Optical studies of chemical doping achieved by ion implantation in poly(p-phenylene vinylene)

Measurements of the optical properties of thin films of poly(p-phenylene vinylene) (PPV) implanted with caesium, xenon and iodine at a low energy (30 keV) are reported. Optical absorption shows evidence for graphitization at high fluences, independent of the ion type. In contrast, for samples implanted with caesium and with iodine, the optical absorption due to charge accumulation in the PPV layer, formed within a field-effect device, shows infrared absorption characteristics of a chemically doped polymer which are associated with charged bipolarons. Photoluminescence is quenched as a result of ion implantation. We model this in terms of exciton migration over a characteristic distance of 10-15 nm to quenching centres introduced by the implantation.