Colloidal assembly to antireflection coatings

Antireflection (AR) coatings are widely used in reducing unwanted light reflection loss from optical surfaces. They are critical components for many important technological applications, such as improving conversion efficiencies of photovoltaic cells, enhancing light extraction efficiencies of light emitting diodes, and reducing glare from lenses. Traditional dielectric AR coatings rely on expensive top-down vacuum deposition technologies, which greatly impede the manufacturing cost and production throughput. Bottom-up colloidal assembly provides a much simpler, faster, and cheaper alternative to top-down approaches in fabricating high-quality AR coatings on a large variety of optical materials. In this book chapter, we will first review on the state-of-the-art of various AR coating manufacturing technologies, and then focus on three colloidal assembly platforms developed in our lab for scalably fabricating AR coatings on different optical substrates ranging from glass and plastics to crystalline silicon and GaAs. Langmuir-Blodgett assembly and electrostatics-assisted self-assembly of silica nanoparticles render simple and parallel approaches for making narrowband quarter-wavelength AR coatings on both planar and nonplanar optical surfaces. Spin coating of silica nanoparticles dispersed in a nonvolatile monomer enables wafer-scale production of colloidal crystals with unusual non-close-packed crystalline structures. The self-assembled nanoparticles can be used as structural templates in making bioinspired broadband moth-eye AR coatings, which can effectively suppress light reflection over a brand range of wavelengths and incident angles.