Dark materials based on graphene sheet stacks

The effective medium properties of graphene sheet stacks are calculated, and it is shown that such stacks can have very low reflectivity and high absorbance. These properties make graphene-sheet-stack-based materials darker than recently studied carbon nanotube materials. Graphene stacks thus hold promise for realizing lower reflectivity coatings and enhanced photodetectors. The bounds of the effective medium approximation and the possible benefits of using graphene sheet stacks in a regime where this approximation does not hold are discussed.