There is still much work to be done, however, to turn the results and underlying concept into a viable solar cell. When light is absorbed by the quantum dots, electrons are generated, but the researchers still can’t control how those electrons travel through the layers. The team is working on modifying the system so that the electrons can be transported from the quantum dots to metal contacts to generate electricity. The team expects to have worked out the majority of the remaining challenges and to have a working cell within two years.
The “all-silicon approach” is more amenable to large-scale manufacturing than is using the more exotic materials for multilayered cells, says Ryne Raffaelle, professor of physics and director of the NanoPower Research Labs at the Rochester Institute of Technology, in NY. For many years, Raffaelle adds, researchers who have been looking toward the future of solar technology have been exploring inexpensive thin films and new materials. But, he says, if Green is successful, “silicon may rise once again to the pinnacle of [solar-cell] conversion efficiency.”
In an arena of technology that is filled with new approaches, solar-cell experts are taking a wait-and-see attitude about whether the initial optical experimental results will hold up in an actual device. “It will take a lot of work to realize the predicted high efficiencies” of the multilayered silicon quantum-dot cell, says Arthur Nozik, senior research fellow at the U.S. DOE National Renewable Energy Laboratory. But, he says, the concept is promising, and it’s a “very worthwhile research effort.”