Vertical graphene sheets as a lightweight light absorber

Abstract

We report the optical properties and solar reflectance of catalyst-free vertical graphene (VG) sheets grown on two types of substrate, copper and silicon, over a wide range of wavelengths and for the first time, a method for the separation of the sheets from the substrate. The index of refraction of the VG sheets was close to unity in the visible and infrared range, while the coefficient of absorption was higher than those of forests of carbon nanotubes (CNTs). A total reflectance (diffuse and specular) of less than 10% was observed for the VG sheets in the visible range. For VG sheets grown on a copper substrate, the specific absorption (absorption divided by the areal density) at a wavelength of 633nm was measured to be two times higher than previously reported results for VG sheets grown on a silicon substrate and much higher than that of a CNT forest.