Angle dependent antireflection property of TiO₂ inspired by cicada wings

Inspired by cicada wings, biomorphic TiO₂ with antireflective structures (ARSs) was precisely fabricated using a simple, inexpensive, and highly effective sol-gel process combined with subsequent calcination. It was confirmed that the fabricated biomorphic TiO₂ not only effectively inherited the ARS but also exhibited high-performance angle dependent antireflective properties ranging from normal to 45°. Reflectance spectra demonstrated that the reflectivity of the biomorphic TiO₂ with ARSs gradually changed from 1.4% to 7.8% with the increasing incidence angle over a large visible wavelength range. This angle dependent antireflective property is attributed to an optimized gradient refractive index between air and TiO₂ via ARSs on the surface. Such surfaces with ARSs may have potential application in solar cells.