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 1.5GPa indent hardness and 35GPa 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.