Cross-fertilized biomimetic structures achieved through nanosphere lithography on an ultrathin wafer for flexible black c-Si SHJ solar cells

Abstract

The millions of years of history of evolution are practically a history of optimization of all the biological designs and structures so as to cope up with nature and to get the best out of it. These natural designs can be exhaustive sources of readily available solutions for engineering and technological problems. Moth eye-like nanostructured anti-reflection coatings are an innovative concept for the fabrication of advanced and efficient solar cells due to its low reflection attributes when applied on the top of a cell. However, owing to its high surface area and low aspect ratio, the minority carrier life time and wide-angle light collection may be compromised, and these are treated as the major barriers of using such moth eye-like nanostructured anti-reflection coatingsin real cases. To overcome this problem, in this work, it has been aimed to introduce a ‘cross fertilized’ biomimetic structure between the ‘moth eye’ and ‘cacti’, so that maximum light can be utilized without much compromising the electrical properties. Detailed experimental and theoretical analyses on the optical and structural properties of such cross-fertilized nanostructures were carried out, giving emphasis on some crucial parameters like wide angle light collection, unified photon-electron harvesting capabilities, and surface recombination velocity. Finally, practical implementation of this optimized geometry has been carried out by the formation of ‘nano-cone’-based black c-Si structures through a metal-assisted chemical etching technique, followed by the fabrication of black p-c-Si/n-a-Si:H flexible solar cells.