Effects of impurity traps on exciton-guest, triplet-triplet annihilation in pyrene-d10 doped single crystal of fluorene

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Abstract
Delayed luminescence spectra of pyrene-d10 doped single crystal of fluorene have been observed. At 245 K the delayed fluorescence intensity shows a second-order dependence on the guest phosphorescence intensity, indicating the bi-molecular origin of delayed fluorescence from the pyrene-d10 molecule. Impurity thermal energy levels are obtained from various Arrhenius plots and the fluorene exciton band is located in the energy level diagram. The decay behaviour of delayed fluorescence is given and the delayed fluorescence life times are obtained for various temperatures. We believe that unknown impurities cause the delayed fluorescence in our crystal system. The kinetics for such guest-trap, triplet-triplet annihilation are discussed.