Optical and spectral properties of the Tl2ZnI4 and Tl2ZnI4 : Mn crystals

The reflection, photoluminescence and photoluminescence excitation spectra of the Tl2ZnI4 and Tl2ZnI4:Mn crystals are measured in the temperature rang e of 77-300 K. A band gap (E-g = 3.935 eV for E perpendicular to C and E-g = 3.957 eV for E parallel toC) and parameters of the exciton (radius and bi nding energy) for both polarizations are defined from the reflection spectr a. Photoluminescence band at 2.66 eV is ascribed to the pi -emission band o f the self-trapped excitons. A luminescence band of Mn2+ centres in Tl2ZnI4 :Mn crystals is effectively excited both in the excitonic absorption region and impurity absorption bands in the 2.5 and 3.1 eV regions. Separate comp onents in the excitation photoluminescence spectra are assigned to the corr esponding electronic transitions in Mn2+ ion in Tl2ZnI4:Mn crystal. (C) 200 1 Elsevier Science B.V. All rights reserved.