Very-low-operating-voltage organic light-emitting diodes using a p-doped amorphous hole injection layer

We demonstrate the use of a p-doped amorphous starburst amine, 4, 4', 4"-tr is(N, N-diphenyl- amino)triphenylamine (TDATA), doped with a very strong ac ceptor, tetrafluoro- tetracyano-quinodimethane by controlled coevaporation as an excellent hole injection material for organic light-emitting diodes ( OLEDs). Multilayered OLEDs consisting of double hole transport layers of p- doped TDATA and triphenyl-diamine, and an emitting layer of pure 8-tris-hyd roxyquinoline aluminum exhibit a very low operating voltage (3.4 V) for obt aining 100 cd/m(2) even for a comparatively large (110 nm) total hole trans port layer thickness. (C) 2001 American Institute of Physics.