TIME RESOLVED ENERGY MIGRATION IN AN ENERGETICALLY DISORDERED MOLECULAR-CRYSTAL

Time resolved emission spectroscopy is used to monitor triplet exciton migration in p-dichlorobenzene-p-dibromobenzene mixed crystals. The migration efficiency is varied by adjusting the concentration and the temperature (2-12 degree K). Long range migration is found even though the static energy disorder parameter W is much larger than the exciton band width B. Because of exciton tunneling, the range of the transfer is only limited by the maximum lifetime of an exciton. These results illustrate the importance of at least six key parameters in determining the efficiency of long range exciton migration; B, W, the range of transfer, the temperature, the exciton lifetime and the topology of the excitation exchange interactions through its effect on the long range connectedness of the system.