Byoung Hoon Lee

Gwangju Institute of Science and Technology, Gwangju, Gwangju, South Korea

Are you Byoung Hoon Lee?

Claim your profile

Publications (42)188 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Small-bandgap polymer solar cells (PSCs) with a thick bulk heterojunction film of 340 nm exhibit high power conversion efficiencies of 9.40% resulting from high short-circuit current density (JSC ) of 20.07 mA cm(-2) and fill factor of 0.70. This remarkable efficiency is attributed to maximized light absorption by the thick active layer and minimized recombination by the optimized lateral and vertical morphology through the processing additive. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    Advanced Materials 04/2015; DOI:10.1002/adma.201501132 · 15.41 Impact Factor
  • Advanced Energy Materials 11/2014; 5(5). DOI:10.1002/aenm.201401653 · 14.39 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Bronchiectasis and asthma are different in many respects, but some patients have both conditions. Studies assessing the effect of bronchiectasis on asthma exacerbation are rare. The aim of this study is to investigate the effect of bronchiectasis on asthma exacerbation. We enrolled 2,270 asthma patients who were followed up in our hospital. Fifty patients had bronchiectasis and asthma. We selected fifty age- and sex-matched controls from the 2,220 asthma patients without bronchiectasis, and assessed asthma exacerbation and its severity based on the annual incidence of total asthma exacerbation, annual prevalence of steroid use, and frequency of emergency room visits and hospitalizations due to asthma exacerbation in each group. Fifty patients (2.2%) had bronchiectasis and asthma. The annual incidence of asthma exacerbation was higher in patients with asthma and bronchiectasis than in patients with asthma alone (1.08±1.68 vs. 0.35±0.42, p=0.004). The annual prevalence of steroid use (0.9±1.54 vs. 0.26±0.36, p=0.006) and the frequency of emergency room visits (0.46±0.84 vs. 0.02±0.13, p=0.001) due to asthma exacerbation were also higher in patients with asthma and bronchiectasis than in patients with asthma alone. Bronchiectasis is associated with difficult asthma control.
    Tuberculosis and Respiratory Diseases 11/2014; 77(5):209-214. DOI:10.4046/trd.2014.77.5.209
  • Source
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To achieve the broad utilization of the full functionality of graphene (GR) in devices, a transfer method should be developed that can simplify the process without leaving residue of the insulating supporting layer on the surface of GR. Furthermore, stable GR doping without the use of an insulating polymer is required. Here, a new GR transfer method that uses a popular conducting polymer, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), is reported as a new supporting layer for the transfer of GR films that are synthesized by chemical vapor deposition. The GR/PEDOT:PSS bilayer can be directly utilized without the removal process. Therefore, this transfer method simplifies the transfer process and solves the residue problem of conventional transfer methods. The stable doping of GR films is simultaneously achieved by using the PEDOT:PSS layer. The new GR/PEDOT:PSS hybrid electrodes are fully functional in polymer solar cells and polymer light-emitting diodes, outperforming the conventionally transferred GR electrodes and indium tin oxide electrodes.
    Advanced Functional Materials 04/2014; 24(13). DOI:10.1002/adfm.201302928 · 10.44 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The crystalline nanostructure of intrinsically conducting polymers is formed via an all-solution process, leading to a highly conducting state. H2 SO4 post-treatment induces a significant structural rearrangement in PEDOT:PSS films, developing crystalline nanofibrils with a stoichiometrically optimal amount of PSS, and this dramatically increases conductivity up to σdc ≈ 4380 S cm(-1) . The highly conductive PEDOT:PSS exhibits potential as a transparent electrode in printable optoelectronic devices, as described by K. Lee, S. H. Lee, and co-workers on page 2268.
    Advanced Materials 04/2014; 26(14):2109. DOI:10.1002/adma.201470088 · 15.41 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Y. H. Kahng, K. Lee, and co‐workers demonstrate a high‐performance, flexible, and transparent electrode for organic optoelectronic devices based on graphene. On page 1847, a popular conducting polymer (PEDOT:PSS) is used as a supporting layer during graphene transfer and as a stable doping layer in the applied devices. High performance, reproducibility, and an enhanced lifetime are demonstrated with the developed electrode in various organic optoelectronic devices.
    Advanced Functional Materials 04/2014; 24(13). DOI:10.1002/adfm.201470086 · 10.44 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Crystalline PEDOT:PSS nanofibrils with an electrical conductivity of 4380 S cm(-1) are formed via a solution process using H2 SO4 . The concentrated H2 SO4 treatment induces a significant structural rearrangement of PEDOT:PSS via a charge-separated transition mechanism, resulting in highly ordered and densely packed PEDOT:PSS nanofibrils. The PEDOT:PSS electrode shows a sheet resistance of 46 Ω sq(-1) with 90% optical transmittance.
    Advanced Materials 04/2014; 26(14). DOI:10.1002/adma.201304611 · 15.41 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Despite the excellent work function adjustability of conjugated polyelectrolytes (CPEs), which induce a vacuum level shift via the formation of permanent dipoles at the CPE/metal electrode interface, the exact mechanism of electron injection through the CPE electron transport layer (ETL) remains unclear. In particular, understanding the ionic motion within the CPE ETLs when overcoming the sizable injection barrier is a significant challenge. Because the ionic functionality of CPEs is a key component for such functions, a rigorous analysis using highly controlled ion density (ID) in CPEs is crucial for understanding the underlying mechanism. Here, by introducing a new series of CPEs with various numbers of ionic functionalities, energy level tuning at such an interface can be determined directly by adjusting the ID in the CPEs. More importantly, these series CPEs indicate that two different mechanisms must be invoked according to the CPE thickness. The formation of permanent interfacial dipoles is critical with respect to electron injection through CPE ETL (≤ 10 nm, quantum mechanical tunneling limit), whereas electron injection through thick CPE ETL (20–30 nm) is dominated by the reorientation of the ionic side chains under a given electric field.
    Advanced Functional Materials 02/2014; 24(8). DOI:10.1002/adfm.201301810 · 10.44 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The correlation between the geometrical structural change in push‐pull π‐conjugated polymers and the formation of phase segregation in their bulk heterojunction (BHJ) composite films is investigated. When substituted with large alkyl side chains, the polymer wires experience serious conformational distortion by increasing the torsion energy of dihedral angles along the backbone and undergo large‐scale phase segregation in the BHJ composites.
    Advanced Energy Materials 12/2013; 3(12). DOI:10.1002/aenm.201300434 · 14.39 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We fabricated ZnO-nanowire (NW) field-effect transistors (FETs) coated with poly(3-hexylthiophene) (P3HT) and characterized the electron-transfer characteristics from the P3HT to the ZnO NWs. Under irradiation by laser light with a wavelength of 532 nm, photo-induced electrons were created in the P3HT and then transported to the ZnO NWs, constituting a source-drain current in the initially enhancement-mode P3HT-coated ZnO-NW FETs. As the intensity of the light increased, the current increased, and its threshold voltage shifted to the negative gate-bias direction. We estimated the photo-induced electron density and the electron-transfer characteristics, which will be helpful for understanding organic-inorganic hybrid optoelectronic devices.
    Applied Physics Letters 11/2013; 103(22):223305-223305-4. DOI:10.1063/1.4833544 · 3.52 Impact Factor
  • Jaehyung Lee, Sang-Hoon Kim, Byoung Hoon Lee
    [Show abstract] [Hide abstract]
    ABSTRACT: COPD Diagnosis & Evaluation PostersSESSION TYPE: Original Investigation PosterPRESENTED ON: Wednesday, October 30, 2013 at 01:30 PM - 02:30 PMPURPOSE: Older adults may face a variety of obstacles (comorbid conditions, physical challenges, or mental challenges) to the accurate use of dry powder inhalers (DPIs). The effectiveness of DPIs therapy education in the elderly patients has rarely been formally evaluated.METHODS: Newly diagnosed twenty nine patients with asthma or COPD were instructed two times on proper DPIs (diskus or turbuhaler) usage with 30 days intervals. The effectiveness of education was scored by using a inhaler specific checklist (12 items) after each education. We compared the scores of elderly patients and controls.RESULTS: Total practical performance scores after first education were not different in each group (11.1±0.7 vs 10.2±2.1, P=0.185). Total practical performance scores of elderly patients after second education were high than controls (9.8±1.3 vs 10.9±0.5, P=0.023). Major practical performance scores after first education were not different in each group (4.0±0.0 vs 3.8±0.8, P=0.291). Major practical performance scores after second education were not different in each group (3.75±0.5 vs 4.0±0.0, P=0.098).CONCLUSIONS: The effectiveness of DPIs therapy education in the elderly patients is similar to the young patients.CLINICAL IMPLICATIONS: The elderly patients could use DPIs effectively similar to the young age patients by optimal education.DISCLOSURE: The following authors have nothing to disclose: Jaehyung Lee, Sang-Hoon Kim, Byoung Hoon LeeNo Product/Research Disclosure Information.
    Chest 10/2013; 144(4_MeetingAbstracts):707A. DOI:10.1378/chest.1704247 · 7.13 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A new electron deficient unit, dimethyl-2H-benzimidazole (MBI), and dihydroindeno[2,1-a]indene (ININE) moiety as electron-rich unit were coupled to synthesize the conjugated polymers containing electron donor–acceptor pair for organic photovoltaics. ININE, MBI, and thiophene (or bithiophene) units were incorporated using Stille and Suzuki polymerization to generate poly(2,7-(5,5,10,10-tetrakis(2-ethylhexyl)-5,10-dihydro- indeno[2,1-a]indene)-alt-5,5-(4′,7′-di-2-thienyl-2,2-dimethyl-2H-benzimidazole)) (PININEDTMBIs) (or PININEBBTMBIs). In MBI, the sulfur at 2-position of 2,1,3-benzothiadiazole (BT) unit was replaced with dialkyl-substituted carbon, whereas keeping the 1,2-quinoid form, to improve the solubility of the polymers. The field-effect hole mobility of PININEBBTMBI was 3.2 × 10−4 cm2/Vs which was improved as compared to that of PININEDTMBI (2.7 × 10−5 cm2/Vs) caused by the introduction of bithiophene units. In case of the most efficient polymer, PININEBBTMBI, the device with the configuration of indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene) (PEDOT):polystyrene sulfonate (PSS)/polymer:PC71BM(1:4 w/w)/Al, annealed at 100 °C for 10 min demonstrated a open circuit voltage of 0.78 V, a short-circuit current density of 6.66 mA/cm2, and a fill factor of 0.41, leading to the power conversion efficiency of 2.11%, under white-light illumination (AM 1.5 G, 100 mW/cm2). © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013
    Journal of Polymer Science Part A Polymer Chemistry 01/2013; 51(2):241. DOI:10.1002/pola.26385 · 3.54 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A new accepter with phenanthro[9,10-c][1,2,5]thiadiazole unit was synthesized and utilized for the synthesis of the conjugated polymers, PCPDTDTPT and PCDTPT, containing electron donor–acceptor pairs for OPV devices. This novel phenanthro[9,10-c][1,2,5]thiadiazole unit with phenanthene group can supply planarity and possess electron deficient thiadiazole group. The solid films of PCPDTDTPT and PCDTPT show absorption bands with maximum peaks at 492 and 394 nm and the absorption onsets at 620 and 519 nm, corresponding to band gaps of 2.00 and 2.39 eV, respectively. The HOMO and LUMO levels of PCPDTDTPT and PCDTPT were estimated to be (−5.54, −3.63) and (5.81, 3.65) eV, respectively. The PCDTPT with carbazole moiety shows lower HOMO levels as compared to PCPDTDTPT caused by strong electron donating ability of nitrogen atom to provide higher Voc. The devices with PCPDTDTPT: PC71BM with TiOx layer showed a VOC of 0.77 V, a JSC of 4.71 mA/cm2, and a FF of 0.36, giving a power conversion efficiency of 1.24%.
    Synthetic Metals 12/2012; 162(s 21–22):1936–1943. DOI:10.1016/j.synthmet.2012.08.009 · 2.22 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A new accepter unit, phenanthro[9,10-c][1,2,5]thiadiazole, was synthesized and utilized for the syntheses of the conjugated polymers containing electron donor–acceptor pairs for OPV devices in order to describe the effect of changing the coupling position with cyclopentadithiophene unit. This novel phenanthro[9,10-c][1,2,5]thiadiazole unit with a phenanthene group possesses an electron deficient thiadiazole group and can promote planarity of the compound. The solid films of PCPDTPTm with meta linkage and PCPDTPTp with para linkage show absorption bands with maximum peaks at about 460 and 484 nm and the absorption onsets at 558 and 579 nm, corresponding to band gaps of 2.22 and 2.14 eV, respectively. The absorption spectrum of the PCPDTPTp was red shifted as compared to that of PCPDTPTm, which reveals that PCPDTPTp has longer conjugated length caused by the coupling position. The electron density of the PCPDTPTm HOMO is distributed not only on the donor moiety but also on the thiadiazole moiety to generate intermolecular charge transfer from cyclopentadithiophene unit to phenanthrothiadiazole unit. The device with PCPDTPTm:PC71BM with TiOx layer showed VOC value of 0.97 V, JSC value of 5.50 mA/cm2, and FF of 0.33, giving power conversion efficiency of 1.80%.
    Solar Energy Materials and Solar Cells 10/2012; 105:229–236. DOI:10.1016/j.solmat.2012.05.038 · 5.03 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We investigated the charge dynamics of the conductivity enhancement from 2 to 1000 S/cm in poly(3, 4-ethylenedioxythiophene):poly(styrenesulfonate) as induced by structural changes through the addition of a polar solvent and the following solvent bath treatment. Our results indicate that the addition of a polar solvent selectively enhanced the π-π coupling of the polymer chains, resulting in the reduction of disorder and tremendously increasing the charge carrier mobility, which yielded an insulator-to-metal transition. In contrast, the following solvent bath treatment selectively enhanced the intergrain coupling, which did not affect the disorder or the mobility but increased the charge carrier density. Therefore, we demonstrate that the conduction-character defining disorder in this conducting polymer system is determined by the extent of interchain coupling.
    Physical Review Letters 09/2012; 109(10):106405. DOI:10.1103/PhysRevLett.109.106405 · 7.73 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Symptoms of deep cerebral vein thrombosis (DCVT) are variable and nonspecific. Radiologic findings are essential for the diagnoses. In the majority of cases of deep internal cerebral venous thrombosis, the thalamus is affected bilaterally, and venous hypertension by thrombosis causes parenchymal edema or venous infarction and may sometimes cause venous hemorrhage. Intravenous injections of mannitol can be administered or decompressive craniectomy can be performed for reduction of intracranial pressure. The objectives of antithrombotic treatment in DCVT include recanalization of the sinus or vein, and prevention of propagation of the thrombus. Herein, the authors report DCVT which was successfully treated by low molecular weight heparin.
    09/2012; 14(3):233-6. DOI:10.7461/jcen.2012.14.3.233
  • [Show abstract] [Hide abstract]
    ABSTRACT: We report on a low-temperature fabrication of organic–inorganic nanohybrid nonvolatile memory transistors using molecular layer deposition combined with atomic layer deposition. A 3 nm ZnO:Cu charge trap layer is sandwiched between 6 nm tunneling and 20 nm blocking self-assembled organic layers. First, we identify a large memory window of 14.1 V operated at ±15 V using metal–oxide–semiconductor capacitors. Second, we apply the capacitor structure to the nonvolatile memory transistors which operate in the low voltage range of −1 to 3 V. The writing/erasing (+8 V/−12 V) current ratio of 103 of the memory transistors is maintained during the static and dynamic retention measurements. The reported organic–inorganic devices offer new opportunities to develop low-voltage-driven flexible memory electronics fabricated at low temperatures.
    Journal of Materials Chemistry 08/2012; 22(36). DOI:10.1039/C2JM32767H · 6.63 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This work presents homogeneous bulk heterojunction (BHJ) networks between a push-pull π-conjugated polymer donor, poly(2,7-(5,5,10,10-tetrakis(2-ethylhexyl)-5,10-dihydroindeno[2,1-a]indene)-alt-5,5-(4,7-bis(2,2-bithien-5-yl)-2,2-dimethyl-2H-benzimidazole)) (PININE-BBTMBI) and a fullerene derivative acceptor, [6,6]-phenyl C71-butyric acid methyl ester (PC71BM). By introducing a bi-thiophene unit between the electron-rich and electron-deficient moieties in a repeating unit, the surface energy of PININE-BBTMBI increased to that of PC71BM, enhancing its miscibility in PININE-BBTMBI/PC71BM blends. Direct evidence obtained via atomic force microscopy and the performance of BHJ solar cells indicate that the introduction of the bi-thiophene unit leads to homogeneous BHJ networks and high-performance BHJ solar cells by matching the surface energies at the polymer/fullerene interfaces.
    Applied Physics Letters 08/2012; 101(8-8):083304-5. DOI:10.1063/1.4747331 · 3.52 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The advantage of dimethyl-2H-benzimidazole compared to the benzothiadiazole moiety of PCDTBT is to improve the solubility of the polymer while keeping the 1,2-quinoid form to lead coplanarity of the backbone. New random copolymers, to broaden the absorption range for the wider coverage of the solar spectrum, were synthesized by Stille coupling reactions to generate PCPPDTMBIs (or PCPPBBTMBIs). The solid films of PCPPDTMBIs show absorption bands with two maximum peaks at about 408–417 and 613–640 nm. The PCPPBBTMBIs show two maxima peaks at about 440–444 and 627–650 nm which are red-shifted about 5–30 nm as compared to PCPPDTMBIs caused by the introduction of bithiophene units. The device with PCPPBBTMBI7:PC71BM blend demonstrated a VOC value of 0.64 V, a JSC value of 2.12 mA/cm2, and a FF of 0.34, leading to the efficiency of 0.46%.
    Synthetic Metals 07/2012; 162(s 11–12):988–994. DOI:10.1016/j.synthmet.2012.04.014 · 2.22 Impact Factor

Publication Stats

121 Citations
188.00 Total Impact Points

Institutions

  • 2009–2014
    • Gwangju Institute of Science and Technology
      • School of Materials Science and Engineering
      Gwangju, Gwangju, South Korea
  • 2007–2014
    • Eulji University
      • Department of Internal Medicine
      Sŏul, Seoul, South Korea
  • 2009–2012
    • Chung-Ang University Hospital
      Sŏul, Seoul, South Korea
  • 2008–2012
    • Hanyang University
      • Department of Chemistry
      Sŏul, Seoul, South Korea