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Sung Min Cho

Bio: Sung Min Cho is an academic researcher from Sungkyunkwan University. The author has contributed to research in topics: OLED & Thin film. The author has an hindex of 34, co-authored 150 publications receiving 4270 citations.
Topics: OLED, Thin film, PEDOT:PSS, Graphene, Electrode


Papers
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Journal ArticleDOI
TL;DR: In this article, a perovskite light absorber incorporating organic-inorganic hybrid cation in the A-site of 3D APbI3 structure with enhanced photo- and moisture stability is reported.
Abstract: Although power conversion efficiency (PCE) of state-of-the-art perovskite solar cells has already exceeded 20%, photo- and/or moisture instability of organolead halide perovskite have prevented further commercialization. In particular, the underlying weak interaction of organic cations with surrounding iodides due to eight equivalent orientations of the organic cation along the body diagonals in unit cell and chemically non-inertness of organic cation result in photo- and moisture instability of organometal halide perovskite. Here, a perovskite light absorber incorporating organic–inorganic hybrid cation in the A-site of 3D APbI3 structure with enhanced photo- and moisture stability is reported. A partial substitution of Cs+ for HC(NH2)2+ in HC(NH2)2PbI3 perovskite is found to substantially improve photo- and moisture stability along with photovoltaic performance. When 10% of HC(NH2)2+ is replaced by Cs+, photo- and moisture stability of perovskite film are significantly improved, which is attributed to the enhanced interaction between HC(NH2)2+ and iodide due to contraction of cubo-octahedral volume. Moreover, trap density is reduced by one order of magnitude upon incorporation of Cs+, which is responsible for the increased open-circuit voltage and fill factor, eventually leading to enhancement of average PCE from 14.9% to 16.5%.

1,307 citations

Journal ArticleDOI
TL;DR: In this paper, a facile means of fabricating graphene thin films via layer-by-layer assembly of charged graphene nanosheets (GS) based on electrostatic interactions is presented.
Abstract: In this study, we present a facile means of fabricating graphene thin films via layer-by-layer (LbL) assembly of charged graphene nanosheets (GS) based on electrostatic interactions. To this end, graphite oxide (GO) obtained from graphite powder using Hummers method is chemically reduced to carboxylic acid-functionalized GS and amine-functionalized GS to perform an alternate LbL deposition between oppositely charged GSs. Specifically, for successful preparation of positively charged GS, GOs are treated with an intermediate acyl-chlorination reaction by thionyl chloride and a subsequent amidation reaction in pyridine, whereby a stable GO dispersibility can be maintained within the polar reaction solvent. As a result, without the aid of additional hybridization with charged nanomaterials or polyelectrolytes, the oppositely charged graphene nanosheets can be electrostatically assembled to form graphene thin films in an aqueous environment, while obtaining controllability over film thickness and transparency....

168 citations

Journal ArticleDOI
TL;DR: A biosensor chip utilizing surface plasmon resonance (SPR) was fabricated for detecting anti-glutamic acid decarboxylase (GAD) antibody, which is an indicator of the presence of type I diabetes mellitus.

140 citations

Journal ArticleDOI
TL;DR: In this paper, Tungsten trioxide (WO3) films with a mesoporous morphology, high transparency, and monoclinic phase crystallinity were prepared using polyethyleneglycol (PEG) as a surfactant and their photoelectrochemical properties were measured.
Abstract: Tungsten trioxide (WO3) films with a mesoporous morphology, high transparency, and monoclinic phase crystallinity were prepared using polyethyleneglycol (PEG) as a surfactant and their photoelectrochemical properties were measured. By controlling the weight ratio of the tungsten precursor to PEG, a sphere-like WO3 nanoparticle film with high transparency can be synthesized. The photocurrent responses of the films under 1 sun solar light illumination were measured. Due to the high transparency of the WO3 photoanode, it is possible to fabricate a tandem cell composed of a WO3/Pt bipolar electrode connected with a dye-sensitized solar cell. Unassisted water splitting from the tandem cell was demonstrated but the maximum current density was exhibited at around +0.4 V (vs.Pt).

139 citations

Journal ArticleDOI
My Duyen Ho1, Daekyoung Kim1, Namhun Kim1, Sung Min Cho1, Heeyeop Chae1 
TL;DR: The electroluminescence performance of QD-LEDs was considerably improved by adding small molecules (TCTA or CBP) having high hole mobilily to the polymer hole transport material (PVK).
Abstract: The performance of quantum dot light-emitting diodes (QD-LEDs) was investigated for different hole transport layers with small molecules and polymers: poly(4-butyl-phenyl-diphenyl-amine), poly-N-vinylcarbazole (PVK), N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-diphenyl-4,4′-diamine, 4,4′,4″-tris(N-carbazolyl)-triphenyl-amine (TCTA), and 4,4′-bis(carbazole-9-yl)biphenyl (CBP). The electroluminescence performance of QD-LEDs was considerably improved by adding small molecules (TCTA or CBP) having high hole mobilily to the polymer hole transport material (PVK). The maximal current efficiency of QD-LED-based PVK was improved by 27% upon addition of 20 wt % TCTA due to the hole injection improvement. The lower turn-on voltage, the higher current density, and the higher luminance were achieved by addition of TCTA. The maximal luminance of 40900 cd/m2 and the highest current efficiency of 14.0 cd/A with the narrow full width at half-maximum (<35 nm) were achieved by the best hole transport layer.

116 citations


Cited by
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Journal ArticleDOI
TL;DR: In this paper, photo-induced superhydrophilicity was used on the surface of a wide-band gap semiconductor like titanium dioxide (TiO 2 ) for photocatalytic activity towards environmentally hazardous compounds.

4,241 citations

Journal ArticleDOI
TL;DR: This work presents a meta-analysis of the literature on food quality and safety analysis and its applications in the context of veterinary drugs and drugs and drug-Induced Antibodies, which focuses on the role of canine coronavirus in the veterinary industry.
Abstract: 5.1. Detection Formats 475 5.2. Food Quality and Safety Analysis 477 5.2.1. Pathogens 477 5.2.2. Toxins 479 5.2.3. Veterinary Drugs 479 5.2.4. Vitamins 480 5.2.5. Hormones 480 5.2.6. Diagnostic Antibodies 480 5.2.7. Allergens 481 5.2.8. Proteins 481 5.2.9. Chemical Contaminants 481 5.3. Medical Diagnostics 481 5.3.1. Cancer Markers 481 5.3.2. Antibodies against Viral Pathogens 482 5.3.3. Drugs and Drug-Induced Antibodies 483 5.3.4. Hormones 483 5.3.5. Allergy Markers 483 5.3.6. Heart Attack Markers 484 5.3.7. Other Molecular Biomarkers 484 5.4. Environmental Monitoring 484 5.4.1. Pesticides 484 5.4.2. 2,4,6-Trinitrotoluene (TNT) 485 5.4.3. Aromatic Hydrocarbons 485 5.4.4. Heavy Metals 485 5.4.5. Phenols 485 5.4.6. Polychlorinated Biphenyls 487 5.4.7. Dioxins 487 5.5. Summary 488 6. Conclusions 489 7. Abbreviations 489 8. Acknowledgment 489 9. References 489

3,698 citations

Journal ArticleDOI
TL;DR: In this paper, the triple cation perovskite photovoltaics with inorganic cesium were shown to be thermally more stable, contain less phase impurities and are less sensitive to processing conditions.
Abstract: Today's best perovskite solar cells use a mixture of formamidinium and methylammonium as the monovalent cations. With the addition of inorganic cesium, the resulting triple cation perovskite compositions are thermally more stable, contain less phase impurities and are less sensitive to processing conditions. This enables more reproducible device performances to reach a stabilized power output of 21.1% and ∼18% after 250 hours under operational conditions. These properties are key for the industrialization of perovskite photovoltaics.

3,470 citations

Journal ArticleDOI
14 Oct 2016-Science
TL;DR: This work shows that the small and oxidation-stable rubidium cation (Rb+) can be embedded into a “cation cascade” to create perovskite materials with excellent material properties and achieved stabilized efficiencies of up to 21.6% on small areas.
Abstract: All of the cations currently used in perovskite solar cells abide by the tolerance factor for incorporation into the lattice. We show that the small and oxidation-stable rubidium cation (Rb + ) can be embedded into a “cation cascade” to create perovskite materials with excellent material properties. We achieved stabilized efficiencies of up to 21.6% (average value, 20.2%) on small areas (and a stabilized 19.0% on a cell 0.5 square centimeters in area) as well as an electroluminescence of 3.8%. The open-circuit voltage of 1.24 volts at a band gap of 1.63 electron volts leads to a loss in potential of 0.39 volts, versus 0.4 volts for commercial silicon cells. Polymer-coated cells maintained 95% of their initial performance at 85°C for 500 hours under full illumination and maximum power point tracking.

3,034 citations

Journal ArticleDOI
08 Jan 2016-Science
TL;DR: It is shown that using cesium ions along with formamidinium cations in lead bromide–iodide cells improved thermal and photostability and lead to high efficiency in single and tandem cells.
Abstract: Metal halide perovskite photovoltaic cells could potentially boost the efficiency of commercial silicon photovoltaic modules from ∼20 toward 30% when used in tandem architectures. An optimum perovskite cell optical band gap of ~1.75 electron volts (eV) can be achieved by varying halide composition, but to date, such materials have had poor photostability and thermal stability. Here we present a highly crystalline and compositionally photostable material, [HC(NH2)2](0.83)Cs(0.17)Pb(I(0.6)Br(0.4))3, with an optical band gap of ~1.74 eV, and we fabricated perovskite cells that reached open-circuit voltages of 1.2 volts and power conversion efficiency of over 17% on small areas and 14.7% on 0.715 cm(2) cells. By combining these perovskite cells with a 19%-efficient silicon cell, we demonstrated the feasibility of achieving >25%-efficient four-terminal tandem cells.

2,412 citations