Photocurrent Direction Control and Increased Photovoltaic Effects in All-2D Ultrathin Vertical Heterostructures Using Asymmetric h-BN Tunneling Barriers

Two-dimensional (2D) materials are atomically thick and without out-of-plane dangling bonds. As a result, they could break the confinement of lattice matching, and thus can be freely mixed and matched together to construct vertical van der Waals heterostructures. Here, we demonstrated an asymmetrical vertical structure of graphene/hexagonal boron nitride (h-BN)/tungsten disulfide (WS