Improved broadband and quasi-omnidirectional anti-reflection properties with biomimetic silicon nanostructures

Abstract

Nature routinely produces nanostructured surfaces with useful properties, such as the self-cleaning lotus leaf, the colour of the butterfly wing, the photoreceptor in brittlestar and the anti-reflection observed in the moth eye. Scientists and engineers have been able to mimic some of these natural structures in the laboratory and in real-world applications. Here, we report a simple aperiodic array of silicon nanotips on a 6-inch wafer with a sub-wavelength structure that can suppress the reflection of light at a range of wavelengths from the ultraviolet, through the visible part of the spectrum, to the terahertz region. Reflection is suppressed for a wide range of angles of incidence and for both s- and p-polarized light. The antireflection properties of the silicon result from changes in the refractive index caused by variations in the height of the silicon nanotips, and can be simulated with models that have been used to explain the low reflection from moth eyes. The improved anti-reflection properties of the surfaces could have applications in renewable energy and electro-optical devices for the military.

The role of random nanostructures for the omnidirectional anti-reflection properties of the glasswing butterfly

“…By optimizing the variance of the distribution and the shape of the pedestals, almost perfect antireflection surfaces can be engineered for a broadband range of wavelengths and a wide range of viewing angles. Such antireflective surfaces could be adapted to improve the light collection in solar cells or for an efficient light extraction of the substrate modes in light-emitting diodes or even enhancing the performance of the optical, optoelectronic and electro-optical devices, such as glasses, mirrors, lens, photodetectors, surface-emitting lasers, displays and optical sensing or imaging 20,21,[30][31][32] .…”

“…A master mould of these structures can be produced by advanced etching techniques 30 . Moulds replicated from such a master can be used for thermal nanoimprint 33 or hot embossing 34 to replicate glasswing structures on large scales.…”

Self-assembled antireflection coatings for light trapping based on SiGe random metasurfaces

“…Efficient anti-reflection coatings (AR) have been intensively studied with many different approaches having been explored for this purpose [1][2][3] , such as multi-layered thinfilms 4,5 , graded index matching via surface texturing with micro-and nano-structures [6][7][8][9][10][11] , plasmonic metasurfaces [12][13][14] and more recently, metasurfaces [15][16][17][18][19][20][21] based on ordered arrays of sub-micrometric dielectric antennas (dielectric Mie resonators [22][23][24][25][26][27][28] ). Depending on the application of the AR different aspects (lowest value of the total reflectance, broad spectral range, broad acceptance angle, transparency or light trapping) determine the optimal features and fabrication method.…”

Realization of Quasi‐Omnidirectional Solar Cells with Superior Electrical Performance by All‐Solution‐Processed Si Nanopyramids

“…Though photovoltaic sun tracking system is effective to solve the problem induced by the changed θ, it is costly and difficult to work precisely for more than 20–25 years of module lifetime 1. In recent years, there are lots of reports demonstrating that Si nanostructures possess outstanding broadband and omnidirectional antireflection ability, which are promising to be adopted in solar cells to form omnidirectional solar cells for enhancing electric energy output over broad θ 2, 3, 4, 5, 6, 7, 8, 9. For example, Spinelli et al2 have reported that Si nanocylinder arrays can effectively suppress reflection over the wide θ of 0°–60°.…”