Tailored Light Scattering through Hyperuniform Disorder in Self‐Organized Arrays of High‐Index Nanodisks

Abstract

Arrays of nanoparticles exploited in light scattering applications commonly only feature either a periodic or a rather random arrangement of its constituents. For the periodic case, light scattering is mostly governed by the strong spatial correlations of the arrangement, expressed by the structure factor. For the random case, structural correlations cancel each other out and light scattering is mostly governed by the scattering properties of the individual scatterer, expressed by the form factor. In contrast to these extreme cases, it is shown here that hyperuniform disorder in self‐organized large‐area arrays of high refractive index nanodisks enables both structure and form factor to impact the resulting scattering pattern, offering novel means to tailor light scattering. The scattering response from the authors’ nearly hyperuniform interfaces can be exploited in a large variety of applications and constitutes a novel class of advanced optical materials.

Antireflective Huygens’ Metasurface with Correlated Disorder Made from High-Index Disks Implemented into Silicon Heterojunction Solar Cells

“…Details of our novel colloid-based nanofabrication method are documented in Methods and in previous publications. , We fabricated arrays of disks on top of the ITO front contact of flat heterojunction solar cells, as shown in Figure . Like-sized disks of 370 nm in diameter and 122 nm in height (Figure , left) cover the entire surface of the sample in a disordered dense pattern (Figure , center).…”

“…We have demonstrated the successful implementation of a TiO 2 dielectric disk-based disordered AR coating in solar cells of standard industrial design by using a scalable bottom-up technique. 18 Robustness of this deposition technique with respect to the surface morphology allows to avoid special preparation of the substrate, which, in addition to scalability, makes it an attractive technique to fabricate disordered particle coatings. Our measurements show significant reflection suppression in the spectral range relevant for solar cells, and we observe 5.1% rel improvement of the short-circuit current in comparison to a standard (optimized for AM1.5G irradiance) flat ARC reference device.…”

“…Details of the disk fabrication have been published elsewhere. 18 Briefly, it is based on self-organizing colloidal particles that are deposited onto a functionalized surface and the patterns thereof are subsequently transferred to a TiO 2 layer via RIE. On top of the front ITO layer, TiO 2 layers of 105.5 nm thickness were deposited via ALD at 120 °C using alternating pulses of titanium tetrachloride (TiCl 4 ) and water (1800 pulses each) in a Beneq TFS-200 thermal ALD tool.…”

“…and employ the first Born approximation 52 to calculate the scattering response of our disk layer. 18 In the far field, the scattered electric field of an individual scatterer has the form of a spherical wave 53 E r f E e r ( )…”

“…That challenge has been accepted, and a number of nanophotonic concepts have been proposed not only to improve light incoupling on the front interface, but for a much broader spectrum of objectives, including light trapping, spectrum splitting in tandem devices, or colored photovoltaics. − As building blocks, submicron-sized disks or pillar-shaped scattering elements have attracted a lot of attention during recent years because of their ability to support multipolar Mie resonances. , This allows to control the propagation of light in quite a drastic and deterministic manner. The shape of such submicron-sized disks (henceforth referred to as disks) can be tuned to carefully overlap electric and magnetic modes to control scattering characteristics. − Inspired by the original work of Kerker et al, complete suppression of back scattering can be achieved, making these disk-based Huygens’ metasurfaces ideal for use as antireflective coatings. − This bears the question of how to arrange the scattering elements. Disordered arrangements have been shown to possess a superior broadband response, − whereas periodic arrangements can be made entirely subwavelength, thereby suppressing all off-axis scattering .…”