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  • Tony Pappas

Solar cell basics

Isn’t it shocking how a little chunk of silicon can produce electricity? When I asked the U.S. Government, Department of Energy, how this worked, this is what they told me:

“When light shines on a photovoltaic (PV) cell – also called a solar cell – that light may be reflected, absorbed, or pass right through the cell. The PV cell is composed of semiconductor material; the ‘semi’ means that it can conduct electricity better than an insulator but not as well as a good conductor like a metal. There are several different semiconductor materials used in PV cells.”

“When the semiconductor is exposed to light, it absorbs the light’s energy and transfers it to negatively charged particles in the

material called electrons. This extra energy allows the electrons to flow through the material as an electrical current. This current is extracted through conductive metal contacts – the grid-like lines on a solar cell – and can then be used to power your home and the rest of the electric grid.”

“The efficiency of a PV cell is simply the amount of electrical power coming out of the cell compared to the energy from the light shining on it, which indicates how effective the cell is at converting energy from one form to the other. The amount of electricity produced from PV cells depends on the characteristics (such as intensity and wavelengths) of the light available and multiple performance attributes of the cell.”

“An important property of PV semiconductors is the bandgap, which indicates what wavelengths of light the material can absorb and convert to electrical energy. If the semiconductor’s bandgap matches the wavelengths of light shining on the PV cell,then that cell can efficiently make use of all the available energy.”

“Silicon is, by far, the most common semiconductor material used in solar cells, representing approximately 95 percent of the modules sold today. It is also the second most abundant material on Earth (after oxygen) and the most common semiconductor

used in computer chips. Crystalline silicon cells are made of silicon atoms connected to one another to form a crystal lattice. This

lattice provides an organized structure that makes conversion of light into electricity more efficient.”

“Solar cells made out of silicon currently provide a combination of high efficiency, low cost, and long lifetime. Modules are expected to last for 25 years or more, still producing more than 80 percent of their original power after this time.”

You can learn more at energy.gov, Office of Energy Efficiency and Renewable Energy.

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