Using first-principles calculations based on density functional theory (DFT), the structural, optoelectronic, and transport properties of the MgICl Janus monolayer have been investigated. The ...stability is validated by the ab-initio molecular dynamics (AIMD), cohesive energy, and phonon spectrum. We found that Janus MgICl monolayer is a direct band-gap semiconductor with an energy gap of 3.35 eV (PBE) and 4.87 eV (HSE), and is energetic and dynamically stable. The dielectric matrix has been calculated within the random phase approximation (RPA). The optical-absorption coefficient is found to be very less in the visible region, and the calculated refractive index values are very near to that of water. The reflectivity is found to be less than 10% in the visible region which further increases in the UV region. The electrical conductivity of the Janus MgICl using Boltzmann transport theory, and the effective mass of electrons and holes have been calculated; the results present good electrical conductivity and small values of effective mass owing to high mobility. These theoretical investigations suggest that the Janus MgICl is a thermodynamically stable and promising material for use in the solar cells as a transparent conductor material.
Graphical Abstract
In this paper, we study the magnetic and thermodynamic properties of the Bethe-Lattice system using Monte Carlo simulations for the Heisenberg model. The magnetizations and specific heat of the ...system are derived from several reduced biquadratic exchange interactions. Transition temperatures are obtained and discussed. The magnetizations as a function of the reduced biquadratic exchange interactions, for different values of reduced temperature, are illustrated. It is found that when increasing the reduced biquadratic interaction increases, the loop area of the hysteresis cycle as well as the reduced coercive magnetic field in the z direction increase. Whereas for the x and y directions, the reduced biquadratic interaction increases the area of the hysteresis cycle loop. While for both x and y directions, the saturation of the magnetizations decreases. Finally, the magnetic hysteresis cycle for different values of physical parameters is plotted and interpreted.
Zinc oxide (ZnO) thin films grown on glass substrates are prepared by means of the Ion Layer Gas Reaction process. The XRD pattern revealed that the ZnO lattice parameters decrease continuously, with ...the increasing of the film thickness, indicating a continuous variation in the compressive strain. The influence of the thickness on the optical, morphological and structural properties of deposited ZnO thin films was investigated. The UV–Vis absorption spectra of deposited thin films were shown to exhibit a blue-shift, resulting in an increase in the optical band gap from 3.13 eV to 3.24 eV. Structural parameters such as crystallite size, lattice parameters, Zn–O bond length, and residual stress have been determined, and the compressive strain (tensile stress) is found to increase with the increasing of spray time and in turn deposited thin film thickness. The PL spectra of deposited ZnO films, show stronger PL intensity with increasing deposited thin film thickness, which confirm the influence of deposited film thickness on the recombination process of charge carriers and thus on its optical properties. These results, were confirmed by the photo-electrochemical experiments. In addition, a wettability alteration and shift from hydrophobic to hydrophilic surface is observed under UV light exposure, which shows that structural defects and surface morphology of deposited thin films were also demonstrated to have a direct impact on deposited films’ optical properties. Furthermore, to further confirm these experimental optical results, theoretical first principle calculations were conducted. In addition, a wettability alteration and shift from hydrophobic to hydrophilic surface is observed under UV light exposure.
Phosphorene, a new two-dimensional material, was investigated theoretically as a promising photocatalyst material. The structural and electronic properties of phosphorene were studied using hybrid ...functional based HSE approximation. The effect of the adsorbed molecules on the phosphorene surface was studied for various chemical elements, such as water molecule (H
2
O), hydronium ion (H
3
O
+
), hydrogen atom and ion (H/H
+
), hydroxide molecule (OH), and hydroxide ion (OH
−
). The potential application of phosphorene as a photocatalyst in vacuum was proved under different pH values. A pH of 8 was found to be the suitable value for clean phosphorene in which the flat band position was corrected for the oxidizing and reducing potentials of phosphorene, but the presence of OH
−
ions in a basic solution damaged the surface structure and limited the use of phosphorene in photocatalysis caused by the high content (0.25 ML and 0.5 ML) of the adsorbed OH
−
on the phosphorene surface. The obtained results matched the required parameters of a photocatalyst for water splitting using clean phosphorene surface in neutral solution (pH = 7).
Phosphorene, a new two-dimensional material, was investigated theoretically as a promising photocatalyst material.
Higher power conversion efficiencies for photovoltaic devices can be achieved through simple and low production cost processing of APbI3(A=CH3NH3,CHN2H4,…) perovskites. Due to their limited long-term ...stability, however, there is an urgent need to find alternative structural combinations for this family of materials. In this study, we propose to investigate the prospects of cation-substitution within the A-site of the APbI3 perovskite by selecting nine substituting organic and inorganic cations to enhance the stability of the material. The tolerance and the octahedral factors are calculated and reported as two of the most critical geometrical features, in order to assess which perovskite compounds can be experimentally designed. Our results showed an improvement in the thermal stability of the organic cation substitutions in contrast to the inorganic cations, with an increase in the power conversion efficiency of the Hydroxyl-ammonium (NH3OH) substitute to η = 25.84%.
Motivated by recent works dealing with electronic properties and high carrier mobility of monolayer materials and their potential applications in nano thick solar cells, we investigate the electronic ...properties and performance of new nano thick solar material based on GeSe/SnS hetro-bilayer. The calculations are performed using DFT calculations within GGA + vdW and HSE06 hybrid functional approximations. Our results indicate that this hetro-bilayer has a direct band gap of 1.48
eV
, which is in the optimal range of the efficient single-junction solar cell, and forms the type-II band alignment in which
SnS
is the donor and
GeSe
is the acceptor. The values of
V
oc
,
FF
and
J
sc
using an external quantum efficiency with a limit of 100% are also calculated. Using Scharber model, the upper limit of power conversion efficiency, PCE, is estimated to be 18.74% which is higher than the reported efficiencies of hetro-bilayers. Another estimate of PCE via the descriptor model is found to be 28.83%. These findings make this hetero-bilayer a good candidate for solar energy conversion as an efficient nano-thick solar cell material, and optoelectronics applications as well.
Magnesium is an attractive hydrogen storage candidate due to its high gravimetric and volumetric storage capacities (7.6 wt.% and 110 gH2/l, respectively). Unfortunately, its use as a storage ...material for hydrogen is hampered by the high stability of its hydride, its high dissociation temperature of 573–673 K and its slow reaction kinetics. In order to overcome those drawbacks, an important advancement toward controlling the enthalpy and desorption temperatures of nano-structured MgH2 thin films via stress/strain and size effects is presented in this paper, as the effect of the nano-structuring of the bulk added to a biaxial strain on the hydrogen storage properties has not been previously investigated. Our results show that the formation heat and decomposition temperature correlate with the thin film’s thickness and strain/stress effects. The instability created by decreasing the thickness of MgH2 thin films combined with the stress/strain effects induce a significant enhancement in the hydrogen storage properties of MgH2.
Phosphorene is a new two-dimensional material that has recently attracted much attention owing to its fascinating electrical, optical, thermal and chemical properties. Here, we report on high-quality ...exfoliation of black phosphorus nanosheets, with controllable size produced in large quantities by liquid-phase exfoliation using
-methyl-2-pyrrolidone (NMP) as a solvent under ambient conditions. The as-synthesized few layers show a great potential for solar energy conversion based on the optical results shown in this work.
In this paper we numerically study the probability Pac of the occurrence of car accidents in the extended Nagel–Schreckenberg (NS) model in the case of mixture of fast (Vmax1=5) and slow vehicles ...(Vmax2=1) by taking also to the risky overtaking of fast vehicles. In comparison with previous existing models, we find that accidents can occur in the free traffic phase and/or congested one depending on the overtaking rate of fast vehicles. The effect of evacuation of damaged vehicles from the road with probabilities Pevf and Pevs of fast and slow vehicles respectively on the traffic flow behavior is also computed.
•Realistic car accident model.•Risky overtaking of fast vehicles.•Occurrence of accident even in free flow traffic.
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