Abstract
Here we report a detailed study of organic light-emitting diodes based on poly(9,9-dioctylfluorene) (PFO), to investigate polaron generation, due to field induced singlet dissociation, and their subsequent recombination. We find that initially free polarons coalesce into intermediate pairs of both singlets and triplets multiplicity which subsequently decay into the neutral state. There is indication that the efficiency of singlet formation (
β=0.7) is much higher than expected from simple state degeneracy arguments (
β=0.25).