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September 18, 2015 | A History of Solar Power: How International Inquiry Transformed Solar Light into Solar Energy

Scientists all over the world have contributed to the development of solar power. For both heat and light energy sources, the sun’s power has been considered a solution to yesterday’s and today’s energy challenges. These international innovators laid the foundation for the solar industry as it is known today.

In 1767, Horace Benedict de Saussure created an insulated box covered with three layers of glass to absorb the sun’s heat. The Swiss scientist had developed the first solar oven, which was capable of reaching over 200° Fahrenheit. Sixty years later, in 1839, the photovoltaic (light into energy) effect was discovered by French scientist Edmond Becquerel. He determined that an electrical current could be increased in certain materials when they were exposed to light, thus separating the two readily apparent solar energies: light and heat. And in 1876, Englishmen William Grylls Adams and Richard Evans Day proved that light could produce energy in and of itself, when they reported that illuminating a junction between selenium and platinum created a photovoltaic effect. After that, scientists around the world took up the project to convert solar light into an accessible and reliable energy source.

In 1883, American inventor Charles Fritts devised a plan for the first solar cell, using junctions formed by coating a selenium wafer with an extremely thin layer of semi-transparent gold and a sheet of glass. It had an energy efficiency of less than 1%, but it proved to be a reliable, albeit inefficient, source of energy.

In 1905, Albert Einstein took up the project in his own unique way. He proposed the "photon" theory of light – how light can “liberate” electrons on a metal surface. Einstein was building on Heinrich Hertz’s discovery that shining ultraviolet light onto metal electrodes could make sparks hop between them. Hertz didn’t speculate on how the light influenced the result, which Einstein found to be a great puzzle. Einstein proposed that the frequency of the light caused electrons in the metals to be released in the form of kinetic energy. He won his only Nobel Prize for this subject, which was awarded 16 years later, in 1921.

The next significant step towards sustainable photovoltaic energy came in 1918, when Jan Czochralski, a Polish Scientist, was able to grow single-crystal silicon. Single-crystal silicon is a superior foundation for photovoltaic activity because its molecular structure is grown from the same crystal, making it uniform in shape and, therefore, ideal for transferring electrons efficiently through the material. This development laid the foundation for the silicon-based solar cell in use today.

Finally, in 1954, three American scientists from Bell Labs devised solar cells that actually powered electrical devices. David Chapin was struggling with selenium wafers, but couldn't exceed the 1% efficiency level. His colleagues Calvin Fuller and Gerald Pearson were working on a separate project to develop silicon transistors. They discovered that one of their transistors created electricity when exposed to light. The three men combined their efforts and introduced the world’s first “solar battery,” which powered a toy windmill and a radio. The efficiency was a remarkable (for the time) 6%, and the solar energy industry took giant leap forward.

In the sixty years since that revelation, solar electricity has become a significant part of the global energy industry and a potential leader in the quest for non-polluting global energy resources. Materials, chemicals and construction methods have been modified to increase efficiencies and provide long-term, stable and reliable solar energy production and storage. In 2014, a French-German collaboration was able to present a photovoltaic cell with 46% efficiency. That same year, three other international companies were able to present solar cells capable of more than 25% efficiency. Although these innovations remain in the lab, they promise that emerging solar energy developments are well on their way to providing a clean, reliable and stable energy supply anywhere on the Earth that the sun shines.