Browsing by Author "Chuen, CH"

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Bis(2,2-diphenylvinyl)spirobifluorene: An efficient and stable blue emitter for electroluminescence applications
(2005-08-15)
Wu, FI
;
Shu, CF
;
Wang, TT
;
Diau, EWG
;
Chien, CH
We have synthesized a spirobifluorene-based DPVBi [4,4'-bis(2,2-diphenylvinyl)-1,1'-biphenyl] analogue, DPVSBF [2,7-bis(2,2diphenylvinyl)-9,9'-spirobifluorene], in which the bis(2,2-diphenylvinyl) groups are connected through the 2 and 7 positions of the spirobifluorene framework, and have characterized its thermal properties, electronic properties (viz. absorption and photoluminescence), and electrochemical behavior. The presence of the rigid spirobifluorene linkage imparts significant improvement in the material's glass transition temperature and morphological stability, while preserving most of the photophysical and electronic properties of its non-spiro, biphenyl analogue, DPVBi. Organic electroluminescent devices having the structure ITO/NPB/DPVSBF/AlQ/LiF/Al display bright emissions with a lambda(max) at 474 nm (CIE coordinates: 0.16, 0.24) and exhibit maximum luminescence exceeding 40,000 cd/m(2). At a driving current density of 100 mAcm(2) (6.4 V), a luminance of 4110 cd/m(2) was obtained with external quantum efficiency of 2.54%, luminance efficiency of 4.1 cd/A, and power efficiency of 2.0 lm/W. Moreover, the DPVSBF-based device exhibits a 16-fold enhancement in the operation lifetime relative to that of a similar device based on DPVBi. (C) 2005 Elsevier B.V. All rights reserved.
White organic light-emitting diodes based on 2,7-bis(2,2-diphenylvinyl)-9,9 '-spirobifluorene: Improvement in operational lifetime
(2004-11-15)
Chuen, CH
;
Tao, YT
;
Wu, FI
;
Shu, CF
;
應用化學系
Very bright white organic light-emitting diodes were fabricated using 2,7-bis(2,2-diphenylvinyl)-9,9(')-spirobifluorene (DPVSBF) doped with [4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran)] (DCJTB) as the emission layer. With a device configuration of ITO/NPB(40 nm)/DPVSBF:0.2%DCJTB(11 nm)/Alq(30 nm)/LiF(1 nm)/Al(150 nm), a brightness of 1575 cd/m(2) with an external quantum efficiency of 3.31% and luminous efficiency of 8.00 cd/A, a power efficiency of 5.35 lm/W was achieved at a driving current of 20 mA/cm(2) (4.7 V). The brightness reached 66 000 cd/m(2) at 15 V. The Commission Internationale de l'Eclairage coordinates stayed nearly constant, changed from (0.35, 0.36) to (0.32, 0.34) when the voltage increased from 6 to 12 V. The relative operational lifetime of the device increased by a factor of similar to20 compared with a similar device based on 4,4(')-bis-(2,2-diphenylvinyl)-1,1(')-biphenyl as the source of the blue emission. The much extended half-lifetime was attributed to the higher morphological stability of the DPVSBF. (C) 2004 American Institute of Physics.