White organic light emitting devices with thin 4-(dicyanomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) layer
In this letter, we have fabricated an efficient, color stable white organic electroluminescent device through the incorporation of double thin 4-(dicyanomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) emitting layers and 4,4?-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB), a hole transporting and blue emitting material. The device structure is ITO/NPB 45nm/DCJTB 0.15nm/NPB 5nm/DCJTB 0.15nm/BCP 10nm/AlQ 50nm/LiF 0.3nm/Al 150nm. This device exhibited a pure white-light emission having Commission Internationale de IEclairage (CIE) coordinates of (0.324, 0.336), a current efficiency of 2.9cd/A and a maximum brightness of 7016cd/m2. When the current density increased from 2mA/cm2 to 100mA/cm2, we observed only a slight shifting in the CIE coordinates from (0.324, 0.336) to (0.320, 0.326). Moreover, the efficiency of the device with double thin emitting layers of DCJTB is two times higher than the device with only one DCJTB layer.
electroluminescent hole organic light emitting devices (oleds) electron