The best way to look at the history of solar panels is by the progress of photovoltaic efficiency since the first created cell. Efficiency rates reflect how much of the sunlight taken in by a solar cell is converted into electricity. There is a theoretical limit of 33.7% to the maximum efficiency of a solar cell with a single p-n junction called the Shockley-Queisser Limit. As you read the timeline below, you’ll start quite far from the limit, reach, and then pass it only in recent years as changes in technology have developed.
The Shockley-Queisser Limit was developed by William Shockley and Hans-Joachim Quisser at Shockley Semiconductors in 1961, and outside of a few notable developments, has held for most modern solar cells of the single p-n junction and non-multilayer variety. These are the most commonly available kinds of solar cells available.
1839: Alexandre Becquerel reports his observations on the photovoltaic effect, where electrical current is generated by exposing a material to light.
1883: Charles Fritts created a Selenium-based solar cell with a photovoltaic efficiency of up to 2 percent.
1887: Heinrich Hertz discovered the photoelectric effect, the observed effect closely related to the photovoltaic effect, except dealing with the ejection of electrons by the material exposed to light. Instead of entering a different material like in the photovoltaic effect, the electrons eject into open space without creating an electric current.
1888: Aleksandr Stoletov creates the first solar cell to harness the photoelectric effect.
1905: Albert Einstein publishes a paper explaining the photoelectric effect in which he also explained his theory of special relativity.
1954: The first silicon-based solar cell was created at Bell Labs and had an efficiency rate of 6%
1957: 1960: Hoffman Electronics achieved breakthroughs in photovoltaic efficiency, first in 1957 with a record 8% and then in 1960 with 14% efficiency.
1979: Solar panels are installed on the White House by President Jimmy Carter. These were removed in 1981 by Ronald Reagan’s orders, and new ones were installed in 2010 by President Obama.
1985: Researchers at the University of South Wales built a silicon-based solar 20% with silicon-based solar cells.
1991: The National Renewable Energy Laboratory is created by the U.S. Department of Energy by order of President George H.W. Bush.
1999: National Renewable Energy Laboratory and SpectroLab Inc reached a record-breaking 33.3% photovoltaic efficiency.
2006: The Solar Investment Tax Credit is enacted, resulting in significant growth of the solar industry.
2009: Perovskite solar cells are invented, generating 3.8% efficiency but showing promise for future research into a viable silicon alternative.
2013: Spectrolabs reached 38.8% efficiency for a multi-junction solar cell, beating their previous 37.8% record. These kinds of panels are very expensive and used for niche purposes like spacecraft and are not yet commercially available.
2015: Researchers at École Polytechnique Fédérale de Lausanne in Switzerland perovskite solar cells reached 21% efficiency.
2016: Scientists at the University of South Wales reached 34.5% efficiency using silicon-based solar cells.
2017: The University of Toronto researchers in perovskite solar cells reached a 20.1% efficiency
2020: Researchers in perovskite solar cells achieve 25.2% efficiency
As you can tell, recent gains in perovskite solar cells show a lot of promise, but silicon-based aren’t going anywhere. Tandem solar cells have been recorded as having up to 26% efficiency, using a layer of perovskite on top of silicon. Other semiconductors have been tested and performed well, but those benefits have yet to reach a commercial or manufacturing audience. These gains have resulted in cheaper solar power over time.
Most of the focus of solar panel development has been on making the individual solar cells more efficient, but in recent years interest in the cosmetic appearance has resulted in interesting research and products, including solar panels that have roof shingle-like appearance and other ways of more subtly integrating the power-producing panels. This means in time we’ll see better looking and more efficient solar panels than ever before.
