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Light & PV Effect

Light

When electrons move against an electric field a ripple is created. When an element is energised, its electrons jump from their place and leave an electron hole. As the free electrons return to their place or find new holes to fill, and return to their original energy levels, the excess energy is released in a neutral form. This neutral energy is photon particles. The photons travel as waves or particles.

The photons reflect on surfaces, and this comes through as a signal into our eyes that causes a ripple in the electrons and atoms of our eyes, connected into the back of our brain by our optic nerves, sent as an electrical signal that we process as light.

An example of this would be tungsten filament in a light bulb. Alternating current (AC) electricity is passed through the filament causing it to energise. As the electrons become energised, they jump from their place. The tungsten becomes hot. The lightbulb produces an electric field and as the electrons return to their original energy levels, they shoot out photon energy. The current alternates fast enough that the light appears constant.

Photovoltaic Effect

A semiconductor is between a conductor and an insulator.

A semiconductor only conducts electricity while heated. Its electrons become free electrons. This means they leave their places and there are electron holes left over for other electrons to fill.

A lot of the science of solar is electrons, interestingly.

Far more interestingly, a question pops up. Why do solar panels produce electricity?

It may seem obvious, the panel becomes heated, and thus it is energised. Perhaps it’s not so simple.

An intrinsic semiconductor is a semiconductor material with not many impurities. It is not very conductive.

By doping, which is essentially injecting the intrinsic semiconductor material, impurities can be added.

The resulting material is known as an extrinsic semiconductor material. An extrinsic semiconductor material is highly conductive.

To put this simply, more electrons or more electron holes are added to the semiconductor material. This means that electrons can move more freely through the material.

By doping one side of a silicon wafer, literally a slice of silicon the size of a coaster, with phosphorus and one side with boron, something called a p-n junction is created. This means there is a positive side and a negative side to the extrinsic semiconductor material, silicon in this case.

This means electrons are drawn to the positive side, leaving plenty of space in the middle for holes to be filled as electricity passes through the silicon. When these holes are filled, we capture this as electricity.

So the answer to our questions about electricity passing through the extrinsic semiconductor material has been answered.

Finally we must figure out, how do solar panels convert sunlight into electricity?

The simple answer is it just does.

To put it in basic terms, the photovoltaic effect is when sunlight hits a photoconductive material, electricity is created.

When sunlight hits an extrinsic semiconductor material that is also a photoconductor, silicon in the case of home solar, heat and visible light are absorbed, electrons become free electrons, and electrons find new holes to fill, thus we capture this as electricity.

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