ABHISHEK KUMAR

2011EEC87

GREEN LED

HOPE FOR A GREEN FUTURE

THE FUTURE OF LIGHTING IS LED

HISTORY OF LIGHTING

SUN

PLANTS IN FORM OF PHOTOSYNTHESIS

BIRTH OF FUEL LAMPS

EDISON AND OTHERS INVENTED BULBS

THAT WILL LAST FOR MAXIMUM 1500

HOURS(1880

SHUJI NAKAMURA INVENTED FIRST

BLUE AND WITH ADDITIONAL

PHOSPHOR,WHITE LED AND STARS A

LED BOOM

LED are semiconductor p-n junctions that under forward bias conditions can emit

radiation by electroluminescence in the UV, visible or infrared regions of the

electromagnetic spectrum. The qaunta of light energy released is approximately

proportional to the band gap of the semiconductor.

WHAT IS LED?

CANDIDATE MATERIALS

Direct band gap materials

e.g. GaAs not Si

UV-ED ~0.5-400nm

Eg > 3.25eV

LED - ~450-650nm

Eg = 3.1eV to 1.6eV IR-ED- ~750nm- 1nm

Eg = 1.65eV

Readily doped n or p-typesMaterials with refractive index that could allow light to ‘get out’

QUESTION 1

Indicate the binary

compounds that can be

selected for red, yellow,

green and blue LED.

CANDIDATE MATERIALS

GROUP III-V & GROUP II-VI

iviii v

ii

Periodic Table to show group III-V and II-V binaries

Group II Group III Group IV Group V

Al

Ga

In

N

P

As

GROUP III-V LED MATERIALS

Al

Ga

In

N

P

As

AlN, AlP,AlAs

GaN, GaP, GaAs

InN, InP, InAs

GaAsGaP

GaAl

GaAsP

GaAsAl

Questions to ask when choosing the right material:1. Can it be doped or not?

2. What wavelength it can emit?3. Would the material able to allow radiative

recombiation?4. Direct or indirect semiconductor?

Ternary

compounds

Binary

compounds

STOKES SHIFT

Current bright blue LEDs are based on the

wide band gap semiconductors GaN (gallium

nitride) and InGaN (indium gallium nitride).

Among the challenges being faced to

improve the efficiency of LED-based white

light sources is the development of more

efficient phosphors.

GREEN LED(NOBEL PRIZE WINNER-2014)

WHY LED IS GREEN?

A modern white LED lightblub converts more

than 50 percent of the electricity it uses into

light.

LEDs also last up to 100,000 hours,

compared to 10,000 hours for fluorescent

lights and 1,000 hours for incandescent

bulbs.

REDUCE CARBON EMISSION

WHAT MADE IT POSSIBLE?

Gallium nitride, a chemical that appears in

many of the layers in a blue LED.

The previous red and green LEDs used

gallium phosphide, which was easier to

produce.

Either by mixing the outputs of blue, red and

green LEDs, or by exciting a phosphor

material with a blue LED to generate green

and red light

FUTURE SCOPE

REDUCING ENERGY CONSUMPTION

INCREASING AREAS OF APPLICATIONS

PROVIDING EACH AND EVERYONE IN

THIS PLANET WITH THE GIFT OF

ELECTRICITY.

TRUE WORDS INDEED

“Engineers like to solve

problems. If there are no

problems handily avialable,

they will create their own

problems.”