Ultra-Broadband and Omnidirectional Perfect Absorber Based on Copper Nanowire/Carbon Nanotube Hierarchical Structure

Zero reflection and complete light absorption are required in a wide range of applications ranging from sensing devices to solar heaters and photoelectrodes. However, simultaneously satisfying the requirements of the broadband spectrum, omnidirectionality, polarization insensitivity, and scalability is very challenging. Combining the light-trapping characteristics of microscale copper nanowires (Cu NWs) with the unique optical properties of carbon nanotubes (CNTs), we experimentally demonstrate a novel perfect absorber that has an average total reflectance of 0.75% over the broad 400–1000 nm wavelength range and an average specular reflectance as low as 0.1%. Importantly, our cactus-like, hierarchical structure retains a similar performance independently of light polarization and for a broad range of incident angles. We furthermore developed a model that elucidates how the Cu NW and CNT components synergistically contribute to the suppression of both specular and diffuse reflections while maximizing light...