Decay behavior of electroluminescence of europium complex molecules dispersed in a poly(N-vinycarbazole)

The process of electroluminescence (EL) decay of devices made by a trivalent europium (Eu) complex, Eu(DBM)3(phen)(DBM=dibenzoylmethane, phen=phenanthroline), dispersed in poly(N-vinycarbazole) (PVK), has been studied. The decay process exhibits the characteristics of the time constant being independent of the intensity of pulsed drive voltage and the EL intensity having nearly single exponential dependence on the decay time. The decay process is considered as the monomolecular recombination process. By analyzing the process, we believe that the charged carrier concentrations (involving both holes and electrons) at initial state (the decay time t=o) do not influence the time constant, indicating that injected holes and electrons within PVK film are of unbalance seriously. From this point of view, we discussed an efficient device based on Eu(DBM)3 (phen) dispersed in polymer structure.

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