Solar cells convert light energy into electrical energy using the photovoltaic effect. They have increased in efficiency over time from initial efficiencies of 4-6% to over 50% efficiency now. There are three generations of solar cells: first generation use crystalline silicon, second generation use thin-film technologies like cadmium telluride and copper indium gallium selenide, and third generation are emerging technologies using organic materials. Solar cells work by using differently doped semiconductor materials to create a p-n junction, where photons create electron-hole pairs that generate voltage.

2. 
 Solar cell is a photovoltaic device that converts the light
energy into electrical energy based on the principles of
photovoltaic effect.
 Albert Einstein was awarded the Nobel Prize in 1921 in
physics for his research on the photoelectric effect—a
phenomenon central to the generation of electricity
through solar cells.
 In the early stages, the solar cell was developed only with
4 to 6 % efficiency( because of inadequate materials and
problems in focusing the solar radiations). But, after 1989,
the solar cells with more than 50% efficiency was
developed.
What is a solar cell?

3. 
 First generation solar cells are made of crystalline silicon,
also called, conventional, traditional, wafer-based solar
cells and include monocrystalline (mono-Si) and
polycrystalline (multi-Si) semiconducting materials.
 Second generation solar cells or panels are based on thin-
film technology and are of commercially significant
importance. These include CdTe, CIGS and amorphous
silicon.
 Third generation solar cells are often labeled as emerging
technologies with little market significance and include a
large range of substances, mostly organic, often using
organometallic compounds.
Generation growth of
solar cells

5. Over 95% of all the solar cells produced worldwide are composed of the
semiconductor material Silicon (Si). As the second most abundant
element in earth`s crust, silicon has the advantage, of being available in
sufficient quantities.
To produce a solar cell, the semiconductor is contaminated or "doped".
"Doping" is the intentional introduction of chemical elements into the
semiconductor.
By doing this, depending upon the type of dopant, one can obtain a
surplus of either positive charge carriers (called p-conducting
semiconductor layer) or negative charge carriers (called n-conducting
semiconductor layer).
Production of solar cells

6. • If two differently contaminated semiconductor layers are
combined, then a so-called p-n-junction results on the
boundary of the layers.
• By doping a trivalent element, we get p-type semiconductor.
(with excess amount of hole)
• By doping a pentavalent element, we get n-type
semiconductor ( with excess amount of electron)
n-type semiconductor
p- type semiconductor
p-n junction layer

7. Photovoltaic Effect
Definition:
The generation of
voltage across the
PN junction in a
semiconductor due
to the absorption of
light radiation is
called photovoltaic
effect. The Devices
based on this effect
are called
photovoltaic devices.
Light
energy
n-type semiconductor
p- type semiconductor
Electrica
l Power
p-n junction

10. Electron-Hole formation
O Photovoltaic energy conversion relies on
the number of photons strikes on the
earth. (photon is a flux of light particles)
O On a clear day, about 4.4 x 1017 photons
strike a square centimeter of the Earth's
surface every second.
O Only some of these photons - those with
energy in excess of the band gap - can be
converted into electricity by the solar cell.

11. hole
Valence band
Conduction band
electron
• When such photon enters the semiconductor, it may be
absorbed and promote an electron from the valence band to
the conduction band.
• Therefore, a vacant is created in the valence band and it is
called hole.
• Now, the electron in the conduction band and hole in
valence band combine together and forms electron-hole pairs.

12. N-type
P-type
Single Solar cell

14. •Materials for Solar cell
•Solar cells are composed of various semiconducting
materials like
1. Amorphous/Crystalline silicon
2. Cadmium telluride
3. Copper indium diselenide
4. Gallium arsenide
5. Indium phosphide
6. Zinc sulphide
•Note: Semiconductors are materials, which become
electrically conductive when supplied with light or heat, but
which operate as insulators at low temperatures.

15. Amorphous Silicon cell

16. Crystalline Silicon cell

18. PV array made of cadmium telluride (CdTe) solar panels

19. Topaz solar farm, California Valley

21. CIGS Solar cell

23. GaAs solar cell

24. The structure of an MJ solar cell. There are six important types of layers: p-n junctions,
back surface field (BSF) layers, window layers, tunnel junctions, anti-reflective coating
and metallic contacts. (b) Graph of spectral irradiance E vs. wavelength λ over the AM
1.5 solar spectrum, together with the maximum electricity conversion efficiency for
every junction as a function of the wavelength

29. Solar pumps are used for water supply.
Domestic power supply for appliances include
refrigeration, washing machine, television and lighting
Ocean navigation aids: Number of lighthouses and
most buoys are powered by solar cells
Telecommunication systems: radio transceivers on
mountain tops, or telephone boxes in the country can
often be solar powered
Electric power generation in space: To providing
electrical power to satellites in an orbit around the Earth

30. Thanks for your kind
attention!