Photoluminescence and electroluminescence of a series of terbium complexes

Photoluminescence and electroluminescence of a series of terbium complexes based on 1-phenyl-3-methyl-4-R-5-pyrazolone were analyzed. The first absorption band of the pyrazolone derivative ligands gradually shifts toward the shorter wavelength region as the R changes from an electron acceptor to an electron donor. Correspondingly, the photoluminescence quantum efficiency of the terbium complexes increases. The neutral ligands also affect the photoluminescence and electroluminescence of the terbium complexes. A photochemical explanation for the influence of the R group and neutral ligand on the photoluminescence was proposed in relation to ligand-to-metal energy transfer. The electroluminescence of the terbium complexes having a neutral ligand comes from both the light emitting layer and the hole transport layer while the electroluminescence of the terbium complex without a neutral ligand is pure green coming solely from the light-emitting layer. It therefore demonstrates that the former have higher electron transport ability than the latter.