Interface design for the optimal optoelectronic conversion properties of MoS2/WS2/WSe2 van der Waals heterostructures

The interfacial nature of few-layer transition metal dichalcogenide (TMD)-based van der Waals heterostructures (vdWHs) plays a vital role in their optoelectronic properties and can greatly influence charge transfer and recombination. Here, we consider a trilayer MoS2/WS2/WSe2 vdWH with ladder band alignment and address the relationship between the interface character and optoelectronic properties in terms of the atomic-bond-relaxation approach, Marcus theory, and the detailed balance principle. We find that a trilayer vdWH with ladder band alignment exhibits ultrafast interface charge transfer, and the interface barrier induced by the middle WS2 layer can significantly suppress interlayer recombination. The power conversion efficiency (PCE) of trilayer MoS2/WS2/WSe2 vdWHs can reach 2.43%. Our findings show that the PCE of MoS2/WS2/WSe2 vdWHs is obviously better than that of bilayer heterostructures, suggesting that the design of ladder band alignment can be an effective way to achieve highly efficient TMD-based photovoltaic devices.