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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 106 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/cm2 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.

International audience; 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 °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 (Eg) 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 (Ω.cm)−1.

International audience; (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°. 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 (104–2 × 105 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 (Eg 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 Verdet 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.

Protecting from solar radiation remains a very stimulating field of research and development. Improvement of performances of UV/IR radiation shielding devices is thus constantly pursued. With increase of computer strength and code efficiency, simulation becomes a real asset in this investigation. In this study, we report an efficient multiscale simulation protocol to design and optimize such photonic devices based on polymers. The simulation approach combines atomistic-level techniques, i.e. classical molecular mechanics, and linear scaling-DFT in order to get full description of the optical properties of polymers over a large wavelength range. At each step of the procedure, validation with experimental data is carried out, confirming the accuracy of the approach. The resulting optical constants enable designing of a multilayer photonic heterostructure purposely optimized for UV/NIR-radiations protection. The ensuing simulated device reveals very promising optical performance. It exhibits a transparency higher than 90% in the visible range and shows high UV absorptance. Moreover, a strong NIR-shielding ability of 96% is achieved.

Mixed thin films of (SnS 2 ) x (CdS) 1−x (0 ≤ x ≤ 1) were deposited by spray pyrolysis technique decomposition of aqueous solutions of Cadmium chloride (CdCl 2 ) and Tin chloride (SnCl 2 ) on glass substrates at a substrate temperature of 350 °C. Structural properties of the obtained films were studied by X-ray diffraction analysis. The surface morphology and elemental analysis of the films has been examined using scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDX). Optical properties of the deposited films were obtained using transmittance measurements in the wavelength range [200–2500 nm].Some optical parameters such as, high frequency dielectric constant e ∞, lattice high frequency dielectric constant e L and the dispersion parameters (oscillation energy E 0 and the dispersion energy E d ) were estimated by analyzing the refractive index data. The direct optical band gap value of these films varies from 2 to 2.41 eV. We have observed that (SnS 2 ) x (CdS) 1-x thin films conductivity obeys the Meyer–Neldel rule (E MN = 32 meV), which is interpreted as disorder parameter. The room temperature electrical resistivity of CdS (x = 0) films was found to be 2.22 10 +4 Ω cm and it decreases when content of Sn in mixed films increases and reaches the optimum value of resistivity 2.32 10 −2 Ω cm for the concentration x = 0.5. The carrier concentration was found to vary from −1.26 10 +12 to −4.50 10 +20 cm −3 and corresponding hall mobility varied from 6.51 10 +1 to 2.64 10 +1 cm 2 /VS.

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: nglass = 1.5, kglass = 0). Thermodynamic and thermoelectric properties of the considered compounds were predicted by employing the “quasi-harmonic Debye model” and the Boltzmann transport theory.

The optical absorbance of four ternary thin films, i.e. MgSiP2, MgGeP2, MgSiAs2, MgGeAs2 have been theoretically examined over a wide range of wavelength from 300 nm to 800 nm. The combination of first-principle electronic structure calculations and the optical matrix approach for modeling the multilayer assembly have been employed for theoretical studies. The analysis of the calculated absorbance spectra at room temperature with unpolarized light and normal incidence, revealed that MgGeAs2 with a direct energy band gap of 1.6 eV exhibit a considerable high optical absorption, where a thickness of 3.2 μm of this thin film is sufficient to absorb 90% of the incident light and generates a maximum photocurrent of ∼23 mA/cm2.

(Sn2S3)x(Bi2S3)1-x (x = 0, 0.2,0.5, 0.8 and 1) composite thin films have been prepared for the first time by the spray pyrolysis method on glass substrates using Tin chloride (SnCl2–H2O) and bismuth chloride (BiCl3) as precursors. The films were characterized by X-Ray diffraction (XRD), Scanning electron microscopy (SEM), optical absorption and electrical resistivity measurement techniques. XRD studies revealed that all the films contain both binary phases, i.e. Sn2S3 and Bi2S3. The band gap energy of these films varies from 1.56 to 2.01 eV. The dispersion parameters of the composite thin films were determined using e single-oscillator model. The films exhibited the lowest electrical resistivity of 5.59 × 10−2 Ω cm with an activation energy of 0.179 eV for the composition x = 0.2.

International audience; 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 °C, 250 °C, 300 °C and 350 °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 °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 °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 °C due to the presence of Ag NPs.

(Bi2S3)x (γ-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 γ-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 γ-MnS crystallites. The optical analysis via transmittance and reflectance measurements revealed that the band gap energy Eg decreased from 3.29 eV to 1.5 eV in terms of Bi2S3 content. The electrical parameters such as resistivity ρ, mobility μ, 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 γ-MnS could be converted to n-type at x = 0.5. The vibrating sample magnetometer measurement has revealed that (Bi2S3)x (γ-MnS)1-x composite thin films have a ferromagnetic behavior at room temperature.

SnO2 including different concentrations of ZnO has synthesized using spray pyrolysis technique for preparing on glass substrate at 350 °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 nanocomposites are characterized via field emission-scanning electron microscopy. The reflectance and transmittance in the wavelength range, 200–2500 nm 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.

We theoretically investigate the possibility of enhancing light absorption in graphene-based one dimensional photonic crystal. We demonstrate that it is possible to achieve total light absorption at technologically important wavelengths using one-dimensional graphene-based photonic crystals. By means of the transfer matrix method, we investigate the effect of refractive indices and layer numbers on the optical response of the structure. We found that it is possible to achieve one peak, multi-peak or broadband, and complete optical absorption. As a result, the proposed photonic structures enable myriad potential applications such as photodetection, shielding and optical sensing.

SnO2 thin films were deposited on glass substrates at 350 °C by spray pyrolysis technique for different deposition times (i.e. 4, 7, 10 and 13 min) from tin chloride (SnCl2, 2H2O). 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 conductive with values of conductivity varying from 32.3 up to 127 Ω−1. cm−1. From the obtained morphological, optical and electrical results, we conclude that spray pyrolysed tin oxide thin films are good candidates to be used in different fields, mainly in solar cell applications.

A first principles study of structural, electronic and optical properties of zinc aluminum oxide (ZnAl 2 O 4 ) by means of the full potential linear augmented plane wave method is presented. The local density approximation is used for the exchange-correlation potential. A direct band gap of 4.19 eV, in agreement with experiment ( E g =3.9 eV), was determined. ZnAl 2 O 4 is transparent in the visible spectral region; the excitonic transition associated with the fundamental band gap is 4.17 eV. The refractive index value is 1.74 in the ultraviolet spectral region.

We have performed R&D project on methanol synthesis from CO2 and hydrogen in order to contribute to CO2 mitigation. High-performance Cu/ZnO based multicomponent catalysts were developed. The roles of metal oxides contained in Cu/ZnO-based catalysts were classified into two categories: (1) Al2O3 or ZrO2 improves the dispersion of copper particles in the catalyst; (2) Ga2O3 or Cr2O3 increases the activity per unit copper surface area of the catalyst. The long-term stability of Cu/ZnO-based catalysts during methanol synthesis from CO2 and hydrogen was improved by adding a small amount of silica to the catalysts. Silica added to the catalysts suppressed the crystallization of ZnO contained in the catalysts. The catalysts were found to be highly active and extremely stable in methanol synthesis from CO2 and hydrogen. In the next step, a bench plant with a capacity of 50 kg day−1 of CH3OH, which was equipped with facilities for recycling unreacted gases and gaseous products, was successfully operated. The purity of crude methanol produced was 99.9 wt%, whereas the purity of crude methanol produced from syngas in a present-day commercial plant was reported as 99.6 wt%.

Polycrystalline films of Sn 2 S 3 compound were prepared on glass substrates by the spray pyrolysis technique at a substrate temperature of 270 ∘ C using tin chloride (SnCl 2 ) and thiourea (Cs(NH 2 ) 2 ) solutions with a concentration of 0.1 M. The X-ray diffraction pattern reveals an orthorhombic structure and an average grain size equal to 130 A. The optical properties of the films were studied using optical transmittance and reflectance measurements over the wavelength range 200–2500 nm. The variation of refractive index n and extinction coefficient k with photon energy are reported. The dispersion of the refractive index in Sn 2 S 3 is analysed using the concept of a single oscillator. The values of oscillator energy E 0 and dispersion energy E d are determined to be 3.98 eV and 13.5 eV, respectively. The optical constants confirm that the Sn 2 S 3 thin films have a direct band gap of 2 eV. A value of 4.35×10 −3 (Ω cm) −1 for the room temperature conductivity is found using the four-probe method.

We propose the use of a pattern search optimization technique in combination with a seed preprocessing procedure to determine the optical constants and thickness of thin films using only the transmittance spectra. The approach is quite flexible, straightforward to implement, and efficient in reaching the best fitting. We demonstrate the effectiveness of the method in extracting optical constants, even when the films are not displaying interference fringes. Comparison to a real-coded genetic algorithm shows that the modified pattern search is fast, almost accurate, and does not need any parameter adjustments. The approach is successfully applied to extract the thickness and optical constants of spray pyrolyzed nanocrystalline CdO thin films.