  Silicon inverted pyramids arrays have been suggested as one of the most
promising structure for high-efficient ultrathin solar cells due to their
ability of superior light absorption and low enhancement of surface area.
However, the existing techniques for such fabrication are either expensive or
not able to create appropriate structure. Here, we present a lithography free
method for the fabrication of inverted pyramid arrays by using a modified metal
assisted chemical etching (MACE) method. The size and inter-inverted pyramids
spacing can also be controlled through this method. We used an isotropic
chemical etching technique for this process to control the angle of etching,
which leads to ultra-low reflection, even < 0.5%, of this nanostructure. Using
this specification, we have predicted the expected solar cell parameters, which
exceeds the Lambertian limit. This report provides a new pathway to improve the
efficiency of the ultrathin silicon solar cells at lower cost.
