U.S. Olympic swimmer Michael Phelps isn't the only one breaking world records these days.
The U.S. National Renewable Energy Laboratory this week said it had set a world record insolar-cell efficiency by creating a cell able to convert 40.8 percent of sunlight into electricity in lab tests.
The cell is made up of three layers of two different materials stacked on top of each other to convert different portions of the solar spectrum into electricity.
Companies such as Sylmar, Calif.-based Spectrolab already make triple-junction cells made of germanium, gallium indium phosphide and gallium indium arsenide.
NREL's new cell includes two layers of gallium indium arsenide and one layer of gallium indium phosphide (see this graphic).
The laboratory has come up with a new process for making the cell that gets rid of the germanium wafer, instead growing the cell on a gallium-arsenide wafer, which is later removed.
According to NREL spokesman George Douglas, the process causes the atoms to bond in a different way, so they aren't lined up. This "mismatching," or staggering of the atoms, allows more light into the cells, making them more efficient.
With its high efficiency and probable high price tag, Douglas thinks the technology could be adapted for concentrating-solar power systems. Companies that build such systems are able to make up for higher costs by directing more sunlight into fewer cells -- and by getting high amounts of electricity from them.
But just how much of an improvement did NREL scientists make over the previous world-record holder? The answer is not much.
Spectrolab, the previous titleholder, announced it had achieved an efficiency of 40.7 percent in 2006.
While one-tenth of a percentage point might not sound like much of a difference, Douglas said it was significant in this case because it signals the potential for even higher efficiencies with more work.
NREL made the first of these cells less than a year ago, meaning that it has only begun to optimize their efficiency.
Spectrolab, for example, came out with a world record-setting triple-junction cell with 32 percent efficiency in 1999, and further improved the cell over seven years to reach the 40.7 percent record.
Of course, it will take some time to bring either of these efficiencies from the lab to the market.
According to Spectrolab's Web site, the company is producing solar cells for space with efficiencies reaching 29 percent. SunPower in 2006 announced its cells had reached 22 percent efficiency, the highest of any commercial cell, and this year said it plans to bring a cell with 23.4 percent efficiency to the market in about two years.
Other groups also are working to improve solar technology.
The day before the NREL announcement, the laboratory's controlling agency, the U.S. Department of Energy, said it would invest $24 million to develop "breakthrough" products to bring more solar electricity onto the grid.
According to the press release, the DOE will spend the money on projects with the potential to "significantly accelerate" the growth of photovoltaic solar power in the United States by making it more cost-effective.
The department has selected a dozen so-called Solar Energy Grid Integration Systems projects for the program, which will work to develop power conversion, energy storage and energy-management products, among others (see a list of participants here).
But the announcement is not the same as money in the bank.
The DOE said it will make the investments this fiscal year "and beyond" - the federal fiscal year ends Sept. 30 - but that the investments are subject to the availability of funds.
Meanwhile, Blaubeuren, Germany-based Centrotherm Photovoltaics said it would invest €10 million ($14.9 million) over two years to develop more efficient solar cells.
Using "a new, improved design" for the front and rear sides of solar cells, the company said it is aiming to produce multi-crystalline cells that can convert 16.5 percent of the light that strikes them into electricity and monocrystalline cells with efficiencies of at least 18 percent.
And according to another press release this week, Oerlikon Solar, which makes thin-film solar-manufacturing equipment, plans to open a new pilot line in Switzerland later this month. The company claims the new line will be able to handle all stages of the production of a thin-film solar panel.
Correction: An earlier version of this story misstated how the new cell is made.