Excimers in poly(phenylene vinylene) and its derivatives

Photoinduced absorption measurements on poly(phenylene vinylene), PPV, and its derivatives have revealed that some percentage of photons past the absorption edge create a long-lived excitation rather than the expected excitons. We review the evidence that these excitations are polaron pairs, and the properties of excimers in this situation, to show that the polaron pairs are essentially excimers. We show that the reason excimers in some derivatives of PPV are emissive while in others they are not is the different separation of the chains constituting the excimer. Reasons why the percentage of photons that give rise to excimers can vary greatly from sample to sample arc presented. igin of the different peaks in the photoinduced absorption is discussed.