• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.10
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• pp.652-657
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• 2015

We have investigated the properties of Al-doped ZnO (AZO) thin films as functions of atomic layer deposition (ALD) oxidants. AZO transparent conducting oxides (TCOs) layer was deposited by ALD with adding trimethylaluminum (TMA) and diethylzinc (DEZn). AZO films were deposited at low temperature with $H_2O$ and $O_3$ as oxidants. Electrical, optical and structural properties of AZO thin films were investigated by 4-point probe, Hall effect measurement, UV-VIS, and AFM. Microstructure and atomic bonding states were investigated by HRXRD and XPS. The resistivity of AZO films grown using $H_2O$ was lower than the films grown using $H_2O$ and $O_3$, by approximately two orders of magnitude. The differences in oxygen vacancy peak intensity of AZO films were correlated to the optical and electrical properties.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.458.1-458.1
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• 2014

An effective light-managing structure has been achieved by using a nano-imprint method. A transparent conductor of indium-tin-oxide (ITO) was periodically nanodome-shaped to have a height of 200 nm with a diameter of 340 nm on a p-type Si substrate. This spontaneously formed a heterojunction between the ITO layer and Si substrate and effectively reduced the light-reflection. The ITO nanodome device response was significantly enhanced to 6010 from the value of 72.9 of a planar ITO film. The transparent conducting ITO nanodome structure efficiently manipulates the incident light driving into the light-absorber and can be applied in various photoelectric applications.

• Transactions on Electrical and Electronic Materials
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• v.17 no.1
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• pp.18-20
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• 2016

Transparent and conducting IGZO thin films were deposited by RF magnetron sputtering on thin Cu coated glass substrates to investigate the effect of a Cu buffer layer on the structural, optical, and electrical film properties. Although X-ray diffraction (XRD) analysis revealed that both the IGZO single layer and IGZO/Cu bi-layered films were in the amorphous phase, the IGZO/Cu films showed a lower resistivity of 5.7×10⁻⁴ Ωcm due to the increased mobility and high carrier concentration. The decreased optical transmittance of the IGZO/Cu films was also attributed to a one order of magnitude higher carrier concentration than the IGZO films. From the observed results, the thin Cu layer is postulated to be an effective buffer film that can enhance the opto-electrical performance of the IGZO films in transparent thin film transistors.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.6
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• pp.408-411
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• 2018

We fabricated highly flexible Mn-doped $SnO_2$ (MTO)/Ag/MTO/polydimethylsiloxane (PDMS)/MTO multilayer transparent conducting films. To reduce refractive-index mismatching of the MTO/Ag/MTO/polyethylene terephthalate (PET), index-matching layers were inserted between the oxide-metal-oxide-structured films and the PET substrate. The PDMS layer was deposited by spin-coating after adjusting the mixing ratio of PDMS and hexane. We investigated the effects of the index-matching layer on the color and reflectance differences with different PDMS dilution ratios. As the dilution ratio increased from 1:100 to 1:130, the color difference increased slightly, while the reflectance difference decreased from 0.62 to 0.32. The MTO/Ag/MTO/PDMS/MTO film showed a transmittance of 87.18~87.68% at 550 nm. The highest value of the Haacke figure of merit was $47.54{\times}10^{-3}{\Omega}^{-1}$ for the dilution ratio of 1:130.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.159-159
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• 2008

투명전도체 (transparent conducting oxides: TCOs) 는 일반적으로 $10^3\Omega^{-1}Cm^{-1}$의 전도도, 가시광 영역에서 80%이상의 투명성을 가지는 재료로서, 액정 박막 표시 장치(TFT-LCD), 광기전성 소자, 유기 발광 소자, 에너지 절약 창문, 태양전지(sollar cell) 등 전극으로 사용되고 있다. 최근에는 TCO의 전도도특성을 조절하여 반도성특성을 가진 투명 산화물 반도체(transparent oxide semiconductor: TOS) 을 이용한 박막 트랜지스터 연구가 활발히 진행 중이다. 기존의 실리콘을 기반으로 하는 박막 트랜지스터의 낮은 이동도, 불투명성의 특성을 가지고 있지만, 산화물 박막트랜지스터는 높은 이동도를 발현 할 수 있을 뿐만 아니라, 넓은 밴드갭 에너지를 갖는 산화물을 이용하므로 투명한 특성도 발현 할 수 있어 차세대 디스플레이의 구동소자로서 응용연구가 되고 있다. 이에 본 연구에서는 박막트랜지스터 channel layer로서의 Indium-Tin-Zinc oxide 적용특성을 조사하였다. Indium, Tin, Zinc 의 혼합비율을 다양하게 조절하여 타겟을 제작하였다. 이를 RF magnetron sputtering 를 이용하여 박막으로 성장시켰으며, 기판으로는 glass 기판을 사용하였다. 박막 성장시 아르곤과 산소의 비율을 다양하게 조절하였다. 성장시킨 박막은 Hall effect, Transmittance, Work function, XRD등을 이용하여 전기적, 광학적, 구조특성을 평가하였다. Indium-Tin-Zinc Oxide(ITZO) 을 channel layer로 사용하여 Thin-film transistor 을 제작하여, TFT의 I-V 및 stability특성을 평가하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.278.2-278.2
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• 2014

We have investigated the highly flexible and transparent Si-doped $In_2O_3$(ISO)/Ag/ISO multilayer grown on polyethylene terephthalate (PET) substrates using a roll-to-roll sputtering system. The electrical and optical properties of ISO/Ag/ISO multilayer electrodes depended on the insertion of a nano-size Ag layer. Due to the high conductivity of a nano-size Ag layer, the optimized ISO/Ag/ISO multilayer electrodes showed the lowest resistivity of $3.679{\times}10^{-5}Ohm-cm$, even though the ISO/Ag/ISO multilayer electrodes was sputtered at room temperature. Furthermore, the ISO/Ag/ISO multilayer electrodes exhibited a high transmittance of 86.33%, because of the anti-reflection effect, comparable to Sn-doped $In_2O_3$ (ITO) electrodes. In addition, the ISO/Ag/ISO multilayer electrodes had a very smooth surface morphology without surface defects and showed good flexibility. The flexible OSCs fabricated on ISO(30nm)/Ag(8nm)/ISO(30nm) multilayer electrode showed a power conversion efficiency of 3.272%. This result indicates that the ISO/Ag/ISO multilayer is a promising transparent conducting electrode for flexible OSCs.

• Bulletin of the Korean Chemical Society
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• v.35 no.7
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• pp.1985-1988
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• 2014

$Cu_2ZnSnSe_4$ (CZTSe) thin films were synthesized on transparent conducting oxide glass substrates via a simple, non-toxic, and low-cost process using a precursor solution paste. A three-step heating process (oxidation, sulfurization, and selenization) was employed to synthesize a CZTSe thin film as an absorber layer for use in thin-film solar cells. In particular, we focused on the effects of sulfurization conditions on CZTSe film formation. We found that sulfurization at $400^{\circ}C$ involves the formation of secondary phases such as $CuSe_2$ and $Cu_2SnSe_3$, but they gradually disappeared when the temperature was increased. The formed CZTSe thin films showed homogenous and good crystallinity with grain sizes of approximately 600 nm. A solar cell device was tentatively fabricated and showed a power conversion efficiency of 2.2% on an active area of 0.44 $cm^2$ with an open circuit voltage of 365 mV, a short current density of 20.6 $mA/cm^2$, and a fill factor of 28.7%.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.69.1-69.1
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• 2010

We have fabricated organic photovoltaic cells (OPVs) with highly conductive poly 3,4-ethylenedioxythiophene : poly styrenesulfonate (PEDOT:PSS) layer as an anode without using transparent conducting oxide (TCO), which has been modified by adding some organic solvents like sorbitol (So), dimethyl sulfoxide (DMSO), N-methyl-pyrrolidone (NMP), dimethylformamide (DMF), and ethylene glycol (EG). The conductivity of PEDOT:PSS film modified with each additive was enhanced by three orders of magnitude. According to atomic force microscopy (AFM) study, conductivity enhancement might be related to better connections between the conducting PEDOT chains. TCO-free solar cells with modified PEDOT:PSS layer and the active layer composed of poly(3-hexylthiophene) (P3HT) and phenyl [6,6] C61 butyric acid methyl ester (PCBM) exhibited a comparable device performance to indium tin oxide (ITO) based organic solar cells. The power conversion efficiency (PCE) of the organic solar cells incorporating DMSO, So + DMSO and EG modified PEDOT:PSS layer reached 3.51, 3.64 and 3.77%, respectively, under illumination of AM 1.5 (100mW/$cm^2$).

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.590-590
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• 2012

A transparent conducting oxide (TCO) layer was applied in crystalline Si (c-Si) solar cells without use of the conventional SiNx-coating. A high quality indium-tin-oxide (ITO) layer was directly deposited on an emitter layer of a Si wafer. Three different types of emitters were formed by controlling the phosphorous diffusion condition. A light-doped emitter forming a thinner emitter junction showed an improved photoconversion efficiency of 14.1% comparing to 13.2% of a heavy-doped emitter. This was induced by lower recombination within a narrower depletion region of the light-doped emitter. In the aspect of light management, the intermediate refractive index of ITO is effective to reduce the light reflection leading the enhanced carrier generation in a Si absorber. For the electrical aspect, the ITO layer serves as an efficient electrical conductor and thus relieves the burden of high contact resistance of the light-doped emitter. Additionally, the ITO works as a buffer layer of Ag and Si and certainly prevents the shunting problem of Ag penetration into Si emitter region. It discusses an efficient design scheme of TCO-embedded emitter Si solar cells.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.12
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• pp.2014-2018
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• 2016

Transparent, conductive electrode films, showing the particular characteristics of good conductivity and high transparency, are of considerable research interest because of their potential for use in opto-electronic applications, such as smart window, photovoltaic cells and flat panel displays. Multilayer transparent electrodes, having a much lower electrical resistance than widely-used transparent conducting oxide electrodes, were prepared by using RF/DC magnetron sputtering system. The multilayer structure consisted of three layers, [NiInZnO(NIZO)/Ag/NIZO]. The optical and electrical properties of the multilayered NIZO/Ag/NIZO structure were investigated in relation to the thickness of each layer. The optical and electrical characteristics of multilayer structures have been investigated as a function of the Ag and NIZO film thickness. High-quality transparent conductive films have been obtained, with sheet resistance of $9.8{\Omega}/sq$ for Ag film thickness of 8 nm. Also the multilayer films of inserted Ag 8 nm thickness showed a high optical transmittance above 93% in the visible range. The electrical and optical properties of the new multilayer films were mainly dependent on the thickness of Ag insertion layer.