Ab-initio study of Cu-based oxychalcogenides: A new class of materials for optoelectronic applications

Laser power and high-temperature dependent Raman studies of layered bismuth and copper-based oxytellurides for optoelectronic applications

Layered metal oxychalcogenide materials have gained significant attention in recent years due to their numerous applications in various emerging fields. The bismuth (Bi) based ternary and quaternary oxychalcogenide materials have become popular due to their excellent potential in optoelectronic, thermoelectric, and semiconducting applications. Adding copper (Cu) to these building matrices has enhanced their usefulness in various ways. In this work, Bi and Cu-based ternary and quaternary layered oxytellurides are synthesized using a unique, rarely used "microwave (MW) assisted method," and their temperature and laser power-dependent Raman measurements are carried out. All the samples are prepared at the same MW power and at a fixed irradiation time. Crystallographic studies show that the good crystallinity of the synthesized materials matches well with the phases reported previously. Nanosheet-like morphology was observed for all the prepared samples. The optical properties and band gap energies of these materials were obtained using the diffuse reflectance spectroscopy technique, which are in the range of 1.15-2.52 eV. The photoluminescence spectrum shows broad peaks around orange-red regions, indicating the potential applicability of these materials in various optoelectronic applications. The effect of high temperature and laser power on the Raman spectra of the oxytellurides is demonstrated, where the appearance of different vibrational modes along with a redshift in peak positions with the increase in temperature and power is observed.

Probing the physical properties for prospective high energy applications of QMnF3 (Q = Ga, In) halide perovskites compounds employing the framework of density functional theory

We use WIEN2K to conduct density functional theory computations to explore the structural, thermodynamic, optoelectronic, and mechanical properties of fluoroperovskites QMnF₃ (Q = Ga, In). The application of the Birch-Murnaghan equation to the energy versus volume, formation energy, and tolerance factor confirms the structural stability of these two QMnF₃ (Q = Ga, In) materials. The thermodynamic stability of the compounds is confirmed by the results of the phonon calculation, while the mechanical stability is confirmed from the values of the elastic constants. GaMnF₃ demonstrates a high capacity to withstand both compressive and shear stresses. A lower bulk modulus is responsible for the weaker ability of InMnF₃ to endure changes in volume. Compared to GaMnF₃, InMnF₃ possesses rigidity having greater shear modulus, indicating greater resistance to changes in shape. However, both compounds are characterized as mechanically brittle, anisotropic, and ductile. The band structure that was determined indicates that both GaMnF₃ and InMnF₃ exhibit a metallic character. The density of states analysis further supports the metallic nature of GaMnF₃ and InMnF₃. In GaMnF₃, the "Mn" and "F" atoms in the valence band significantly participate in the total density of states, whereas in InMnF₃, both "Mn" and "F" atoms also dominate the total density of states. The values of ε₁(0) computed for GaMnF₃ and InMnF₃ are positive i.e. > 0, and agree with Penn's model. We calculate the optical properties for both GaMnF₃ and InMnF₃ and the potential of these materials of interest for applications in optoelectronic gadgets including light-emitting diodes is attributed to their absorption in the ultraviolet-visible zone. We believe that this work may provide comprehensive insight, encouraging further exploration of experimental studies.

Investigation of Structural, Mechanical, Optoelectronic, and Thermoelectric Properties of BaXF3 (X = Co, Ir) Fluoro-Perovskites: Promising Materials for Optoelectronic and Thermoelectric Applications

Coded within Wien2K, we carry out DFT-based calculations for investigations of the structural, elastic, optoelectronic, and thermoelectric properties of BaXF₃ (X = Co, Ir) fluoro-perovskites. The Birch-Murnaghan fit to the energy-vs-volume data and formation energy shows that these fluoro-perovskites are structurally stable. The phonon calculation confirms the thermodynamic stability, while the relation between elastic constants such as C ₁₁ - C ₁₂ > 0, C ₁₁ > 0, C ₁₁ + 2C ₁₂ > 0, and B > 0 validates the mechanical stability of the compounds. BaIrF₃ exhibits a strong ability to endure compressive and shear stresses. BaCoF₃ shows a weaker capacity of withstanding changes in volume, attributed to a lower bulk modulus. Demonstrating a higher G-modulus of rigidity than the BaIrF₃, BaCoF₃ demonstrates stronger resistance to change the shape and both compounds are found to be anisotropic and brittle. The determined band structure profiles reveal that both BaCoF₃ and BaIrF₃ demonstrate a metallic nature. In addition, the metallic nature of BaCoF₃ and BaIrF₃ is reinforced by the density-of-states (DOS) study, where Co and F atoms contribute significantly to the total DOS in the valence band in the case of BaCoF₃, while that of BaIrF₃ is predominated by the Ba and F atoms. The computed values of ε₁(0) for BaCoF₃ and BaIrF₃ are approximately 30 and 19, respectively, which are in line with Penn's model. The researched materials are confirmed to be strong contenders for optoelectronics by the lack of absorption in the visible range. For their potential use in thermoelectric device applications, thermoelectric parameters such as temperature-dependent Seebeck coefficient, specific heat capacity, thermal conductivity, power factor, and figure of merit are also investigated, which show that these materials are thermally stable and promising for applications in thermoelectric devices.