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Name: Katerina 
Status: student 
Grade: 9-12 
Location: WI 
Country: USA 



Question:
How do solar/photovoltaic cells convert photons into electrons?


Replies:
Hi Katerina,

The short answer is that photovoltaic ("PV") cells do not "convert" photos into electrons.

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.

Regards,
Bob Wilson


Katerina,

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 voltage.

Ryan Belscamper



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