Carrier transport in thin films of organic electroluminescent materials

Using the time of flight technique, the carrier mobilities of organic electroluminescent materials, N,N'-bis-(1-naphhyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (NPB), tris(8-hydroxyquinoline) aluminum (Alq), and Tb(AcA)(3)phen (AcA: acetylacetone, phen: phenanthroline) (Tb-complex), were measured. At room temperature and an electric field of 2.3 X 10(5) V/cm, the effective mobility of holes in NPB, electrons in Alq and Tb-complex were (8.8 +/- 2) X 10(-4), (6.7 +/- 2) X 10(-5) and (3 +/- 2)X 10-4 cm(2) V-1 S-1, respectively. The hole mobility of NPB shows an exponential root field dependence as commonly seen in some organic materials. (C) 1999 Elsevier Science B.V. All rights reserved.