First-principles study of XSrBr3 (X = Li, K, Ag) halide perovskites for solar-blind photodetector applications

Abstract

We conducted DFT calculations using FP-LAPW method to explore the electrical, optical, and elastic properties of XSrBr₃ (X = Li, K, Ag) perovskites. For structural optimization, Birch-Murnaghan equation of state is used, which confirmed that these compounds crystallize in a cubic structure. Structural stability was validated through tolerance and octahedral factors, as well as formation energies, while phonon dispersion and Gibbs free energy confirmed their dynamic stability. TB-mBJ-GGA approximation are used to precisely determine the band structures of these compounds and it reveals that all three i.e., (LiSrBr₃, 6.31 eV), (KSrBr₃, 6.59 eV), and (AgSrBr₃, 4.17 eV) are indirect band gaps at the M-Γ high-symmetry points, respectively. IRelast package in WIEN2K are used to assess the elastic responses and it was found all three compounds demonstrated mechanical stability and elastic anisotropy. However, LiSrBr₃ and KSrBr₃ exhibited brittle behavior, while AgSrBr₃ is ductile. In the optical domain, we examined the absorption coefficient, refractive index (n(ω)), reflectivity, and optical conductivity across an energy range of 0 to 12 eV, shedding light on how these materials interacted with different photon energies. Based on the findings, the halide perovskites XSrBr₃ (X = Li, K, Ag) exhibited excellent optical properties, making them strong candidates for solar-blind applications such as UV photodetectors, deep UV-LEDs, and high-frequency systems.