Imagine a baseball game in which the pitcher throws balls in all directions, not just over home plate. Today's solar panels are like batters in that baseball game: patiently waiting until a ball comes their direction at the right speed to make a hit.
This is because normally light, and heat*, radiate in all different directions. So the first solar panel to bat at the game where the pitcher always throws the ball straight over home plate, and even at exactly the same speed each time, will be a superstar.
This vision could be part of our energy future thanks to scientists at Australian National University, especially Dr. Sergey Kruk, who predicted a material that would have the amazing properties the team was seeking. The ANU team turned to the University of California Berkeley, where the technical facilities to build Dr. Kruk's metamaterial could be found.
At UC Berkeley, they built up alternating thin layers of gold and magnesium fluoride on a silicon nitride membrane, then milled these with a focused ion beam into the "multilayer fishnets" depicted in the image. This metamaterial is so small that 12,000 building blocks fit on the cross-section of a human hair.
Tests proved what Dr. Kruk predicted: this metamaterial can interact with the magnetic component of light (or heat waves which are just another form of light that is outside of the range our eyes evolved to detect), to radiate the waves in a specific direction, and even in a limited range of wavelengths.
This makes the material ideal for pairing with thermophotovoltaic cells, which convert heat into electricity. With the metamaterial serving up light, or even heat (so it works in the dark!), and thermophotovoltaics optimized to receive the appropriate specific wavelengths, efficiency breakthoughs are bound to follow.
Build it and they will come.
The open access article, Magnetic hyperbolic optical metamaterials, can be read in Nature Communications.
Additional image credit: iamme ubeyou
* Technically "thermal radiation"