Design and synthesis of new multifunctional europium molecular complex for oleds

Abstract

Lanthanide based OLEDs are gained much importance due to their line like emission characteristics (f-f electronic transition) as well as phosphorescent visible range emission (IQE up to 100%). Most of the hole transporting materials reported are derived from aromatic amines, where the inclusion of arylamine units into the antenna should improve the hole injection/transporting properties of the EuIII-phosphors. The present research work aim is to increase the internal quantum efficiency by using chromophore (fluorene) molecule in order to improve the ð-ð* transition in the antenna and facilitate the energy transfer to europium ion, to link multi-functional ligands (TPA-DPA/ Fluorene and phenanthroline) that should be active as well as capable of charge transport. To fulfil this, a new efficient red emitting europium(III) molecular complex having neutral ligand [Eu(TTA)3 (Phen-Fl-TPA-DPA) - Eu(TTA)3 = Tris (thenoyltrifluoroacetone) Europium (III), Phen-Fl-TPA-DPA = N1-(4-(diphenylamino)phenyl)-N1-(4-(1-(9,9-diethyl-9H-fluoren-2-yl)-1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)phenyl)-N4,N4-diphenylbenzene-1,4-diamine) has been designed. The same has been successfully synthesised and optically characterised. The photophysical studies of the synthesized Ligand (Phen-FL-TPA-DPA) and Eu-complex have been carried out in the solution form by UV-Vis spectroscopy and spectrofluorimetry. The photoluminescence emission spectra of Eu(TTA)3Phen-FL-TPA-DPA exhibits 5D0-7FJ (J=0-4) transitions of Eu(III) ion. The characteristic emission observed at 612 nm due to 5D0-7F2 electric-dipole transition (non-centrosymmetric site). The thermogravimetric analysis (TGA) shows that the compound is thermally stable (278oC (10%)) and it is good enough to fabricate the OLED device using the synthesised Eu(III)-complex.