Singlet exciton migration and energy transfer in pyrene doped naphthalene

Time resolved spectroscopy measurements of the fluorescence intensities of pyrene doped naphthalene crystals were used to investigate host sensitized energy transfer in this system. A time dependent energy transfer rate is observed and these results are interpreted in terms of a generalized random walk formulation for the migration of singlet excitons. This leads to a value of about ${\text{1.5× 10}}^{\text{−10}}\sec$ for the exciton hopping time at room temperature. The results also imply the existence of extended trapping regions surrounding each activator and indicate the importance of including greater than nearest neighbor steps in the random walk. These results are compared to similar ones obtained on anthracene and tetracene doped naphthalene crystals. The temperature dependence of the energy transfer rate in pyrene doped naphthalene is consistent with thermal defect scattering and trapping effects similar to those seen in other doped naphthalene crystals.