How Electric Power Came from the Sun

The realization that sunlight can be a source of electricity as well as warmth is 178 years old. In 1839, the French physicist Alexandre Edmond Becquerel noticed that more electric current flowed during daylight than in darkness during experiments with a platinum anode and cathode. But an accidental discovery in 1940 proved to be decisive for the commercial use of solar energy. In his research on silicon, the American physicist Russell Ohl observed an effect that was similar to the one that Becquerel noted 100 years earlier: Electric current flowed under the application of light. But he benefited from a simple fact: his sample had a crack in it. This apparently led to positive charging on one side and negative charging on the other due to contamination with other atoms. As a result, current was able to flow. This positive-negative transfer remains the basis for every silicon solar cell down to the present.

Silicon Contamination as a Recipe for Success

Ohl had made his discovery at the Bell Telephone Laboratories, and it was to prove valuable to other researchers at this institution. One decade after Ohl’s sudden insight, Gerald Pearson, Calvin Fuller and Daryl Chapin were looking for a way to autonomously supply remote telephone facilities with current. They learned that the silicon used in the new transistor technology exhibited the capabilities that Ohl had discovered. In the meantime, it had become clear that silicon contaminated with other elements became more sensitive to light and produced higher voltages. The results were still not satisfactory, so Pearson, Fuller and Chapin experimented with boron and arsenic. They mixed – or doped, in the jargon of the profession – the silicon with traces of the two elements on its upper or lower side and reached energy conversion efficiencies of up to six percent. On that basis, the first silicon solar cell was presented to the world in 1954.