Charles Fritts (1850 – 1903) was the American

inventor An invention is a unique or novel device, method, composition, idea or process. An invention may be an improvement upon a machine, product, or process for increasing efficiency or lowering cost. It may also be an entirely new concept. If an ...

credited with creating the first working

selenium cell A copper indium gallium selenide solar cell (or CIGS cell, sometimes CI(G)S or CIS cell) is a thin-film solar cell used to convert sunlight into electric power. It is manufactured by depositing a thin layer of copper indium gallium selenide soluti ...

in 1883. The world's first rooftop

solar array A photovoltaic system, also PV system or solar power system, is an electric power system designed to supply usable solar power by means of photovoltaics. It consists of an arrangement of several components, including solar panels to absorb and ...

, using Fritts' selenium cells, was installed in 1884 on a New York City rooftop. Fritts coated the

semiconductor A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way ...

material

selenium Selenium is a chemical element with the symbol Se and atomic number 34. It is a nonmetal (more rarely considered a metalloid) with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium, ...

with an extremely thin layer of gold. The resulting cells had a conversion

electrical efficiency The efficiency of a system in electronics and electrical engineering is defined as useful power output divided by the total electrical power consumed (a vulgar fraction, fractional Expression (mathematics), expression), typically denoted by the Gr ...

of only about 1% owing to the properties of selenium, which in combination with the material's high cost prevented the use of such cells for energy supply. Selenium cells found other applications however, for example as light sensors for exposure timing in photo cameras, where they were common well into the 1960s. Solar cells later became practical for power uses after Russell Ohl's 1941 development of silicon P/N junction cells that reached efficiencies above 5% by the 1950s/1960s. By 2006, the best silicon solar cells were over 40% efficient, with industrial average over 17%.

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