Cham Kim

Cham Kim
Daegu Gyeongbuk Institute of Science and Technology | DGIST · Green Energy Research Division

Dr.

About

46
Publications
3,012
Reads
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793
Citations
Introduction
- Various inorganic-organic materials for alternative energy sources (Thermoelectric materials, Lithium ion battery electrodes, etc.)
Additional affiliations
September 2015 - September 2016
The University of Arizona
Position
  • Professor
September 2009 - August 2012
Pohang University of Science and Technology
Position
  • PhD
February 2006 - present
Daegu Gyeongbuk Institute of Science and Technology
Position
  • Senior Researcher

Publications

Publications (46)
Article
An inorganic/organic composite is suggested for low-temperature thermoelectric applications. An abundant and inexpensive conducting polymer, Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), is introduced to n-type Bi 2 Te 3 , thus affording a bulk-phase composite, in which interfacial...
Article
Full-text available
We provided a method to hybridize Bi2Te3 with polypyrrole, thus forming an inorganic/organic bulk composite (Bi2Te3–polypyrrole), in which the effects of energy band junction and phonon scattering were expected to occur at the interface of the two components. Bi2Te3–polypyrrole exhibited a considerably high Seebeck coefficient compared to pristine...
Article
The crystal alignment technology of lithium nickel manganese oxide (LiNi0.5Mn0.3Co0.2O2) is proposed using its magnetic properties. The crystalline LiNi0.5Mn0.3Co0.2O2 exhibits the paramagnetic behavior at room temperature as well as the magnetic anisotropy originated from its crystallographic anisotropy. If the crystalline LiNi0.5Mn0.3Co0.2O2 is e...
Article
We studied technology that enables the crystal alignment of LiNi0.5Mn0.3Co0.2O2 using its magnetic properties. LiNi0.5Mn0.3Co0.2O2 exhibited either antiferromagnetic or paramagnetic behavior depending on temperature as well as magnetic anisotropy originated from its crystallographic anisotropy. Based on these magnetic characteristics, we adjusted t...
Article
Full-text available
We suggest a way to control the crystal orientation of LiFePO4 using a magnetic field to obtain an advantageous structure for lithium ion conduction. We examined the magnetic properties of LiFePO4 such as magnetism and magnetic susceptibility, which are closely related to the crystal rotation in an external magnetic field, and considered how to use...
Article
We suggested a defect system consisting of Te- and Ag-related defects in n-type Bi2(Te,Se)3. We prepared the Terich Bi2Te2.88Se0.15 compound, which is expected to have Te antisite defects, via a conventional pulverization process. We devised a one-pot chemical process in which Ag nanoparticles were synthesized and instantly deposited onto the Bi2Te...
Article
Enhancement in thermoelectric performance of n-type Bi2(Te,Se)3 was accomplished by forming the dual defect system composed of Te- and Ag-related defects. The Te-rich Bi2(Te,Se)3+y, which should have antisite defects generated by the excessive Te, was prepared via a conventional melting process. We devised the one-pot process, in which Ag nanoparti...
Article
We provided a Bi2Te3-polypyrrole hybrid material, in which energy band junction and phonon scattering effects should appear at the interface of the two components. The hybrid material exhibited increases in electrical resistivity and the Seebeck coefficient due the energy band junction, thus retaining the power factor without loss, whereas showing...
Article
We hybridized n-type Bi2Te3 with an inexpensive and abundantly available conducting polymer, polypyrrole, to obtain a bulk-structured hybrid material in which the interfacial energy band and the phonon scattering effects should occur at the interface of the two components. The obtained hybrid material inevitably exhibited a lower electrical conduct...
Article
We report significant enhancement in thermoelectric performance of n-type Bi-2(Te,Se)(3) prepared via conventional melting process. We deposited chemically synthesized Ag nanoparticles onto Te-rich Bi-2(Te,Se)(3) and sintered the resulting substance to obtain a bulk product. The Ag nanoparticles and excessive Te elements should be converted to inte...
Article
A polycrystalline WSe2 nanocompound was produced via a brief thermal reaction between the atomic elements. It should grow along the in-plane direction with covalent bonds rather than along the through-plane direction with van der Waals forces, leading to both crystallographic and morphological anisotropies. Not only the anisotropies should structur...
Article
We studied a polycrystalline p-type WSe2 semiconductor for thermoelectric applications. The polycrystalline WSe2 nanocompound was prepared via a thermal reaction process of tungsten and selenium elements and it was sintered to produce a bulk structure using spark plasma sintering equipment. The resulting bulk specimen showed different morphological...
Article
Chemical reaction processes for thermoelectric nanomaterials have received a lot of attention because of subsequent small and uniform nanostructures, causing a remarkable reduction in thermal conductivity; however, they typically showed low electrical properties possibly due to contaminations by chemicals resulting in low ZT. We devised a new chemi...
Article
Various chemical reaction processes have been adopted to synthesize Bi2Te3 thermoelectric nanomaterials for achieving remarkably low thermal conductivities, but chemical contaminations were usually pointed out as flaws, severely deteriorating electrical conductivities. We devised a novel water-based chemical reaction process for a Bi2Te2.7Se0.3 nan...
Article
A phenyl compound with electron withdrawing substituents, 3-fluoro-4-cyanophenol (FCP), was used as an additive in polymer solar cells with a P3HT [poly(3-hexyl thiophene)]:PCBM [[6,6]-phenyl-C61-butyric acid methyl ester] blend film. Under simulated solar illumination of AM 1.5 (100 mW/cm2), the devices fabricated using a P3HT:PCBM (1:0.9 w:w) lay...
Article
We synthesized ternary n-type bismuth tellurium selenide nanomaterials for thermoelectric applications via a water-based chemical reaction under an atmospheric environment. In this work, bismuth nitrate was employed as a bismuth precursor and was hydrolyzed to form bismuth hydroxide in an aqueous solution. Ascorbic acid was used to dissolve the bis...
Article
A tellurium evaporation annealing method has been investigated to control the carrier concentration of sintered (Bi,Sb)2Te3 compounds. Hot-pressed (Bi,Sb)2Te3 bulk alloys and tellurium powders located in an evacuated ampoule, were heated to 673 K and held for 3, 12 and 48 h. The crystal structure and chemical composition in the annealed specimens w...
Article
A solution-based process was developed for the preparation of a CuInTe2 material that can be used as an absorber in thin-film photovoltaics. We performed a solvothermal synthesis under specific processing conditions to generate the CuInTe2 material. The resulting product showed different diffraction patterns and morphology depending on the reaction...
Article
We report on the effects of surface-modified TiO2 on the performance of dye-sensitized solar cells (DSSCs). TiO2 surface was modified with Na2CO3 via a simple dip coating process and the modified TiO2 was applied to photoelectrodes of DSSCs. By dipping of TiO2 layer into aqueous Na2CO3 solution, the DSSC showed a power conversion efficiency of 9.98...
Article
Single crystalline Bi-Te thermoelectric materials have a rhombohedral structure with van der Waals bonding along c-axis direction. This structure gives intrinsic anisotropy in thermoelectric properties like electrical resistivity, thermal conductivity, Seebeck coefficient, as well as electron/hall mobility. Recent research works report that nano st...
Article
A binary BiTe nanocompound for thermoelectric applications was prepared via a water-based chemical reaction under atmospheric conditions. We attempted to increase the carrier mobility of the nanocompound by adopting a post-thermal treatment consisting of calcination and reduction at different temperatures. We also tried to control the carrier densi...
Article
The synthesized n-type perylene derivative, N,N'-bis-(4-bromophenyl)-1,6,7,12-tetrakis(4-n-butoxy-phenoxy)-3,4,9,10-perylene tetracarboxdiimide (PIBr), was applied as an additive to polymer solar cells (PSCs) with P3HT [poly(3-hexylthiophene)]:PCBM [[6,6]-phenyl C61-butyric acid methyl ester] blend films. Without post thermal annealing, a considera...
Article
An ultrathin lithium fluoride (LiF) buffer layer was applied to inverted polymer solar cells with P3HT [poly(3-hexylthiophene)]:PCBM [[6,6]-phenyl C61-butyric acid methyl ester] blend films. By inserting the LiF layer between the transparent electrode and the P3HT:PCBM blend film, all parameters, including the short-circuit current, the open-circui...
Article
We investigated the thermoelectric properties of sintered Bi0.5Sb1.5Te3 alloys containing grains for their alignment, sizes and shapes. The figure of merit can be improved as the result of lower resistivity by increasing the alignment, which is realized by using the spark plasma sintering method and a strong magnetic field. In addition, making the...
Article
Bismuth telluride nanoparticles for thermoelectric applications were successfully prepared via a water-based chemical reaction. In this process, we used both a complexing agent (ethylenediaminetetraacetic acid) and a reducing agent (ascorbic acid) to stabilize the bismuth precursor (Bi(NO3)3) in water and to favor the reaction with the reduced sour...
Article
A bismuth tellurium selenide (Bi2TeySe3−y) nanocompound for thermoelectric applications was successfully prepared via a water-based chemical reaction in an atmospheric environment. The compound was less that ca. 100nm in size, with a crystalline structure corresponding to the rhombohedral Bi2Te2.7Se0.3. We sintered the compound via a spark plasma s...
Article
We simultaneously investigated the effects of nanostructure and crystal alignment on the thermoelectric performance of polycrystalline Bi0.5Sb1.5Te3. An appropriate experimental procedure was devised for a sequential process of slip-casting under a 6T magnetic field for c-axis alignment and the use of a spark plasma sinter machine for sintering. Fl...
Article
With a view to experimental demonstration for an improved thermoelectric performance, a slip casting method under high magnetic field for uni-directionally aligned crystals has been investigated. The sintered body of Bi2Te3 powder, its size between 300 and 500nm, green-bodied under 6T magnetic field showed a 33% variation in the fraction of the dir...
Article
Bismuth tellurium selenide (Bi2TeySe3−y) nanoparticles for thermoelectric applications are successfully prepared via a water-based chemical reaction under atmospheric conditions. The nanostructured compound is prepared using a complexing agent (ethylenediaminetetraacetic acid) and a reducing agent (ascorbic acid) to stabilize the bismuth precursor...
Article
Antimony telluride (Sb2Te3) nanoparticles for thermoelectric applications were successfully prepared via a water-based chemical reaction under atmospheric conditions. In this process, we tried to prepare the nanostructured compound by employing both a complexing agent (l-tartaric acid) and a reducing agent (NaBH4) to stabilize the Sb precursor (SbC...
Article
The influence of the starting powders’ morphology on the thermoelectric anisotropy of Bi–Te-based thermoelectric materials that are fabricated by spark plasma sintering has been investigated. Starting powders with three types of morphologies are prepared through a chemical reaction method (nano-sized particles with a spherical shape), a conventiona...
Article
This work reports on the preparation of Mg salts [MS; MgCO3 and Mg(CH3COO)2]-modified TiO2 electrodes by very simple dip coating and effects on the photovoltaic properties of dye-sensitized solar cells (DSSCs) with them. The DSSC with MS-modified TiO2 layer showed an increase in short-circuit current (Jsc) and open-circuit voltage (Voc), resulting...
Article
This work reports on the preparation of modified TiO2 electrodes, which could be applied to the photoanodes of dye-sensitized solar cells (DSSCs). TiO2 layers were formed on fluorine-doped tin oxide glasses via doctor-blade method followed by heat treatment. Then, the various metal hydroxides were individually incorporated onto the TiO2 layers via...
Article
Three n-type polymers, Ppe01, Ppe02, andPpe03, containing both perylene moieties and fluorine atoms were synthesized. The synthesiszed polymeric perylene derivatives with good compatibility for solution processes were chosen as new acceptor candidates for substitution of C60 derivatives in poly(3-hexylthiophene)-based organic photovoltaic applicati...
Article
This work reports on the preparation of modified TiO2 electrodes, which could be applied to the photoanodes in a dye-sensitized solar cells (DSSCs). TiO2 layer was formed on a FTO (fluorine-doped tin oxide) coated glass via doctor-blade method and post heat treatment. Then, the various metal hydroxides and metal oxides were selectively deposited on...
Article
Three emitting materials containing a biphenyl core connected at both ends with phenoxazine or anthracene groups, 10-(3-(10H-phenoxazin-10-yl)-6-phenylphenanthridin-8-yl)-10H-phenoxazine (DPoPP), 8-(anthracen-10-yl)-3-(anthracen-9-yl)-6-phenylphenanthridine (DAnPP), and 2-(anthracen-10-yl)-7-(anthracen-9-yl)-4,5,9,10-tetrahydropyrene (DAnTP) were s...
Article
Two materials containing carbazole moieties and exhibiting a high band gap energy, 3,8-di(9H-carbazol-9-yl)-6-phenylphenanthridine (DCzP) and 3,6-di(naphthalene-2-yl)-9-phenyl-9H-carbazole (DNaC), were synthesized via CN coupling and Suzuki coupling reactions, respectively. The compound DCzP exhibited blue emission with the CIE coordinates of x=0.1...
Article
In this study, we developed an immobilized TiO2 semiconductor on an ITO glass substrate (TiO2/ITO) and investigated its photocatalytic and electrochemical performance. The TiO2/ITO samples were prepared via a spin-coating process followed by calcination and were used for the photocatalytic or electrochemical degradation of an organic dye pollutant....
Article
Two materials, DNCz and TCzPB, which contain carbazole moieties and exhibit high band gap energies, were synthesized via CN coupling and Suzuki coupling reactions, respectively. The ionization potential and electron affinity of the synthesized TCzPB were measured at 5.89 and 2.39eV, respectively, implying that it is suitable for a host material. A...
Article
Three different cyclic amine dyes, 9-(2-chlorophenyl)-9H-carbazole (CPCz; C18H12ClN), 10-(2-chlorophenyl)-10H-phenoxazine (CPPo; C18H12ClNO), and 10-(2-chlorophenyl)-10H-phenothiazine (CPPt; C18H12ClNS), were synthesized to systematically investigate their optical properties and electronic band structures with molecular microstructure. By the inser...
Article
This work reports on the preparation of Cr-doped TiO2 (Cr–TiO2) and its utilization in the photoanode of a dye-sensitized solar cell (DSSC). Pure TiO2 and 10% Cr–TiO2 sols were individually obtained via hydrolysis followed by a hydrothermal process at 250 °C for 12 h. The TiO2 sol was first coated on a fluorine-doped tin oxide (FTO) substrate using...
Article
We have developed photocatalytic TiO2 nanofibers for the treatment of organic pollutants by using electrospinning method. We found that the optimized electrospinning conditions (electric field and flow rate) were 0.9 kV cm(-1) and 50 microL min(-1). After annealing at 550 degrees C for 30 min, we fabricated TiO2 nanofibers (average 236 nm thick) wi...
Article
This work reports the development of a visible-light sensible photocatalyst and the photocatalytic degradation of organic pollutants under visible-light irradiation. A composite semiconductor of ZnS and ZnO was prepared through co-precipitation process of Zn(NO3)2 in the mixed solution of aqueous Na2S and NaOH followed by calcination at 400°C in N2...
Article
In the anodes of direct methanol fuel cells (DMFCs), Pt poisoning by CO adsorption during methanol electro-oxidation has been a serious problem. Efforts to overcome or minimize this obstacle have largely involved investigations of PtRu bimetallic catalysts. In order to prepare fine PtRu alloyed hydrosols, we used non-ionic surfactants including L12...

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Project (1)
Project
Bi2Te3-based low-dimensional or nanobulk structures for high thermoelectric performance