I-Hung Chiang

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

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Publications (5)20.88 Total impact

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    ABSTRACT: In this study, we synthesized two novel 1,3,4-oxadiazole-based bent-core liquid crystals (OXD7*, OXD5B7F*) containing a chiral tail that display broad ranges of the blue phase III (34 and 7 K, respectively); we characterized them using polarized optical microscopy, differential scanning calorimetry, and circular dichroism. The electro-optical responses of both of these liquid crystals are much faster than those of previously reported single-component blue-phase liquid crystals. To optimize its electro-optical performance, we mixed OXD7* (the blue-phase range of which is broader than that of OXD5B7F*) with its analogue OXD6 (at weight ratios of 6:4 and 4:6). We also performed molecular modeling of single-component BPLCs (OXD7* and OXD5B7F*) to analyze the possible parameters affecting their blue phase ranges.
    ACS Applied Materials & Interfaces 12/2013; · 5.90 Impact Factor
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    ABSTRACT: A series of π-conjugated bis-terpyridyl ligands (M1–M3) bearing various benzodiazole cores and their corresponding main-chain Ru(II) metallo-polymers were designed and synthesized. The formation of metallo-polymers were confirmed by NMR, relative viscosity, and UV-visibletitration measurements. The effects of electron donor and acceptor interactions on their thermal, optical, electrochemical, and photovoltaic properties were investigated. Due to the strong intramolecular charge transfer (ICT) interaction and metal to ligand charge transfer (MLCT) in Ru(II)-containing polymers, the absorption spectra covered a broad range of 260–750 nm with the optical band gaps of 1.77–1.63 eV. In addition, due to the broad sensitization areas of the metallo-polymers, their bulk heterojunction (BHJ) solar cell devices containing [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as an electron acceptor exhibited a high short-circuit current (Jsc). An optimum PVC device based on the blended polymerP1:PCBM = 1:1 (w/w) achieved the maximum power conversion efficiency (PCE) value up to 0.45%, with Voc = 0.61 V, Jsc = 2.18 mA cm−2, and FF = 34.1% (under AM 1.5 G 100 mW cm−2), which demonstrated a novel family of conjugated polyelectrolytes with the highest PCE value comparable with BHJ solar cells fabricated from ionic polythiophene and C60.
    Journal of Materials Chemistry 01/2011; 21(4):1196-1205. · 6.63 Impact Factor
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    ABSTRACT: Two kinds of novel conjugated polymers containing 2,7-carbazole, thiophene, and fused-dithienothiophene rings as backbones bearing acid-protected and benzoic acid pendants (PC1 and PC2, respectively) were utilized for organic solar cell applications. The absorption spectra of these polymers (in both solutions and solid films) showed an absorption range at 300–580nm. Furthermore, ZnO nanoparticles were synthesized and surface-modified with pyridyl surfactants (ZnOpy) to be ca. 3–4nm. The pyridyl surfactants of ZnOpy nanoparticles (as electron acceptors to partially replace expensive electron acceptor PCBM) not only induce supramolecular interactions with benzoic acid pendants of polymer PC2 via H-bonds, but also enhance the homogeneous dispersions of ZnOpy nanoparticles in polymer PC2. Thus, the ternary systems of PC1–PC2/ZnOpy/PCBM in weight ratios of 1:0.05:1 and 1:0.1:1 were investigated in bulk heterojunction polymer solar cells (PSCs). Under the standard illumination of AM 1.5, 100mW/cm2, the best power conversion efficiency (PCE) of the PSC cell containing a polymer blend of PC2/ZnOpy/PCBM=1:0.05:1 reached PCE=0.55%, with Jsc=2.11mA/cm2, Voc=0.88V, and FF=29.4%.
    Thin Solid Films 01/2011; 519(15):5212-5218. · 1.87 Impact Factor
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    ABSTRACT: Novel supramolecular side-chain polymers were constructed by complexation of proton acceptor (H-acceptor) polymers, i.e., side-chain conjugated polymers P1–P2 containing pyridyl pendants, with low-band-gap proton donor (H-donor) dyes S1–S4 (bearing terminal cyanoacrylic acids) in a proper molar ratio. Besides unique mesomorphic properties confirmed by DSC and XRD results, the H-bonds of supramolecular side-chain structures formed by pyridyl H-acceptors and cyanoacrylic acid H-donors were also confirmed by FTIR measurements. H-donor dyes S1–S4 in solid films exhibited broad absorption peaks located in the range of 471–490 nm with optical band-gaps of 1.99–2.14 eV. Furthermore, H-bonded polymer complexes P1/S1–P1/S4 and P2/S1–P2/S4 exhibited broad absorption peaks in the range of 440–462 nm with optical band-gaps of 2.11–2.25 eV. Under 100 mW/cm2 of AM 1.5 white-light illumination, the bulk heterojunction polymer solar cell (PSC) devices containing an active layer of H-bonded polymer complexes P1/S1–P1/S4 and P2/S1–P2/S4 (as electron donors) mixed with [6,6]-phenyl C61 butyric acid methyl ester (i.e., PCBM, as an electron acceptor) in the weight ratio of 1:1 were investigated. The PSC device containing H-bonded polymer complex P1/S3 mixed with PCBM (1:1 w/w) gave the best preliminary result with an overall power conversion efficiency (PCE) of 0.50%, a short-circuit current of 3.17 mA/cm2, an open-circuit voltage of 0.47 V, and a fill factor of 34%. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5998–6013, 2009
    Journal of Polymer Science Part A Polymer Chemistry 10/2009; 47(22):5998 - 6013. · 3.54 Impact Factor
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    ABSTRACT: Several series of novel banana-shaped H-bonded symmetric trimers (with two H-bonds) and asymmetric heterodimers (with one H-bond) were self-assembled by appropriate molar ratios of proton donors (H-donors) and acceptors (H-acceptors). The influences of H-bonded linking positions and aromatic ring numbers (4-8 aromatic rings in the rigid cores) as well as the chain lengths (n, m = 12 or 16, respectively, in the flexible parts) on the mesomorphism and the switching behavior of the bent-core supramolecules were evaluated and theoretically analyzed. Except for the supramolecular structures with longer rigid cores or shorter flexible chains possessing the rectangular columnar (Col(r) or B1) phase, the SmC(A)P(A) phase was revealed in most supramolecular asymmetric heterodimers and switched to the SmC(S)P(F) phase by applying electric fields. The polar smectic C phase was dominated for those with H-bonded sites apart from the core center. Interestingly, the SmA and nematic phases were observed in H-bonded asymmetric dimers with H-bonded sites close to the core center, which theoretically proved that the polar smectic C phase was disfavored due to an unfavorable bend angle (smaller than the lower limit of 110 degrees ) in the lowest-energy H-bonded conformer. Compared with the fully covalently bonded analogue, lower transition temperatures and lower threshold voltages were developed in the H-bonded asymmetric dimers with the polar smectic C phase. On the basis of the theoretical calculations of molecular modeling, the existence of polar switching behavior in the polar smectic C phase of asymmetric heterodimers was proven to be associated with their configurations with higher dipole moments and suitable bend angles. Furthermore, the lack of polar switching behavior in supramolecular symmetric trimers, which exhibited the regular SmC phase with weak electrical stabilities, was related to their configurations with smaller dipole moments and confirmed by theoretical calculations.
    The Journal of Physical Chemistry B 10/2009; 113(44):14648-60. · 3.61 Impact Factor