Nano-and Micro-Engineered Vertical Graphene/Ni for Superior Optical Absorption

Black coatings benefit from low reflectance or high light absorption are utilized in multifarious optical applications. Due to their unique three-dimensional nanostructure and pi-band optical transitions, vertical graphene (VG) has drawn great attention to the field of black coatings. However, how the morphology of VGs affects reflectance has not been comprehensively disclosed yet. In addition, the morphology of the substrate for VG growth also affects the absorption properties. Here, we report a nano-and micro-engineered VG/Ni structure based on VG and laser-modified nickel foil, which possesses omnidirectional low reflectance of similar to 0.25% over the visible range. A larger spacing of graphene nanowalls is more conducive to the formation of light traps and improves the absorption property. Besides, the surface of nickel substrate by laser irradiation presents a "cauliflower-like" microstructure, which further enhances light-trapping ability.