Low operational voltage of organic electroluminescent devices with a high bipolar conducting silole derivative

We have measured electron and hole mobilities in vacuum-deposited film of 2,5-bi (6'-(2',2"-bipyridyl))-1,1-dimethyl-3,4diphenylsilole (PyPySPyPy) using a time-of-flight technique. The PyPySPyPy has a bipolar transport property and both its electron and hole mobilities are over 10(-4) cm(2)/Vs. Multilayered organic electroluminescent (EL) devices consisting of N, N'diphenyl-N, N'-(3-methylphenyl)-[1,1'-biphenyl]-4,4'-diamine (TPD) as a hole transport layer, tris (8-quinolinolato) aluminum (III) (Alq(3)), as an emitting layer, and PyPySPyPy as an electron transport layer exhibit a very low operational voltage of 3.6 V for obtaining 1,000 cd/m(2). The Schottky barrier height at the PyPySPyPy/Al interface was 0.59eV, and the value was obviously smaller than that in the case of the Alq(3)/Al interface.