From Sunlight to Solar Cell: Nine Pioneers of Solar Power

Augustin Mouchot built solar powered steam engines in the 1860s and 1870s, using large parabolic collectors to boil water, driven by worry that French coal might run short. At the 1878 Paris Universal Exposition his engine made ice from the sun alone. Falling coal prices in the 1880s ended his funding, which makes him the starting point of sunlight as a fuel substitute.

Willoughby Smith found in 1866, while testing underwater telegraph cables, that selenium conducts better when light falls on it, and presented the finding in 1873. He was not looking for solar power, yet this was the first sign that light could change electrical behavior in a solid.

William Grylls Adams, a professor at King's College London, showed that selenium actually produces an electric current when exposed to light, an early demonstration of what became known as the photovoltaic effect. This step moved from light changing conductivity to light generating current.

In 1883 Charles Fritts coated a thin layer of selenium with nearly transparent gold and built the first working solar cell. It converted under one percent of sunlight and found no practical use in his time, but it proved that a solid device could turn light directly into current.

Frank Shuman completed a large solar thermal plant at Maadi near Cairo in 1913, using long parabolic mirrors to make steam for an irrigation pump. The First World War stopped its operation and funding. It is the heat route to solar power, set beside the photovoltaic route on this trail.

Russell Ohl, working at Bell Telephone Laboratories in 1940 on radio detectors, discovered the p-n junction in silicon and saw a junction sample generate a substantial current in light. His 1941 patent is the direct ancestor of the silicon solar cell, and the same junction underlies the diode and transistor.

Daryl Chapin was asked in the early 1950s to find a more reliable power source than selenium cells for remote telephone equipment in humid climates. He developed silicon into a practical photovoltaic device through systematic testing of doping and cell designs, and helped demonstrate the Bell Solar Battery in 1954.

Calvin Fuller, a Bell Laboratories chemist, applied the doping technique he had developed for transistors to silicon, introducing controlled amounts of lithium and later boron to make a durable p-n junction. This let the 1954 solar battery reach roughly six percent efficiency.

Gerald Pearson, a Bell Laboratories physicist, completed the team with Chapin and Fuller that built the first practical silicon solar cell in 1954. The Bell Solar Battery at roughly six percent efficiency was many times better than earlier cells and is the ancestor of the modern solar panel industry.