[amor de cosmos]

Stanford Report, October 31, 2012
Stanford scientists build the first all-carbon solar cell
Researchers have developed a solar cell made entirely of carbon, an inexpensive substitute for the pricey materials used in conventional solar panels.
By Mark Shwartz

Stanford University scientists have built the first solar cell made entirely of carbon, a promising alternative to the expensive materials used in photovoltaic devices today. The results are published in today's online edition of the journal ACS Nano.

"Carbon has the potential to deliver high performance at a low cost," said study senior author Zhenan Bao, a professor of chemical engineering at Stanford. "To the best of our knowledge, this is the first demonstration of a working solar cell that has all of the components made of carbon. This study builds on previous work done in our lab."

Unlike rigid silicon solar panels that adorn many rooftops, Stanford's thin film prototype is made of carbon materials that can be coated from solution. "Perhaps in the future we can look at alternative markets where flexible carbon solar cells are coated on the surface of buildings, on windows or on cars to generate electricity," Bao said.

The coating technique also has the potential to reduce manufacturing costs, said Stanford graduate student Michael Vosgueritchian, co-lead author of the study with postdoctoral researcher Marc Ramuz.

"Processing silicon-based solar cells requires a lot of steps," Vosgueritchian explained. "But our entire device can be built using simple coating methods that don't require expensive tools and machines."

http://news.stanford.edu/news/2012/o...ll-103112.html

Funneling the sun’s energy
MIT engineers propose a new way of harnessing photons for electricity, with the potential for capturing a wider spectrum of solar energy.
David L. Chandler, MIT News Office
November 25, 2012

The quest to harness a broader spectrum of sunlight’s energy to produce electricity has taken a radically new turn, with the proposal of a “solar energy funnel” that takes advantage of materials under elastic strain.

“We’re trying to use elastic strains to produce unprecedented properties,” says Ju Li, an MIT professor and corresponding author of a paper describing the new solar-funnel concept that was published this week in the journal Nature Photonics.

In this case, the “funnel” is a metaphor: Electrons and their counterparts, holes — which are split off from atoms by the energy of photons — are driven to the center of the structure by electronic forces, not by gravity as in a household funnel. And yet, as it happens, the material actually does assume the shape of a funnel: It is a stretched sheet of vanishingly thin material, poked down at its center by a microscopic needle that indents the surface and produces a curved, funnel-like shape.

The pressure exerted by the needle imparts elastic strain, which increases toward the sheet’s center. The varying strain changes the atomic structure just enough to “tune” different sections to different wavelengths of light — including not just visible light, but also some of the invisible spectrum, which accounts for much of sunlight’s energy.

http://www.mit.edu/newsoffice/2012/f...ergy-1125.html