This document discusses the history and technology of LED lighting. It begins with the early sources of light from the sun and fire, through the invention of the light bulb. In the late 20th century, Shuji Nakamura invented the first blue and white LEDs, starting an LED revolution. The document then explains what an LED is - a semiconductor p-n junction that emits light when forward biased. Different semiconductor materials are used to produce light across the UV/visible/IR spectrum. Key materials for red, yellow, green and blue LEDs are gallium arsenide, gallium phosphide, and gallium nitride. The green LED was an important innovation for which Shuji Nakamura received

1. ABHISHEK KUMAR
2011EEC87

2. GREEN LED
HOPE FOR A GREEN FUTURE
THE FUTURE OF LIGHTING IS LED

3. 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

4. WHAT IS LED?
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.

5. 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
CANDIDATE MATERIALS
Materials with refractive Readily doped n or p-types
index that could allow light
to ‘get out’

6. QUESTION 1
Indicate the binary
compounds that can be
selected for red, yellow,
green and blue LED.

7. CANDIDATE MATERIALS
GROUP III-V & GROUP II-VI
Group II Group III Group IV Group V
iii iv v
ii
Al
Ga
In
N
P
As
Periodic Table to show group III-V and II-V binaries

8. GROUP III-V LED MATERIALS
Al
Ga
In
N
P
As
AlN, AlP,AlAs
GaN, GaP, GaAs
InN, InP, InAs
GaAs
GaP
GaAl
GaAsP
GaAsAl
Binary
compounds
Ternary
compounds
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?

9. 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.

10. GREEN LED(NOBEL PRIZE WINNER-2014)

11. 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

12. 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

13. FUTURE SCOPE
 REDUCING ENERGY CONSUMPTION
 INCREASING AREAS OF APPLICATIONS
 PROVIDING EACH AND EVERYONE IN
THIS PLANET WITH THE GIFT OF
ELECTRICITY.

14. TRUE WORDS INDEED
“Engineers like to solve
problems. If there are no
problems handily avialable,
they will create their own
problems.”