Study of optoelectronic and thermoelectric properties of K2XSbCl6 (X= In, Au) double perovskites for energy conversion devices: A DFT insight

Density functional theory (DFT) method based on first principles calculations are performed to explore the novel halide perovskites K2InSbCl6 and K2AuSbCl6. This study explores them for the first time to investigate their structural, electronic, optical, and thermoelectric properties. After relax the structure, we computed some parameters such as lattice constant (21.2195, 20.256) bohr, ground states energy (-32681.329187 eV, -59010.453287 eV), and formation energy (-2.06 eV, -1.433 eV) observed for K2XSbCl6 (X = In, Au) compounds respectively. The K2InSbCl6 reveals a direct band gap (1.03 eV), while K2AuSbCl6 shows an indirect band gap (1.01 eV). Hence, both materials express semiconducting behavior. Furthermore, the calculated optical characteristic is favorable for optoelectronics devices. The real dielectric function epsilon 1(omega) for K2XSbCl6 (X = In, Au) 4.0 and 4.25 and the absorption coefficient shows maximum absorption in the visible region. The thermometric response of both compounds is calculated with Boltzmann's theory. To check the material efficiency, considered the thermal parameters, electrical conductivity, thermal conductivity, Seebeck coefficient, and power factor. The zT values of K2InSbCl6 is 0.74 and 0.77 for K2AuSbCl6. The present study of these novel compounds provides an overview of the physical properties of optoelectronics and thermoelectric applications.