Published on January 20th, 2015 | by Glenn Meyers0
Photovoltaics Miniseries #9: Saved by Silicon – Part 2
January 20th, 2015 by Glenn Meyers
This ninth entry of Photovoltaics Miniseries celebrating the UN’s 2015 Year of Light features JohnPerlin, author of Let It Shine: The 6000-Year Story of Solar Energy, looking further at the impact of the semiconductor revolution and its principal material, silicon.For those who may have missed an episode in this miniseries, here is what has been published:
- Author John Perlin Celebrates the Coming Year of Light
- Author John Perlin & the Solar Cell
- The Pathway to Today’s Solar Revolution: Discovering the Photosensitivity of Selenium
- Photovoltaics Discovered in 1875: Interview with Author John Perlin
- Photovoltaic Dreaming: First Attempts at Commercializing PV
- Einstein: The Father of Photovoltaics Part 1
- Einstein: The Father of Photovoltaics – Part 2
- John Perlin Miniseries #8: Photovoltaics: Saved by Silicon – Part 1
In the last episode, Gerald Pearson had serendipitously discovered that silicon greatly exceeded the performance of selenium as a solar cell and brought it to the attention of his colleague Daryl Chapin. Chapin then took Pearson’s piece of silicon exposed it to strong sunlight, obtained the same smashing results, dropped selenium like a hot potato, and focused all subsequent studies on bettering what Pearson had done.
Theoretical calculations on the potential of silicon as a solar device supported Chapin’s change of heart. He found that under ideal conditions silicon could transform 23% of the incoming sunlight into electricity. Under real conditions a 6% efficient cell would satisfy his quest for a solar device that could directly turn sunshine into useful amounts of electricity.
Einstein’s photoelectric work provided Chapin with a framework from which to realize his goal. He knew that the heart of the cell – the p-n junction – had to be placed as close to the surface as possible to insure the collection of the more powerful photons.
CleanTechnica: Whose help did Chapin seek in furthering his work?
Perlin: He turned to Calvin Fuller, who had built the first silicon electronic pieces, for help. It turned out that two years earlier Fuller had done just as Chapin had envisioned and replicated for his colleague what he had done before. Despite the new approach, nothing significant happened when the new design was tested in sunlight.
CleanTechnica: What was the problem?
Perlin: After some head scratching, Chapin figured what went wrong: the shiny surface of the silicon reflected most of the incoming photons. A clear dull plastic coating changed the entire equation. Now these cells absorbed the great majority of the incoming light, raising the cell’s efficiency to 4%.
CleanTechnica: What was the next step in this new field of discovery? This could not have been easy at all.
Perlin: It wasn’t. Chapin then had to figure out an efficient way of transferring the charged electrons to where they would be used. This meant successfully adhering contacts onto the cells.
Once again Fuller came to the rescue by adding arsenic and boron to the silicon. In less than a year Chapin, Fuller and Pearson had gone from the first serendipitous discovery of the promise of silicon as a power solar cell, achieving the greatest breakthrough in the 6000-year history of solar energy and possibly in the entire field of electricity by presenting to the world the first device to directly convert enough of the sun’s energy into useful amounts of electricity.
Coming next: The world celebrates the beginning of one of humanity’s most cherished dreams – the possibility of harnessing of the almost limitless energy of the sun for the uses of civilization.
Photo Credit: Calvin Fuller prepares silicon solar cells via AT&T archive
John Perlin from Amazon:
Even as concern over climate change and energy security fuel a boom in solar technology, many still think of solar as a twentieth-century wonder. Few realize that the first photovoltaic array appeared on a New York City rooftop in 1884, or that brilliant engineers in France were using solar power in the 1860s to run steam engines, or that in 1901 an ostrich farmer in Southern California used a single solar engine to irrigate three hundred acres of citrus trees. Fewer still know that Leonardo da Vinci planned to make his fortune by building half-mile-long mirrors to heat water, or that the Bronze Age Chinese used hand-sized solar-concentrating mirrors to light fires the way we use matches and lighters today.
With thirteen new chapters, Let It Shine is a fully revised and expanded edition of A Golden Thread, Perlin’s classic history of solar technology, detailing the past forty years of technological developments driving today’s solar renaissance. This unique and compelling compendium of humankind’s solar ideas tells the fascinating story of how our predecessors throughout time, again and again, have applied the sun to better their lives — and how we can too.