The effect of ligand conjugation length on europium complex performances in light-emitting diodes

Novel europium complexes containing either symmetrical or unsymmetrical diphenanthryl beta -diketone ligands were synthesized and characterized. The ligand conjugation length has a profound effect on the spectral properties of the complexes and the device performance of the complexes as emitting dopants in light-emitting diodes. The unsymmetrical ligand has a longer conjugation, which red-shifts the absorption of the complex. The longer wavelength absorption facilitates the choice of host material that can efficiently transfer energy to the complex. However, the longer conjugation also results in a less efficient energy transfer from the ligand to the central Eu3+ ion. (C) 2001 Elsevier Science B.V. All rights reserved.