High efficiency red organic light-emitting devices using tetraphenyldibenzoperiflanthene-doped rubrene as an emitting layer

Red organic light-emitting devices (OLEDs) have been developed employing a novel fluorescent emitting layer, tetraphenyldibenzoperiflanthene-doped rubrene. The devices are characterized by low driving voltage below 4 V at a current density of 20 mA ∕ cm 2 and high color purity with Commission Internationale de l'Eclairage coordinates of (0.66, 0.34). The OLED using the novel emitting layer in combination with the electron-transporting layer consisting of 9,10-bis[4-(6-methylbenzothiazol-2-yl)phenyl]anthracene exhibits a high power efficiency of 5.3 lm ∕ W at a current density of 20 mA ∕ cm 2 . The half-luminance lifetime of the red OLED is 223 h at a current density of 80 mA ∕ cm 2 (initial luminance of 3570 cd ∕ m 2 ). Both the driving voltage and current efficiency of the device are significantly improved compared to a device using tris(8-quinolinolato)aluminum as an electron-transporting layer. The studies on charge transport for the host materials indicate that the high efficiency is attributed to the improved charge injection and balance in the device.