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김은미,박경희,구할본,박복기,Jin, En-Mei,Park, Kyung-Hee,Gu, Hal-Bon,Park, Bok-Kee 한국전기전자재료학회 2009 전기전자재료학회논문지 Vol.22 No.6
$TiO_2$ nano-particle paste was prepared by ethyl cellulose, $\alpha$-terpineol and bis(2-ethylhexyl) phthalate (dioxcyl phthalate) for dye-sensitized solar cells (DSSCs). Dispersion and absorbance of $TiO_2$ photoanode films was controlled by adding different amount of ethyl cellulose and $\alpha$-terpineol. The morphology of prepared $TiO_2$ films was studied by field emission scanning electron microscopy (FE-SEM) and the optical properties of $TiO_2$ films were measured by UV/vis spectra. Photovoltaic-current density was observed to determine the electrochemical response of DSSCs. Energy conversion efficiency was obtained about 7.1% at ethyl cellulose and $\alpha$-terpineol at optimal mixed ratio (as ethyl cellulose: 0.1 g; $\alpha$-terpineol: 1.5 ml) under illumination with AM 1.5($100\;Wcm^{-2}$) simulated sunlight.
MnO<sub>2</sub>-HCS 복합체를 이용한 슈퍼커패시터의 전기화학적 특성
김은미,정상문,Jin, En Mei,Jeong, Sang Mun 한국청정기술학회 2018 청정기술 Vol.24 No.3
중공형 구형 탄소(hollow carbon spheres, HCS) 또는 구형 탄소(carbon spheres, CS)는 수열합성법에 의해 제조되었고 $MnO_2$를 증착하기 위한 탄소 지지체로 사용하였다. $MnO_2$는 화학적 레독스 증착법에 의해 HCS 또는 CS 표면에 증착하였다. 화학적 산화환원 증착법은 미립자 지지체의 표면에 다른 산화물 합성에 특히 효과적이다. $MnO_2$는 HCS 또는 CS의 표면에 일정한 슬릿 모양의 분포를 보였고 HCS 표면에서 보다 엉성한 슬릿 모양의 $MnO_2$ 입자가 생성되었다. $MnO_2-HCS$는 $20mv\;s^{-1}$의 스캔 속도에서 초기 사이클에서 약 $164.1F\;g^{-1}$의 정전용량을 나타내었고 1000 사이클 후에는 약 $141.3F\;g^{-1}$의 정전용량을 나타내었다. 1000 사이클 기준으로 $MnO_2-HCS$와 $MnO_2-CS$는 각각 86%와 78%의 용량유지율을 나타내었다. 이것은 HCS 표면에서 엉성한 슬릿모양의 $MnO_2$의 성장이 전해질의 흐름 및 전해질 내의 $Na^+$ 이온의 흡탈착이 보다 용이하여 나타난 결과로 생각된다. Hollow carbon spheres (HCS) and carbon spheres (CS) were prepared by a hydrothermal reaction and they were introduced as a substrate for the deposition of $MnO_2$ nanoparticles. The $MnO_2$ nanoparticles were deposited on the carbon surface by a chemical redox deposition method. After deposition, the $MnO_2$ nanoparticles were uniformally distributed on the carbon surface in a slit-shape, and sparse $MnO_2$ slits appeared on the HCS surface. The $MnO_2-HCS$ showed an initial specific capacitance of $164.1F\;g^{-1}$ at scan rate of $20mv\;s^{-1}$, and after 1,000 cycles, the specific capacitance was maintained to $141.3F\;g^{-1}$. The capacity retention of $MnO_2-HCS$ and $MnO_2-CS$ were calculated to 86% and 78% in the cycle performance test up to 1,000 cycles, respectively. $MnO_2-HCS$ showed a good cycle stability due to the mesoporous hollow structure which can cause a faster diffusion of the electrolyte and can easily adsorb and desorb $Na^+$ ions on the surface of the electrode.
김은미 ( En Mei Jin ),구할본 ( Hal Bon Gu ) 조선대학교 공학기술연구원 2011 공학기술논문지 Vol.4 No.2
The acid treatment have been used for nanocrystalline TiO2 particles. It ha been observed that nitric acid treatment can enhance transparency of thin films a well as higher level of dispersion of nanoparticles. HNO3 treated surfaces has showed higher surface area and increase in hydroxy functional groups at TiO2 photoelectrode film surfaces was observed. This process has allowed to increase the conversion efficiency of solar cell which is possibly due to higher amount of dye adsorption. These process have significantly enhanced the efficiency of DSCs for developing high sensitivity. The efficiency increased upto 11 8% and this is observed at non nitric acid treatment of TiO2 photoelectrode.
상용 고용량 리튬이온이차전지용 NCA 양극활물질의 전기화학적 특성
김은미 ( En Mei Jin ),이가을 ( Ga-eul Lee ),나병기 ( Byuong-ki Na ),정상문 ( Sang Mun Jeong ) 한국화학공학회 2017 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.55 No.2
In order to investigate the electrochemical properties and the particle size effect of LiNi<sub>1-x-y</sub>Co<sub>x</sub>Al<sub>y</sub>O<sub>2</sub> (x=0.15, y=0.045 or 0.05, NCA) for lithium ion batteries (LIBs), two commercial NCA cathode materials (NCA#1, NCA#2) were used as cathode materials for LIB. The average particle size of the NCA#1 which consisted of uniform spherical particles was found to be approximately 5 μm. NCA#2 consisted of particles with bimodal size distribution of approximately 5 μm and 11 μm. From the results of charge-discharge performance test, a high initial discharge capacity of 197.0 mAh/g was obtained with NCA#2, which is a higher value than that with NCA#1. The cycle retentions of NCA#1 and NCA#2 up to 30 cycles were 92% and 94%, respectively.
리튬 폴리머 전지용 정극활물질 LiFePO4 및 LiM(x)Fe(1-x)PO4의 전기화학적 특성
김은미 ( En Mei Jin ),박경희 ( Kyung Hee Park ),구할본 ( Hal Bon Gu ) 조선대학교 공학기술연구원 2009 공학기술논문지 Vol.2 No.2
Phospho-olivine LiFePO4 and LiTi0.1Fe0.9PO4 calhode materials were prepared by the solid-state reaction at the different temperature (550, 600 and 650℃). To improve conductivity carried out Ti2+ doped LiFeP04 and we studied the effect of electrochemical performance. At the different heating temperature resulted in the didn``t appearance of impurity phase which was shown by high resolution X-ray diffraction and perepared by 600℃ temperature``s discharge performance results exhibited an excellent high capacity of 140 mAh/g at the first cycle, and 139 mAh/g after 50 cycles. The Ti2+ doped LiFeP04 started 3.36 V of flat voltage on discharge curve and showed a gentle decline in the curve compared to undoped LiFeP04 without great changes of capacity. And so, we could achieve to improve electrochemical performance as reversible, cycle life. Similarly, LiFePO4 doping with Ti2+ showed the effect of dopant which is the improved discharge capacity as 140 mAh/g and good cycling performance.
수열합성한 TiO2을 이용한 염료감응형 태양전지의 전기화학적 특성
김은미 ( En Mei Jin ),왕만림 ( Wan Lin Wang ),구할본 ( Hal Bon Gu ) 조선대학교 공학기술연구원 2013 공학기술논문지 Vol.6 No.1
In this study, the TiO2 was prepared by hydrothermal reactions; and 0.5 M, 1.0 M and 2.0 M TTIP were added. The different contents of TTIP added TiO2 are studied by X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), and photocurrent density-voltage test. The photovoltaic properties under illumination with AM 1.5 simulated under sunlight. In the results, the XRD patterns index to single-phase material having an anatage structure and the particle size of 1.0 M TTIP added TiO2 is 7.61 nm. Using the 1.0 M TTIP added TiO2 demonstrates a higher solar conversion efficiency than the other samples. We got 114% and 131% enhanced power conversion efficiency when the optimal content of TTIP.
TiO2 광전극의 광산란 특성을 이용한 염료감응형 태양전지
김은미 ( En Mei Jin ),박경희 ( Kyung Hee Park ),구할본 ( Hal Bon Gu ) 조선대학교 공학기술연구원 2010 공학기술논문지 Vol.3 No.2
In this study, we increase the solar conversion efficiency of DSSC (dye-sensitized solar cell) using nanocrystalline TiO2 semiconductor. We preparation of TiO2 photoelectrode, assembly the DSSC and put a focus in analyses electrochemical properties of DSSC by using quartz glass powder in TiO2 photoelectrode to increase light scattering effect and improved conversion efficiency. Morphology of the photoelectrode was investigate using field emission scanning electron microscopy (FE-SEM) and photovoltaic properties was examined under illumination with AM 1.5 simulated sunlight. The results showed 146% power conversion efficiency when the optimal content of quartz glass powder was 5 wt.% than another content.
Radio Frequency Plasma Power변화에 따른 ITO 특성 및 OLED의 광학적 특성
기현철,김회종,홍경진,김은미,구할본,Ki, Hyun-Chul,Kim, Hwe-Jong,Hong, Kyung-Jin,Kim, En-Mei,Gu, Hal-Bon 한국전기전자재료학회 2009 전기전자재료학회논문지 Vol.22 No.1
We has been analysed optical properties of OLED(organic light emitting diode) and characteristics of ITO(Indium Tin Oxide) in terms of $O_2$ plasma treatment for manufacturing high efficiency OLED, RF power of $O_2$ plasma was changed 25, 50, 100, 200 W. $O_2$ gas flow, gas pressure and treatment time were fixed. Sheet resistance and surface roughness of ITO were measured by Hall-effect measurement system and AFM, respectively. The ranges of sheet resistance and surface roughness were $5.5{\sim}6,06\;{\Omega}$ and $2.438{\sim}3.506\;nm$ changing of RF power, respectively, PM(Passive Matrix)OLED was fabricated with the structure of ITO(plasm treatment)/TPD($400\;{\AA}$)/$Alq_3(600\;{\AA})$/LiF($5\;{\AA}$)/Al($1200\;{\AA}$). Turn-on voltage of PMOLED was 7 V and luminance was $7,371\;cd/m^2$ at the RF power of 25 W, $O_2$ plasma treatment of ITO surface was result in lowering the operating voltage and improving luminance of PMOLED.
전착법을 이용한 슈퍼커패시터용 다공성 Co(OH)₂ 나노플레이크 박막의 제조 및 전기화학적 특성
이현정 ( Hyeon Jeong Lee ),김은미 ( En Mei Jin ),정상문 ( Sang Mun Jeong ) 한국화학공학회 2016 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.54 No.2
Porous Co(OH)₂ nano-flake thin films were prepared by a potential-controlled electro-deposition technique at various deposition voltage (-0.75, -1.0, -1.2, and -1.4 V) on Ti-mesh substrates for supercapacitor application. The potential of electrode was controlled to regulate the film thickness and the amount of Co(OH)₂ nano-flake on the titanium substrate. The film thickness was shown to reach the maximum value of 34 μm at -1.4 V of electrode potential, where 17.2 g of Co(OH)₂ was deposited on the substrate. The specific discharge capacitances were measured to be 226, 370, 720, and 1008 mF cm^{-2} in the 1st cycle corresponding to the films which were formed at -0.75, -1.0, -1.2, and -1.4 V of electrode potentials, respectively. Then the discharge capacities were decreased to be 206, 349, 586 and 866 mF/㎠, where the persistency rates were 91, 94, 81, and 86%, respectively.