| Recently,the van der Waals（vdW）heterostructures based on two-dimensional transition metal dichalcogenides（TMDs）have shown great application potential in many fields such as new type of electronics,optoelectronics and energy,etc.,due to their excellent mechanical,optical and electronic properties.However,the defect states and lower barrier heights at the heterointerface can lead to higher interlayer recombination,and the surface has also a large light reflectance,which depress the power conversion efficiency（PCE）of TMDs-based heterostructures that always fail to meet people’s expectations and the application requirements of solar cells.Therefore,the effective modulation of their photoelectric properties is a very critical problem in the field of related nanoscience and optoelectronic devices,etc.At present,it has been shown that the interlayer recombination and PCE can be effectively suppressed and enhanced by inserting an insulator such as h-BN into the vdW heterostructure,but the continuous increase of insulator layer after reaching a critical thickness will reduce the PCE.Moreover,the geometric configuration of tilted/horizontal vdW heterostructures has a significant effect on the light absorption,in which the nanosheet arrays can reduce surface light reflectance and enhance light absorption.Although these two heterostructures can enhance photoelectric conversion properties by depressing interlayer recombination and enhancing light absorption,and have the optimal PCE,some fundamental problems need to be resolved urgently,such as the optimized conditions for the optimal PCE,the underlying mechanism on the effect of intercalated insulator for the carrier recombination and collection,the light harvesting mechanism of the nanosheet array as well as the theoretical relationship between size（or geometrical parameters）and photoelectric properties,etc.Therefore,in order to find the optimal conditions and PCE as well as reveal the underlying mechanisms of carrier recombination,carrier collection and light-trapping,in our work,we explore the effects of interface modulation and geometry effect on the photoelectric properties in MoS2/WSe2 vdW heterostructures based on the combination of surface atomic-bond-relaxation method and detailed balance principle.The specific results are shown as follows:（1）We have developed a theoretical model between the thickness and the band offsets as well as the photoelectric properties of Mo S2/h-BN/WSe2 heterostructures,and clarified that the effect of intercalated h-BN on the carrier collection and recombination in the Mo S2/WSe2 heterostructures.It is found that the photoelectric properties of MoS2/h-BN/WSe2 heterostructures have been significantly improved compared to that of MoS2/WSe2.Due to the different levels of suppression of h-BN on interlayer recombination and carrier collection,the PCE of MoS2/h-BN/WSe2 can reach the optimal 3.23%under the condition of single-layer TMDs and 11-layer h-BN.Also,as the thickness of TMDs increases,the optimal PCE can be enhanced to 23.37%,and the optimal thickness of h-BN is reduced to 2.86 nm.（2）We have established a theoretical relationship between light absorptance and geometrical parameters,explored the effect of geometric parameters on the photoelectric properties of MoS2/WSe2 tilted/horizontal heterostructures at the atomic level,and revealed the photon harvesting mechanism.Our results show that the tilted/horizontal heterostructure exhibits excellent photoelectric conversion properties due to its anti-reflection properties.Moreover,we obtain the optimal thickness and tilted angle of MoS2 nanosheet that can achieve the optimal PCE of Mo S2/WSe2 tilted/horizontal heterostructure,and find that the optimal structure of energy harvesting is a type B heterostructure.The optimal PCE can be up to 12.60%in the case of L1=D2=100 nm when the tilt angle and thickness of MoS2 increase to 62°and 9.7 nm,respectively.Also,the optimal PCE can be further enhanced through controlling the sheet tilt angle and size. |
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