'Darker-than-black' metamaterial could lead to more efficient solar cells

September 30, 2011 by Lisa Zyga

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When a hyperbolic metamaterial is
corrugated, its reflectance is greatly reduced and it becomes "darker
than black." Image credit: E. E. Narimanov, et al.

(PhysOrg.com) -- If typical black paint absorbs about 85%
of incoming light, then a newly designed metamaterial that absorbs up to
99% of incoming light may be considered “darker than black." By taking
advantage of the unique light-scattering properties of metamaterials,
researchers have discovered that a hyperbolic metamaterial with a
corrugated surface can have a very low reflectance, which could make it
promising for high-efficiency solar cells, photodetectors, and radar
stealth technology.

The researchers, E. Narimanov, et al., from Purdue University
and Norfolk State University, have posted their study on the
radiation-absorbing metamaterial at arXiv.org.

In their study, the researchers fabricated a hyperbolic metamaterial
out of arrays of silver nanowires grown in alumina membranes. They found
that this material absorbed about 80% of incoming light. Then, they
ground the surface of the metamaterial to produce corrugations and
defects, which they predicted would dramatically reduce the light
reflection, increasing the absorption. Their measurements showed that
the corrugated metamaterial absorbed up to 99% of incoming light, and
that the radiation-absorbing capability is applicable to all parts of
the electromagnetic spectrum.

As the scientists explained, the metamaterial’s very low reflectivity
results from one of its hyperbolic properties: an infinite density of
photonic states. This “super singularity” greatly increases the amount
of light scattering from surface defects and corrugations in the
metamaterial. The defects and corrugations scatter light primarily
inside the material, basically “sucking” photons inside the hyperbolic
medium.

The researchers predict that the new metamaterial will provide a new
route toward designing radiation-absorbing materials. As light
absorption plays a key role in solar cells and many other applications, the researchers plan to investigate these possibilities in the near future.

More information: E. E. Narimanov, et al. "Darker than black: radiation-absorbing metamaterial." arXiv:1109.5469v1 [physics.optics]


99% 이상 흡수하면 DTB라 카더라

DTB 들어가 있길래 그냥 퍼옴