Center for Materials Engineering

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Browsing Center for Materials Engineering by Author "Birhan, Tesfaye"

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    First Principles Investigation of Van Der Waals Heterostructures of Mos2 and Janus Transition Metal Dichalcogenides for Energy Applications
    (Addis Ababa University, 2021-09) Birhan, Tesfaye; Georgies, Alene (PhD)
    Recent research on the Janus transition metal dichalcogenide (JTMD) with an asymmetric structure has revealed that this material possesses interesting unique properties, notably in solar cells. This work is based on cutting-edge density functional theory (DFT) computations utilizing Generalized Gradient Approximation- Perdew–Burke–Ernzerhof functional (GGA-PBE) as implemented in the Quantum ESPRESSO and VASP codes. To find the most stable optimized heterostructures, eight basic stacking patterns were designed. Then, for MoSSe/MoS2, WSSe/MoS2, and MoSTe/MoS2 heterobilayer, the AAII-S stacking mode was more stable than the other stacking types. According to the findings, the band alignment was type-I for MoSSe/MoS2, MoSTe/MoS2, and type-II for WSSe/MoS2, within, 1.03, 0.30 and 0.84 eV are estimated bandgap, respectively. The electrical band structure, as well as band edge placements, was investigated. When the water redox and oxidation potentials of heterostructures were compared, it was discovered that MoSSe/MoS2, MoSTe/MoS2, and WSSe/MoS2 were not applicable for photocatalytic materials for full water splitting. On the other hand, MoSSe/MoS2 and MoSTe/MoS2 heterostructures were placed lower than the oxidation potential of O2/H2O, making them applicable for oxygen evolution reaction (OER). This work reveals that JTMDs/MoS2 heterostructures are often subsequent material that promotes the development of photovoltaic devices, specially MoSSe/MoS2, and WSSe/MoS2 vdWH. The power conversion efficiency (PCE) of the heterostructures is calculated, and the results show that MoSSe/MoS2 and WSSe/MoS2 show very good efficiency with values of 19.41% and 16.25%, respectively. The result is good when compared to other similar studies: GaTe-InSe (9.1%), MoS2/p-Si (5.23%), organic solar cells (11.7%), and PN-WSe2 (13.8 % ). Since the results are encouraging, we believe it is a good idea to do additional experiments on the heterostructures and adapt them to solar cell applications.