Localized and Free Biexcitons in Silver Bromide

Abstract

Abstract Recombination luminescence in AgBr at low temperature is studied for high power quasi‐cw and pulsed excitation. The samples are nominally pure but vary systematically in iodine impurity content. Using time‐resolving techniques several new luminescence transitions are detected and found to be correlated with iodine concentration. The results can be consistently explained assuming that, besides free excitons and free biexcitons, a biexciton bound to isoelectronic iodine is created and decays. The model is supported by energy positions and shape of the observed lines as well as by the dependence of luminescence intensity on excitation power and iodine concentration. To completely account for the observed spectra, the model also takes into account intervalley exciton scattering by‐ X‐phonons known to be an effective exciton relaxation process in AgBr.