Researchers around Koray Aydin, Northwestern University, USA, used metal and silicon oxide to create ultrathin (260 nm) but complex, trapezoid-shaped metal gratings on the nanoscale that can trap a wider range of visible light. The uniquely shaped grating captured a wide range of wavelengths (400–700) due to the local optical resonances, causing light to spend more time inside the material until it gets absorbed. The design of nanostructured ‘black’ super absorbers from materials comprising only lossless dielectric materials and highly reflective noble materials represent a new research direction.

The composite metamaterial was also able to collect light from many different angles – a useful quality when dealing with sunlight, which hits solar cells at different angles as sun moves throughout the day.

Metal and silicon oxide cannot convert light to electricity. But if the innovative trapezoid shape could be replicated in semiconducting materials that could be used in solar cells. Then the technology could lead to thinner, lower-cost, and more efficient solar cells.

• Broadband polarization-independent resonant light absorption using ultrathin plasmonic super absorbers,
  Koray Aydin, Vivian E. Ferry, Ryan M. Briggs, Harry A. Atwater,
  Nature Communic. 2011.
  DOI: 10.1038/ncomms1528