Molecular electrophosphorescence in (Sm, Gd)-β-diketonate complex blend for OLED applications

In this work the preparation and characterization of the triple-layer organic light-emitting diode (OLED) using a mixture of the samarium and gadolinium beta-diketonate complexes [Sm0.5Gd0.5(TTA)(3)(TPPO)(2)] as emitting layer is reported. The OLED's devices contain 1-(3-methylphenyl)-1,2,3,4-tetrahydroquinoline-6-carboxyaldehyde-1,1'-diphenylhydrazone (MTCD) as hole-transporting layer and tris(8-hydroxyquinoline aluminum) (Alq(3)) as electron transporting layer. The electroluminescence spectrum present emission narrow bands from the (4)G(5/2)-> H-6(J) transitions (where J=5/2, 7/2 and 9/2) characteristic of the Sm3+ ion. These sharp lines are overlapped with a broad band attributed to the electrophosphorescence from the T-1 -> S-0 transition in the ligand TTA. The intramolecular energy transfer is discussed and applied on the change of the emission color of the organic LEDs at different bias voltages. (c) 2012 Elsevier B.V. All rights reserved.