• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.3
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• pp.551-558
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• 2021

In this paper, we made the integrated intelligent air ventilation of the actuator module that can be remotely controlled based on IoT and sensors. we implemented a ventilation window system by configuring an algorithm design and a driving circuit to control the operation of the actuator to open and close the ventilation port based on a predetermined number of data that detects indoor gas/CO2/humidity temperature and outdoor fine dust related indoor/outdoor environment. It is difficult to store, manage, and analyze data due to the large number of sensors and conditions for the transmission data of indoor air circulation module. The remote monitoring and remote wireless control screens were constructed to automate the separation and operation conditions by extracting and managing the state. We apply MQTT to enhance big data transmission and construct the system using Rocket MQ to ensure safe transmission of operational big data against system errors.

• Journal of IKEEE
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• v.23 no.2
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• pp.538-542
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• 2019

Semiconductor oxides such as $TiO_2$ involved in light conversion efficiency are the main elements of dye-sensitized solar cells (DSSC) and are used to mix different semiconductor oxides to improve efficiency. In this research, characteristics of the dye-sensitive solar cell are studied using semiconductor oxide formed by mixing $TiO_2$ and $Nb_2O_5$. A solar cell is manufactured by adding $Nb_2O_5$ at different ratios in order to analyze electrical characteristics of a mixed semiconductor oxide on light conversion efficiency. With the addition of $Nb_2O_5$, the conductivity was further enhanced than the recombination phenomenon caused by contact with electrolytes, confirming the improve of short-circuit, open voltage, and conversion efficiency of solar cells.

• Korean Journal of Materials Research
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• v.29 no.3
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• pp.183-188
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• 2019

Flexible dye-sensitized solar cells using binder free $TiO_2$ paste for low temperature sintering are developed. In this paste a small amount of titanium gel is added to a paste of $TiO_2$ nanoparticle. Analysis of titanium gel paste prepared at $150^{\circ}C$ shows that it has a pure anatase phase in XRD and mesoporous structure in SEM. The formation of the titanium gel 1-2 nm coated layer is confirmed by comparing the TEM image analysis of the titanium gel paste and the pristine paste. This coating layer improves the excited electron transfer and electrical contact between particles. The J-V curves of the organic binder DSSCs fabricated at $150^{\circ}C$ shows a current density of $0.12mA/cm^2$ and an open-circuit voltage of 0.47 V, while the titanium gel DSSCs improves electrical characteristics to $5.04mA/cm^2$ and 0.74 V. As a result, the photoelectric conversion efficiency of the organic binder DSSC prepared at low temperature is as low as 0.02 %, but the titanium gel paste DSSCs has a measured effciency of 2.76 %.

• Asian-Australasian Journal of Animal Sciences
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• v.32 no.9
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• pp.1389-1396
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• 2019

Objective: The current study analysed the relationships between methane ($CH_4$) output from animal and dietary factors. Methods: The dataset was obtained from 159 Dorper${\times}$thin-tailed Han lambs from our seven studies, and $CH_4$ production and energy metabolism data were measured in vivo by an opencircuit respiratory method. All lambs were confined indoors and fed pelleted diet during the whole experimental period in all studies. Data from two-thirds of lambs were used to develop linear and multiple regressions to describe the relationship between $CH_4$ emission and dietary variables, and data from the remaining one third of lambs were used to validate the established models. Results: $CH_4$ emission (g/d) was positively related to dry matter intake (DMI) and gross energy intake (GEI) (p<0.001). $CH_4$ energy/GEI was negatively related to metabolizable energy/gross energy and metabolizable energy/digestible energy (p<0.001). Using DMI to predict $CH_4$ emission (g/d) resulted in a coefficient of determination ($R^2$) of 0.80. Using GEI, digestible energy intake, and metabolizable energy intake predict $CH_4$ energy/GEI resulted in a $R^2$ of 0.92. Conclusion: the prediction equations established in the current study are useful to develop appropriate feeding and management strategies to mitigate $CH_4$ emissions from sheep.

• Journal of the Korean Solar Energy Society
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• v.39 no.3
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• pp.9-17
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• 2019

Laser cutting cell of solar cells can achieve high voltage and efficiency through more array than conventional 6 inch cell compared to same area. In this study, we fabricated c-Si cutting cell with various lasers and laser conditions such as power, speed, and number of times. In the case of picosecond laser, excellent surface characteristics were obtained due to small surface defects and low thermal damage at the output of 20W and the speed of 100 mm/s. However, it is not possible to fabricate a cutting cell having good characteristics due to nonuniform cutting inside the wafer when the processing for forming a cutting cell is not sufficiently performed. For nanosecond lasers, the best wafer characteristics were obtained for fabrication of excellent cutting cells at a frequency of 500 kHz and a laser speed of 100 mm/s. However, the nanosecond laser has not been processed sufficiently in the condition of a number of times. As a result, it was confirmed that the wafer thickness was cut by $63{\mu}m$ of the cell thickness of $170{\mu}m$ in the condition of five times of laser process. It was found that more than 30% of the wafer thickness had to be processed to fabricate the cutting cell. After cutting the 6-inch cell having the voltage of 0.65 V, we obtained the voltage of about 0.63 V.

• Current Photovoltaic Research
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• v.7 no.3
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• pp.55-60
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• 2019

Polymer:nonfullerene solar cells with an inverted-type device structure were fabricated by employing the bulk heterojunction (BHJ) active layers, which are composed of poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophene-2-yl)-benzo[1,2-b:4,5-b']dithiophene))-alt-(5,5-(1',3'-di-2-thienyl-5',7-bis(2-ethylhexyl)benzo[1',2'-c:4',5'-c']dithiophene-4,8-dione))] (PBDB-T) and 3,9-bis(6-methyl-2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2',3-d']-s-indaceno[1,2-b:5,6-b']dithiophene (IT-M). The BHJ layers were formed on a pre-patterned indium-tin oxide (ITO)-coated glass substrate by spin-coating using the blend solutions of PBDB-T and IT-M. The solar cell performances were investigated with respect to the cell position on the ITO-glass substrates. In addition, the short-term shelf lifetime of solar cells was tested by storing the PBDB-T:IT-M solar cells in a glovebox filled with inert gas. The results showed that the performance of solar cells was relatively higher for the cells close to the center of substrates, which was maintained even after storage for 24 h. In particular, the PCE of PBDB-T:IT-M solar cells was marginally decreased after storage for 24 h owing to the slightly reduced fill factor, even though the open circuit voltage was unchanged after 24 h.

• Journal of IKEEE
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• v.23 no.1
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• pp.330-333
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• 2019

Various studies on dye-sensitized solar cells, which are cheaper to manufacture and have superior stability than silicon solar cells, are continuously conducted. In this study, the properties of dye-sensitized solar cells were studied using semiconductor oxides made by mixing $TiO_2$ and $Nb_2O_5$. By adding $Nb_2O_5$ in different proportions, the solar cell was made, and the surface area and electrical characteristics of this cell were measured. As $Nb_2O_5$ was added, the contact area of dye and electrolyte increased and the short-circuit current, open voltage, fill factor and conversion efficiency of dye-sensitized solar cells were confirmed to be improved.

• Korean Journal of Materials Research
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• v.29 no.5
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• pp.322-327
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• 2019

Hole carrier selective MoOx film is obtained by atomic layer deposition(ALD) using molybdenum hexacarbonyl[$Mo(CO)_6$] as precursor and ozone($O_3$) oxidant. The growth rate is about 0.036 nm/cycle at 200 g/Nm of ozone concentration and the thickness of interfacial oxide is about 2 nm. The measured band gap and work function of the MoOx film grown by ALD are 3.25 eV and 8 eV, respectively. X-ray photoelectron spectroscopy(XPS) result shows that the $Mo^{6+}$ state is dominant in the MoOx thin film. In the case of ALD-MoOx grown on Si wafer, the ozone concentration does not affect the passivation performance in the as-deposited state. But, the implied open-circuit voltage increases from $576^{\circ}C$ to $620^{\circ}C$ at 250 g/Nm after post-deposition annealing at $350^{\circ}C$ in a forming gas ambient. Instead of using a p-type amorphous silicon layer, high work function MoOx films as hole selective contact are applied for heterojunction silicon solar cells and the best efficiency yet recorded (21 %) is obtained.

• Current Applied Physics
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• v.18 no.12
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• pp.1571-1576
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• 2018

Recent study shows that the main reason for limiting CZTS device performance lies in the low open circuit voltage, and crucial factor that could affect the $V_{oc}$ is secondary phases like ZnS existing in absorber layer and its interfaces. In this work, the $Cu_2ZnSnS_4$ thin film solar cells were prepared by sputtering CuSn and CuZn alloy targets. Through tuning the Zn/Sn ratios of the CZTS thin films, the crystal structure, morphology, chemical composition and phase purity of CZTS thin films were characterized by X-Ray Diffraction (XRD), scanning electron microscopy (SEM) equipped with an energy dispersive spectrometer (EDS) and Raman spectroscopy. The statistics data show that the CZTS solar cell with a ratio of Zn/Sn = 1.2 have the best power convention efficiency of 5.07%. After HCl etching process, the CZTS thin film solar cell with the highest efficiency 5.41% was obtained, which demonstrated that CZTS film solar cells with high efficiency could be developed by sputtering CuSn and CuZn alloy targets.

• Korean Journal of Metals and Materials
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• v.50 no.9
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• pp.685-690
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• 2012

Decalcomania is a new method for SOFCs (solid oxide fuel cells) unit cell fabrication. A tight and dense $5{\mu}m$ Yttria-stabilized zirconia (8YSZ) electrolyte layer on anode substrate was fabricated by the decalcomania method. After 8YSZ as the electrolyte starting material was calcined at $1200^{\circ}C$, the particle size was controlled by the attrition mill. The median particle size (D50) of each 8YSZ was $39.6{\mu}m$, $9.30{\mu}m$, $6.35{\mu}m$, and $3.16{\mu}m$, respectively. The anode substrate was coated with decalcomania papers which were made by using 8YSZ with different median particle sizes. In order to investigate the effect of median particle sizes and sintering conditions on the electrolyte density, each sample was sintered for 2, 5 and 10 h, respectively. 8YSZ with a median particle size of $3.16{\mu}m$ which was sintered at $1400^{\circ}C$ for 10 had the highest density. With this 8YSZ, a SOFCs unit cell was manufactured with a $5{\mu}m$ layer by the decalcomania method. Then the unit cell was run at $800^{\circ}C$. The Open Circuit Voltage (OCV) and Maximum power density (MPD) was 1.12 V and $650mW/cm^2$, respectively.