Why “first” is hard to answer
There is no single date on which the first solar panel was built. A “panel” is a group of cells, and a “cell” is a device that turns light into electricity. Whether the first one means a laboratory effect, a working selenium device, a practical silicon cell, or a sealed commercial module, the answer and the person credited differ. All of those milestones are well documented, so the story below follows them in order.
1839: the photovoltaic effect
The earliest widely cited observation comes from the French physicist Edmond Becquerel, who in 1839 found that certain electrodes dipped in a liquid produced a small current when light fell on them. He was a young researcher at the time. His work established that light could produce electricity directly, but his arrangement was a chemical cell in a laboratory and not something anyone would call a panel.
Selenium enters the story
In 1873 the English engineer Willoughby Smith, working on telegraph cables, noticed that selenium changed its electrical resistance when exposed to light. This was photoconductivity, a related effect, and it drew attention to the material.
In 1876, William Grylls Adams and his student Richard Evans Day showed that a bar of selenium with electrodes could produce a current when lit, with no battery involved. Many historians consider this the first demonstration of a solid material generating electricity from light, which makes it a strong candidate for the first photovoltaic cell.
In the 1880s, Charles Fritts in New York coated selenium with a thin layer of gold and built larger plates, which he proposed could be used for generating power. Reports commonly describe their efficiency as about one percent. The Fritts device is sometimes called the first true solar cell, though how it worked was not understood at the time. Selenium cells never produced useful amounts of power. They did find a use in light meters, and photographers relied on them for many years.
Physics explains the effect
For decades, the theory lagged behind the experiments. In 1905 Albert Einstein explained how light could release electrons from a material by treating light as quanta, work that earned him the 1921 Nobel Prize in Physics. Later, advances in quantum mechanics and in understanding semiconductors, the same knowledge that led to silicon chips, made it possible to explain why a junction between two kinds of treated material could generate a voltage. In the 1940s, Russell Ohl, also at Bell Laboratories, noticed a current produced by light in a cracked silicon sample that contained a junction, an accidental discovery that is often noted as a step toward the silicon cell.
1954: the silicon cell
Bell Laboratories researchers Daryl Chapin, Calvin Fuller and Gerald Pearson announced a silicon solar cell in April 1954. Chapin had been looking for a power source for remote telephone equipment, and had found that selenium was inadequate. Fuller and Pearson had been working on how to introduce small amounts of impurities into silicon to control its electrical properties, and their approach produced a cell with an efficiency usually quoted at about 6 percent, a large improvement over the earlier devices.
The group built small arrays, and the cells were demonstrated powering a small toy Ferris wheel and a radio transmitter, according to accounts of the announcement. These were demonstrations rather than a product line. At the time, the cost of silicon cells per watt was far too high for ordinary electricity supply.
From cell to panel
A single cell produces only a small voltage, so a usable panel joins many cells in series and parallel and encases them to protect them from weather. The first modules for space use were assembled in the late 1950s, and the American satellite Vanguard 1, launched in 1958 shortly after the Sputnik launch had started the space race, carried small solar-powered equipment. Later communications satellites depended on larger arrays. Panels for ground use appeared in the 1960s and 1970s, mostly for specialized needs.
So who gets the credit?
Reasonable people can name different answers.
- Becquerel (1839) for discovering the photovoltaic effect.
- Adams and Day (1876) for showing it in a solid material.
- Fritts (1880s) for an early larger device built with an eye to power generation.
- Chapin, Fuller and Pearson (1954) for the first practical silicon cell.
The sequence is a good example of how an invention often matures: one person notices an effect, others find a material, theory catches up, and engineers turn it into a device someone can use.