Photovoltaic Solar Cells

Photovoltaic solar cells are thin silicon disks that convert sunlight into electricity. These disks act as energy sources for a wide variety of uses, including: calculators and other small devices; telecommunications; rooftop panels on individual houses; and for lighting, pumping, and medical refrigeration for villages in developing countries. Solar cells in the form of large arrays are used to power satellites and, in rare cases, to provide electricity for power plants.
When research into electricity began and simple batteries were being made and studied, research into solar electricity followed amazingly quickly. As early as 1839, Antoine-Cesar Becquerel exposed a chemical battery to the sun to see it produce voltage. This first conversion of sunlight to electricity was one percent efficient. That is, one percent of the incoming sunlight was converted into electricity. Willoughby Smith in 1873 discovered that selenium was sensitive to light; in 1877 Adams and Day noted that selenium, when exposed to light, produced an electrical current. Charles Fritts, in the 1880s, also used gold-coated selenium to make the first solar cell, again only one percent efficient. Nevertheless, Fritts considered his cells to be revolutionary. He envisioned free solar energy to be a means of decentralization, predicting that solar cells would replace power plants with individually powered residences.
With Albert Einstein's explanation in 1905 of the photoelectric effect—metal absorbs energy from light and will retain that energy until too much light hits it—hope soared anew that solar electricity at higher efficiencies would become feasible. Little progress was made, however, until research into diodes and transistors yielded the knowledge necessary for Bell scientists Gordon Pearson, Darryl Chapin, and Cal Fuller to produce a silicon solar cell of four percent efficiency in 1954.
Further work brought the cell's efficiency up to 15 percent. Solar cells were first used in the...