Alkali-metal-driven optoelectronic properties of XSrBr₃ (X = Cs, Rb, K) Sr-based halide perovskites: A...

In this study, First-principles calculations were conducted to investigate the structure, electric, optical, and thermodynamic properties of Sr-minerals based halide perovskites, in order to gain insight into their potential for optoelectronic applications. The present work aims to comprehensively investigated the structural, electronic, elastic and optical properties of Sr-minerals based halide perovskites of XSrBr₃ (X = Cs, Rb, and K) through first principles density functional theory (DFT)-based calculations. The PBE-GGA, TB-mBJ and HSE06 exchange-correlation schemes were used to calculate the electronic band structures of XSrBr₃ (X = Cs, Rb, K) to obtain better reliability in the prediction of the band-gap energies. CsSrBr₃ was found to have indirect band gaps of (4.249, 6.351 and 5.333) eV with the PBE-GGA, TB-mBJ, and HSE06 methods, respectively. The values of the corresponding band gaps for RbSrBr₃ were (3.932, 6.421 and 5.023) eV, while KSrBr₃ had indirect gaps of (3.797, 6.642 and 4.860) eV, respectively. Based on the result obtained, that all the three compounds are semiconducting with high band gap. The optical properties show a high absorption in the UV region, and good refractive-index and dielectric responses, particularly for XSrBr₃ (X = Cs, Rb, K) for optoelectronic applications in the UV region. All these compounds are mechanically stable and ductile as the calculated elastic constants meet all mechanical stability requirements. They have relatively low moduli of elasticity indicating moderate rigidity, and perhaps better mechanical processability. The finding of these characteristics makes CsSrBr₃, RbSrBr₃ and KSrBr₃ interesting for application as UV photodetectors, as optoelectronic devices resistant to radiation, and as electronic devices with a wide band gap.