THE BEHAVIOR OF TRAPPING AFTER DIFFUSION BY TUNNELING IN DISORDERED-SYSTEMS

Simulations of symmetric hopping by tunneling between randomly distributed centres in two dimensions, in the presence of deep traps, reveal as many as four regimes of decay of the survival probability of the carrier: (i) Pure trapping at short times. (ii) Trapping after dispersive transport at intermediate times. (iii) Trapping after crossover toward regular diffusion at longer times. (iv) Escape of carriers from isolated centres at very long times. The prominence of these regimes depends on the trap concentration and the decay length of the tunneling interaction. The results are related to experiments on the transport of triplet excitons in mixed crystals of p-dichlorobenzene in p-dibromobenzene.