Probing the local structural order of C60 thin films by their exciton transport characteristics

We investigate effects of the local structure on the excitonic transport in C60 thin films by means of temperature-dependent photoluminescence quenching studies in a range of 5 to 300 K. Exciton motion in the X-ray amorphous layers indicates thermally activated transport initiated above 80 K accompanied by a thermalization of excitations into low lying states within the excitonic density of states. Discontinuities in the temperature-dependent photoluminescence behavior can be attributed to a continuous phase transition at 80 K and a first order phase transition at 180 K, thereby revealing structural information on the local film morphology in the C60 films.