A comparative study on the electroluminescence properties of some terbium beta-diketonate complexes

By comparing the phosphorescence spectra of Gd(acac)(3) (acac=acetylacetone ), Gd(TFacac)3 (TFacac=1,1,1-trifluoroacetylacetone), the effects of fluori ne replacement of hydrogen on the triplet state energy of the ligands were revealed. Fluorine can lower the triplet state energy of Hacac and make it more suitable for energy transfer towards the D-5(4) state of terbium. Orga nic electroluminescent devices (OELDs) with the corresponding trivalent ter bium complexes as emissive layers were fabricated. Triple-layer-type device s with a structure of glass substrate/ITO (indium tin oxide)/PVK [poly(N-vi nylcarbazole)]/PVK : Tb complex: PBD [2-(4-biphenyl)-5-(4-tert-butylphenyl) -1,3,4-oxadiazole]/PBD/Al exhibit bright green luminescence upon applying a dc voltage. The luminance of a device with Tb(TFacac)(3)phen (1,10-phenant hroline) and Tb( TFacac) 3 as emissive layer is higher than that of the cor responding devices with Tb(acac)(3)(phen) and Tb(acac)(3) as emissive layer s. The EL device with Tb(TFacac)(3)(phen) as emitter exhibits characteristi c emission of Tb3+ ions with a maximum luminance of 58 cd m(-2) at 25 V.