Electronic structure transition of cubic CsSnCl3 under pressure: effect of rPBE and PBEsol functionals and GW method

Newly predicted halide perovskites Mg3AB3 (A = N, Bi; B = F, Br, I) for next-generation photovoltaic applications: a first-principles study

The research examines the exceptional physical characteristics of Mg3AB3 (A = N, Bi; B = F, Br, I) perovskite compounds through density functional theory to assess their feasibility for photovoltaic applications. Mechanical characterization further supports their stability where out of all the compounds, Mg3BiI3 demonstrates high ductility, while Mg3NF3 and Mg3BiBr3 possess a brittle nature. The calculated elastic constants and anisotropy factors also substantiate their mechanical stability, while there is an observed declining trend in Debye temperature with increase in atomic number. From the electronic point of view, Mg3NF3 can be considered as a wide-bandgap insulator with the bandgap of 6.789 eV, whereas Mg3BiBr3 and Mg3BiI3 can be classified as semiconductors suitable for photovoltaic applications bandgaps of 1.626 eV and 0.867 eV, respectively. The optical characteristics of such materials are excellent and pronounced by high absorption coefficients, low reflectivity, and good dielectrics, which are very important in the collection of solar energy. Among them, Mg3BiBr3 and Mg3BiI3 possess high light absorption coefficient, moderate reflectivity, and good electrical conductivity, indicating that they are quite suitable for applying the photoelectric conversion materials for solar cells. In addition, thermal analysis shows that Mg3NF3 is a good heat sink material, Mg3BiBr3 and Mg3BiI3 are favorable for thermal barrier coating materials. Due to their high absorption coefficients, low reflectance and suitable conductivity, both Mg3BiBr3 and Mg3BiI3 could be regarded as the most appropriate materials for the creation of the next generation of photovoltaic converters.

Investigating the effects of hydrostatic pressure on the physical properties of cubic Sr3BCl3 (B = As, Sb) for improved optoelectronic applications: A DFT study

This article explores changes in the structural, electronic, elastic, and optical properties of the novel cubic Sr3BCl3 (B = As, Sb) with increasing pressure. This research aims to decrease the electronic band gap of Sr3BCl3 (B = As, Sb) by applying pressure, with the objective of enhancing the optical properties and evaluating the potential of these compounds for use in optoelectronic applications. It has been revealed that both the lattice parameter and cell volume exhibit a declining pattern as pressure increases. At ambient pressure, analysis of the band structure revealed that both Sr3AsCl3 and Sr3SbCl3 are direct band gap semiconductors. With increasing pressure up to 25 GPa the electronic band gap of Sr3AsCl3 (Sr3SbCl3) reduces from 1.70 (1.72) eV to 0.35 (0.10) eV. However, applying hydrostatic pressure enables the attainment of optimal bandgaps for Sr3AsCl3 and Sr3SbCl3, offering theoretical backing for the adjustment of Sr3BCl3 (B = As, Sb) perovskite's bandgaps. The electron and hole effective masses in this perovskite exhibit a gradual decrease as pressure rises from 0 to 25 GPa, promoting the conductivity of both electrons and holes. The elastic properties are calculated using the Thermo-PW tool, revealing that they are anisotropic, ductile, mechanically stable, and resistant to plastic deformation. Importantly, these mechanical properties of both compounds are significantly enhanced under pressure. Optical properties, including the absorption and extinction coefficients, dielectric function, refractive index, reflectivity, and loss function, were calculated within the 0-20 eV range under different pressure conditions. The calculated optical properties highlight the versatility and suitability of Sr3AsCl3 and Sr3SbCl3 perovskites for pressure-tunable optoelectronic devices.

Exploring the influence of pressure-induced semiconductor-to-metal transition on the physical properties of cubic perovskites FrXCl3 (X = Ge and Sn)

Even though lead halide perovskites have outstanding physiochemical properties and improved power conversion efficiency, most of these compounds threaten their future commercialization because of their instability and highly toxic nature. Thus, it is preferable to use stable alternative elements rather than lead to make environmentally friendly perovskite material that will have comparable optical and electronic properties to those constructed from Pb-based perovskites. However, devices constructed from lead-free perovskites typically display a lower power conversion efficiency. Applying hydrostatic pressure could be deemed an effective method to alter the physical properties of these compounds. This not only improves their performance in application but also reveals significant correlations between structure and properties. This work uses DFT to investigate the structural, electronic, optical, and elastic properties of non-toxic, francium-based halide perovskites FrXCl3 (X = Ge, Sn) at different levels of hydrostatic pressures that vary from 0 to 10 GPa. The estimated structural parameter's strong correlation with the data from earlier studies ensures the accuracy of the current findings. Pressure causes the Fr-Cl and Ge (Sn)-Cl bonds to shorten and become stronger. The electronic property calculations demonstrated that both compounds are direct band-gap semiconductors. The application of pressure leads to a linear reduction in the band gap (semiconducting to metallic state) and raises the electronic density of states around the Fermi level by forcing the valence band electrons upward, indicating that the optoelectronic device's performance can be tuned and improved. The values of the dielectric constant, absorptivity and reflectivity showed an increasing tendency with pressure. As the pressure applied to the compounds increases, the absorption spectra show a redshift. These findings suggested that the FrXCl3 (X = Ge and Sn) compound becomes more appropriate for usage in optoelectronic applications under pressure. Furthermore, our examination of the mechanical properties indicates that both FrGeCl3 and FrSnCl3 exhibit mechanically stability, and ductility. Interestingly, we observe an increase in ductility as pressure levels rise.

Thermodynamic and dynamic stability in a new potential Cs2AgAsCl6 perovskite: insight from DFT study

A schematic diagram of the possible energy band level for photocatalytic activity: (a) favorable energy band level, (b) unfavorable VBM, and (c) unfavorable CBM position.