Photons to Electrons
How do solar/photovoltaic cells convert
photons into electrons?
The short answer is that photovoltaic ("PV") cells do not "convert" photos
PV cells are made of a semiconductor (typically silicon). When a photon of
sufficient energy strikes the PV cell, it is absorbed and its energy "knocks"
an loose electron from one of the silicon atoms, allowing it to flow freely.
The internal construction of the PV cell is like a diode, in that there is a
layer of "p" type silicon (that has a deficiency of electrons), sandwiched
against a layer of "n" type material (that has an excess of electrons). Because
of this construction, when an electron is knocked loose from the "n" type
layer, it tends to flow in only one direction out the wire attached to this
layer, then through an external circuit to do useful work, and back again
into a wire connected to the "p" layer.
So a photon is not "morph" into an electron. Photons simply provide the energy
needed to start an electric current flowing within the PV cell.
Photocells do not actually convert the Photons into Electrons, rather, they use
the Photons to move the electrons around.
They are made primarily of a pair of semi-conductors, with slightly different
electrical characteristics. (Called P-Doped and N-Doped, for Positive and
Negative) When Photons strike the molecules of the semi-conductors, electrons
are shifted in their orbits, sometimes to the other side. These electrons
moving from one side to the other are what generates the electric potential, or
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Update: June 2012