Ultrafast charge transfer in graphene-WS2 Van der Waals heterostructures

By using a graphene layer as fast carrier combination channel for WS2. Graphene-WS2 heterostructures be used as an example to study the charge transfer across the interface via transient absorption measurements. We found the transfer of photo-induced carriers from WS2 to graphene take place within 83 fs, this ultrafast transfer time supports the charge transfer mechanisms via layer-coupled states and Coulomb field. Our results provide the basic information for understanding the photo-induced carriers transfer across the interfaces of van der Waals heterostructures and suggest that van der Waals heterostructures may be useful in ultrafast optoelectronic devices.