Browsing by Author "Chu, Ta-Ya"

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A morphologically stable host material for efficient phosphorescent green and red organic light emitting devices
(2008-11-28)
Ho, Meng-Huan
;
Balaganesan, Banumathy
;
Chu, Ta-Ya
;
Chen, Teng-Ming
;
Chen, Chin H.
A carbazole-based host material, 4,4'-N,N'-[di(3, 6-di(t-butyl)carbazole]biphenyl (ttbCBP), with four t-butyl steric spacers on peripheral carbazole moieties was effectively synthesized through Friedel-Crafts Alkylation. Owing to the presence of sterically hindered t-butyl groups, ttbCBP exhibits a high glass transition temperature (175 degrees C) and is morphologically stable. This host material also preserves the characteristics of wide band-gap of 3.2 eV and high triplet energy of 2.64 eV. In addition, ttbCBP has been shown to be effective hosts for green and red phosphorescent emitters in organic electrophosphorescent devices. (C) 2008 Elsevier B.V. All rights reserved.
Ab initio molecular orbital calculation of 1,3,5-triazine derivatives as hosts for phosphorescent organic light emitting devices
(2005)
Chu, Ta-Ya
;
Ho, Meng-Huan
;
Chen, Jenn-Fang
;
Chen, Chin H.
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電子物理學系
Novel triplet host materials 2,4,6-tris (diarylamino)-1,3,5-triazine derivatives (TRZ1-TRZ4) have been reported and from which TRZ2 as a host for Ir(ppy)(3) was particularly useful in producing high efficiency phosphorescent organic light emitting diodes (OLEDs). This paper reports the molecular orbital and energy level of these derivatives determined by ab initio calculation. The calculated triplet bandgap energy of TRZ1 has been found to be larger than that of TRZ2.
Comparative study of single and multiemissive layers in inverted white organic light-emitting devices
(2006-09-11)
Chu, Ta-Ya
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Chen, Jenn-Fang
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Chen, Szu-Yi
;
Chen, Chin H.
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電子物理學系
The authors have fabricated and compared highly efficient inverted white organic light-emitting devices (WOLEDs) with a single emission layer (SEL) and with a multiemission layer (MEL). The efficiency levels of the WOLEDs with a SEL and a MEL achieved 13.0 cd/A, 10.6 lm/W and 11.3 cd/A, 7.3 lm/W, respectively. The projected half lifetime of a SEL device under an initial luminance of 400 cd/m(2) is expected to be over 34 000 h, which is five times better than that of a MEL device of 6350 h. The Commission International de l'Eclairage coordinates of a SEL device are not affected by aging. (c) 2006 American Institute of Physics.
High-Efficiency Inverted Transparent Blue Organic Light-Emitting Devices
(2006)
Chen, Szu-Yi
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Chu, Ta-Ya
;
Chen, Chao-Jung
;
Chen, Jenn-Fang
;
Chen, Chin H.
We report efficient inverted transparent blue OLEDs (ITOED) with an hole injection layer prepared by co-evaporation of WO3 with NPB, which achieved a total current efficiency 0 10.7 cd/A at 20 mA/cm(2) with light emits from both ITO bottom cathode and Au top anode in about 3:1 ratio.
Highly efficient and stable inverted bottom-emission organic light emitting devices
(2006-07-31)
Chu, Ta-Ya
;
Chen, Jenn-Fang
;
Chen, Szu-Yi
;
Chen, Chao-Jung
;
Chen, Chin H.
The authors report the development of highly efficient and stable C545T doped green fluorescent Alq(3) inverted bottom-emission organic light emitting device (OLED), with a device configuration of ITO/Mg/Cs(2)O:Bphen/Alq(3)/C545T:Alq(3)/NPB/WO(3)/Al, that achieved a maximum current efficiency of 23.7 cd/A and a power efficiency of 12.4 lm/W which are two times better than those of the conventional OLED. At a brightness level of 100 cd/m(2), the device required driving current density only as low as 0.5 mA/cm(2) at a driving voltage of only 5.0 V and its half-lifetime T(1/2) in excess of 104 000 h. (c) 2006 American Institute of Physics.
Iminodibenzyl-substituted distyrylarylenes as dopants for blue and white organic light-emitting devices
(2008-02-01)
Ho, Meng-Huan
;
Chang, Chia-Ming
;
Chu, Ta-Ya
;
Chen, Teng-Ming
;
Chen, Chin H.
A series of highly efficient blue materials based on iminodibenzyl-substituted distyrylarylene (IDB-series) fluorescent dyes using the concept of steric-compression have been designed and synthesized by means of a rigidized and over-sized ring. The steric-compression effect can shorten the effective conjugation length (chromophore) of the molecule and the added phenyl moiety in the core can alleviate the propensity for molecular aggregation. These materials also possess high glass transition temperature over 100 degrees C. The blue IDB-Ph device achieved a maximum external quantum efficiency of 4.8% with a Commission Internationale de I'Eclairage (CIEx,y) coordinate of (0.16, 0.28). When applied in two-element white OLED system, the IDB-Ph doped device achieved a luminance efficiency of 11.0 cd/A with a CIEx,y color coordinate of (0.29, 0.36). (c) 2007 Elsevier B.V. All rights reserved.
Stable inverted bottom-emitting organic electroluminescent devices with molecular doping and morphology improvement
(2006-07-31)
Chen, Szu-Yi
;
Chu, Ta-Ya
;
Chen, Jenn-Fang
;
Su, Chien-Ying
;
Chen, Chin H.
Stable inverted bottom-emitting organic light-emitting diodes (IBOLEDs) have been investigated by inserting n-type Cs2O dopant between indium-tin oxide bottom cathode and Alq(3), the combination of which not only improved the morphology of organic layer but enhanced the lifetime of the IBOLED. This n-type doped IBOLED achieved efficiencies of 5.2 cd/A and 2.0 lm/W at 20 mA/cm(2). The 20% decay lifetime (t(80)) of Cs2O doped IBOLED is 270 h which is about 1.7 times more stable than that of the conventional OLED (160 h) and 2.5 times of Li doped IBOLED (104 h). (c) 2006 American Institute of Physics.
Stilbene-based materials for blue organic light emitting devices
(2005)
Ho, Meng-Huan
;
Wu, Yao-Shan
;
Chu, Ta-Ya
;
Chen, Jenn-Fang
;
Chen, Chin H.
We introduce a new series of blue emitting material with stilbene molecular nucleus and attempt to improve the color purity and EL efficiency of blue OLEDs. When (E)-4,4'-bis(diphenylamino)stilbene (SB-1) was doped in a stable blue host material, 2-methyl-9, 10-di(2-naphthyl)anthracene (MADN), the blue device achieved an EL efficiency of 2.8 cd/A and a power efficiency of 1.5 lm/W at a current density of 20 mA/cm(2) with a deep blue CIEx,y cordinates of (0.15, 0.16).