Calvin Fuller

American physical chemist

• Born: May 25, 1902
• Birthplace: Chicago, Illinois
• Died: October 28, 1994
• Place of death: Vero Beach, Florida

Fuller was one of the inventors of the first efficient silicon solar cell. Solar cells have provided a renewable resource for electricity and have made space exploration possible.

Primary fields: Chemistry; electronics and electrical engineering; physics

Primary invention: Silicon solar cells

Early Life

Calvin Souther Fuller was born to Bessie and Julius Quincy Fuller in Chicago, Illinois. After graduating high school, Fuller attended the University of Chicago, where he received a B.S. in physical chemistry. He continued his studies at the University of Chicago and in 1929 was awarded a Ph.D. in physical chemistry.

Fuller began working for Bell Laboratories the year after his graduation. His first projects were developing insulating materials and researching polymers. During World War II, he served as the head of synthetic rubber research for the U.S. government, investigating new products that could replace real rubber, of which there was a shortage during the war. In 1948, he began developing semiconductors for Bell Laboratories. He and his wife, Willmine, had three children: Robert, Stephen, and John.

Life’s Work

In 1952, at Bell Labs, Daryl Chapin was given the task of solving a problem with the batteries in the Bell telephone system. The batteries worked well in temperate climates, but in hot, wet tropical climates they quickly degraded. Chapin at the time was investigating alternative forms of energy such as wind machines. He suggested that solar cells might be a solution to the battery problem.

The first solar cell was designed byCharles Fritts in 1883. It was made of selenium and gold but was only about 1 percent efficient. By 1952, selenium solar cells had been modestly improved, but they produced a paltry 5 watts per square meter, which equated to harnessing less than one-half of one percent of the available energy in the sunlight. Chapin wanted to achieve capturing at least 6 percent of the solar energy with a cell.

During this time, in March, 1953, Fuller was collaborating with Gerald Pearson on semiconductors, experimenting with silicon to make the semiconductors. In 1946, Bell Labs employee Russell Ohl had developed a method to reduce the impurities in silicon so that it could function as a semiconductor. Ohl realized that the impurities in the silicon created resistance and thwarted electron flow. Fuller had perfected a chemical process to remove even more impurities from the silicon so that it would be a better electrical conductor. He also added a small amount of gallium to give the silicon a positive charge. After bathing the silicon in lithium, Pearson shone light on the piece and recorded the amount of electricity it produced. The silicon made a much-improved solar cell compared to the selenium solar cell. Pearson and Chapin were good friends, and Pearson shared the information about the superiority of the silicon cell with him.

Pearson’s cell worked about five times better than Chapin’s selenium cell, but Chapin found it very difficult to make electrical connections to the silicon to collect the electricity it was producing. He could not solder wires directly to the silicon, and attempts to electroplate various metals to the silicon failed. Chapin approached Fuller for help in fixing his PN junction (the point of contact between positively charged and negatively charged semiconductors), as Fuller had successfully worked with PN junctions a few years earlier when he was developing transistors. Fuller substituted the lithium with phosphorous, which doubled the output of the cell, but unfortunately it was still shy of Chapin’s 6-percent goal.

In the meantime, Radio Corporation of America (RCA), Bell Labs’ main rival, unveiled to the public its Atomic Battery, which was powered by photons from a nuclear-waste product, strontium 90. RCA’s goal in using the strontium 90 was to demonstrate that nuclear waste could be reused productively. Unfortunately, strontium 90 has since been categorized as a highly dangerous component of nuclear waste and an unsafe choice for inclusion in batteries. Interestingly, the Atomic Battery could also be powered by solar photons, so when the RCA scientists performed their first public demonstration, they had to shield the battery from the Sun so that it would only be powered by the strontium 90.

The success of the Atomic Battery put pressure on Bell Labs to accelerate its solar cell work. Fuller went back to the drawing board and developed a completely new process for making silicon into a solar cell. Instead of using the positively charged gallium, he mixed arsenic with the silicon to give the silicon a negative charge, and then he cut the silicon into thin strips. When coated with a layer of boron, the cell had a PN junction very close to the surface of the cell. This allowed for good electrical contacts for transporting the electricity off the cell. One of these designs finally achieved Chapin’s goal of 6-percent efficiency.

The Bell Solar Battery was first presented to the public on April 25, 1954. Bell Labs held a press conference to demonstrate the solar battery by having it power a radio transmitter. Bell Labs claimed that the battery could produce 50 watts of electricity per square yard of cell. By 1955, Bell was using the cell in its telephone carrier system; in 1958, the cell was used to power the U.S. Vanguard 1 satellite, the first satellite to use solar energy.

Bell Labs owned the patents Fuller received while he was working for the company, so Fuller never became wealthy as a result of his inventions. This did not bother him, however, as he received great personal satisfaction from his scientific achievements. Altogether, Fuller and Bell Laboratories were granted thirty-three patents for his semiconductor and solar cell developments.

Fuller retired to Vero Beach, Florida. From there, he made many trips across the United States with his wife in a Silver Stream camper. He died in Vero Beach in 1994. On June 22, 2006, Fuller was inducted into the New Jersey Inventors Hall of Fame for development of the semiconductor photovoltaic solar cell. Along with Daryl Chapin and Gerald Pearson, he was inducted into the National Inventors Hall of Fame on May 2, 2008.

Impact

The invention of the solar cell and its applications have had far-reaching consequences in many areas. The solar cell gave the U.S. space program a source of energy to use for its satellites, spacecraft, space station, and remote moon and planetary landers. Without solar power generators, satellites could not continue to function in orbit for years, the rovers Spirit and Opportunity could not have explored Mars, and the International Space Station project would never have gotten off the ground. In the early twenty-first century, the international market for solar-generated electricity sometimes grew by more than 25 percent per year. Today’s commercially produced solar cells have a life span of at least twenty years before they begin to lose efficiency.

Solar cells can be used to generate electricity in locations where there is no other power source. They light remote road signs and power solar cars. Solar cell arrays are used to generate electricity for commercial factories, warehouses, and stores as well as private homes. They can be made large enough to provide electricity for towns or small enough to power a handheld calculator. New flexible solar cell materials are being used to make military tents so soldiers can have air conditioning and power for their entertainment devices; the materials are also used to make cases for electronic equipment such as cell phones, laptops, and radios so the devices can be recharged without having to plug them into a standard electrical socket. The power produced can be used directly, stored in a battery until needed, or sent into the commercial power grid. The ability to store the generated electricity is very important, as solar panels must be exposed to sunlight to generate electricity, so they do not work at night or on cloudy days.

When the function of the solar cell is reversed, electricity can be converted into light. This process allows for fiber-optic lines to carry data, a technology that transmits telephone calls, television signals, and information throughout the Internet.

Bibliography

Bradford, Travis. Solar Revolution: The Economic Transformation of the Global Energy Industry. Cambridge, Mass.: MIT Press, 2008. Bradford, a corporate-buyout specialist, argues that solar energy will become an increasingly cost-effective option in the coming decades.

Komp, Richard J. Practical Photovoltaics: Electricity from Solar Cells. Ann Arbor, Mich.: Aatec, 1995. A good basic book on how solar cells are made, how they work, and their present and future applications. The introduction includes a very brief history of their development by Fuller, Chapin, and Pearson.

Perlin, John. From Space to Earth: The Story of Solar Electricity. Cambridge, Mass.: Harvard University Press, 2002. A history of solar power that includes a chapter on the development of the Bell Labs cell by Fuller, Chapin, and Pearson.

Van Pelt, Michael. Space Invaders: How Robotic Spacecraft Explore the Solar System. New York: Springer, 2006. A comprehensive discussion on unmanned space exploration, including details on how solar cells and arrays are used to power spacecraft, satellites, and robots.