Researchers at MIT recently announced plans to create a “solar energy funnel” that could harvest energy from a much broader spectrum of sunlight than silicon photovoltaics are currently able to achieve. Ju Li, an MIT professor, and Xiaoteng Qian, a postdoc student, published a paper this week in Nature Photonics describing the funnel, which is made from a vanishingly thin material called Molybdenum Disulfide (MoS2).
Li and Qian’s solar energy funnel is much more sophisticated than your household funnel. The device is created by using a microscopic needle to poke a tiny hole in a thin film of MoS2 that is only a single molecule thick. This indents the surface and creates a funnel-like shape. The pressure exerted by the needle creates elastic strain, which is highest at the film’s center where it’s poked. The varying strain on the material created by this solar funnel changes the atomic structure just enough to “tune” different sections to different wavelengths of light – not just visible light, but also some of the invisible spectrum which happens to account for a great amount of the energy in sunlight.
MoS2 is a natural semiconductor and it has a special characteristic called bandgap that allows it to be converted into solar cells or integrated circuits. This characteristic, along with the solar funnel, gives this material the ability to respond to different colors of light in ways that silicon simply can’t. Qian says that in silicon-based organic solar cells, “it’s a diffusion process and it’s very inefficient.” But a solar funnel on MoS2 creates a focused “collection site [at the film’s center], which should be more efficient for charge collection.”
These solar funnels have only been tested through computer modeling so far, although researchers are hoping to carry out real-life lab experiments on MoS2 to confirm the solar funnel’s ability to efficiently convert solar energy into electricity.