Temperature dependence of electronic energy transfer from a polymer host to a triplet emitter in light emitting diode materials

We investigate the temperature dependence of electronic energy transfer between a polymer host, poly(N-vinylcarbazole) blended with 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole, and the triplet emitter tris[9,9-dihexyl-2-(phenyl-4′-(pyridin-2′′-yl))fluorene] iridium(III) (Ir(DPPF)3). The photophysics of the blend are similar to those of neat poly(N-vinylcarbazole), with two emitting species corresponding to shallow and deep excimer traps. When the blend is doped with Ir(DPPF)3, the deep trap emission is preferentially quenched. This quenching cannot be explained by simple Förster energy transfer to the dopant. Instead, the data are consistent with a rapid, temperature-dependent partitioning of the energy between the two host species and the Ir(DPPF)3, each of which decays independently.