The document discusses solar cells, specifically photovoltaic (PV) cells, which convert sunlight into electricity using semiconductor materials like silicon. It details the functioning, efficiency, and various applications of different types of solar cells, as well as emerging technologies such as flexible and organic solar cells. The summary mentions the cost-effectiveness, sustainability, and low maintenance of solar energy sources, highlighting their increasing market value.

1. SOLAR CELL
Presenter: Damion Lawrence, M.Sc., B.Ed.
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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