Wei-Sheng Huang

National Chiao Tung University, Hsin-chu-hsien, Taiwan, Taiwan

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Publications (7)31.45 Total impact

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    ABSTRACT: A series of novel electroluminescent main-chain copolymers containing fluorene-1,4-bis(9-octyl-9H-carbarzol-3yl)-2,5-dioctyloxy-benzene (BCB) segments and phosphorescent benzimidazole-based iridium (Ir) complexes in the backbones were synthesized by Suzuki coupling reaction. The relative intensity of phosphorescence and fluorescence were affected by the energy transfer and back transfer efficiencies between the polymer backbones and the iridium units as evidenced by solid state PL and EL spectra. PLED devices with a configuration of ITO/PEDOT: PSS (70 nm)/Ir-copolymers (P3–P10) or Ir-doped copolymers (P1–P2 doped with Ir-complex 4) (60–80 nm)/TPBI (40 nm)/LiF (1 nm)/Al (120 nm) were fabricated, where electroluminescence (EL) efficiencies depended on the chemical constituents and the triplet energies of the copolymers. PLED devices based on Ir-containing copolymerP8 or copolymerP2 doped with 5 mol% Ir-complex 4 exhibited white-light emissions with EL properties of ηext,max = 0.93%, ηc,max = 1.88 cd A−1, and Lmax = 1960 cd m−2 from the former (P8), and ηext,max = 4.09%, ηc,max = 10.94 cd A−1, and Lmax = 4870 cd m−2 from the latter (P2 doped with Ir-complex 4), respectively. The CIE coordinates, color-rendering index (CRI) and correlated color temperature (CCT) of the two PLED devices were (0.33, 0.30) at 13 V, 74 and 5966 K for the former, and (0.35, 0.32) at 15 V, 82 and 6147 K for the latter, respectively.
    Polymer Chemistry. 01/2010; 1(4).
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    ABSTRACT: A series benzoimidazole-based dendritric complexes of iridium dendrimers containing Fréchet-type dendrons with peripheral fluorenyl surface groups have been synthesized. These iridium dendrimers are green-emitting with high phosphorescence quantum yield, and can be spin-coated as films of good quality. From cyclic voltammograms (CV), high onset potentials at 1.42–1.58 V due to the peripheral fluorene group were observed. Device from a second generation dendrimer 17 with structure of ITO/PEDOT:PSS/CBP: 20 wt% 17/TPBI/LiF/Al (PEDOT:PSS = poly(ethylene dioxythiophene): polystyrenesulfonate and CBP = bis(N-carbazolyl)biphenyl) has the best performance: maximum external quantum efficiency of 13.58% and maximum current efficiency of 45.7 cd/A. Space-charge-limited current (SCLC) flow technique was used to measure the mobility of charge carriers in the blend films of the compounds in CBP. Blend films of higher generation dendrimers have lower hole mobility, albeit with higher device efficiencies.
    Organic Electronics 07/2009; · 3.84 Impact Factor
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    ABSTRACT: New pyrimidine derivatives (pyr) have been synthesized using palladium-catalyzed Suzuki coupling reaction. These compounds can undergo cyclometalation with iridium trichloride to form bis-cyclometalated iridium complexes, (pyr)(2)Ir(acac) (acac = acetylacetonate; pyr = cyclometalated pyr). The substituents at the both cyclometalated phenyl ring and pyrimidine ring were found to affect both electrochemical and photophysical properties of the complexes. Computation results on these complexes are consistent with the electrochemical and photophysical data. The complexes are green-emitting with good solution quantum yields at similar to 0.30. Light-emitting devices using these complexes as dopants were fabricated, and the device performance at 100 mA/cm(2) are moderate: 9 (17 481 cd/m(2), 4.8%, 18 cd/A, 5.1 lm/W); 10 (18 704 cd/m(2), 4.9%, 18.9 cd/A, 4.7 lm/W); 13 (20 942 cd/m(2), 5.4%, 21.0 cd/A, 6.1 lm/W). (C) 2009 Elsevier B.V. All rights reserved.
    Journal of Organometallic Chemistry 01/2009; 694(17):2757-2769. · 2.00 Impact Factor
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    ABSTRACT: A series of compounds containing arylamine and 1,2-diphenyl-1H-benz[d]imidazole moieties are developed as ambipolar, blue-emitting materials with tunable blue-emitting wavelengths, tunable ambipolar carrier-transport properties and tunable triplet energy gaps. These compounds possess several novel properties: (1) they emit in the blue region with high quantum yields; (2) they have high morphological stability and thermal stability; (3) they are capable of ambipolar carrier transport; (4) they possess tunable triplet energy gaps, suitable as hosts for yellow-orange to green phosphors. The electron and hole mobilities of these compounds lie in the range of 0.68–144 × 10−6 and 0.34–147 × 10−6 cm2 V−1 s−1, respectively. High-performance, single-layer, blue-emitting, fluorescent organic light-emitting diodes (OLEDs) are achieved with these ambipolar materials. High-performance, single-layer, phosphorescent OLEDs with yellow-orange to green emission are also been demonstrated using these ambipolar materials, which have different triplet energy gaps as the host for yellow-orange-emitting to green-emitting iridium complexes. When these ambipolar, blue-emitting materials are lightly doped with a yellow-orange-emitting iridium complex, white organic light-emitting diodes (WOLEDs) can be achieved, as well by the use of the incomplete energy transfer between the host and the dopant.
    Advanced Functional Materials 01/2009; 19(16). · 10.44 Impact Factor
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    ABSTRACT: A series of electroluminescent copolymers containing fluorene-2,8-disubstituted dibenzothiophene (PFD), fluorene-2,8-disubstituted dibenzothiophene-S,S-dioxide (PFDo) and phosphorescent benzimidazole-based iridium (Ir) complexes in the backbones were synthesized by the Suzuki coupling reaction. The thermal stabilities, HOMO/LUMO levels and triplet energy gap (ET) values were enhanced with increasing contents of dibenzothiophene (D) or dibenzothiophene-S,S-dioxide (Do) segments in the copolymers. The relative intensities of phosphorescence and fluorescence were affected by the energy transfer and back transfer efficiencies between the polymer backbones and iridium units as evidenced by solid state PL and EL spectra. PLED devices with a configuration of ITO/PEDOT:PSS (50nm)/metal-free copolymers (P1–P5), Ir-copolymers (P7–P13) and Ir-doped copolymers (P3 doped with Ir-complexes 6 and 8) (60–80nm)/TPBI (40nm)/LiF (1nm)/Al (120nm) were fabricated, and the electroluminescence (EL) efficiencies depended on the chemical constituents and triplet energies of the copolymers. The space-charge-limited current (SCLC) flow technique was used to measure the charge carrier mobilities of these copolymers, where both hole and electron mobilities were in the following order: the metal-free copolymers (P2, P3 and P5)>Ir-doped copolymers (P3+3 or 10mol% Ir-complex 6)>Ir-copolymers (P7, P8, P12 and P13).
    Polymer. 01/2009; 50(25):5945-5958.
  • Angewandte Chemie International Edition 02/2008; 47(3):581-5. · 11.34 Impact Factor
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    Wei-Sheng Huang, Jiann T. Lin, Hong-Cheu Lin
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    ABSTRACT: A series of novel non-conjugated functionalized benzoimidazole-based dendrimers containing peripheral benzyl ether type dendrons have been synthesized and characterized. These compounds undergo cyclometalation with iridium trichloride to form iridium(III) complexes. The emission wavelengths of these dendrimers are in the range from 510 to 530 nm, and the photoluminescence quantum yields (PLQYs) in the range from 0.45 to 0.80. Dendrimers (Gn)2Ir(acac) and (Gn)3Ir exhibit a reversible one-electron oxidation wave at ∼0.55 V and ∼0.37 V (vs. Ag/AgNO3), respectively. With a device configuration of indium tin oxide/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid)/4,4′-bis(N-carbarzolyl)biphenyl:(G2)3Ir 20 wt% dopant/1,3,5-tris(2-N-phenyl-benzoimidazolyl)benzene/LiF/Al has a maximum external quantum efficiency (EQE) of 17.6% and a maximum current efficiency of 61.5 cd/A.
    Organic Electronics 01/2008; · 3.84 Impact Factor