DFT aided prediction of phase stability, optoelectronic and thermoelectric properties of A2AuScX6 (A= Cs, Rb; X= Cl, Br, I) double perovskites for energy harvesting technology

In this work, the density functional theory (DFT) was used to predict the physical properties of A2AuScX6 (A = Cs, Rb; X = Cl, Br, I) double perovskites (DPs). The stability was confirmed by computing the formation energy, binding energy, phonon dispersion curve, stiffness constants, tolerance, and octahedral factors. The nature of electronic conductivity and chemical bonding were explored. The band gap values using TB-mBJ are 1.88, 1.68, and 1.30 eV for Cs2AuScX6 [X = Cl, Br, I] and 1.93, 1.71, and 1.32 eV for Rb2AuScX6 [X = Cl, Br, I], respectively. The dielectric function, absorption coefficient, refractive index, energy loss function, photoconductivity, and reflectivity were also calculated and analyzed. The absorption coefficients in the visible range are 0.333 x 106 cm- 1, 0.27 x 106 cm- 1, and 0.213 x 106 cm- 1 for Cs2AuScX6 [X = Cl, Br, I] and 0.345 x 106 cm- 1, 0.281 x 106 cm- 1, and 0.218 x 106 cm- 1 for Rb2AuScX6 [X = Cl, Br, I], respectively. We also investigated the thermoelectric properties and found the figure of merit (ZT) values of 0.44, 0.47, and 0.62 for Cs2AuScX6 (X = Cl, Br, I) and 0.47, 0.53, and 0.54 for Rb2AuScX6 (X = Cl, Br, I) at 300 K. The results revealed that the studied compounds are potential candidates for solar cells and thermoelectric devices.