Solar cells convert sunlight directly into electrical energy through the photovoltaic effect. They consist of layers of n-type and p-type semiconductors that form a p-n junction. When sunlight strikes the solar cell, photons are absorbed and release electrons that can be harvested as electric current. There are three main types of solar cells: monocrystalline silicon cells have the highest efficiency around 14-17%, polycrystalline silicon cells have an efficiency of 13-15%, and amorphous silicon cells have the lowest efficiency of 5-7%.

2. Definition
• Solar cell is also called as photo galvanic cell
Photo galvanic cell or solar cell is the
one which converts the solar energy (energy
obtained from the sun) directly into electrical
energy.

3. Principle
• The solar cells are based on the principles
of photovoltaic effect.

4. Photovoltaic effect
• Definition: Light
ener
• The generation of gy
voltage across the PN
junction in a
semiconductor due to the n-type semiconductor
Electri
absorption of light cal
radiation is called p- type semiconductor Power
photovoltaic effect. The
Devices based on this
effect is called p-n junction
photovoltaic device.

5. Construction
• Solar cell (crystalline Silicon) consists of a
n-type semiconductor (emitter) layer and
p-type semiconductor layer (base). The two
layers are sandwiched and hence there is
formation of p-n junction.
• The surface is coated with anti-reflection
coating to avoid the loss of incident light
energy due to reflection.

6. Construction

7. Working
• When a solar panel exposed to sunlight , the light
energies are absorbed by a semi conduction
materials.
• Due to this absorbed energy, the electrons are
liberated and produce the external DC current.
• The DC current is converted into 240-volt AC
current using an inverter for different
applications.

8. Working

9. • Thus when this p and n layers are connected to
external circuit, electrons flow from n-layer to
p-layer, an hence current is generated
• The electrons that leave the solar cell as
current give up their energy to whatever is
connected to the solar cell, and then re-enter
the solar cell. Once back in the solar cell, the
process begins again.

10. Types of Solar cell
Based on the types of crystal used, soar cells can be classified as,
1. Mono crystalline silicon cells
2. Polycrystalline silicon cells
3. Amorphous silicon cells
1. The Mono crystalline silicon cell is produced from pure
silicon (single crystal). Since the Mono crystalline
silicon is pure and defect free, the efficiency of cell will be
higher.

11. Polycrystalline solar cell
• In Polycrystalline solar cell, liquid silicon
is used as raw material and polycrystalline
silicon was obtained followed by solidification
process. The materials contain various
crystalline sizes. Hence, the efficiency of this
type of cell is less than Mono crystalline cell

12. Amorphous silicon cells
3.Amorphous silicon was obtained by
depositing silicon film on the substrate like
glass plate.
•The layer thickness amounts to less than 1µm
– the thickness of a human hair for
comparison is 50-100 µm.

13. Comparison of Types of solar cell
Material Efficiency (%)
Mono crystalline silicon 14-17
Polycrystalline silicon 13-15
Amorphous silicon 5-7

14. Advantages
1. It is clean and non-polluting
2. It is a renewable energy
3. Solar cells do not produce noise and they are totally
silent.
4. They require very little maintenance
5. They are long lasting sources of energy which can be
used almost anywhere
6. They have long life time
7. There are no fuel costs or fuel supply problems

15. Disadvantage
1. Solar power can`t be obtained in night time
2. Solar cells (or) solar panels are very expensive
3. Energy has not be stored in batteries
4. Air pollution and whether can affect the production of
electricity
5. They need large area of land to produce more efficient
power supply