First-principles study of novel non-toxic trigonal KGeX3 (X=Br, I) perovskites: A potential for optoelectronic applications

In this study, structural, mechanical, electronic and optical properties of non-toxic inorganic trigonal-KGeX3 (X = Br, I) perovskites are investigated by first-principles method. The trigonal-KGeX3 (X = Br, I) perovskites are found to be thermodynamically and mechanically stable. Both trigonal perovskites, KGeBr3 and KGeI3 are direct band gap semiconductors with band gaps of 2.46 eV and 1.45 eV respectively. KGeBr3 is well-suited for optoelectronic devices that operate in the ultraviolet (UV) range, while KGeI3 is very promising as a solar absorber layer in perovskite solar cells. The KGeI3 is found to be ductile and provides good optical absorbance in visible region. The findings presented in this article align well with the previous literature published on similar crystal structures. This study suggests that trigonal non-toxic K-based inorganic perovskites can be very good candidates for optoelectronic applications.