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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; (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.

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.

(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.