Solar cells convert sunlight directly into electricity through a process where photons knock electrons loose from semiconductor materials like silicon. The electrons then flow as a current that can be drawn off the top and bottom contacts of the solar cell to be used as power. Solar cells provide renewable and sustainable power for applications from small electronics to large solar panel arrays. They are particularly useful for powering remote devices without access to electricity grids. The most efficient solar cells are made from single crystalline silicon, with efficiencies up to 25%, while thin film technologies continue advancing toward flexible solar cells and improved efficiency.

1. Solar Cells
&
Its Applications

2. The Solar Cell
• The most common type of solar cells are Photovoltaic
Cells (PV cells)
• Converts sunlight directly into electricity
• Cells are made of a semiconductor material (eg. silicon)
• Light strikes the PV cell, and a certain portion is
absorbed
• The light energy (in the form of photons) knocks
electrons loose, allowing them to flow freely, forming a
current
• Metal contacts on the top and bottom of PV cell draws
off the current to use externally as power

3. Why Use Solar Cells?
• Low maintenance, long lasting sources of energy
• Provides cost-effective power supplies for people
remote from the main electricity grid
• Non-polluting and silent sources of electricity
• Convenient and flexible source of small amounts
of power
• Renewable and sustainable power, as a means to
reduce global warming
• In 2002, the global market for photovoltaic panels
and equipment was valued at 3.5 billion dollars

4. The Single Crystalline Silicon
Solar Cell
• Pure silicon is a poor
conductor of electricity
• “Doping” of silicon with
phosphorus and boron is
necessary to create n-type
and p-type regions
• This allows presence of
free electrons and electron-
free ‘holes’
• The p-n junction generates
an electric field that acts
as a diode, pushing
electrons to flow from the
P side to the N side

5. The Solar Cell

6. When Light Hits the Cell
• Light energy (photons) ionizes the atoms in the
silicon and the internal field produced by the
junction separates some of the positive charges
(holes) from the negative charges (electrons)
• The holes are swept into the p-layer and the
electrons are swept into the n-layer
• The charges can only recombine by passing
through an external circuit outside the material
• Power is produced since the free electrons have to
pass through the load to recombine with the
positive holes

7. Efficiency of Solar Cells
• The amount of power available from a PV device
is determined by
– Type and area of the material
– The intensity of the sunlight
– The wavelength of the sunlight
• Single crystalline solar cells  25% efficency
• Polycrystalline silicon solar cells  less than
20%
• Amorphous silicon solar cells  less than 10%
• Cells are connected in series to form a panel to
provide larger voltages and an increased current

8. Arrays and Systems
• Panels of solar cells can be linked together
to form a larger system – an array
(a) a PV panel array, ranging from two to
many hundreds of panels;
(b) a control panel, to regulate the power
from the panels;
(c) a power storage system, generally
comprising of a number of specially
designed batteries;
(d) an inverter, for converting the DC to
AC power (eg 240 V AC)
(e) backup power supplies such as diesel
startup generators (optional)
(f) framework and housing for the system
(g) trackers and sensors (optional);

9. Solar Cells are used in a wide
variety of applications
• Toys, watches, calculators
• Electric fences
• Remote lighting systems
• Water pumping
• Water treatment
• Emergency power
• Portable power supplies
• Satellites

10. Future Applications
• Looks like denim
• Can be draped over any
shape
• No rigid, silicon base
• Made of thousands of
flexible, inexpensive solar
beads between two layers of
aluminum foil
• Each bead functions as a tiny
solar cell
The Flexible Solar Cell

11. Future Applications
• Based on photosynthesis in plants
• Use of light-sensitive dyes
• Cost of manufacture is decreased by
60%
Organic Solar Cells
New Alloys
• Indium, gallium, and Nitrogen
• Converts full spectrum of sunlight from
near-infrared to far-ultraviolet

12. Future Applications
• Tiny rods are embedded
in a semi-conducting
plastic layer sandwiched
between two electrodes
• Rods act like wires,
absorbing light to create
an electric current
Nano Solar Cells
Tetrapod Nanocrystals
• May double the efficiency of plastic solar cells
• Made of cadmium, tellurium

13. Thankyouall…!!!
hareesh kumar