Single component: Bilayer TiO2 as a durable antireflective coating

Presently, assembling antireflective coatings (ARC) on diverse surfaces have been intensively explored for the preparation of functional nanocoatings, which are tremendously favored and required on optical devices. Broadband ARC characteristically obtains the AR purpose via low refractive index (i.e., SiO2 [1.4] or MgF2 [1.32]). However, the developed photocatalytic coatings comprise high refractive index materials (TiO2 similar to 2.0). Regardless of fabricating a composite compatible AR coating, Herein, a single component ARC comprising two layers were fabricated. A bilayer TiO2 antireflective coating (BT@ARC) based on porous nanorods (eta similar to 1.38) and dense TiO2 layer (eta similar to 2.45) have been fabricated via physical vapor deposition attaining negligible reduced reflectance over the desired wavelength region beside tunability. The present strategy is practically applicable to different transparent and semitransparent substrates with varying refractive index (eta) from 1.41-3.4. The result proves that fabricated BT@ARC exhibits omnidirectional antireflectance with thermal stability up to 300 degrees C. Annealing significantly enhances the mechanical adhesion strength and robustness of BT@ARC. The BT@ARC also passes the salt brine test, exposure to negative temperature showing AR durability. The BT@ARC also shows organic dye degradation due to its photoactive and self-cleaning nature. Thus this practically applicable approach opens a new path in future technology using a single component material in ARC. (C) 2020 Elsevier B.V. All rights reserved.