• Journal of the Semiconductor & Display Technology
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• v.13 no.3
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• pp.21-25
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• 2014

The texturing is one of the most important processes for high efficiency crystalline silicon solar cells. The rear side flatness of silicon solar cell is very important for increasing the light reflectance and forming uniform back surface field(BSF) region in manufacturing high efficiency crystalline silicon solar cells. We investigated texturing difference between front and rear side of wafer by texturing of two adhered wafers. As a result, the flatter rear side was obtained by forming less pyramid size compared to the front side and improved reflectance of long wavelength and back surface field(BSF) region were also achieved. Therefore, the texturing of two adhered wafers can be expected to improve the efficiency of silicon solar cells due to increased short circuit current(Isc).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.2
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• pp.178-181
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• 2008

A solar cell based on dye-sensitized photoelectric conversion was studied by investigating the effects of the amount of polyethylene glycol(PEG), added to the $TiO_2$ paste, on surface morphology of the $TiO_2$ films and on the solar cell performance. Energy conversion efficiency was found to increase with PEG addition up to 20 % by weight of $TiO_2$ and then decrease with further addition due to the aggregation of $TiO_2$ nano particles in the $TiO_2$ film. In this study, the best result of dye-sensitized solar cell was the short circuit current(Isc) of $22.6mAcm^{-2}$, the open circuit voltage (Voc) of 0.73 V, the fill factor (ff) of 0.55 and the overall energy conversion efficiency (${\eta}$) of 9.1 % under illumination with AM 1.5 simulated sunlight.

• Journal of Environmental Science International
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• v.16 no.6
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• pp.715-723
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• 2007

The air pollutant emission is mainly caused by line sources in urban area. For example, the annually totaled air pollutant emission is known to consist of about 80% of line sources in Daegu. Hence, the appropriate assessment on the air pollutants of line sources is very important for the atmospheric environmental management in urban area. In this study, we made a comparative study to evaluate suitable dispersion model for estimating the air pollution from line sources. Two air pollution dispersion models, ISCST3 and CALINE4 were the subject of this study. The results were as follows; In the assessment of air pollution model, ISCST3 was found to have 4 times higher concentration than CALINE4. In addition, actual data obtained by measurement and estimated values by CALINE4 were generally identical. The air pollution assessment based on ISC3 model produced significantly lower values than actual data. The air pollution levels estimated by ISCST3 were very low in comparison with the observational values.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1990.10a
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• pp.88-90
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• 1990

In this study, PN junction solar cell and P$\^$+/-N-N$\^$+/ BSF solar cell, using N-type(111), 10$\^$16/[atoms/cm$\^$-3/] wafer, were fabricated applying that ion implant method whose dose are 1E14, 1E15, 3E15 and its acceleration energy is 50Key, 100Key respectively. The impurity concentration of two types of front-side are 10$\^$18/[atoms/cm$\^$-3/] and back-side concentration for BSF solar cell is 10$\^$17/[atoms/cm$\^$-3/]. As a result of comparison for 2 typical types of cells out of various fabricated samples, open circuit voltage (Voc), short circuit current(Isc) of BSF solar cell are larger than those of PN solar cell by 48[%], 14[%]. Considering that the efficiency of BSF cell is 2.5[%] as well as PN solar cell's is 7.5[%], 10.0[%] of efficiency improvement effect can be obtained from BSF solar cell. Futhermore, in consequence of front-side impurity concentration change from 10$\^$17/[atoms/cm$\^$-3] to 10$\^$20/[atoms/cm$\^$-3/] alternately, the most ideal result can be expected when it is 10$\^$18/[atoms/cm$\^$-3/].

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.335-335
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• 2007

염료감응형 태양전지(Dye-sensitized solar cells)용 페이스트의 제조시 바인더(binder)인 폴리에틸렌 글리콜(Polyethylene glycol; 이하 PEG)의 함량변화가 염료감응형 태양전지의 에너지 변환효율에 미치는 영향을 조사하고자 하였다. PEG의 함량변화는 0-30wt%까지 변화시켰으며 그들의 표면이나 단면의 형상을 FE-SEM, AFM으로 관찰 하였고, PEG 함량변화에 따른 열적특성은 TG/DTA 결과로 조사하였다. PEG의 양이 0%에서 20wt%까지 첨가되었을 때 단락전류밀도(Isc: Short current density)는 증가되어 나타났고 PEG가 30wt%가 첨가되었을 때는 오히려 감소하는 것을 확인할 수 있으며 이것은 $TiO_2$ 입자간의 응집현상이 과도하게 진행되어 전자의 흐름을 방해한 것으로 판단된다. PEG의 함량이 20wt% 첨가되었을 때 개방전압 (Voc: Open circuit voltage)이 0.73V, 단락전류밀도는 $22.6mA/cm^2$, 필펙터는 0.55, 에너지변환효율은 9.1%로 최적의 바인더 함량을 나타내었다. 염료감응형 태양전지의 광전극 제조시 PEG 바인더의 함량 변화에 따라 일자간의 응징특성이나 기공도와 같은 표면형상, 그리고 에너지변환효율을 변화시킨다는 것을 확인할 수 있었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.313.2-313.2
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• 2013

본 연구에서는 기존에 연구된 Solar Cell 보다 구조 및 제작이 단순한 $Al/Al_2O_3/Si$(100) Solar cell을 제작하여 평가하였다. 기판으로는 p-type Si(100), 0.5~2 ${\Omega}{\cdot}cm$을 사용하여 chemical cleaning 후 ALD(Atom Layer Deposition)법으로 Al2O3 터널링 절연막을 증착하였으며, 박막의 두께를 1~10 nm로 변화시켜 MIS 커패시터의 터널링 효과를 평가하였다. MIS 커패시터의 전기적 특성평가를 위해 누설전류 밀도-전계 특성은 pA meter/DC Voltage source를 사용하였고, 커패시턴스-전압특성, D-factor 특성은 precision LCR meter를 사용하였다. $Al/Al_2O_3/Si$(100) Solar cell의 특성평가를 위해 300~1100nm 파장영역에 따른 양자 효율을 평가하기 위해 Quantum Efficiency system (QE)을 사용하였고, Stanard Test Conditions 100 $mW/cm^2$, AM1.5, $25^{\circ}C$ 조건의 Voc, Isc, Jsc, FF (Fill Factor) 및 Efficiency(%)를 평가하기 위해 Solar simulator를 이용하였다.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.281-284
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• 2007

Recently, we have developed p-i-n a-Si:H single junction thin film solar cells with RF (13.56MHz) plasma enhanced chemical vapor deposition (PECVD) system, and also successfully fabricated the mini modules ($>300cm^2$), using the laser patterning technique to form an integrated series connection. The efficiency of a mini module was 7.4% ($Area=305cm^2$, Isc=0.25A, Voc=14.74V, FF=62%). To fabricate large area modules, it is important to optimise the integrated series connection, without damaging the cell. We have newly installed the laser patterning equipment that consists of two different lasers, $SHG-YVO_4$ (${\lambda}=0.532{\mu}m$) and YAG (${\lambda}=1.064{\mu}m$). The mini-modules are formed through several scribed lines such as pattern-l (front TCO), pattern-2 (PV layers) and pattern-3 (BR/back contact). However, in the case of pattern-3, a high-energy part of laser shot damaged the textured surface of the front TCO, so that the resistance between the each cells decreases due to an incomplete isolation. In this study, the re-deposition of SnOx from the front TCO, Zn (BR layer) and Al (back contact) on the sidewalls of pattern-3 scribed lines was observed. Moreover, re-crystallization of a-Si:H layers due to thermal damage by laser patterning was evaluated. These cause an increase of a leakage current, result in a low efficiency of module. To optimize a-Si:H single junction thin film modules, a laser beam profile was changed, and its effect on isolation of scribed lines is discussed in this paper.

• Journal of Korean Neurosurgical Society
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• v.62 no.6
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• pp.626-634
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• 2019

Objective : Nerve growth factor (NGF) is a member of the neurotrophic factor family and plays a vital role in the physiological processes of organisms, especially in the nervous system. Many recent studies have reported that NGF is also involved in the regulation of tumourigenesis by either promoting or suppressing tumor growth, which depends on the location and type of tumor. However, little is known regarding the effect of NGF on interspinal schwannoma (IS). In the present study, we aimed to explored whether mouse nerve growth factor (mNGF), which is widely used in the clinic, can influence the growth of interspinal schwannoma cells (ISCs) isolated from IS in vitro. Methods : ISCs were isolated, cultured and identified by S-100 with immunofluorescence analysis. S-100-positive cells were divided into five groups, and separately cultured with various concentrations of mNGF (0 [phosphate buffered saline, PBS], 40, 80, 160, and 320 ng/mL) for 24 hours. Western blot and quantantive real time polymerase chain reaction (PCR) were applied to detect tyrosine kinase A (TrkA) receptor and p75 neurotrophin receptor ($p75^{NTR}$) in each group. Crystal violet staining was selected to assess the effect of mNGF (160 ng/mL) on ISCs growth. Results : ISCs growth was enhanced by mNGF in a dose-dependent manner. The result of crystal violet staining revealed that it was significantly strengthened the cells growth kinetics when cultured with 160 ng/mL mNGF compared to PBS group. Western blot and quantantive real time PCR discovered that TrkA receptor and mRNA expression were both up-regualated under the condition of mNGF, expecially in 160 ng/mL, while the exoression of $p75^{NTR}$ demonstrated no difference among groups. Conclusion : From these data, we conclude that exogenous mNGF can facilitate ISC growth by activating both TrkA receptor and $p75^{NTR}$. In addition, patients who are suffering from IS should not be administered mNGF in the clinic.

• Journal of Power Electronics
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• v.17 no.2
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• pp.346-357
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• 2017

The Modular Multilevel Converter (MMC) is particularly attractive for medium and high power applications such as High-Voltage Direct Current (HVDC) systems. In order to reach a high voltage, the number of cascaded submodules (SMs) is generally very large. Thus, in the applications with hundreds or even thousands of SMs such as MMC-HVDCs, the sorting algorithm of the conventional voltage balancing strategy is extremely slow. This complicates the controller design and increases the hardware cost tremendously. This paper presents a Two-Way Merge Sort (TWMS) strategy based on the prediction of the capacitor voltages under ideal conditions. It also proposes an innovative Insertion Sort Correction for the TWMS (ISC-TWMS) to solve issues in practical engineering under non-ideal conditions. The proposed sorting methods are combined with the features of the MMC-HVDC control strategy, which significantly accelerates the sorting process and reduces the implementation efforts. In comparison with the commonly used quicksort algorithm, it saves at least two-thirds of the sorting execution time in one arm with 100 SMs, and saves more with a higher number of SMs. A 501-level MMC-HVDC simulation model in PSCAD/EMTDC has been built to verify the validity of the proposed strategies. The fast speed and high efficiency of the algorithms are demonstrated by experiments with a DSP controller (TMS320F28335).

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.11
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• pp.1535-1539
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• 2000

A sonic nozzle is used as a reference flow meter in the area of gas flow rate measurement. The critical pressure ratio of sonic nozzle is an important factor in maintaining its operating condition. ISO9300 suggested the critical pressure ratio of sonic nozzle as a function of area ratio. In this study, 13 sonic nozzles were made by the design of ISC9300 with different half diffuser angles of 2。 to 8。 and throat diameters of 0.28 to 4.48 mm. The test results of half diffuser angles below 8。 ar quite similar to those of ISO9300. On the other hand, the critical pressure ratio for the nozzle of 8。 decreases by 5.5% in comparison with ISO9300. However, ISO9300 does not predict the critical pressure ratio at lower Reynolds numbers than 10(sup)5. Therefore, it is found that it is a better way for the flow of low Reynolds number to express the critical pressure ratio of sonic nozzle as a function of Reynolds number than area ratios. A correlation equation of critical pressure is introduced with uncertainty $\pm$3.2 % at 95% confidence level.