Investigations of optoelectronic and scintillating properties of novel halide perovskites Cs2KSnX6 (X=Cl, Br, I)

In this paper, using density functional theory (DFT) formalism, optoelectronic properties of new halide perovskites Cs₂KSnX₆ (X = Cl, Br, I) are explored. The lattice constants of these double perovskites with $\text{Cl},\text{Br,}$ and $I$ were found to be $11.75\AA ,12.34\AA \text{,}$ and $13.24\AA \text{,}$ respectively. Trans-Blaha modified Becke-Johnson (TB-mBJ) exchange-correlation functional was used to calculate the energy bandgap by incorporating spin-orbital coupling effects into it. The double perovskite with $\text{Cl}$ was observed to possess a higher band gap value due to the increase in the size of halide anions. Due to the inverse relationship between bandgap values and lattice constants, it has been observed that increasing the lattice constant value results in the decrease of the electronic band gap and vice versa. From the density of states calculations, the nature of the electronic states involved in forming the energy bands has been determined. The upper light yield (LY) with the limit of 100 % under ideal conditions is found to be 544217 ph/MeV, 950118 ph/MeV, and 1600000 ph/MeV for ${\text{Cs}}_2\text{KSn}{\text{Cl}}_6,{\text{Cs}}_2\text{KSn}{\text{Br}}_6$, and ${\text{Cs}}_2\text{KSn}{I}_6$ respectively, which suggests their potential applications in scintillating devices. Moreover, the optical properties like complex dielectric functions, absorption coefficients, reflectivity, and refractive index are calculated for these new proposed compounds. A systematic analysis of the optical and scintillating properties suggests the usefulness of ${\text{Cs}}_2\text{KSn}{I}_6$ among other compounds, as a potential candidate for high-energy radiation detection and other optoelectronic applications.