Textured stainless steel foil as efficient rear reflector for flexible black silicon

Abstract

This paper reports textured SS foil as an efficient rear reflector for flexible b-Si. Wafer thinning by concentrated potassium hydroxide (KOH) solution followed by metal-assisted chemical etching (MACE) are used to fabricate the flexible b-Si with 67 μm thickness. After the MACE process, the b-Si exhibit nanowires (NWs) with average diameter of 100 nm and height of 1.25 µm. To texture the stainless steel (SS) foil, wet chemical etching involving hydrofluoric (HF) acid (49%) is used at room temperature for different durations; from 10 to 30 min. When increasing the etching time of the SS foil, the SS foil exhibits formation of random textures with the roughest morphology after being etched for 20 min. At the same etching time, the SS foil also shows the highest root mean square (RMS) surface roughness and peak texture angle with a broad angle distribution. With the textured SS foil, the flexible b-Si demonstrates absorption enhancement of 1.27 at wavelength of 1075 nm due to the enhanced light scattering at the b-Si/textured SS interface.