Efficient white organic light-emitting devices are demonstrated by inserting a thin layer of tris (8-hydroxyquinoline) aluminum (Alq) doped with 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl) (DCJTB) into N,N'-diphenyl-N,N'-bis(1-naphthyl)-(1,1'-biphenyl)-4,4'-diamine (NPB) layer. Alq without doping is used as an electron-transporting layer and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (bathocuproine or BCP) as an exciton-blocking layer. NPB layers are separated by the doped Alq layer, the layer that sandwiched between BCP and doped Alq layers acts as a blue-emitting layer, and the other as a hole-transporting layer. The doped Alq layer acts as a red and green-emitting as well as chromaticity-tuning layer, whose thickness and position as well as the concentration of DCJTB in Alq permit the tuning of the device spectrum to achieve a balanced white emission with Commission Internationale De L'Eclairage coordinates of (0.33, 0.33), which are largely insensitive to the applied voltages, especially at high brightness (>1000cd/m2). The device have maximum luminance and efficiency of 6745 cd/m2 and 2.56 cd/A, respectively.
We studied electron injection form Al cathode into the tris(8-hydroxyquinoline)aluminum (Alq3). When a thin CsCl layer is inserted between Alq3 and Al, a substantial enhancement in electron injection is observed. The results show that the device with the cathode containing the ultrathin CsCl layer has a higher brightness and electroluminescent efficiency than the device without this layer. Further, organic light-emitting devices (OLEDs) based on tris-(8-hydroxyquinoline)aluminum using a trilayer of CsCl/LiF/Al as cathodes have been fabricated. The results show that the device with the cathode containing 0.5 nm CsCl layer and 1.0 nm LiF layer has a higher brightness and electroluminescent efficiency than that of the device with LiF/Al or CsCl/Al cathodes. The maximum EL efficiency of the CsCl/LiF/Al cathode device is 3.41 cd/A, which is higher than the 2.74 cd/A of the LiF/Al device and 2.49 cd/A of the CsCl/Al device.
Si02 films were fabricated on Si substrates by flame hydrolysis deposition (FHD) as buffer layer of waveguides. The
optical and surface properties of the films were characterized using scanning electron microanalyzer (SEM), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and variable angle spectroscopic ellipsometry (VASE). From a series of analyses, we demonstrated the excellent silica films fabricated. It proves that Si02 films prepared by flame hydrolysis deposition are entirely able to be applied in planar optical waveguides.