Nanostructured pyramidal black silicon with ultra-low reflectance and high passivation

Abstract

In this study, nanostructured pyramidal black silicon is prepared by metal assisted chemical etching method, in which the silver nitrate (AgNO3) is used as the metal catalyst. Effects of the concentration of AgNO3 on passivation and optical properties of the black silicon are investigated. The experimental results show that at the AgNO3 concentration of 0.03 M, the nanostructure length is about 300 nm, and the reflectance of the black silicon with a stack of silicon nitride (SiNx) and aluminum oxide (Al2O3) is 0.8%, which is comparable to that of the conventional black silicon with micrometer-long nanowires. In addition, an acceptably low surface recombination rate of 42 cm/s can be obtained. Plasma chemical vapor deposited SiNx is deposited well on the top of nanostructures of black silicon, but shows poor coverage at the bottom region. Spatial atomic layer deposited Al2O3 can conformally cover the nanostructures with high passivation quality. Simulation result indicates an improvement of 5.5% of conversion efficiency for the nanostructured pyramidal black silicon solar cell compared to industrial silicon solar cell. The short nanostructured pyramidal surface with low reflectance and high passivation is expected to be helpful for black silicon technology applied to photovoltaic applications.