PHOTOLUMINESCENCE AND THERMAL QUENCHING OF BOUND EXCITONS IN (BAS)(1-X)(SRTE)(X)

Photoluminescence spectra are reported for the first time for (BaS)(1- x)(SrTe)(x)(x = 0.1, 1.0, and 5.0 wt%) powders. Changes in the lumines cent spectra were attributed to bound exciton recombination at substit uted Te on S (Te-S) sites. Peaks were observed at 420 and 465 nm, and were attributed to singlet and doublet Te emission, respectively. The binding energies and thermal quenching activation energies for the sin glet and doublet excitons were found to be 630 and 860 meV, and 45 and 58 meV, respectively. The thermal quenching activation energy for sin glet excitons was attributed to the energy required to excite the boun d electron into the conduction band of the BaS host, and for doublet e xcitons was attributed to charge transfer between Te-S and/or nonradia tive quenching centers. (C) 1998 Elsevier Science B.V. All rights rese rved.