Trapping Sunlightwith Silicon Nanowires

Trapping Sunlightwith Silicon Nanowires

While there are now silicon photovoltaics that can convert sunlight into electricity at impressive 20 percent efficiencies,the cost of this solar power is prohibitive for large-scale use.Researchers are developing a new approach that could substantially reduce these costs. The key to their success is a betterway of trapping sunlight.Because of its superior photo-electronic properties,silicon remains the photovoltaic semiconductor of choice but rising demand has inflated the price of the raw material. Furthermore,because of the high-level of crystal purification required,even the fabrication of the simplest silicon-based solar cell is a complex,energy-intensive and costly process. The researchers are now able to reduce both the quantity and the quality requirements for silicon by using vertical arrays of nanostructured radial p-n junctions rather than conventional planar p-n junctions. In a radial p-n junction,a layer of n-type silicon forms a shell around a p-type silicon nanowire core.As a result,photo-excited electrons and holes travel much shorter distances to electrodes,eliminating a charge-carrier bottleneck thatoften arises in a typical silicon solar cell.The radial geometry array also,asphotocurrent and optical transmission measurements by the researchers revealed,greatly improves light trapping.

(From:Light Trapping in Silicon Nanowire Solar Cells)