Zener diodes conduct current similarly to normal diodes when forward biased but will conduct in the reverse direction once a breakdown voltage is reached, making them useful for voltage regulation. Photodiodes conduct current when light hits their photoactive surface and generates electron-hole pairs, while LEDs emit photons when an external current passes through. Solar cells work like photodiodes, using photons to energize electrons in silicon and allow current conduction, generating electricity from light.

1. TYPES OF DIODES
AND
SOLAR CELL
SHALET K S
Asst. Prof

2. ANODE CATHODE
ZENER DIODE

3. Symbolic Representation

4. OPERATION
When forward biased the
Zener diode will work like
a normal diode. It
conducts a lot of forward
current.
When reverse biased, the zener
diode will not conduct till a certain
break down voltage but will conduct
well after the break down voltage is
reached, making it a good regulator
device.
+ -

5. PHOTO DIODE

6. SYMBOL

7. OPERATION
When the light falls on the photodiode, depending
on the intensity of light the amount of photons
projected in the photo active surface of the will form
Electron Hole pairs and will allow the diode to
conduct the external current.

8. LED (Light emitting Diode )

9. REPRESENTATION AND TERMINALS

10. OPERATION
The operation of LED is exactly the opposite to that
of photo diode. In photo diode the external current
will conduct after the diode is exposed to Photons,
where as in an LED the Photons are released when
an external current flows through the diode.

11. SOLAR CELL

12. Representation and Working
The working of a solar cell is very much similar to that of a
photo diode. It all depends on the principle of photons and energy. As
the light hits the Glass and metal contacts on the top of the solar cell the
photons will energize the N doped silicon and will allow the excited
electrons to conduct.