Self-Cleaning Antireflective Optical Coatings

TLDR

Low‑cost antireflection coatings on large optical surfaces are crucial for high‑performance solar cells, yet nanoporous thin films lack the robustness and cleanability needed for outdoor use. This study introduces a simple method to produce robust, self‑cleaning antireflective coatings. The technique employs self‑assembly of a block copolymer with silica sol‑gel chemistry and preformed TiO₂ nanocrystals, creating an inverse‑opal silica matrix loaded with TiO₂ photocatalytic hotspots while keeping the inorganic volume fraction low to preserve antireflective properties. The resulting coatings deliver high optical performance and self‑cleaning capability and can be applied to flexible plastic substrates.

Abstract

Low-cost antireflection coatings (ARCs) on large optical surfaces are an ingredient-technology for high-performance solar cells. While nanoporous thin films that meet the zero-reflectance conditions on transparent substrates can be cheaply manufactured, their suitability for outdoor applications is limited by the lack of robustness and cleanability. Here, we present a simple method for the manufacture of robust self-cleaning ARCs. Our strategy relies on the self-assembly of a block-copolymer in combination with silica-based sol-gel chemistry and preformed TiO2 nanocrystals. The spontaneous dense packing of copolymer micelles followed by a condensation reaction results in an inverse opal-type silica morphology that is loaded with TiO2 photocatalytic hot-spots. The very low volume fraction of the inorganic network allows the optimization of the antireflecting properties of the porous ARC despite the high refractive index of the embedded photocatalytic TiO2 nanocrystals. The resulting ARCs combine high optical and self-cleaning performance and can be deposited onto flexible plastic substrates.