ABSTRACT
Becquerel [1] Ÿrst discovered that sunlight can be converted directly into electricity in 1839, when he observed the photogalvanic e¢ect. Aµer more than a century of theoretical work, the Ÿrst solar cell was not developed until 1954, by Chapin, Fuller, and Pearson, when su£ciently pure semiconductor material had become available. It had an e£ciency of 6%. Only 4 years later, the Ÿrst solar cells were used on the Vanguard I orbiting satellite.
