• Bulletin of the Korean Chemical Society
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• v.23 no.2
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• pp.330-336
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• 2002

A quantum-chemical investigation on the conformations and electronic properties of bis[2-{2-methoxy-4,6-di(t-butyl)phenyl}ethenyl]benzenes (MBPBs) as building block for ${\pi}$-conjugate polymer are performed in order to display the effects of t-butyl and methoxy group substitution and of kink(ortho and meta) linkage. The conjugation length of the polymers can be controlled by substituents and kink linkages of backbone. Structures for the molecules, o-, m-, and p-MBPBs as well as unsubstituted o-, m-, and p-DSBs were fully optimized by using semiempirical AM1, PM3 methods, and ab initio HF method with 3-21G(d) basis set. The potential energy curves with respect to the change of single torsion angle are obtained by using semiempirical methods and ab initio HF/3-21G(d) basis set. The curves are similar shape in the molecules with respect to the position of vinylene groups. It is shown that the conformations of the molecules are compromised between the steric repulsion interaction and the degree of the conjugation. Electronic properties of the molecules were obtained by applying the optimized structures and geometries to the ZINDO/S method. ZINDO/S analysis performed on the geometries obtained by AM1 method and HF/3-21G(d) level is reported. The absorption wavelength on the geometries obtained by AM1 method is much longer than that by HF/3-21G(d) level. The absorption wavelength of MBPBs are red shifted with comparison to that of corresponding DSBs in the same torsion angle because of electron donating substituents. The absorption wavelength of isomers with kink(orth and meta) linkage is shorter than that of para linkage.

• Korean Journal of Materials Research
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• v.21 no.4
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• pp.212-215
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• 2011

New organic light-emitting diodes with structure of indium-tin-oxide[ITO]/N,N'-diphenyl-N, N'-bis-[4-(phenyl-m-tolvlamino)-phenyl]-biphenyl-4,4'-diamine[DNTPD]/1,1-bis-(di-4-poly-aminophenyl) cyclohexane[TAPC]/bis(10-hydroxy-benzo(h)quinolinato)beryllium[Bebq2]/Bebq2:iridium(III)bis(2-phenylquinoline-N,C2')acetylacetonate[(pq)2Ir(acac)]/ET-137[electron transport material from SFC Co]/LiF/Al using the selective doping of 5%-(pq)2Ir(acac) in a single Bebq2 host in the two wavelength (green, orange) emitter formation were proposed and characterized. In the experiments, with a 300${\AA}$-thick undoped emitter of Bebq2, two kinds of devices with the doped emitter thicknesses of 20${\AA}$ and 40${\AA}$ in the Bebq2:(pq)2Ir(acac) were fabricated. The device with a 20${\AA}$-thick doped emitter is referred to as "D-1" and the device with a 4${\AA}$-thick doped emitter is referred to as "D-2". Under an applied voltage of 9V, the luminance of D-1 and D-2 were 7780 $cd/m^2$ and 6620 $cd/m^2$, respectively. The electroluminescent spectrum of each fabricated device showed peak emissions at the same two wavelengths: 508 nm and 596 nm. However, the relative intensity of 596 nm to 508 nm at those wavelengths was higher in the D-2 than in the D-1. The D-1 and D-2 devices showed maximum current efficiencies of 5.2 cd/A and 6.0 cd/A, and color coordinates of (0.31, 0.50) and (0.37, 0.48) on the Commission Internationale de I'Eclairage[CIE] chart, respectively.

• Journal of the Korean Ceramic Society
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• v.39 no.2
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• pp.210-215
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• 2002

Optical Band-pass Filter(BPF) for the selected wavelength of 4300 nm was designed and fabricated on Si wager by alternately depositing Ge and $SiO_2$ thin layers by an electron beam evaporation technique. The fabricated BPF showed the optical transmittance characteristics of 58.2% with FWHM(Full Width at Half Maximum) of 204 nm at 4300 nm, but showed the transmittance less than 5% due to the reflectance over all the wavelength ranges except 4300 nm band. The $CO_2$ sensitivity of BPF was investigated with the transmittance as a function of $CO_2$ gas concentration using a sensing cell attached to FT-IR instrument. The transmittance of BPF was almost linearly decreased with increasing of $CO_2$ concentration in the range of from 500 to 5000 ppm. The sensing structure using double BPFs showed higher slop of transmittance vs $CO_2$ concentration, and thus higher gas sensitivity than that using a single BPF, even though the former had relatively lower transmittance.

• Bulletin of the Korean Chemical Society
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• v.32 no.8
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• pp.2743-2750
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• 2011

Lanthanide(III)-cored complex as a wavelength conversion material has been successfully designed and synthesized for highly efficient dye-sensitized solar cells, for the first time, since light with a short wavelength has not been effectively used for generating electric power owing to the limited absorption of these DSSCs in the UV region. A black dye (BD) was chosen and used as a sensitizer, because BD has a relatively weak light absorption at shorter wavelengths. The overall conversion efficiency of the BD/WCM device was remarkably increased, even with the relatively small amount of WCM added to the device. The enhancement in $V_{oc}$ by WCM, like DCA, could be correlated with the suppression of electron recombination between the injected electrons and $I_3{^-}$ ions. Furthermore, the short-circuit current density was significantly increased by WCM with a strong UV light-harvesting effect. The energy transfer from the Eu(III)-cored complex to the $TiO_2$ film occurred via the dye, so the number of electrons injected into the $TiO_2$ surface increased, i.e., the short-circuit current density was increased. As a result, BD/WCM-sensitized solar cells exhibit superior device performance with the enhanced conversion efficiency by a factor of 1.22 under AM 1.5 sunlight: The photovoltaic performance of the BD/WCM-based DSSC exhibited remarkably high values, $J_{sc}$ of 17.72 mA/$cm^2$, $V_{oc}$ of 720 mV, and a conversion efficiency of 9.28% at 100 mW $cm^{-2}$, compared to a standard DSSC with $J_{sc}$ of 15.53 mA/$cm^2$, $V_{oc}$ of 689 mV, and a conversion efficiency of 7.58% at 100 mW $cm^{-2}$. Therefore, the Eu(III)-cored complex is a promising candidate as a new wavelength conversion coadsorbent for highly efficient dye-sensitized solar cells to improve UV light harvesting through energy transfer processes. The abstract should be a single paragraph which summaries the content of the article.

• Journal of Sensor Science and Technology
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• v.15 no.3
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• pp.186-191
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• 2006

In general, Cerenkov light is produced by a charged particle that passes through a medium with a velocity greater than that of visible light. Although the wavelength of Cerenkov light is very broad, the peak is in the almost visible range from 400 to 480 nm. Therefore, it always causes a problem to detect a real light signal that is generated in the scintillator on the fiber-optic sensor tip for dose measurements of high-energy electron beam. The objectives of this study are to measure, characterize and remove Cerenkov light generated in a fiber-optic radiation sensor tip to detect a real light signal from the scintillator. In this study, the intensity of Cerenkov light is measured and characterized as a function of incident angle of electron beam from a LINAC, and as a function of the energy of electron beam. As a measuring device, a photodiode-amplifier system is used, and a subtraction method using a background optical fiber is investigated to remove Cerenkov light.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.3
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• pp.422-428
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• 2015

A 2.45GHz microwave plasma source with a linear antenna has been developed for low temperature large scale deposition processing. Microwave power is transmitted through WR340 waveguide and a copper rod, linear antenna, is located in a quartz tube. The power matching is effectively achieved by a linear antenna is located at ${\lambda}_g/4$ or $3{\lambda}_g/4$ from the end of WR340 waveguide. The Ar plasma was generated along the surface of quartz tube and a clear standing wave pattern with nearly 10cm wavelength was observed at Ar pressure of 200mTorr and 200W input power. The electron density and electron temperature were investigated by using the electrostatic probe. The electron density and electron temperature were highly measured near the surface of quartz tube. Ar plasma density along the quartz tube is mostly uniform despite standing wave set-up and antenna of long length. A uniform temperature was measured at 10~40cm distance from the end quartz tube and 5cm distance from the surface of quartz tube.

• Applied Chemistry for Engineering
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• v.23 no.6
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• pp.539-545
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• 2012

3-(2-benzotriazolovinyl)thiophene (BVT) was synthesized by the connection of the thiophene with the electron-withdrawing group, benzotriazole, through the vinylene. Its structure was confirmed by FT-IR, $^1H$-NMR, $^{13}C$-NMR and 2D hetero-cosy spectroscopy. Both BVT and 3-octylthiophene (OT) were copolymerized and showed an average molecular weight of 12000 (PDI 2.67) and 15000 (PDI 2.55), respectively. The copolymers were dissolved in the organic solvent such as chloroform, THF, TCE, etc. The mole ratios of BVT and OT in the synthesized copolymers were confirmed as 1 : 1.8 and 1 : 2.8 from $^1H$-NMR spectra. The UV-vis maximum absorption of copolymers appeared at the wavelength of 470 nm and 465 nm and the photoluminescence at ${\lambda}_{max}$ = 662 nm and 641 nm correspond to red-orange light. The band gaps of copolymers at 1.96 eV and 2.02 eV were found to be higher than those of poly(3-octylthiophene). The HOMO energy levels of the copolymers decreased overall in comparison with those of poly(3-octylthiophene), but the overall LUMO energy level increased.

• Journal of the Korean Magnetics Society
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• v.25 no.5
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• pp.149-155
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• 2015

The ECR (Electron Cyclotron Resonance) Ar ion milling was manufactured to fabricate the device of thin film. The ECR ion milling system applied to the device etching operated by a power of 600W, a frequency of 2.45 GHz, and a wavelength of 12.24 cm and transferred by a designed waveguide. In order to match one resonant frequency, a magnetic field of 908 G was applied to a cavity inside of ECR. The Ar gas intruded into a cavity and created the discharged ion beam. The surface of target material was etched by the ion beam having an acceleration voltage of 1000 V. The formed devices with a width of $1{\mu}m{\sim}9{\mu}m$ on the GMR-SV (Giant magnetoresistance-spin valve) multilayer after three major processes such as photo lithography, ion milling, and electrode fabrication were observed by the optical microscope.

• Journal of the Korean GEO-environmental Society
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• v.20 no.11
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• pp.5-10
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• 2019

For the development of long-wavelength responding photocatalyst, Ag was applied to commercial $TiO_2$ to produce $Ag/TiO_2$ photocatalyst. Moreover, micro-emulsion method was used in order to increase the efficiency of the photocatalyst by enhancing the dispersion of Ag. Physical properties of the manufactured catalyst were analyzed by scanning electron microscopy (SEM), field emission transmission electron microscopy (FE-TEM) and diffuse reflectance spectroscopy (DRS). For the catalytic performance measurement, RO 16 (Reactive Orange 16) removal was performed with 25 ppm RO 16 under UV-A (365 nm) irradiation. In addition, ball milling and dip-coating method were used to synthesize the photocatalyst for the comparison of the outcomes of using different synthesis methods. In addition, catalytic performance was improved by varying the Ag content and surfactant content. The highest catalytic performance was shown at $Ag/TiO_2$ synthesized by micro-emulsion method with 2 wt% of Ag content, and 0.5 g of the surfactant.

• Korean Journal of Metals and Materials
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• v.46 no.10
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• pp.683-690
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• 2008

In order to develop transparent electrodes for high efficiency GaN-based light emitting diodes (LEDs), the electrical and optical properties of the electron beam evaporated ITO contacts have been investigated as a function of the deposition temperature and flow rate of oxygen during the deposition. As the deposition temperature increases from $140^{\circ}C$ to $220^{\circ}C$, the resistivity of the ITO films decreases slightly from $4.0{\times}10^{-4}{\Omega}cm$ to $3.3{\times}10^{-4}{\Omega}cm$, meanwhile the transmittance of the ITO films significantly increases from 67% to 88% at the wavelength of 470 nm. When the flow rate of oxygen during the deposition increases from 2 sccm to 4 sccm, the resistivity of the ITO films increases from $3.6{\times}10^{-4}{\Omega}cm$ to $7.4{\times}10^{-4}{\Omega}cm$, meanwhile the transmittance of the ITO films increases from 86% to 99% at 470 nm. Blue LEDs fabricated with the electron beam evaporated ITO electrode show that the ITO films deposited at $200^{\circ}C$ and 3 sccm of the oxygen flow rate give a low forward-bias voltage of 3.55 V at injection current of 20 mA with a highest output power.