• Title/Summary/Keyword: low bandgap polymer

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Electrical and Optical Properties of Newly Synthesised Low Bandgap Polymer with Protic and Aprotic Ionic Liquids (양자성, 비양자성 이온성 액체와 새롭게 합성된 낮은 밴드갭을 갖는 고분자와의 상호작용에 의한 전기적,광학적 특성 연구)

  • Kim, Joong-Il;Kim, In-Tae
    • Journal of the Korean Applied Science and Technology
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    • v.30 no.3
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    • pp.461-471
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    • 2013
  • Use of low bandgap polymers is the most suitable way to harvest a broader spectrum of solar radiations for solar cells. But, still there is lack of most efficient low bandgap polymer. In order to solve this problem, we have synthesised a new low bandgap polymer and investigated its interaction with the ILs to enhance its conductivity. ILs may undergo almost unlimited structural variations; these structural variations have attracted extensive attention in polymer studies. In addition to this, UV-Vis spectroscopy, confocal Raman spectroscopy and FT-IR spectroscopy results have revealed that all studied ILs (tributylmethylammonium methyl sulfate [$N_{1444}$][$MeSO_4$] from ammonium family) and 1-methylimidazolium chloride ([MIM]Cl, and 1-butyl-3-methylimidazolium chloride [Bmim]Cl from imidazolium family) has potential to interact with polymer. Further, protic ILs shows enhanced conductivity than aprotic ILs with low bandgap polymer. This study provides the combined effect of low bandgap polymer and ILs that may generate many theoretical and experimental opportunities.

High Molecular Weight Conjugated Polymer Thin Films with Enhanced Molecular Ordering, Obtained via a Dipping Method

  • Park, Yeong Don
    • Bulletin of the Korean Chemical Society
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    • v.34 no.11
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    • pp.3340-3344
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    • 2013
  • The fabrication of polymer field-effect transistors with good electrical properties requires the minimization of molecular defects caused by low molecular weight (MW) fractions of a conjugated polymer. Here we report that the electrical properties of a narrow bandgap conjugated polymer could be dramatically improved as a result of dipping a thin film into a poor solvent. The dipping time in hexanes was controlled to efficiently eliminate the low molecular weight fractions and concomitantly improve the molecular ordering of the conjugated polymer. The correlation between the structural order and the electrical properties was used to optimize the dipping time and investigate the effects of the low MW fraction on the electrical properties of the resulting thin film.

Interaction of Conjugated Conducting Polymer with Ionic Liquids (공액 전도성 고분자와 이온성 액체 간에 상호작용 연구)

  • Kim, Joong-Il;Kim, Do-Young;Kim, In-Tae
    • Journal of the Korean Applied Science and Technology
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    • v.31 no.3
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    • pp.337-344
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    • 2014
  • In this paper, we have examined the interaction of low bandgap polymer {poly(2-heptadecyl-4-vinylthieno[3,4-d]thiazole)(PHVTT)} with ionic liquids. Further, we have studied the temperature dependent interactions between the ionic liquids [tri-butyl methyl ammonium methyl sulfate ([TBMA][$MeSO_4$]), methyl imidazolium chloride ([MIM]Cl) and butyl methyl imidazolium chloride ([BMIM]Cl)] and polymer using UV-vis spectroscopy, FT-IR spectroscopy, photoluminescence (PL) spectroscopy, as a function of temperature at 21, 28, 32, $37^{\circ}C$. These experimental results suggest that interactions of polymer with ionic liquids ([MIM]Cl, [TBMA][$MeSO_4$]) showed weak interactions by increasing temperature but [BMIM]Cl has no significant effect with increase in temperature.

Nano imprinting lithography fabrication for photonic crystal waveguides (나노 임프린트 공정에 의한 광자결정 도파로 제조공정)

  • Jung Une-Teak;Kim Chang-Soek;Jeong Myung-Yung
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2005.10a
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    • pp.498-501
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    • 2005
  • Photonic crystals, periodic structure with a high refractive index contrast modulation, have recently become very interesting platform for manipulation of light. The existence of a photonic bandgap, a frequency range in which propagation of light is prevented in all direction, makes photonic crystal very useful in application where spatial localization of light is required for waveguide, beam splitter, and cavity. But fabrication of 3 dimensional photonic crystal is still difficult process. a concept that has recently attracted a lot of attention is a planar photonic crystal based on a dielectric membrane, suspended in the air, and perforated with 2 dimensional lattice of hole. We show that the polymer slabs suspended in air with triangular lattice of air hole can exhibit the in-plane photonic bandgap for TE-like modes. The fabrication of Si master with pillar structure using hot embossing process was investigated for 2 dimensional low-index-contrast photonic crystal waveguide.

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Nano stamp fabrication for photonic crystal waveguides (나노 광소자용 나노스탬프 제조공정 연구)

  • Jeong, Myung-Yung;Jung, Une-Teak;Kim, Chang-Seok
    • Journal of the Korean Society for Precision Engineering
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    • v.22 no.12 s.177
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    • pp.16-21
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    • 2005
  • Photonic crystals, periodic structure with a high refractive index contrast modulation, have recently become very interesting platform for the manipulation of light. The existence of a photonic bandgap, a frequency range in which the propagation of light is prevented in all directions, makes photonic crystal very useful in application where the spatial localization of light is required, for example waveguide, beam splitter, and cavity. However, the fabrication of 3 dimensional photonic crystals is still difficult process. A concept that has recently attracted a lot of attention is a planar photonic crystal based on a dielectric membrane, suspended in the air and perforated with two dimensional lattice of hole. The fabrication of Si master with pillar structure using hot embossing process is investigated for two dimensional, low-index-contrast photonic crystal waveguide. From our research we show that the multiple stamp copy process proved to be feasible and useful.

Synthesis and Characterization of Quinoxaline-Based Thiophene Copolymers as Photoactive Layers in Organic Photovoltaic Cells

  • Choi, Yoon-Suk;Lee, Woo-Hyung;Kim, Jae-Ryoung;Lee, Sang-Kyu;Shin, Won-Suk;Moon, Sang-Jin;Park, Jong-Wook;Kang, In-Nam
    • Bulletin of the Korean Chemical Society
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    • v.32 no.2
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    • pp.417-423
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    • 2011
  • A series of new quinoxaline-based thiophene copolymers (PQx2T, PQx4T, and PQx6T) was synthesized via Yamamoto and Stille coupling reactions. The $M_ws$ of PQx2T, PQx4T, and PQx6T were found to be 20,000, 12,000, and 29,000, with polydispersity indices of 2.0, 1.2, and 1.1, respectively. The UV-visible absorption spectra of the polymers showed two distinct absorption peaks in the ranges 350 - 460 nm and 560 - 600 nm, which arose from the ${\pi}-{\pi}^*$ transition of oligothiophene units and intramolecular charge transfer (ICT) between a quinoxaline acceptor and thiophene donor. The HOMO levels of the polymer ranged from -5.37 to -5.17 eV and the LUMO levels ranged from -3.67 to -3.45 eV. The electrochemical bandgaps of PQx2T, PQx4T, and PQx6T were 1.70, 1.71, and 1.72 eV, respectively, thus yielding low bandgap behavior. PQx2T, PQx4T, and PQx6T had open circuit voltages of 0.58, 0.42, and 0.47 V, and short circuit current densities of 2.9, 5.29 and 9.05 mA/$cm^2$, respectively, when $PC_{71}BM$ was used as an acceptor. For the solar cells with PQx2T-PQx6T:$PC_{71}BM$ (1:3) blends, an increase in performance was observed in going from PQx2T to PQx6T. The power conversion efficiencies of PQx2T, PQx4T, and PQx6T devices were found to be 0.69%, 0.73%, and 1.80% under AM 1.5 G (100 mW/$cm^2$) illumination.