Mechanically robust and self-cleaning antireflection coatings from nanoscale binding of hydrophobic silica nanoparticles

Antireflection coatings from silica nanoparticles exhibit promising applications in many energy-related areas such as solar-thermal and photo-voltaic systems. However, the coatings suffer from poor mechanical durability and low self-cleaning capability in outdoor conditions, which limit their practical application. Here, we create mechanically robust and self-cleaning antireflection coatings through nanoscale binding of hydrophobic silica nanoparticles with an organosilica binder. The coatings demonstrated nearly full transmission at desired wavelength of similar to 550 nm, with peak transmittance up to 99.9%. Further advantage of these coatings is the combination of hydrophobic silica nanoparticles with the organosilica binder, resulting in hydrophobic and mechanically robust coatings, with water contact angle of 161 degrees and hardness of 4.2 GPa. The coatings maintained their high transmittance under outdoor conditions for 3 months, which is largely attributed to their self-cleaning functionality resulting from super-hydrophobicity. We envision that the mechanically robust and self-cleaning antireflection coatings could find wide applications in outdoor conditions and other harsh environments.