From Mary Bellis,
Your Guide to Inventors.
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Today's photovoltaic systems are used to generate electricity to pump water, light up the night, activate switches, charge batteries, supply power to the utility grid, and much more.

1839:

Nineteen-year-old Edmund Becquerel, a French experimental physicist, discovered the photovoltaic effect while experimenting with an electrolytic cell made up of two metal electrodes. 1873: Willoughby Smith discovered the photoconductivity of selenium.

1876:

Adams and Day observed the photovoltaic effect in solid selenium.

1883:

Charles Fritts, an American inventor, described the first solar cells made from selenium wafers.

1887:

Heinrich Hertz discovered that ultraviolet light altered the lowest voltage capable of causing a spark to jump between two metal electrodes.

1904:

Hallwachs discovered that a combination of copper and cuprous oxide was photosensitive. Einstein published his paper on the photoelectric effect.

1914:

The existence of a barrier layer in PV devices was reported.

1916:

Millikan provided experimental proof of the photoelectric effect.

1918:

Polish scientist Czochralski developed a way to grow single-crystal silicon.

1923:

Albert Einstein received the Nobel Prize for his theories explaining the photoelectric effect.

1951:

A grown p-n junction enabled the production of a single-crystal cell of germanium.

1954:

The PV effect in Cd was reported; primary work was performed by Rappaport, Loferski and Jenny at RCA. Bell Labs researchers Pearson, Chapin, and Fuller reported their discovery of 4.5% efficient silicon solar cells; this was raised to 6% only a few months later (by a work team including Mort Prince). Chapin, Fuller, Pearson (AT&T) submitted their results to the Journal of Applied Physics. AT&T demonstrated solar cells in Murray Hill, New Jersey, then at the National Academy of Science Meeting in Washington, DC.

1955:

Western Electric began to sell commercial licenses for silicon PV technologies; early successful products included PV-powered dollar bill changers and devices that decoded computer punch cards and tape. Bell System's demonstration of the type P rural carrier system began in Americus, Georgia. Hoffman Electronics's Semiconductor Division announced a commercial PV product at 2% efficiency; priced at $25/cell and at 14 mW each, the cost of energy was $1500/W.

1956:

Bell System's demonstration of the type P rural carrier system was terminated after five months.

1957:

Hoffman Electronics achieved 8% efficient cells. "Solar Energy Converting Apparatus," patent #2,780,765, was issued to Chapin, Fuller, and Pearson, AT&T.

1958:

Hoffman Electronics achieved 9% efficient PV cells. Vanguard I, the first PV-powered satellite, was launched in cooperation with the U.S. Signal Corp. The satellite power system operated for 8 years.

1959:

Hoffman Electronics achieved 10% efficient, commercially available PV cells and demonstrated the use of a grid contact to significantly reduce series resistance. Explorer-6 was launched with a PV array of 9600 cells, each only 1 cm x 2 cm.

1960:

Hoffman Electronics achieved 14% efficient PV cells.

Continue > 1960 to present