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How does a solar cell work?














A solar cell is a specially made photodiode. A process analogous to that happens inside a photodiode, i.e. when visible light is allowed to fall on the p-n junction of a silicon diode bonds in the depletion range break and releases free electrons and holes, happens in the solar cell.














(Photo credit: specmat.com)


These carriers produced ,in the junction of a diode that is not biased by a external potential, gets dragged either ways due to the potential barrier across the junction and the electric field created by this region.

Electrons get dragged to the n side and the holes get dragged to the p side. This leads for an additional potential difference across the junction.









(Photo credit: www.suryaurza.com)


This voltage is called the photovoltage and this process is called the photovoltaic effect.

In this process the electrons that migrated to the n side and the holes that migrated to the p side become the major carriers.

An open circuit voltage (VOC) of 0.6 V and a short circuit current (ISC) in the range 30 mA - 50 mA can be obtained from the solar cell under intense solar radiation.

These solar cells are built such that the n region of the cell is thin and the junction has the maximum area. This allows a maximum radiation gain from sunlight to the cell.















(Photo credit : solarserver.com)


To send the electrons  collected during the above process and to accumulate the electrons from the outer circuit, electrode systems should be used.



















(Photo credit: www.solarcell.net.in)

By connecting these solar cells either in series or in parallel, solar panels can be created.














(Photo credit: ecogreenroofs.co.uk)

However, these solar panels are expensive as the semiconductor used to make them is the single crystal silicon. Present researches prove that other compounds, such as polycrystalline silicon, GaAs, InP can be economical alternatives to the use of single crystal silicon.


















(Photo credit: encyclobeamia.solarbotics.net)


Researches also estimate that in the next 20 years, solar cells would be sufficient to provide 10% of the expected energy demand in the world.













(Photo credit: www.treehugger.com)

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