Luminescence of Cs4PbBr6 aggregates in As-grown and in annealed CsBr : Pb single crystals

Luminescent aggregates of the type of Cs4PbBr6 dispersed in a CsBr crystal lattice have been observed for the first time in as-grown and in annealed ( at 160 to 260 degrees C for 20 h) CsBr:Pb single crystals with a sufficient ly large lead concentration (0.3 to 1.8 mol% in the melt). Absorption spect ra as well as spectral, polarization and kinetic characteristics of their l uminescence peaking near 3.3 eV and excited near 4.0 eV and 5.2 to 5.1 eV h ave been studied at 4.2 to 200 K. The characteristics of the Cs4PbBr6 aggre gates have been compared with those of a Cs4PbBr6 Single crystal and with t he characteristics of Pb2+ centres in a quenched CsBr:Pb crystal. The origi n and the structure of the corresponding relaxed excited states have been d iscussed.