Energy and Charge Transfer in Heterobilayers formed by Transition Metal Dichalcogenides and Graphene

We report time-resolved measurements of Dexter-type energy transfer from transition metal dichalcogenide (TMD) monolayers to graphene monolayers by transient absorption measurements. Samples were fabricated by manually stacking together graphene monolayers and tungsten disulfide or molybdenum disulfide monolayers. Transient absorption measurements showed that the electron-hole pairs excited in the TMD layer transfer to graphene on a time scale shorter than the 100-fs laser pulses. Spatially resolved measurements revealed that the transfer is enhanced by an electric field, which indicates that the transfer is achieved by individual charge transfer of the electrons and holes. We further found that the transferred carriers can effectively alter the absorption coefficient of the TMD layer by screening effect. The observed ultrafast energy transfer from TMD monolayer to graphene and the control of TMD optical absorption by carriers in graphene suggest potential applications of TMD-graphene heterobilayers in optoelectronic devices.