Speed Bumps for Sunlight Could Improve Solar Cells

Most research in photovoltaics (PV) works by coaxing our materials to respond differently to sunlight. But what if we could change the light instead? Scientists at the Massachusetts Institute of Technology (MIT) are trying to do just that by slowing down the speed of light using nanomaterials.

Working with researchers at Zehjiang University, Taiyuan University, and the University of Illinois–Urbana-Champaign, they have developed a new ultra-thin nanotech metamaterial that slows light in order to absorb it more effectively. As they explain in “Ultrabroadband Light Absorption by a Sawtooth Anisotropic Metamaterial Slab,” metamaterials are custom-engineered at the atomic level for specific purposes and can be fabricated with standard PV-cell manufacturing equipment.

MIT’s design involves wedge-shaped ridges of different widths; at various depths, the ridges slow light of specific wavelengths to less than 1/100 of its normal speed, selectively enhancing absorption of those wavelengths. This enhanced absorption could greatly increase the efficiency of solar cells, and the material’s efficiency at emitting electromagnetic radiation of particular wavelengths could lead to light bulbs with far lower energy consumption.