1800’s: Light and Electricity
In the first chapter of solar history was the discovery that light was related to electricity. The first solar cells or (photocells) did not produce much power and used an element called selenium (Se). They were often used as light sensors for cameras or other electronic eye applications since they could only convert a mere 0.5% of the sun’s energy into electricity.
- In 1839, Alexandre Edmond Becquerel opened the door to solar energy, showing a strong relationship between light and electricity.
- In 1873, Willoughby Smith accidentally discovered photoconductivity in Selenium. Shortly thereafter, William Grylls Adams and his student Richard Day discovered that when Selenium (Se) was exposed to light, it produced electricity. While it wasn’t perfect, it was the first step towards the energy revolution — proving that sunlight itself could be converted into usable electricity.
- In 1887, Heinrich Hertz observed the photoelectric effect and the production and reception of electromagnetic waves, also known as the Hertz effect. This lead to more research by researchers like Hallwachs, Hoor, Righi, and Stoletow.
- From 1888-1891, Aleksandr Stoletov found a way to measure the relationship between the intensity of light, and the electric current it generated, based on Heinrich Hertz’s discoveries.
1900’s: Quantum Mechanics
When Einstein and Millikan related light energy to movement at a quantum level, this paved the way for future solar research (and quantum mechanics).
- In 1902, Lenard observed that the energy of individual electrons increased with the frequency of light.
- In 1905, Albert Einstein published a paper taking the hypothesis that light energy was at a quantum level and making it into a formula. This is the fundamental theory that has driven the solar energy revolution and quantum mechanics. *Einstein was awarded the Nobel Prize in 1921 for “his discovery of the law of the photoelectric effect”
- In 1914, Robert Millikan’s experiments supported Einstein’s model of the photoelectric effect. *Millikan was awarded the Nobel Prize in 1923 for “his work on the elementary charge of electricity and on the photoelectric effect”
- In 1946, Russel Ohl patented the modern junction semiconductor solar cell.
1950’s: The Space Race
Soon after the discovery of the transistor, the modern solar cell —the solar battery— was announced to the world in 1954 with an efficiency of 6%. This new iteration was based on mono-crystalline Silicon (Si). These were commercially produced and applied to space exploration missions, which drove the development of higher efficiencies in solar cells during the space race.
- In 1954, the first photovoltaic cell was publicly presented at Bell Laboratories by Calvin Souther Fuller, Daryl Chapin, and Gerald Pearson.
- In 1958, solar cells were applied to the Vanguard satellite as an alternative to a battery.
- In 1959, the US launched Explorer 6 launched with wing-shaped solar arrays consisting of Hoffman solar cells.
- By 1960, solar cells were the main power source for orbiting satellites and probes.
- In 1973, Elliot Berman founded Solar Power Corporation, a subsidiary of Exxon, and made huge strides in the cost of solar cell production.
- After 1973, Oil Crisis, oil companies used the extra profits to advance solar innovation and production.
In recent years, research has moved towards designing lightweight, flexible, and highly efficient solar cells. Manufacturers have added strength, protection, and widened the spectrum of light a solar cell can convert into energy.
The fifth chapter in solar cells is happening now with lots of innovation happening in the solar cell market.
Many types of cells are being produced or tested such as organic, perovskite, multijunction, concentrator, and many others. Solar cell efficiencies are up to 42% in the lab meaning that 42% of the sun’s energy can be converted into electricity using multi-junction concentrator solar cells. Research for higher efficiencies, lower costs, and new materials are all active areas of research.
There is a lot more history!
The above history talks about the progression of solar cells themselves through time but if you’d like to learn more about what events took place to cause change and movement in the industry I suggest reading this article by John Perlin on NREL’s website https://www.nrel.gov/docs/fy04osti/33947.pdf or by checking out his book for a complete history on solar energy entitled Let It Shine: The 6,000-Year Story of Solar Energy.