A first-principles study of mechanical, thermodynamics, optical, and thermoelectric characteristics of hexagonal CsGeX3 (<mml:mstyle>X</mml:mstyle>=<mml:mstyle>Cl</mml:mstyle>, Br, I) Perovskites

In this research, we have employed the Density Functional Theory (DFT) to successfully study the structural, elastic, thermoelectric, and optoelectronic properties of hexagonal halide perovskites CsGeX3 (X = I, Cl, and Br). We used the Modified Becke-Johnson (MBJ-GGA) potential approximation to profoundly describe the band structure. The compounds of this interesting study are ductile, anisotropic, and mechanically stable. Our study showed that the optical properties are significant, among which are the following: the absorption is higher in the ultraviolet range, and the transmittance reaches a maximum level, which is 80% in the visible and infrared ranges. These substances can be employed in various optoelectronic systems that work in visible and ultraviolet energies. Furthermore, the transport properties are remarkably improved and reached the ZT similar to 1. These characteristics proved that they have an interesting potential for thermoelectric uses. We emphasized that this study provided the theoretical foundation of these structures' elastic, electronic, and optical properties.