Humans have made deliberate use of solar energy going back to at least the 7th century B.C., from starting fires with magnifying glasses to the use of sunrooms, which are still found in many homes today. By the late 1800s, things had quickly taken a progressive turn with the discovery of the photovoltaic (PV) effect and the invention of the solar cell (or, PV cell). Photovoltaic is the term that refers to the conversion of sunlight into electricity.
In 1839, a nineteen-year-old named Alexandre-Edmond Becquerel, an assistant to his father at the National Museum of Natural History in Paris, conducted an experiment in which he coated platinum electrodes with silver bromide or silver chloride. He noticed afterward that when light shone upon the electrodes, small amounts of voltage and current were emitted. This is what is known as the “photovoltaic effect,” also called the “Becquerel effect.”
By the 1860s, the harnessing of solar power was being considered on the notion that coal supplies might soon become low. In 1873, English electrician Willoughby Smith, while conducting circuit tests on undersea telegraph cables, noted that the selenium rods he had chosen demonstrated higher electrical conductivity when under intense light.
Three years later, a professor at King’s College London, William Grylls Adams, along with a pupil of his, Richard Evans Day, further demonstrated that when a bond between platinum and selenium was illuminated, electricity was generated. This conclusively showed that light alone, when it strikes certain elements, could be used to produce electricity with no moving parts required.
In 1883, American engineer Charles Fritts applied this principle to invent the first solar cell, coating it with selenium and a very thin layer of gold. However, this cell operated at a mere 1-2% efficiency (efficiency being the average amount of electricity solar panels generate per square meter), which was not cost-effective enough for practical use. Solar-cell development then stagnated over the next several decades as coal became more available and the petroleum industry grew.
The modern solar cell is credited to Russell Ohl, a Bell Labs engineer who patented the first silicon PV cell in 1941. In 1954, three other Bell Labs employees, physicists Calvin Fuller, Daryl Chapin, and Gerald Pearson, patented the first practical solar cell, a 6%-efficient silicon-based panel.
The first commercially available PV cells were introduced the following year by Hoffman Electronics’ Semiconductor Division. Founder Leslie Hoffman sought to quickly improve the efficiency and lower the cost of solar panels, and by 1960 his PV cells were operating at 14% efficiency and being used to power transistor radios and orbiting satellites.
Solar-cell efficiency has improved a bit since, averaging 20%, although a world record was set in 2014 of 46% by a collaboration of French companies Soitec and CEA-Leti and Germany’s Fraunhofer Institute for Solar Energy Systems ISE. As PV cell technology advances, many more engineers and scientists are sure to be credited with making clean, renewable solar energy even more economical.