Browsing by Author "Zheng, HG"

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Organic electroluminescent derivatives containing dibenzothiophene and diarylamine segments
(2005)
Huang, TH
;
Whang, WT
;
Shen, JY
;
Lin, JT
;
Zheng, HG
A new series of 2,8-disubstituted dibenzothiophenes have been successfully synthesized via palladium-catalyzed C-N or C-C bond formation using 2,8-dibromodibenzothiophene and diarylamines as starting materials. These new dibenzothiophene derivatives are amorphous with a glass transition temperature ranging from 86 to 190 degrees C. Furthermore, they are fluorescent in the blue to bluish green region. Two types of light-emitting diodes ( LED) were constructed from these compounds, ( I) ITO/Cpd/TPBI/LiF/Al and (II) ITO/Cpd/Alq3/LiF/Al, where TPBI and Alq(3) are 1,3,5-tris(N-phenylbenzimidazol-2-yl) benzene and tris(8-hydroxyquinolinato) aluminium, respectively. In type I devices, the compounds function as the hole-transporting and emitting material. In type II devices, emission from Alq3 is observed. Several type I devices emit pure blue light, and most of the devices II have very promising performance. The relation between the energy levels of the materials and the performance of the light-emitting diodes is discussed.
Quinoxalines incorporating triarylamines: Dipolar electroluminescent materials with tunable emission characteristics
(2006-02-01)
Huang, TH
;
Whang, WT
;
Zheng, HG
;
Lin, JTS
;
材料科學與工程學系
Dipolar compounds (abbreviated as QuPy) featuring quinoxaline acceptors and diarylamine or triarylamine donors were prepared via palladium-catalyzed C-N or C-C bond formation in good yields. They possess high thermal stability with a high decomposition temperature (T-d > 400 degrees C) and exhibit no crystalline character. The emission colors of the materials vary from green to orange red and are dependent on the nature of the electron-withdrawing segments and solvents. Two types of double-layer organic light-emitting diodes (OLEDs) were constructed using these dipolar compounds as hole-transporting/emitting layers and TPBI or Alq(3) as an electron-transporting layer: (I) ITO/QuPy/Alq(3)/Mg:Ag and (II) ITO/QuPy/TPBI/Mg:Ag (TPBI = 1,3,5-tris(N-phenylbenzimidazol-2-yl)-benzen; Alq(3) = 1,3,5-tris(N-phenyl-benzimidazol-2-yl)-benzene). The recombination zone in most of those devices were confined in the quinoxaline layers, The green to orange colors in these devices correspond well with the film PL of the material used. The relation between the energy levels of the compounds and the performance of the light-emitting diode are discussed.