• 전기화학회지
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• 제14권4호
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• pp.196-200
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• 2011

본 연구에서는 니오븀 산화물을 비교적 저온에서 단시간 동안의 양극산화법을 통해 제조하였다. 이때, 전해질로는 NaF와 HF를 혼합하여 사용하였으며, 20~120 V의 다양한 전압 조건에 따라 생성되는 니오븀 산화물의 미세구조를 관찰하였다. 일반적으로 니오븀 금속의 양극산화 시 초기에 생성된 니오븀 산화물은 무정형 구조이나 반응이 경과함에 따라 점차 결정형 산화물로 성장하게 된다. 이러한 산화물은 XRD 분석을 통하여 결정형의 $Nb_2O_5$ 임을 확인하였고, FE-SEM 분석결과, 그 표면은 매우 밀집된 형태의 나노로드로 이루어진 마이크로콘 산화물임을 알 수 있었다. 적절한 공정변수로 제조된 니오븀 산화물은 마이크로콘 구조 전체 표면에 걸쳐 동일한 크기를 갖는 나노로드 다발을 형성하고 있으며, 이러한 나노 구조는 또한 넓은 표면적을 기대할 수 있어 염료감응 태양전지나 바이오 소재 등에 대한 다양한 분야에 응용될 수 있을 것으로 기대된다.

• 한국재료학회지
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• 제29권3호
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• pp.183-188
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• 2019

Flexible dye-sensitized solar cells using binder free $TiO_2$ paste for low temperature sintering are developed. In this paste a small amount of titanium gel is added to a paste of $TiO_2$ nanoparticle. Analysis of titanium gel paste prepared at $150^{\circ}C$ shows that it has a pure anatase phase in XRD and mesoporous structure in SEM. The formation of the titanium gel 1-2 nm coated layer is confirmed by comparing the TEM image analysis of the titanium gel paste and the pristine paste. This coating layer improves the excited electron transfer and electrical contact between particles. The J-V curves of the organic binder DSSCs fabricated at $150^{\circ}C$ shows a current density of $0.12mA/cm^2$ and an open-circuit voltage of 0.47 V, while the titanium gel DSSCs improves electrical characteristics to $5.04mA/cm^2$ and 0.74 V. As a result, the photoelectric conversion efficiency of the organic binder DSSC prepared at low temperature is as low as 0.02 %, but the titanium gel paste DSSCs has a measured effciency of 2.76 %.

• 한국재료학회지
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• 제24권10호
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• pp.565-571
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• 2014

Nitrogen-doped ZnO nanoparticle-carbon nanofiber composites were prepared using electrospinning. As the relative amounts of N-doped ZnO nanoparticles in the composites were controlled to levels of 3.4, 9.6, and 13.8 wt%, the morphological, structural, and chemical properties of the composites were characterized by means of field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). In particular, the carbon nanofiber composites containing 13.8 wt% N-doped ZnO nanoparticles exhibited superior catalytic properties, making them suitable for use as counter electrodes in dye-sensitized solar cells (DSSCs). This result can be attributed to the enhanced surface roughness of the composites, which offers sites for $I_3{^-}$ ion reductions and the formation of Zn3N2 phases that facilitate electron transfer. Therefore, DSSCs fabricated with 13.8 wt% N-doped ZnO nanoparticle-carbon nanofiber composites showed high current density ($16.3mA/cm^2$), high fill factor (57.8%), and excellent power-conversion efficiency (6.69%); at the same time, these DSSCs displayed power-conversion efficiency almost identical to that of DSSCs fabricated with a pure Pt counter electrode (6.57%).

• 대한기계학회논문집A
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• 제39권9호
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• pp.947-954
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• 2015

염료감응형 태양전지용 플렉시블 필름에 도포된 코팅물질의 균질한 코팅은 제품의 성능과 내구성과 매우 밀접한 관계가 있고, 균질한 코팅은 열풍건조로 노즐에서의 균일한 온도분포와 질량유량에 의해 얻어질 수 있다. 본 연구에서 열풍건조로의 성능향상에 영향을 주는 다양한 인자들에 대한 수치해석을 수행함으로써 열풍건조로 출구의 균일한 온도분포와 질량유량을 얻고자 하였다. 수치해석 모델은 유동방정식과 에너지방정식으로 구성되었고, 수치해석을 모델의 검증을 위해 수치해석 결과값과 실험결과를 비교하였다. 연구결과로서 열풍건조로의 타공판이 균일한 온도분포 및 질량유량에 큰 영향을 미친다는 것을 알 수 있었다.

• 공업화학
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• 제21권4호
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• pp.405-410
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• 2010

P25와 Dyesol $TiO_2$ (Titanium dioxide)를 사용하여 두께와 소성 온도가 다른 전극을 제조하여 염료감응형 태양전지(Dye Sensitized Solar Cell, DSSC)를 제조한 후 광 변환 효율을 측정하였다. 소성 전 후의 $TiO_2$ 작업 전극의 두께 변화는 FE-SEM을 사용하여 시편의 cross section을 확인하여 비교하였다. 또한 상대전극인 Pt의 소성 온도에 따른 DSSC의 효율 변화도 측정하였다. P25를 활용한 DSSC는 doctor blade로 1층으로 도포 후, $500^{\circ}C$에서 30 min 동안 소성한 작업 전극(${\sim}20.4{\mu}m$)과 $350^{\circ}C$에서 30 min 동안 소성한 Pt 상대 전극으로 제조한 셀이 3.8%의 광효율을 나타내었다. Dyesol $TiO_2$를 활용하여 1층으로 도포 후, $500^{\circ}C$에서 30 min 동안 소성한 작업전극(${\sim}9.1\;{\mu}m$)과 $450^{\circ}C$에서 30 min 동안 소성한 Pt 상대 전극으로 제조한 셀이 5.8%의 광 효율을 나타냄을 알았다.

• 한국재료학회지
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• 제26권5호
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• pp.250-257
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• 2016

Octahedral $Co_3O_4$/carbon nanofiber (CNF) composites are fabricated using electrospinning and hydrothermal methods. Their morphological characteristics, chemical bonding states, and electrochemical properties are used to demonstrate the improved photovoltaic properties of the samples. Octahedral $Co_3O_4$ grown on CNFs is based on metallic Co nanoparticles acting as seeds in the CNFs, which seeds are directly related to the high performance of DSSCs. The octahedral $Co_3O_4$/CNFs composites exhibit high photocurrent density ($12.73mA/m^2$), superb fill factor (62.1 %), and excellent power conversion efficiency (5.61 %) compared to those characteristics of commercial $Co_3O_4$, conventional CNFs, and metallic Co-seed/CNFs. These results can be described as stemmnig from the synergistic effect of the porous and graphitized matrix formed by catalytic graphitization using the metal cobalt catalyst on CNFs, which leads to an increase in the catalytic activity for the reduction of triiodide ions. Therefore, octahedral $Co_3O_4$/CNFs composites can be used as a counter electrode for Pt-free dye-sensitized solar cells.

• 한국재료학회지
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• 제26권8호
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• pp.401-405
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• 2016

The cobalt silicides were investigated for employment as a catalytic layer for a DSSC. Using an E-gun evaporation process, we prepared a sample of 100 nm-thick cobalt on a p-type Si (100) wafer. To form cobalt silicides, the samples were annealed at temperatures of $300^{\circ}C$, $500^{\circ}C$, and $700^{\circ}C$ for 30 minutes in a vacuum. Four-point probe, XRD, FE-SEM, and CV analyses were used to determine the sheet resistance, phase, microstructure, and catalytic activity of the cobalt silicides. To confirm the corrosion stability, we also checked the microstructure change of the cobalt silicides after dipping into iodide electrolyte. Through the sheet resistance and XRD results, we determined that $Co_2Si$, CoSi, and $CoSi_2$ were formed successfully by annealing at $300^{\circ}C$, $500^{\circ}C$, and $700^{\circ}C$, respectively. The microstructure analysis results showed that all the cobalt silicides were formed uniformly, and CoSi and $CoSi_2$ layers were very stable even after dipping in the iodide electrolyte. The CV result showed that CoSi and $CoSi_2$ exhibit catalytic activities 67 % and 54 % that of Pt. Our results for $Co_2Si$, CoSi, and $CoSi_2$ revealed that CoSi and $CoSi_2$ could be employed as catalyst for a DSSC.

• 전기학회논문지
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• 제59권12호
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• pp.2218-2224
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• 2010

Dye-sensitized solar cell (DSC) is a promising alternative solar cell to the conventional silicon solar cell due to several advantages. Development of large scale module is necessary to commercialize the DSC in the near future. A scribing technology of the transparent conductive oxide (TCO) is one of the important technologies on the fabrication of DSC module. A quality of the scribed line on the TCO has a decisive effect on the efficiency of DSC module. Among several scribing technologies, the fiber laser is a suitable for scribing the TCO more precisely and accurately because of their own characteristics. In this study, we try to improve the quality of the TCO scribed line by using the fiber laser. Consequently, the operating parameter of fiber laser is optimized to get the TCO scribed line with good quality. And the fiber laser scribing technology of the TCO is applied to the fabrication of the DSC with optimal operating parameter, operating current 3900mA. As a result, the current density and fill factor are improved and the total efficiency is increased because the internal resistances of DSC such as TCO sheet resistance and the resistance concerned to the electron movement in the $TiO_2$ are reduced. This is analyzed by the electrochemistry impedance spectroscopy (EIS) and the equivalent circuit model of the DSC.

• 한국전기전자재료학회논문지
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• 제17권3호
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• pp.323-328
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• 2004

Down-conversion of Eu$^{3+}$ doped LiGdF$_4$ (LGF) for increasing the cell efficiency on dye-sensitized Ti $O_2$ solar cells has been studied. The dye sensitized solar cell (DSC) consisting of mesoporous Ti $O_2$ electrode deposited on transparent substrate, an electrolyte containing I$^{[-10]}$ /I$_3$$^{[-10]}$ redox couple, and Pt counter electrode is a promising alternative to the inorganic solar cell. The structure of DSC is basically a sandwich type, viz., FTO glass/Ru-red dye-absorbed Ti $O_2$/iodine electrolyte/sputtered Pt/FTO glass. The cell without down converter had open circuit potential of approximately 0.66 Volt, the short circuit photocurrent density of 1.632 mA/$\textrm{cm}^2$, and fill factor of about 50 ％ at the excitation wavelength of 550 nm. In addition, 5.6 mW/$\textrm{cm}^2$ incident light intensity beam was used as a light source. From this result, the calculated monochromatic efficiency at the wavelength of 550 nm of this cell was about 9.62 ％. The incident photon to current conversion efficiency (IPCE) of N3 used as a dye in this work is about 80 ％ at around 590 nm and 610 nm, which is the emission spectrum of Eu$^{3+}$ doped LGF, results in efficiency increasing of DSC.C.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.435-436
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• 2008

Dye-sensitized Solar Cells(DSSCs) which convert incident sun light into electricity were expected to overcome global warming and depletion of fossil fuels. And it is one of study that is lately getting into the spotlight because manufacturing method is more simple and inexpensive than existing silicon solar cells. In this respect, DSSCs are in the limelight as the next generation solar cells. DSSCs are generally composed of a dye-modified $TiO_2$ photoelectrode, a Pt counter electrode, and an electrolytes containing a redox couple$(I^-/I_3^-)$. Among these elements, pt electrode were prepared by applying electric potential to FTO substrate in the $H_2PtCl_6$ solution. In this study, we report the solar cell efficiency depending on $PtCl_4$ concentration change. $PtCl_4$ concentration was 1mM, 5mM, 10mM, and 20mM, and adhered on FTO glass substrate by sintering process. When applied each $PtCl_4$ counter electrode on DSSC, the best efficiency was found at 10mM of $PtCl_4$ concentration. The catalyst promotes the movement of electron from the counter electrode to the electrolyte the higher the molarity, the better the efficiency. However, in case of 20mM, it is estimated that over-deposited $PtCl_4$ tends to restrict the movement of electron due to its bundle formation.