Robust and durable polyhedral oligomeric silsesquioxane-based anti-reflective nanostructures with broadband quasi-omnidirectional properties

Abstract

Polymer-based anti-reflective coatings (ARCs) on glass pose major challenges for outdoor photovoltaic applications due to their incompatible mechanical and thermal properties. Here we demonstrate durable, chemically and thermally stable polyhedral oligomeric silsesquioxane-based (POSS) anti-reflective moth's eye nanostructures on glass fabricated by double-side nanoimprint lithography. These anti-reflective nanostructures exhibited excellent broadband and quasi-omnidirectional anti-reflective properties. An optimum resist composition for nanoimprinting was obtained by mixing a methacryl POSS cage mixture with 1,6-hexanediol diacrylate in a 1 : 12 molar ratio. Thermal free radical co-polymerization during nanoimprint lithography produced a uniform array of moth's eye nanostructures on both sides of a glass substrate with yields ∼90 to 100%. The transmittance of the resulting glass was enhanced to 98.2% (reflectance 1.26%) with excellent quasi-omnidirectional transmittance observed from −50° to +50° of angles of incidence. Furthermore, a series of ASTM-based tests on the imprinted ARC structures showed strong adherence to glass, better hardness and mechanical strength with superior chemical and thermal stability, thus suggesting their strong potential for commercial applications.