Antireflection coatings from nano-scale silicon cylinders

A concept for antireflection coatings based on nanocylinders is demonstrated in Nature Communications this week. These silicon-based structures offer potential for reducing reflections from a large number of materials, which makes them promising for a number of optical devices, including solar cells. Eliminating reflection is crucial for optical and optoelectronic devices if they are to maximise their use of incident light. Many schemes exist, but they often only work over narrow wavelength ranges. Albert Polman and colleagues demonstrated an antireflection layer based on an array of silicon nanocylinders on a silicon wafer. The tiny cylinders act as efficient scatterers, which are strongly coupled to the surface they are placed on. This produces preferential scattering of the light towards the wafer instead of away from it. They found an average reflectivity of 1.3% across the visible spectrum and into the near-infrared range. The transmission through the layer also approaches 100% at longer wavelengths. The high transmission and low reflection of these nanocylinder coatings may offer an efficient route to improving the coupling of light into all manner of optoelectronic devices.