Publications (37)109.76 Total impact
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Article: A new class of cyclometalated ruthenium sensitizers of the type ĈNN for efficient dye-sensitized solar cells.
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ABSTRACT: A new class of cyclometalated ruthenium sensitizers incorporating a ĈNN ligand and conjugated 2,2'-bipyridine in the ancillary ligand have been designed and synthesized. The photovoltaic performance of JK-206 using an electrolyte containing 0.6 M 1,2-dimethyl-3-propylimidazolium iodide, 0.05 M I(2), 0.1 M LiI, and 0.5 M tert-butylpyridine in CH(3)CN gave a short-circuit photocurrent density of 19.63 mA cm(-2), an open-circuit voltage of 0.74 V, and a fill factor of 0.72, affording an overall conversion efficiency of 10.39%. The efficiency is the highest one reported for dye-sensitized solar cells based on the cyclometalated ruthenium sensitizer of the type ĈNN. Moreover, the same device using a polymer gel electrolyte exhibited a remarkable stability under 1000 h of light soaking at 60 °C, retaining 91% of the initial efficiency of 7.14%.Inorganic Chemistry 11/2011; 50(22):11340-7. · 4.60 Impact Factor -
Article: Successful demonstration of an efficient I(-)/(SeCN)2 redox mediator for dye-sensitized solar cells.
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ABSTRACT: A new I(-)/(SeCN)(2) redox mediator has favorable properties for dye-sensitized solar cells (DSCs) such as less visible light absorption, higher ionic conductivity, and downward shift of redox potential than I(-)/I(3)(-). It was then applied for DSCs towards increasing energy conversion efficiency, giving a new potential for improving performance.Physical Chemistry Chemical Physics 11/2011; 14(2):469-72. · 3.57 Impact Factor -
Article: New efficient ruthenium sensitizers with unsymmetrical indeno[1,2-b]thiophene or a fused dithiophene ligand for dye-sensitized solar cells.
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ABSTRACT: Two novel ruthenium sensitizers containing unsymmetrical indeno[1,2-b]thiophene or a fused dithiophene unit in the ancillary ligand have been designed and synthesized. The photovoltaic performance of JK-188 using an electrolyte consisting of 0.6 M 1,2-dimethyl-3-propylimidazolium iodide, 0.05 M I(2), 0.1 M LiI, 0.05 M guanidinium thiocyanate, and 0.5 M tert-butylpyridine in acetonitrile revealed a short-circuit photocurrent density of 18.60 mA/cm(2), an open-circuit voltage of 0.72 V, and a fill factor of 0.71, yielding an overall conversion efficiency of 9.54%. The cell exhibits a remarkable stability under 1000 h of light soaking at 60 °C using a quasi-solid-state electrolyte consisting of 5 wt % poly(vinylidenefluoride-co-hexafluoropropylene), 0.6 M 1-propyl-2,3-dimethylimidazolium iodide, 0.5 M N-methylbenzimidazole, and 0.1 M I(2) in 3-methoxypropionitrile, retaining 97% of the initial efficiency (7.38%).Inorganic Chemistry 09/2010; 49(18):8351-7. · 4.60 Impact Factor -
Article: Molecular Engineering of Efficient Organic Sensitizers Incorporating a Binary π-Conjugated Linker Unit for Dye-Sensitized Solar Cells
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ABSTRACT: Six organic sensitizers containing 3,4-ethylenedioxythiophene and thienothiophene in the bridged group are designed and synthesized, which under standard global AM 1.5 solar conditions, the device using JK-184 gave a conversion efficiency of 8.70%. The photovoltaic performance data are quite sensitive to the structural modification of sensitizer. The hexyl substituent of the hexyloxy group on the sensitizer was shown to improve the efficiency and stability. The device based on the JK-184 with an ionic liguid electolyte exhibits an excellent stability after 1000 h of light soaking at 60 °C.08/2010; -
Article: Novel Amphiphilic Ruthenium Sensitizer with Hydrophobic Thiophene or Thieno(3,2-b)thiophene-Substituted 2,2′-Dipyridylamine Ligands for Effective Nanocrystalline Dye Sensitized Solar Cells
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ABSTRACT: Hydrophobic conjugated 2,2′-dipyridylamine substituted amphiphilic ruthenium complexes {cis-Ru(dcbpy)(L)(NCS)2, where dcbpy is 4,4′-dicarboxylic acid-2,2′-bipyridine and L is 4,4′-di(5-hexylthiophen-2-yl)-2,2′-dipyridylamine, JK-85, or 4,4′-di[5-hexylthieno(3,2-b)thiophene]-2,2′-dipyridylamine, JK-86} were newly designed, synthesized, and successfully used as sensitizers for nanocrystalline dye sensitized solar cell using an electrolyte consisting of 0.6 M 1,2-dimethyl-3-propylimidazolium iodide (DMPII), 0.05 M I2, 0.1 M LiI, and 0.5 M tert-butylpyridine in acetonitrile. Under standard AM 1.5 sunlight, the complex JK-86 yielded a short-circuit photocurrent density of 18.3 mA/cm2, an open-circuit voltage of 0.68 V, and a fill factor of 0.72, corresponding to an overall conversion efficiency of 9.03%. Importantly, the cell exhibits an excellent stability, revealing almost no change after 1000 h of light soaking at 60 °C using a quasi-solid-state electrolyte composed of 0.1 M I2, 0.5 M NMBI (n-methyl-benzimidazole), 0.6 M DMPII (1-propyl-2,3-dimethylimidazolium iodide), and 5 wt % PVDF-HFP (poly(vinylidene fluoride-co-hexafluoropropylene)) in MPN (3-methoxypropionitrile).12/2009; -
Article: An efficient dye-sensitized solar cell with an organic sensitizer encapsulated in a cyclodextrin cavity.
Angewandte Chemie International Edition 02/2009; 48(32):5938-41. · 13.45 Impact Factor -
Article: Enhanced photovoltaic performance and long-term stability of quasi-solid-state dye-sensitized solar cells via molecular engineering.
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ABSTRACT: Organic dyes with long alkyl chains have been synthesized and demonstrated to be highly efficient sensitizers for liquid and quasi-solid-state solar cells, giving power conversion efficiencies of 8.31-8.39% and 7.03-7.31% under AM 1.5 G irradiation, respectively.Chemical Communications 11/2008; · 6.17 Impact Factor -
Article: Stepwise cosensitization of nanocrystalline TiO2 films utilizing Al2O3 layers in dye-sensitized solar cells.
Angewandte Chemie International Edition 10/2008; 47(43):8259-63. · 13.45 Impact Factor -
Article: Molecular engineering of organic sensitizers containing p-phenylene vinylene unit for dye-sensitized solar cells.
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ABSTRACT: Three organic sensitizers containing bis-dimethylfluorenyl amino donor and a cyanoacrylic acid acceptor bridged by p-phenylene vinylene unit were synthesized. The power conversion efficiency was quite sensitive to the length of bridged phenylene vinylene groups. A nanocrystalline TiO2 dye-sensitized solar cell was fabricated using three sensitizers. The maximum power conversion efficiency of JK-59 reached 7.02%.The Journal of Organic Chemistry 09/2008; 73(18):7072-9. · 4.45 Impact Factor -
Article: PEO electrolytes containing dioctyl phthalate (DOP) for dye-sensitized nanocrystalline TiO2 solar cells
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ABSTRACT: In this paper, we aim to prepare polymer electrolytes consisting of NaI and I2 dissolved in poly(ethylene oxide) (PEO) and dioctyl phthalate (DOP) as an additive and apply the electrolytes to dye-sensitized solar cells (DSSC). Upon the incorporation of salt, the phthalic-stretching C=O bands of DOP in Fourier transform infrared spectra shifted to a lower wave number (Δf = 93cm−1), confirming the unusual strong complex formation between sodium ions and phthalic oxygen. Coordinative interactions and structural changes of PEO/NaI/I2/DOP electrolytes have also been characterized by wide angle X-ray scattering, presenting an almost amorphous structure of the polymer electrolytes. The ionic conductivity of the polymer electrolytes reached ∼10–4S/cm at room temperature at the mole ratio of [EO]:[Na]:[DOP] = 10:1:0.5, as determined by the four-probe method. DSSC using the polymer electrolytes and conductive indium tin oxide glasses exhibited 2.9% of overall energy conversion efficiency (=P max/P in × 100) at one sun condition (100mW/cm2). The good interfacial contact between the electrolytes and the dye-attached nanocrystalline TiO2 layers were verified by field-emission scanning electron microscopy.Ionics 03/2008; 14(2):143-148. · 1.29 Impact Factor -
Article: Highly efficient and thermally stable organic sensitizers for solvent-free dye-sensitized solar cells.
Angewandte Chemie International Edition 02/2008; 47(2):327-30. · 13.45 Impact Factor -
Article: Nanocomposite polymer electrolytes containing silica nanoparticles: Comparison between poly(ethylene glycol) and poly(ethylene oxide) dimethyl ether
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ABSTRACT: Nanocomposite polymer electrolytes consisting of low molecular weight poly(ethylene oxide) (PEO), iodine salt MI (M = K+, imidazolium+), and fumed silica nanoparticles have been prepared and characterized. The effect of terminal group in PEO, i.e., hydroxyl (OH) and methyl (CH3) using poly(ethylene glycol) (PEG) and PEO dimethyl ether (PEODME), respectively, was investigated on the interactions, structures, and ionic conductivities of polymer electrolytes. Wide angle X-ray scattering (WAXS), differential scanning calorimetry (DSC), and complex viscositymeasurements clearly showed that the gelation of PEG electrolytes occurred more effectively than that of PEODME electrolytes. It was attributed to the fact that the hydroxyl groups of PEG participated in the hydrogen-bonding interaction between silica nanoparticles, and consequently helped to accelerate the gelation reaction, as confirmed by FTIR spectroscopy. Because of its interaction, the ionic conductivities of PEG electrolytes (maximum value ∼ 6.9 × 10−4 S/cm) were lower than that of PEODME electrolytes (2.3 × 10−3 S/cm). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007Journal of Applied Polymer Science 09/2007; 106(6):4083 - 4090. · 1.29 Impact Factor -
Article: Proton exchange membranes with high cell performance based on Nafion/poly (p-phenylene vinylene) composite polymer electrolyte
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ABSTRACT: Proton exchange membranes based on Nafion/poly(p-phenylene vinylene) (PPV) composites were prepared by the heat treatment of a Nafion/PPV precursor, and investigated regarding their applicability for direct methanol fuel cells (DMFCs). The power density of MEA using Nafion/PPV composites was increased with increasing the PPV precursor concentration of the precursor solutions and reached 34 mW/cm 2 , which is much greater than that using bare Nafion (∼26 mW/cm 2). The improved MEA performance was primarily due to a significant decrease in the methanol permeability with only a minimal loss of the ionic conductivity through the formation of PPV grains inside of the ionic channels and on the Nafion surface. The structure and properties of the Nafion/PPV composites were characterized by UV–vis spectroscopy, scanning electron microscopy, ion exchange capacity, water contact angle, and water uptake.Journal of Membrane Science 01/2007; 304:60-64. · 3.85 Impact Factor -
Article: Dye-sensitized solar cells based on crosslinked poly (ethylene glycol) electrolytes
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ABSTRACT: The high-energy conversion efficiency in solid-state dye-sensitized solar cells (SDSCs) has been achieved by both the better interfacial contact between solid polymer medium and dye molecules and the higher ionic conductivity of polymer electrolyte. Low molecular weight poly(ethylene glycol) (oligo-PEG, M w = 1000) has been used for the deeper penetration of electrolyte into nanoporous TiO 2 layer and consequently the better interfacial contact, followed by crosslinking terminal –OH groups of oligo-PEG with bifunctional glutaraldehyde. The ionic conductivity for the crosslinked oligo-PEG electrolytes is in the range of 10 −5 to 10 −3 S cm −1 at room temperature, which is high enough for solar cell applications and is presumably due to the increased intersegmental distance with an addition of the crosslinker as confirmed by WAXS analysis. The best result of the SDSCs is the short circuit current (J sc) of 9.48 mA cm −2 , the open circuit voltage (V oc) of 0.64 V, the fill factor (ff) of 0.60 and the overall energy conversion efficiency (η) of 3.64% at 100 mW cm −2 (AM 1.5).Journal of Photochemistry and Photobiology A: Chemistry. 01/2006; 183:15-21. -
Article: Roles of terminal groups of oligomer electrolytes in determining photovoltaic performances of dye-sensitized solar cells.
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ABSTRACT: The effect of terminal groups of oligomer electrolytes on the photovoltaic performance of dye-sensitized solar cells (DSSCs) have been systematically investigated to show that the terminal group plays a critical role in determining the concentration of I(3)(-), ionic conductivity, flatband potential and consequently the energy conversion efficiency.Chemical Communications 07/2005; · 6.17 Impact Factor -
Article: Dye-sensitized solar cells based on composite solid polymer electrolytes.
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ABSTRACT: The ionic conductivity of polymer electrolytes and their interfacial contact with dye-attached TiO2 particles were enhanced markedly by the addition of amorphous oligomer into polymer electrolytes, resulting in very high overall energy conversion efficiency.Chemical Communications 03/2005; · 6.17 Impact Factor -
Article: Dye-sensitized nanocrystalline solar cells based on composite polymer electrolytes containing fumed silica nanoparticles.
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ABSTRACT: We report remarkably high energy conversion efficiency (4.5% at 100 mW cm(-2)) of a dye-sensitized solar cell in the solid state, using composite polymer electrolytes containing fumed silica nanoparticles.Chemical Communications 08/2004; · 6.17 Impact Factor -
Article: Effects of inorganic substances on water splitting in ion-exchange membranes; I. Electrochemical characteristics of ion-exchange membranes coated with iron hydroxide/oxide and silica sol.
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ABSTRACT: The effects of inorganic substances on water splitting in ion-exchange membranes (IEMs) were investigated. In this study, iron hydroxide/ oxide and silica sol were immobilized on the surface of the IEMs. The water-splitting capabilities of the metal-embedded cation-exchange membranes were 10(4)-10(5) times greater than those of the virgin membranes at the same current density. Similarly, silica sol (i.e., triple bond Si-OH groups) deposited on the anion-exchange membrane surface also drastically increased the proton transport numbers. It was thought that the bipolar structure consisting of H- and OH-affinity groups immobilized on the IEM surface increased water-splitting due to the enhancement of water polarization with the help of strong electric fields. This study revealed that metal oxides or silica groups (triple bond Si-OH), as well as metal hydroxides, can be used as catalysts for water splitting.Journal of Colloid and Interface Science 06/2004; 273(2):523-32. · 3.07 Impact Factor -
Article: Effects of inorganic substances on water splitting in ion-exchange membranes; II. Optimal contents of inorganic substances in preparing bipolar membranes.
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ABSTRACT: An approach to enhancing the water-splitting performance of bipolar membranes (BPMs) is introducing an inorganic substance at the bipolar (BP) junction. In this study, the immobilization of inorganic matters (i.e., iron hydroxides and silicon compounds) at the BP junction and the optimum concentration have been investigated. To immobilize these inorganic matters, novel methods (i.e., electrodeposition of the iron hydroxide and processing of the sol-gel to introduce silicon groups at the BP junction) were suggested. At optimal concentrations, the immobilized inorganic matters significantly enhanced the water-splitting fluxes, indicating that they provide alternative paths for water dissociation, but on the other hand possibly reduce the polarization of water molecules between the sulfonic acid and quaternary ammonium groups at high contents. Consequently, the amount of inorganic substances introduced should be optimized to obtain the maximum water splitting in the BPM.Journal of Colloid and Interface Science 06/2004; 273(2):533-9. · 3.07 Impact Factor -
Article: Characterization of anion‐exchange membranes containing pyridinium groups
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ABSTRACT: A poly(vinyl chloride) (PVC)/glycidyl methacrylate (GMA)-divinyl benzene (DVB)-based membrane was prepared via monomer sorption, and then pyridium or its derivates (that is, 4-ethyl pyridium, 4-tetrabutyl pyridium) were introduced into the PVC/poly(GMA-DVB) base membrane. The effects of pyridinium anion-exchangeable sites on the water splitting and the electrochemical properties of the membrane were investigated. The electrochemical properties and the water splitting on the anion-exchange membranes were compared with selected commercial membranes containing quaternary ammonium groups. The pyridium membranes showed good electrochemical properties, comparable to those of the commercial membranes, with electrical resistances of less than 3.0 × 10−4 Ω·m2 in 0.5 mol dm−3 NaCl and high ionic permselectivities (the transport number of Cl− ions being 0.96). Moreover, water splitting indicated by the proton transport numbers of the membranes containing pyridinium or its derivates, were about two or three orders of magnitude lower than those of the commercial membranes (such as AM-1) at the same current density because the resonance effect in the quaternary pyridinium groups contributed to their molecular stability.AIChE Journal 04/2004; 49(12):3213 - 3220. · 2.26 Impact Factor
Top co-authors
Top Journals
Institutions
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2011
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Hanyang University
- Division of Chemical Engineering and Bioengineering
Ansan, Gyeonggi, South Korea
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2007
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Samsung Advanced Institute of Technology
Osan, Gyeonggi, South Korea
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2006
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Sejong University
Seoul, Seoul, South Korea
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2004–2005
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Korea Institute of Science and Technology
Seoul, Seoul, South Korea
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