• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1999.11a
• /
• pp.553-556
• /
• 1999

This paper presents a proper condition to achieve above 19 % conversion efficiency using PC1D simulator. Cast poly-Si wafers with resistivity of 1 $\Omega$-cm and thickness of 250 ${\mu}{\textrm}{m}$ were used as a starting material. Various efficiency influencing parameters such as rear surface recombination velocity and minority carrier diffusion length in the base region, front surface recombination velocity, junction depth and doping concentration in the Emitter layer, BSF thickness and doping concentration were investigated. Optimized cell parameters were given as rear surface recombination of 1000 cm/s, minority carrier diffusion length in the base region 200 ${\mu}{\textrm}{m}$, front surface recombination velocity 100 cnt/s, sheet resistivity of emitter layer 100 $\Omega$/$\square$, BSF thickness 5 ${\mu}{\textrm}{m}$, doping concentration 5$\times$10$^{19}$ cm$^3$ . Among the investigated variables, we learn that a diffusion length of base layer acts as a key factor to achieve conversion efficiency higher than 19 %. Further details of simulation parameters and their effects to cell characteristics are discussed in this paper.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.07a
• /
• pp.83-84
• /
• 2005

생명체의 근육을 구성하는 근섬유와 마찬가지로 나노선 구동기는 불규칙적으로 엉켜있는 나노선들의 집합으로 이루어져 있으며, 기존의 강유전체에 기반을 둔 구동기에 비해 낮은 구동전압과 높은 일률을 가진다. 대표적인 나노선인 MWCNTs(Multi-walled Carbon Nanotubs)와 $V_2O_5$ 나노선을 이용한 구동기는 이미 각각 시현된 바 있으나, 이 둘의 이종접합을 통한 구동기는 아직까지 보고되지 않았다. 본 연구에서는 탄소나노튜브와 $V_2O_5$의 이종접합을 통해 필름 형태의 구동기를 구현하여 각각의 나노선 만을 이용했을 때보다 월등한 성능을 보여주는 구동기를 구현하였다. 향후 실용화 가능성을 염두에 두어, 보다 강건하고 최적화된 나노선 sheet의 합성과 구동기의 구조적 향상이 이루어진다면 그동안 알려진 그 어떤 물질보다도 우수한 구동특성을 보여줄 것이라 예상된다.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2000.02a
• /
• pp.93-93
• /
• 2000

수소화된 비정질 탄소(a-C:H)는 그 증착 조건에 따라서 여러 가지 다른 구조와 특성을 갖게 되며, 특히 DLC(diamond-like carbon) 및 CNT(Carbon nanotube)는 FED (field emission display) 개발 면에서 중요하게 연구되고 있다. 우리는 a-C:H 박막을 PECVD (plasma-enhanced chemical vapor deposition) 방법으로 증착하고 CH4 가스를 사용하였고 기판 온도는 상온-32$0^{\circ}C$ 사이에서 변화되었다. 기판은 Corning 1737 glass, quartz, Si, Ni 등을 사용하였다. 증착 압력과 R.F. power는 각각 0.1-1 Torr 와 12-60w 사이에서 변화되었다. ESR 측정은 X-band(주파수 약 9 GHz)에서 그리고 상온에서 행해졌다. 상온에서의 스핀밀도는 약한-표준피치(weak-pitch standard) 스펙트럼과 비교하여 얻을 수 있었다. 그리고 a-C:H 박막의 구조는 He-Ne laser(파장 632.8 nm)를 이용하는 micro-Raman spectroscopy로 분석하였다. 증착조건에 따른 스핀밀도의 변화 및 Raman 스펙트럼에서의 D-peak, G-peak의 위치 및 반치록, I(D)/I(G) 등을 조사하였다. 증착된 a-C:H 박막은 R.F.power가 증가할수록 대체로 스핀밀도가 증가하였으며, Raman 스펙트럼에서의 I(D)/I(G) 비율은 대체로 감소하였다. 증착된 박막들은 polymer-like Carbon으로 추정되었으며, 스핀밀도가 증가할수록 대체적으로 흑연 구조 영역이 증가됨을 알 수 있었다. 또한 glass나 Si 기판에 비해 Ni 기판위에서 polymer-like Carbon 구조는 향상되는 경향을 보였다.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.49-49
• /
• 2010

Nanopiezotronics is an emerging area of nanotechnology with a variety of applications that include piezoelectric field-effect transistors and diodes, self-powered nanogenerators and biosystems, and wireless nano/biosensors. By exploiting coupled piezoelectric and semiconducting characteristics, it is possible for nanowires, nanobelts, or nanorods to generate rectifying current and potential under external mechanical energies such as body movement (handling, winding, pushing, and bending) and muscle stretching, vibrations (acoustic and ultrasonic waves), and hydraulic forces (body fluid and blood flow). Fully transparent, flexible (TF) nanogenerators that are operated by external mechanical forces will be presented. By controlling the density of the seed layer for ZnO nanorod growth, transparent ZnO nanorod arrays were grown on ITO/PES films, and a TF conductive electrode was stacked on the ZnO nanorods. The resulting integrated TF nanodevice (having transparency exceeding 70 %) generated a noticeable current when it was pushed by application of an external load. The output current density was clearly dependent on the force applied. Furthermore, the output current density depended strongly on the morphology and the work function of the top electrode. ZnO nanorod-based nanogenerators with a PdAu, ITO, CNT, and graphene top electrodes gave output current densities of approximately $1-10\;uA/cm^2$ at a load of 0.9 kgf. Our results suggest that our TF nanogenerators are suitable for self-powered TF device applications such as flexible self-powered touch sensors, wearable artificial skins, fully rollable display mobile devices, and battery supplements for wearable cellular phones.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.08a
• /
• pp.168.1-168.1
• /
• 2013

고분자유기물로 사용되는 발광층에 탄소나노튜브를 합성하여 AC로 구동되는 고분자유기물소자를 제작하였다. 고분자유기물소자는 총 4개의 층(ITO/CRS/탄소나노튜브를 함유한 MEH-PPV/Al)으로 구성하였다. ITO가 코팅된 유리기판 위에 발광층을 보호하는 역할을 하는 절연층[cyanoethyl pullulan(CRS)], 유기발광물질인 poly[2-methoxy-5-(2-ethyl-hexyloxy)-1,4-phenylene-vinylene](MEH-PPV)에 탄소나노튜브의 함량을 조절하여 발광층으로 사용하였으며, 절연층과 발광층은 스핀코우터를 이용하여 증착하다. 마지막으로 thermal evaporator을 이용하여 Al을 증착하였다. 고분자유기물소자는 발광층에 함유된 탄소나노튜브에 함량에 따른 전압, 전류 그리고 밝기 특성을 분석하였다. 탄소나노튜브가 0.015wt% 함유된 고분자유기물소자에서 최대 밝기 특성과 낮은 소비전력을 얻을 수 있었다. 고분자유기물에 탄소나노튜브를 합성된 효과를 알아보기 위하여 임피던스분석을 통하여 고분자유기물소자의 저항, 캐패시턴스, 기생저항을 알아보았다. 고분자유기물소자의 캐패시턴스의 변화는 탄소나노튜브와 고분자 유기물(polymer-CNT matrix) 에서 생성되는 블록들이 매우 얇은 유전층을 구성할 것으로 예상되며 이는 micro-capacitance로 고분자유기물소자의 구동에 영향을 미치는 것으로 예상된다. AC구동 고분자유기물소자에 탄소나노튜브를 함유하여 높은 효율을 얻을 수 있는 장점으로 차세대 디스플레이나 조명으로 탄소나노튜브의 쓰임새를 기대해 본다.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.10a
• /
• pp.73-76
• /
• 2005

Carbon nanotubes (CNTs) have attracted an increasing attention due to their superior mechanical properties and potential application in industries. The strength of CNT has been predicted or calculated through several simulation techniques but actual experiments on stress-strain behavior are rare due to its dimensional limit, nanoscale positioning/manipulation, and instrumental resolution. We have attempted to observe straining responses of a multi-walled carbon nanotube (MWNT) by performing an in-situ tensile testing in a scanning electron microscope. The carbon nanotube, having its both ends attached on a cantilever force sensor and Y-shaped support, was elongated by a computer-controlled nanomanipulator. Linear deformation and fracture behaviors of MWNT were successfully observed and its force-displacement curve was also measured from the bending stiffness and displacement of the force sensor and manipulator.

• Steel and Composite Structures
• /
• v.24 no.6
• /
• pp.727-740
• /
• 2017

The present paper studies the stability analysis of the continuously graded CNT-Reinforced Composite (CNTRC) panel stiffened by rings and stringers. The Stiffened Panel (SP) subjected to axial and lateral loads is reinforced by agglomerated CNTs smoothly graded through the thickness. A two-parameter Eshelby-Mori-Tanaka (EMT) model is adopted to derive the effective material moduli of the CNTRC. The stability equations of the CNRTC SP are obtained by means of the adjacent equilibrium criterion. Notwithstanding most available literature in which the stiffener effects were smeared out over the respective stiffener spacing, in the present work, the stiffeners are modeled as Euler-Bernoulli beams. The Generalized Differential Quadrature Method (GDQM) is employed to discretize the stability equations. A numerical study is performed to investigate the influences of different types of parameters involved on the critical buckling of the SP reinforced by agglomerated CNTs. The results achieved reveal that continuously distributing of CNTs adjacent to the inner and outer panel's surface results in improving the stiffness of the SP and, as a consequence, inclining the critical buckling load. Furthermore, it has been concluded that the decline rate of buckling load intensity factor owing to the increase of the panel angle is significantly more sensible for the smaller values of panel angle.

• Structural Engineering and Mechanics
• /
• v.73 no.5
• /
• pp.555-563
• /
• 2020

The objective of present paper is assessment of dynamic buckling behavior of an embedded sandwich microplates in thermal environment in which the layers are reinforced through functionally graded carbon nanotubes (FG-CNTs). Therefore, mixture rule is taken into consideration for obtaining effective material characteristics. In order to model this structure much more realistic, Kelvin-Voigt model is presumed and the sandwich structure is rested on visco-Pasternak medium. Exponential shear deformation theory (ESDT) in addition to Eringen's nonlocal theory are utilized to obtain motion equations. Further, differential cubature method (DCM) as well as Bolotin's procedure are used to solve governing equations and achieve dynamic instability region (DIR) related to sandwich structure. Different parameters focusing on volume percent of CNTs, dispersion kinds of CNTs, thermal environment, small scale effect and structural damping and their influences upon the dynamic behavior of sandwich structure are investigated. So as to indicate the accuracy of applied theories as well as methods, the results are collated with another paper. According to results, presence of CNTs and their dispersion kind can alter system's dynamic response as well.

• Journal of Industrial and Engineering Chemistry
• /
• v.68
• /
• pp.387-392
• /
• 2018

Various technical approaches and concepts have been proposed to develop conductive super-hydrophobic (SH) surfaces. However, most of these approaches are not usable in practical applications because of insufficient adhesion and cost issues. Additionally, durability and uniformity issues are still in need of improvement. The goal of this research is to produce a large-area conductive SH surface with improved adhesion performance and uniformity. To this end, carbon nanotubes (CNT) with a high aspect ratio and elastomeric polymer were utilized as a conductive filler and matrix, respectively, to form a coating layer. Additionally, nanoscale silica particles were utilized for stable implementation of the conductive SH surface. To improve the adhesion properties between the SH coating layer and substrate, pretreatment of the substrate was conducted by utilizing both wet and dry etching processes to create specific organic functional groups on the substrate. Following pretreatment of the surface, a zirco-aluminate coupling agent was utilized to enhance adhesion properties between the substrate and the SH coating layer. Raman spectroscopy revealed that adhesion was greatly improved by the formation of a chemical bond between the substrate and the SH coating layer at an optimal coupling agent concentration. The developed conductive SH coating attained a high electromagnetic interference (EMI) shielding effectiveness, which is advantageous in self-cleaning EMI shielding applications.

• Korean Journal of Chemical Engineering
• /
• v.35 no.12
• /
• pp.2421-2429
• /
• 2018

Thiol-based self-assembled anchor linked to glucose oxidase (GOx) and gold nanoparticle (GNP) cluster is suggested to enhance the performance of glucose biosensor. By the adoption of thiol-based anchors, the activity of biocatalyst consisting of GOx, GNP, polyethyleneimine (PEI) and carbon nanotube (CNT) is improved because they play a crucial role in preventing the leaching out of GOx. They also promote electron collection and transfer, and this is due to a strong hydrophobic interaction between the active site of GOx and the aromatic ring of anchor, while the effect is optimized with the use of thiophenol anchor due to its simple configuration. Based on that, it is quantified that by the adoption of thiophenol as anchor, the current density of flavin adenine dinucleotide (FAD) redox reaction increases about 42%, electron transfer rate constant ($k_s$) is $9.1{\pm}0.1s^{-1}$ and the value is 26% higher than that of catalyst that does not use the anchor structure.