Solar Cells

today are mostly made of silicon, one of the most common
elements on Earth. The crystalline silicon solar cell was one of the first
types to be developed and it is still the most common type in use today.
They do not pollute the atmosphere and they leave behind no harmful waste
products. Photovoltaic cells work effectively even in cloudy weather and
unlike solar heaters, are more efficient at low temperatures. They do their
job silently and there are no moving parts to wear out. It is no wonder
that one marvels on how such a device would function.
To understand how a solar cell works, it is necessary to go back to
some basic atomic concepts. In the simplest model of the atom, ...

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but in
insulators and semiconductors there is an "energy gap", in which no
electron orbits can exist, between the inner valence band and outer
conduction band [Book 1]. Valence electrons help to bind together the atoms
in a solid by orbiting 2 adjacent nucleii, while conduction electrons,
being less closely bound to the nucleii, are free to move in response to an
applied voltage or electric field. The fewer conduction electrons there are,
the higher the electrical resistivity of the material.
In semiconductors, the materials from which solar sells are made, the
energy gap Eg is fairly small. Because of this, electrons in the valence
band can easily be made to jump to the conduction band by the injection of
energy, either in the form of heat or light [Book 4]. This explains why the
high resistivity of semiconductors decreases as the temperature is raised
or the material illuminated. The excitation of valence electrons to the
conduction band is best accomplished when the ...

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Solar Cells. (2007, February 2). Retrieved October 20, 2018, from
"Solar Cells.", 2 Feb. 2007. Web. 20 Oct. 2018. <>
"Solar Cells." February 2, 2007. Accessed October 20, 2018.
"Solar Cells." February 2, 2007. Accessed October 20, 2018.
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Added: 2/2/2007 03:10:58 AM
Category: Science & Nature
Type: Premium Paper
Words: 1165
Pages: 5

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