  We demonstrate a nanopatterning technique for silicon photovoltaics, which
optically outperforms conventional micron-scale random pyramids, while
decreasing by a factor of ten the quantity of silicon lost during the texturing
process. We combine hole-mask colloidal lithography, a bottom-up
nanolithography technique, with reactive ion etching to define nanopyramids at
the surface of a silicon wafer. Thanks to the self-organised aspect of the
technique, the beads are randomly distributed, however keeping a interbead
distance of the order of their diameter. We tune the nanopattern feature size
to maximize the absorption in the crystalline silicon by exploiting both
anti-reflection and light trapping. When optimized, the nanopyramids lead to a
higher absorption in the crystalline silicon than the conventional micron-scale
random pyramids in the visible and near the band edge, with a superior
robustness to variations of the angle of the incident light. As the
nanopatterning technique presented here is simple, we expect that it could be
readily integrated into the crystalline silicon solar cell fabrication
processing.
