Theoretical and experimental study on the electronic and optical properties of K 0.5 Rb 0.5 Pb 2 Br 5 : a promising laser host material

• Published in: RSC advances 2020-03, Vol.10 (19), p.11156-11164
• Main Authors: Vu, Tuan V, Lavrentyev, A A, Gabrelian, B V, Vo, Dat D, Tong, Hien D, Denysyuk, N M, Isaenko, L I, Tarasova, A Y, Khyzhun, O Y
• Format: Article
• Language: English
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/D0RA00718H

The data on the electronic structure and optical properties of bromide K Rb Pb Br achieved by first-principle calculations and verified by X-ray spectroscopy measurements are reported. The kinetic energy, the Coulomb potential induced by the exchange hole, spin-orbital effects, and Coulomb repulsion were taken into account by applying the Tran and Blaha modified Becke-Johnson function (TB-mBJ), Hubbard U parameter, and spin-orbital coupling effect (SOC) in the TB-mBJ + U + SOC technique. The band gap was for the first time defined to be 3.23 eV. The partial density of state (PDOS) curves of K Rb Pb Br agree well with XES K Ll and Br Kβ , and XPS spectra. The valence band (VB) is characterized by the Pb-5d and Pb-5d sub-states locating in the vicinities of -20 eV and -18 eV, respectively. The VB middle part is mainly formed by K-3p, Rb-4p and Br-4s states, in which the separation of Rb-4p and Rb-4p was also observed. The strong hybridization of Br-p and Pb-s/p states near -6.5 eV reveals a major covalent part in the Br-Pb bonding. With a large band gap of 3.23 eV, and the remarkably high possibility of inter-band transition in energy ranges of 4-7 eV, and 10-12 eV, the bromide K Rb Pb Br is expected to be a very promising active host material for core valence luminescence and mid-infrared rare-earth doped laser materials. The anisotropy of optical properties in K Rb Pb Br is not significant, and it occurs at the extrema in the optical spectra. The absorption coefficient ( ) is in the order of magnitude of 10 cm for an energy range of 5-25 eV.