Biomimetic nano/micro double-textured silicon with outstanding antireflective and superhydrophilic surfaces for high optical performance

We report the fabrication of nano/micro double-textured silicon (NMDT-Si) and its structural, optical, and surface wetting properties. The micro-pyramidal textured (MPTs) are formed on the Si surface by a simple potassium hydroxide-based wet etching process. On the other hand, for pillar-arrayed nano-textures (NTs), the thermally-dewetted gold (Au) nanoparticles are employed on the surface of the MPT-Si as an etch mask and the inductively coupled plasma etching is followed. The optical reflectance of the NMDT-Si is strongly dependent on the period and height of NTs on the surface of the MPT-Si, which can be controlled by the Au film thickness and etching time, respectively. Compared with the planar nano-textured Si, the NMDT-Si shows superior antireflection (or higher light absorption) and light-scattered propagation behaviors, which are verified from a finite-difference time-domain simulation, over wide ranges of wavelengths (350-1100 nm) and incident angles (0-70 degrees), resulting in the average reflectance of similar to 2.1% and the solar weighted absorption of similar to 98.5% at normal incidence, respectively. In addition, it has a super-hydrophilic surface with water contact angles of < 5 degrees