Enhanced durability transparent superhydrophobic anti-soiling coatings for CSP applications

Optically transparent superhydrophobic (SH) coatings based on multifunctional silica nanoparticles and polymeric binders were developed and their optical and abrasion resistance properties were studied. Three key factors are emphasized: i) The optical clarity of the coatings. Particle deagglomeration and surface functionalization techniques were developed to obtain particle size distributions with an average size smaller than 200 nm. The particles were uniformly dispersed in organic binders and resulted in coatings with an average roughness value smaller than 30 nm. The nano-sized particles do not scatter light at wavelengths > 250 nm because of their small dimensions. ii) Enhanced particle-binder interfaces. We have introduced a double functionality on the particle's surface in order to partially crosslink them with the polymeric binder. This multifunctional configuration significantly improves the abrasion resistance of the coatings without degrading their SH properties. iii) Accelerated weathering durability. Coatings were subjected to simulated solar UV exposure. Our ongoing studies indicate that the coatings are environmentally durable over several years of simulated UVA exposure. The nanostructure-property interdependencies underlined in the above three key factors are utilized in the development of transparent SH coatings with enhanced durability.