Strong interference-based ultrathin conductive anti-reflection coating on metal substrates for optoelectronics

Anti-reflection layers, which comprise one or more films of dielectric or metallic materials, are widely used in many applications, such as solar cells, to reduce unwanted reflection loss or overcome undesirable color features. Many conventional anti-reflection layers are based on multilayer interference, index matching, surface texturing and plasmonic phenomena. Here, we present a novel paradigm that suppresses the reflection of light from a metallic surface by using an ultrathin, conductive CuO coating. This new anti-reflection concept relies on the strong inference inside the ultrathin, absorptive CuO coating. We derive the optimal conditions for minimal reflectance and expound how the film thickness impacts the reflectance. It is shown that zero reflectance can almost be obtained at a wavelength of ca. 550 nm over a wide range of incident angles. As a proof-of-concept experiment, a transparent conductive electrode with a record figure of merit was fabricated based on a CuO/Cu double-layer structure, of which CuO was used to tune the chromaticity of the resultant TCEs and protect Cu from oxidation. This technology has the potential for many applications, especially for photoelectrochemical cells, which can be used to simultaneously enhance the total absorption and reduce the minority charge carrier collection length. A simple material for reducing reflection from shiny surfaces has been developed by scientists in China. Reflection of light from a surface reduces the optical intensity transmitted to an underlying detector. Stacks of thin films on the surface can reduce reflection by making the backscattered light from each layer destructively interfere, but fabricating numerous layers with very precise thicknesses can be tricky. Now, Xiaoli Wang from the National Center for Nanoscience and Technology, Beijing, and co-workers have taken a different approach in which reflection is suppressed by harnessing the strong inference inside a single ultrathin layer of absorptive copper oxide. The thin copper oxide coating could improve the efficiency of optoelectronic devices such as solar cells. The team demonstrated the potential of their approach by constructing transparent conductive electrodes, which are needed in optoelectronics. we present a novel paradigm that suppresses the reflection of light from a metallic surface by using an ultrathin CuO coating. This antireflection concept relies on the strong inference inside the ultrathin absorptive CuO coating. We derive the optimal conditions for minimum reflectance and expound how the film thickness impacts the reflectance. Almost zero reflectance can be obtained at wavelength of ca. 550 nm over a wide range of incident angles. This technology has the potential for many applications, especially viable for photoelctrochemical cells, which requires strong absorption and short carrier collection length.