The opto-electronic properties of the transition metal dichalcogenides (TMDs) are sensitive to their environment. For example, the presence of graphene in the vicinity of the TMDs modifies their exciton binding energy and the magnitude of the bandgap via external dielectric screening. At the same time, charge- and energy transfer determine the doping level of the TMD and the lifetime of excitations. By embedding TMDs into van der Waals heterostructures, their properties can thus be tailored in novel ways, which are complementary to traditional material engineering, such as substitutional doping.
Here, we will describe our advances in understanding the dielectric screening as well as the energy transfer in TMD – graphene heterostructures. We will discuss how the screening modifies the dispersion of the electronic bands and the exciton binding energy. We will discuss how heterostructures of TMDs, graphene and hBN spacer layers can be used to tune the screening and the energy-transfer times.