Browsing by Author "Jen, AKY"

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A convenient modular approach of functionalizing aromatic polyquinolines for electrooptic devices
(1999-08-01)
Ma, H
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Jen, AKY
;
Wu, JY
;
Wu, XM
;
Liu, S
A versatile and generally applicable synthetic method for making second-order nonlinear optical (NLO)side-chain aromatic polyquinolines has been developed. This approach emphasizes the ease of incorporating NLO chromophores onto the pendent phenyl moieties of parent polyquinolines at the final stage via a mild Mitsunobu reaction, which provides the synthesis of NLO polyquinolines with a broad variation of polymer backbones and great flexibility in the selection of chromophores. The synthesized NLO side-chain polyquinolines possess high glass transition temperature (T-g > 200 degrees C), good processability, and excellent thermal stability. The promising results of electrooptic (EO) activity (up to 35 pm/V at 830 nm and 22 pm/V at 1300 nm), optical loss (1.5-2.5 dB/cm), and long-term stability of the poling-induced polar order (r(33) values retained > 90% of their original values at 85 degrees C for more than 1000 h) have demonstrated the advantages of this design approach. The excellent combination of these properties in the resulting polymers have also provided a great promise in the development of EO devices.
A new synthetic approach for nonlinear optical chromophores possessing enhanced thermal stability
(1996-09-23)
Shu, CF
;
Tsai, WJ
;
Jen, AKY
;
應用化學系
;
Department of Applied Chemistry
A synthetic strategy for NLO chromophores containing cyclic-locked, conjugated triene segment has been developed. The incorporation of the ethylenic bonds into a 6-membered ring resulted in enhanced thermal stabilities of chromophores. Copyright (C) 1996 Elsevier Science Ltd
A new synthetic approach for nonlinear optical chromophores possessing enhanced thermal stability
(1996-09-23)
Shu, CF
;
Tsai, WJ
;
Jen, AKY
;
應用化學系
;
Department of Applied Chemistry
A synthetic strategy for NLO chromophores containing cyclic-locked, conjugated triene segment has been developed. The incorporation of the ethylenic bonds into a 6-membered ring resulted in enhanced thermal stabilities of chromophores. Copyright (C) 1996 Elsevier Science Ltd
A side-chain dendronized nonlinear optical polyimide with large and thermally stable electrooptic activity
(2004-01-27)
Luo, JD
;
Haller, M
;
Li, HX
;
Tang, HZ
;
Jen, AKY
Bright red-emitting electrophosphorescent device using osmium complex as a triplet emitter
(2003-07-28)
Kim, JH
;
Liu, MS
;
Jen, AKY
;
Carlson, B
;
Dalton, LR
A series of efficient and bright double-layer light-emitting devices have been fabricated using the osmium (Os) complex as the triplet emissive dopant in both a blue-emitting polyfluorene derivative (PF-TPA-OXD) containing hole-transporting triphenylamine (TPA) and electron-transporting oxadiazole (OXD) as side chains and a blend of 2-(4-t-butylphenyl)-5(4-biphenylyl)-1,3,4-oxadizole (PBD) in poly(N-vinylcarbazole) (PVK). Due to a balanced charge injection and transport in PF-TPA-OXD and very efficient energy transfer from this polymer to the Os complex, the resulting device (indium tin oxide/HTL/OsCF3:PF-TPA-OXD/Ca/Ag) reaches a maximum external quantum efficiency of 2.1% with a peak brightness of 2920 cd/m(2). These results are significantly higher than those obtained from the commonly used host, PVK:PBD (0.49% and 1270 cd/m(2)). (C) 2003 American Institute of Physics.
Bright white light electroluminescent devices based on a dye-dispersed polyfluorene derivative
(2004-08-16)
Kim, JH
;
Herguth, P
;
Kang, MS
;
Jen, AKY
;
Tseng, YH
A series of efficient and bright white light-emitting diodes were fabricated using the blends of two fluorene-derived fluorescent dyes, (4,7-bis-(9,9,9('),9(')-tetrahexyl-9H,9(')H-[2,2(')]bifluoren-7-yl)-benzo[1,2,5]thiadiazole) (FFBFF-emits green) and (4,7-bis-[5-(9,9-dihexyl-9H-fluoren-2-yl)-thiophen-2-yl]-benzo[1,2,5]thiadiazole) (FTBTF-emits red) in an efficient blue-emitting polyfluorene-derived copolymer (poly[(9,9-bis(4-di(4-n-butylphenyl)aminophenyl))]-stat-(9,9-bis(4-(5-(4-tert-butylphenyl)-2-oxadiazolyl)-phenyl))-stat-(9,9-di-n-octyl)fluorene) (PF-TPA-OXD). The resulting white light-emitting device reaches a maximum external quantum efficiency of 0.82% and a maximum brightness of 12 900 cd/m(2) at 12 V. The Commission Internationale d'Enclairage chromaticity coordinates of the device remain very close to that of pure white emission at a relatively broad bias range from 6 V (x=0.36, y=0.37) to 12 V (x=0.34, y=0.34). (C) 2004 American Institute of Physics.
High-efficiency polymer light-emitting diodes using neutral surfactant modified aluminum cathode
(2006-03-30)
Niu, YH
;
Jen, AKY
;
Shu, CF
;
應用化學系
;
Department of Applied Chemistry
High-efficiency polymer light-emitting diodes were fabricated by inserting a layer of nonionic neutral surfactant between the electroluminescent (EL) layer and the high-work-function aluminum cathode via spin coating. It was found that both the poly(ethylene glycol)- and poly(propylene glycol)-based surfactants as well as their copolymers can all demonstrate similar performance enhancement. Device performances comparable to or even better than those of the control devices using calcium as the cathode have been achieved for both poly(p-phenylene)-based and polyfluorene-based conjugated polymers with orange-red, green, and blue emission colors. It is possible that when both surfactant and aluminum are used as the cathode, the abundant hole injection through a hole-transporting layer and hole pile-up at the inner side of the EL/surfactant interface might cause an effective electric field to induce the realignment of the dipole moment of those polar surfactant molecules, thus lowering the barrier for electron injection. In addition, the coordination between the aluminum and oxygen atoms on the surfactant might cause n-type doping in the areas near surfactant in the EL polymer layer that causes the enhancement of electron injection.
Highly efficient blue-light-emitting diodes from polyfluorene containing bipolar pendant groups
(2003-09-09)
Shu, CF
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Dodda, R
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Wu, FI
;
Liu, MS
;
Jen, AKY
A highly efficient blue-light-emitting copolymer with bulky hole-transporting triphenylamine (TPA) and electron-transporting oxadiazole (OXD) pendant groups at the C-9 position of fluorene was synthesized. The results from photoluminescence and electrochemical measurements reveal that both the side chains and the polyfluorene main chain retain their own electronic characteristics in the copolymer. It shows a pure blue emission with no aggregates or excimers formed even after being annealed at 150 degreesC under nitrogen for 20 h. In addition, it also demonstrates improved charge injection and balanced charge transport in electroluminescence. The maximum external quantum efficiency of a single-layer device using this copolymer as the emitting layer is 1.21% (at a brightness of 354 cd/m(2) with driving voltage of 7.6 V). The maximum luminance of the device reaches 4080 cd/m(2) at a bias of 12.0 V and a current density of 640 mA/cm(2).
Highly efficient electrophosphorescent devices with saturated red emission from a neutral osmium complex
(2005-06-28)
Niu, YH
;
Tung, YL
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Chi, Y
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Shu, CF
;
Kim, JH
Highly efficient electrophosphorescent polymer light-emitting diodes (LEDs) with saturated red emission (Commission Internationale de L'Eclairage chromaticity coordinates exactly at x = 0.67, y = 0.33) are achieved by blending a novel neutral Osmium complex into a single-component bipolar polymer host that possesses balanced hole- and electron-transporting ability. By using a tetraphenylenebiphenyldiamine (TPD)-based cross-linkable hole-transport layer as well as a layer of 1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene (TPBI) as an electron-tran sport layer, a device structure with both effective hole/electron injection and efficient carriers/excitons blocking or confinement at both electrode sides is constituted. In this way, external quantum efficiency 12.8% is reached the first time with an organometallic complex with heavy metal core other than iridium.
Highly efficient red electrophosphorescent devices based on an iridium complex with trifluoromethyl-substituted pyrimidine ligand
(2004-08-30)
Niu, YH
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Chen, BQ
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Liu, S
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Yip, H
;
Bardecker, J
Highly efficient red-emitting electrophosphorescent devices were fabricated by doping an iridium (Ir) complex containing trifluoromethyl (CF3)-substituted pyrimidine ligand into a conjugated bipolar polyfluorene with triphenylamine and oxadiazole as side chains. The device efficiency can be enhanced through effective exciton confinement using a layer of 1,3,5-tris(N- phenylbenzimidazol-2-yl)benzene on the cathode side and a layer of in situ polymerized tetraphenyldiamine-perfluorocyclobutane on the anode side. For a blend with 5 wt % of the Ir complex, a maximum external quantum efficiency of 7.9 photon/electron % and a maximum brightness of 15800 cd/m(2) are reached with Commission Internationale de L'Eclairage chromaticity coordinates of x=0.65 and y=0.34. (C) 2004 American Institute of Physics.
Highly efficient red-electrophosphorescent devices based on polyfluorene copolymers containing charge-transporting pendant units
(2005-07-28)
Wu, FI
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Shih, PI
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Tseng, YH
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Chen, GY
;
Chien, CH
We have systematically examined the photoluminescence (PL) and electroluminescence (EL) behavior of blends comprising two efficient red phosphors doped, respectively, into the blue-emitting polyfluorene derivatives PF-TPA-OXD and PF-OXD. The host polymers, which contain both hole- and electron-transporting or merely electron-tran sporting side chains, are capable of facilitating charge injection and transport. After determining the HOMO and LUMO energy levels of these materials, we were able to match the dopant with its most suitable host to achieve the direct formation and confinement of an exciton at the dopant. This configuration also leads to a reduction in the electrical excitation of the host polymer, which in turn decreases the degree of exciton loss arising from nonradiative decay of the host triplet. Using this approach, we were able to realize the production of high-performance red-electrophosphorescent devices. For Os(fppz)-doped devices, we obtain a balanced charge recombination in conjunction with higher current and luminance when using PF-TPA-OXD as the host matrix; this device reached a maximum external quantum efficiency of 8.37% with a peak brightness of 16 720 cd/m(2). The absence of charge-transporting pendant units, i.e., the device fabricated from poly [9,9-dioctylfluorene-2,7-diyl] (POF), led, however, to relatively poor electroluminescence characteristics (5.81% and 2144 cd/m(2)).
Material and interface engineering for high-performance light-emitting diodes.
(2005-03-13)
Jen, AKY
;
Niu, YH
;
Liu, MS
;
Yip, H
;
Kang, MS
Nonlinear optical chromophores with configuration-locked polyenes possessing enhanced thermal stability and chemical stability
(1998-11-01)
Shu, CF
;
Shu, YC
;
Gong, ZH
;
Peng, SM
;
Lee, GH
A synthetic strategy has been developed for preparation of NLO chromophores with all the pi-conjugated methine groups incorporated into plane-rigidified, fused, six-membered rings. The comparison of the rigidified chromophores to the analogous nonrigid chromophores shows that the configuration-locking methods provide a dramatic enhancement of molecular thermal stability. The data from W-vis spectroscopy and X-ray crystallography reveal that the rigidity of the annulated rings does not diminish the planarity and the electron delocalization efficiency of the polyenic chain.
Nonlinear optical chromophores with configuration-locked polyenes possessing enhanced thermal stability and chemical stability
(1998-11-01)
Shu, CF
;
Shu, YC
;
Gong, ZH
;
Peng, SM
;
Lee, GH
A synthetic strategy has been developed for preparation of NLO chromophores with all the pi-conjugated methine groups incorporated into plane-rigidified, fused, six-membered rings. The comparison of the rigidified chromophores to the analogous nonrigid chromophores shows that the configuration-locking methods provide a dramatic enhancement of molecular thermal stability. The data from W-vis spectroscopy and X-ray crystallography reveal that the rigidity of the annulated rings does not diminish the planarity and the electron delocalization efficiency of the polyenic chain.
Novel oxadiazole-containing polyfluorene with efficient blue electroluminescence
(2003-01-14)
Wu, FI
;
Reddy, DS
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Shu, CF
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Liu, MS
;
Jen, AKY
A novel oxdiazole-containing polyfluorene copolymer (PF-OXD) was synthesized by attaching two electron-deficient, 4-tent-butylphenyl-1,3,4-oxadiazole groups onto the C-9 position of the alternating fluorene unit to form a 3-D cardo-structure. This polymer possesses a very high glass transition temperature (T-g: 213 degreesC) and very good thermal stability due to its rigid cardo-linkage. The results from the photoluminescence measurements of the isothermally heated PF-OXD thin film (150 degreesC for 20 h) show that the commonly observed aggregate/excimer formation in polyfluorenes is very effectively suppressed in this polymer due to its 3-D structure and high T-g. A double-layer LED device using this polymer as the emitting layer shows a bright blue emission with a low turn-on voltage at 5.3 V and a high brightness of 2770 cd/m(2) at a drive voltage of 10.8 V. The maximum external quantum efficiency is 0.52% at 537 cd/m(2) with a bias of 7.4 V. The improved device performance over that of poly(9,9-dioctylfluorene) (POF) may be due to better electron injection and transport in PF-OXD and the efficient energy transfer from the OXD side chain to the polyfluorene main chains.
Recent development of electro-optic polymers for device applications.
(1997-09-07)
Jen, AKY
;
Marder, SR
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Shu, CF
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應用化學系
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Department of Applied Chemistry
Synthesis and characterization of nonlinear optical chromophores with conformationally locked polyenes possessing enhanced thermal stability
(1999-06-01)
Shu, YC
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Gong, ZH
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Shu, CF
;
Breitung, EM
;
McMahon, RJ
Dipolar NLO chromophores with an interposed conjugated tetraene segment in which all but four of the methine groups are incorporated into a tetrahydronaphthalene framework have been synthesized and characterized. This conformation-locking approach furnishes NLO chromophores possessing an enhanced thermal stability. X-ray crystallographic data indicate that the polyenic chain of these molecules exhibits a near-planar all-trans conformation in the solid state. EFISH measurements show that these conformationally locked tetraenic chromophores exhibit large second-order optical nonlinearities (mu.beta similar to 4000 x 10(-48) cm(6) at 1907 nm), although the nonlinearities of the corresponding "unlocked" analogues are slightly larger.
Synthesis of second-order nonlinear optical chromophores with enhanced thermal stability and nonlinearity: A conformation-locked trans-polyene approach
(1996-10-07)
Shu, CF
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Tsai, WJ
;
Chen, JY
;
Jen, AKY
;
Zhang, Y
A facile synthesis that combines the use of an easily polarizable thiophene ring and a ring-locked triene as efficient conjugating moieties is employed to simultaneously enhance molecular nonlinearity (as high as 13 000 x 10(-48) esu) and thermal stability; incorporating this highly nonlinear chromophore in polyquinoline results in high electrooptic activity and long-term alignment stability at 100 degrees C for more than 1000 h.