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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.

To find a seemly solution to the problems of efficiency dependency of the hybrid PV/TE devices, on important factors like “high-absorbance with high-ZT materials” and improving the performance of existing devices, are essential research topics nowadays. In this regard, we report here optical coating, and thermoelectric features of the kesterite-structured Ag2CdSnS4 and Ag2CdSnSe4 compounds. These investigations are performed at the level of “full-potential linearized augmented plane wave plus local orbital method, FP-L(APW + lo)” framed within the “density functional theory (DFT)” method comprised with relativistic effects. Our study of the optical coating shows that both the investigated materials have a good level of absorbance (A), approximately 80% in the visible part of the spectra. Further, we found that the magnitude of reflectance (R) of the Ag2CdSnX4 (X = S, Se) thin films increase with increasing film thickness, while the response of the transmittance (T) spectra is reverse to it. These results are corroborated by the study of the transport properties by employing the Boltztrap code, and correspondingly electrical conductivity, Seebeck coefficient, electronic thermal conductivity as well as the figure of merit parameters were evaluated and analyzed as a function of the chemical potential for both investigated compounds at five values of the temperatures. Hence our obtained results show that both the investigated semiconductor materials exhibit strong potential for the application of hybrid PV/TE systems.

First principles calculations were carried out on the SrMoO4 compound which has been of interest owing to its technologically important physical properties. The structural, electronic, optical and thermal properties of this compound have been investigated under low pressure (LP) through the full potential linearized augmented plane wave method (FP-LAPW) within the framework of density functional theory. It is found that the phase transition from zircon to scheelite type structure occurs at negative pressure. The calculated ground state properties in scheelite structure are found to be in good accord with previously published data. Using the recently developed Tran Blaha-modified Becke Johnson approach, we have also studied the electronic band structure of this compound which shows the semiconducting behavior with a direct band gap of 4.30 eV in the scheelite phase, whereas the band gap is found to be 2.18 eV in the zircon phase. Various thermodynamic properties including the thermal volume expansion coefficient and heat capacities at constant volumes and pressures were calculated via the quasi-harmonic Debye model at different temperatures (0–1000 K). Furthermore, optical properties such as complex dielectric function, refractive index, and reflectivity spectra of the titled compound were studied for incident electromagnetic waves in an energy range up to 16 eV. The contributions to various transitions peaks in the optical spectra are analyzed and discussed with the help from the energy dependent imaginary part of the dielectric function.

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.

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.

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 investigated the pressure dependence of the excitation energies of the ternary CdXP2 (with X=Si, Ge and Sn) pnictide semiconductors in the chalcopyrite structure. Using a new full potential augmented plane wave plus local orbitals method, we have studied the effect of high pressure on the band structure and on the optical properties. We show that the pseudodirect band gap of CdSiP2 narrows with increasing pressure and the direct band gap of CdGeP2 changes to a pseudo-direct band gap. Furthermore, we find that the magnitude of the pressure coefficients for this series of materials changes from the pseudodirect to a direct band gap.

We have studied structural, electronic and optical properties of some A II B IV C 2 V ternary semiconductors, precisely CdSiP 2 and CdGeP 2 with chalcopyrite structure which are investigated using the full potential linearized augmented plane wave (FPLAPW) method. For treating the correlation term, we have choosen the local density approximation (LDA). The total-energy approach is used to determine the c / a ratio and the equilibrium volume. On the one hand, we have analyzed electronic properties such as band structures, electronic charge densities and density of states. On the other hand, optical properties are also derived.

The electronic structure, mechanical and thermodynamic properties of Fe2VX, (with X = Al and Ga), have been studied self consistently by employing state-of-the-art full-potential linearized approach of augmented plane wave plus local orbitals (FP-LAPW + lo) method. The exchange-correlation potential is treated with the local density and generalized gradient approximations (LDA and GGA). Our predicted ground state properties such as lattice constants, bulk modulus and elastic constants appear more accurate when we employed the GGA rather than the LDA, and these results are in very good agreement with the available experimental and theoretical data. Further, thermodynamic properties of Fe2VAl and Fe2VGa are predicted with pressure and temperature in the ranges of 0–40 GPa and 0–1500 K using the quasi-harmonic Debye model. We have obtained successfully the variations of the heat capacities, primitive cell volume and volume expansion coefficient.

New structured mesoporous catalysts TiSBA15 and Ti-A1SBA15 were synthesised by grafting titanium on the pore internal surface of various SBA15 and A1-SBA15 materials by means of titanium tetrachloride in the gas phase. These catalysts were tested in the oxidation of alkenes by alkyl hydroperoxides in mild conditions (343-353 K). The silica based materials lead, in any case, to the selective formation of the epoxides with a high level of conversion over four catalytic runs. Al-based supports afford an efficient acid-catalysed ring opening of oxiranes and allow the direct conversion of cyclohexene to adipic acid with a yield of 80%.

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.