• Journal of the Microelectronics and Packaging Society
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• v.21 no.2
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• pp.1-11
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• 2014

Flexible transparent conductive electrodes (TCEs) have recently attracted a great deal of attention owing to rapid advances in flexible electronic devices, such as flexible displays, flexible photovoltanics, and e-papers. As the performance and reliability of flexible electronics are critically affected by the quality of TCE films, it is imperative to develop TCE films with low resistivity and high transparency as well as high flexibility. Indium tin oxide (ITO) has been the most dominant transparent conducting material due to its high optical transparency and electrical conductivity. However, ITO is susceptible to cracking and delamination when it is bent or deformed. Therefore, various types of flexible TCEs, such as carbon nanotube, conducting polymers, graphene, metal mesh, Ag nanowires (NWs), and metal mesh have been extensively investigated. Among several options to replace ITO film, Ag NWs and metal mesh have been suggested as the promising candidate for flexible TCEs. In this paper, we focused on Ag NWs and metal mesh, and summarized the current development status of Ag NWs and metal mesh. The several critical issues such as high contact resistance and haze are discussed, and newly developed technologies to resolve these issues are also presented. In particular, the flexibility and durability of Ag NWs and metal mesh was compared with ITO electrode.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.430.1-430.1
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• 2016

We present the concept of reducible fugitive material that conformally surrounds core Cu nanowire (NW) to fabricate transparent conducting electrode (TCE). Reducing atmosphere can corrodes/erodes the underlying/surrounding layers and might cause undesirable reactions such impurity doing and contamination, so that hydrogen-/forming gas based annealing is impractical to make device. In this regards, we introduce novel reducible shell conformally surrounding indivial CuNW to provide a protection against the oxidation when exposed to both air and solvent. Uniform copper lactate shell formation is readily achievable by injecting lactic acid to the CuNW dispersion as the acid reacts with the surface oxide/hydroxide or pure copper. Cu lactate shell prevents the core CuNW from the oxidation during the storage and/or film formation, so that the core-shell CuNW maintains without signficant oxidation for long time. Upon simple thermal annealing under vacuum or in nitrogen atmosphere, the Cu lactate shell is easily decomposed to pure Cu, providing an effective way to produce pure CuNW network TCE with typically sheet resistance of $19.8{\Omega}/sq$ and optical transmittance of 85.5% at 550 nm. Our reducible copper lactate core-shell Cu nanowires have the great advantage in fabrication of device such as composite transparent electrodes or solar cells.

• Korean Journal of Materials Research
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• v.30 no.6
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• pp.285-291
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• 2020

Recent advances in technology using ultra-thin noble metal film in oxide/metal/oxide structures have attracted attention because this material is a promising alternative to meet the needs of transparent conduction electrodes (TCE). AZO/Ag/AZO multilayer films are prepared by magnetron sputtering for Cu₂ZnSn(S,Se)₄ (CZTSSe) of kesterite solar cells. It is shown that the electrical and optical properties of the AZO/Ag/AZO multilayer films can be improved by the very low resistivity and surface plasmon effects due to the deposition of different thicknesses of Ag layer between oxide layers fixed at AZO 30 nm. The AZO/Ag/AZO multilayer films of Ag 15 nm show high mobility of 26.4 ㎠/Vs and low resistivity and sheet resistance of 3.58^⁎10^-5 Ωcm and 5.0 Ω/sq. Also, the AZO/Ag (15 nm)/AZO multilayer film shows relatively high transmittance of more than 65 % in the visible region. Through this, we fabricated CZTSSe thin film solar cells with 7.51 % efficiency by improving the short-circuit current density and fill factor to 27.7 mV/㎠ and 62 %, respectively.

• Journal of Powder Materials
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• v.24 no.6
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• pp.464-471
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• 2017

A metal mesh TCE film is fabricated using a series of processes such as UV imprinting of a transparent trench pattern (with a width of $2-5{\mu}m$) onto a PET film, filling it with silver paste, wiping of the surface, and heat-curing the silver paste. In this work nanosized (40-50 nm) silver particles are synthesized and mixed with submicron (250-300 nm)-sized silver particles to prepare silver paste for the fabrication of metal mesh-type TCE films. The filling of these silver pastes into the patterned trench layer is examined using a specially designed filling machine and the rheological testing of the silver pastes. The wiping of the trench layer surface to remove any residual silver paste or particles is tested with various mixture solvents, and ethyl cellosolve acetate (ECA):DI water = 90:10 wt% is found to give the best result. The silver paste with 40-50 nm Ag:250-300 nm Ag in a 10:90 wt% mixture gives the highest electrical conductance. The metal mesh TCE film obtained with this silver paste in an optimized process exhibits a light transmittance of 90.4% and haze at 1.2%, which is suitable for TSP application.

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

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.201.1-201.1
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• 2014

본 연구에서는 Slot die coating 공법으로 코팅된 Poly (3-4 ethylenedioxythiophene): Poly (styrenesulfonate) (PEDOT:PSS) 박막과 비정질 ITO 박막의 전기적, 광학적, 기계적 특성을 비교 평가하여 Slot die coating 공법으로 코팅된 PEDOT:PSS 박막의 유기태양전지의 전극으로서의 적용가능성을 확인하였다. 상업용 PEDOT:PSS 박막은 보통 280 Ohm/sq.의 면저항과 가시광 영역에서 약 80%의 광투과도를 나타내며, 비정질 ITO 박막과 유사한 전기적, 광학적 특성을 나타내었다. Slot die coating 공법을 통해 제작된 PEDOT:PSS 투명 전극과 비정질 ITO 투명 전극의 기판 휘어짐에 따른 전기적 안정성을 비교 평가하기 위해 25 mm에서 1 mm까지 radius 변화에 따른 저항의 변화를 측정하였다. 그 결과, 비정질 ITO 투명 전극 대비 PEDOT:PSS 투명 전극이 더 우수한 전기적 안정성을 나타냄을 확인하였다. 또한, 다양한 Bending test (Inner/Outer bending, Rolling, Stretching, Twisting) 를 통해 비정질 ITO 투명 전극 보다 Slot die coating 공법으로 코팅된 PEDOT:PSS 투명 전극의 우수한 기계적 특성을 확인하였다. 이를 바탕으로 Flexible 유기태양전지에의 적용 가능성을 알아보기 위해 Slot die coating 공법으로 코팅된 PEDOT:PSS 투명 전극과 비정질 ITO 투명 전극을 유기태양전지의 anode 층에 적용하여 각각 제작하고 그 특성을 평가하였다. 비정질 ITO 투명 박막을 적용한 유기태양전지 대비 Slot die coating 공법으로 코팅된 PEDOT:PSS 투명 박막으로 제작한 유기태양전지에서 더 높은 효율이 나타났으며, 이로써 Slot die coating 공법으로 코팅된 PEDOT:PSS 투명 전극의 Flexible 유기태양전지로써의 적용 가능성을 확인하였다.