• Proceedings of the KIEE Conference
• /
• 2011.07a
• /
• pp.1485-1486
• /
• 2011

A layer of $TiO_2$ thin film less than ~500nm in thickness, as a blocking layer, was coated by sol-gel method directly onto the anode electrode to be isolated from the electrolyte in dye-sensitized solar cells (DSCs). This is to prevent the electrons from back-transferring from the electrode to the electrolyte (I-/I3-). The effects of heat treatment conditions of the gel and as-coated film on the thickness and consolidation to substrate were studied. The flexible DSCs were fabricated with working electrode of Ti thin foil coated with blocking $TiO_2$ layer, dye-attached mesoporous $TiO_2$ film, gel electrolyte and counter electrode of Pt-deposited indium doped tin oxide/polyethylene naphthalate (ITO/PEN). The photo-current conversion efficiency of the cell was 5.3% ($V_{oc}=0.678V$, $J_{sc}=12.181mA/cm^2$, ff=0.634) under AM1.5, 100 mW/$cm^2$ illumination.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.24 no.1
• /
• pp.94-97
• /
• 2015

In this study, we introduce a yellowing phenomenon in silver nanowire laser patterning and attempt to understand the cause of this phenomenon. Silver nanowire is a promising alternative to indium tin oxide as a transparent electrode owing to its flexibility. Additionally, silver nanowire can be easily patterned by laser ablation, which is free of dangerous chemicals. However, a yellowish color change reducing visibility is observed on the patterned area of the silver nanowires, and this yellowing phenomenon prevents the use of silver nanowire as a transparent electrode material. We concluded that resolidified debris of melted and evaporated silver nanowires after laser ablation causes the color change of the electrode. Further research is needed to determine a means of mitigating this yellowing phenomenon.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.19 no.8
• /
• pp.724-731
• /
• 2006

We investigated the electrochemical properties for Langmuir-Blodgett (LB) films mixed with 4-octyl-4'-(5-carboxylpentamethyleneoxy)azobenzene (denoted as 8A5H) and phospholipid(L-a-dimyristoylphosphatidylcholine, denoted as DMPC and L-a-dilauroylphosphayidylcholine, denoted as DLPC). The LB films of 8A5H, 8A5H-DMPC and 8A5H-DLPC mixture monolayers were deposited by using the LB method on the indium tin oxide(ITO) glass. The electrochemical properties measured by using cyclic voltammetry with a three-electrode system, an Ag/AgCl reference electrode, a platinum wire counter electrode and LB film-coated ITO working electrode at various concentrations(0.1, 0.5, and 1.0 mol/L) of $NaClO_4$ solution. A measuring range was reduced from initial potential to -1350 mV, continuously oxidized to 1650 mV and measured to the initial point. The scan rates were 50, 100, 150 and 200 mV/s, respectively. As a result, LB films of 8A5H and 8A5H-DLPC mixture monolayers appeared irreversible process caused by only the oxidation current from the cyclic voltammogram and LB films of 8A5H-DMPC monolayer mixture was found to be caused by a reversible oxidation-reduction process.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.653-653
• /
• 2013

In this study, ITO extended gate reduced graphene oxide field effect transistor (rGO FET) was demonstrated as a transducer for a proton sensing application. In this structure, the sensing area is isolated from the active area of the device. Therefore, it is easy to deposit or modify the sensing area without affecting on the device performance. In this case, the ITO extended gate was used as a gate electrode as well as a proton sensing material. The proton sensing properties based on the rGO FET transducer were analyzed. The rGO FET device showed a high stability in the air ambient with a TTC encapsulation layer for months. The device showed an ambipolar characteristic with the Dirac point shift with varying the pH solutions. The sensing characteristics have offered the potential for the ion sensing application.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2015.08a
• /
• pp.237.1-237.1
• /
• 2015

OLED의 낮은 외부 광자 효율 문제를 해결하기 위해서는 발광층은 물론 전극 재료에 대한 연구가 함께 진행되어야 한다. 최근 플렉서블 디스플레이(Flexible Display) 분야에서 투명전극(Transparent Electrode)은 큰 주목을 받고 있다. 기존 전자소자의 투명전극으로는 인듐산화물(ITO, Indium Tin Oxide)이 널리 사용되어 왔으나, ITO의 주원료인 인듐(Indium)은 희소성으로 인해 앞으로 30년 후에 고갈될 것으로 예상되어 ITO를 대체할만한 투명전극 재료가 필요하게 되었다. 인듐이 포함되지 않은(Indium-free) 투명전극을 개발하려는 많은 연구들이 진행 중인데, 본 연구에서는 PEN(Polyethylene Naphthalate) 유연기판 상에 그래핀(Graphene)을 투명전극으로 구현하여 OLED의 효율을 높이는데 이용하고자 하였다. 화학 기상 증착(CVD, Chemical Vapor Deposition) 방법을 이용하여 Cu 호일 위에 그래핀을 성장시킨 후 PEN 유연기판에 전사하여 그래핀 투명전극을 구현하면서 그래핀 성장층을 단층 또는 다층으로 구분하여 성장시켜 각각의 투명전극을 구현해보았다. 유연기판 상의 그래핀의 상태를 확인하기 위해 라만 분광(Raman Spectroscopy) 분석을 이용하여 그래핀 고유의 라만 꼭지점(Raman peak)인 G 꼭지점(G peak: 1580 cm-1), 2D 꼭지점(2D peak: ~2700 cm-1)을 확인하였는데 그래핀 전사 상태가 양호하여 D 꼭지점(D peak: ~1360 cm-1)은 나타나지 않았다. 원자힘 현미경(AFM, Atomic Force Microscope) 분석을 통해 다층 및 단층 그래핀 표면의 거칠기(Roughness) 및 두께(Thickness)를 각각 확인할 수 있었고 자외선-가시광선 분광법(UV-Visible Spectroscopy) 분석으로 그래핀 투명전극과 유연기판의 투과도(Transmittance)를 분석하였으며, 단층 그래핀 투과도가 90%수준의 높은 값이 나타나 ITO보다 개선됨을 확인하였다. 그래핀 면저항은 TLM(Transmission Line Measurement)법을 통해 측정하였는데, 단층 그래핀의 경우 $800{\Omega}/{\square}$ 내외 수준임을 확인할 수 있었다. 본 연구에서는 근자외선 영역에서 높은 투과도와 우수한 전기적 특성을 가지는 그래핀 투명 전도성 전극 구조를 제안하고, 나아가 가시영역에서 ITO를 대체할 수 있는 투명 전도성 전극 물질을 개발함으로써 발광다이오드의 광효율을 높일 수 있는 투명 전도성 전극을 구현하였다.

• Rapid Communication in Photoscience
• /
• v.2 no.3
• /
• pp.79-81
• /
• 2013

A novel method of fabricating polythiophene-gold nanoparticle composite film electrodes for photoelectric conversion is demonstrated. The method includes electrodeposition of gold and electropolymerization of 2,2'-bithiophene onto an indium-tin-oxide (ITO) electrode. First, electrodeposition of gold onto the ITO electrode was carried out with various repetition times of pulsed applied potential (0.25 s at -2.0 V vs. Ag/AgCl) in an aqueous solution of $HAuCl_4$. Significant progress of the number density of deposited gold nanoparticles was confirmed from scanning electron micrographs, from 4 (1 time) to 25% (15 times). Next, electropolymerization of 2,2'-bithiophene onto the above ITO electrode was performed under controlled charge condition (+1.4 V vs. Ag wire, 15 $mC/cm^2$). Structural characterization of as-fabricated films were carried out by spectroscopic and electron micrographic methods. Photocurrent responses from the sample film electrodes were investigated in the presence of electron acceptors (methyl viologen and oxygen). Photocurrent intensities increased with increasing the density of deposited gold nanoparticles up to ~10%, and tended to decrease above it. It suggests that the surplus gold nanoparticles exhibit quenching effects rather than enhancement effects based on localized electric fields induced by surface plasmon resonance of the deposited gold nanoparticles.

• Journal of the Semiconductor & Display Technology
• /
• v.14 no.3
• /
• pp.33-36
• /
• 2015

It has increased several decades in the field of Indium Tin Oxide (ITO) transparent thin film, However, a major problem with this ITO thin film application is high cost compared with other transparent thin film materials[1]. So far, in order to overcome this disadvantage, we show that a transparent ITO/Ag/i-ZnO multilayer thin film electrode would be more cost-effective and it has not only highly transparent but also conductive properties. The aim of this research has therefore been to try and establish how ITO/Ag/i-ZnO multilayer thin film would be more effective than ITO thin film. Herein, we report the properties of ITO/Ag/i-ZnO multilayer thin film by using optical spectroscopic method and measuring sheet resistance. At a certain total thickness of thin film, sheet resistance of ITO/Ag/i-ZnO multilayer was drastically decreased than ITO layer approximately $40{\Omega}/{\Box}$ at same visible light transmittance. (minimal point $5.2{\Omega}/{\Box}$). Tendency, which shows lowly sheet resistive in a certain transmittance, has been observed, hence, it should be suitable for transparent electrode device.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.299-299
• /
• 2013

Indium Tin Oxide (ITO) has widely been used as a transparent conductive oxide (TCE) for photovoltaic devices. Lately, flexibility of ITO becomes an issue as demand of flexible device increases. Several scientists have tried to substitute ITO to different materials such as conductive polymer, graphene, CNT, and metal nanowire because of ITO brittleness. Among the substitute materials, PEDOT:PSS has mostly paid attention because PEDOT:PSS has excellent flexibility and good conductivity. The conductivity of PEDOT:PSS increases up to 1000 S/cm with additives such as DMSO, EG, sorbitol, and so on. In our research group, we introduce a conductive polymer PEDOT:PSS as a buffer layer to improve not only flexibility but also conductivity. As PEDOT:PSS layer forms beneath ITO thin film (20 nm), sheet resistance decreases from $230{\Omega}$/${\Box}$ to $85{\Omega}$/${\Box}$ and crack initiation decreases from 4.5 mm to 3.5 mm as well. We have fabricated organic photovoltaic device and power conversion efficiencies using conventional ITO electrode and ITO/PEDOT:PSS hybrid electrode. The photovoltaic property such as power conversion efficiency for ITO/PEDOT:PSS hybrid electrode is comparable to the value obtained using conventional ITO electrode on glass substrate.

• Journal of Sensor Science and Technology
• /
• v.31 no.2
• /
• pp.90-95
• /
• 2022

The effect of the structure of an ITO nanoparticle film sensor on its performance was studied. A printed ITO film (P-ITO film) was fabricated on a flexible polyethylene terephthalate (PET) substrate, and the contact resistance of the electrode and sensor response change were clarified according to the detection position. The contact resistance between Ag and P-ITO was observed to be -204.4 Ω using the transmission line method (TLM), confirming that a very good ohmic contact is possible. In addition, we confirmed that the contact position of the analyte had a significant influence on the response of the sensor. Based on these results, the performance of the four types of sensors was compared. Consequently, we observed that 1) optimizing the resistance of the printed film, 2) optimizing the electrode structure and analyte input position, and 3) optimizing the electrode area are very important for fabricating a metal oxide nanoparticle (MONP) sensor with optimal performance.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.29 no.4
• /
• pp.277-284
• /
• 2018

This paper reports the transparent electrode, which would be applied to transparent displays and smart glasses. Herein, a squared metal mesh with the most widely used copper wire in microwaves is studied for the alternating thin-film-type transparent and conducting indium tin oxide(ITO), with a low conductivity(sheet resistance > $5{\Omega}/sq.$). The electromagnetic performance of a patch antenna with metal mesh is analyzed. This paper presents the results of the optical(OT, optical transparent) and electrical(sheet resistance) characteristics of a squared metal mesh, which is a basic design. To improve the OT, copper wire(w=0.2 mm) is used in fabricating the squared metal mesh and the relationship between the OT and the antenna performance(radiation gain, radiation pattern) was analyzed according to the mesh size(l=1, 2 mm). The measurement results show that the antenna performance and the optical characteristic are in inverse proportion to each other. In real applications, the optical and electrical characteristics, and the costs of production are to be considered.