Solar cells are panels that contain light sensitive materials, which, when acted upon by sunlight, cause a flow of electrons to flow, which we call electricity. The principle that causes electricity to be generated from sunlight is that sunlight is composed of photons of energy from the sun. Those photons are allowed to penetrate a desirable material, such as a sheet of silicon (which is a great semiconductor). The photons essentially "strip" the existing silicon atoms of some of their electrons and cause an electron flow, which travels is one direction only. This one direction current is called direct current, and is very useful for powering local electricical items at your house. The power that is generated and not needed immediately can be stored for later use by batteries. Solar cells may be linked together in a series circuit, but power production is maximized by utilizing parallel circuit linkage.