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Abstract In this paper, we first investigate the electronic properties of the two-dimensional structure of dichalcogenide Pd2S4. These properties strongly depend on the crystal field splitting which can change by atomic vacancies (S and Pd vacancies). The main purpose of the present paper is to create remarkable magnetic properties in the system by adding 3d transition metal atoms where the presence of Mn, Cr, and Fe creates the exchange interaction in the system as well as change in the crystal field. The created magnetic properties strongly depend on the competition between exchange interaction and crystal field to separate the levels of d orbitals. In addition, the presence of the transition metals in the structures with S and Pd vacancy has been investigated carefully. The calculations demonstrate that we can achieve an extensive range of magnetic moment up to 3.131 $${\mu }_{B}$$ μ B . The maximum one is obtained in the presence of Mn and absence of sulfur while some of the doped structures does not have magnetic moment. Our results show that Pd vacancy in the presence of Cr, Mn and Fe metals increases the magnetic property of the Pd2S4 structure. The extensiveness and variety of the obtained properties can be used for different magnetic and non-magnetic applications.

Perovskite solar cell (PSC) consisting textile-based electrodes has been created novel features for future energy supply. Recently, Cs0.05(FA0.85MA0.15)0.95Pb(I0.85Br0.15)3 perovskite has appeared as a favourable candidate for flexible perovskite solar cells. However, a confined performance was acquired when the conventional Spiro-OMeTAD were used as hole transport layer (HTL) material because of suboptimal valance band offset (ΔEV) between Perovskite/HTL layers. In this study, a theoretical drift–diffusion​ modelling is used by finite volume method (FVM) to investigate performance of textile perovskite solar cell with double hole transport layers (HTLs) with graded band gap energies. Copper thiocyanate (CuSCN) and Nickel Oxide (NiO) are replaced as double HTLs, which dramatically enhanced the performance due to optimal upward step by step valance band offsets (ΔEV) between Perovskite/Textile Composite Electrode layers. It is shown that the decreasing of the metal–semiconductor schottky barrier height of electrodes leads to significant increase in fill factor (FF). Also, it is revealed that the enriching of perovskite carrier diffusion length by equipoising of carrier capture cross section, carrier total defect density and carrier thermal velocity substantially promote the overall device efficiency. The short-circuit current (Jsc) of 20.65 mA/cm 2, open-circuit voltage (Voc) of 1.19 V, fill factor (FF) of 73.57%, and power conversion efficiency (PCE) of 18.20% have been obtained by optimization of electrodes properties and perovskite layers. Remarkably, the advantageous of low cost, flexible, and chemical stable conducive textile composite, extends new opportunities in the commercial expansion of highly efficient photovoltaic textile in optoelectronic industry field.

Abstract By using density functional theory calculations, we have studied the effects of V-, Cr-, Mn-, Fe- and Co-doped on the electronic and magnetic properties of the 1T-NiS2 monolayer. The results show that pure 1T-NiS2 monolayer is a non-magnetic semiconductor. Whereas depending on the species of transition metal atom, the substituted 1T-NiS2 monolayer can become a magnetic semiconductor (Mn-doped), half-metal (V- and Fe-doped) and magnetic (Cr-doped) or non-magnetic (Co-doped) metal. The results indicate that the magnetism can be controlled by the doping of 3d transition metal atoms on the monolayer. In this paper, the engineering of the electric and magnetic properties of 1T-NiS2 monolayer is revealed. It is clear that it could have a promising application in new nanoelectronic and spintronic devices.

Since perovskite solar cells have attracted a great deal of attention over the past few years, the enhancement of their optical absorption and current density are among the basic upcoming challenges. For this reason, first, we have studied the structural and optical properties of organic–inorganic hybrid halide perovskite CH3NH3PbI3 and the compounds doped by chlorine halogen CH3NH3PbI3−xClx in the cubic phase by using a density functional theory (DFT). Then, we model a single-junction perovskite solar cell based on a full solution to Maxwell’s equations, using a finite difference time domain (FDTD) technique, which helps us to investigate the light absorption efficiency and optical current density of the cell with CH3NH3PbI3−xClx (x  =  0, 1, 2, 3) as the active layer. The results suggest that increasing the amount of chlorine in CH3NH3PbI3−xClx compound leads to an increase in the bandgap energy, as well as a decrease in the lattice constants and optical properties, like the refractive index and extinction coefficient of the structure. Also, the results obtained by the simulation express that by taking advantage of the light trapping techniques of SiO2, a remarkable increase of light absorption will be achieved to the magnitude of 83.13%, which is noticeable. [ABSTRACT FROM AUTHOR]

In this paper, we consider zigzag-edge germanene nanoribbons with small buckling and even (symmetric) or odd (asymmetric) widths. Although the band structures of these two type structures are the same, they are noticeably different in terms of conductivity and current. In previous works on silicene, the role of buckling to dominate the effect of symmetry has been ignored and just the buckling changes of the symmetry space group from σ to C2 are shown. In this case, buckling is the main factor responsible for differences in conductivity and current. Fluorine, hydroxyl, and hydrogen are used to passivate the nanoribbon edges. Results show that the current and conductivity are strongly dependent on the kinds of substitutional atoms/groups used to passivate the structure. It is found that symmetry breaking is not the only effective factor in the creation of current—buckling and backscattering are also important. [ABSTRACT FROM AUTHOR]

Thermal and electron transport through organic molecules attached to three-dimensional gold electrodes in two different configurations, namely para and meta with thiol-terminated junctions is studied theoretically in the linear response regime using Green’s function formalism. We used thiol-terminated (–SH bond) benzene units and found a positive thermopower because the highest occupied molecular orbital (HOMO) is near the Fermi energy level. We investigated the influence of molecular length and molecular junction geometry on the thermoelectric properties. Our results show that the thermoelectric properties are highly sensitive to the coupling geometry and the molecular length. In addition, we observed that the interference effects and increasing molecular length can increase the thermoelectric efficiency of device in a specific configuration. [ABSTRACT FROM AUTHOR]

In this paper, we investigated the behaviors of the absorptive-dispersive properties of weak probe light based on quantum coherence and interference in a Landau-quantized graphene nanostructure driven by coherent pumping fields. The linear dynamical properties of the grapheme are discussed with reference to the density matrix method and the perturbation theory. It is found that under certain conditions and by an appropriate selection of the parameters of the medium, the absorption, dispersion and group index of the weak probe light can be controlled. Moreover, the superluminal light propagation in the system is accompanied by amplification to make sure that the probe field is amplified as it passes through the system via adjusting the corresponding controllable parameters such as the intensity, the detuning and the relative phase of the applied fields. Moreover, it is observed that the probe amplification can be obtained in the presence or absence of population inversion by properly choosing the system’s parameters. We hope that these results may have useful application in future quantum communicational systems and networks. [ABSTRACT FROM AUTHOR]

We study the controlling of the Goos-Hänchen (GH) shifts in reflected and transmitted light beams in the triple coupled InGaAs/GaAs quantum dot (QD) nanostructures with electron tunneling and incoherent pumping field. It is shown that the lateral shift can become either large negative or large positive, which can be controlled by the electron tunneling and the rate of incoherent pump field in different incident angles. It is also demonstrated that the properties of the GH shifts are strongly dependent on the probe absorption beam of the intracavity medium due to the switching from superluminal light propagation to subluminal behavior or vice versa. Our suggested system can be considered as a new theoretical method for developing a new nano-optoelectronic sensor. [ABSTRACT FROM AUTHOR]

The charge and spin-dependent thermoelectric properties of different lengths of polythiophene in a molecular junction are investigated using the Büttiker probe method within Green function formalism in linear response regime. The coupling of the molecular chain to three-dimensional ferromagnetic electrodes is described by a tight-binding model for both parallel and antiparallel spin configurations. The decrease of height of transmission probability peaks and thermoelectric coefficients are observed in the presence of the Büttiker probes. The reduction is more intensive in the strong dephased chains. Results show that the spin magnetothermopower is bigger than the charge magnetothermopower due to the larger difference between the spin thermopowers with respect to the charge ones. In addition, we observed that the kind of carriers participating in the thermoelectric transport depends on the number of the thiophene rings. [ABSTRACT FROM AUTHOR]

In this paper we investigate the optical properties of an open four-level tripod atomic system driven by an elliptically polarized probe field and compare its properties with the corresponding closed system. Our results reveal that absorption, dispersion, group velocity, and optical bistability of the probe field can be manipulated by adjusting the phase difference between the two circularly polarized components of a single coherent field and cavity parameters, i.e., the atomic exit rate from cavity and atomic injection rates. [ABSTRACT FROM AUTHOR]

The effect of Er3+ ion concentration and incoherent pumping field on the refractive index and group index in an Er3+: YAG crystal is investigated. It is shown that under different concentrations of Er3+ ion in the crystal, the index of refraction and absorption can be changed and a high index of refraction is accompanied by amplification in the medium. Also, it is shown that with the switching from subluminal to superluminal, or vice versa, light propagation can be obtained by different concentrations of Er3+ ions in the crystal. [ABSTRACT FROM AUTHOR]

We study the absorption-dispersion process and group index of weak probe field in a four-level Er3+:YAG crystal. We find that the Er3+ ion concentration and incoherent pumping field can influence the absorption-dispersion process and group index of weak probe field. Moreover, our results show that Er3+ ion concentration plays a major role in lasing without inversion and absorption with inversion. [ABSTRACT FROM AUTHOR]

We theoretically analyze the transient properties of a probe field absorption dispersion in a quantum-dot nanostructure driven by terahertz signal radiation. Here a four-level quantum-dot nanostructure is designed numerically by Schrödinger and Poisson's equations. We show that in the presence of the THz signal, the medium becomes phase dependent and the absorption dispersion can be dramatically influenced by the relative phase between applied fields. [ABSTRACT FROM AUTHOR]

A double cascade-type four-level multiple-quantum-well-based exciton—biexciton transitions are proposed. The study is carried out on a 4.8-nm ZnSe single-quantum well which is embedded into ZnMgSSe cladding layers and pseudomorphically grown by molecular beam epitaxy on a (0 0 1) GaAs substrate. It is displayed that the exciton spin relaxation and relative phases between applied fields can influence the transient and steady-state behaviors of absorption, dispersion, and group velocity of two weak probe and signal fields. Also, transient behaviors of electron population of different levels are discussed. It is found that the probe or signal amplification occurs in the absence of population inversion. [ABSTRACT FROM AUTHOR]

In this paper, we first investigate the electronic properties of the two-dimensional structure of dichalcogenide Pd 2 S 4 . These properties strongly depend on the crystal field splitting which can change by atomic vacancies (S and Pd vacancies). The main purpose of the present paper is to create remarkable magnetic properties in the system by adding 3d transition metal atoms where the presence of Mn, Cr, and Fe creates the exchange interaction in the system as well as change in the crystal field. The created magnetic properties strongly depend on the competition between exchange interaction and crystal field to separate the levels of d orbitals. In addition, the presence of the transition metals in the structures with S and Pd vacancy has been investigated carefully. The calculations demonstrate that we can achieve an extensive range of magnetic moment up to 3.131 [Formula: see text]. The maximum one is obtained in the presence of Mn and absence of sulfur while some of the doped structures does not have magnetic moment. Our results show that Pd vacancy in the presence of Cr, Mn and Fe metals increases the magnetic property of the Pd 2 S 4 structure. The extensiveness and variety of the obtained properties can be used for different magnetic and non-magnetic applications., (© 2022. The Author(s).)

Charge transfer characteristics of single-molecule junctions at the nanoscale, and consequently, their thermoelectric properties can be dramatically tuned by chemical or conformational modification of side groups or anchoring groups. In this study, we used density functional theory (DFT) combined with the non-equilibrium Green's function (NEGF) formalism in the linear response regime to examine the thermoelectric properties of a side-group-mediated anthracene molecule coupled to gold (Au) electrodes via anchoring groups. In order to provide a comparative inspection three different side groups, i.e. amine, nitro and methyl, in two different positions were considered for the functionalization of the molecule terminated with thiol or isocyanide anchoring groups. We showed that when the anchored molecule is perturbed with side group, the peaks of the transmission spectrum were shifted relative to the Fermi energy in comparison to the unperturbed molecule (i.e. without side group) leading to modified thermoelectric properties of the system. Particularly, in the thiol-terminated molecule the amine side group showed the greatest figure of merit in both positions which was suppressed by the change of side group position. However, in the isocyanide-terminated molecule the methyl side group attained the greatest thermoelectric efficiency where its magnitude was relatively robust to the change of side group position. In this way, different combinations of side groups and anchoring groups can improve or suppress thermopower and the figure of merit of the molecular junction depending on the interplay between charge donating/accepting nature of the functionals or their position.

Density functional theory (DFT) and the non-equilibrium Green's function (NEGF) formalism in the linear response regime were employed to investigate the impact of doping on the electronic and phononic transport properties in an anthracene molecule attached to two metallic zigzag graphene nanoribbons (ZGNRs). Boron (B) and nitrogen (N) atoms were used for doping and co-doping (NB) of carbon atoms located at the edge of the anthracene molecule. Our results show that B doping enhances the electronic transport in comparison with the other dopants which is due to its ability to increase the binding energy of the system. The chemical doping of the anthracene molecule mainly impacts on the thermopower which results in a significantly enhanced electronic contribution of the figure of merit. On the contrary, considering the effect of phononic thermal conductance suppresses the figure of merit. However, by taking into account the effect of both electron and phonon contributions to the thermal conductance, we find that the thermoelectric efficiency can be improved by B doping. The potential role of the phononic thermal conductance in shaping the thermoelectric properties of molecular junctions has been ignored in numerous studies, however, our findings demonstrate its importance for a realistic and accurate estimation of the thermoelectric figure of merit.