Anti-soiling surfaces for PV applications prepared by sol-gel processing: Comparison of laboratory testing and outdoor exposure

Nanoporous SiO2 antireflective films and films additionally incorporating larger particles in this matrix were prepared by sol-gel processing; the latter exhibits a randomly corrugated surface pattern. Both films show a significant anti-soiling effect versus standardized test dust materials of different particle size distributions. The surface coverages determined by laser scanning microscopy were correlated to the respective optical properties. These laboratory results were compared to long-term outdoor exposure experiments performed in the Kingdom of Saudi Arabia. A vast potential of sol-gel derived coatings for anti-soiling applications is demonstrated, nevertheless the high complexity of the particle-surface interaction mechanisms cannot be underestimated.