BLUE LED-THE STUNNINGGG LAMPS.....

3. A brief intro to the luminous world of LEDs…
• LED – Light Emitting Diode
• A two lead semi-conductor light source
• A basic PN junction diode
• Colours available : Blue Green and Red
• Working principle : Electroluminescence
• Applications : Wide variety of applications in electronics
and illumination engineering

4. LEDs and the colour Blue
• Gallium nitride (GaN), which is the material used to create blue
LEDs, is hard to grow.
• GaN is a wide band gap semi-conductor.
• Blue is one of the basic colours necessary
to make White light.
• Oct-7 2014, Nobel prize was awarded to
the inventors for their illusive contribution
to the world of light .

5. LEDs came a long way…
• 1907 – Discovered electroluminescence – HJ Round
• 1927 – Created first LED – Oleg Losev
• 1955 – Infrared emission from GaAs – Rubin Braunstein
• 1962 – First visible spectrum (Red) LED – Nick Holonyak
• 1972 – Yellow LED – M. George
• 1972 – First blue-Violet LED – Herb Maruska and Wally Rhines
• 1994 – First high brightness blue LED (InGaN) – Shuji Nakamura
• 1995 – P-Type doping of GaN – Isamu Akasaki & Hiroshi Amano
• 2014 – Nobel Prize in Physics for the invention of blue LED - Isamu Akasaki Hiroshi Amano & Shuji Nakamura
• 2014 – 5 of us just stepped into these footsteps

6. Hiroshi Amano Shuji Nakamura
The Genius behind the Blue LED…
Isamu Akasaki

7. Principle…
• LEDs create light by electroluminescence in a semiconductor material
• Electroluminescence - optical phenomenon and electrical phenomenon in which a material
emits light in response to the passage of an electric current or to a strong electric field.
• the result of radiative recombination of electrons and holes in a material, usually a
semiconductor.
• the electron-hole recombination process produces some photons in the IR or visible.
• The junction in LED is forward biased.

8. Working…
• Consists of p-n junction diode dopped with Gan/InGaN
• Current flows from p-side to n-side not in reverse
• Charge carriers electrons and holes-flow into junction with different voltage
• When electrons meet holes at junction
• Then it falls into lower energy level and release energy in the form of light

9. • colour of LED based on band gap energy
• Materials for led have direct band with energy corresponding to IR-UV region

10. • Advantages • Disadvantages
• Blue LEDs are environment friendly.
• Small, durable and need little power.
• Operate at a safe and low voltage
• Require less energy to provide light.
• A blue LED is necessary to make a white
LED
• LEDs also last up to 100,000 hours,
compared to 10,000 hours for
fluorescent lights and 1,000 hours for
incandescent bulbs.
• High life time –slow failure
• Very difficult to produce than other LEDs
• High initial price
• Blue hazard-can damage eye
• Blue pollution-cause light pollution
• Voltage sensitivity-should supply with
the voltage above the threshold and a
current below the rating
• Electrical polarity- only light with correct
electrical polarity.

11. APPLICATION
• Used in flat screens and data storage.
• Used in accent Lighting fixtures
• It has been used to kill harmful bacteria that can cause dental and skin problems.
• Used to make white LEDs.
• Used in sterilization and hygiene.
• To help conducting studies of electro magnetic radiations.