Effects of etching time towards broadband absorption enhancement in black silicon fabricated by silver-assisted chemical etching

Abstract

This paper presents investigation on the effects of etching time towards broadband absorption enhancement in black silicon (b-Si) fabricated by silver-assisted chemical etching. The c-Si wafers are deposited with a thin silver (Ag) layer and annealed in a nitrogen (N2) atmosphere to form Ag nanoparticles (Ag NPs). The wafers are then etched in an aqueous solution of HF:H2O2:H2O at room temperature at different etching times to form the b-Si. All the b-Si wafers show rough surface morphology due to the presence of nanotextures. The b-Si exhibit wafers exhibit significantly lower broadband reflection compared to a planar c-Si reference. The c-Si wafer etched for 70 s demonstrates the lowest broadband reflection, with reflection of 3% at wavelength of 600 nm (i.e. absorption of 97%). This sample exhibits b-Si nanotextures with width of 50–100 nm and height of 300–400 nm. The enhanced broadband light absorption in the b-Si leads to maximum potential short-circuit current density (Jsc (max)) of 39.7 mA/cm2, or 51% enhancement compared to a planar c-Si reference, calculated for wavelength region of 300–1100 nm.