Integrated three-dimensional photonic nanostructures for achieving near-unity solar absorption and superhydrophobicity

Abstract

In this paper, we proposed and realized 3D photonic nanostructures consisting of ultra- thin graded index antireflective coatings (ARCs) and woodpile photonic crystals. The use of the integrated ARC and photonic crystal structure can achieve broadband, broad- angle near unity solar absorption. The amorphous silicon based photonic nanostructure experimentally shows an average absorption of similar to 95% for 400-620 nm over a wide angular acceptance of theta = 0 degrees - 60 degrees. Theoretical studies show that a Gallium Arsenide (GaAs) based structure can achieve an average absorption of > 95% for lambda = 400-870 nm. Furthermore, the use of the slanted SiO2 nanorod ARC surface layer by glancing angle deposition exhibits Cassie- Baxter state wetting, and superhydrophobic surface is obtained with highest water contact angle theta(CB) similar to 153 degrees. These properties are fundamentally important for achieving maximum solar absorption and surface self-cleaning in thin film solar cell applications. (C) 2015 AIP Publishing LLC.