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Q: What is a solar photovoltaic cell?
A solar cell is a small semiconductor element that converts sunlight into electricity. Each cell is made of silicon or another semi-conductor material, like a computer chip. The silicon is treated so that it generates a flow of electricity when light shines on it. A thin layer of semiconductor materials exhibit the photoelectric effect, such as silicon or cadmium telluride. The layers contain small amounts of doping agents (intentional impurities), such as the element germanium. The additives give the semiconductor the ability to produce a current when exposed to light.
Consumer solar cells convert about five to twenty five percent of the solar energy they receive into electricity. Military and NASA produce a higher grade solar cell that can product up to 45% of the suns energy into electricity. Solar cells are solid-state devices in which photons collide with atoms. This process transforms the resulting energy into electrons. These electrons flow into wires connected to the cell, thus providing electric current to appliances, lighting systems or other electrical loads. A typical PV cell is a thin 3"x3”, producing only a small amount of electricity.
Sunlight is composed of particles of energy called photons. When sunlight strikes a PV material, photons will either pass through, be reflected, or be absorbed. If the photon is absorbed, its energy will be transferred to an electron in an atom of the PV material. With new energy, the electron is able to escape from its normal position in orbit around that atom. In this way, the electron can become part of, and augment, the current in an electrical circuit. This photovoltaic effect is the basic physical process through which sunlight is converted into electricity.