A DFT study of 2D Van der Waals Heterostructures of Janus Transition Metal Dichalcogenides with WSe2 Monolayer for Energy Applications
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Date
2021-09
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Addis Ababa University
Abstract
Atomically thin two-dimensional layered semiconductor materials such as Transition Metal Dichalcogenides (TMDs) have a great potential for solar cells applications due to their favorable photon absorption and electronic transport properties. The combination of 2D materials in the form of van der Waals heterostructures has been proved to be an effective approach for improving the electronic properties of the material. In this work, the electronic properties, such as band structure, bandgap, and band alignment of MoSSe/WSe2, WSSe/WSe2, and WSeTe/WSe2 vdW heterostructures were obtained from Density Functional Theory (DFT). The potential of the exchange and correlation was calculated using the Generalized Gradient-Perdew Berk Ernzed (GGA-PBE) approximation. MoSSe/WSe2, WSeTe/WSe2, and WSSe/WSe2 heterostructures have type-II band alignments, which is advantageous for electron-hole pair separation. Photons can be absorbed directly in MoSSe/WSe2 and WSeTe/WSe2 semiconductors because they have direct bandgaps. WSSe/WSe2 semiconductor has an indirect bandgap, which means that a phonon must also be absorbed or emitted for a photon to be absorbed. The most stable stacking order in heterostructures comprising Janus monolayers of TMDs and WSe2 has been ascertained based on interlayer binding energies. The binding energies in MoSSe/WSe2, WSSe/WSe2, and WSeTe/WSe2 heterostructures were found to be -18216.75 eV, -38995.69 eV, and -0.3296 eV at an equilibrium interlayer space of 5.75 Å, 4.02 Å, and 4.72 Å respectively, which are more stable than the other tested configurations. The solar cell and photocatalytic applications of the heterostructures were investigated. The structures were not promising for photocatalytic applications because the band levels of semiconductors were insufficient to support full water splitting. When MoSSe/WSe2, WSSe/WSe2, and WSeTe/WSe2 were used as PV materials, the Power Conversion Efficiency (PCE) was found to be 20.16%, 20.48%, and 19.05%, respectively. The results show that it can serve as a suitable photovoltaic material with high efficiency and opening possibilities to develop solar cells based on 2D TMDs materials.
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JTMDs/WSe2 Heterostructure, DFT, Bandgap, Band Alignment, Binding Energy