Highly efficient and stable red phosphorescent organic light-emitting device using bis[2-(2-benzothiazoyl)phenolato]zinc(II) as host material

The red-emitting phosphorescent organic light-emitting device employing Bis[2-(2-benzothiazoyl)phenolato]zinc(II) ( Zn ( BTP ) 2 ) as a host material has been demonstrated. The device generates saturated red emission with Commission Internationale de l'Eclairage coordinates of (0.67, 0.33), characterized by a low driving voltage of 3.2 V and high external quantum efficiency of 10.3% at 10 mA ∕ cm 2 . Moreover, the efficiency and lifetime are improved by using 30% NPB-doped Zn ( BTP ) 2 host in the emitting layer, where NPB is 4, 4 ′ -bis( N -phenyl-1-naphthyl-amino)biphenyl. The maximum external quantum efficiency of the device reaches 12.6% at 1.7 mA ∕ cm 2 . The device has exhibited excellent stability. The half-luminance lifetime is 240 h at 80 mA ∕ cm 2 (initial luminance of 6070 cd ∕ m 2 ). The relationship between the employed host material and device performance is discussed.