Abstract
Abstract The exciton transport in the presence of both orientational and substitutional disorders is investigated at 77 K. The systems of study include different compositions of 1,4-dibromonaphthalene (DBN) and 1-bromo-4-chloronaphthalene (BCN). In DBN, crystal phosphorescence emission is in conformity with quasi-one-dimensional exciton motion. Fluorescence emission from an impurity and phosphorescence emissions from the triplet state of DBN and from an impurity site present in the DBN crystal have been observed. However the fluorescence emission from the first excited singlet state of DBN is absent. In BCN-doped DBN crystal, the emission corresponding to first triplet of DBN disappears. With the increase of BCN concentration, fluorescence intensity of impurity S1IMP decreases, while the impurity phosphorescence emission intensity increases. The role of the deep trap present in DBN and the effect of orientational disorder due to BCN on the energy transfer processes have been discussed. The experimental results are explained quite satisfactorily in terms of the percolation model, which suggests a two-dimensional exciton transport topology in the mixed crystal.
Published Version
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