Center for Materials Engineering

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Browsing Center for Materials Engineering by Subject "band gap"

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    First-Principles Study Of Van Der Waals Heterostructures of MoSeTe/ZnO for Investigating Photocatalytic Water-Splitting and Photovoltaic Applications
    (Addis Ababa University, 2023-06) Derese, Abraham; Georgies, Alene (PhD)
    Two-dimensional (2D) heterostructures have allowed for the development of novel properties with interesting applications in photocatalytic water splitting and optoelectronic devices. Electronic properties of ZnO and Janus MoSeTe monolayers were investigated using density functional theory (DFT)-based first-principles calculations, and depending on the lattice mismatch, layered 2D MoSeTe/ZnO heterostructures were produced. In this study, the first-principles van der Waals corrected density functional theory calculations were also performed on ABI_Se, ABI_Te, and ABII_Te heterostructure.Out of eight basic stacking patterns of the ZnO/MoSeTe hetero-bilayer designed, the ABII-Te stacking mode was a more stable stacking type due to the small lattice mismatch and the binding energy. The result showed that the band alignment for ABI_Se, ABI_Te, and ABII_Te was done on the electrical band structure and band edge positions, and confirmed type two band alignment. In addition, the ABI_Se, ABI_Te, and ABII_Te configurations of ZnO/MoSeTe vdW heterostructures are indirect band gap semiconductors. The investigated 2D ZnO/MoSeTe heterostructures have an acceptable band gap for solar applications, according to a first-principles study. The power conversion efficiency of ZnO/MoSeTe heterostructure is computed, and the results exhibit ABI_Se, ABI_Te, and ABII_Te stacking orientations have high efficiency with values of 22.26%, 22.31%and22.17%, respectively. Therefore, our findings show the heterostructures have reasonable band gaps and high PCE, and exhibit type-II band alignment, which are suitable candidates for solar cell application. Furthermore, for full water splitting heterostructures cannot satisfy the band edge requirements; however, the heterostructures are a good photocatalyst for the hydrogen evolution reaction. The heterostructure's ability to split water more effectively can be improved by moving the band edges position using strain and doping.
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    Investigation of 2D Hexagonal Transition Metal Dichalcogenide Heterostructures for Photocatalytic Water Splitting and Photovoltaic Solar Cells Using Density Functional Theory
    (Addis Ababa University, 2025-03) Bereket Fekede; Goergis Alene (PhD)
    Advances in materials science and technology are critical to the development of different sophisticated processes. It is imperative to recognize the significance of affordable, sustainable, and eco-friendly energy alternatives. Significant scientific and technological interest has consistently been shown in the use of hydrogen-based technologies towards the provision of clean, green energy in the energy mix. The formation of heterostructures combining MoS2, WS2, and ReS2 is a promising strategy in developing 2D semiconductor-based photo-catalysts for water splitting. This specific Research paper involves theoretical simulations to predict and optimize the properties of MoS2, WS2, and ReS2 heterostructures. This approach helps in understanding the fundamental mechanisms at play and designing more effective photo-catalytic systems. Monolayers and heterostructure combining MoS2, WS2, and ReS2 is constructed and investigated in this study using Density functional study as implemented in quantum ESPRESSO and CASTEP. ReS2 -WS2 hetero structure is type II hetero junction which has greater energy level than that of WS2 monolayer. It is also demonstrated appropriate CBM position located within -2.650 to -4.010eV range according to the band alignment, highlighting another class of suitable materials for hydrogen evolution reaction. In similar manner, hetero structure ReS2-MoS2 has greater energy level than MoS2 monolayer. The band alignment is shows us appropriate CBM position located within -3.054 to -4.350 eV range, this denote this hetero structure is suitable for hydrogen production. The power conversion efficiency of MoS2, WS2 and MoS2 –WS2 heterostructure is computed, and the results exhibit high efficiency with values of 18.7%, 17.0% and 21.4%, respectively making these materials promising for photovoltaic solar cell.