• Korean Chemical Engineering Research
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• v.47 no.4
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• pp.418-423
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• 2009

MWCNT(multi-wall carbon nanotube)-doped PEDOT:PSS(poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)), used as a HIL(hole injection layer) material in OLEDs(organic light emitting diodes), was spin-coated on to the ITO glass to form PEDOT:PSS-MWCNT nano composite thin film. Morphology and transparency characteristics of nano composite thin films with respect to the loading percent of MWCNT have been investigated using FT-IR, UV-Vis and SEM. Furthermore, ITO/PEDOT:PSS-MWCNT/NPD/$Alq_3$/Al devices were fabricated, and then J-V and L-V characteristics were investigated. Functional group-incorporated MWCNT was prepared by acid treatment and showed good dispersion property in PEDOT:PSS solution. PEDOT:PSS-MWCNT thin films possessed good transparency property. For multi-layered devices, it was shown that as the loading percent of MWCNT increased, the current density increased but the luminance dramatically decreased. It might be conclusively suggested that the enhanced charge mobility by MWCNT could increase the current density but the hole trapping property of MWCNT could dramatically decrease the hole mobility in the current devices.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.430-430
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• 2008

Using multi plasma enhanced chemical vapor deposition system (Multi-PECVD), p-a-Si:H deposition layer as a $p^+$ region which was annealed by laser (Q-switched fiber laser, $\lambda$ = 1064 nm) on an n-type single crystalline Si (100) plane circle wafer was prepared as new doping method for single crystalline interdigitated back contact (IBC) solar cells. As lots of earlier studies implemented, most cases dealt with the excimer (excited dimer) laserannealing or crystallization of boron with the ultraviolet wavelength range and $10^{-9}$ sec pulse duration. In this study, the Q-switched fiber laser which has higher power, longer wavelength of infrared range ($\lambda$ = 1064 nm) and longer pulse duration of $10^{-8}$ sec than excimer laser was introduced for uniformly deposited p-a-Si:H layer to be annealed and to make sheet resistance expectable as an important process for IBC solar cell $p^+$ layer on a polished n-type Si circle wafer. A $525{\mu}m$ thick n-type Si semiconductor circle wafer of (100) plane which was dipped in a buffered hydrofluoric acid solution for 30 seconds was mounted on the Multi-PECVD system for p-a-Si:H deposition layer with the ratio of $SiH_4:H_2:B_2H_6$ = 30:120:30, at $200^{\circ}C$, 50 W power, 0.2 Torr pressure for 20 minutes. 15 mm $\times$ 15 mm size laser cut samples were annealed by fiber laser with different sets of power levels and frequencies. By comparing the results of lifetime measurement and sheet resistance relation, the laser condition set of 50 mm/s of mark speed, 160 kHz of period, 21 % of power level with continuous wave mode of scanner lens showed the features of small difference of lifetime and lowering sheet resistance than before the fiber laser treatment with not much surface damages. Diode level device was made to confirm these experimental results by measuring C-V, I-V characteristics. Uniform and expectable boron doped layer can play an important role to predict the efficiency during the fabricating process of IBC solar cells.

• Membrane Journal
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• v.19 no.3
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• pp.228-236
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• 2009

ABA type triblock copolymer of poly(hydroxyl ethyl acrylate )-b-polystyrene-b-poly(hydroxyl ethyl acrylate), i.e. PHEA-b-PS-b-PHEA, was synthesized throughatom transfer radical polymerization (ATRP). This block copolymer was thermally crosslinked with 4,5-imidazole dicarboxylic acid (IDA) via the esterification between the -OH groups of PHEA in block copolymer and the -COOH groups of IDA. Upon doping with ${H_3}{PO_4}$ to form imidazole-${H_3}{PO_4}$ complexes, the proton conductivity of membranes continuously increased with increasing ${H_3}{PO_4}$ content. The PHEA-b-PS-b-PHEA/IDA/${H_3}{PO_4}$ polymer membrane with [HEA]:[IDA]:[${H_3}{PO_4}$]=3:4:4 exhibited a maximum proton conductivity of 0.01 S/cm at $100^{\circ}C$ under anhydrous conditions. Thermal gravimetric analysis (TGA) shows that the PHEA-b-PS-b-PHEA/IDA/${H_3}{PO_4}$ complex membranes were thermally stable up to $350^{\circ}C$, indicating their applicability in fuel cells.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.6
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• pp.274-278
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• 2012

$TiO_2$ can be used optically and is applied on many areas such as gas sensor, solar cell and photocatalysis. Electrospun nanofibers have received great interest for development and utilization in some novel applications, such as chemical sensors, dye-sensitized solar cell and photo catalysis. In this study, pure $TiO_2$ and Ga-doped $TiO_2$ nanofibers synthesized by a modified electrospinning method. The Ga doped $TiO_2$ solution is prepared by mixing poly vinyl pyrrolidone, ethyl alcohol, and titanium (IV) isopropoxide. By electrospinning these sols, nanofibers were fabricated. These fibers are heat-treated at $800^{\circ}C$ in air. The prepared pure $TiO_2$ and Ga-doped $TiO_2$ nanofibers samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy.

• Membrane Journal
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• v.19 no.4
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• pp.302-309
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• 2009

A block copolymer of polystyrene-b-poly (hydroxyl ethyl methacrylate), PS-b-PHEMA, was synthesized via atom transfer radical polymerization (ATRP) and crosslinked with 4,5-imidazole dicarboxylic acid (IDA) via esterification of the -OH groups of PHEMA in the block copolymer and the -COOH groups of IDA. Upon doping with $H_3PO_4$ to form imidazole-$H_3PO_4$ complexes, the proton conductivity of the membranes continuously increased as the content of $H_3PO_4$ increased. In addition, both the tensile strength and the elongation at break increased with IDA content. A proton conductivity of 0.01 S/cm at $100^{\circ}C$ was obtained for the PS-b-PHEMA/IDA/$H_3PO_4$ membrane with [HEMA]:[IDA]:[$H_3PO_4$] = 3:4:4 under anhydrous conditions. All of the PS-b-PHEMA/IDA/$H_3PO_4$ membranes were thermally stable up to $350^{\circ}C$, as revealed by thermal gravimetric analysis (TGA).