Flexible and Mechanically Robust Organic Light-Emitting Diodes Based on Photopatternable Silver Nanowire Electrodes

Kang, Hyungseok,Kang, Iljoong,Han, Jaehun,Kim, Jun Beom,Lee, Dong Yun,Cho, Sung Min,Cho, Jeong Ho American Chemical Society 2016 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.120 No.38

<P>We developed a simple methodology for fabricating silver nanowire (AgNW) micropattems on a plastic substrate using a photocurable polymer. The patterning method began with the lamination of a UV-curable prepolymer film onto the AgNW-coated rigid glass substrate. Selective UV exposure of the UV-curable prepolymer film through a photomask solidified the exposed regions, and the unexposed regions were simply removed by the solvent. AgNW micropattems of various sizes and shapes could be readily formed across the entire plastic substrate. Importantly, this photopatterning process enabled the embedding of the AgNW structures into the polymer matrix, which dramatically reduced the surface roughness and enhanced the mechanical stability of the AgNW film. The AgNW structures served as transparent anode electrodes in organic light-emitting diodes (OLEDs) that performed well compared to OLEDs fabricated using conventional indium tin oxide (ITO) or conducting polymer electrodes. This simple, inexpensive, and scalable AgNW patterning technique provides a novel approach to realizing next-generation flexible electronics.</P>

Epitaxial-Growth-Induced Junction Welding of Silver Nanowire Network Electrodes

Kang, Hyungseok,Song, Sol-Ji,Sul, Young Eun,An, Byeong-Seon,Yin, Zhenxing,Choi, Yongsuk,Pu, Lyongsun,Yang, Cheol-Woong,Kim, Youn Sang,Cho, Sung Min,Kim, Jung-Gu,Cho, Jeong Ho American Chemical Society 2018 ACS NANO Vol.12 No.5

<P>In this study, we developed a roll-to-roll Ag electroplating process for metallic nanowire electrodes using a galvanostatic mode. Electroplating is a low-cost and facile method for deposition of metal onto a target surface with precise control of both the composition and the thickness. Metallic nanowire networks [silver nanowires (AgNWs) and copper nanowires (CuNWs)] coated onto a polyethylene terephthalate (PET) film were immersed directly in an electroplating bath containing AgNO<SUB>3</SUB>. Solvated silver ions (Ag<SUP>+</SUP> ions) were deposited onto the nanowire surface through application of a constant current <I>via</I> an external circuit between the nanowire networks (cathode) and a Ag plate (anode). The amount of electroplated Ag was systematically controlled by changing both the applied current density and the electroplating time, which enabled precise control of the sheet resistance and optical transmittance of the metallic nanowire networks. The optimized Ag-electroplated AgNW (Ag-AgNW) films exhibited a sheet resistance of ∼19 Ω/sq at an optical transmittance of 90% (550 nm). A transmission electron microscopy study confirmed that Ag grew epitaxially on the AgNW surface, but a polycrystalline Ag structure was formed on the CuNW surface. The Ag-electroplated metallic nanowire electrodes were successfully applied to various electronic devices such as organic light-emitting diodes, triboelectric nanogenerators, and a resistive touch panel. The proposed roll-to-roll Ag electroplating process provides a simple, low-cost, and scalable method for the fabrication of enhanced transparent conductive electrode materials for next-generation electronic devices.</P> [FIG OMISSION]</BR>

Halide Welding for Silver Nanowire Network Electrode

Kang, Hyungseok,Kim, Yeontae,Cheon, Siuk,Yi, Gi-Ra,Cho, Jeong Ho American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.36

<P>We developed a method of chemically welding silver nanowires (AgNWs) using an aqueous solution containing sodium halide salts (NaF, NaCl; NaBr, or NaI). The halide welding was performed simply by immersing the as-coated AgNW film into the sodium halide solution, and the resulting material was compared with those obtained using two typical thermal and plasmonic welding techniques. The halide welding dramatically reduced the sheet resistance of the AgNW electrode because of the strong fusion among nanowires at each junction while preserving the optical transmittance. The dramatic decrease in the sheet resistance was attributed to the autocatalytic addition of dissolved silver ions to the nanowire junction. Unlike thermal and plasmonic welding methods, the halide welding could be applied to AgNW films with a variety of deposition densities because the halide ions uniformly contacted the surface or junction regions. The optimized AgNW electrodes exhibited a sheet resistance of 9.3 Omega/sq at an optical transmittance of 92%. The halide welding significantly enhanced the mechanical flexibility of the electrode compared with the as coated AgNWs. The halide-welded AgNWs were successfully used as source drain electrodes in a transparent and flexible organic field-effect transistor (OFET). This simple, low-cost, and low-power consumption halide welding technique provides an innovative approach to preparing transparent electrodes for use in next-generation flexible optoelectronic devices.</P>

Automatic Registration between EO and IR Images of KOMPSAT-3A Using Block-based Image Matching

Hyungseok Kang 대한원격탐사학회 2020 大韓遠隔探査學會誌 Vol.36 No.4

This paper focuses on automatic image registration between EO (Electro-Optical) and IR (InfraRed) satellite images with different spectral properties using block-based approach and simple preprocessing technique to enhance the performance of feature matching. If unpreprocessed EO and IR images from Kompsat-3A satellite were applied to local feature matching algorithms (Scale Invariant Feature Transform, Speed-Up Robust Feature, etc.), image registration algorithm generally failed because of few detected feature points or mismatched pairs despite of many detected feature points. In this paper, we proposed a new image registration method which improved the performance of feature matching with block-based registration process on 9-divided image and pre-processing technique based on adaptive histogram equalization. The proposed method showed better performance than without our proposed technique on visual inspection and I-RMSE. This study can be used for automatic image registration between various images acquired from different sensors.

Triboelectric Nanogenerators Using Robust Silver Nanowires Network

Hyungseok Kang,Han Kim,Seongsu Kim,Hyeon Jin Shin,Siuk Cheon,Ji-Hyeok Huh,Dong Yun Lee,Seungwoo Lee,Sang-Woo Kim,Jeong Ho Cho 한국고분자학회 2016 한국고분자학회 학술대회 연구논문 초록집 Vol.41 No.2

Electroplated core–shell nanowire network electrodes for highly efficient organic light-emitting diodes

Kang Hyungseok,Kim Joo Sung,최석열,Kim Young-Hoon,김도환,김정구,이태우,Cho Jeong Ho 나노기술연구협의회 2022 Nano Convergence Vol.9 No.1

In this study, we performed metal (Ag, Ni, Cu, or Pd) electroplating of core–shell metallic Ag nanowire (AgNW) networks intended for use as the anode electrode in organic light-emitting diodes (OLEDs) to modify the work function (WF) and conductivity of the AgNW networks. This low-cost and facile electroplating method enabled the precise deposition of metal onto the AgNW surface and at the nanowire (NW) junctions. AgNWs coated onto a transparent glass substrate were immersed in four different metal electroplating baths: those containing AgNO3 for Ag electroplating, NiSO4 for Ni electroplating, Cu2P2O7 for Cu electroplating, and PdCl2 for Pd electroplating. The solvated metal ions (Ag+, Ni2+, Cu2+, and Pd2+) in the respective electroplating baths were reduced to the corresponding metals on the AgNW surface in the galvanostatic mode under a constant electric current achieved by linear sweep voltammetry via an external circuit between the AgNW networks (cathode) and a Pt mesh (anode). The amount of electroplated metal was systematically controlled by varying the electroplating time. Scanning electron microscopy images showed that the four different metals (shells) were successfully electroplated on the AgNWs (core), and the nanosize-controlled electroplating process produced metal NWs with varying diameters, conductivities, optical transmittances, and WFs. The metal-electroplated AgNWs were successfully employed as the anode electrodes of the OLEDs. This facile and low-cost method of metal electroplating of AgNWs to increase their WFs and conductivities is a promising development for the fabrication of next-generation OLEDs.

텍스트 영상에서의 디포커스 블러 제거

강형석(Hyungseok Kang),이승용(Seungyong Lee) 한국정보과학회 2014 한국정보과학회 학술발표논문집 Vol.2014 No.12

추정된 전력 손실 지수를 활용하는 비콘 노드 기반의 위치 검출 알고리즘

강형서(Hyungseok Kang),안태준(Taejune An),구인수(Insoo Koo) 대한전기학회 2010 정보 및 제어 심포지엄 논문집 Vol.2010 No.4

현재 센서 네트워크 시스템(Sensor Network system)에서 중요시 되고 있는 기술 중에 하나는 위치 측정이다. 위치 측정 기술에서 가장 중요한 부분은 위치 측정의 정확성과 위치 측정을 위해 소모되는 에너지의 절약이다. 많은 논문에서는 이동 노드 기반의 위치 측정을 수행함으로써 이동노드의 에너지 소모 측면에서 비효율적인 단점이 있다. 이에 본 논문에서 는 전력 손실 지수(?)를 먼저 추정하고 추정된 전력 손실 지수를 활용하여, 비콘 노드 중심으로 이동 노드의 위치를 순차적으로 개선하는 위치 검출 알고리즘을 제안하다. 제안된 알고리즘은 무선채널 환경에 강인한 위치 측정 정확도 및 이동노드에 의한 에너지 소모 감소를 동시에 제공한다.

2차원 축소확대노즐의 추력편향특성 수치해석연구

강형석(Hyungseok Kang),최성만(Seongman choi),오성환(Seonghwan Oh) 한국추진공학회 2012 한국추진공학회 학술대회논문집 Vol.2012 No.11

본 수치해석 연구는 초음속 항공기에 적용되는 이차원 축소-확대 노즐의 기계적인 피치 편향각 변화에 따른 추력편향노즐의 특성을 이해 하고자 수행 되었다. 수치해석은 Fluent를 이용하여 진행되었으며 해석결과는 동일한 조건에서의 실험결과와 비교검토 하였다. 노즐의 피치 편향각은 0° 와 20°로 각각 설정하였으며 피치 플랩의 길이를 노즐 출구 높이의 0.5배에서 2.5배까지 설정하여 피치플랩의 길이에 따른 편향효율과 유동특성을 분석하였다. 연구결과 피치플랩의 길이에 따라 피치추력의 변화가 크게 나타났으며, 이러한 피치추력변화는 피치플랩 길이비의 변화에 따라 노즐 내부에서 발생하는 충격파의 상호간섭현상에 의해 좌우됨을 알 수 있었다. A numerical analysis has been conducted to determine the pitch thrust vectoring characteristics of a two-dimensional convergent divergent exhaust nozzle for supersonic aircraft application. The numerical analysis was done by Fluent and verified by the experimental test result. The analysis was performed with pitch angle of 0° and 20° each at the ambient temperature condition. To see the effect of a ratio of pitch flap length and pitch flap height, the ratio was varied from 0.5 to 2.5. The numerical analysis show that pitch thrust is changed much with pitch flap length. The big differences of the pitch thrust with pitch flap length is due to the shock interaction in the nozzle.

Effect of thiophenol-based ligands on photoluminescence of quantum dot nanocrystals

Hyungseok Moon,Hoseok Jin,Bokyoung Kim,Hyunjin Kang,Daekyoung Kim,Heeyeop Chae 한국진공학회 2016 한국진공학회 학술발표회초록집 Vol.2016 No.2