Dispersive triplet excitation transport in organic glasses

Time dependent transport of triplet excitations in amorphous benzophenone, anthraquinone, and phenanthrene has been investigated in the temperature range 4.2 K<T< 100 K by monitoring diffusion-controlled decay of the inhomogeneously broadened 0-0 phosphorescence band of bulk states. The results are in excellent agreement with both the analytic theory of Grünewald et al. and computer simulation of nonequilibrium transport. They indicate the applicability of a stochastic transport model based on asymmetric hopping rates with unrestricted energy relaxation. The time dependence of the ensemble averaged hopping frequency has been determined within three decades of time. It can be approximated by a ν(t)∼(t/t₀)^a-1 law with time dependent dispersion parameter a.