The image of a solar cell glistening in the sun illustrates many a magazine article on modern technology. But the means of converting light energy into electrical energy is nothing new. A "photovoltaic effect," whereby light hitting an electrode immersed in an electrolyte produces a current, was first observed in 1839 by A. E. Becquerel. This phenomenon was harnessed in 1884 when the first solar cell was built by American scientist Charles Fritts.
Fritts used the less than economic design of semiconductive selenium coated in a thin layer of gold to achieve the conversion, at an efficiency of just 1 percent. The cell works by absorbing energy in the form of photons of light, which then displace electrons in the semiconductor, generating a current.
Despite Fritts's optimism that the technology might replace centralized power plants, no one was ever going to power their home with only this kind of efficiency. But Fritts's ideas did find applications in photography. Selenium, and later copper, cells made convenient sensors for measuring lighting levels in twentieth-century cameras.
Solar technology benefited from the introduction of silicon semiconductors in 1941. Developments in the 1950s and 1960s increased efficiency to levels where domestic applications became feasible, and solar panels became a lightweight power source for spacecraft and satellites. The technology is still inefficient today, with commercial cells performing at only around 13 percent, and the world record standing at 42.8 percent. Still, this is enough to power homes, outdoor gadgets, and spacecraft.
