Efficient top-emitting organic light-emitting devices using Fe3O4 modified Ag anode

Highly efficient top-emitting organic light-emitting devices (TOLEDs) using a Fe3O4 modified Ag anode have been demonstrated. The tris-(8-hydroxyquinoline) aluminum-based TOLEDs exhibit a very low turn-on voltage of 2.5 V and a high current efficiency of 8.1 cd/A. The improved properties for the TOLEDs is mainly due to the enhanced hole injection by introducing the anodic buffer. The mechanism of this enhanced hole injection is studied by the X-ray and ultra-violet photoemission spectroscopy, which demonstrated that the dipole layer is formed at the anode/organic interface and the hole-injection barrier is therefore reduced after introducing the thin Fe3O4 film between the Ag anode and the hole-transport layer.