نشریه پژوهش سیستم های بس ذره ای
سال سیزدهم شماره 4 (پیاپی 39، زمستان 1402)

In this study, a CIGS solar cell with a Mo/Cu(In0.7Ga0.3)Se2(CIGS)/CdS/ZnO/Al-doped ZnO (AZO) structure was simulated by Atlas silvaco-TCAD software. The photovoltaic characteristics of solar cells using CdS and ZnSe buffer layers were calculated and compared. Then, the photovoltaic characteristics were examined with different thicknesses of the ZnSe buffer layer. The 25 nm thickness was selected as the optimum thickness. After optimization of the ZnSe layer thickness, the photovoltaic characteristics of solar cells were evaluated by changing the conduction band offset (CBO). The highest CIGS solar cell conversion efficiency was obtained in the range from -0.5 eV to +0.5 eV for CBO. Finally, graphene was replaced with Al-doped ZnO (AZO) due to its high optical transparency, high carrier mobility, and proper mechanical properties. Graphene was used as a monolayer and multilayer as a transparent conductive oxide (TCO) layer. Simulations predicted the highest efficiency for solar cell structure based on Mo/CIGS/ZnSe/i-ZnO/monolayer graphene and the photovoltaic parameters were Jsc=38.64 mA/cm2, Voc=0.67 V, FF=79.33% and η=20.71%.

Liquid crystals with high optical and electro-optical responses play an important role in optics and photonics. Therefore, providing a simple method to increase the optical behavior of liquid crystals under the influence of external fields can be considered one of the most challenging research areas. In this experimental work, the effects of temperature and right-handed chiral material with different weight percentages on the refractive indices and optical properties of E7 nematic liquid crystal under the influence of an external electric field were investigated. Despite the reduction of the Kerr constant with increasing the weight percentage of chiral dopants and temperature, the highest amount of optical response in the presence of the electric field was obtained for the nematic liquid crystal doped with 3% of right-handed material. In this case, the value of the Kerr constant is almost 2 times that of pure liquid crystal. This interesting result can be related to the order parameter changes caused by different molecular interactions. Thus, the results obtained in this research can be used as a simple method to increase the optical response of nematic liquid crystals in the presence of an external electric field.

The study of the astrophysical S-factor is one of the methods of analyzing proton radiation capture reactions in the theoretical framework for low temperatures. In this research, we have numerically studied the proton radiative capture reaction by 17O using the Woods-Saxon potential model. First, the astrophysical S-factor reaction was calculated at low energies, and then the reaction rate of was obtained from the astrophysical S-factor. Also, in this study, the electrical quadrupole transition strength (B[E2]) for excited states 18F nucleus has been calculated. We found that B[E2] depends on the energy and spin of the excited states. The results corresponding to the astrophysical S-factor, reaction rate and transition strength at energy range of 200-500 keV were compared with experimental data and other theoretical models and were in good agreement. Also, the astrophysical S-factor at zero energy was calculated by the extrapolation method for (5/2)+ state and S(0)=4/8 keV b.

In this paper, we study the electrical conductance of a molecular bridge consisting of a graphyne ring with the chemical formula C18H6 connected to two cumulene electrodes using the tight-binding model. We then compare its conductance to a similar system in which the graphyne ring has been replaced by a benzene molecule. To do this, we first obtain the structural characteristics of the studied rings using density functional theory, and then use the method of matching levels, to obtain the tight-binding parameters, i.e., the on-site and hopping energies for the benzene and graphyne rings. Using these parameters, we study the electrical conductance for these two molecules, the benzene and the graphyne rings. We conclude that when these two molecules are in the same position between two cumulene electrodes, they exhibit the same electrical properties. However, in the graphyne ring, a phase transition from metal to semiconductor or vice versa can be created with less energy than in a benzene ring.

In this research, the singularity of the central shape-invariant potentials, which have a singularity of the inverse-square power , has been investigated. It has been shown that in quantum mechanics, for , the eigenvalue problem is well-defined and, as a result, the energy spectrum can be determined. In the transition region, for , both regular and irregular wave functions are square integrable and therefore acceptable, but the boundary conditions for determining the eigenvalues and eigenfunctions are not sufficient and there is no a specific predetermined mechanism for choosing a linear combination of wave functions. For , the particle is drawn to the singularity, and therefore, there is no any ground state with finite energy. It has also been shown using supersymmetric quantum mechanics that the inverse-square potential is the result of the singular inverse superpotential . Supersymmetric quantum mechanics provides a mechanism that, without any additional constraints, the less singular wave function is chosen and the potential is placed in the transition region for .

In this study, the structural properties and electronic band structure of InSb1-xBix (x=0, 0.25, 0.5, 0.75, 1) alloys are investigated using density functional theory utilizing the WIEN2K package. The results related to the structural properties showed that the lattice constant, as a function of x, is in excellent agreement with Vegard's linear rule. Calculations involving the investigation of the band structure using the mBJGGA exchange-correlation potential reveal that InSb is a semiconductor with a small gap , exhibiting a normal band order at the Γ point while InBi is a metal that exhibits a band inversion at the Γ point. By adding Bi to InSb and forming InSb0.75Bi0.25 and InSb0.25Bi0.75 alloys, the normal band order and the gap at the Γ point disappear. This leads to a transition from a narrow band gap semiconductor with normal band order (InSb) to a gapless semiconductor (InSb0.75Bi0.25) and a metal (InSb0.25Bi0.75) with an inverted band order. By replacing half of the Sb atoms with Bi atoms in InSb and creating the InSb0.5Bi0.5 alloy, not only is an inverted band order observed at the Γ point but a band gap is also created and a transition from a conventional semiconductor to a topological semiconductor occurs.