Kinetics of triplet–triplet annihilation in disordered organic solids on short time scale Original Research Article

In the present paper, the results of the investigation of the decay kinetics of delayed luminescence of disordered chrysene on short times are presented. A strong deviation of the decay of both phosphorescence and annihilation delayed fluorescence from the exponential law is observed. This effect is shown to be due to the relaxation process of electronic excitation energy in the system with large energetic disorder. At the same time, the reaction of triplet–triplet annihilation is well described by the second-order classical equation with a time-independent rate coefficient. This permits concluding that delayed fluorescence results from the annihilation of triplet excitations cascading down in the system of energetically disordered centres, and this process is in no way spatially limited. The mechanisms leading to the power law of annihilation delayed fluorescence decay in the region of low temperatures and their universality are also discussed.