Tuesday, June 14, 2011

Solar Cells

Solar cells are in fact large area semiconductor diodes. Due to photo voltaic effect energy of light (energy of photons) converts into electrical current. At p-n junction, an electric field is built up which leads to the separation of the charge carriers (electrons and holes). At incidence of photon stream onto semiconductor material the electrons are released, if the energy of photons is sufficient. Contact to a solar cell is realized due to metal contacts. If the circuit is closed, meaning an electrical load is connected, then direct current flows. The energy of photons comes in "packages" which are called quants. The energy of each quantum depends on the wavelength of the visible light or electromagnetic waves. The electrons are released, however, the electric current flows only if the energy of each quantum is greater than WL - WV (boundaries of valence and conductive bands).

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