Scalable parallel self-assembly of nanoparticle anti-reflection coatings

Here we report a simple, inherently parallel, and scalable bottom-up approach for fabricating nanoparticle anti-reflection coatings on large glass substrates. Negatively charged silica nanoparticles are electrostatically adsorbed onto a surface-functionalized glass substrate with positive surface charges to form a disordered monolayer nanoparticle coating. Systematic experiments have been conducted to optimize the critical process parameters, including the dispersing dielectric media, nanoparticle concentration of the colloidal suspensions, and the coating time, that significantly affect the uniformity and the anti-reflection properties of the final coatings. Specular reflection and transmission measurements demonstrate that good anti-reflection performance (with < 1% two-sided reflection) and high optical transmission (> 99%) can be achieved by the self-assembled nanoparticle coatings. This innovative technology also enables the simultaneous coating of multiple 5-in.-sized glass substrates with high and reproducible qualities. Importantly, we combine experiments with theoretical calculations to address a fundamental question faced by the fabrication of monolayer nanoparticle-based anti-reflection coatings — what is the optimal nanoparticle surface area coverage for best anti-reflection performance? Our optical simulations based on a rigorous coupled-wave analysis model indicate that the optimal nanoparticle coverage is ~ 60% which is readily achievable by this electrostatics-assisted bottom-up technology.