Two-Dimensional MoS2-Graphene-Based Multilayer van der Waals Heterostructures: Enhanced Charge Transfer and Optical Absorption, and Electric-Field Tunable Dirac Point and Band Gap

Multilayer van der Waals (vdW) heterostructures assembled by diverse atomically thin layers have demonstrated a wide range of fascinating phenomena and novel applications. Understanding the interlayer coupling and its correlation effect is paramount for designing novel vdW heterostructures with desirable physical properties. Using a detailed theoretical study of two-dimensional (2D) MoS2-graphene (GR)-based heterostructures based on state-of-the-art hybrid density functional theory, we reveal that for 2D few-layer heterostructures, vdW forces between neighboring layers depend on the number of layers. Compared to that in the bilayer, the interlayer coupling in trilayer vdW heterostructures can significantly be enhanced by stacking the third layer, directly supported by short interlayer separations and more interfacial charge transfer. The trilayer shows strong light absorption over a wide range (<700 nm), making it great potential for solar energy harvesting and conversion. Moreover, the Dirac point of GR and band gaps of each layer and trilayer can be readily tuned by the external electric field, verifying multilayer vdW heterostructures with unique optoelectronic properties found by experiments. These results suggest that tuning the vdW interaction, as a new design parameter, would be an effective strategy for devising particular 2D multilayer vdW heterostructures to meet demands in various applications.