Solar panels generate electrical current by exploiting a phenomenon first described more than a century ago by a French physicist. In 1839, Henri Becquerel noted that silver and platinum electrodes in an acidic solution produced small amounts of electricity when exposed to light. This reaction became known as the photovoltaic effect, meaning “light into electricity.”
It wasn’t until 1954 that the first practical “solar cell” was created by scientists at Bell Laboratories in Murray Hill, New Jersey. Their silicon-based device arrived less than a decade after researchers at Bell invented the transistor, which is now a key component of electronic devices.
Modern solar cells are made of semiconductor materials like silicon or cadmium telluride. Light falling on this material energizes its electrons, giving them enough energy to create a flow of electrical current.
A typical solar panel combines dozens of solar cells in an electrical circuit to produce a usable voltage, which can provide power right away or be stored in batteries for later use. Some solar power installations can feed power directly into the electricity grid.
Since the amount of electric power produced by solar panels depends on the intensity of light, they don’t work well on cloudy days and not at all at night. A common solution is to back up solar power installations with batteries that store extra power until it is needed at a later time.
The cost of silicon used in many solar panels has dropped sharply over the last 20 years, with the result that, in the sunniest parts of the U.S., commercial solar power is now as cheap or cheaper than generating power from fossil fuels.
A 6 kW installation of solar panels, enough to power a typical American home, now costs about $14,000 — a fraction of what it would have cost a generation ago.