Researchers at Stanford University, United States, have demonstrated that a set of metamaterials can enable solar cells to use a band of the solar spectrum that would otherwise go to waste. These materials could convert red and near-infrared light into shorter-wavelength light that the cells can turn into energy. The best silicon solar cells of today can’t use about 30 percent of the light from the sun because the active materials in the cells can’t interact with photons whose energy is too low. Being able to tap that energy would, however, make solar cells more cost-competitive. Jennifer Dionne, an assistant professor and leader of the group, believes that their process of “upconversion” could improve the sunlight-to-electricity conversion efficiency of amorphous-silicon solar cells from 11 percent to 15 percent. Dionne is using metal nanoparticles that act like tiny optical antennas to make better upconversion systems. The university researchers are collaborating with the Bosch Research and Technology Center in Palo Alto, California, to demonstrate a system in working solar cells in the next four years, with the hope that this technology could be in Bosch’s commercial solar cells in seven to 10 years.
http://www.technologyreview.com/energy/37994/