Using an exotic form of silicon could substantially improve the efficiency of solar cells, according to computer simulations by researchers at the University of California, Davis, and in Hungary. The work was published Jan. 25 in the journal Physical Review Letters.
Solar cells are based on the photoelectric effect: a photon, or particle of light, hits a silicon crystal and generates a negatively charged electron and a positively charged hole. Collecting those electron-hole pairs generates electric current.
Conventional solar cells generate one electron-hole pair per incoming photon, and have a theoretical maximum efficiency of 33 percent. One exciting new route to improved efficiency is to generate more than one electron-hole pair per photon, said Giulia Galli, professor of chemistry at UC Davis and co-author of the paper.
"This approach is capable of increasing the maximum efficiency to 42 percent, beyond any solar cell available today, which would be a pretty big deal," said lead author Stefan Wippermann, a postdoctoral researcher at UC Davis.
"In fact, there is reason to believe that if parabolic mirrors are used to focus the sunlight on such a new-paradigm solar cell, its efficiency could reach as high as 70 percent," Wippermann said.
Galli said that nanoparticles have a size of nanometers, typically just a few atoms across. Because of their small size, many of their properties are different from bulk materials. In particular, the probability of generating more than one electron-hole pair is much enhanced, driven by an effect called "quantum confinement." Experiments to explore this paradigm are being pursued by researchers at the Los Alamos National Laboratory, the National Renewable Energy Laboratory in Golden, Colo., as well as at UC Davis.
"But with nanoparticles of conventional silicon, the paradigm works only in ultraviolet light," Wippermann said. "This new approach will become useful only when it is demonstrated to work in visible sunlight."
The researchers simulated the behavior of a structure of silicon called silicon BC8, which is formed under high pressure but is stable at normal pressures, much as diamond is a form of carbon formed under high pressure but stable at normal pressures.
The computer simulations were run through the National Energy Research Scientific Supercomputing Center at the Lawrence Berkeley Laboratory, which granted the project 10 million hours of supercomputer time.
The simulations demonstrated that nanoparticles of silicon BC8 indeed generate multiple electron-hole pairs per photon even when exposed to visible light.
"This is more than an academic exercise. A Harvard-MIT paper showed that when normal silicon solar cells are irradiated with laser light, the energy the laser emits may create a local pressure high enough to form BC8 nanocrystals. Thus, laser or chemical pressure treatment of existing solar cells may turn them into these higher-efficiency cells," said co-author Gergely Zimanyi, professor of physics at UC Davis.
University of California - Davis: http://www.ucdavis.edu
This press release was posted to serve as a topic for discussion. Please comment below. We try our best to only post press releases that are associated with peer reviewed scientific literature. Critical discussions of the research are appreciated. If you need help finding a link to the original article, please contact us on twitter or via e-mail.
Kate Brooks' aerial photos show the beauty of Africa's elephants, and the catastrophic extinction they face at the hands of poachers.
It didn't feel like it in much of the U.S., but August set a record worldwide
More endangered sockeye salmon have made the 900-mile journey from the Pacific Ocean to central Idaho's high-elevation Redfish Lake this fall than in any previous year going back nearly six decades
With rising seas, cities like Satellite Beach, Fla., are debating options: defend the shoreline to avoid destruction, or retreat, withdrawing homes and businesses from the water's edge.
The extent of Antarctica's sea ice has hit yet another record high, and counter-intuitively global warming is responsible
The largest consumer of coal in the world has announced radical restrictions on coal imports and its domestic transport and use
An otherworldly photograph of a lagoon reflecting the swirls of the aurora has taken the top prize in the Astronomy Photographer of the Year competition
The U.S. Department of Agriculture on Wednesday gave final approval to new genetically modified corn and soybeans developed by Dow AgroSciences that, while heavily criticized by environmentalists and some farmers, are portrayed by Dow as an answer to weed resistance problems that limit crop production.
With new genetic insights, researchers aim to fight a devastating coffee fungus
Hedgehogs are more thinly spread in the UK than previously believed, a study using ink pads to record their paw prints reveals.