Charge carrier generation through reexcitations of an exciton in poly(p-phenylene vinylene) molecules

Charge carrier generation due to reexcitations of an exciton in poly(p-phenylene vinylene) (PPV) molecules is studied theoretically in the framework of the tight-binding approach. Two different kinds of optical transitions for an exciton are suggested. It is found that the high-energy transition will dissociate the exciton into free charges, which is responsible for the photocurrent. The state from the low-energy transition is strongly field dependent. Only at a strong electric field does the exciton dissociate into free charges. The different quantum efficiency of charge carrier photogeneration in a solid-state PPV from that in a solution one is studied by including the effect of interchain couplings on the exciton dissociation.