Ultrafast electric field-assisted pump-probe spectroscopy in poly(9,9-dioctylfluorene) light-emitting diodes
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).
For the reason that the algorithm PFIM needs to scan database repeatedly, to produce a great deal of redundant candidate itemset, and to compute more time-complexity of frequent probability, an improved algorithm UPro-Eclat which is based on PFIM and Eclat is proposed. It uses a vertical mining method which is extension-based, adds probabilistic information in Tid, builds recursively the subset of search tree, and mines probabilistic frequent pattern by depth-first traversa. The algorithm UPro-Eclat can swiftly find probabilistic frequent itemset rather than compute their probability in each possible world.