High performance inkjet printed phosphorescent organic light emitting diodes based on small molecules commonly used in vacuum processes

Abstract High efficiency phosphorescent organic light emitting diodes (OLEDs) are realized by inkjet printing based on small molecules commonly used in vacuum processes in spite of the limitation of the limited solubility. The OLEDs used the inkjet printed 5 wt.% tris(2-phenylpyridine)iridium(III) (Ir(ppy) 3 ) doped in 4,4′-Bis(carbazol-9-yl)biphenyl (CBP) as the light emitting layer on various small molecule based hole transporting layers, which are widely used in the fabrication of OLEDs by vacuum processes. The OLEDs resulted in the high power and the external quantum efficiencies of 29.9 lm/W and 11.7%, respectively, by inkjet printing the CBP:Ir(ppy) 3 on a 40 nm thick 4,4′,4″-tris(carbazol-9-yl)triphenylamine layer. The performance was very close to a vacuum deposited device with a similar structure.