Two-dimensional Van der Waals heterostructures based chalcogenide for photovoltaic applications: a DFT study

In this paper, structural, electronic properties, optical spectra, stability, as well as the quantum efficiency of bulk, monolayer and two different stacking heterostructure configurations (XY2/XY2) of dichalcogenide compounds XY2 (where X = Mo or W and Y = S or Se) were performed using density functional technique. Our findings reveal the strong chemical bonds and high interlayer banding energy for MoSe2/WSe2 heterostructure of configuration-2, which confirms its stability and its feasibility for synthesizing. Besides, the elastic stiffness coefficients demonstrate all studied heterostructures are mechanically stable at ambient pressure, this means that the studied heterostructures are harder to separate their components, making them more durable and less reactive under certain conditions, especially MoSe2/WSe2 heterostructure-configuration 2. Otherwise, the electronic band structure highlights an indirect semiconductor behavior for bulk XY2. In contrast, a strong ionic bonding between the chalcogen and metal atoms leads to the electrons confinement in the direction perpendicular to the plane revealing direct semiconductor behavior for monolayers XY2 at Gamma point. Besides, after combining two monolayers with different work functions the holes and electrons are accumulated in different layers, therefore indirect excitons have been observed for XY2/XY2 heterostructures (Gamma -> K). Furthermore, due to the presence of the type-II band alignment, the optical absorbance spectra proves that the absorbance is enhanced along both x and z directions for all investigated heterostructures. In addition, the MoSe2/WSe2 heterostructure of configuration-2, has about 65% of photons converted into usable electrical power, while 35% of photons are lost as heat and/or reflected. Finely, its high stability, its suitable forbidden band, its high visible light absorption, as well as its high quantum efficiency make the 2D Van der Waals MoSe2/WSe2 heterostructure-configuration-2 as new potential candidate for upcoming nano-electronic, photovoltaic and optoelectronic devices.