Ultralow Index SiO<sub>2</sub> Antireflection Coatings Produced via Magnetron Sputtering.

Ruud, Christian J; Cleri, Angela; Maria, Jon-Paul; Giebink, Noel C · Nano Lett · 2022

basic_science · Level V

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Abstract

Antireflection (AR) coatings with graded refractive index profiles approaching air offer unparalleled AR performance but lack a scalable fabrication process that would enable them to be used more widely in applications such as architecture and solar energy conversion. This work introduces a sputtering-based sacrificial porogen process to fabricate multilayer nanoporous SiO<sub>2</sub> coatings with tunable refractive index down to <i>n</i><sub>eff</sub> = 1.11. Using this approach, we demonstrate a step-graded bilayer AR coating with outstanding wide-angle AR performance (single side average reflectivity in the visible spectrum ranges from 0.2% at normal incidence to 0.7% at 40°), good adhesion, and promising environmental durability. These results open up a path to produce ultrahigh performance AR coatings over large area by using industrial-scale magnetron sputtering systems.