Document Deep Dive: The Patent for the First Practical Solar Cell

We often think of solar power as a new and emerging technology. As it stands, less than one percent of the electricity used in the United States—just a tiny sliver of the energy pie—is sourced from the sun. But the story of photovoltaics began more than half a century ago.

In the 1950s, at Bell Labs, the research branch of the Bell Telephone Company in Murray Hill, New Jersey, three scientists—Daryl Chapin, Calvin Fuller and Gerald Pearson—toiled over thin strips of silicon, in an attempt to turn it into a strong conductor of electricity. They manipulated the material, bathing it in different elements, until on one auspicious day, they attached an ammeter, a device for measuring electric current, to the silicon and huddled around a lamp. They flicked on the light and in an instant realized that their silicon solar cell was a viable source of power.

The trio tweaked the technology until it effectively converted six percent of all incoming light into usable electricity. Though solar cells had been made before with the element selenium (which could only convert tenths of one percentage point), Chapin, Fuller and Pearson’s design is considered the first practical solar cell, given its efficiency rate.

Solar energy expert John Perlin spent a month at the AT&T Archives (the Bell Telephone Company eventually became AT&T) in Warren, New Jersey, to research his new book Let It Shine: The 6,000-Year Story of Solar Energy. At the archives, he was able to study the lab reports that Chapin, Fuller and Pearson wrote while working on the silicon solar cell.

The original patent (number 2,780,765) of the “solar energy converting apparatus,” shown above, is annotated based on a conversation with Perlin. Read the notes to learn more about how the Bell Labs scientists invented the solar cell and how the product—a technology still largely used today—works.

Megan Gambino | | READ MORE

Megan Gambino is a senior web editor for Smithsonian magazine.