We have measured electron mobility in vacuum-deposited films of 4,7-diphenyl-1,10phenanthroline (bathophenanthroline, or BPhen) using a time-of-flight technique. Electron transport was highly dispersive for BPhen with a dispersion parameter of a value 0.30. The electron mobility in excess of 10−4 cm2/V s has been observed at electric fields of the order of 105 V/cm with weakly dependent on the electric field. The characteristic energy of the distribution is obtained a value 0.09 eV. It is directly confirmed that the BPhen has superior electron-transport capability.
We fabricated nondoped white organic electroluminescent devices using vacuum-deposited thin films of blue-emitting 4,4′-bis[N-1-napthyl-N-phenyl-amino]biphenyl (α-NPD) and orange-emitting 4-(dicyanomethylene)-2-metyl-6-(p-dimethyl aminostyryl)-4H-pyran (DCM), a hole-blocking layer of 2-(4-biphenyl)-5-(p-tert-butylphenyl)-1,3,4-oxadiazole (tBu-PBD) and electron-transporting tris(8-quinolinolato) aluminum (III). Excitons formed at the α-NPD/tBu-PBD interface sequentially transfer their energy to α-NPD via the Förster mechanism. The exciton is captured by an ultrathin DCM layer located within the pure α-NPD layer. The position of the DCM determines the device spectrum, and enables a white emission to be achieved. The spectrum is not sensitive to the voltage applied, and the devices show maximum luminance of about 1000 cd/m2.
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