Here's how to make a powerful solar cell from nanowires: First, arrange microscopic flecks of gold on a semiconductor background. Using the gold as a foundation, build wires roughly 1.5 micron tall out of chemically tweaked compounds of indium and phosphorus using heat and vacuum pressure. Keep the nanowires in line by etching them clean with hydrochloric acid and confine their diameter to 180 nanometers. (A nanometer is one billionth of a meter.) Exposed to the sun, such a nanowire solar cell can turn nearly 14 percent of the incoming light into electricity—a new record for nanowire photovoltaics that opens up more possibilities for cheap and effective solar power.
According to research published online in Science—and validated at Germany's Fraunhofer Institute for Solar Energy Systems—this novel nanowire configuration delivered nearly as much electricity as thin-film versions, even though the nanowires covered only 12 percent of the device's surface. That achievement suggests such nanowire cells could prove cheaper—and more powerful—if the process could be industrialized, argues physicist Magnus Borgström of Lund University in Sweden, who led the effort.
The key will lie in developing even finer control of the nanowires as they grow and in chemically tweaking the constituent compounds. Borgström also hopes to simplify the production process by building the nanowires using simple heat and evaporation techniques, which should help further bring down the cost.
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