M. BOUARISSA Nadir

In this paper, a novel solar cell based on hydrogenated amorphous silicon (a-Si:H) and metal oxides CuO is proposed. Using the one-dimensional computer code SCAPS-1D and under the AM1.5G spectrum, the a-Si:H(p)/CuO (P)/a-Si:H(n) solar cell is simulated and studied. The performance of solar cells, especially short-circuit current (Jsc), fill factor (FF) and conversion efficiency (ƞ), has been significantly improved by the CuO metal oxide absorber layer. The influence of the thickness of the absorbing layer, the band-gap of the CuO absorbing layer, the concentration of the acceptor, as well as the effect of working temperature on the photovoltaic parameters of the proposed solar cell are examined and promising results have been obtained. Indeed, the yield goes from 11.29 % for conventional p-i-n hydrogenated amorphous silicon to 26.39 % for the new hetero-junction structure.

The optoelectronic domains of two-dimensional single-layer ZnTe in compressive and tensile deformations are studied. The calculations are performed within the framework of density functional theory within a revised generalized gradient approximation. The authors' results show that unstrained 2D-ZnTe represents an indirect (K→Г) semiconductor with a band-gap of 1.17 eV. The magnitude of the energy band gap increases when the strain varies from −6% to −2% when the deformation is compressive, its nature remains unchanged. A tensile strain can modify the kind of the gap from indirect to direct transition. The tensile deformation can change the type of transition from an indirect transition to a direct transition, giving the chances of applications of the 2D-ZnTe monolayer in flexible optoelectronics. Compressive strain is found to reduce the energy-gap by moving it toward the infrared regime, while tensile strain affects both the magnitude and type of the gap. The optical spectra exhibit an anisotropic behavior in the x and z directions. These spectra are shifted toward the region of low (high) photon energies under tensile (compressive) stress. The reflectivity structure values for the unstrained 2D-ZnTe monolayer are recorded as 13 % and 2.43 % along x and z axes, respectively. The monolayer locally presents sufficiently significant optical damping which is negligibly deteriorated by deformations. The merits of 2D-ZnTe monolayer on the x-axis for solar cell implementations have been demonstrated. A transparent nature of the monolayer of interest, unconstrained and constrained, is noted for a wide domain of the solar spectrum covering the infrared and visible zones of the electromagnetic spectrum.

In this study, the effect of potential and deposition times on the electrochemical, structural, morphological and optical properties of CdS films obtained by electrodeposition was investigated. The results obtained during the different characterizations carried out show that the films present different phases with the presence of the same CdS composition. Electrochemical characterization by cyclic voltammetry allowed us to determine the electrochemical range of the potential corresponding to the formation of CdS. X-ray diffraction analysis indicated that the CdS nanostructures has a polycrystalline nature and orthorhombic system and preferential orientation along the (420) plane. Surface morphological studies by (AFM and SEM) revealed the presence of nano-crystalline grains and all the deposited films have almost uniform grain size and well covered on the surface of the substrates. Composition analyses showed high stoichiometry, and the S/Cd atomic ratio is close to one. Optical studies showed that the average transmittance of the deposited films as a function of electrochemical parameters in the visible and near infrared regions is approximately (20–70)%, and the band gap ranged from (2.25 to 2.45) eV. The optical transmission of deposits varies randomly with increasing potential.

Lead-free halide double perovskite materials have recently attracted considerable interest from the scientific community due to their vast potential in optoelectronic applications without toxicity issues. In this research, the physical properties of double halide perovskites (DP) were theoretically analyzed using the full-potential linearized augmented plane wave (FPLAPW) approach within the framework of density functional theory (DFT). The generalized gradient approximation (GGA) was utilized to compute key physical properties. The stability of both perovskites was confirmed through volume optimization curves and corresponding formation energies. Furthermore, electronic properties were assessed, and the band gap was determined. The results reveal semiconducting behavior with a direct band gap of 2.6 eV, suggesting its potential for solar cell applications.

The potential of halide perovskites has transformed the field of optoelectronics and energy conversion. In this study, the physical properties of double halide perovskites (DP) were investigated theoretically using the full-potential linearized augmented plane wave (FPLAPW) method within the framework of DFT. The generalized gradient approximation (GGA) was employed to calculate relevant physical characteristics. Stability for both perovskites was verified through volume optimization curves and corresponding formation energies. Additionally, electronic properties were examined, and band-gap were calculated. The findings indicate a semiconducting behavior with a direct band-gap of 2.6 eV, highlighting its potential for solar cell applications.

First-principles calculations were carried out to study the electronic structure and mechanical and hydrogen storage properties of calcium bis(tetrahydridoborate) using density functional theory. The obtained equilibrium lattice parameters are in good agreement with the available experimental data. The stability of the structure at zero pressure is determined by the calculation of the elastic coefficients. Nevertheless, the existence of elastic anisotropy in the compound demonstrates its lower compressibility along the c-axis than the a- and b-axes. F2dd-Ca(BH4)2 is nonmetallic with a wide band gap of 5.54 eV. In this regard, Ca(BH4)2 is promising for hydrogen storage applications at the expense of its high hydrogen volume density of 130 g/L (more than that of liquid hydrogen) and a hydrogen gravimetric density of 11.46 wt%, exceeding the U.S. Department of Energy's 2025 goal of 5.5 wt%.

Electron and positron chemical potentials, positron affinity and bulk lifetime, positronium work function and positron effective mass have been computed for ZnxCd1−xS using a pseudo-potential approach within the virtual crystal approximation (VCA) and the independent particle model. A correction to VCA is included taking into consideration the disorder effect. This has permitted the computation of the positron affinity to separate materials of interest. The performances indicated that the positron annihilates differently in CdS than in ZnS. The bulk lifetime of positron has been obtained as 241.17 ps for CdS and 215.47 ps for ZnS. Hence, it decreases when going from CdS to ZnS. The positronium work function increases from 2.245 to 3.08 eV when augmenting the composition x from 0 to 1, indicating that only fewer positronium atoms are figured in a specimen surface and ejected for the vacuum. The positron effective mass augments from 0.96 to 1.34 m0 when going from CdS to ZnS materials. The details collected from the assisted investigation are of a former significance for an ameliorate accordance of positron annihilation in ZnxCd1−xS.

The structural, mechanical, and thermoelectric characteristics of layered transition metal dichalcogenides MX2 (M = Zr, Hf; X = S, Se) have been studied using density functional theory along with van der Waals correction. The exchange-correlation functional, enhanced with corrections for van der Waals interactions, has been evaluated for the hexagonal bulk structures of these materials. The analysis of elastic properties reveals that these compounds exhibit brittleness at zero pressure and conform to Born's criteria for mechanical stability. Examination of elastic constants and moduli suggests that the compounds possess reasonable machinability, moderate hardness, and anisotropy in terms of sound velocity. Transport properties, including the Seebeck coefficient, electrical conductivity, thermal conductivity, and power factor, have been computed using the semi-classical Boltzmann theory implemented in the BoltzTraP code. All investigated compounds exhibit excellent thermoelectric performance at high temperatures. This result suggests that our compounds are highly promising candidate for practical utilization in the thermoelectric scope.

The structural, elastic, electronic, and thermodynamic properties of a LiScSi1−xCx alloy in the α-phase were investigated using density functional theory with the plane-wave pseudopotential method and the alchemical mixing approximation in ABINIT code. We computed ground-state properties including lattice constants, bulk modulus, energy gap, refractive index, and optical dielectric constant for the LiScSi1−xCx compounds. Our results align well with existing theoretical data for the parent compounds LiScSi and LiScC. We found that the fundamental bandgap for the α-LiScSi1−xCx alloy varied from 0.865 eV to 1.143 eV using the B3LYP approach, indicating potential applications in optoelectronic devices such as photodetectors and light-emitting diodes (LEDs), where precise control over electronic and optical properties is crucial. Additionally, we calculated the electron and hole effective masses, which showed a decrease with increasing carbon concentration; the electron effective mass ranged from 0.042m* for LiScSi to 0.035m* for LiSiC. The LiScSi1−xCx alloy in the α-phase consistently exhibited direct semiconductor behavior (X → X) across all concentrations. We also predicted the variation in thermodynamic properties, including unit cell volume, bulk modulus, heat capacity, and thermal expansion coefficient, with temperature for various carbon concentrations. These findings contribute to a deeper understanding of the material’s potential applications in electronic and thermoelectric devices.

First-principles pseudo-potential computations established on the density functional perturbation theory have been utilized for calculating frequencies of optical phonons, high-frequency and static dielectric constants, Frӧhlich coupling parameter, Debye temperature of longitudinal phonon frequency and effective polar field for zinc-blende CdxZn1-xS semiconductor ternary alloys. The frequencies of these phonons, and hence the dielectric constants, are found to be composition dependent. The higher the dielectric constant is, the better a material functions as an insulator. The large dielectric constant in CdxZn1-xS is mainly due to a pseudo-potential of low frequency phonons with large mode effective charge. The predisposition of experimental consequences display shapely convention with our datum. Otherwise, our consequences are predictions. The compositional dependence of the features of interest display at all events non-monotonic behavior. The survey may be beneficial for the distinguishing permission of CdZnS-stabilized quantum well apparatus.

A precise and systematic analysis for A2BCl6 [(A = Cs; B = Se, Sn, Te, Ti, Zr) and (A = K; B = Pd, Pt, Sn)] is performed to investigate structural stability as well as optical and electrical properties using pseudopotential plane wave method. The calculated lattice constants show consistency with the experimental results that ensure their structural stability. From the electronic band structure results, Cs2BCl6 (B = Se, Sn, Te, Ti, Zr) and K2BCl6 (B = Pd, Pt, Sn) are established to be within an energy bandgap that varies between 1.131 and 3.731 eV. The metallic behavior of the materials for Cs2BCl6 (B = Ta, W) and K2BCl6 (B = Ta, W, Mn, Mo, Os, Re, Ru, Ta, Tc) is confirmed showing the presence of conducting characteristics. The dielectric function is large in the near-ultraviolet region (3.10–4.13 eV). The extinction coefficient of A2BCl6 has the ability to work for implementations like Bragg's reflectors, optical and optoelectronic devices. The optical parameters of A2BCl6 disclose that the working constructions have an elevated dielectric constant. Analysis of the electronic and optical properties demonstrates that these double-perovskite materials are suitable for photovoltaic and optoelectronic applications.

The manuscript details the application of spray pyrolysis for the deposition of an economically viable transparent conductive oxide film comprised of (Ni/Co) co-doped SnO2 on a glass substrate. The primary objective of this
research was to systematically examine the impact of Ni/Co co-doping on diverse properties of the SnO2 thin film. These properties encompassed the film’s structural composition, surface morphology, optical response, and
electrical behaviors. A comparison was made with pure SnO2 film, as well as SnO2 films doped with 3 %Ni and 1%Co. The results indicate that all the samples exhibited a tetragonal structureThe introduction of Co and Ni
atoms had no impact on the favored alignment of the (110) plane or the crystal structure of the SnO2 film. The crystallite size of the pure SnO2 film, as well as the (Co, Ni)-doped and (Ni/Co) co-doped SnO2 films, varied
within the range of 11 to 20 nm. Scanning electron microscopy (SEM) images were employed to assess how doping and co-doping influenced the surface characteristics of the films. The presence of pores and/or roughness
on the surface resulted in a hydrophilic character and a decrease in the contact angle for the doped films (Ni, Co). However, the co-doped film exhibited a hydrophobic characteristic due to the surface enhancement provided by SnO2:3 %Ni:1 %Co. The research also focused on the optical characteristics of the films, showing a positive impact with the proper incorporation of Ni and Co atoms into the SnO2 lattice. It was notably observed that the
addition of Ni and Co atoms improves the optical properties of the undoped transparent SnO2 film in the visible spectrum, with a high transmittance of 87 % achieved for the Ni-doped film. Furthermore, the hydrophobic
nature achieved by adding a concentration of 3 %Ni to the SnO2:1 %Co film enhances its optical transmission in the range of 300 nm to 750 nm. The SnO2 film shows an improvement in the electrical resistivity upon doping and co-doping with low resistivity value of 2.22 × 10− 2 Ω.cm for the film (3 %Ni/1 %Co)-SnO2. Drawing from these insightful results, the study proposes the potential utilization of (Ni/Co) co-doped SnO2 films as transparent electrodes in optoelectronic applications, especially in the manufacturing of thin film solar cells.

As part of this study, we elaborated and characterized samples of thin layers of cobalt oxide, doping them with diferent concentrations of nickel (2%, 4% and 6%). These flms were deposited on ordinary glass substrates at a temperature of 400 °C, with a deposition time of 5 min, using the spray pyrolysis technique. The main objective of this research was to explore the infuence of nickel doping on the physical properties of cobalt oxide. The
results obtained by Raman spectroscopy confrmed the presence of Co+2 cations located in tetrahedral sites and Co+3 in octahedral sites, thus validating the spinel-type cubic structure. Morphological analysis revealed that the incorporation of nickel into the Co3O4 thin flms, synthesized by spray pyrolysis, resulted in a signifcant transformation of the porous surface morphology. This transformation resulted in the transition from a porous structure to a dense and uniform confguration, characterized by nanofower grains. Analyzes by EDS spectrometry revealed peaks associated with the elements Co and O, thus confrming the composition of the flms. An improvement in the durability and overall performance of the solar device in humid environments by obtaining the hydrophobic character (CA=99°) for the Co3O4/6%Ni flm. The transmittance decreased with increased as a function of Ni concentration. Optical studies show direct band gaps Eg1 and Eg2 varying between 1.41 and 1.3 eV and between 2.09 and 1.99 eV respectively. Notably, the electrical resistivity experienced a signifcant decrease from 28.39 to 0.178 Ω.cm for the undoped and 2% Ni-doped flms, respectively. However, for Ni concentrations≥4%, the electrical resistivity increased from 3.47 to 10.2 Ω cm.

The effect of compressive strain and tensile strain on the band structure and optical spectra of two-dimensional monolayer GaN has been investigated. Computations were performed within density functional-theory. The results show that tensile two-dimensional monolayer-GaN undergoes an indirect-to-direct transition, which makes the material suitable for light-emitting and laser diodes. The material of interest is found to exhibit different optical properties dependent on the strain. Besides, the absorption band becomes wider and the optical absorption coefficient is reduced negligibly by strain, making two-dimensional-GaN a good candidate for application in photovoltaics and flexible optoelectronics.

Using the projected augmented wave pseudo-potentials (PAW) approach and the generalized gradient approximation (GGA) of Perdew–Burke–Ernzerhof (PBEsol) in the framework of the density functional theory as implemented in the Quantum Espresso code, the mechanical behaviour as well as the thermo-physical properties of LiAl2X (X = Rh, Pd, Ir and Pt) ternary intermetallic compounds under high hydrostatic pressure up to 10 GPa have been predicted. Our finding on the elastic stiffness constants, aggregate elastic modulus, Debye temperature, limiting angular vibrational frequency, vibrational energy as well as the vibrational free energy of LiAl2X (X = Rh, Pd, Ir and Pt) compounds shows that all these quantities increase monotonically with increasing pressure up to 10 GPa; while the elastic compliance constants (except S12), the vibrational entropy and the constant volume heat capacity of LiAl2X (X = Rh, Pd, Ir and Pt) decrease monotonically with increasing pressure. At room-temperature and zero-pressure, the obtained values of the Debye temperature θD are 486.10 K for LiAl2Rh, 462.51 K for LiAl2Pd, 401.36 K for LiAl2Ir and 406.62 K for LiAl2Pt, respectively; while at room-temperature and pressure of 10 GPa, the values obtained of θD are around: 528.29 K for LiAl2Rh, 507.80 K for LiAl2Pd, 428.81 K for LiAl2Ir and 442.88 K for LiAl2Pt, respectively. In addition, the analysing of the generalized mechanical stability criteria under isotropic pressure shows that all our materials of interest are mechanically stable up to 10 GPa.

The full-potential linearized augmented plane wave (FP-LAPW) approach of density functional theory has been utilized to systematically analyze the AgCoFeZ(Z = Al,Ga,Si,Ge, Sn), NiFeCrZ(Z = Al,Si,Ge,In) and NdCoMnGa materials. The electronic band structure and density of states (DOS) are determined using GGA, GGA + U, mBJ, mBJ + U and SCAN approximations. AgCoFeGe, AgCoFeSn, NdCoMnGa and NiFeCrAl exhibit half-metallic (HM) properties when their equilibrium lattice constants are optimally adjusted in the normal state and themagnetic moment of the alloys satisfies the value prescribed by the Slater-Pauling rule.We have analyzed the calculated DOS and energy bands of the alloys, and investigated the mechanism behind the formation of the HM band gap based on our research findings. The excellent HM property gives a good candidate for spin polarized material. Using spin density functional theory calculations, it is found that the given compounds are metallic in both spin channels. The thermoelectric properties have also been investigated in terms of Seebeck, electrical conductivity, thermal conductivity, power factor and figure of merit.

Lattice parameters, band-gap energies, optical transitions and exciton properties of ZnSe at high-pressures up to 100 kbar have been studied using a pseudo-potential method. Results are generally in good agreement with experiment at zero pressure. Adachi's expression formula for exciton binding energy and Bohr radius are adjusted giving a significant accordance with experiments. A very good accord is acquired between our obtained consequences concerning the refractive index and the high-frequency dielectric constant when using Hervé and Vandamme model. Upon compression up to 100 kbar, ZnSe remains a direct (Γ-Γ) semiconductor. The lattice parameter decreases from 5.6692 to 4.9075 Å, whereas the valence band width increases from 11.47 to 15.35 eV. A monotonic behavior has been found for all parameters of interest under hydrostatic pressure.

The outcomes of computational study of electronic, magnetic and optical spectra for A2BX6 (A = Rb; B = Tc, Pb, Pt, Sn, W, Ir, Ta, Sb, Te, Se, Mo, Mn, Ti, Zr and X = Cl, Br) materials have been proceeded utilizing Vanderbilt Ultra Soft Pseudo Potential (US-PP) process. The Rb2PbBr6 and Rb2PbCl6 are found to be a (Г-Г) semiconductors with energy gaps of 0.275 and 1.142 eV, respectively making them promising photovoltaic materials. The metallic behavior of the materials for Rb2BX6 (B = Tc, W, Ir, Ta, Mn, Sb, Mo) has been confirmed showing the attendance of conducting lineaments. The dielectric function is found to be large close to the ultraviolet districts (3.10 - 4.13 eV). The extinction coefficient of the Rb2BX6 has the ability to be used for implements. The band structures and density of states ensure the magnetic semiconductors’ nature of the Rb2Mn (Cl, Br)6 perovskites. The total calculated magnetic moment of Rb2MnCl6 and Rb2MnB6 is 3.00μβ. Advanced spintronic technology requires room-temperature ferromagnetism. The present work confirms that, bromine and chlorine-founded double perovskites are extremely attractive for photovoltaic and optoelectronic devices.

In the present work, thin films of ZnO co-doped with Co and Cu cations were obtained on glass substrate, combining the sol gel process and spin-coating technique. For the compound, the general chemical formula used was: Zn1-x-zCoxCuzO, [(x; z) = (0.00; 0.00), (0.02; 0.02), (0.04; 0.04) and (0.06; 0.06)]. For pure ZnO film, the surface morphology is composed by small spherical grains that present interstitial spaces, while the films obtained from the simultaneous Co and Cu insertion in the ZnO structure are more dense and interstitial spaces disappear. For all films, the X-ray diffraction patterns testify the monophasic phase formation, typical of the hexagonal structure of ZnO. In addition, the films presented preferential orientation in the (002) direction. It was demonstrated that the Zn2+ cations by Co2+ and Cu2+ cations replacement, causes relevant modifications in the lattice parameter (c), crystallite size (D), dislocation density (δ), strain (εc) and stress (σc) of the hexagonal structure wurtzite from ZnO. The Co and Cu cations inclusion in the ZnO host lattice, alto caused a decrease in the optical band gap energy (3.37 for 3.16 eV), which is related to the charge transfer between the 4f level electrons and the conduction band or valence band of ZnO. Finally, for all films thin the linear and non-linear optical constants were computed and analyzed, showing variations that depend on the concentration of the dopant cations.

Spinel thin flms Co3O4 have been deposited at a temperature of approximately 400 °C using spray pyrolysis. The testimony process was carried out with diferent deposition times (4, 5, 6, and 8 min), indicating that the flms were grown for varying durations. The objective of varying deposition times of the thin flms of Co3O4 was to optimize the fabrication of a hetero-junction between Co3O4 and ZnO. XRD, SEM and Raman investigations showed that pure cubic Co3O4 with an irregular spindle shaped particles have been successfully obtained. The flms’ thickness increased under prolonged preparation times leading to a denser surface. The optical measurements revealed that the thin layer with a deposition time of 8 min atained a total absorbance of 98% in the apparent spectrum with a band gap of 1.27 eV. The I–V characteristics recorded of FTO/ZnO/Co3O4/Au cells
showed that all devices exhibiting a rectifying behavior with a perfect factor that varies between 3.87 and 1.64. Our results suggest that Co3O4 at 8 min with a carrier density of 2.414 × 1014 cm−3 and high absorbance is potentially a competitive hole transport material in spinel solar cells, and, the recorded characteristics of the photovoltaic phenomenon were noted a short circuit current of 1.302 mA, an open circuit voltage of 369 mV and a fll factor of 32%.