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Bong, Sungjae,Ahn, Shihyun,Anh, Le Huy Tuan,Kim, Sunbo,Park, Hyeongsik,Shin, Chonghoon,Park, Jinjoo,Lee, Younjung,Yi, Junsin American Scientific Publishers 2016 Journal of nanoscience and nanotechnology Vol.16 No.5
<P>For thin film silicon-based solar cells, effective light trapping at a broad range of wavelengths (400-1100 nm) is necessary. Normally, etching is only carried out with TCOs, such as SnO2:F and impurity doped ZnO, to form nano-sized craters in the surface morphology to confer a light trapping effect. However, in this study, prior to ZnO: Al etching, periodic structures on the glass substrates were made by photolithography and wet etching to increase the light scattering and internal reflection. The use of periodic structures on the glass substrate resulted in higher haze ratios in the range from 550 nm to 1100 nm, which is the optical absorption wavelength region for thin film silicon solar cells, than obtained by simple ZnO: Al etching. The periodically textured glass with micro-sized structures compensates for the low haze ratio at the middle and long wavelengths of wet etched ZnO: Al. ZnO: Al was deposited on the periodically textured glass, after which the ZnO: Al surface was also etched randomly using a mixed acid solution to form nano-sized craters. The thin film silicon solar cells with 350-nm-thick amorphous silicon absorber layer deposited on the periodic structured glass and etched ZnO: Al generated up to 10.68% more photocurrent, with 11.2% increase of the conversion efficiency compared to the cell deposited on flat glass and etched ZnO: Al.</P>
Ramayanti, Suci,Kim, Bong Chan,Park, Sungjae,Lee, Chang-Wook The Korean Society of Remote Sensing 2022 大韓遠隔探査學會誌 Vol.38 No.6
The availability of high-resolution satellite images provides precise information without direct observation of the research target. Korea Multi-Purpose Satellite (KOMPSAT), also known as the Arirang satellite, has been developed and utilized for earth observation. The machine learning model was continuously proven as a good classifier in classifying remotely sensed images. This study aimed to compare the performance of the support vector machine (SVM) model in classifying the land cover of the Delaware River port area on high and medium-resolution images. Three optical images, which are KOMPSAT-2, KOMPSAT-3A, and Sentinel-2B, were classified into six land cover classes, including water, road, vegetation, building, vacant, and shadow. The KOMPSAT images are provided by Korea Aerospace Research Institute (KARI), and the Sentinel-2B image was provided by the European Space Agency (ESA). The training samples were manually digitized for each land cover class and considered the reference image. The predicted images were compared to the actual data to obtain the accuracy assessment using a confusion matrix analysis. In addition, the time-consuming training and classifying were recorded to evaluate the model performance. The results showed that the KOMPSAT-3A image has the highest overall accuracy and followed by KOMPSAT-2 and Sentinel-2B results. On the contrary, the model took a long time to classify the higher-resolution image compared to the lower resolution. For that reason, we can conclude that the SVM model performed better in the higher resolution image with the consequence of the longer time-consuming training and classifying data. Thus, this finding might provide consideration for related researchers when selecting satellite imagery for effective and accurate image classification.
Park, Jinjoo,Shin, Chonghoon,Park, Hyeongsik,Jung, Junhee,Lee, Youn-Jung,Bong, Sungjae,Dao, Vinh Ai,Balaji, Nagarajan,Yi, Junsin American Scientific Publishers 2015 Journal of nanoscience and nanotechnology Vol.15 No.3
<P>We investigated thin film silicon solar cells with boron doped hydrogenated nanocrystalline silicon/ hydrogenated amorphous silicon oxide [p-type nc-Si:H/a-SiOx:H] layer. First, we researched the bandgap engineering of diborane (B2H6) doped wide bandgap hydrogenated nanocryslline silicon (p-type nc-Si:H) films, which have excellent electrical properties of high dark conductivity, and low activation energy. The films prepared with lower doping ratio and higher hydrogen dilution ratio had higher optical gap (Eg), with higher dark conductivity (??(d)), and lower activation energy (Ea). We controlled Eg from 2.10 eV to 1.75 eV, with ??(d) from 1.1 S/cm to 7.59 x 10(-3) S/cm, and Ea from 0.040 eV to 0.128 eV. Next, we focused on the fabrication of thin film silicon solar cells. By inserting p-type nc-Si:H film into the thin film silicon solar cells, we achieved a remarkable increase in the built-in potential from 0.803 eV to 0.901 eV. By forming p-type nc-Si:H film between SnO2:F/ZnO:Al (30 nm) and p-type a-SiOx:H layer, the solar cell properties of open circuit voltage (Voc), short circuit current density (Jsc), and efficiency (관) were improved by 3.7%, 9.2%, and 9.8%, respectively.</P>
Shin, Chonghoon,Park, Jinjoo,Kim, Sangho,Park, Hyeongsik,Jung, Junhee,Bong, Sungjae,Lee, Youn-Jung,Yi, Junsin American Scientific Publishers 2014 Journal of nanoscience and nanotechnology Vol.14 No.12
<P>Highly conducting boron-doped microcrystalline silicon (p-type μc-Si:H) thin films have been prepared by radio frequency plasma-enhanced chemical-vapor deposition (RF-PECVD). In this work, the effects of hydrogen dilution, doping ratio, plasma power, deposition pressure and substrate temperature on the growth and the properties of boron-doped microcrystalline silicon (p-type μc-Si:H) thin films are investigated. The electrical, chemical and structural properties are improved with increasing crystallite, which depends on the plasma conditions. For various plasma parameters, the crystalline volume fraction (X(c)), dark conductivity (σ(d)), activation energy (E(a)), hydrogen content (C(H)), surface roughness (S(r)), and micro void fraction (R*) were measured, and they were 0-72%, 4.17-10(-4) S/cm-1.1 S/cm, 0.041-0.113 eV, 3.8-11.5 at.%, 3.2 nm-12.2 nm, and 0.47-0.80, respectively. The film with R* of 0.47 and C(H) of about 5 at.% belonged to a region of low disorder, and acted as a good passivation layer.</P>
Present Status and Prospects of Thin Film Silicon Solar Cells
Iftiquar, Sk Md,Park, Jinjoo,Shin, Jonghoon,Jung, Junhee,Bong, Sungjae,Dao, Vinh Ai,Yi, Junsin Korea Photovoltaic Society 2014 Current Photovoltaic Research Vol.2 No.2
Extensive investigation on silicon based thin film reveals a wide range of film characteristics, from low optical gap to high optical gap, from amorphous to micro-crystalline silicon etc. Fabrication of single junction, tandem and triple junction solar cell with suitable materials, indicate that fabrication of solar cell of a relatively moderate efficiency is possible with a better light induced stability. Due to these investigations, various competing materials like wide band gap silicon carbide and silicon oxide, low band gap micro-crystalline silicon and silicon germanium etc were also prepared and applied to the solar cells. Such a multi-junction solar cell can be a technologically promising photo-voltaic device, as the external quantum efficiency of such a cell covers a wider spectral range.
Present Status and Prospects of Thin Film Silicon Solar Cells
Sk Md Iftiquar,Jinjoo Park,Jonghoon Shin,Junhee Jung,Sungjae Bong,Vinh Ai Dao,Junsin Yi 한국태양광발전학회 2014 Current Photovoltaic Research Vol.2 No.2
Extensive investigation on silicon based thin film reveals a wide range of film characteristics, from low optical gap to high optical gap, from amorphous to micro-crystalline silicon etc. Fabrication of single junction, tandem and triple junction solar cell with suitable materials, indicate that fabrication of solar cell of a relatively moderate efficiency is possible with a better light induced stability. Due to these investigations, various competing materials like wide band gap silicon carbide and silicon oxide, low band gap micro-crystalline silicon and silicon germanium etc were also prepared and applied to the solar cells. Such a multi-junction solar cell can be a technologically promising photo-voltaic device, as the external quantum efficiency of such a cell covers a wider spectral range.
Fabrication of ZnO nanorods for gas sensing applications using hydrothermal method.
Nguyen, Cam Phu Thi,La, Phan Phuong Ha,Trinh, Thanh Thuy,Le, Tuan Anh Huy,Bong, Sungjae,Jang, Kyungsoo,Ahn, Shihyun,Yi, Junsin American Scientific Publishers 2014 Journal of nanoscience and nanotechnology Vol.14 No.8
<P>We showed well-aligned zinc oxide (ZnO) nanorod arrays synthesized using hydrothermal method at atmospheric pressure. The influence of fabrication conditions such as Zn2+/hexamethylentriamin concentration ratio, and growth temperature on the formation of ZnO nanorods was investigated. Scanning Electron Microscope (SEM) images and X-ray Diffraction (XRD) analysis were used to confirm the single crystal of ZnO nanorods, which showed wurtzite structure with growth direction of [0001] (the c-axis). Photoluminescence (PL) measurements of ZnO nanorods revealed an intense ultraviolet peak at 388.5 nm (3.19 eV) at room temperature. The results showed that the ZnO seed layers had strong influence on the growth of vertically aligned ZnO nanorods. The gas sensor based on ZnO nanorod arrays had the most selectivity with n-butanol gas (within 2 surveyed gas: ethanol and n-butanol) and showed a higher sensitivity of 222, fast response time of 15 seconds, recovery time of 110 seconds and lower operating temperature of 200-250 C than the sensor based on the ZnO film in the same detecting conditions.</P>
박형식(Hyeongsik Park),신명훈(Myunghoon Shin),안시현(Shihyun Ahn),김선보(Sunbo Kim),봉성재(Sungjae Bong),Anh Le Tuan,S. Q. Hussain,이준신(Junsin Yi) 한국태양광발전학회 2014 Current Photovoltaic Research Vol.2 No.3
Light trapping techniques can change the propagation direction of incident light and keep the light longer in the absorption layers of solar cells to enhance the power conversion efficiency. In thin film silicon (Si) solar cells, the thickness of absorption layer is generally not enough to absorb entire available photons because of short carrier life time, and light induced degradation effect, which can be compensated by the light trapping techniques. These techniques have been adopted as textured transparent conduction oxide (TCO) layers randomly or periodically textured, intermediate reflection layers of tandem and triple junction, and glass substrates etched by various patterning methods. We reviewed the light trapping techniques for thin film Si solar cells and mainly focused on the commercially available techniques applicable to textured TCO on patterned glass substrates. We described the characterization methods representing the light trapping effects, texturing of TCO and showed the results of multi-scale textured TCO on etched glass substrates. These methods can be used tandem and triple thin film Si solar cells to enhance photo-current and power conversion efficiency of long term stability.