Theoretical investigation of mechanical, optoelectronic and thermoelectric properties of K ₂ TlInY ₆ (Y = Cl, Br and I) perovskites: Emerging materials for green energy technologies

Currently, hybrid organic–inorganic perovskites attract considerable attention because of their excellent efficiency in energy conversion and tunable optical and electronic properties. The purpose of this research report is to theoretically determine the mechanical, optical, and electrical characteristics of the perovskites K 2 TlInY 6 (Y [Formula: see text] Cl, Br, I), which might be useful in energy scavenging applications. Using the Wein2k coding under the framework of density functional theory (DFT), the mechanical properties of the title perovskites are highly stable. The replacement of I (iodine) ions by their counterparts, such as Cl, Br (chlorine and bromine), leads to shrunk down of the lattice parameters and bond length of the In (indium)–Y (halides). From the electronic band energy properties, these perovskites exhibit indirect band gaps, with calculated energies of 3.44[Formula: see text]eV (3.70[Formula: see text]eV) for K 2 TlInCl 6 , 2.42[Formula: see text]eV (3.01[Formula: see text]eV) for K 2 TlInBr 6 , and 1.38[Formula: see text]eV (2.38[Formula: see text]eV) for K 2 TlInI 6 , as obtained using the TB-mBJ and (HSE06) approximations, respectively. The analysis of the density of energy states and optical bandgaps revealed that K 2 TlInCl 6 , K 2 TlInBr 6 , and K 2 TlInI 6 exhibit significant conductivity and strong electromagnetic energy absorption properties in the UV, visible, and infrared energy ranges, which is also supported by their low reflectivity. The combination of high electrical conductivity, moderate thermal conductivity, and higher ZT values of 0.771, 0.770, and 0.760, respectively, at 800[Formula: see text]K makes them promising candidates for thermoelectric applications.