"Studies On The Energy Transfer Of Phosphorescent Dye Doped Polymer"

In recent years there has been much interest in polymer-based light-emitting diode (PLED), and intensive research has been devoting to their development due to their promising applications in display technology. Although great progress has made, there are still many arguments to the mechanisms concernedPoly methyl methacrylate(PMMA), an inertia host material, was doped with 4-(dicyanomethylene)-2-t-buty-6-(1,1,7,7-tetramethyljulolidy-9-enyl)-4H-pyran(DCJTB), the electroluminescence-(EL) and phtotlu-minsecence(PL) were analysed. The distinct EL was observed but not the PL since no spectral overlap between the host and guest, which indicted that hole and electron direct recombine on the guest molecular by charge trapping. For comparison, similar device with (N-vinylcarbazole)(PVK) as a matrix material was studied, higher luminescence was observed from the PVK—based device due to the favorable hole transporting ability of PVK, but the luminescence increases slowly with applied voltage than the PMMA-based one, indicating that carrier trapping contributes more to its luminescence at a higher voltage, which agrees well with the carrier trapping mechanism.According to the changes in the electroluminescence (EL) spectrum and the relative intensity of photoluminescence(PL) spectrum of PVK doped by Ir(ppy)3 and DCJTB, we also find that the relative intensity of the emission from dye rises with increasing biases. At low bias, the relative intensity of emission from PVK host is much higher than that in PL. Basing on the experimental results, the interaction between host-exciton and charged-trap is found. The interaction blocks the energy transfer from host to dye guest.The electrophosphorescent organic light emitting diode with the structure of ITO/ PVK:Ir(ppy)3 (1:0.1%wt)/Al doped by magnetic nanopartical of iron were fabricated. Their electroluminescence properties were measured under an externalmagnetic field of 20 mT. Compared to the case of without magnetic field, the emission of Ir(ppy)3 increased. The results of experiment attributed to the Zeeman split of triplet state and hyperfine interactions of electrons and holes, which improving the energy transfer of singlet-triplet.