1. A photodiode is a type of photo detector capable of converting light into current.
It converts light energy into electrical energy.
Photodiodes are similar to regular semiconductor diodes except that they may be either exposed with a window or optical fibre to allow light to reach sensitive part of device

2. Material commonly used for producing photodiode includes:

3. Working of Photodiode Photodiodes are of two types PN and PIN.
At PN junction there will be concentration gradient that causes electrons to diffuse into p-type region and holes into n-type region. This diffusion results in an opposing electric potential, often referred to as an Depletion region.
Any photon absorbed in the depletion region causes moment of charge carriers

4. This moment of charge carriers across the junction upsets the electrical balance and produces a photocurrent, which can be detected at electrodes.

6. In electronic devices In smoke detectors
Applications
In electronic devices In smoke detectors
Light sensors
Used to measurer light intensity in science and industry

7. Semiconductors bring quality to light!
What is LED?
Semiconductors bring quality
to light!
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.

8. Applications of LEDs

9. Your fancy telephone, i-pod, palm pilot and digital camera

10. Getting to know LED Advantages of Light Emitting Diodes (LEDs)
Longevity: The light emitting element in a diode is a small conductor chip rather than a filament which greatly extends the diode’s life in comparison to an incandescent bulb ( hours life time compared to ~1000 hours for incandescence light bulb)
Efficiency: Diodes emit almost no heat and run at very low ampere.

11. How does it work? Recombination produces light!!
P-n junction
Electrical Contacts
A typical LED needs a p-n junction
There are a lot of electrons and holes at the junction due to excitations
Electrons from n need to be injected to p to promote recombination
Recombination produces light!!
Junction is biased to produce even more e-h and to inject electrons from n to p for recombination to happen

12. Thank you