MURRAY HILL, N.J. (WHTM) — On this day in 1954, Bell Telephone Laboratories demonstrated the first practical solar panel.

The emphasis here is on practical. The photovoltaic (or photoelectric) effect, where a material produces an electric current when exposed to light, was discovered in 1839 by Edmond Becquerel, a French physicist. Throughout the 1800s people experimented with the concept of solar power, either out of curiosity or the hope of being on the cutting edge of the next big thing in power generation. (A lot of patents got issued along the way.) But solar power was hamstrung by its inefficiency. Experimenters were lucky if one percent of the light they shone on a cell would come out as electricity. Part of the problem-nobody had a clear idea why the photoelectric effect happened.

Albert Einstein explained what was going on. In a paper published in 1905, he treated light as a beam of particles-photons. The energy of the beam is determined by its frequency. (Insert convoluted math here.) When the beam is pointed at a piece of metal, the photons will collide with atoms, and IF a photon is at the right frequency, it will knock loose an electron-producing the photovoltaic/electric effect. The paper won Einstein the Nobel Prize in Physics in 1921.

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Research continued through the first half of the 20th Century, with incremental, minor improvements in the efficiency of solar power.

In 1953 Bell Telephone Laboratories, those wonderful folks who gave us the transistor, the laser, radio astronomy, the charge-coupled device (CCD), information theory, the Unix operating system, and a variety of programming languages (among other things) had some people working on two different projects, which cross-pollinated to produce the new solar cell.

Engineer Daryl Chapin was trying to develop power sources for phone systems in remote locations. Chemist Calvin Fuller and physicist Gerald Pearson were working on fine-tuning semiconductors (such as transistors) by introducing impurities to them. Pearson tested silicon with gallium impurities and discovered the material produced a strong electric current when exposed to light. The three men worked together to refine the discovery, solving the remaining technical shortcomings and working out ways to get the solar cells from the lab bench into general use.

Bell Labs announced the invention on April 25, 1954, in Murray Hill, New Jersey. They demonstrated their solar panel by using it to power a small toy Ferris wheel and a solar-powered radio transmitter. The new solar cells turned sunlight into energy at an astonishing (for the time) six percent. Within a few years, solar cells were powering satellites. Prices on solar energy have dropped and we can now find solar cells everywhere, from the roofs of our houses to pocket calculators. The average efficiency of a commercially manufactured solar panel is up to 20-22 percent, and the current world record for efficiency, set in a laboratory in 2019, is 47.1 percent.

Bell Telephone Laboratories, by the way, still exists. From 1984 to 1996 they were AT&T Bell Laboratories, Bell Labs Innovations from 1996 to 2007, and is now known as Nokia Bell Labs.

For more about Bell Laboratories, click here.

For more about the history of solar cells, click here.