Photovoltaics

The technology involved in the conversion of solar radiation to direct electric current. Photovoltaic cells have been made from amorphous silicon, polycrystalline silicon, microcrystalline silicon, cadmium telluride, and copper indium selenide/sulfide. Because each individual cell has relatively low voltage and current output, cells are usually connected in series and parallel to form arrays. Research in this field has pursued improvements in efficiency and lowering of costs. In view of the need to develop alternative sources of energy, use of solar cells is expanding significantly. Costs have dropped from over $100/watt in the 1970s to a reported $1.09/watt in 2011. The highest efficiency reported is over 40%.