Effects of the vibronic interactions in the K2ZnI4: In and Rb2ZnI4: In crystals

The results of the photoluminescence spectra, excitation photoluminescence spectra and absolute quantum efficiency of the photoluminescence ηq for the A2ZnI4 (A=K,Rb) crystals activated with In+ impurity in the temperature range of 77–300 K are presented. At 77 K photoluminescence spectrum consists of two bands peaked at 2.43 eV (AT) and 2.13 eV (AX) for the K2ZnI4: In crystal and 2.36 eV (AT) and 2.15 eV (AX) for the Rb2ZnI4: In crystal. A fine structure was revealed in the excitation spectra of the AT- and AX-photoluminescence bands. This allows to suggest that A-absorption band of the In+ impurity is splitted into two component, and a C-band into three components. Intensity distributions in a separate components in the excitation spectra for the AT- and AX-photoluminescence bands are different. The value of the absolute quantum efficiency of the photoluminescence at 77 K is equal to ηq=0.73 for the K2ZnI4: In crystal and ηq=0.62 for the Rb2ZnI4: In crystal. Temperature quenching of the In+-centres in the A2ZnI4: In crystals begins at lower temperatures than in alkali halides.