Ab initio prediction of the structural, electronic and optical behavior of novel combinations of ternary perovskite oxides ATiO_3 (A = Rb, Cs, Fr) using the Hubbard'U' correction for optoelectronic devices

摘要

The structural and optoelectronic properties of ATiO_3 (A = Rb, Cs, and Fr) perovskite oxides in the cubic phase are investigated using an ab initio method based on density functional theory. The exchange correlation function is determined by the full-potential linearized augmented plane wave approach. RbTiO_3 shows an indirect band gap energy of 2.43 eV, whereas direct band gap energies of 1.90 eV and 1.66 eV are calculated for CsTiO_3 and FrTiO_3 compounds, respectively. The electronic density of states reveals that d states from A-cations (Rb, Cs, and Fr), along with Ti-d states, are located in the conduction band. The charge density demonstrates the ionic nature of the A-cations (Rb, Cs and Fr), while oxygen atoms share isolines with Ti atoms, leading to covalent bonds between them. Optical analyses show that the considered compounds have good optical conductivity and absorptivity when high-energy photons are incident on the surface of the materials, in particular showing minimal reflectivity. In view of these results, we consider that perovskites belong to a semiconductor category of materials suitable for application in photovoltaic and optoelectronic devices.