What does silicon have to do with solar energy?
Question:
Answer:
Silicon is the stuff ot which most photovoltaic cells are made.
When energy is added to pure silicon, for example in the form of heat, it can cause a few electrons to break free of their bonds and leave their atoms. A hole is left behind in each case where an electron could bond. These electrons then wander randomly around the crystalline lattice looking for another hole to fall into. These electrons are called free carriers, and can carry electrical current. There are so few of them in pure silicon, however, that they aren't very useful.
Our impure silicon with phosphorous atoms mixed in is a different story. It turns out that it takes a lot less energy to knock loose one of our "extra" phosphorous electrons because they aren't tied up in a bond - their neighbours aren't holding them back. As a result, most of these electrons do break free, and we have a lot more free carriers than we would have in pure silicon.
The process of adding impurities on purpose is called doping, and when doped with phosphorous, the resulting silicon is called n-type (n for negative) because of the prevalence of free electrons. N-type doped silicon is a much better conductor than pure silicon is.
Actually, only part of our cell is n-type. The other part is doped with boron, which has only 3 electrons in its outer shell instead of 4, to become p-type silicon. Instead of having free electrons, p-type silicon (p for positive) has free holes. Holes really are just the absence of electrons, so they carry the opposite (positive) charge. They move around just like electrons do.
There is a specally designed p-n junction called photovoltaic cell.
It is a p-n junction in which the potential barrier between the p-n regons is used to drive a current through external circuit when light is incident on the junction.
Silicon is used in the makings. A single silicon photovoltaic cell, as you can imagine would produce a current of a few mA, & a small voltage of 0.6 V. Thus in roder to obtain greater power, series parallel arays of thousands of such cells are used. They are caled photovoltaic panels & are used in satellite & space stations to convert solar energy into electrical energy.
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