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

Abstract

Delayed luminescence spectra of pyrene-d 10 doped single crystal of fluorene have been observed. At 245 K the delayed fluorescence intensity shows a secondorder dependence on the guest phosphorescence intensity, indicating the bi-molecular origin of delayed fluorescence from the pyrene-dl0 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.