SEMICONDUCTOR DEVICES (EC-2005)
A PRESENTATION ON LIGHT.EMITTING.DIODE
SUBMITTED TO: PROFESSOR S.N MISHRA(SCHOOL OF ELECTRONICS ENGINEERING)
SUBMITTED BY:
SUNIDHI MOHAPATRA 2028037
VIVIAN RAWADE 2028040
ABHIJIT MOHANTY 2028042
ANKIT PRASAD 2028049
ANKIT KUMAR 2028050
INTRODUCTION
Most of us are aware that the semiconductor light-emitting diode or the LED is
the major component of today’s technology. All our houses have plenty of tiny
glowing indicators provided by leds; these indicators are employed for various
aspects like reading CD and DVD disks in computer and game console drives
or to transmit signals from remote controls to electronic equipment. Cars that
are equipped with LED indicators are increasing in number these days. Most
significantly, it should be noted that LED is a crucial link between electronics
and photonics.
ELECTRICAL CHARACTERISTICS OF
LED
• Individual LEDs are low voltage devices.
• Single indicator LEDs require 2 to 4 volts of direct
current, with current in the range from 1 to 50
milliamperes.
• An illumination-grade LED containing a single
semiconducting element requires the same voltage, but
operating currents are much higher, typically several
hundred milliamperes.
• A device containing multiple elements connected series
will require higher voltage corresponding to the larger
number of individual elements in the device.
• Reverse polarity destroys an LED.
• Manufacturers provide specifications about the
maximum reverse voltages acceptable for LED V.I characteristics of led
devices; 5 volts is a typical maximum rating.
CONSTRUCTION
A Light Emitting Diode (LED) consists of three layers:
1. p-type semiconductor (intrinsic semiconductor doped with
trivalent impurities, majority charge carriers are holes)
2. n-type semiconductor (intrinsic semiconductor doped with
pentavalent impurities ,majority charge carriers are free
electrons)
3. depletion layer (region present between the p-type and n-type
semiconductor with no charge carriers present).
This creates a PN junction.
The chips are mounted in a reflecting tray order to increase the light
output.
The contacts are made on the cathode side by means of conductive
adhesive and on the anode side via gold wire to the lead frame.
The plastic case encloses the chip area of the lead frame.
The construction of an LED is similar to the normal p-n junction
diode except that gallium, phosphorus and arsenic materials are used
for construction instead of silicon or germanium materials.
WORKING
• When Light Emitting Diode (LED) is in forward biased i.e negative end of a circuit is connected to the N-type
layer and the positive end is connected with P-type layer .
• Since energy level of the holes in the Valence band is at a level much lower than the free electrons in the
Conduction band , the free electron loses its energy to come to the valence band in order to combine with
holes. This energy lost is in the form of photons ,which gives us either visible light or invisible infrared light .
• Hence the depletion region decreases and allows more charge
carriers to cross the p-n junction ,therefore causing current to
flow across the diode.
• In LEDs, the energy gap between conduction band and valence
band is very large so the free electrons in LEDs have greater
energy than the free electrons in silicon diodes. As a result, high
energy photons are released which are visible to us. While the
other diodes just produce light from the other portion of the
spectrum.
• The process of emitting light in response to the strong electric
field or flow of electric current is called electroluminescence. ENERGY BAND DIAGRAM
TYPES OF
•
LED’S
Dimmer Switches
• Color LED
• LED Tubes for Lighting
• SMD LED
• COB LED
• Graphene LED
• Traditional and Inorganic LEDs
• Maximum Brightness LEDs
• Organic LED
DIMMER
The LED is available with dimmer switches similar to other bulbs. The
SWITCHES
dimmer switch in normal incandescent bulbs doesn’t work well when
compared to dimmer switch with LED bulbs. So it is advisable to replace
standard bulbs with LED bulbs as it operates with minimum wattage than
other standard bulbs.
COLOUR LED’S
The color LED attracts every person and is available in three varieties like cool
white LED, warm white LED, daylight LED. Most of the home use halogen
bulbs which are warm white. The color in the daylight LED which has stark
white and hint blue in it which is mainly used for highlighting the real color.
LED TUBES FOR
It is implemented to substitute the fluorescent tubes and in a few cases, it can
LIGHTENING
be the single hanging replacement. The other designs require new ballast and
rewiring. It operates by offering a series of LED miniatures along the tube
length and is accessible in all the size which fits as expected.
SMD
It is expanded as a surface-mounted device and it is popular in LED
LED
lighting. The SMD chips mounted in the bulb have additional
brightness which is reliable in office and household.
COB LED
The COB stands for chip on board which is another LED generation
and offers a strong amount of light than SMD and has an accessible
option as the user considered a beam of controlling light. It serves a
better watt ration to lumen that signifies as it has high productivity.
GRAPHENE LED
The popular channel BBC charged the evolution of light comprises
LED filament shaped lined with graphene and marked as the most
available one in late 2015. It is cheaper than standard bulbs and claims
for the decrement in energy bills around 10%. The usage of graphene
was invented by a Russian scientist who was operating at Manchester
university.
Energy Efficiency and Light Emitting Compact Fluorescents Incandescent Light
Energy Costs Diodes(LEDs) Lamp(CFLs) Bulbs
Life Span(average) 50,000 hours 8,000 hours 1,200 hours
Watts of electricity used 6-8 watts 13-15watts 60watts
(equivalent to 60 watt
bulb).LEDS use less
power (watts) per unit of
light generated
(lumens). LEDs help
reduce greenhouse gas
emissions from power
plants and lower electric
bills
Kilo-watts of Electricity 329KWh/year 767KWh/year 3285KWh/year
used(30 Incandescent
Bulbs per year
equivalent
Annual Operating ₹2246.23/year ₹5241.21/year ₹22486.27/year
Cost(30 Incandescent
Bulbs per year
equivalent)
COMPARISON
LED CFL HALOGEN INCANDESCE
NT
Life Span Very Long Long Medium Short
Energy Use Very Low Low Medium High
Average Energy Up to 85% Up to 75% Up to 28% 0%
Savings
Operating Cost Very Low Low Medium High
APPLICATION OF LED
THERE ARE 3 MAIN APPLICATIONS OF LED
• indicators and signals
• lighting
• data communication and other signaling
INDICATORS AND SIGNALS
The low energy consumption, low maintenance and
small size of LEDS has LED to uses as status
indicators and displays on a variety of equipment and
installations. the are used as stadium airports and
railway stations, trains, buses, trams, and ferries etc.
LIGHTING
LEDs are now used commonly in all market areas from commercial to home use:
standard lighting, stage, theatrical, architectural, and public installations, and
wherever artificial light is used.
DATA COMMUNICATION AND OTHER
SIGNALLING
ADVANTAGE & DISADVANTAGE
ADVANTAGE DISADVANTAGE
• efficiency: leds emit more lumens per watt than • high initial price: leds are currently more expensive,
incandescent light bulbs the efficiency of led price per lumen. In 2012 the cost of per thousand
lighting fixtures is not affected by shape and size lumens was about $6. The price was expected to reach
unlike fluorescence light bulbs or tubes. in 2013 $2/kilolumen and march 2014 $1.
• color : leds can emit light of an intended color • Light quality: most cool-white leds have spectra that
without using any color filters as traditional differ significant from a black body radiator like the
lighting methods need easily available many sun or an incident light.
colors. • Temperature dependence: dividing the led hard in high
ambient temperatures may result to overheating of the
• size: leds can be very smaller than 2mm.
led package, eventually leading to device failure.
• on/off time: leds light up very quickly. A typical
red indicator led will achieve full brightness in
under a microsecond.
CONCLUSIO
N
As research continues, LEDs proved to be the best invention
so far in terms of efficiency , affordability , durability and
versatility in applications. LEDs have had a significant role in
reducing global warming by producing less to no heat and
have also proved to be sustainable and eco-friendly . New age
technology has had a major shift towards LED as a way to
light everything from Household appliances to traffic
signals .Due to its ever rising demand its safe to say that LED
has changed the lighting industry and will continue to light up
our future.
SCIENCE IS TO FIND SOMETHING UNKNOWN,
WHILE INVENTION IS TO MAKE SOMETHING
NEW OUT OF THE KNOWN THEORY. — IVAR
GIAEVER
THANK
YOU
