Browsing by Author "Chen, KB"

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New soluble poly(2,3-diphenylphenylene vinylene) derivatives for light-emitting diodes
(2005-04-22)
Yang, SH
;
Chen, JT
;
Li, AK
;
Huang, CH
;
Chen, KB
Soluble poly(2,3-diphenylphenylene vinylene) (DP-PPV) derivatives, poly(2,3-diphenyl-5-(4-heptyloxy-4'-oxytrimethylenediphenyl)phenylene vinylene) (P1), poly(2,3-diphenyl-5-[4-(4-pentylcyclohexyl)phenoxyl-propyl-p-phenylene vinylene) (P2) and poly(2,3-diphenyl-5-(2-(1, 4, 5-triphenyl-1H-2-imidazoloyl)-1-oxytrimethylene phenyl) phenylene vinylene) (P3), were synthesized. P1 and P2 contain liquid crystal side groups; while P3 contains a charge transport group. The polymers showed solid state UV-Visible absorption and photoluminescence in the range of 370-380 and 480-510 nm, corresponding to blue green emission. Similar to many other reported systems, the solution fluorescence spectra of P1 and P2 showed slight solvent dependency and blue-shifted with respect to those of the films. These were not the case for P3 which showed little solvent dependency and little blue shift in solution. Two-layer light-emitting devices with a simple ITO/PEDOT/polymer/Ca (Al) configuration were fabricated and characterized. (c) 2004 Elsevier B.V. All rights reserved.
Novel poly(2,3-biphenyl-1,4-phenylenevinylene) derivatives containing long branched alkoxy and fluorenyl substituents: Synthesis, characterization, and their applications for polymer light-emitting diodes
(2005-10-18)
Chen, KB
;
Li, HC
;
Chen, CK
;
Yang, SH
;
Hsieh, BR
Two series of poly(2,3-Biphenyl-1,4-phenylenevinylene) (DP-PPV) derivatives containing long branched alkoxy chains or fluorenyl substituents were synthesized. The branched alkoxy groups were introduced to enhance the solubility for spin-coating processes. Bulky fluorenyl groups with two hexyl chains on the 9-position were introduced to increase steric hindrance and prevent close packing of the main chain. By controlling the feed ratio of different monomers during polymerization, DP-PPV derivatives with high molecular weights were obtained. All synthesized polymers possess high glass transitions temperatures and thermal stabilities. The maximum photoluminescent emissions of the thin films are located between 498 and 564 nm. Cyclic voltammetric analysis reveals that the band gaps of these light-emitting materials are in the range from 2.4 to 2.5 eV. A double-layer electroluminescent device with the configuration of ITO/PEDOT/polymer 2/Ca/Al exhibited a low turn-on voltage (4.0 V), a very high external quantum efficiency (3.39 cd/A), and a high brightness (16 910 cd/m(2)).
Synthesis and light emitting properties of polyacetylenes having pendent fluorene groups
(2006-01-01)
Huang, CH
;
Yang, SH
;
Chen, KB
;
Hsu, CS
;
應用化學系
Five novel fluorene-containing polymers, poly[(9,9-dimethylfluoren-2-yl)acetylenel (PFA1), poly[(1-pentyl-2-(9,9-dimethylfluoren-2-yl)acetylene) (PFA2), poly[1-decyl-2-(9,9-dimethylfluoren-2-yl)acetylene] (PFA3), poly[1-phenyl-2-(9,9-dimethylfluoren-2-yl)acetylenel (PFA4), and poly[1-(3,4-difluorophenyl)-2-(9,9-dimethylfluoren-2yl)acetylene] (PFA5) were synthesized by the polymerization of the corresponding fluorene-substituted acetylenic monomers (M1-M5), using WCl6, MoCl5, and TaCl5 as catalysts and n-Bu4Sn as a cocatalyst. The synthesized polymers were thermally stable and readily soluble in common organic solvents. The degradation temperatures for a 5% weight loss of the polymers were similar to 352-503 degrees C under nitrogen. PFA1-PFA5 show emission peaks from 402 to 590 nm. Besides, their electroluminescent properties were studied in heterostructure light-emitting diodes (LEDs), using PFA2-PFA5 as an emitting layer. The PFA5 device revealed an orange-red emission peak at 602 nm with a maximum luminescence of 923 cd/m(2) at 8 V. A device with the ITO/PEDOT/ a mixture of PFA2 (98 wt %) and PFA5 (2 wt %)/Ca/Al showed near white emission. Its maximum luminance and current efficiency are 450 cd/m(2) at 15 V and 1.3 cd/A, respectively. 0 2005 Wiley Periodicals, Inc.
Synthesis and opto-electrical properties of stellar polyfluorene derivatives containing polyhedral oligomeric silsesquioxanes as the center core
(2006-06-01)
Chen, KB
;
Chen, HY
;
Yang, SH
;
Hsu, CS
;
應用化學系
Three polyfluorene derivatives (P1-P3) emitting blue, green and red light were prepared via a Suzuki coupling method. Polyhedral oligomeric silsesquioxanes (POSS) were integrated into the center core of the derivatives to create stellar light-emitting polymers (POSS-P1-POSS-P3). The glass-transition and decomposition temperatures were raised after introducing POSS moieties. The starlike polymers showed a reduced emissive band at 540 nm when annealing at 200 degrees C. The result implies that integrated POSS at the center core suppresses the keto effect generally occurring for polyfluorenes. Double-layer light-emitting devices of indium tin oxide/poly(ethylenedioxythiophene)/polymer/Ca/Al were fabricated to evaluate polymer potential. Compared with pristine polymers, the maximum brightness and the current efficiency of devices using POSS-containing polymers as active layers were enhanced. A blending method using P1 or POSS-P1 as the host matrix further improved device performance.