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Characterization of ZnO : Al-Thin-Film-Passivated Porous Silicon
Kyungha Kim,이종무,프라바카르 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.48 No.6
Al-doped ZnO (AZO) films were deposited on porous silicon (PS) and on glass substrates by using a reactive rf-cosputtering process from targets of ZnO and Al. The effects of the ZnO target’s rf-sputtering power on the structural and the photoluminescence (PL) properties were studied. The crystalline structures of the AZO films were improved, and the degree of (002) preferred orientation was enhanced. The optical transmittance spectra showed more than 80 % transmittance in the visible region, and the band gap was found to be direct. Strong monochromatic blue emission located at 2.78 eV was observed for the AZO films deposited at 150 W. Freshly prepared PS showed an emission band in the green spectral region. We show that deposition of AZO on PS does not degrade the skeleton of the PS and enhances the PL intensity. The PL band shifts to high energy for AZO films deposited on PS, and the intensity becomes stable. The current-voltage characteristics of AZO/PS heterostructures were also studied. The ideality factor was found to be 19, and the series resistance determined from the forward characteristics was 36 M .h
Inyoung Shin,Hyunwoong Seo,Min-Kyu Son,Jin-Kyoung Kim,김희제,프라바카르 한국물리학회 2010 Current Applied Physics Vol.10 No.3
Dye-sensitized solar cell (DSC) consists of a TiO2 nano film of the photo electrode, dye molecules on the surface of the TiO2 film, an electrolyte layer and a counter electrode. Among these, the nano porous TiO2film plays an important role as the photo electrode in DSC because it adsorbs a large number of the dye molecules which provide electrons. Therefore, the condition of the TiO2 film affects the cell performance such as current density (Jsc), open circuit voltage (Voc) and fill factor (FF). The thickness of TiO2 film is one of these conditions. Its variation influences on the internal impedances of DSC related to the electron transport. In this study, we analyzed the characteristics of DSC with the different thicknesses of TiO2 film by using electrochemical impedance spectroscopy (EIS) in details. As a result, it was demonstrated that the variation of the TiO2 thickness has an effect on the electron transport in the DSC. Finally, the TiO2thickness is optimized for the best performance of DSC.
Fabrication of Mesoporous TiO2 Double Layer Using Dicarboxylic Acid in Dye-Sensitized Solar Cell
김수경,Min-Kyu Son,Songyi Park,정명수,Hyunwoong Seo,프라바카르,김희제 대한금속·재료학회 2014 ELECTRONIC MATERIALS LETTERS Vol.10 No.1
Several techniques have been used to prepare titanium dioxide (TiO2) paste from commercially available powders for applications in dye-sensitized solar cells (DSCs). In this study, submicron-sized TiO2 agglomerates with mesopores (2 - 50 nm) were prepared using a dicarboxylic acid, adipic acid. This type of acid creates new hydroxyl groups that increase the surface area and level of dye adsorption. The adipic acid-added mesoporous TiO2 exhibited light scattering effect at a comparable wavelength with a lower back-scattering efficiency. The effects of the TiO2 paste components, such as the morphology, characteristics and structure, were examined and comparative studies were performed using acetic acid added-TiO2 nanoparticles.
Songyi Park,김희제,Min-Kyu Son,Soo-Kyoung Kim,Myeong-Soo Jeong,프라바카르 한국화학공학회 2013 Korean Journal of Chemical Engineering Vol.30 No.11
The electrolyte for QDSSCs is normally a polysulfide, S2−/Sx 2−, redox couple. This couple plays an important role for the regeneration of quantum dots. This study examined the effects of the electrolyte for CdS/CdSe QDSSCs. Electrolytes consisting of 1M Na2S, 2M S in a methanol and water-mixed solution at a 7 : 3 ratio with or without additives such as KCl, NaOH, KOH and NaCl were used for QDSSC. The electrolyte with NaOH showed the highest conversion efficiency, 3.18%. The reasons for the improved photovoltaic characteristics were analyzed using a range of techniques.
김희제(Hee-Je Kim),이정기(Jeong-Gee Lee),이경준(Kyung-Jun Lee),프라바카르(Prabakar),신동설(Dong-Seoul Sin),채원용(Won-Yong Chae) 대한전기학회 2010 전기학회논문지 Vol.59 No.1
The shadowing effects lead to the serious power losses of the PV module. The shadowing effects are caused by several factors such as leafs, dust, antenna and clouds. The dye-sensitized solar cells are more economical than the conventional silicon solar cell that's why the dye-sensitized solar cells are recently focused on. We carried out research on the efficiency of the dye-sensitized solar cell depending on the level of shadow changing the formula of the circuit. The research on the efficiency of the large dye-sensitized solar cell depending on the level of shadow focused on commercialization was carried out. As the results, it is known that the series and parallel connection method is the best choice for the least losses of PV module assemblies. It is especially known that one more series connection is the best choice for the least losses about shadowing effects and current losses in the series and parallel connection.
TiO₂ 두께에 따른 염료감응형 태양전지의 전기화학적 임피던스 분석
김희제(Hee-Je Kim),이정기(Jeong-Gee Lee),서현웅(Hyunwoong Seo),손민규(Min-Kyu Son),김진경(Jin-Kyoung Kim),프라바카르(K. Prabakar),신인영(Inyoung Shin) 대한전기학회 2009 전기학회논문지 Vol.58 No.12
Dye-sensitized solar cell(DSC) is composed of a dye-adsorbed nanoporous TiO₂ layer on fluorine-doped tin oxide(FTO) glass substrate, electrolyte, and platinium doped counter electrode. Among these, a dye-absorbed nanoporous TiO₂ layer plays an important role in the performance of the DSC because the injected electrons from excited dye molecules move through this layer. And the condition of TiO₂ layer such as the morphology and thickness affects on the electron movement. Therefore, the performances and the efficiency of DSC change as the thickness of TiO₂ layer is different. Electrochemical Impedance Spectroscopy(EIS) is the powerful analysis method to study the kinetics of electrochemical and photoelectrochemical processes occurring in the DSC especially the injected electron movements. So we analyzed the DSCs with different TiO₂ thicknesses by using EIS to understand the influence of the TiO₂ thickness to the performance of the DSC clearly. Finally, we got the EIS analysis on the DSC with different TiO₂ thickness from the internal resistance of the DSC, the electron life time and the amount of dye molecules.
B. Balamuralitharan,Suresh Kannan Balasingam,S. N. Karthick,Ananthakumar Ramadoss,Manab Kundu,박진수,조인호,프라바카르,전용석,김희제 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.71 No.-
Iron pyrite (FeS2) is an interesting mineral in the transition metal dichalcogenide group due to its highabundance in the earth’s crust which can be used for various electrochemical energy storage applications,such as batteries and supercapacitors; however, it suffers from low rate capability and poor cycleperformance, which hampers its use from large-scale commercial applications. In the present study, irondisulfide microspheres anchored onto a reduced graphene oxide matrix (rGO-FeS2 hybrid) were grownusing a superficial hydrothermal method. For comparison, rGO-free iron disulfide material wassynthesized under the same hydrothermal conditions, and uniformly distributed FeS2 micro-sizeflowerswere formed. The energy storage capacity of both electroactive materials (FeS2 and rGO-FeS2 hybridmaterial) was tested for supercapacitor applications in a symmetric cell configuration. The pristine FeS2microflower electrode exhibited an areal capacitance of 70.98 mF cm 2 at 5 mV s 1. On the other hand,the rGO-FeS2 hybrid microsphere electrode exhibited an enhanced areal capacitance of 112.41 mF cm 2 atthe same scan rate with an excellent capacitance retention of 90% over 10,000 cycles. The improvedelectrochemical performance of the rGO-FeS2 hybrid material is due mainly to its improved electricalconductivity, high surface area indicating an enhanced electron, and ion transfer mechanism. This studysuggests that the rGO-FeS2 hybrid electrode material has potential applications in energy storage devices.
Zinc nitrate 용액을 이용한 염료감응형 태양전지 반사 방지막에 관한 연구
최진호(Jinho Choi),서현웅(Hyunwoong Seo),손민규(Min-Kyu Son),김수경(Soo-Kyoung Kim),김병만(Byung-Man Kim),김희제(Hee-Je Kim),프라바카르(Kandasamy Prabakar),김종락(Jong-Rak Kim) 대한전기학회 2012 전기학회논문지 Vol.61 No.5
An anti-reflection layer (AR) is used in the solar cell to improve the amount of the irradiated light, resulting in the improvement of the performance of the solar cell. In this study, the zinc oxide (ZnO) AR is applied to the dye-sensitized solar cell (DSC) by using zinc nitrate solution. The conditions such as solution concentration and sintering temperature for fabricating the ZnO AR are changed to optimize the performance of the AR. As a result, the best performance is shown when the zinc nitrate solution with 100mM concentration is used and the sintering temperature is 600℃. And then, the ZnO AR formed with these optimal conditions is applied to the DSC. Consequently, a DSC with a ZnO AR had an increased current density up to 13.86㎃/㎠ and an enhanced efficiency of 6.32%.
Blocking layer 제작에 따른 염료감응형 태양전지 출력특성 및 내부 임피던스 분석
김진경(Jin-Kyoung Kim),손민규(Min-Kyu Son),김수경(Soo-Kyoung Kim),홍나영(Na Yeong Hong),김병만(Byung-Man Kim),프라바카르(KANDASAMY PRABAKAR),김희제(Hee-Je Kim) 대한전기학회 2012 전기학회논문지 Vol.61 No.1
DSCs are based on a dye-adsorbed porous TiO2 layer as a photo electrode [1]. Under the illumination, dye molecules are excited and electrons are produced. The injected electrons in the conduction band of TiO2 may recombine with the electrolyte. To obtain high performance DSCs, it is essential to retard the recombination. The charge recombination can be reduced by forming core-shell structure. In this work, we investigated the core-shell structure with Al2O3 and MgO coating layer on the porous TiO2 layer. We confirmed the photovoltaic properties by I-V characteristics. The current and the efficiency was improved. In addition to, Through decrease in the width of EIS arc, which is the sum of the interfacial charge transfer resistances of both electrodes, we can be indicated that the block effect.