• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.251-254
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• 2001

This paper describes an efficiency improvement of buried contact solar cell (BSCS) with a structure of MgF$_2$/CeO$_2$/Ag/Cu/Ni grid/n$^{+}$ emitter/p-type Si base/p$^{+}$/Al. Theoretical and experimental investigations were performed on a double layer antireflection (DLAR) coating of MgF$_2$/CeO$_2$. We investigated CeO$_2$ films as an AR layer because they have a proper refractive index of 2.46 and demonstrate the same lattice constant as Si substrate. An optimized DLAR coating shewed a reflectance as low as 2.04 % in the wavelengths ranged from 0.4 ${\mu}{\textrm}{m}$ to 1.1 ${\mu}{\textrm}{m}$. BCSC cell efficiency was improved from 16.2 % without any AR coating to 19.9 % by employing DLAR coatings. Further details on MgF$_2$/CeO$_2$ DLAR coatings on the BCSC cells are presented in this paper.per.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.242-242
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• 2010

산화 알루미늄($Al_2O_3$) 박막을 p-type Czochralski(CZ) Si 위에 Remote Plasma Atomic Layer Deposition(RPALD)을 이용하여 저온 공정으로 증착하였다. Photolithography 공정으로 grid 패턴을 형성한 후 열 증착기로 알루미늄을 증착하여 MIS-IL (Metal-Insulator-Semiconductor Inversion Layer) solar cell을 제작하였다. 반응소스로는 Trimethylaluminum (TMA)과 $O_2$를 이용하였다. $Al_2O_3$ 박막의 전기적 특성 평가를 위해 MIS capacitor를 제작하여 Capacitance-voltage (C-V), Current-voltage (I-V), Interface state density ($D_{it}$)를 평가하였으며 Solar simulator를 이용하여 MIS-IL Solar cell의 Efficiency을 측정하였다.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.36.1-36.1
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• 2010

While the substrate-type solar cells with Cu(In,Ga)Se2 absorbers yield conversion efficiencies of up 20%[1], the highest published efficiency of Cu(In,Ga)Se2 superstrate solar cell is only 12.8% [2]. The commerciallized Cu(In,Ga)Se2 solar cells are made in the substrate configuration having the stacking sequence of substrate (soda lime glass)/back contact (molybdenum)/absorber layer (Cu(In,Ga)Se2)/buffer layer (cadmium sulfide)/window layer (transparent conductive oxide)/anti reflection layer (MgF2) /grid contact. Thus, it is not possible to illuminate the substrate-type cell through the glass substrate. Rather, it is necessary to illuminate from the opposite side which requires an elaborate transparent encapsulation. In contrast to that, the configuration of superstrate solar cell allows the illumination through the glass substrate. This saves the expensive transparent encapsulation. Usually, the high quality Cu(In,Ga)Se2 absorber requires a high deposition temperature over 550C. Therefore, the front contact should be thermally stable in the temperature range to realize a successful superstrate-type solar cell. In this study, it was tried to make a decent superstrate-type solar cell with the thermally stable ZnO:Al layer obtained by adjusting its deposition parameters in magnetron sputtering process. The effect of deposition condition of the layer on the cell performance will be discussed together with hall measurement results and current-voltage characteristics of the cells.

• Electrical & Electronic Materials
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• v.7 no.3
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• pp.243-251
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• 1994

ITO(Indium Tin Oxide) film with thickness of 1500.angs. was prepared by an e-beam evaporator onto a glass and a p-type InP wafer (100) LEC grown Zn-doped p=2.3*10$\^$16/cm$\^$-3/), in which the components of ITO used for evaporation source were hot pressed pellets 1 mole% ln$\_$2/O$\_$3/+9 mole% SnO$\_$2/, and evaporated in O$\_$2/ ambient. The optimum conditions to preparation of ITO thin film were the substrate temperature of 350.deg. C, the injected oxygen pressure of 2*10$\^$-4/ torr, and the evaporation speed of 0.2-0.3.angs./sec, respectively. In these optimum conditions, the resistivity and the carrier concentration were 5.3*10$\^$-3/ .ohm.-cm, 6.5*10$\^$20/cm$\^$-3/, and the transmittance was over 80%. From the results of J-V measurements in ITO/p-InP structure solar cells, the higher pressure of injected oxygen, the more open circuit voltage. The efficiency of ITO/p-InP solar cell without the grid line contact, prepared by the optimum evaporation conditions, was 7.19%. By using the grid line contact, the efficiency, the open circuit voltage, the short circuit current density, the fill factor, the series resistance, and the shunt resistance were 8.5%, 0.47V, 29.48 mAcm$\^$-2/ , 61.35%, 3.ohm., and 26.6k.ohm., respectively.

• 한국전산유체공학회:학술대회논문집
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• 2009.04a
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• pp.223-226
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• 2009

This paper presents three-dimensional flow analysis for a mixed-flow pump which consists of a rotor and a stator. Reynolds-averaged Navier-Stokes equations with shear stress transport turbulence model are discretized by finite volume approximations and solved by the commercial CFD code CFX 11.0. Structured grid system is constructed in the computational domain, which has O-type grids near the blade surfaces and H-type grids in other regions. Validation of the numerical results was performed with experimental data for head coefficients and hydraulic efficiencies at different flow coefficients. This paper shows that the pump characteristics can be predicted effectively by numerical analysis.

• The KSFM Journal of Fluid Machinery
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• v.13 no.1
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• pp.17-22
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• 2010

In this paper, numerical study on a mixed-flow pump for irrigation and drainage has been performed based on three-dimensional viscous flow analysis. Reynolds-averaged Navier-Stokes equations with shear stress transport turbulence model are discretized by finite volume approximations and solved by the commercial CFD code ANSYS CFX-11.0. A structured grid system is constructed in the computational domain, which has O-type grids near the blade surfaces and H/J-type grids in other regions. The numerical results were validated with experimental data for the heads and efficiencies at different flow coefficients. The efficiency at the design flow coefficient is evaluated with the variation of two geometric variables related to area of discharge and length of the vane in the diffuser. The results show that efficiency of the mixed-flow pump at the design flow coefficient is improved by the modifications of the geometry.

• Nuclear Engineering and Technology
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• v.48 no.4
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• pp.915-924
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• 2016

After a severe accident to the nuclear reactor, the in-vessel retention strategy is a key way to prevent the leakage of radioactive material. Nanofluid is a steady suspension used to improve heat-transfer characteristics of working fluids, formed by adding solid particles with diameters below 100nm to the base fluids, and its thermal physical properties and heat-transfer characteristics are much different from the conventional working fluids. Thus, nanofluids with appropriate nanoparticle type and volume concentration can enhance the heat-transfer process. In this study, the moving particle semi-implicit method-meshless advection using flow-directional local grid method is used to simulate the bubble growth, departure, and sliding on the downward-facing heating surface in pure water and nanofluid (1.0 vol.% $Al_2O_3/H_2O$) flow boiling processes; additionally, the bubble critical departure angle and sliding characteristics and their influence are also investigated. The results indicate that the bubble in nanofluid departs from the heating surface more easily and the critical departure inclined angle of nanofluid is greater than that of pure water. In addition, the influence of nanofluid on bubble sliding is not significant compared with pure water.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.306.1-306.1
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• 2016

ZnO semiconductor material has been widely utilized in various applications in semiconductor device technology owing to its unique electrical and optical features. It is a promising as solar cell material, because of its low cost, n-type conductivity and wide direct band gap. In this work ZnO/Si heterojunctions were fabricated by using pulsed laser deposition. Vacuum chamber was evacuated to a base pressure of approximately $2{\times}10^{-6}Torr$. ZnO thin films were grown on p-Si (100) substrate at oxygen partial pressure from 5mTorr to 40mTorr. Growth temperature of ZnO thin films was set to 773K. A pulsed (10 Hz) Nd:YAG laser operating at a wavelength of 266 nm was used to produce a plasma plume from an ablated a ZnO target, whose density of laser energy was $10J/cm^2$. Thickness of all the thin films of ZnO was about 300nm. The optical property was characterized by photoluminescence and crystallinity of ZnO was analyzed by X-ray diffraction. For fabrication ZnO/Si heterojunction diodes, indium metal and Al grid patterns were deposited on back and front side of the solar cells by using thermal evaporator, respectively. Finally, current-voltage characteristics of the ZnO/Si structure were studied by using Keithly 2600. Under Air Mass 1.5 Global solar simulator with an irradiation intensity of $100mW/cm^2$, the electrical properties of ZnO/Si heterojunction photovoltaic devices were analyzed.

• Journal of the Society of Disaster Information
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• v.15 no.3
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• pp.418-426
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• 2019

Purpose: After analyzing the seismic capability of low-rise RC grid structures with insufficient seismic performance, the purpose of the project is to install steel slab hysteretic dampers (SSHD) to improve the seismic performance of beams and columns, and to suggest measures to minimize damage to the structure and human damage when an earthquake occurs. Method: The evaluation of the seismic performance of a structure is reviewed based on the assumption that the seismic performance is identified for the grid-type subway systems that are not designed to be seismic resistant and the installation of an SSHD system, a method that minimizes construction period, if insufficient, is required. Result: After the application and reinforce of structure with SSHD, and the results of eigenvalue analysis are as follows. The natural periodicity of longitudinal direction was 0.55s and that of vertical direction was 0.58s. Conclusion: As results of cyclic load test of structure with SSHD, the shear rigidity of damper is 101%, the energy dissipation rate is 108% and, plastic rotation angle of all column and beam is satisfied for $I_o$ level and therefore it is judged that the reinforce effect is sufficient.

• Korean Journal of Crystallography
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• v.15 no.2
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• pp.78-82
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• 2004

The solvothermal reaction of zinc(H) nitrate $(Zn(NO_3)_2\;{\cdot}\;6H_2O)$ with $ATP(2-aminoterephthalate,\;H_2N-C_6H_3-1,4-(COO)_2)$ in a mixture of solvents of DMF and ethanol, in the presence of benzene, gave a 2 dimensional zinc polymer [Zn(ATP) (DMF)] (1). X-ray structure determination revealed that two zinc metals and four ATP ligands form the paddle-wheel SBUs, which are linked by the ATP ligands to give a 2-D square-grid network. Each square grid has approximate dimensions of $11.1\times11.1\;{\AA}$ based on Zn metals. Benzene was required to produce high-quality crystals of polymer 1.