• Current Photovoltaic Research
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• v.9 no.3
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• pp.75-83
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• 2021

The tunnel oxide passivated contact (TOPCon) structure got more consideration for development of high performance solar cells by the introduction of a tunnel oxide layer between the substrate and poly-Si is best for attaining interface passivation. The quality of passivation of the tunnel oxide layer clearly depends on the bond of SiO in the tunnel oxide layer, which is affected by the subsequent annealing and the tunnel oxide layer was formed in the suboxide region (SiO, Si₂O, Si₂O₃) at the interface with the substrate. In the suboxide region, an oxygen-rich bond is formed as a result of subsequent annealing that also improves the quality of passivation. To control the surface morphology, annealing profile, and acceleration rate, an oxide tunnel junction structure with a passivation characteristic of 700 mV or more (V_oc) on a p-type wafer could achieved. The quality of passivation of samples subjected to RTP annealing at temperatures above 900℃ declined rapidly. To improve the quality of passivation of the tunnel oxide layer, the physical properties and thermal stability of the thin layer must be considered. TOPCon silicon solar cell has a boron diffused front emitter, a tunnel-SiO_x/n⁺-poly-Si/SiN_x:H structure at the rear side, and screen-printed electrodes on both sides. The saturation currents J_o of this structure on polished surface is 1.3 fA/cm² and for textured silicon surfaces is 3.7 fA/cm² before printing the silver contacts. After printing the Ag contacts, the J_o of this structure increases to 50.7 fA/cm² on textured silicon surfaces, which is still manageably less for metal contacts. This structure was applied to TOPCon solar cells, resulting in a median efficiency of 23.91%, and a highest efficiency of 24.58%, independently. The conversion efficiency of interdigitated back-contact solar cells has reached up to 26% by enhancing the optoelectrical properties for both-sides-contacted of the cells.

• Journal of the Korean Society of Radiology
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• v.14 no.7
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• pp.891-898
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• 2020

As the problem of shields made of lead has recently emerged, research on replacement shields is essential, and studies on the manufacture of diagnostic X-ray shields with 3D printers are also being actively conducted. Recently, with the development of metal mixed filaments, it has become possible to manufacture shielding materials easily, but studies on the nozzle size and output setting of 3D printers are insufficient. Therefore, this study aims to compare and analyze the results through a shielding rate experiment using a brass filament and a 3D printer, outputting the shield according to the nozzle size and layer height, and using a diagnostic radiation generator. The nozzle size was changed to 0.4, 0.8 mm, layer height 0.1, 0.2, 0.3, 0.4 mm, and output. The shielding rate test was fixed at 40 mAs, and the shielding rate was analyzed by experimenting with 60, 80, and 100 kVp, respectively. As a result of the analysis, it was analyzed that the printing time could be reduced to 1/10 according to the nozzle size and the layer height, and the shielding rate could be increased by 1% or more.

• Journal of the Korean Graphic Arts Communication Society
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• v.30 no.1
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• pp.59-69
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• 2012

This study is Long term preservation measures which is closely related to preserving paper records, record condition evaluation, preservation measure and is conducted as follows. As for Means to Evaluate the Deterioration and Damaged Conditions of Records, research and analysis has been made on the contamination and deterioration examples such as damage, dry, stapler, metal, contamination, acidification which are the characteristics of paper record damage types. The of Paper record is one of the key procedures to evaluate the record material and its physi-chemical status in many criteria and to suggest the best preservation method. Between 1970 and 2000, the main record materials was fine paper and OMR paper along with partly newspaper and coarse paper, whereas the main recording material was ball point pen. Overall damage and deterioration status is, for record materials between 1940 and 1960, high deterioration was found and in urgent need for preservation measure and more damages are caused by tapes, staplers and metals. As for records after 1970, there is light deterioration but needs preservation process. There are approximately 3 million records produces before 2000, and assuming that there are 30 pages per record and that 30% has been damaged or deteriorated, 27 million pages are subject to preservation process. Among damaged or deteriorated records, there are large number of records impossible to go through deacidification process so manual preservation and restoration process is necessary as well. Securing manpower having preservation and restoration skills as well as preservation equipment(deacidification process, preservation and restoration) is in urgent need.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.293.1-293.1
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• 2016

Various materials including conductive, dielectric, and semi-conductive materials, constitute suitable candidates for printed electronics. Metal nanoparticles (e.g. Ag, Cu, Ni, Au) are typically used in conductive ink. However, easily oxidized metals, such as Cu, must be processed at low temperatures and as such, photonic sintering has gained significant attention as a new low-temperature processing method. This method is based on the principle of selective heating of a strongly absorbent film, without light-source-induced damage to the transparent substrate. However, Cu nanoparticles used in inks are susceptible to the growth of a native copper-oxide layer on their surface. Copper-oxide-nanoparticle ink subjected to a reduction mechanism has therefore been introduced in an attempt to achieve long-term stability and reliability. In this work, a flash-light sintering process was used for the reduction of an inkjet-printed Cu(II)O thin film to a Cu film. Using a photographic lighting instrument, the intensity of the light (or intense pulse light) was controlled by the charged power (Ws). The resulting changes in the structure, as well as the optical and electrical properties of the light-irradiated Cu(II)O films, were investigated. A Cu thin film was obtained from Cu(II)O via photo-thermal reduction at 2500 Ws. More importantly, at one shot of 3000 Ws, a low sheet resistance value ($0.2527{\Omega}/sq.$) and a high resistivity (${\sim}5.05-6.32{\times}10^{-8}{\Omega}m$), which was ~3.0-3.8 times that of bulk Cu was achieved for the ~200-250-nm-thick film.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.1.1-1.1
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• 2011

Printed electronics based on the direct writing of solution processable functional materials have been of paramount interest and importance. In this talk, the synthesis of printable inorganic functional materials (conductors and semiconductors) for thin-film transistors (TFTs) and photovoltaic devices, device fabrication based on a printing technique, and specific characteristics of devices are presented. For printable conductor materials, Ag ink is designed to achieve the long-term dispersion stability and good adhesion property on a glass substrate, and Cu ink is sophisticatedly formulated to endow the oxidation stability in air and even aqueous solvent system. The both inks were successfully printed onto either polymer or glass substrate, exhibiting the superior conductivity comparable to that of bulk one. In addition, the organic thin-film transistor based on the printed metal source/drain electrode exhibits the electrical performance comparable to that of a transistor based on a vacuum deposited Au electrode. For printable amorphous oxide semiconductors (AOSs), I introduce the noble ways to resolve the critical problems, a high processing temperature above $400^{\circ}C$ and low mobility of AOSs annealed at a low temperature below $400^{\circ}C$. The dependency of TFT performances on the chemical structure of AOSs is compared and contrasted to clarify which factor should be considered to realize the low temperature annealed, high performance AOSs. For photovoltaic application, CI(G)S nanoparticle ink for solution processable high performance solar cells is presented. By overcoming the critical drawbacks of conventional solution processed CI(G)S absorber layers, the device quality dense CI(G)S layer is obtained, affording 7.3% efficiency CI(G)S photovoltaic device.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.757-762
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• 2002

Many reports have been shown that the buoyancy, electromagnetic force, surface tension, and gas shear stress are the driving forces of weld pool circulation in arc welding. Among them, the surface tension of molten metal plays an important role in the flow in weld pool, which are clarified by the specially designed experiments with small particles as well as the numerical simulations. The surface tension is also related to the penetration in arc welding. Therefore, a quantitative evaluation of surface tension is demanded for the development of materials and arc process control. However, there are few available data published on the surface tension of molten metals, since it depends on the temperature and the composition of materials. In this study, a new method was proposed for the evaluation of surface tension and its temperature dependence, in which it is evaluated by the equilibrium condition of acting forces under a given surface geometry, especially back surface. When this method was applied to the water pool and to the back surface of molten pool in the stationary gas tungsten arc welding of thin plate, following results were obtained. In the evaluation of surface tension of water, it was shown that the back surface geometry was very sensitive to the evaluation of surface tension and the evaluated value coincided with the surface tension of water. In the measurement of molten pool in the stationary gas tungsten arc welding, it was also shown that the comparison between the surface tension and temperature distribution across the back surface gave the temperature dependent surface tension. Applying this method to the mild steel and stainless steel plates, the surface tension with negative gradient for temperature is obtained. The evaluated values are well matched with ones in the published papers.

• Carbon letters
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• v.12 no.4
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• pp.207-217
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• 2011

We discuss the influence of few-walled carbon nanotubes (FWCNTs) treated with nitric acid and/or sulfuric acid on field emission characteristics. FWCNTs/tetraethyl orthosilicate (TEOS) thin film field emitters were fabricated by a spray method using FWCNTs/TEOS sol one-component solution onto indium tin oxide (ITO) glass. After thermal curing, they were found tightly adhered to the ITO glass, and after an activation process by a taping method, numerous FWCNTs were aligned preferentially in the vertical direction. Pristine FWCNT/TEOS-based field emitters revealed higher current density, lower turn-on field, and a higher field enhancement factor than the oxidized FWCNTs-based field emitters. However, the unstable dispersion of pristine FWCNT in TEOS/N,N-dimethylformamide solution was not applicable to the field emitter fabrication using a spray method. Although the field emitter of nitric acid-treated FWCNT showed slightly lower field emission characteristics, this could be improved by the introduction of metal nanoparticles or resistive layer coating. Thus, we can conclude that our spray method using nitric acid-treated FWCNT could be useful for fabricating a field emitter and offers several advantages compared to previously reported techniques such as chemical vapor deposition and screen printing.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.904-908
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• 2008

As the various industrial production machinery has come into being by development of industrial technology, the productivity of the basic industrial production machinery has improved and the international competitiveness of the one of Korea has strengthened. However, at the same time, noise from various industrial production machinery disturbs the quiet environment. There are 35 kinds of the noise emission machinery defined in the noise and vibration control act according to the horse power and the number of machinery. These were classified in 1992 through investigation from 1990 to 1991, and the characteristic of the noise emission machinery may be different from the past one. So we need to investigate the characteristics of the noise emitted by machinery to control it rightly. Also we need to investigate the new noise emission machinery which has come into being recently. In this survey, we measured sound intensity of 32 noise emission machinery to calculate the sound power levels of those and investigated the characteristic of the sound power level of those according to the frequency. From the survey, we found that the forging machine, concrete pipe and pile making machine, sawing machine, etc. are the noisy machinery. And the automatic packing machine, sewing machine, centrifuge, etc. are the silent machinery. Also the generator, the concrete pipe and pile making machine, the printing machine, etc. emit the low frequency noise, and the molding machine, the stone cutter, the metal cutter, etc. emit the high frequency noise. Lastly, we intented to propose the proper guide line of classifying noise emission machinery.

• Applied Chemistry for Engineering
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• v.5 no.3
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• pp.419-424
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• 1994

An oil stain on the steel induced by metal working oil was studied on the six kinds of fat and oil compounds(rapeseed oil, oleic acid, methyl oleate, oleyl alcohol, lauryl amino, and lanolin) by MIL-C-22235A test. The samples used for the printing on the oil stain plates were prepared by the addition of fat and oil compounds(10wt% ) and antioxidants(B. H. T, B. T, T. C. P; 0.5wt%) to base oil(spindle oil; 1.5wt% of sulfur). An analysis based on the experimental data indicated that B.T was more effective than B. H. T and T. C. P as antioxidant for inhibiting oil stains. And acid values exerted a bad influence upon the preventation of oil stains. As expected by the chemical structure of fat and oil compound, oleic acid that could react with iron ions produced more stains on the steel pannel.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.797-798
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• 2005

We report a novel structure for a full-color AMOLED (Active Matrix Organic Light Emitting Diode) eliminating the patterning process of a blue emitting layer. The patterning of the three primary colors, RGB, is a key technology in the OLED fabrication process. Conventional full color AMOLED containing RGB layers includes the three opportunities of the defects to make an accurate position and fine resolution using various technologies such as fine metal mask, ink-jet printing and laser-induced transfer system. We can skip the blue patterning step by simply stacking the blue layer as a common layer to the whole active area after pixelizing two primary colors, RG, in the conventional small molecular OLED structure. The red and green pixel showed equivalent performances without any contribution of the blue emission.