There's a limit on the conversion efficiency of a conventional solar cell. No matter how it's tweaked, it can only convert 31 percent of the light that hits it into usable electrical current. That's because there's a broad spectrum of wavelengths in sunlight, and some of it has more energy than the active material in the solar cell can handle. High-energy light hits the active material in a solar cell and knocks loose electrons that have a similarly high energy--then these electrons rapidly lose that excess energy as heat.

Physicists know that if they could capture "hot electrons", they could more than double the efficiency of solar cells. The problem is that they lose their energy in a picosecond. Now, researchers have for the first time demonstrated that it's possible to capture hot electrons while they're still in their high energy state, before that heat loss happens.

Careful design at the nanoscale is key. Instead of a conventional bulk semiconductor, the researchers used quantum dots, because these nanomaterials can confine electrons over a longer timescale. "Nanomaterials can keep electrons electrons hot for a longer period of time, so that you can get them out," says Xiaoyang Zhu, professor of chemistry at the University of Texas, Austin.

The confinement is great--until you want to get the hot electrons out. "The electron likes to stay inside the nanomaterial, so you need to make an extremely strong interaction with another material" that will conduct the electrons out of the quantum dot, Zhu says. His group coated the quantum dots with a very thin layer of an electrical conductor, and were meticulous about the quality of the interface between that material and the quantum dots.

So now it's possible to get hot electrons out, but one major problem remains. Those hot electrons require new device designs that prevent them from simply losing their energy to heat once they enter the metal wire of an electrical circuit. "We hope to inspire people to work on the engineering," says Zhu.

This research was published this week in the journal Science.

SXSW is a marathon event, from the Interactive conference to the music festival--and it can be hard to keep all your gadgets charged and running.

So the conference organizers have collaborated with Austin-based Sol Design Lab to make the firm's SolarPumps available at locations around downtown Austin.

The SolarPump is a free, solar-powered charging station for electric bikes, scooters, cell phones, and laptops--basically anything that uses a standard electric cord to charge. Beth Ferguson created the pump in February 2009 as her project for her MFA at the University of Texas at Austin. Ferguson combined the reclaimed body of a 1950's gas station pump with solar panels to get people thinking about solar energy.

"We've used kind of a fun combination of 1950's gas pumps with solar panels for people to really start questioning and seeing the humor and really start thinking about a new form of transportation and energy for the city," she told Austin's KVUE News.

The SolarPump combines 1950s vintage gas pumps with solar panels to create an electronics-charging station. © Sol Design Lab

A private investment group called Teanaway Solar Reserve says that it plans to build a massive 75-megawatt solar facility that will sprawl over some 400 acres in Cle Elum, WA, a rural area about 80 miles east of Seattle. The solar farm will be by far the largest in the Northwest, and much larger than any existing photovoltaic plant anywhere. (A 60-megawatt plant in Spain now holds the world record, while a 14-megawatt photovoltaic facility at Nellis Air Force Base, in Nevada, is the largest photovoltaic facility in the United States.) However, the solar facility in Washington is only one of several larger photovoltaic plants that have been recently announced, including several in California that would exceed 200 megawatts; a 60-megawatt plant is planned for Chicago.

Washington appears to be an odd location for a solar plant. While central Washington is, unlike Seattle, actually quite sunny--Howard Trott, Teanaway's managing director, estimates that the location has 300 sunny days a year--it is also home to some of the country's cheapest electricity because of its hydroelectric capacity. However, Trott says, Washington's consumers will favor photovoltaic-generated electricity because it is "very green," and they will pay a premium for it, "which will make us profitable."

Trott declined to disclose many financial details of the project or his company except to say that the costs of the solar farm will likely "run north of a hundred million." His plan calls for a solar producer to build a manufacturing facility at the site to provide the 400,000 panels that the solar farm will need. Trott, who acknowledges that he has no previous experience in the solar industry, says that it has not yet been decided whether the new solar facility will use conventional silicon solar cells or thin-film photovoltaics. Indeed, it is still very early days for the private solar company and its Washington project. Says Trott: "Yesterday, we rented an office."