Optimization and characterization of silicon nano-grass antireflection layer on textured silicon wafer

Abstract

We propose in this paper silicon nano-grass layer as an alternative of conventional black silicon nanowire structure. Conventional metal-assisted chemical etching process by HF produces porous silicon nanowire structure. This is due to uncontrollable chemical reaction making long-heighted nanowires which causes detrimental effect on further solar cell processing. The shape and height of silicon nanostructure was reduced by new chemical solution to minimize the porosity. Silicon nano-grass layer was grown on textured silicon surface and investigated in detail. The structure was formed by NH4F/H2SO4/H2O2 solution at room temperature. Substantial reflectance reduction with broadband spectral range was observed. The etching mechanism and the effect of etch constituents of the etching solution on the structure of nano-grass were studied elaborately. Reflectance and photoluminescence were studied accordingly, and the variations in the surface porosity and light absorbance property have been monitored. At the very end, a comparative study of conventional black silicon etching process by HF/H2O2 and nano-grass on textured silicon by NH4F solution has been investigated. The etch rate and the optical superiority of nanostructures formed by both the solutions have been manifested and explained. For the commercial production level, silicon nano-grass structure is much persistent than silicon nanowire.