Scratch-resistant zeolite anti-reflective coating on glass for solar applications

Sol-gel SiO2 anti-reflection (AR) coating on solar glass is known to increase the current output by a few percent, but its mechanical durability is of concern. To improve its strength, the amorphous SiO2 may be replaced by zeolite, which is a microporous aluminosilicate crystalline material. Scratch-resistant AR coating has been prepared by the dip coating of a composition which contains aggregated zeolite nanoparticles as the structure provider and zeolite precursors as the reactive binder. AR coating with better than 5H pencil hardness can be made with a composition containing BEA zeolite. Nanoindenter measurements show that this BEA zeolite films have 1.5 GPa indent hardness and 35 GPa elastic modulus. Furthermore, the freshly prepared AR coating shows a self-cleaning effect with a water contact angle (WCA) close to zero. It can be made super-hydrophobic with larger than 130° WCA after modifying with hexamethyl-disilazane (HMDS), upon which the pencil hardness further increases to 6H.

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► Scratch resistant AR coating prepared from aggregated zeolite BEA nanocrystals.
► Better than 5H pencil hardness and <1% average reflectance.
► Indent-hardness > 1.5 GPa and elastic modulus >35 GPa.
► Water contact angle changes from ∼0° to 130° after hydrophobization.