• Title/Summary/Keyword: PL properties

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Photovoltaic Properties of MEH-PPV/DFPP Blend Devices Based on Novel n-type Polymer DFPP (새로운 n형 고분자인 DFPP 기반의 MEH-PPV/DFPP Blend 소자의 광전특성)

  • Kim, Su-Hyun;Moon, Ji-Sun;Lee, Jae-Woo;Lee, Seok;Kim, Sun-Ho;Byun, Young-Tae;Kim, Dong-Young;Lee, Chang-Jin;Kim, Eu-Gene;Chung, Young-Chul;Rie, Kung-Won
    • Korean Journal of Optics and Photonics
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    • v.17 no.5
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    • pp.461-468
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    • 2006
  • Optical characteristics in polymer films of MEH-PPV/DFPP blends were for the first time investigated. DFPP (N, N'-diperfluorophenyl-3,4,9,10-perylenetetracarboxylic diimide) used here was a novel n-type polymer, which had good stability in air and solubility in common solvents. For a 1:9 DFPP:MEH-PPV blend, highly efficient quenching of photoluminescence (PL) was observed. In addition, the photocurrent responses of these MEH-PPV/DFPP photovoltaic cells were measured. When the light intensity was $50mW/cm^2$, short-circuit photocurrent densities were two times higher than those of single layer MEH-PPV devices.

Ecological Characteristic of Warm Temperate Vegetation Distributed around Hakdong and Haegeumgang at Geojae Island (거제도 학동 및 해금강 일대에 분포하는 난대림 식생의 생태적 특성 연구)

  • Lee, Soo-Dong
    • Korean Journal of Environment and Ecology
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    • v.36 no.1
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    • pp.72-86
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    • 2022
  • This study was conducted to identify structural characteristics of the evergreen broad-leaved forests distributed in Hak-dong, Geojae island. For a survey, 52 sites were set up in areas with changes in the vegetation community or location environment where Cinnamomum yabunikkei, Neolitsea sericea, and Machilus thunbergii dominated or appeared in the canopy, sub-canopy, or shrub layer. The community classification with TWINSPAN identified the following communities: N. sericea-C. yabunikkei, C. yabunikkei-Camellia japonica, Ca. japonica, Quercus variabilis-Ca. japonica, Pinus thunbergii-Ca. japonica, Castanopsis sieboldii, P. thunbergii, and Platycarya strobilacea-Mallotus japonicus. Considering the result of the study that succession series of warm-temperate forest reflecting the latent natural vegetation is the transition of conifers and deciduous broad-leaved forest to evergreen broad-leaved forest, the communities predominated by the communities predominated by the communities predominated by P. thunbergii, Q. variabilis, and Pl. strobilacea are likely to transform into the evergreen forest predominated by N. sericea and C. yabunikkei. The sites where C. yabunikkei, N. sericea, and Castanopsis sieboldii are dominant in the canopy and sub-canopy layers are likely to maintain the status quo if there is no artificial disturbance. The relationship between the impact of the environmental factors and the vegetation distribution showed silt among the physical properties of the soil directly or indirectly affected it, which was judged to be due to the fact that it was located on a steep slope. The soil acidity (pH) was 5-5.84, electrical conductivity 0.047-0.139 dS/m, and organic matter content was 3.32-12.06%. Although there were differences by the colony, they were generally low.

Degradation of Antibiotics Using Silver Decorated Heterojunction Carbon Nitride under Visible Light (은 장식 이종접합 질화탄소를 이용한 가시광선 조건에서의 항생제 분해 연구)

  • Taeyoon, Lee
    • Journal of the Korean GEO-environmental Society
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    • v.24 no.3
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    • pp.23-27
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    • 2023
  • Graphitic carbon nitride (g-C3N4) has been used as effective photocatalyst for degradation of antibiotics under visible light irradiation. However, the fast recombination of hole-electron pair may limit their photocatalytic efficiency. In our study, Ag was grafted on g-C3N4/g-C3N4 isotype heterojunction by a microwave-assisted decomposition method. The structure and physical properties of heterojunction photocatalyst were characterized through X-ray diffraction, UV-DRS, FT-IR, and Photoluminescence analyses. Ag decorated g-C3N4/g-C3N4 isotype heterojunction exhibited excellent photocatalytic activity for degradation of sulfamethoxazole under irradiation under visible light irradiation within 210 min, which is higher than g-C3N4/g-C3N4 isotype heterojunction and bulk g-C3N4. The addition of Ag may broaden the visible light absorption and restrict the recombination of hole-electron pair because of the surface plasmons resonance, resulting in the improving the photocatalytic activity.

Growth and Photocurrent Properties of $CuGaSe_2$ Single Crystal ($CuGaSe_2$ 단결정 박막 성장과 광전류 특성)

  • K.J. Hong
    • Proceedings of the Materials Research Society of Korea Conference
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    • 2003.03a
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    • pp.81-81
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    • 2003
  • The stochiometric mixture of evaporating materials for the CuGaSe$_2$ single crystal thin films were prepared from horizontal furnace. Using extrapolation method of X-ray diffraction patterns for the polycrystal CuGaSe$_2$, it was found tetragonal structure whose lattice constant no and co were 5.615$\AA$ and 11.025$\AA$, respectively. To obtains the single crystal thin films, CuGaSe$_2$ mixed crystal was deposited on throughly etched GaAs(100) by the Hot Wall Epitaxy(HWE) system. The source and substrate temperature were 61$0^{\circ}C$ and 45$0^{\circ}C$ respectively, and the growth rate of the single crystal thin films was about 0.5${\mu}{\textrm}{m}$/h. The crystalline structure of single crystal thin films was investigated by the double crystal X-ray diffraction(DCXD). Hall effect on this sample was measured by the method of van der pauw and studied on carrier density and mobility depending on temperature. From Hall data, the mobility was likely to be decreased by pizoelectric scattering in the temperature range 30K to 150K and by polar optical scattering in the temperature range 150K to 293K. The optical energy gaps were found to be 1.68eV for CuGaSe$_2$ single crystal thin films at room temperature. The temperature dependence of the photocurrent peak energy is well explained by the Varshni equation then the constants in the Varshni equation are given by a=9.615$\times$ 10$^{-4}$ eV/K, and $\beta$=335K. From the photocurrent spectra by illumination of polarized light of the CuGaSe$_2$ single crystal thin films. We have found that values of spin orbit coupling ΔSo and crystal field splitting ΔCr was 0.0900eV and 0.2498eV, respectively. From the PL spectra at 20K, the peaks corresponding to free bound excitons and D-A pair and a broad emission band due to SA is identified. The binding energy of the free excitons are determined to be 0.0626eV and the dissipation energy of the acceptor-bound exciton and donor-bound exciton to be 0.0352eV, 0.0932eV, respectively.

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Effect of Deposition and Heat Treatment Conditions on the Electrical and Optical Properties of AZO/Cu/AZO Thin Film (증착 및 열처리 조건에 따른 AZO/Cu/AZO 박막의 전기적·광학적 특성 평가)

  • Chan-Young Kim;Ha-Eun Lim;Gaeun Yang;Sukjeang Kwon;Chan-Hee Kang;Sang-Chul Lim;Taek Yeong Lee
    • Korean Journal of Materials Research
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    • v.33 no.4
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    • pp.142-150
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    • 2023
  • AZO/Cu/AZO thin films were deposited on glass by RF magnetron sputtering. The specimens showed the preferred orientation of (0002) AZO and (111) Cu. The Cu crystal sizes increased from about 3.7 nm to about 8.5 nm with increasing Cu thickness, and from about 6.3 nm to about 9.5 nm with increasing heat treatment temperatures. The sizes of AZO crystals were almost independent of the Cu thickness, and increased slightly with heat treatment temperature. The residual stress of AZO after heat treatment also increased compressively from -4.6 GPa to -5.6 GPa with increasing heat treatment temperature. The increase in crystal size resulted from grain growth, and the increase in stress resulted from the decrease in defects that accompanied grain growth, and the thermal stress during cooling from heat treatment temperature to room temperature. From the PL spectra, the decrease in defects during heat treatment resulted in the increased intensity. The electrical resistivities of the 4 nm Cu film were 5.9×10-4 Ω·cm and about 1.0×10-4 Ω·cm for thicker Cu films. The resistivity decreased as the temperature of heat treatment increased. As the Cu thickness increased, an increase in carrier concentration resulted, as the fraction of AZO/Cu/AZO metal film increased. And the increase in carrier concentration with increasing heat treatment temperature might result from the diffusion of Cu ions into AZO. Transmittance decreased with increasing Cu thicknesses, and reached a maximum near the 500 nm wavelength after being heat treated at 200 ℃.

Development of novel oxyfluoride glasses and glass ceramics for photoluminescence material by a containerless processing (무용기 용융법을 활용한 형광소재용 결정화 유리 개발)

  • Hyerin Jo;Minsung Hwang;Youngjin Lee;Jaeyeop Chung
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.33 no.5
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    • pp.181-186
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    • 2023
  • In this study, novel Eu2O3-BaF2-La2O3-B2O3 oxyfluoride glasses and glass ceramics were developed by a containerless processing. Differential thermal analysis (DTA) analysis was performed to analyze the thermophysical properties of oxyfluoride glasses doped with Eu2O3, and photoluminescence (PL) characteristics were analyzed to evaluate the luminous efficiency depending on the degree of crystallinity. The glass transition temperature decreased with increasing BaF2 concentration since BaF2 acts as a network modifier in this glass system. In addition, thermal stability which can be estimated by the difference between the glass transition temperature and the onset temperature of the crystallization decreased with increasing BaF2 contents. The peak related to the BaF2 crystal was confirmed after the crystallization by X-ray Diffraction (XRD) analysis. Photoluminescence intensity increased after the crystallization which indicates that the Eu3+ ions are sited in BaF2 crystal. La 3d5/2 x-ray photoelectron spectroscopy (XPS) and F1s XPS spectra were analyzed to precisely understand the behavior of the fluorine ion in the glass structure. Fluorine tends to bond with the network modifying cations such as La3+ and Ba2+ ions and after the crystallization the La-F bonds decreased because F- ions used to form BaF2 crystals.

A STUDY ON THE MEASUREMENT OF THE IMPLANT STABILITY USING RESONANCE FREQUENCY ANALYSIS (공진 주파수 분석법에 의한 임플랜트의 안정성 측정에 관한 연구)

  • Park Cheol;Lim Ju-Hwan;Cho In-Ho;Lim Heon-Song
    • The Journal of Korean Academy of Prosthodontics
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    • v.41 no.2
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    • pp.182-206
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    • 2003
  • Statement of problem : Successful osseointegration of endosseous threaded implants is dependent on many factors. These may include the surface characteristics and gross geometry of implants, the quality and quantity of bone where implants are placed, and the magnitude and direction of stress in functional occlusion. Therefore clinical quantitative measurement of primary stability at placement and functional state of implant may play a role in prediction of possible clinical symptoms and the renovation of implant geometry, types and surface characteristic according to each patients conditions. Ultimately, it may increase success rate of implants. Purpose : Many available non-invasive techniques used for the clinical measurement of implant stability and osseointegration include percussion, radiography, the $Periotest^{(R)}$, Dental Fine $Tester^{(R)}$ and so on. There is, however, relatively little research undertaken to standardize quantitative measurement of stability of implant and osseointegration due to the various clinical applications performed by each individual operator. Therefore, in order to develop non-invasive experimental method to measure stability of implant quantitatively, the resonance frequency analyzer to measure the natural frequency of specific substance was developed in the procedure of this study. Material & method : To test the stability of the resonance frequency analyzer developed in this study, following methods and materials were used : 1) In-vitro study: the implant was placed in both epoxy resin of which physical properties are similar to the bone stiffness of human and fresh cow rib bone specimen. Then the resonance frequency values of them were measured and analyzed. In an attempt to test the reliability of the data gathered with the resonance frequency analyzer, comparative analysis with the data from the Periotest was conducted. 2) In-vivo study: the implants were inserted into the tibiae of 10 New Zealand rabbits and the resonance frequency value of them with connected abutments at healing time are measured immediately after insertion and gauged every 4 weeks for 16 weeks. Results : Results from these studies were such as follows : The same length implants placed in Hot Melt showed the repetitive resonance frequency values. As the length of abutment increased, the resonance frequency value changed significantly (p<0.01). As the thickness of transducer increased in order of 0.5, 1.0 and 2.0 mm, the resonance frequency value significantly increased (p<0.05). The implants placed in PL-2 and epoxy resin with different exposure degree resulted in the increase of resonance frequency value as the exposure degree of implants and the length of abutment decreased. In comparative experiment based on physical properties, as the thickness of transducer increased, the resonance frequency value increased significantly(p<0.01). As the stiffness of substances where implants were placed increased, and the effective length of implants decreased, the resonance frequencies value increased significantly (p<0.05). In the experiment with cow rib bone specimen, the increase of the length of abutment resulted in significant difference between the results from resonance frequency analyzer and the $Periotest^{(R)}$. There was no difference with significant meaning in the comparison based on the direction of measurement between the resonance frequency value and the $Periotest^{(R)}$ value (p<0.05). In-vivo experiment resulted in repetitive patternes of resonance frequency. As the time elapsed, the resonance frequency value increased significantly with the exception of 4th and 8th week (p<0.05). Conclusion : The development of resonance frequency analyzer is an attempt to standardize the quantitative measurement of stability of implant and osseointegration and compensate for the reliability of data from other non-invasive measuring devices It is considered that further research is needed to improve the efficiency of clinical application of resonance frequency analyzer. In addition, further investigation is warranted on the standardized quantitative analysis of the stability of implant.

An Experimental Study on Friction Welding and Heat Treatment of Engine Exhaust Valve Steels ( SCr4-21-4 N , SUH3-21-4-N (기관배기 밸브용 강 ( SCr4-21-4N , SUH3-21-4N ) 의 마찰압접과 열처리에 관한 실험적 연구)

  • 오세규
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.14 no.2
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    • pp.79-87
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    • 1978
  • This is an experimental study on friction welding and heat treatment of engine exhaust valve materials whose welding combination is SCr4 as stem to 21-4N as head and SUH3 to 21-4N. In this study, not only the experiments of friction welding under the selected optimum welding condition and the examination of the mechanical properties were carried out, but also the heat treatment of friction welded specimens under the two selected conditions was taken to obtain the better welding character, eliminating the latent stress and the hardness peak which appeared at the welded zones of heat resisting steel(21-4N, SUH3) and low alloyed steel ($SCr_4$) friction weldments. The results obtained by the experiments and consideration in this study are as follows: I) It was experimentally proved quite reasonable that 'speed=3,OOO rpm, heating pressure Pl=8 kg/ mm2, upsetting pressure p, = 20 kg/mm', heating time $t_1$ = 3 see, upsetting time TEX>$t_2$ = 2.5 sec' was selected as the optimum welding condition for friction-welding the engine exhaust valve materials $SCr_4$ to 21-4 Nand SUH 3 to 21-4 N. 2) The results of the previous study and this one on friction welding of such dissimilar materials as SUH 3-SUH 31, SCr 4-SUH 31, SCr 4-SUH 3, SUH 3-CRK 22, SCr4-21-4 Nand SUH3-21-4 N agreed with each other substantially in the friction welding characteristics at welded interface zones. 3) It was also certified quite satisfactory that '600\ulcornerCX30 min. Xroom air cooling' as an optimum heat treatment condition of the friction welded materials SCr 4-21-4 Nand SUH 3-21-4 N was experimentally determined to eliminate the latent stress and the hardness peak at welded zones. 4) About 20% of the tensile strength before heat treatment of friction welded specimens was decreased after heat treatment 600\ulcornerCX30 min. Xair cooling, but the location of fracture was moved from heat affected zone to parent $SCr_4$ & SUH3. 5) Microscopic examination of the weld joints friction-welded and heat-treated under the above mentioned conditions revealed that the weld zone is very narrow and has a fine grained intermixed structure without any welding defects. 6) The above mentioned conditions can be also utilized as friction welding parameters of the other dissimiar materials for engine valve production.

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