Broadband low reflectance stepped-cone nanostructures by nanosphere lithography

The authors demonstrated broadband low reflectance through a two-step surface texturing technique that combines nanosphere lithography with dry-etching. Through this, various stepped-cone nanostructures were fabricated on the surface of GaAs to suppress its reflectance, with the shape and height of these nanostructures being precisely controlled by altering the diameter of the etch mask (SiO₂ nanospheres) and the etching time. The effects of this stepped-cone nanostructure were analyzed by measuring its reflectance spectra in conjunction with finite-difference time-domain calculations. This found that the average reflectance at wavelengths of 300-2500nm is reduced from 38.1% to 2.6% due to enhanced light scattering and a gradual change in refractive index. This novel method is therefore considered to represent an easily scalable approach to fabricating broadband antireflective surfaces for solar cell applications.