• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.83.1-83.1
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• 2010

Hydrogenated a-SiGe middle cell for triple junction solar cell was investigated with various process parameters. a-SiGe I-layer was deposited at substrate temperature $245^{\circ}C$ and hydrogen content(R) was up to 26.7. Low optical bandgap(1.45eV) of a-SiGe cell was applied for middle cell although a-SiGe single cell efficiency with low Ge content was higher. And this cell was applied to the middle cell of a glass superstrate type a-Si/a-SiGe/uc-Si triple junction solar cell. The triple junction solar cell was resulted in the initial efficiency of about 9%, area $0.25cm^2$, under global AM 1.5 illumination.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.67.1-67.1
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• 2010

Triple junction solar cell을 위한 a-SiGe middle cell의 조건별 광학적 특성에 관한 연구를 실시하였다. a-SiGe I층은 GeH4 유량, 압력, H2 dilution ratio를 변화시켜 제조하였으며 전기적, 광학적 특성을 비교하여 최종적으로 선택된 조건을 triple junction solar cell에 적용하였다. a-SiGe I층은 Ge contents가 증가함에 따라 band gap은 감소하고 45% 이상의 조건에서는 700nm 전후 파장의 투과율이 감소하며, 압력이 감소함에 따라 band gap은 소폭 감소하나 700nm 전후 파장의 투과율은 증가하였다. 그리고 H2 ratio가 증가함에 따라 band gap은 소폭 감소하나 투과율에는 큰 변화가 없었다. 상기 결과를 바탕으로 최종적으로 선택된 조건에서 triple-junction solar cell을 제작하여 평가한 결과 초기 변환효율 9%의 결과를 얻었다.

• Current Photovoltaic Research
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• v.2 no.2
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• pp.41-47
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• 2014

Extensive investigation on silicon based thin film reveals a wide range of film characteristics, from low optical gap to high optical gap, from amorphous to micro-crystalline silicon etc. Fabrication of single junction, tandem and triple junction solar cell with suitable materials, indicate that fabrication of solar cell of a relatively moderate efficiency is possible with a better light induced stability. Due to these investigations, various competing materials like wide band gap silicon carbide and silicon oxide, low band gap micro-crystalline silicon and silicon germanium etc were also prepared and applied to the solar cells. Such a multi-junction solar cell can be a technologically promising photo-voltaic device, as the external quantum efficiency of such a cell covers a wider spectral range.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.64.1-64.1
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• 2011

다중접합 태양전지는 흡수대역이 다른 juntion으로 구성되어, 각각의 태양전지 간의 전류정합(current matching)이 효율 향상에 중요하다. 본 실험에서는 Top cell에 i-a-Si:H(Thinckness:100nm), Middle cell에는 i-a-SiGe:H(Thickness:800nm)을 적용하였고, bottom cell에는 i-${\mu}c$-Si:H(Thickness:1800nm), 수광부의 p-layer에 에 SiOx을 이용하여 triple juntion amorphous silicon solar cell(삼중접합태양전지)을 구현하였다. 이를 최적화 시키기 위해 ASA simulation을 이용하여 각 Cell의 intrinsic layer의 밴드갭을 가변하였다. 가변 결과 i-a-Si:H : 1.85 eV, i-a-SiGe:H: 1.6 eV, i-${\mu}c$-Si:H: 1.4 eV에서 태양전지 효율 14.5 %을 기록 하였다. 본 연구를 통해 Triple juntion cell에서의 intrinsic layer의 밴드갭 최적화를 구현해 볼 수 있었다.

• 한국태양에너지학회:학술대회논문집
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• 2011.04a
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• pp.269-274
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• 2011

A solar cell is primary parts to produce electrical energy from the Sun. And, we can utilize those solar cells as a power generation system in home, factory, and so on. In order to make proper power, the solar cells are configured in series and parallel lay down. In condition of uniform illumination, the solar array will produce an enough power by photovoltaic effects from the solar cells. In case of non-uniform illumination on the solar cells, the power will be dramatically decreased compared to design. Fortunately, there were so many research outputs regarding the illumination effects on solar array. In this work, we tried to find out the non-uniform effects on unit CPV solar cell, because there were no research outputs for unit CPV solar cell considering illumination. The CPV solar cell was used in CPV system to make a power by the Sun. We chosen the triple junction solar cell of GaAsInP2Ge for simulation, which has a 30 % of conversion efficiency. By simulation, we obtained the output performance of CPV solar cells in condition of various illumination by using Hamming Window function. Its performance was degraded by 10 % to 50 % depending illumination conditions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.12
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• pp.1057-1064
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• 2014

The satellite on geostationary orbit accommodates multiple payloads into a single spacecraft platform and launched in June 26, 2010. The electrical power required to the satellite during sunlight is generated by a solar array wing. The solar cells are the GaInP/GaAs/Ge Triple Junction cells named Gaget2 cells from RWE Space, which were based on a Spectrolab epitaxy. This paper evaluates solar array power performance at end of design life based on the trend analysis results for the flight data on geostationary orbit. The estimated solar array power performance at end of design life compares with the power performance provided by solar array manufacturer. The solar cells show nominal behavior without significant degradation through the trend analysis results.

• Current Photovoltaic Research
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• v.2 no.3
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• pp.95-102
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• 2014

Light trapping techniques can change the propagation direction of incident light and keep the light longer in the absorption layers of solar cells to enhance the power conversion efficiency. In thin film silicon (Si) solar cells, the thickness of absorption layer is generally not enough to absorb entire available photons because of short carrier life time, and light induced degradation effect, which can be compensated by the light trapping techniques. These techniques have been adopted as textured transparent conduction oxide (TCO) layers randomly or periodically textured, intermediate reflection layers of tandem and triple junction, and glass substrates etched by various patterning methods. We reviewed the light trapping techniques for thin film Si solar cells and mainly focused on the commercially available techniques applicable to textured TCO on patterned glass substrates. We described the characterization methods representing the light trapping effects, texturing of TCO and showed the results of multi-scale textured TCO on etched glass substrates. These methods can be used tandem and triple thin film Si solar cells to enhance photo-current and power conversion efficiency of long term stability.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.12
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• pp.1019-1025
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• 2021

In nearly all space environments, the solar cell degradation is dominated by protons[1]. Even through a GEO orbit lines in the electron radiation belts, the protons emitted from any solar event will still dominate the degradation[1]. Since COMS launch on June 26 2010, the proton events with the fluence of more than approximately 30 times the average level of perennial observations were observed between January 23 - 29 2012 and March 07 - 14 2012[16]. This paper studies the solar cell degradation by solar proton events in January and March 2012 for the open circuit voltage(Voc) of a witness cell and the short circuit current(Isc) of a section connected to a shunt switch. To evaluate the performance of solar cell, the flight data of voltage and current are corrected to the temperature, the Earth-Sun distance and the Sun angle and then compare with the solar cell characteristics at BOL. The Voc voltage dropped about 23.6mV compare after the March 2012 proton events to before the January 2012 proton events. The Voc voltage dropped less than 1% at BOL, which is 2575mV. The Isc current decreased negligible, as expected, in the March 2012 proton events.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.320-320
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• 2014

Amorphous silicon alloy (a-Si) solar cells and modules have been receiving a great deal of attention as a low-cost alternate energy source for large-scale terrestrial applications. Key to the achievement of high-efficiency solar cells using the multi-junction approach is the development of high quality, low band-gap materials which can capture the low-energy photons of the solar spectrum. Several cell designs have been reported in the past where grading or buffer layers have been incorporated at the junction interface to reduce carrier recombination near the junction. We have investigated profiling the composition of the a-SiGe alloy throughout the bulk of the intrinsic material so as to have a built-in electrical field in a substantial portion of the intrinsic material. As a result, the band gap mismatch between a-Si:H and $a-Si_{1-x}Ge_x:H$ creates a barrier for carrier transport. Previous reports have proposed a graded band gap structure in the absorber layer not only effectively increases the short wavelength absorption near the p/i interface, but also enhances the hole transport near the i-n interface. Here, we modulated the GeH4 flow rate to control the band gap to be graded from 1.75 eV (a-Si:H) to 1.55 eV ($a-Si_{1-x}Ge_x:H$). The band structure in the absorber layer thus became like a U-shape in which the lowest band gap was located in the middle of the i-layer. Incorporation of this structure in the middle and top cell of the triple-cell configuration is expected to increase the conversion efficiency further.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.584-587
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• 2006

An energy generating greenhouse based on fluoropolymer envelope and fresnel lens is proposed. The outstanding properties of the fluoropolymer films make them very suitable for large scale solar applications. Extremely high optical transmission over the whole solar spectrum, combined with mechanical strength, and durability allows us to design a highly optimized greenhouses for both plant growing and energy generation. Systems such as photovoltaic triple junction cells are especially attractive since they have up to 35% efficiency with much less cell material when the sun beam is focused with concentrators such as fresnel lenses. Cooling such devices will enhance the efficiency and provide useful thermal energy that could be further utilized for various applications depending on the local demands. This article introduces the basic ideas and principles of the energy generating greenhouses as a first step towards the actual deployment of such systems under Korean environment.