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How Photovoltaic Cells Work

Energy From Nuclear Reaction

Initially, the energy a photovoltaic cell uses comes from the sun. There, hydrogen nuclei fuse with each other to form helium nuclei and energy. It takes four hydrogen nuclei to form one helium nucleus.

Fusion in the Sun

Photons

Photons are the energy byproducts of the nuclear reaction in the sun. They are essentially "packets of energy."

Photons from the Sun

Electrons Absorb Photons

When photons from the sun hit a photovoltaic cell, they may be absorbed by an electron. With this extra energy, the electron may become excited and break off its atom, and eventually begin an electric current.

Electrons Absorb Photons

Silicon Wafer

The silicon wafer is the basic starting material of photovoltaic cells. As other materials are added to both sides of the cell, the silicon remains neutral, and acts as a barrier layer. This is because of its four valence electrons.

The Silicon Wafer

Positive Layer

In a photovoltaic cell, boron is found on the bottom. This forms a positive layer. Often, silicon wafers are obtained with boron already infused into one side.

Boron: The Positive Layer

Negative Layer

In a photovoltaic cell, phosphorus is found on the top, directly on top of the silicon. The phosphorus is a dopant, which forms a negative layer on the side of the cell facing the sun.

Phosphorus: The Negative Layer

Electrons Move Into Phosphorus

The phosphorus layer, with a negative charge, can produce an electric current when the absorbed charge attempts to "spread out." Shown here is a picture of phosphorus dopant: a clear, odorous fluid.

Phosphorus Spreads Electrons

Photoelectric Effect

The photoelectric effect explains the movement of electrons in the presence of photons. This was first hypothesized in 1839, but was not fully explained until 1921, when Albert Einstein won the Nobel Prize for it.

Albert Einstein


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