• Journal of international Conference on Electrical Machines and Systems
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• 제1권4호
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• pp.483-491
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• 2012

It is expected that, in the future, DC power service will be widely used for photovoltaic home power generation systems, since DC consuming devices are ever increasing. Instead of using multiple converters to convert DC to AC and then AC to DC, the power service could solely be based on DC. This would eliminate the need for converters, reducing the cost, complexity, and possibly increasing the efficiency. However, configuration of direct DC power service with mechanical contacts can cause spark voltage or an electric shock when the switch is turned on and off. To solve these problems, in this paper, a contactless power supply for a DC power service that can transfer electric power produced by photovoltaics to the home electric system using magnetic coupling instead of mechanical contacts has been proposed. The proposed system consists of a ZVS boost converter, a half-bridge LLC resonant converter, and a contactless transformer. This proposed contactless system eliminates the use of DC switches. To reduce the stress and loss of the boost converter switching devices, a lossless snubber with coupled inductor is applied. In this paper, a switching frequency control technique using the contactless voltage sensing circuit is also proposed and implemented for the output voltage control instead of using additional power regulators. Finally, a prototype consisted of 150W boost converter has been designed and built to demonstrate the feasibility of the proposed contactless photovoltaic DC power service. Experimental results show that 74~83% overall system efficiency is obtained for the 10W~80W load.

• Current Photovoltaic Research
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• 제7권4호
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• pp.111-120
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• 2019

The output power of a crystalline silicon (c-Si) photovoltaic (PV) module is not directly the sum of the powers of its unit cells. There are several losses and gain mechanisms that reduce the total output power when solar cells are encapsulated into solar modules. Theses factors are getting high attention as the high cell efficiency achievement become more complex and expensive. More research works are involved to minimize the "cell-to-module" (CTM) loss. Our paper is aimed to focus on electrical losses due to interconnection and mismatch loss at PV modules. Research study shows that among all reasons of PV module failure 40.7% fails at interconnection. The mismatch loss in modern PV modules is very low (nearly 0.1%) but still lacks in the approach that determines all the contributing factors in mismatch loss. This review paper is related to study of interconnection loss technologies and key factors contributing to mismatch loss during module fabrication. Also, the improved interconnection technologies, understanding the approaches to mitigate the mismatch loss factors are precisely described here. This research study will give the approach of mitigating the loss and enable improvement in reliability of PV modules.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.76.1-76.1
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• 2015

Optical resonances of metallic or dielectric nanoantennas enable to effectively convert free-propagating electromagnetic waves to localized electromagnetic fields and vice versa. Plasmonic resonances of metal nanoantennas extremely modify the local density of optical states beyond the optical diffraction limit and thus facilitate highly-efficient light-emitting, nonlinear signal conversion, photovoltaics, and optical trapping. The leaky-mode resonances, or termed Mie resonances, allow dielectric nanoantennas to have a compact size even less than the wavelength scale. The dielectric nanoantennas exhibiting low optical losses and supporting both electric and magnetic resonances provide an alternative to their metallic counterparts. To extend the utility of metal and dielectric nanoantennas in further applications, e.g. metasurfaces and metamaterials, it is required to understand and engineer their scattering characteristics. At first, we characterize resonant plasmonic antenna radiations of a single-crystalline Ag nanowire over a wide spectral range from visible to near infrared regions. Dark-field optical microscope and direct far-field scanning measurements successfully identify the FP resonances and mode matching conditions of the antenna radiation, and reveal the mutual relation between the SPP dispersion and the far-field antenna radiation. Secondly, we perform a systematical study on resonant scattering properties of high-refractive-index dielectric nanoantennas. In this research, we examined Si nanoblock and electron-beam induced deposition (EBID) carbonaceous nanorod structures. Scattering spectra of the transverse-electric (TE) and transverse-magnetic (TM) leaky-mode resonances are measured by dark-field microscope spectroscopy. The leaky-mode resonances result a large scattering cross section approaching the theoretical single-channel scattering limit, and their wide tuning ranges enable vivid structural color generation over the full visible spectrum range from blue to green, yellow, and red. In particular, the lowest-order TM01 mode overcomes the diffraction limit. The finite-difference time-domain method and modal dispersion model successfully reproduce the experimental results.

• 대한기계학회논문집B
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• 제36권10호
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• pp.1049-1054
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• 2012

유기전자재료의 발전으로 박막화, 유연화, 경량화가 가능하면서, 저가의 생산비용으로 제조 될 수 있는 유기반도체의 개발 및 상용화에 대한 연구가 활발히 이루어지고 있다. 하지만, 유기반도체를 구성하는 유기재료 및 전극재료가 미량의 수분과 반응으로 성능이 저하되는 문제로 상용화의 큰 걸림돌이 되고 있다. 따라서 유기재료 및 전극을 동작환경의 수분으로부터 보호할 수 있는 고성능 투습 방지막 개발에 대한 연구가 많이 진행되고 있다. 본 연구에서는 $SiO_x$/parylene 및 $SiN_x$/parylene 구조를 이용한 다중 구조의 고성능 박막 봉지막을 개발하고, 개발된 박막을 Ca-corrosion test를 이용하여 수분투과율을 측정하였다. 또한 박막 봉지재를 유기태양전지에 적용하여 유기태양전지의 수명과 투습특성과의 관계를 확인하였다.

• 공업화학
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• 제26권5호
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• pp.526-532
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• 2015

신 기후변화대응(Post 2020)을 위한 대체에너지의 역할과 더불어 태양전지의 중요성이 높아져 가고 있다. 태양전지의 종류는 크게 재료관점에서 보면 유기물과 무기물 계열로 구분할 수 있지만 대규모 발전역할에서는 현재까지 실리콘과 같이 양산성과 안정성 기반의 무기물 태양전지가 주된 역할을 하고 있다. 특히 최근 몇 년간 화합물반도체 태양전지에 대한 연구는 급속도로 가속화되면서 3-5족 적층형 태양전지, chalcopyrite 계열 $CuInGa(S,Se)_2$ (CIGSSe) 태양전지와 kesterite 계열 $Cu_2ZnSn(S,Se)_4$ (CZTSSe) 태양전지 연구가 대표적으로 주류를 이루어 왔다. 따라서 화합물반도체 태양전지에서 주류를 이루고 있는 3-5족 적층형, CIGSSe 및 CZTSSe 태양전지들의 연구개발동향 및 기술적인 주요내용들에 대해 소개하고자 한다.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2016년도 추계학술대회 논문집
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• pp.181-181
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• 2016

Hydrogenated microcrystalline silicon (${\mu}c-Si:H$) films have attracted much attention as materials of the bottom-cells in Si thin film tandem photovoltaics due to their low bandgap and excellent stability against light soaking. However, in PECVD, the source gas $SiH_4$ must be highly diluted by $H_2$, which eventually results in low deposition rate. Moreover, it is known that high-rate ${\mu}c-Si:H$ growth is usually accompanied by a large number of dangling-bond (DB) defects in the resulting films, which act as recombination centers for photoexcited carriers, leading to a deterioration in the device performance. During film deposition, Si nanoparticles generated in $SiH_4$ discharges can be incorporated into films, and such incorporation may have effects on film properties depending on the size, structure, and volume fraction of nanoparticles incorporated into films. Here we report experimental results on the effects of nonoparticles incorporation at the different substrate temperature studied using a multi-hollow discharge plasma CVD method in which such incorporation can be significantly suppressed in upstream region by setting the gas flow velocity high enough to drive nanoparticles toward the downstream region. All experiments were performed with the multi-hollow discharge plasma CVD reactor at RT, 100, and $250^{\circ}C$, respectively. The gas flow rate ratio of $SiH_4$ to $H_2$ was 0.997. The total gas pressure P was kept at 2 Torr. The discharge frequency and power were 60 MHz, 180 W, respectively. Crystallinity Xc of resulting films was evaluated using Raman spectra. The defect densities of the films were measured with electron spin resonance (ESR). The defect density of fims deposited in the downstream region (with nonoparticles) is higher defect density than that in the upstream region (without nanoparticles) at low substrate temperature of RT and $100^{\circ}C$. This result indicates that nanoparticle incorporation can change considerably their film properties depending on the substrate temperature.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 추계학술발표대회
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• pp.35.1-35.1
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• 2011

New photovoltaic (PV) materials and manufacturing approaches are needed for meeting the demand for lower-cost solar cells. The prototypal thin-film photovoltaic absorbers (CdTe and $Cu(In,Ga)Se_2$) can achieve solar conversion efficiencies of up to 20% and are now commercially available, but the presence of toxic (Cd,Se) and expensive elemental components (In, Te) is a real issue as the demand for photovoltaics rapidly increases. To overcome these limitations, there has been substantial interest in developing viable alternative materials, such as $Cu_2ZnSnS_4$ (CZTS) is an emerging solar absorber that is structurally similar to CIGS, but contains only earth abundant, non-toxic elements and has a near optimal direct band gap energy of 1.4~1.6 ev and a large absorption coefficient of ${\sim}10^4\;cm^{-1}$. The CZTS absorber layers are grown and investigated by various fabrication methods, such as thermal evaporation, e-beam evaporation with a post sulfurization, sputtering, non-vacuum sol-gel, pulsed laser, spray-pyrolysis method and electrodeposition technique. In the present work, we report an alternative method for large area deposition of CZTS thin films that is potentially high throughput and inexpensive when used to produce monolithically integrated solar panel modules. Specifically, we have developed an aqueous chemical approach based on chemical bath deposition (CBD) with a subsequent sulfurization heat treatment. Samples produced by our method were analyzed by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, absorbance and photoluminescence. The results show that this inexpensive and relatively benign process produces thin films of CZTS exhibiting uniform composition, kesterite crystal structure, and good optical properties. A preliminary solar cell device was fabricated to demonstrate rectifying and photovoltaic behavior.

• 한국실천공학교육학회논문지
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• 제3권2호
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• pp.75-82
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• 2011

최근들어 화석 연료의 고갈, 지구 온난화등의 문제들로 인해, 녹색성장 기술이 중요시 되고 있다. 에너지 문제와 녹색성장 기술이 융합된 신성장동력 확보를 위해 풍력, 태양광, 연료전지, 바이오 연료등에 많이 투자가 확대되고 있다. 그 중 풍력발전은 다른 에너지에 비해 경제성이 높고, 유해물질의 배출이 거의 없다. 따라서 최근 정부나 기업들에서도 많은 비용을 투자하여 풍력 기술 개발에 적극적인 지원을 하고 있지만, 풍력 기술을 선도하는 해외 선진국들에 비해서 국내에서의 관련 교육과 장비는 연구소 수준에 머물고 있다. 그러므로 관련 산업에서 요구하는 기본 기술의 저변화와 기술적 향상을 위해 실제 산업에서 적용하고 있는 시스템과 유사한 자비와 교육과정의 개발이 필요한 실정이다. 본 논문에서는 실험을 통하여 풍력터빈제어의 이론적인 내용을 수강생들이 보다 쉽게 이해할 수 있도록 교육용 풍력터빈제어 실습장치를 개발하고 교육효과를 알아보았다. 개발된 실습장치를 소개하고, 각각의 실습장치를 소개한다. 마지막으로 설문조사를 통하여 반응도 평가를 통한 교육효과를 검증하였다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.33-36
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• 2009

고효율 양자점 태양전지를 위하여 $Si_{1-x}C_x$ 박막 내에 Si 양자점을 형성한 박막을 제작하고 그 특성을 분석하였다. $Si_{1-x}C_x$ 박막은 Si과 C target을 co-sputtering하여 증착하였다. C target의 RF power를 변화시켜 $Si_{1-x}C_x$ 박막의 조성비를 조절하였으며, 조성비는 auger electron spectroscopy로 정량적으로 측정하였다. 이 박막들을 질소 분위기에서 후 열처리하여 high resolution transmittance electron microscopy로 확인한 결과 박막 내에 2~10nm 크기의 양자점이 형성된 것을 관측할 수 있었다. 이 양자점은 transmittance electron diffraction과 grazing incident X-ray diffraction을 통해 Si 양자점과 SiC 양자점이 형성되었음을 알 수 있었다. Raman 측정 결과에서는 후 열처리한 $Si_{1-x}C_x$ 박막의 조성비가 증가할 수록 crystal Si peak의 shift가 증가함을 알 수 있었고, 이를 통해 양자점의 크기도 함께 계산할 수 있었다. Fourier transform infrared spectroscopy을 통해 후 열처리한 Si1-xCx 박막의 양자점의 형성 원인을 추정하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.226-226
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• 2013

Si is a dominant solar material, which is the second most abundant element in the earth giving a benefit in the aspect in cost with low toxicity. However, the inherent limit of Si has an indirect band gap of 1.1 eV resulting in the limited optical absorption. Therefore, a critical issue has been raised to increase the utilization of the incident light into the Si absorber. The enhancement of light absorption is a crucial to improve the performances and thus relieves the cost burden of Si photovoltaics. For the optical aspect, an efficient design of a front surface, where the incident light comes in, has been intensively investigated to improve the performance of photon absorption. Lambertian light trapping can be attained when the light active surface is ideally rough to increase the optical length by about 50 compared to a planar substrate. This suggests that an efficient design may reduce thickness of the Si absorber from the conventional 100~300 ${\mu}m$ to less than 3 ${\mu}m$. Theoretically, a hole-array structure satisfies an equivalent efficiency of c-Si with only one-twelfth mass and one-sixth thickness. Various approaches have been applied to improve the incident light utilization in a Si absorber using textured structures, periodic gratings, photonic crystals, and nanorod arrays. We have designed hole and pillar structured Si absorbers. Four-different Si absorbers have been simultaneously fabricated on an identical Si wafer with hole arrays or pillar arrays at a fixed depth of 2 ${\mu}m$. We have found that the significant enhanced solar cell performances both for the hole arrayed and pillar arrayed Si absorbers compared to that of a planar Si wafer resulting from the effective improvement in the quantum efficiencies.