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How solar (photovoltaic) cells work



A solar-powered lamppost
A solar-powered lamppost

Solar cells, also known as photovoltaic cells, convert sunlight into electricity (photo = light, voltaic = electricity).

Originally, photovoltaic cells were developed for use in space and were too costly for wider use.

Researchers have found ways to manufacture cheaper and more efficient photovoltaic cells and they are rapidly becoming a widely used form of renewable energy with many applications.


Make up of a photovoltaic cell

A photovoltaic cell consists of two thin sheets of a semiconductor, usually silicon. Photons from the sun striking the silicon are absorbed by the sheet and cause some electrons to be freed. "Doping", a process of adding impurities to the silicon, is used to increase the activity of free electrons.

Doping with phosphorous causes the sheet to become negatively charged. This sheet of silicon is called N-type ("n" for negative). N-type doped silicon is a much better conductor than pure silicon.

Doping with boron creates P-type, positively charged, silicon. Instead of having free electrons, P-type silicon has a shortage of electrons, or "holes", in its outer shell.

When the two thin sheets of silicon are sandwiched together, an electric field is established between them. If a conductive pathway is introduced close to the electric field, there is an increase in the electric activity between the plates and some electrons cause a current to flow through the conductor pathway.

Diagram of how a photovoltaic cell processes sunlight.
How a photovoltaic cell processes sunlight.
Source: Image courtesy of RISE http://rise.org.au

Learn more about how solar cells work http://wwwphys.murdoch.edu.au/rise/reslab/resfiles/pv/index.html.

Diagram of a cross-section of a photovoltaic cell
Cross-section view of a photovoltaic cell.
Source: Image from How Stuff Works http://science.howstuffworks.com/solar-cell7.htm

An antireflective coating is applied to the cell to promote more absorption of sunlight through the shiny silicon. The cell is finished with a glass cover and positive and negative terminals on the back.

How the cells work

When sunlight passes through the silicon sheets in the photovoltaic cell, photons from the sunlight are absorbed. The energy of the photons is transferred to the semiconductor, knocking loose free electrons. Electricity is produced.

As more photovoltaic cells are connected together, the voltage of the electricity produced increases. Solar energy panels combine many cells to generate the electrical energy required for homes or devices. Where larger amounts of electricity are required, panels are linked together in arrays.

The possibility of being able to supply reliable electricity isolated from a distribution grid leads to endless applications. Satellites that orbit the earth, people living or working in remote areas and sailors on yachts all use solar panels for electricity and are now able to work more efficiently.


 
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Last updated: Monday, 04 January 2010
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© Copyright 2003 – 2014, ActewAGL Retail. ABN 46 221 314841
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