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

We demonstrate the use of a $p\mathrm{-doped}$ amorphous starburst amine, 4, $4^{\prime },$ $4^{″}\mathrm{-tris(N},$ N-diphenyl- amino)triphenylamine (TDATA), doped with a very strong acceptor, 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 $p\mathrm{-doped}$ TDATA and triphenyl-diamine, and an emitting layer of pure 8-tris-hydroxyquinoline aluminum exhibit a very low operating voltage (3.4 V) for obtaining $\text{100\hspace{0.5em}}{\mathrm{cd/m}}^2$ even for a comparatively large (110 nm) total hole transport layer thickness.