How Does Solar Power Produce Electricity

Photovoltaic (PV) cells are the technology that is used to produce electricity from solar power. PV cells are a relatively new innovation in our use of the sun's energy that stretches back thousands of years. This article will explain how solar power produces electricity using photovoltaic cells.

PV cells are made out of a semiconductor material.  This is usually a compound of silicon. When the cell is exposed to sunlight it takes in some of the light energy. 

The incoming energy is enough to push an electron loose from the silicon atoms.  These free-floating electrons flow in the same direction in the semiconductor.  This produces an electrical current.  The next step is to use contacts that have been placed on the photovoltaic cells and run a circuit from the top contacts, through the item to be powered, and back to the bottom contacts. 

The silicon is, surprisingly, impure.  This is because silicon in its natural crystalline state does not allow for much movement of electrons.  Each of the silicon atoms is unstable on its own because there are four places for electrons that can be filled.  Yet, every silicon atom is usually locked up with the other silicon atoms by sharing electrons on the outer valance. 
 
In order to make the silicon material more conductive, it is necessary to dope it, or mix in some other substance.  To make N-type silicon, phosphorous is used.  It has five electrons in its outer ring, so that when it mates up with the silicon atoms surrounding it, there is one free electron for every phosphorous atom. 

P-type silicon is made by doping with boron.  It has only three electrons in its outer shell.  This leaves a hole, which is a place where an electron can jump in, for every atom of boron.  The key to using silicon in photovoltaic cells is to use both P-type and N-type silicon. 

The two types of silicon are set up side by side.  At first, the electrons and holes near the shared border fill in rapidly.  Then, equilibrium is reached where the electrons can no longer interact in that way. 

An electric field is created separating the two halves.  In this field, it is easy for electrons to flow from the P-side to the N-side.  Electrons on the N-side cannot make it over to the P-side.  This creates a one-way flow of electrons. 

Photons are units of energy from the sun.  Photons keep the energy flowing by bumping into the atoms of the solar cell and freeing electrons and holes.  This perpetuates the movement of electrons from hole to hole and establishes current.  The field created at the site of the N-type and P-type silicon junction makes the voltage that completes the power picture. 

The solar panels that you see on rooftops are a number of PV cells linked together in a parallel or series configuration. The number of PV cells in the panel increases the amount of electricity that will be produced. The electricity that is created is transformed from direct current to alternating current where it can be used in the home.

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