Browsing by Author "Liao, Yung-Ming"

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Fabrication of hybrid chromophoric amphiphile/silica nanocomposite-based light emitting devices with enhanced performance
(2007)
Yang, Chung-He
;
Bhongale, Chetan Jagdish
;
Liao, Yung-Ming
;
Hsu, Chain-Shu
;
應用化學系
Organic semiconductors show efficient electroluminescence which has led to their commercialization in light-emitting diodes (LEDs), however, they have been marred by the thorniest problem of solid-state quenching. Here, we report the synthesis and characterization of two fluorene-based blue amphiphile emitters containing triphenylamine or anthracene side groups and demonstrate formation of their hybrid meso-structured nanocomposites by sol - gel co-assembly with tetraethyl orthosilicate; and study the molecular interactions within the mesophases formed. The chromophore amphiphiles designed act as photonic active materials as well as structure-directing agents. The new blue luminescent fluorene-based amphiphile/silica co-assembled nanocomposite films have been successfully prepared with enhanced emission. Different kinds of light emitting devices based on these nanocomposites show efficiencies which are improved by several times compared with the corresponding pristine chromophore amphiphiles.
High birefringence lateral difluoro phenyl tolane liquid crystals
(2010)
Song, Qiong
;
Gauza, Sebastian
;
Xianyu, Haiqing
;
Wu, Shin Tson
;
Liao, Yung-Ming
Four laterally difluorinated phenyl tolane liquid crystals were synthesised and their physical properties evaluated. These compounds exhibit a fairly small heat fusion enthalpy (Delta H similar to 12.56 kJ mol(-1)), which is favourable for mixture formulations. For comparison, four lateral difluoro cyclohexane tolane homologues are also studied. We doped 10 wt% of each compound into a commercial negative mixture N1 and measured the birefringence, visco-elastic coefficient and figure of merit. Birefringence varies very little between homologues, but the visco-elastic coefficient increases as alkyl chain length increases. The refractive indices of these guest-host mixtures at 1550 nm are also measured.
High-performance poly(2,3-diphenyl-1,4-phenylene vinylene)-based polymer light-emitting diodes by blade coating method
(2011-08-03)
Liao, Yung-Ming
;
Shih, Hung-Min
;
Hsu, Kuang-Hui
;
Hsu, Chain-Shu
;
Chao, Yu-Chiang
A new series of super high brightness and luminance efficient poly(2,3-diphenyl-1,4-phenylene vinylene) (DP-PPV)-based electroluminescent (EL) polymers containing methoxy or long branched alkoxy chains were synthesized via Gilch polymerization. The branched alkoxy groups were introduced to enhance solubility for blade and spin-coating processes. Monomers of DMeO-PPV and m-Ph-PPV were used to increase steric hindrance and prevent close packing of the main chain. By controlling the feeding ratio of different monomers during polymerization, DP-PPV derivatives with high molecular weight were obtained. All synthesized polymers possess high glass transition temperatures and thermal stabilities. The maximum photoluminescent emissions of the thin films are located between 544 and 547 nm. Cyclic voltammetry analysis reveals that the band gaps of these light-emitting materials are in the range of 2.75 -2.84 eV. Blade coating was used to fabricate multilayer polymer light-emitting diodes. A multilayer electroluminescent device with the configuration of ITO/PEDOT:PSS/TFB/P1/TPBi/LiF/Al exhibited a very high luminescence efficiency (10.96 cd A(-1)). The maximum brightness of the multilayer EL device ITO/PEDOT:PSS/TFB/P3/CsF/Al reached up to 78,050 cd m(-2) with a low turn-on voltage (4.0 V). For further investigation, polymer P3 was blended with DPPFBNA to achieve white light-emitting device; the multilayer devices generated a maximum brightness of 1085 cd m(-2) and a luminance efficiency of 0.75 cd A(-1), with CIE coordinates (0.28, 0.33) at 11 V. (C) 2011 Elsevier Ltd. All rights reserved.
Induced Chain Alignment of Conjugated Polymers Within Nanoporous Template
(2011-07-22)
Lo, Kuan-Hsin
;
Ho, Rong-Ming
;
Liao, Yung-Ming
;
Hsu, Chain-Shu
;
Massuyeau, Florian
This work presents a simple method to generate ordered conjugated polymer nanoarrays through a pore-filling process for nanoporous polymer templates so as to enhance the efficiency of photoluminescence (PL). PL results combined with the morphological evolution examined by scanning probe microscopy revealed that the enhanced PL reaches maximum intensity as the template pores are completely filled by conjugated polymers. Polarized PL spectroscopy and grazing incidence Fourier transform infrared spectroscopy were used to determine the chain orientation of templated conjugated polymer; the spectroscopic results indicate a parallel chain orientation along the cylindrical direction of nanopores. The induced alignment of the polymer chains is attributed to a nanoscale spatial effect that increases the PL intensity and the lifetime of the conjugated polymer. The enhanced luminescence of nanostructured conjugated polymers is highly promising for use in designing luminescent nanodevices.
Synthesis and mesomorphic properties of fluoro and isothiocyanato biphenyl tolane liquid crystals
(2006)
Liao, Yung-Ming
;
Janarthanan, Narayanasamy
;
Hsu, Chain-Shu
;
Gauza, Sebastian
;
Wu, Shin-Tson
Four series of high birefringence biphenyl tolane liquid crystals having a terminal isothiocyanato or fluoro group were synthesized; their mesomorphic properties were studied by optical polarizing microscopy and DSC. These biphenyl tolane compounds exhibit reasonably low melting points and high birefringence of 0.37-0.49. By using these compounds a eutectic mixture was formulated exhibiting a wide nematic range, high figure-of-merit and low viscosity.
Synthesis and mesomorphic properties of super high birefringence isothiocyanato bistolane liquid crystals
(2007)
Liao, Yung-Ming
;
Chen, Hsin-Lan
;
Hsu, Chain-Shu
;
Gauza, Sebastian
;
Wu, Shin-Tson
Four series of high birefringence bistolane liquid crystals containing isothiocyanato termal groups were synthesized and characterized. As well as the phenyl group, both biphenyl and naphthyl moieties were introduced to enhance the birefringence. These bistolane compounds exhibit reasonably low melting points and high birefringence of 0.5-0.8. A eutectic mixture was formulated from these compounds exhibiting a wide nematic range, high figure-of-merit and low viscosity.
Synthesis of High Birefringence Liquid Crystals for Display Application
(2008)
Hsu, Chain-Shu
;
Liao, Yung-Ming
;
應用化學系
;
Department of Applied Chemistry
Four series of high birefringence bistolane liquid crystals were synthesized and characterized. Biphenyl and naphthyl moieties were introduced to enhance the birefringence. These bistolane compounds exhibit reasonably low melting points and high birefringence of 0.5-0.8.