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

In the present study, we propose a novel type of lead-free double halide perovskite Cs2AgAsCl6 material exhibiting exceptional photovoltaic and photocatalytic properties. Density functional theory (DFT) is employed to investigate the photovoltaic and photocatalytic properties based on several significant properties of the Cs2AgAsCl6 material. The thermodynamic stability of Cs2AgAsCl6 has been confirmed by the enthalpy formation, which is -32.36 eV f.u.-1 Dispersion of phonons near the gamma point confirmed the existence of dynamical stability. The constant value of the heat capacity is 59.45 cal per cell K, which is calculated by the Dulong-Petit limit. The GGA-PBE and HSE-06 functional approaches determined indirect bandgaps of 1.31 and 2.49 eV, respectively, for a semiconductor whose electronic properties revealed photocatalytic efficiency. The effective masses of an electron and a hole are 0.46 me and 0.61 me, respectively, which may enhance the photocatalytic dye degradation owing to their low carrier effective mass. Notably, better photocatalytic properties, i.e., dye degradation, are confirmed by the redox potential. The estimated edge potentials of the conduction band (CB) and valence band (VB) are -0.048 and 2.448 eV, respectively, which are greater than the H+/H2 and O2/H2O potentials. The Cs2AgAsCl6 material reveals an outstanding optical property that is suitable for photovoltaic applications. Therefore, Cs2AgAsCl6 can act as a potential candidate in the field of photovoltaic and photocatalytic applications.

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

The antiperovskites based on metal halides have emerged as potential materials for advanced photovoltaic and electronic device applications. But the wide bandgap of non-toxic CsSnCl3 reduces its photovoltaic efficiency. Here, we report the change of electronic structure of CsSnCl3 at different pressure by using GGA-rPBE and GGA-PBEsol functionals and the GW method. We have shown that the prediction of electronic structure transition (semiconducting to metallic state) strongly depends on the exchange-correlation and the GW method gives the most reasonable values of the bandgap under pressure. The pressure increases the electronic density of states close to the Fermi level by pushing the valence electrons upward and thus, reduces the bandgap linearly. Afterward, we have also investigated the influence of pressure on absorption coefficient, and mechanical properties meticulously. Although the pressure shifts the absorption peak to lower photon energies, the absorption coefficient is slightly improved.