Photogeneration Mechanism and Exciton Binding Energy in Phenylenevinylene Polymers

We report measurements in a substituted phenylenevinylene polymer where we correlate the reduction of exciton population with the reduction of photoconductivity. These illustrate that the photogenerated carriers derive primarily from exciton dissociation in what is probably an intrinsic process. Excitons which survive several picoseconds do not eventually dissociate and contribute to photoconductivity, presumably reflecting a binding strength large compared to thermal energies.