Exciton diffusion lengths of organic semiconductor thin films measured by spectrally resolved photoluminescence quenching

We demonstrate spectrally resolved photoluminescence quenching as a means to determine the exciton diffusion length of several archetype organic semiconductors used in thin film devices. We show that aggregation and crystal orientation influence the anisotropy of the diffusion length for vacuum-deposited polycrystalline films. The measurement of the singlet diffusion lengths is found to be in agreement with diffusion by Forster transfer, whereas triplet diffusion occurs primarily via Dexter transfer.