Semiconductor Nanowires for Next Generation Solar Cells

Nanowires are filamentary crystals with a tailored diameter in the submicron range. This particular morphology has improved existing and inspired many novel applications such as biosensors 1, high mobility transistors, lasers 2,3 and solar cells 4. The one dimensional nature of nanowires is especially relevant for solar cells. First, by fabricating radial pn junctions in otherwise standing nanowires it is possible to decouple light absorption from carrier collection, see Fig. 1a 5,6. Second, it has been shown that careful design of the nanowire diameter leads to absorption cross sections about one order of magnitude larger than their physical section 7. As a consequence, semiconductor nanowires act as nanoscale light concentrators, thereby opening a new path for surpassing the Shockley Queisser limit in single junction solar cells. Recently, careful design of the nanowire diameter and spacing has led to a 13.8% efficiency device8.