Aluminium-assisted chemical etching for fabrication of black silicon

Abstract

This paper investigates aluminium-assisted chemical etching (AACE) process to fabricate b-Si absorber for the first time. The AACE process combines deposition of a thin aluminium (Al) film with thickness of 12–30 nm on crystalline silicon (c-Si) wafers, followed by subsequent thermal annealing and wet chemical etching processes. The AACE process produces random nanopores on the b-Si surface. From the results, thicker Al thickness leads to lower depth of nanopores, lower surface coverage of nanopores on the b-Si and exhibits higher weighted average reflection (Ravg) within 300–1100 nm wavelength region. The b-Si fabricated by Al film of 12 nm thickness demonstrates the lowest Ravg (11.9%) and the highest broadband light absorption. The b-Si reveals nanopores with average depth of 200 nm and surface coverage of 45.1%. The findings from this work demonstrate the potential of the AACE process to produce b-Si with superior broadband light absorption, which is crucial for photovoltaic (PV) applications.