Efficient blue organic light-emitting devices based on solution-processed starburst macromolecular electron injection layer

Highly efficient blue organic light-emitting devices using an alcohol-soluble conjugated starburst macromolecule TrOH as electron injection layer were investigated. Multilayered OLEDs based on a blue polymer poly(9,9-dioctylfluorene) (PFO) and a blue small molecule 1,6-bis(3′,6′-bis(octyloxy)spiro [fluorene-9,9′- xanthene]-2-yl)pyrene (DOSFXPy) were fabricated by solution-processing. The devices exhibit low turn-on voltages of 3.8 V (PFO) and 3.5 V (DOSFXPy), and high current efficiencies of 4.3 cd/A (PFO) and 3.1 cd/A (DOSFXPy), respectively, which are better than those of the devices using TPBi/LiF as electron injection layer. These improved properties are attributed to the reduced barrier for electron injection by inserting a TrOH electron injection layer.