Nature Nanotechnol.http://dx.doi.org/10.1038/nnano.2012.166 (2012)

Although photovoltaic devices based on silicon nanostructures are expected to provide excellent power-conversion efficiencies, they have not yet been able to out-perform conventional cells. This shortcoming is due partly to a lack of understanding regarding the mechanisms involved in the charge recombination processes. Jihun Oh and researchers from Colorado in the USA have now demonstrated an 18.2%-efficiency 'black silicon' nanostructured cell that not only absorbs a high percentage of incident light but also suppresses unwanted recombination processes. By varying the diffusion time of a phosphorus dopant, the researchers identified two parallel charge recombination channels that dominated under different conditions. They found that the Auger recombination channel dominated under high doping, whereas the surface recombination channel dominated under low doping. Between these two levels, both channels contributed to photocarrier recombination. The researchers report that, contrary to popular belief, it is the Auger recombination process that limits the efficiency of most nanostructured silicon solar cells.