작동전극부에 나노다이아몬드를 첨가한 염료감응형 태양전지의 물성 연구

노윤영 ( Yunyoung Noh ),김광배 ( Kwangbae Kim ),최민경 ( Minkyoung Choi ),송오성 ( Ohsung Song ) 대한금속재료학회(구 대한금속학회) 2016 대한금속·재료학회지 Vol.54 No.1

We prepared a TiO2 blocking layer containing 0~0.5 wt% nano diamonds (NDs) to increase the effective surface area of working electrodes in a dye sensitized solar cell (DSSC). The result was a DSSC with a 0.45 cm2 active area of a glass/FTO/blocking layer (TiO2 with NDs)/TiO2/dye/electrolyte/100 nm Pt/glass structure. The microstructure of the blocking layer was examined by optical microscope, FESEM, and AFM. UV-VIS-NIR was used to determine the optical absorbance of the working electrodes containing NDs. The photovoltaic properties for the ND added DSSC, such as short circuit current density, open circuit voltage, fill factor, energy conversion efficiency, and impedance, were checked using a solar simulator and potentiostat. Microstructure characterization showed that the NDs were evenly dispersed in the blocking layer. The absorbance in the visible light regime increased as the ND content increased. The photovoltaic properties indicated that energy conversion efficiency increased from 3.53% to 4.96% with 0 wt% and 0.4 wt% ND addition. This was due to the decreased interface resistance of the working electrode and the increased surface area and shunt resistance of the blocking layer resulting from the addition of the NDs. The DSSC with 0.5 wt% NDs was less efficient due to a reduction of the effective electron transport area caused by excess NDs. Our results suggest that we can improve the efficiency of a DSSC by proper addition of NDs into the blocking layer.

염료감응태양전지에서 Pd 촉매층의 전해질과의 반응에 따른 특성 저하

노윤영(Noh, Yunyoung),송오성(Song Ohsung) 한국산학기술학회 2013 한국산학기술학회논문지 Vol.14 No.4

기존 DSSC의 상대전극을 TCO-less로 하여 도전성과 촉매기능을 동시에 가지고 있는 Pd의 안정성 확인을 위해 열증착기를 채용하여 유리기판 전면에 Pd를 90nm 두께로 증착하고 전해질과의 반응 안정성을 확인하였다. 0.45cm2급 면 적을 가진 glass/FTO/blocking layer/TiO₂/dye/electrolyte(10 mM LiI + 1 mM I2 + 0.1 M LiClO₄ in acetonitrile solution)/Pd/glass 구조의 DSSC 소자를 만들고, 시편제작 1시간, 12시간 후의 변화를 육안분석, 광학현미경과 FESEM을 이용하여 미세구조 분석을 진행하고, 전기적 분석은 각각 C-V(cyclic voltammetry measurements), I-V(current voltage) 분석 을 통해 확인하였다. 미세구조 분석을 통하여 시간이 지남에 따라 확연히 Pd과 전해질이 반응하여 부식되는 것을 확인하 였고, 전기적으로도 시간이 지남에 따라 촉매활동도와 효율이 감소하는 것을 확인하였다. 최종 효율은 1시간 후에는 0.34%의 광전효율을 보였으나 12시간 후에는 0.15%를 나타내어 약 44%로 감소하였다. 따라서 염료감응태양전지에 Pd촉 매를 채용하기 위해 I-/I3 - 전해질이 아닌 다른 전해질을 사용하거나 Pd 전극이 아닌 다른 촉매재를 사용해야 함을 확인하였다. A TCO-less palladium (Pd) catalytic layer on the glass substrate was assessed as the counter electrode (CE) in a dye sensitized solar cell (DSSC) to confirm the stability of Pd with the I-/I3 -electrolyte on the DSSC performance. A 90nm-thick Pd film was deposited by a thermal evaporator. Finally, DSSC devices of 0.45cm2 with glass/FTO/blocking layer/TiO₂/dye/electrolyte(10 mM LiI + 1 mM I2 + 0.1 M LiClO₄ in acetonitrile solution)/Pd/glass structure was prepared. We investigated the microstructure and photovoltaic property at 1 and 12 hours after the sample preparation. The optical microscopy, field emission scanning electron microscopy (FESEM), cyclic voltammetry measurement (C-V), and current voltage (I-V) were employed to measure the microstructure and photovoltaic property evolution. Microstructure analysis showed that the corrosion by reaction between the Pd layer and the electrolyte occurred as time went by, which led the decrease of the catalytic activity and the efficiency. I-V result revealed that the energy conversion efficiency after 1 and 12 hours was 0.34% and 0.15%, respectively. Our results implied that we might employ the other non- I-/I3 -electrolyte or the other catalytic metal layers to guarantee the long term stability of the DSSC devices.

코발트실리사이드 상대전극을 채용한 염료감응형 태양전지의 물성 연구

노윤영 ( Yunyoung Noh ),김광배 ( Kwangbae Kim ),송오성 ( Ohsung Song ) 대한금속재료학회(구 대한금속학회) 2017 대한금속·재료학회지 Vol.55 No.1

Cobalt silicide was used as a counter electrode to replace the Pt catalytic layer of a dye-sensitized solar cell (DSSC) device. 100 nm Si/ 100 nm Co on quartz were formed by sputtering, and cobalt-silicides were formed by vacuum heat treatment at 500 ℃ and 700 ℃ for 30 min, respectively. Field emission scanning electron microscopy (FE-SEM) was used to analyze the surface microstructure. X-ray diffraction (XRD) and Auger electron spectroscopy (AES) depth profiling analysis were used to confirm the phases. Also, cyclic-voltammetry (CV) analysis was employed to confirm the catalytic activity, and photovoltaic properties were confirmed using a simulator and potentiostat. The microstructure analysis indicated that the 500 ℃ and 700 ℃ silicidation led to a uniform planar layer, and island-like agglomerates, respectively. In the XRD and AES results, those phases were structures of quartz/CoSi/Co and quartz/dot-(CoSi₂/Co). CV analysis showed that Si/Co and CoSi/Co exhibited catalytic activity, while dot-(CoSi₂/Co) did not show catalytic activity due to the isolated dot structure. The energy conversion efficiencies of DSSCs with CoSi/Co and dot-(CoSi₂/Co) were 3.75% and 0%, respectively, while that of Pt employed DSSC was 5.13%. Our result implies that using the nano-thick CoSi as a reduction catalytic layer may be an effective replacement for Pt. (Received March 4, 2016; Acceted July 22, 2016)

염료감응태양전지의 Au/Pt 이중 촉매층의 전해질과의 반응에 따른 열화

노윤영(Noh, Yunyoung),송오성(Song Ohsung) 한국산학기술학회 2014 한국산학기술학회논문지 Vol.15 No.6

염료감응형 태양전지 상대전극부에 Au/Pt 이중 촉매층 적용에 따른 전해질과의 반응안정성 확인과 에너지변환효율 변화를 확인하기 위해 0.45cm2 면적을 가진 glass/FTO/blocking layer/TiO₂/dye/electrolyte/50nm Pt/50nm Au/glass 구조의 소자를 준비하였다. 비교를 위해 평탄한 유리기판 위에 증착된 100nm 두께의 Pt 상대전극을 채용한 소자도 동일한 방법으로 확인하였다. 솔라 시뮬레이터와 퍼텐쇼 스탯을 통해 단락전류밀도, 개방전압, 필팩터, 에너지변환효율의 광전기적 특성을 확 인하였다. Au/Pt 이중층과 전해질의 반응을 확인하기 위해 광학현미경을 통해 전해질 주입 후 0∼25분 후 이중층의 미세구조 를 확인하였다. 광전기적 특성 분석 결과, 평탄한 유리기판 위의 단일층 Pt의 에너지변환효율은 4.60%를 나타내고 시간 의존 성이 없었다. 반면, Au/Pt의 경우 전해질 주입 직 후, 5분 후, 25분 후의 에너지 변환 효율이 각각 5.28%, 3.64%, 2.09%로 시간이 지남에 따라 감소하였다. 광학현미경 분석을 통하여, 전해질 주입 직 후, 5분 후, 25분 후의 부식면적이 각각 0, 21.92, 34.06%로 Au와 전해질이 반응하여 부식되는 것을 확인하였고, 이를 통해 Au/Pt가 전기적으로 시간이 지남에 따라 촉매활성 도와 효율이 감소하는 것을 확인하였다. 따라서 염료감응태양전지에 Au/Pt 촉매는 단기적으로는 기존 Pt only보다 우수하였 으나 장기적으로는 전해질과의 안정성이 미흡함을 확인하였다. A 0.45 cm2 DSSC device with a glass/FTO/blocking layer/TiO₂/N719(dye)/electrolyte/50 nm-Pt/50 nm-Au/FTO/glass was prepared to examine the stability of the Au/Pt bilayered counter electrode (CE) with electrolyte and the energy conversion efficiency (ECE) of dye-sensitized solar cells (DSSCs). For comparison, a 100 nm-thick Pt only CE DSSC was also prepared using the same method. The photovoltaic properties, such as the short circuit current density (Jsc), open circuit voltage (Voc), fill factor (FF), and ECE, were checked using a solar simulator and potentiostat with time after assembling the DSSC. The microstructure of the Au/Pt bilayer was examined by optical microscopy after 0∼25 minutes. The ECE of the Pt only CE-employed DSSC was 4.60 %, which did not show time dependence. On the other hand, for the Au/Pt CE DSSC, the ECEs after 0, 5 and 15 minutes were 5.28 %, 3.64 % and 2.09 %, respectively. The corrosion areas of the Au/Pt CE determined by optical microscopy after 0, 5, and 25 minutes were 0, 21.92 and 34.06 %. These results confirmed that the ECE and catalytic activity of Au/Pt CE decreased drastically with time. Therefore, a Au/Pt CE-employed DSSC may be superior to the Pt only CE-employed one immediately after integration of the device, but it would degrade drastically with time.

나노급 Cr/Pt 이중층이 사용된 염료감응태양전지의 저온 열처리에 따른 물성변화

노윤영 ( Yunyoung Noh And ),송오성 ( Oh Sung Song ) 대한금속재료학회(구 대한금속학회) 2014 대한금속·재료학회지 Vol.52 No.10

Abstract: The properties of the Cr/Pt bilayered catalytic layer with additional low temperature annealing using a dye sensitized solar cell (DSSC) were investigated. A DSSC device with a structure with an effective area of 0.45 cm2 glass/FTO/blocking layer/TiO2/N719 (dye)/electrolyte/50 nm Pt/50 nm Cr/glass was prepared. For comparison, 100 nm-thick Pt and Cr counter electrodes on flat glass substrates were also prepared using the same procedure. The sheet resistance was examined using a four point probe. The photovoltaic properties, such as the short circuit current density, open circuit voltage, fill factor, energy conversion efficiency (ECE), and impedance, were characterized using a solar simulator and potentiostat. The phases of the bilayered films were examined by X-ray diffraction. The microstructure of the bilayered films was characterized by atomic force microscopy. The measured sheet resistance of the counter electrode with annealing increased to. The measured ECE of the dye-sensitized solar cell devices with vacuum annealed Cr/Pt bilayer counter electrodes decreased abruptly. The interface resistance at the interface between the counter electrode and electrolyte increased as the annealing time increased. The increase in catalytic activity of the Cr/Pt bilayer before annealing resulted from the effect of a compressive strain field. After 10 minutes, the strain field was removed by annealing. The new phases of Pt3Cr and CrPt by annealing led to drastically decreased catalytic activity.

구리 합금을 위한 초고융점 원소의 용융산화물 확산 공정

송정호,노윤영,송오성,Song, Jeongho,Noh, Yunyoung,Song, Ohsung 한국재료학회 2016 한국재료학회지 Vol.26 No.3

To alloy high melting point elements such as boron, ruthenium, and iridium with copper, heat treatment was performed using metal oxides of $B_2O_3$, $RuO_2$, and $IrO_2$ at the temperature of $1200^{\circ}C$ in vacuum for 30 minutes. The microstructure analysis of the alloyed sample was confirmed using an optical microscope and FE-SEM. Hardness and trace element analyses were performed using Vickers hardness and WD-XRF, respectively. Diffusion profile analysis was performed using D-SIMS. From the microstructure analysis results, crystal grains were found to have formed with sizes of 2.97 mm. For the copper alloys formed using metal oxides of $B_2O_3$, $RuO_2$, and $IrO_2$ the sizes of the crystal grains were 1.24, 1.77, and 2.23 mm, respectively, while these sizes were smaller than pure copper. From the Vickers hardness results, the hardness of the Ir-copper alloy was found to have increased by a maximum of 2.2 times compared to pure copper. From the trace element analysis, the copper alloy was fabricated with the expected composition. From the diffusion profile analysis results, it can be seen that 0.059 wt%, 0.030 wt%, and 0.114 wt% of B, Ru, and Ir, respectively, were alloyed in the copper, and it led to change the hardness. Therefore, we verified that alloying of high melting point elements is possible at the low temperature of $1200^{\circ}C$.

염료감응형 태양전지용 코발트실리사이드들의 촉매 물성

김광배,노윤영,송오성,Kim, Kwangbae,Noh, Yunyoung,Song, Ohsung 한국재료학회 2016 한국재료학회지 Vol.26 No.8

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.

백색금 합금용 모합금의 실리콘 함량에 따른 물성변화

송정호,노윤영,이현우,최민경,송오성,Song, Jeongho,Noh, Yunyoung,Lee, Hyeonwoo,Choi, Minkyoung,Song, Ohsung 한국재료학회 2015 한국재료학회지 Vol.25 No.2

We prepared 8 samples of non-silver and silver-added master alloys containing silicon to confirm the existence of nickel-silicides. We then prepared products made of 14K and 18K white gold by using the prepared master alloys containing 0.25, 0.35, and 0.50 wt% silicon to check for nickel release. We then employed the EN 1811 testing standard to investigate the nickel release of the white gold products, and we also confirmed the color of the white gold products with an UV-VIS-NIR-color meter. We observed $NiSi_x$ residue in all master alloys containing more than 0.50 wt% Si with EDS-nitric acid etching. For the white gold products, we could not confirm the existence of $NiSi_x$ through XRD after aqua-regia etching. In the EN 1811 test, only the white gold products with 0.25 wt% silicon master alloys successfully passed the nickel release regulations. Moreover, we confirmed that our white gold products showed excellent Lab indices as compared to those of commercial white gold ones, and the silver-added master alloys offered a larger L index. Our results indicate that employing 0.25 wt% silicon master alloys might be suitable for white gold products without nickel-silicide defects and nickel release problems.

초고압을 이용한 나노급 마그네시아 분말의 저온 소결 연구

송정호,엄정혜,노윤영,김영욱,송오성,Song, Jeongho,Eom, Junghye,Noh, Yunyoung,Kim, Young-Wook,Song, Ohsung 한국세라믹학회 2013 한국세라믹학회지 Vol.50 No.3

We performed high pressure high temperature (HPHT) sintering for the 20 nm MgO powders at the temperatures from $600^{\circ}C$ to $1200^{\circ}C$ for only 5 min under 7 GPa pressure condition. To investigate the microstructure evolution and physical property change of the HPHT sintered MgO samples, we employed a scanning electron microscopy (SEM), density and Vickers hardness measurements. The SEM results showed that the grain size of the sintered MgO increased from 200 nm to $1.9{\mu}m$ as the sintering temperature increased. The density results showed that the sintered MgO achieved a more than 95% of the theoretical density in overall sintering temperature range. Based on Vickers hardness test, we confirmed that hardness increased as temperature increased. Our results implied that we might obtain the dense sintered MgO samples with an extremely short time and low temperature HPHT process compared to conventional electrical furnace sintering process.

천연과 CVD 합성 다이아몬드의 감별을 위한 물성 연구

김연우,송정호,노윤영,송오성,Kim, Yunwoo,Song, Jeongho,Noh, Yunyoung,Song, Ohsung 한국세라믹학회 2014 한국세라믹학회지 Vol.51 No.4

Recently, Chemical Vapor Deposition (CVD) synthetic diamonds have been introduced to the jewelry gem market, as CVD technology has been making considerable advances. Unfortunately, CVD diamonds are not distinguishable from natural diamonds when using the conventional gemological characterization method. Therefore, we need to develop a new identification method that is non-destructive, fast, and inexpensive. In our study, we employed optical microscopy and spectroscopy techniques, including Fourier transform infra-red (FT-IR), UV-VIS-NIR, photoluminescence (PL), micro Raman, and cathodoluminescent (CL) spectroscopy, to determine the differences between a natural diamond (0.30 cts) and a CVD diamond (0.43 cts). The identification of a CVD diamond was difficult when using standard gemological techniques, UV-VIS-NIR, or micro-Raman spectroscopy. However, a CVD diamond could be identified using a FT-IR by the Type II peaks. In addition, we identified a CVD diamond conclusively with the uneven UV fluorescent local bands, additional satellite PL peaks, longer phosphorescence life time, and uneven streaks in the CL images. Our results suggest that using FT-IR combined with UV fluorescent images, PL, and CL analysis might be an appropriate method for identifying CVD diamonds.