Water Impact Resistant and Antireflective Superhydrophobic Surfaces Fabricated by Spray Coating of Nanoparticles: Interface Engineering via End-Grafted Polymers

Abstract

Fully transparent and water impact resistant superhydrophobic coatings are of great importance for a range of applications including photovoltaics, photonics, automotive windshields, and building windows. A widely utilized approach to fabricate such coatings involves solution-based deposition of hydrophobic nanoparticles. A central challenge is that these coatings do not simultaneously offer high levels of water repellency, perfect transparence, and water impact resistance. Here we demonstrate that end-grafted polymers present excellent interfaces for spray-coated hydrophobic nanoparticles and enable fabrication of water impact resistant and antireflective superhydrophobic coatings (SHPARCs). Depending on the backbone chemistry and thickness, end-grafted polymers uniquely interacted with the fluorinated nanoparticles, resulting in nanostructured films that provided reduction of reflective losses and protection from the impact of water droplets. Counterintuitively, substrates modified with end-grafted hydrophilic polymers exhibited high water impact resistance: the sliding angle of SHPARC on 12 nm thick end-grafted poly(ethylene glycol) layer was <2 degrees after exposure to 100000 water droplets. SHPARC increased the transparency of the glass substrate by similar to 5% through omnidirectional antireflectivity. We finally demonstrate application of SHPARC on a large area (156 x 156 mm(2)) silicon solar cell without significant (<0.23%) reduction of the power conversion efficiency, illustrating the promise of the presented approach in fabrication of self-cleaning photovoltaic modules.