Fabrication of pyramid/nanowire binary structure on n-type silicon using chemical etching

A pyramid and nanowire binary structure of n-type monocrystalline silicon surface was fabricated by two-step chemical etching process. The nanowire surface is formed by electroless etching in HF-AgNO₃ aqueous solution after being textured in KOH/IPA solution. Optical absorption was compared between this structure and that of random pyramid arrays. The effective reflectance calculated between 400 and 1100 nm decreased from ≈ 40% to ≈ 15% after pyramidal texturing and ≈ 4% after formation of vertically aligned nanowires with a length less than 1 μ m. This simple and low-cost surface structuring technique holds high potential for the manufacture of terrestrial silicon solar cells with reduced optical losses.