• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.425-428
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• 2011

This paper presents a micro-scale solar energy harvesting circuit with a simple MPPT control. Solar Energy is harvested using a small off-chip PV cell generating output voltages under 0.5V instead of an on-chip PV cell. A simple MPPT is implemented using a pilot PV cell and utilizing the relationship between the open-circuit voltage of a PV cell ($V_{OC}$) and its MPP voltage ($V_{MPP}$). With applying the MPPT control, the designed circuit delivers the MPP voltage to load even though the loads is heavy such that the load circuit can operate properly. The proposed circuit is designed in TSMC 0.18um CMOS process.

• Bulletin of the Korean Chemical Society
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• v.28 no.12
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• pp.2333-2337
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• 2007

Nanoporous TiO2 and ZrO2 thin films were spin-coated using a surfactant-templated approach from Pluronic P123 (EO20PO70EO20) as the templating agent, titanium alkoxide (Ti(OC4H9)4) as the inorganic precursor, and butanol as a the solvent. The control of the electronic structure of TiO2 is crucial for its various applications. We found that the band gap of the hybrid nanoporous thin films can be easily tuned by adding an acetylacetonestabilized Zr(OC4H9)4 precursor to the precursor solution of Ti(OC4H9)4. Pores with a diameter of 5 nm-10 nm were randomly dispersed and partially connected to each other inside the films. TiO2 and ZrO2 thin films have an anatase structure and tetragonal structure, respectively, while the TiO2-ZrO2 hybrid film exhibited no crystallinity. The refractive index was significantly changed by varying the atomic ratio of titanium to zirconium. The band gap for the nanoporous TiO2 was estimated to 3.43 eV and that for the TiO2-ZrO2 hybrid film was 3.61 eV.

• Korean Journal of Materials Research
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• v.23 no.1
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• pp.35-40
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• 2013

In this study, the influence on the surface passivation properties of crystalline silicon according to silicon wafer thickness, and the correlation with a-Si:H/c-Si heterojunction solar cell performances were investigated. The wafers passivated by p(n)-doped a-Si:H layers show poor passivation properties because of the doping elements, such as boron(B) and phosphorous(P), which result in a low minority carrier lifetime (MCLT). A decrease in open circuit voltage ($V_{oc}$) was observed when the wafer thickness was thinned from $170{\mu}m$ to $50{\mu}m$. On the other hand, wafers incorporating intrinsic (i) a-Si:H as a passivation layer showed high quality passivation of a-Si:H/c-Si. The implied $V_{oc}$ of the ITO/p a-Si:H/i a-Si:H/n c-Si wafer/i a-Si:H/n a-Si:H/ITO stacked layers was 0.715 V for $50{\mu}m$ c-Si substrate, and 0.704 V for $170{\mu}m$ c-Si. The $V_{oc}$ in the heterojunction solar cells increased with decreases in the substrate thickness. The high quality passivation property on the c-Si led to an increasing of $V_{oc}$ in the thinner wafer. Short circuit current decreased as the substrate became thinner because of the low optical absorption for long wavelength light. In this paper, we show that high quality passivation of c-Si plays a role in heterojunction solar cells and is important in the development of thinner wafer technology.

• Electric Engineers Magazine
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• v.256 no.12
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• pp.24-30
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• 2003

22.9KV 수, 변전설비의 노출충전부로부터 감전 재해를 예방하기 위하여 사용되는 절연커버 및 OC전선은 각각의 제조회사마다 상이한 절연재료를 사용하고 있다. 이러한 절연커버 및 OC 전선은 사용 여건상 한번 설치하면 소손 및 파괴가 일어날 때까지 사용하기 때문에 염해, 분진 등 이물질이 항시 존재하는 열악한 환경에 장기간 노출되더라도 내아크성, 내후성 및 내열성 등에 우수한 특성을 갖도록 설계될 필요성이 있다

• Journal of Electrochemical Science and Technology
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• v.2 no.2
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• pp.110-115
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• 2011

The effect of $TiO_2$ nanotube (TNT) and nanoparticle (TNP) composite photoelectrode and the role of TNT to enhance the photo conversion efficiency in dye-sensitized solar cell (DSSC) have investigated in this study. Results demonstrated that the increase of the TNT content (1-15 %) into the electron collecting TNP film increases the open-circuit potential ($V_{oc}$) and short circuit current density ($J_{sc}$). Based on the impedance analysis, the increased $V_{oc}$ was attributed to the suppressed recombination between electrode and electrolyte or dye. Photochemical analysis revealed that the increased Jsc with the increased TNT content was due to the scattering effect and the reduced electron diffusion path of TNT. The highest $J_{sc}$ (12.6 mA/$cm^2$), Voc (711 mV) and conversion efficiency (5.9%) were obtained in the composite photoelectrode with 15% TNT. However, $J_{sc}$ and $V_{oc}$ was decreased for the case of 20% TNT, which results from the significant reduction of adsorbed dye amount and the poor attachment of the film on the fluorine-doped tin oxide (FTO). Therefore, application of this composite photoelectrode is expected to be a promising approach to improve the energy conversion efficiency of DSSC.

• Pediatric Infection and Vaccine
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• v.14 no.1
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• pp.69-74
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• 2007

Purpose : Human coronanviruses (hCovs) including hCoV-229E and hCoV-OC43 have been known as etiologic agents of the common colds and were regarded as clinically insignificant agents. However, recent identification of hCoV-NL63 and hCoV-HKU1 in children with lower respiratory tract infections has evoked the clinical concerns about their prevalence and the clinical significance of these hCoVs in children. This study was performed to investigate the prevalence of hCoVs in children with community-acquired pneumonia. Methods : From March 2006 to January 2007, nasopharyngeal specimens collected from children hospitalized with pneumonia, were tested for the presence of common respiratory viruses (respiratory syncytial virus, influenza A, influenza B, parainfluenza viruses, and adenovirus) using multiplex reverse transcriptase polymerase chain reaction (RT-PCR). Human metapneumovirus (hMPV) infection was excluded by nested RT-PCR using primers for the F-gene. To detect the different strains of hCoVs, nested RT-PCR assays specific for hCoVNL63, hCoV-OC43, hCoV-229E, and hCoV-HKU1 were performed. Results : Out of the 217 nasopharyngeal aspirate from children aged under 15 years, respiratory syncytial virus (RSV) was detected in 32 patients, hMPV in 18, human parainfluenza virus in 10, influenza virus A in 2, and adenovirus in 6. HCoVs were detected by RT-PCR in 8 (3.7%) of the 217 patients, hCoV-229E in 1, hCoV-NL63 in 3, and hCoVOC43 in 4 patients. HCoV-HKU1 was not detected in this study population. Conclusion : Recently identified hCoV-NL63 and hCoV-HKU1 seemed to have a little clinical significance in Korean children with severe or hospitalized community-acquired pneumonia.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.10
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• pp.1694-1696
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• 2016

Present thin film solar cells with hydrogenated amorphous silicon oxide (a-SiO:H) as an absorber suffer from low fill factor(FF) of 61~64 [%] in spite of its benefits related to high open circuit voltage ($V_{oc}$). Since degraded quality of a-SiO:H absorber by alloying with oxygen can affect the FF, we aimed to achieve high photosensitivity by minimizing $CO_2$ gas addition. Improving optical gap($E_{opt}$) has been attained by strong hydrogen dilution combined with lowering substrate temperature down to 100 [$^{\circ}C$]. Small amount of the $CO_2$ was added in order to disturb microcrystalline formation by high hydrogen dilution. The developed a-SiO:H has high photosensitivity (${\sim}2{\times}10^5$) and high $E_{opt}$ of 1.85 [eV], which contributed to attain remarkable FF of 74 [%] and high $V_{oc}$ (>1 [V]). As a result, high power conversion efficiency of 7.18 [%] was demonstrated by using very thin absorber layer of only 100 [nm], even though we processed all experiment at extremely low temperature of 100 [$^{\circ}C$].

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.11
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• pp.104-108
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• 2012

Flexible organic thin film solar cell device with Bulk Hetero-Junction (BHJ) structure was fabricated with blended conjugated polymer of PCDTBT : $PC_{71}BM$ as active layer. Surface of ITO anode for the organic solar cell device was treated with ozone. The organic solar cell device with bare ITO showed short circuit current density ($J_{sc}$) of $8.2mA/cm^2$, open-circuit voltage ($V_{oc}$) of 0.73V, fill factor (FF) of 0.36, and power conversion efficiency (PCE) of 2.16%, respectively. The organic solar cell device with ozone treated ITO anode revealed distinctively improved performance parameters:$J_{sc}$ of $9.8mA/cm^2$, $V_{oc}$ of 0.82V, FF of 0.43, PCE(${\eta}$) of 3.42%.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.1
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• pp.100-104
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• 2011

In this work, an optimum condition of electrolytes preparation for photovoltaic cells application was investigated experimentally in terms of impedance and conversion efficiency of the cells. 3-methoxyppropionitrie and redox pairs with LiI and $I_2$ were used as stable solvents for fabrication of electrolyte. Efficiency comparison of the prepared cells carried out for various additives and ionic liquids. From the results, there was an optimum concentration (about 0.3 M) of ionic liquids for efficient cell fabrication. For case of electrolyte using single DMAp additive, the maximum conversion efficiency of the cell was 6.4%($V_{oc}$: 0.78V, $J_{sc}$: 14.4 mA/$cm^2$, ff: 0.57). For case of electrolyte using both DMAp and CEMim additives, the maximum conversion efficiency of the cell was 7.2%($V_{oc}$: 0.79V, $J_{sc}$: 16 mA/$cm^2$, ff: 0.57). From the result of electrochemical impedance measurement, both Z1 and Z3 values of binary additives-based cell decreased compared to those of single additive-based. This is due to the decreased in internal and charge transfer resistivities of the cells.

• Journal of the Semiconductor & Display Technology
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• v.12 no.3
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• pp.47-51
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• 2013

Current research trends of solar cells has focused on the high conversion efficiency and low-cost production technology. Passivation technology that can be easily adapted to mass production. Therefore, this study conducted experiments with aim of the following two methods for the fabrication of high-efficiency crystalline silicon solar cells. In the first task, an attempt is formation of local Al-BSF to a number of locally doped dots to increase the conversion efficiency of solar cells to reduce the loss of $V_{oc}$ overcome. The second major task, rear surface apply in $Al_2O_3/SiN_x$ stack layer, $Al_2O_3$ prominent negative fixed charge characteristics. As the result of task, Local Al-BSF and $Al_2O_3/SiN_x$ stack layer applied to the p-type single crystalline silicon solar cells, the average $V_{oc}$ of 644mV, $I_{sc}$ of 918mV and conversion efficiency of 18.70% were obtained.