A novel red organic light-emitting diode with ultrathin DCJTB and Rubrene layers

A novel red organic electroluminescent diode based on an ultrathin 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) layer has been fabricated. The device with the ultrathin DCJTB layer inserted between N, N′-bis-(1-naphthyl)-N, N′-diphenyl-1,1′-biph-enyl-4,4′- diamine (NPB) and tri-(8-hydroxyquinoline) aluminum (Alq3) layers has an emission from both DCJTB and Alq3. When utilizing the 5,6,11,12-tetraphenylnaphthacene (Rubrene) bilayer as the emitting-assistant layer in the fabrication of the device, the emission from Alq3 disappears. We attribute the improvement of color purity to the exciton confinement and energy transfer from the Rubrene molecular. The device with 0.1 nm DCJTB layer has a luminance of 1130 cd/m2 at 20 mA/cm2 with an EL efficiency of 5.6 cd/A, and the CIE coordinates was [0.617, 0.379]. The maximum brightness of this device reaches 21,525 cd/m2.

Research highlights
► A novel red organic electroluminescent diode based on ultrathin DCJTB and Rubrene layer has been fabricated.
► Utilizing the Rubrene bilayer as the emitting-assistant layer in the fabrication of the device, the emission from Alq3 disappears.
► The improvement of color purity and efficiency are come from the exciton confinement and energy transfer from the Rubrene molecular.