Dual-functional broadband antireflective and hydrophobic films for solar and optical applications

We report hydrophobic modification of a high-performance broadband antireflective (AR) film comprising mesoporous MgF2 nanoparticles. The MgF2 film demonstrates high transmission, >99% (400-800 nm) and >97% (300-1500 nm) and is hydrophilic with a water contact angle of 27°. Hydrophobic modification with a fluorosilane containing silica sol by a simple dip coating process increases the water contact angle to 130° without affecting transmittance. Hence, this hybrid layer exhibits excellent anti-reflection in a broad wavelength range (98.8% (400-800 nm) and 97.03% (300-1500 nm)), along with good water-repellence. Moreover, the layer is also environmentally and mechanically stable indicating its suitability for solar and optical applications.