Strain effects on electronic, optical properties and carriers mobility of Cs2SnI6 double perovskite: A promising photovoltaic material

Owing to the fascinating optoelectronic and photovoltaic properties, perovskite halide materials have attracted much attention for solar cells applications. Using the first-principles approaches, we present here results of calculations of the strain effects on electronic and optical properties as well as carriers mobility of CsSnI double perovskite. The calculated band gap energy of unstrained CsSnI is about 1.257 eV when using Tran-Blaha modified Becke Johnson (mBJ) exchange potential that is in fair agreement with experimental measurements. Under the applied strains, this band gap value increases up to 1.316 eV for -4% compressive strain and decreases till 1.211 eV for 4% tensile strain. This effect is mainly due to the fact that the conduction band minimum shifts under compressive and tensile strains. From carrier mobility calculations, we notice that under tensile strain both hole and electron carrier mobilitiy diminishes, whereas the carrier mobility increases by 25.7 % for electron and by 15 % for holes under -4% compressive strain. Moreover, the optical analysis reveals that applied strain can affect the optical properties of CsSnI perovskite.

First-Principle Investigations on the Electronic and Transport Properties of PbBi2Te2X2 (X=S/Se/Te) Monolayers

This paper reports first-principles calculations on PbBi2Te2S2, PbBi2Te2Se2 and PbBi2Te4 monolayers. The strain effects on their electronic and thermoelectric properties as well as on their stability have been investigated. Without strain, the PbBi2Te4 monolayer exhibits highest Seebeck coefficient with a maximum value of 671 μV/K. Under tensile strain the highest power factor are 12.38×1011 Wm−1K−2s−1, 10.74×1011 Wm−1K−2s−1 and 6.51×1011 Wm−1K−2s−1 for PbBi2Te2S2, PbBi2Te2Se2 and PbBi2Te4 at 3%, 2% and 1% tensile strains, respectively. These values are 85.9%, 55.0% and 3.3% larger than those of the unstrained structures.

Ab-Initio Investigation of Strain Effects on the Physical Properties of PdVTe Alloy

The investigations of the strain effects on magnetism, elasticity, electronic, optical and thermodynamic properties of PdVTe half-Heusler alloy are carried out using the most accurate methods to electronic band structure, i.e. the full-potential linearized augmented plane wave plus a local orbital (FP-LAPW + lo) approach. The analysis of the band structures and the density of states reveals the Half-metallic behavior with a small indirect band gap Eg of 0.51 eV around the Fermi level for the minority spin channels. The study of magnetic properties led to the predicted value of total magnetic moment µtot = 3µB, which nicely follows the Slater–Pauling rule µtot = Zt -18. Several optical properties are calculated for the first time and the predicted values are in line with the Penn model. It is shown from the imaginary part of the complex dielectric function that the investigated alloy is optically metallic. The variations of thermodynamic parameters calculated using the quasi-harmonic Debye model, accord well with the results predicted by the Debye theory. Moreover, the dynamical stability of the investigated alloy is computed by means of the phonon dispersion curves, the density of states, and the formation energies. Finally, the analysis of the strain effects reveals that PdVTe alloy preserves its ferromagnetic half metallic behavior, it remains mechanically stable, the ionic nature dominates the atomic bonding, and the thermodynamic and the optical properties keep the same features in a large interval of pressure.