Antireflective properties of disordered Si SWSs with hydrophobic surface by thermally dewetted Pt nanomask patterns for Si-based solar cells

We have theoretically and experimentally investigated the antireflective properties of the disordered subwavelength structures (SWSs) with a hydrophobic surface on silicon (Si) substrates by an inductively coupled plasma (ICP) etching in SiCl4/Ar plasma using thermally dewetted platinum (Pt) nanopatterns as etch masks for Si-based solar cells. The Pt thin films on the SiO2/Si surface were properly changed into the optimized dot-like nanopatterns via the thermal dewetting by rapid thermal annealing process. The antireflection properties were definitely affected by the etched profile of SWSs which can be controlled by the conditions of etching process. For the tapered Si SWS with a high average height of 724 +/- 78 nm, the reflectance was significantly reduced below 5% over a wide wavelength range of 350-1030 nm, leading to a relatively low solar weighted reflectance of 2.6%. The structure exhibited reflectances less than 14.8% at wide incident angles of 8-70 degrees. The hydrophobic surface with a water contact angle of 113.2 degrees was obtained. For Si SWSs, the antireflective properties were also analyzed by the rigorous coupled-wave analysis simulation. These calculated results showed similar behavior to the experimental results. (C) 2011 Elsevier B. V. All rights reserved.