Tungsten oxide WO₃₋ₓ thin films were synthesized using the spray pyrolysis technique on glass substrates heated to 350 °C, employing tungsten hexachloride (WCl₆) as the precursor. The films were annealed at the same temperature for 5 hours. Their structural properties were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD analysis revealed that the as-deposited films crystallized in a monoclinic W₁₈O₄₉ (WO₂.₇₂) phase, while annealing induced a phase transformation to tetragonal W₅O₁₄ (WO₂.₈). Optical measurements indicated a wide direct optical band gap of 3.5 eV for WO₂.₇₂, which increased to 3.8 eV for WO₂.₈ after annealing, accompanied by a reduction in Urbach energy. Electrical properties were analyzed using impedance spectroscopy in the frequency range of 100 kHz–13 MHz at temperatures between 200 and 275 °C. Nyquist plot fitting revealed contributions from both grain interiors and grain boundaries to the relaxation process, with a non-Debye poly-dispersive behavior. Additionally, the activation energy decreased post-annealing. The as-deposited films exhibited excellent photocatalytic performance in the degradation of methylene blue under solar irradiation. This enhanced activity was attributed to the presence of oxygen vacancies and a comparatively lower band gap relative to the annealed films. This study not only highlights the phase transformation of WO₃₋ₓ to WO₃ induced by thermal annealing but also demonstrates the potential of WO₂.₇₂ thin films in photocatalytic dye degradation applications.

ZnS thin films were synthesized using the spray pyrolysis technique at 350 °C. Following the annealing process, X-ray diffraction (XRD) analysis was performed to examine the structural characteristics of the films. This analysis revealed a gradual substitution of sulfur by oxygen during an extended annealing period, leading to the transformation of the samples into a mixed phase consisting of ZnS, ZnO, and a substitutional solid solution Zn(S,O). The surface morphology and elemental composition of the treated films were investigated using Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDX) and profilometry. These crystalline particles of growing ZnO phase adopt a hexagonal shape, displaying well defined edges and smoother surfaces, with dimensions of approximately 600 nm. Moreover, a change in surface properties, marked by a transition from hydrophilic to hydrophobic behavior, was observed. The optical characteristics were examined through transmittance, reflectance and absorbance spectra, recorded in the range of 200–2500 nm. Films with a high percentage of ZnO are more absorbent in the UV range and have a narrower bandgap energy. Additionally, the photocatalytic activity was evaluated by monitoring the degradation of an aqueous solution of methylene blue (MB) when exposed to sunlight. Enhanced degradation of MB dye was observed as the amount of zinc oxide in the annealed samples increased.

This study examines the physical characteristics of Co2Te3O8 in the spiroffite structure using an ab initio approach. The optimization of the Co2Te3O8 structure, in both nonmagnetic and magnetic states, indicates that the magnetic state is more stable than the non-magnetic one. Thermodynamic properties under various temperatures and pressures, calculated via the quasi-harmonic approximation, reveal that the specific heat capacity of spiroffite Co2Te3O8 conforms to the Debye model and satisfies the Dulong and Petit limits. The electrical, magnetic, and optical properties of Co2Te3O8 are investigated using the GGA and TB-mBJ approximations. Analysis of the density of states and the band structure indicates that spiroffite Co2Te3O8 exhibits semiconductor characteristics in both the spin up and spin down channels. The study is extended to apply hydrostatic pressure to assess the electronic and magnetic properties of both unstrained and strained structures of Co2Te3O8. It is found that within the investigated pressure range (0–15 GPa), no structural changes are observed. Furthermore, a slight decrease in the spin up gap is noted, while no appreciable changes are observed in the spin down gap. Moreover, the investigation into the spin-polarized thermoelectric properties of the material reveals that it achieves a high figure of merit, approximately 0.99, across broad temperature spectra. This performance highlights its suitability as a candidate for thermoelectric power generation. Finally, optical properties calculations on spiroffite Co2Te3O8 reveal efficient absorption in the ultraviolet region.

Technological development cannot take place without a deep knowledge of materials and their physical properties. Complex oxides constitute a family of materials characterized by specific characteristics prompting them for potential technological applications. The results of a theoretical study related to the structural, thermodynamic, electronic, optical, and magnetic properties of the Dy 2 Be 2 GeO 7 complex oxide are presented. The current study is accomplished using the “Full Potential (FP) Linearized (L) Augmented Plane Wave Plus Local Orbitals (APW + lo)” formalism as incorporated in the WIEN2k computational code in the “density functional theory” framework. To approximate the exchange and correlation effects, the PBE-GGA formalism of the “generalized gradient approximation” is used. Furthermore, “Tran-Blaha modified Becke–Johnson potential” is used to better describe the electronic structure. The equilibrium structural parameters are in good agreement with the corresponding measured data reported in the literature. The thermodynamic properties of the title compounds are explored via the quasi-harmonic approximation over temperature and pressure ranges from 0 to 700 K and 0 to 10 GPa, respectively. The electronic properties are determined with spin-polarized inclusions. Finally, the optical properties are examined with a detailed discussion of different optical parameters, including dielectric function, absorption coefficient, optical conductivity, reflectivity, and refractive index spectra. The Dy 2 Be 2 GeO 7 complex oxide with a non-centrosymmetric tetragonal structure shows a negative birefringent, therefore it is a possible candidate for applying to the birefringent field and nonlinear optical process. To our best knowledge, the current study is the first effort to explore the physical characteristics of the considered complex oxide.

Tungsten oxide WO3-x thin films were prepared by spray pyrolysis technique on glass substrates heated at 350 °C using a solution of tungsten chloride (WCl6) with low molarity of 3.10-3 M. The films were annealed at the same temperature for 5h. The structural properties were investigated using X-ray diffraction (XRD) and scanning electronic microscopy (SEM) techniques. XRD data indicates the presence of W18O49 (or WO2.72) films with monoclinic symmetry for as-deposited films and tetragonal W5O14 (or WO2.8) after annealing. The optical results show large direct optical gap of 3.5 eV for WO2.72 which reaches 3.8 eV in the case of WO2.8 accompanied with a decrease of Urbach energy. The electric properties of WO3-x films was studied using impedance spectroscopy technique in the frequency range 100 kHz–13 MHz at various temperatures (200 – 275 °C).

Un-doped, Zn-doped, and Al–Zn co-doped CdO thin films were deposited onto glass substrates at 350 °C by spray pyrolysis. X-ray diffraction (XRD) analysis was conducted to investigate the structural properties of the films. The XRD patterns confirmed that all the films crystallize in a cubic structure and that the addition of Zn and Al did not alter the CdO crystal structure. Energy-dispersive X-ray spectroscopy analysis further confirmed the successful incorporation of Zn and Al into the CdO films. Theoretical calculations based on first-principles were performed, and crystallographic information files (CIF) were obtained for optimized theoretical supercells in space group Pm3-m. The CIF files were used as input for experimental XRD spectra Rietveld refinement, to determine the Wyckoff positions of the dopants and their occupation rates. The optical properties of the films were characterized using transmittance measurements in the wavelength range of 300–1700 nm. The optical data indicated an increase in the average transmittance from 60 to 70% within the wavelength range of 600–1700 nm upon Al–Zn co-doping. The estimated direct optical band gap of the un-doped, doped, and co-doped CdO thin films is varied between 2.41 and 2.50 eV. All the samples exhibited n -type conductivity with low electrical resistivity of about 1.32 × 10 –4 Ω⋅cm. Co-doped CdO thin films with 1% Al and 3% Zn exhibited higher carrier concentration (4.39 × 10 +20 cm −3 ) than the other samples.

TM (TM = Sn, Al) doped and co-doped CdO thin films were deposited by spray pyrolysis technique on glass substrate at temperature 350 ˚C. The effect of TM doping and co-doping on the structural, morphological, optical, and electrical properties of CdO thin films was investigated. The obtained films are crystallized in the cubic structure and oriented along the preferential (111) crystallographic plane. The average optical transmittance reaches 79% in the visible range for Sn doped CdO films and 74% for Al-Sn co-doped films. The gap values of the obtained samples are between 2.29 and 2.49 eV. All the deposited films exhibit n-type conductivity with a low electrical resistivity of 7.85.10-4 Ω.cm obtained for Al doped CdO films.

The present work is a theoretical study of the structural and spin-polarized dependent optoelectronic thermoelectric properties of the melilite-typeGd2Be2GeO7 compound, using the full potential linearized augmented plane wave approach in the framework of density functional theory. The predicted structural parameters are in good accordance with the measured counterparts. It is found that the title compound is more stable in the ferromagnetic order than in the non-magnetic order. The calculated band structure using the modified Becke–Johnson potential reveals that the studied compound has a wide bandgap of 3.78 eV. The frequency-dependent linear optical spectra are studied in an energy range expanding from 0 to 30 eV. Finally, the semi classical Boltzmann theory as incorporated in the Boltztrap code is used to study the spin-polarized dependent transport properties. The obtained results show that Gd2Be2GeO7 is a potential candidate for conversion energy device applications.

Titanium dioxide (TiO2) thin films are deposited onto glass and silicon < 100 > substrates by high power impulse magnetron sputtering (HiPIMS) at various substrate positions from the substrate-holder center (x = 0, 10, 20 and 30 mm). The structural analysis conducted through XRD and Raman spectroscopy shows that all the films deposited at lower radial distance (x = 0-20 mm) are identified as pure anatase phase of TiO2, while those deposited at 30 mm contain a small trace of rutile phase with anatase phase remaining dominant. AFM analysis reveals homogenous surfaces with low values of roughness (2.6-3.8 nm) and a decrease of grain size with the substrate position. The films exhibit high refractive index and large indirect optical band gaps (3.25-3.38 eV). Finally, UV-blocking and antireflection characteristics are studied.

In this paper, we present the results of a detailed computational study of the structural, electronics, optical, thermodynamic, and thermoelectric properties of the AgXO2 (X = In, Y) materials with delafossite-type structure, by using the "full-potential linearized augmented plane wave (FP-LAPW)" method. The calculated structural parameters of the title compounds are in excellent agreement with the available theoretical data. We have explored the dynamical stability of the AgXO2 compounds by investigating the phonon dispersion curves. The optoelectronic characteristics of the studied compounds were accurately described at the level of the "Trans Blaha modified Becke-Johnson (TB-mBJ)" approach to model the exchange-correlation potential. On the other hand, the optical characteristics of the AgInO2 and AgYO2 thin films were investigated in the wavelength range 200-750 nm for three different thicknesses: 300, 600 and 1300 nm on a transparent substrate (glass: n(glass) = 1.5, k(glass) = 0). Thermodynamic and thermoelectric properties of the considered compounds were predicted by employing the "quasi-harmonic Debye model" and the Boltzmann transport theory.

SnO2 including different concentrations of ZnO has synthesized using spray pyrolysis technique for preparing on glass substrate at 350 degrees C. Effect of ZnO ratio has been researched to study optical and structural properties of SnO2. X-ray diffraction scheme indicates the presence of different peaks that attribute to a mixture of rutile SnO2 and hexagonal ZnO. The crystallite size of SnO2 decreases as ZnO ratio increases. The synthesized nano-composites are characterized via field emission-scanning electron microscopy. The reflectance and transmittance in the wavelength range, 200-2500 rim have been measured. The direct band gaps vary from 3.04 to 3.78 eV to show contrary concept to Ubach's energy. The refractive index and extinction coefficient display vibrations due to ZnO ratio effect. Dielectric constants of SnO2 are deduced effectively in terms of ZnO ratio using Maxwell-Garnett 's effective medium theory, they are compared with experimental spectra. The optical properties can be interpreted correctly with Maxwell-Garnett theory of small underestimation, indicating that adaptation of optical properties can take place by varying the volume fraction. Our results present good agreement with experimental data.

Silver chloride thin films were easily prepared for the first time by direct spraying of silver chloride (AgCl) solution with low molarity on glass substrates heated at 200 degrees C, 250 degrees C, 300 degrees C and 350 degrees C. The X-ray diffraction (XRD) data showed that the films have cubic symmetry and are subject to compressive and tensile strains. Transmission electron microscopy revealed the presence of Ag nanoparticles (NPs) of different sizes embedded in AgCl thin films. These nanoparticles were roughly spherical and well crystallized in the case of the film prepared at 350 degrees C. The Raman and X-ray photoelectron spectroscopy confirmed the XRD results. The UV-vis-NIR spectroscopy indicated a low reflectance with antireflecting properties and high optical transmission superior to 80 % at 350 degrees C. The obtained films have wide indirect band gap and exhibit localized surface plasmon resonance (LSPR) peak at 407 nm at deposition temperature of 350 degrees C due to the presence of Ag NPs.

Un-doped, Al-doped, and Sn-Al co-doped ZnO thin films have been successfully synthesized by Spray Pyrolysis method. Zinc Nitrate (Zn(NO3)(2)), Tin Chloride (SnCl2) and Aluminum Nitrate (Al (NO3)(3)) were used as starting chemicals at different compositions. Films depositions were carried out on glass substrates at 350 degrees C. The X-ray diffraction confirmed that the Al-Sn co-doping did not change the ZnO Hexagonal Wurtzite structure. The obtained un-doped ZnO films were highly oriented along the preferential (002) crystallographic plane while the Sn-Al co-doped ZnO films were disoriented with slight loss of crystallinity. The optical measurement showed an increase of the average transmittance from 65 % to 81 % and the band gap energy (E-g) from 3.23 to 3.30 eV. The electrical conductivity has increased with the Al-Sn co-doping concentration to reach the value of 0.335 (Omega.cm)(-1).

Bismuth sulfide Bi2S3 thin films were deposited by Spray Pyrolysis method at 260 degrees C. X-Ray Diffraction has been used to investigate the crystalline structure and the crystallite size of Bi2S3 thin films. The optical band gap has been determined by UV-VIS-NIR spectrophotometry. Using the measured absorption coefficient data, we estimated the expected absorption capacity and photocurrent of the thin films. The deposited thin films yield a maximum photocurrent of 33.6 mA/cm(2). Hall-effect measurements showed that Bi2S3 thin films have a lower value of resistivity of 2.82x10(-2) Omega cm. This value is optimal for the improvement of solar cells based Bi2S3 thin films. AC conductivity obeys to the relation A omega(s). The decrease of the exponent S with temperature reveals to understand the behavior hopping model CBH. The density of states N(Ef) was in order of 10(18) eV(-1) cm(-3).

Bi2S3)(x) (gamma-MnS)(1-x) composite thin films have been deposited onto glass substrates using spray pyrolysis method. The structural and compositional investigations confirmed the co-existence of Bi2S3 and gamma-MnS binary compounds in the thin films. The surface morphology indicated that the increase in Bi2S3 concentration influences both the shape and the size of gamma-MnS crystallites. The optical analysis via transmittance and reflectance measurements revealed that the band gap energy E-g decreased from 3.29 eV to 1.5 eV in terms of Bi2S3 content. The electrical parameters such as resistivity., mobility mu, carrier concentrations and Hall coefficient have been obtained by Hall Effect measurements. It is found than incorporation of Bi2S3 enhances the conductivity, and p-type conduction of gamma-MnS could be converted to n-type at x = 0.5. The vibrating sample magnetometer measurement has revealed that (Bi2S3)(x) (gamma-MnS)(1-x) composite thin films have a ferromagnetic behavior at room temperature.

SnO2 thin films were deposited on glass substrates at 350 degrees C by spray pyrolysis technique for different deposition times (i.e. 4, 7, 10 and 13 min) from fin chloride (SnCl2, 2H(2)O). The X-ray diffraction analysis showed that all the synthesized films correspond to the tetragonal structure of SnO2. Depending on the deposition time, the estimated average crystallite size varied from 29 to 55 nm using Williamson-Hall analysis (36 to 65 nm using the Scherrer method). Atomic force microscopy analysis revealed homogenous surfaces with low values of roughness (9.9 to 27.7 nm). As measured by spectroscopic ellipsometry, the thickness of the films was ranging from 150 to 350 nm. The obtained SnO2 films displayed an average transmittance of 80% and a direct optical band gap ranging from 3.98 to 4.09 eV. The Hall-effect measurements revealed that all the films are conducive with values of conductivity varying from 32.3 up to 127 Omega(-1). cm(-1). From the obtained morphological, optical and electrical results, we conclude that spray pyrolysed fin oxide thin films are good candidates to be used in different fields, mainly in solar cell applications.

The present work aims at investigating the electronic, optical, photovoltaic and thermoelectric properties of AgBiS2 compound using the density functional theory (DFT) and the modified Becke-Johnson exchange-correlation potential (mBJ). Both hexagonal Matildite and cubic Schapbachite polymorphs were considered. The hexagonal phase is found to be indirect gap semiconductor with band gap energy of about 1.07 eV and high absorption coefficient of 10(6) cm(-1), whereas the cubic phase were metallic. The analysis of band alignment of Matildite with some binary oxides and sulfides revealed interesting results. The photovoltaic properties of AgBiS2 confirmed that Matildite phase could achieve a short-circuit current of 22 mA/cm(2) and conversion efficiency of 20%. Also, we demonstrated that including photon recycling with a proper solar cell design could improve the conversion efficiency. Moreover, interesting thermoelectric performance has been confirmed.

gamma-MnS thin films were prepared on glass substrate by spray pyrolysis method at 280 degrees C. The optical constants and thickness of the films were extracted using the pattern search optimization technique in combination with a seed preprocessing procedure (spPS). Refractive index dispersion of the films was analyzed by using the concept of the single oscillator model. The values of the oscillator energy, E-0, and the dispersion energy, E-d, were determined as 8.83 eV and 5.65 eV, respectively. The analysis of the optical properties of the gamma-MnS film showed a direct transition with energy band gap of 2.74 eV. Utilizing Hall Effect measurement, we have determined values of the resistivity. which equals to 1150 Omega cm. The positive value of hall coefficient showed a p-type in nature of the obtained thin film. The maximum of photocurrent density estimated by Yablonovitch limit is equal to 46 mA/cm(2).

(SnS)(m)(Sb2S3)(n) thin films were prepared by thermal evaporation using the glancing angle deposition technique (GLAD). The incident angle between the particle flux and the normal to the substrate was fixed at 80 degrees. The Raman and XRD characterization revealed the amorphous character of the films due to the columnar structure as shown by the SEM characterization and AFM analysis. A strong change of the surface morphology of the films was observed and it depends on the composition. Optical properties were extracted from transmittance T and reflectance R spectra. (SnS)(m)(Sb2S3)(n) thin films exhibit high absorption coefficients (10(4)-2 x 10(5) cm(-1)) in the visible range and the higher values were obtained for Sn3Sb2S6 and it has the highest photocurrent values. The direct band gap (E-g dir) was in the range 2.11-1.67 eV. The refractive indices are calculated from optical transmittance spectra of the films. The Sn3Sb2S6 sample exhibits a lower refractive index. All the dispersion curves of refractive index match well with the Cauchy dispersion formula and they were analyzed using Wemple-DiDomenico model. The Bruggeman effective medium approximation EMA was used to calculate the packing density of different compositions, and SnSb4S7 sample has the highest value. The so-called Verdes coefficient was evaluated from refractive index dispersion, and it was enhanced near the band gap.

We report computational results on the optical response of quarter-wave periodic, modified periodic and optimized photonic crystals based on Ge and MgF2 materials. Transfer matrix method and pattern-search optimization algorithm have been combined to achieve high performance structures destined to spectral control in thermophotovoltaic systems. Our computations demonstrate that the pattern-search algorithm is readily applicable to optimal design of photonic crystals within reduced computing time. High optical performance and spectral efficiency have been achieved.