ABSTRACT
Theoretical examination based on first principle computation has been conducted for van der Waals heterostructure (vdwHS) GaAlS2/HfS2including structural, optoelectronic and photocatalytic characteristics. From the adhesion energy calculation, the AB configuration of GaAlS2/HfS2vdwHS is the most stable. A type-II GaAlS2/HfS2vdwHS is a dynamically and thermally stable structure. The band edge position, projected band, and projected charge densities verify the type-II alignment of GaAlS2/HfS2vdwHS. For GaAlS2/HfS2, GaAlS2is acting as a donor and HfS2is acting as an acceptor ensured by the charge density difference plot. The electron localized function validates the weak van der Waals interaction between GaAlS2and HfS2. The GaAlS2/HfS2vdwHS possess an indirect bandgap of 1.54 eV with notable absorption in the visible range. The findings assure that the GaAlS2/HfS2vdwHS is an efficient photocatalyst for pH 4-8. The band alignment of GaAlS2/HfS2is suitable for Z-scheme charge transfer. The strain influenced band edge suggests that the GaAlS2/HfS2vdwHS remains photocatalytic for strain-4%to+6%in both cases of uniaxial and biaxial strains.
ABSTRACT
The computational study of the van der Waals hetero (vdW) bilayer GeI2/InTe has been carried out in present study. The isolated monolayer GeI2and InTe have been studied first and the results were compared to the previous studies. The possible stackings are considered after the vdW interaction correction is applied in the structure relaxation. The vdW hetero bilayer stability has been checked from the phonon dispersion andab initioMolecular Dynamics calculations. The charge transfer from InTe to GeI2monolayer. Type-II indirect band gap (1.98, 2.01 eV) is verified by the projected band structure and band alignment calculations. The vdW hetero bilayer is a superior photocatalyst for the pH value up to pH = 0 to 11. The optical properties are calculated from the complex dielectric constant. The absorption coefficient shows the enhance absorption of light in the visible and ultraviolet regions. The vdW hetero bilayer has shown low reflectivity (37%) and a high refractive index (2.80) in the visible region. The enhanced optical properties have shown its possible applications in optoelectronic devices.
ABSTRACT
First principle calculations of novel two-dimensional (2D) group-III ternary chalcogenide monolayer (G3TCM) compounds have been carried out using density functional theory. The 2D hexagonal structure has a honeycomb-like appearance from both the top and bottom views. Both pristine and G3TCM compounds are energetically favourable and have been found to be dynamically stable via phonon calculations. Theab-initiomolecular dynamics calculations show the thermodynamical stability of the G3TCM compounds. The G3TCM compounds exhibit semiconductor behaviour with a decreased indirect bandgap compared to the pristine monolayers. Chalcogen atoms contribute mainly to the valence bands, while group-III atoms have a major contribution to the conduction band. A red shift has been observed in the absorption of light, mainly in the visible and ultraviolet regions, and the refractive index is increased compared to the pristine material. Both pristine and G3TCM compounds have been found to be more active in the ultraviolet region, and low reflection has been observed. In the 6-8 eV range of the ultraviolet region, zero reflection and the highest absorption are observed. The monolayer has shown potential applications in optoelectronics devices as an ultraviolet and visible light detector, absorber, coating material, and more. The band alignment of the 2D G3TCM monolayer is calculated to observe its photo-catalyst behaviour.
ABSTRACT
In this investigation, the structural, electronic, and optical properties of two-dimensional van der Waals heterostructure (vdwHS) PtSe2/GaSe with three different configurations have been studied using density functional theory with the generalized gradient approximation. All three optimized vdwHSs PtSe2/GaSe have positive phonon frequencies and hexagonal unit cells. The hybrid exchange-correlation functional has been employed to study the electronic properties of vdwHSs PtSe2/GaSe. The vdwHSs PtSe2/GaSe shows semiconducting behavior with indirect Type-II bandgaps, which have been confirmed by the charge density difference, electrostatic potential, work function, and band edge calculations. Additionally, from the band edge positions, the vdwHSs PtSe2/GaSe are analyzed for photocatalytic activities. The optical properties such as extinction coefficient, refractive index, reflectivity, energy loss spectrum, and absorption coefficient have been studied using norm-conserving pseudo-potentials. The vdwHSs PtSe2/GaSe exhibit consistent absorption from the visible to the ultraviolet region of the electromagnetic spectrum. From the obtained results, we conclude that vdwHSs PtSe2/GaSe could be utilized for H2 production through photocatalytic activity as well as for optoelectronic devices and their application.
ABSTRACT
In the present work, Janus monolayers WSSe and WSTe are investigated by combining first-principles calculations and semiclassical Boltzmann transport theory. Janus WSSe and WSTe monolayers show a direct band gap of 1.72 and 1.84 eV at K-points, respectively. These layered materials have an extraordinary Seebeck coefficient and electrical conductivity. This combination of high Seebeck coefficient and high electrical conductivity leads to a significantly large power factor. In addition, the lattice thermal conductivity in the Janus monolayer is found to be relatively very low as compared to the WS2 monolayer. This leads to a high figure of merit (ZT) value of 2.56 at higher temperatures for the Janus WSTe monolayer. We propose that the Janus WSTe monolayer could be used as a potential thermoelectric material due to its high thermoelectric performance. The result suggests that the Janus monolayer is a better candidate for excellent thermoelectric conversion.
