Researchers working on the next generation of photovoltaic solar cells—cells that convert sunlight directly into electrical current—are looking toward exotic materials (which are expensive) or more common substances, but use subtler methods to extract energy. A new study used a basic semiconductor material, already in use in solar cell research, but made it into a set of wires in a brushlike structure. The key was making the wires’ diameter smaller than the wavelength of light, which exploited a resonant property to extract more energy than expected from the photons. In this way, the researchers achieved efficiencies comparable to normal (planar) solar cells.
In the new study, the researchers determined that two major factors dictated optimal performance: the diameter of the wire, and the conductive properties of the InP [indium phosphide]. From theoretical predictions, wires with diameters significantly less than visible-light wavelengths achieve resonance when the light strikes, vastly increasing the amount of energy that can be absorbed. The new model suggested peak efficiency would be reached with an nanowire diameter of 180 nanometers. [Read more…]