Nanoparticle coating eliminates reflection from glass
Reflection of light off glass surfaces is a problem occurring in everyday life, and hinders the performance of solar panels, smart phone and tablet displays. Researchers from FOM Institute AMOLF have found a new and simple method to eliminate this reflection, by adding a silica nanopatterned antireflection coating to the device.
The reflection of light from a material is determined by the refractive index. Glass, a material commonly used in solar panels and displays, has a refractive index of 1.5 and reflects four percent of incident light at its surface. The reflectivity can be reduced applying an anti-reflection coating, which must have a refractive index of 1.2 in order to make a difference. However, materials with such a low index do not exist in nature.
The AMOLF team used soft-imprint technology to fabricate an array of nanoscale glass cylinders onto a glass substrate. The effective index of this coating is determined by the density of the glass cylinders and was made to match exactly 1.2. By doing so, the combined reflectivity of the two sides of the glass substrate was reduced from 7.4 percent to 0.6 percent. The low reflectivity is maintained over a large range of angle of incidence, up to 50 degrees.
Soft-imprint lithography uses a flexible rubber stamp that transfers a nanoscale pattern into a liquid silica solgel layer that is first spin-coated on the glass substrate. After drying, the nanocoating is robust and water repellant. The researchers applied the nanocoating on miniature solar panels and showed that their efficiency increases by 2.8 percent. They also show how the glare from a nano-coated smartphone screen is effectively eliminated.
Group leader Albert Polman: "These experiments are the proof-of-principle. The next step is to exploit the fact that nano-imprint lithography can be expanded to an industrial scale, and work with manufacturers of solar panels and displays to apply our new, patented technology."
Reference
Single-step soft-imprinted large-area nanopatterned anti-reflection coating, Jorik van de Groep, Pierpaolo Spinelli and Albert Polman, Nano Letters, DOI: 10.1021/acs.nanolett.5b01623
Contact
Albert Polman, +31 20 754 71 00.