Nanoporous films with low refractive index for large-surface broad-band anti-reflection coatings

Nowadays, nanoporous films are widely employed in biochemical applications or in opto-photonic devices such as displays, solar cells, or light-guiding systems. In particular, the technological feasibility of nanoporous layers with low refractive indices has recently enabled the development of high-efficiency anti-reflection coatings. In this paper, we report on hybrid polymer nanoporous films that can be fabricated in a single coating step with an industrial aqueous-based method on very large surfaces. Both high transparency and low refractive index are simultaneously achieved over the entire visible spectrum. We eventually demonstrate the potential of such films for broadband AR applications by combining them in a graded-index multilayer that reduces the surface reflectivity of a polymer substrate from 10% to few ‰