Ein Modell zur verzögerten Fluoreszenz von Anthracen/Tetracen Kristallen

Abstract

Abstract Spectra and decay-times of delayed fluorescence in anthracene single crystals doped with tetracene at concentrations ranging between 3·10-10 to 3·10-5 were measured (T = 300°K). The dependence of the relative intensities and the decay-times on the concentration is explained by a simple model: The triplet-excitons of the host-lattice are captured by triplet traps localized in the nearest neighbourhood of the guest molecules. Than, the energy either goes to the tetracene, or thermally stimulated back into the triplet exciton band. The energy transfer of singlet excitons is taken into the considerations. The differential-equations describing the model are approximative^ solved. The solutions are compared with the experimental results. From the measurements a transfer rate K= (1.1 ± 0.4) · 104 for singlet excitons is derived, corresponding to a velocity constant of ks = 5.5 · 1011 s-1 (at p = 0.7 ± 0.07). The transfer of triplet excitons is governt by the constant k = 2 · 1011 s-1 . This corresponds a diffusion constant of triplet excitons D= (1.25 ± 0.2) · 104 cm2 s-1 . The lifetime of the tetracene triplet state within the antracene lattice is found to be τ = ( 1.09 ± 0.1) · 10-3 s.