Formation mechanism of inverted pyramid from sub-micro to micro scale on c-Si surface by metal assisted chemical etching temperature

Abstract

Since challenges still exist in size control fabrication of inverted pyramids (IPs) on c-Si substrate, size difference of IPs among reported literatures still can not be explained reasonably. Here, formation mechanism of IPs from sub-micro scale to micro scale for light trapping on c-Si substrate is reported based on metal assisted chemical etching (MACE) temperature control for the first time. The formation of the IPs is realized through a mask-less Ag assisted wet chemical etching method followed by a post nanostructure rebuilding (NSR) process. It is found that the etching directions on (1 0 0) Si can be influenced by the MACE temperature due to the shrink of Ag nanoparticles at high MACE temperature, leaving behind few pore channels in the deepest region of black silicon layer as nucleation sites. Thus large IPs can be formed during the following NSR process. It is believed that the elucidation of the fundamental formation will speed up the fabrication of wafer-scale c-Si IPs for application in bulk and ultrathin c-Si solar cells.