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Monday, October 6, 2014

MIT Researchers make a perfect 'solar absorber':

The key to creating a material that would be ideal for converting solar energy to heat is tuning the material's spectrum of absorption just right: It should absorb virtually all wavelengths of light that reach Earth's surface from the sun -- but not much of the rest of the spectrum, since that would increase the energy that is reradiated by the material, and thus lost to the conversion process.

Now researchers at MIT say they have accomplished the development of a material that comes very close to the "ideal" for solar absorption. The material is a two-dimensional metallic dielectric photonic crystal, and has the additional benefits of absorbing sunlight from a wide range of angles and withstanding extremely high temperatures. Perhaps most importantly, the material can also be made cheaply at large scales.

The creation of this material is described in a paper appearing this week in the journal Advanced Materials , co-authored by MIT postdoc Jeffrey Chou, professors Marin Soljacic, Nicholas Fang, Evelyn Wang, and Sang-Gook Kim, and five others.

The material works as part of a solar-thermophotovoltaic (STPV) device: The sunlight's energy is first converted to heat, which then causes the material to glow, emitting light that can, in turn, be converted to an electric current. Some members of the team worked on an earlier STPV device that took the form of hollow cavities, explains Chou, of MIT's Department of Mechanical Engineering, who is the paper's lead author. "They were empty, there was air inside," he says. "No one had tried putting a dielectric material inside, so we tried that and saw some interesting properties."

Source: Science Daily