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N Solar Cell Watches

The first solar cells were developed by D. Chapin, G.L. Pearson and C. Fuller in the USA. In the Horological Journal of April 1958, the following can be read: "One of their electric wrist watches has been modified by Hamilton Watch Co. to operate on power provided by the sun. A small silicon cell converts light into enough power to store sufficient electricity to run the watch. No commercial development is planned". A number of firms, for instance Patek Philippe (1952) and Lip, used solar cells in small clocks.

1920The first research on selenium starts.
1930The first photocells are invented by the physicists B. Lange and W. Schottky.
1953Patek Philippe presents the first light powered clock at the Basle Fair. The clock was equipped with photocells made of selenium.
1976The first Swiss-made solar powered cells for watches are manufactured by Esotron S.A. of La Chaux-de-Fonds, Switzerland.


The first solar cells were made of silicium and selenium. When light falls on a special kind of semiconductor diode, the photons create pairs of holes and electrons. The negative electrons go in the depletion-layer to the N-silicium and the positive holes to the P-silicium, and a voltage difference of about 0.3 to 0.5 Volt will be created. Four or five solar cells connected together in series, generate 1.5 Volt; the voltage required to make a watch run or recharge its battery.

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Copyright by Pieter Doensen

email: doensen@xs4all.nl

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