for Light Emitting Diode
 It is a P-N junction diode
 Which emits light when activated by a suitable voltage is applied to the
leads.
 the red led light was the first led of visible light
developed in 1962 by Nick Holonyack jr. He used
GaAsP(gallium arsenide Phosphide) on a GaAs
substrate. general electric(Syracus,New york).

4. Nobel prize winner 2014
For the invention of efficient blue light emitting diode which has enable
bright & energy saving white light source
INTRODUCTION

5. Construction of LED
• A layer of P-type semiconductor material is placed
above the N-type semiconductor layer. A metal film is
used on the P-type layer to provide anode connection
to the device. Similarly, a gold-film is formed on the
N-type layer to provide cathode connection

6. Working of LED
 LED is basically a P-N junction diode
 the P side contains excess positive charge. ("holes," indicating the absence of
electrons)
 the N side contains excess negative charge (electrons).
 When p-n type semiconductor is join a junction is form called p-n junction.
 Depletion region is develop across the junction.

7. Biasing of LED
 When negative end of battery is connected with N type layer and positive
is connected with P type layer electron and hole start moving and
depletion region disappears.
Working of LED

8. Electroluminisence
 When current flows across a diode.
Negative electron moves one way and
positive holes moves another way.
 The holes exist at a lower energy level
than the free electron
 Therefore when free electron falls it losses energy
 This energy is emitted in a form of photon Which cause
light
 The color of the light is determined by the fall of the
electron and hence energy level of the photon
Working of LED

9. Types of LED
 Traditional Inorganic LEDs
 this type of LEDs manufactured from inorganic materials.
 Some of the more widely used are compound semiconductor such as
Aluminium Gallium Arsinide (AlGaAr), Gallium Arsenide Phosohide(GaArP), and
many more.
 Bi-color LED
 Two different LED emitter in one case. There are two types of these.
 One type consist of two dies connected to the same two color types of light.
 Current flows in one direction emits one colour, and current in the opposite
direction emits the other color.
Bi-color LED

10.  THROUGH-HOLE LEDS
 These are available in different shapes and sizes
 the most common ones being 3mm, 5mm and 8mm LEDs.
 These LEDs are available in different colors like Red, Blue,
Yellow, Green, White, etc.
 RGB LED
 RGB LED contains 3 LEDs on a single chip
 by using technique called PWM (Pulse Width Modulation), we
can control the output of the RGB LED to produce a wide range
of colors.
 RGB LEDs are used in Computer Cases, Motherboards, RAMs,
etc.
Through hole LED
RGB LED
Types of LED

11.  High power
 For example the CREE XP-G series archived 105
lm/w in 2009, white nichia released with a typical
efficiency of 140 lm/w.
 Organic light Emitting Diode(OLED)
 The OLED mostly used display technology computer
monitors,television,mobile phone screen etc.
 The semiconductor in an OLEd is organic which means
it contains carbon.
 The OLED uses one of the two polymer or molecules.
OLED
High power LED
Types of LED

12. Application
 Indicator and signals
 Uses of LEDs in the automotive industry is growing. With LEDs,
energy is saved and there is clearer visibility. These are
extensively used in the back and rear of an automobile for better
accessibility. LED lighting can improve the safety of pedestrians
and driver as it enhance visibility when it is ON, OFF, and dimmed
in any part of the journey.
 LED display boards are common now these days and are used
outdoors like storage signs, billboards, road signs, etc. In
signboards which has multiple languages conveying signals, the
use of more LEDs will be beneficial in terms of less power
consumption.


13.  Lighting
 LEDS are now used commonly used in all market areas from commercial
to home use : stranded lightning ,stages, theatrical, architectural and
public installation what ever artificial light is used.
Application

14.  Data communication and other signaling
 Light can be used to transmit data and signals.
 Listening devices in many theaters and similar spaces uses arrays of infrared LEDs
to sent sound to listeners and receivers
 Light Emitting Diode are used to send data over many types of fiber optics cable,
from digital audio the very high bandwidth fiber links that from the internet backbone.
Application

15. Advantages
 Efficiency: LED emit more lumen per watt than indecent light
bulbs. the efficiency of LED light fixtures is not affected by shape
and size ,unlike florescent light bulbs or tubes.
 Color:LEDs can emit light of an intended color without using any
color filters as traditional lightning methods need. Easily available
in many colors.
 Size: LEDs can be very small ,smaller than 2mm.

16. Advantages
 On/off time: LED light up very quickly. A typical red indicator LED will
achieve full brightness in under a microsecond
 Cycling: LEDs are ideal for uses subject to frequent on -off cycling unlike
indecent and fluorescent lamps that fail faster when high intensity
discharge lamps that requires a long time before restarting.
 Focus: the solid package of LED can be designed to focus its light .
Indecent and florescent source often require an internal reflectors to
collect light and direct it in a usable manner.
 .

17. Disadvantage
 High initial price: LEDs are currently more expensive,price per
lumen .
 Light quality: most cool white LEDs have spectra that differs
significantly from a black body radiator like sun or indecent light.
 Temperature dependence: driving the LED hard in high ambient
temperature may result to over heating of led package, eventually
leading to device to failure
 Voltage sensitivity
 Non reparation

18. CONCLUSION
 A light emitting diode is a solid state semiconductor device that converts
electrical power into light via the emission of photons.
 Led have many advantages in lightning today, due to their high efficiency and
longevity.
 However they are more expensive up front than incandescent and florescent
at the moment and so require additional research before completely replacing
other form of light.

19. THANK YOU