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RISS 인기검색어
- 검색키워드
- 저자 : (Shuichi Kawai) (검색결과 3 건)
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Nano-scale current voltage characteristics of thin film solar cell with light irradiations
Masato Kawai,Tomohiro Kawakami,Tomoya Inaba,Fumitaka Ohashi,Hironori Natsuhara,Takashi Itoh,Shuichi Nonomura 한국물리학회 2010 Current Applied Physics Vol.10 No.3
Nano-scale current voltage (I–V) characteristics of hydrogenated amorphous silicon (a-Si:H) solar cells were studied with and without light irradiations by using conductive Atomic Force Microscope (conductive-AFM). To obtain proper I–V characteristics, electrical contacts between the n-layer of the a-Si solar cells and the cantilever of the AFM were modified by depositing ZnO films with the thickness of 20 nm on the tip using DC sputterer. The I–V characteristics were changed from Schottky like to ohmic like. Surface defects and grain boundaries of the ZnO thin film possibly formed an ohmic-like current path between n-layer and the tip of the cantilever. We measured photo-current map at the bias of -2 V with a resolution of nano-meter scales. High photo-current paths appeared at nano-crystallites formed in the nc-Si:H film of the solar cell while small current area was observed at the boundaries of the small and large grains. This suggests that the boundaries have high impedance created by hydrogen passivation or act as a leakage current path for the photo-current recombination. These results imply that our proposed measurement technique using conductive-AFM combined with covering of ZnO film on the cantilever is a useful tool for the evaluation of the short path of the photo-current. In addition, these techniques contribute to increase the conversion efficiency of thin film solar cells.
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Suh, Jin Suk,Hermawan, Dede,Kawai, Shuichi 한국목재공학회 2000 목재공학 Vol.28 No.4
Cement-bonded particleboard is being used as outdoor siding material all over the world, because this composite particularly bears a light weight, high resistance against fire, decay, and crack by cyclic freezing and thawing, anti-shock property, and strength enhancement. Construction systems are currently changing into a frame-building style and wooden houses are being constructed with prefabrication type. Therefore, they require a more durability at outdoor-exposed sides. In this study, the cement hydration property for Korean pine particle, Japanese larch particle and face-and middle layer particles (designated as PB particle below) used in Korean particleboard-manufacturing company was investigated, and the rapid manufacturing characteristics of cement-bonded particleboard by supercritical CO₂ curing was evaluated. Korean pine flour showed a good hydration property, however, larch flour showed a bad one. PB particle had a better hydration property than larch flour. The addition of Na₂SiO₃ indicated a negative effect on hydration, however, MgCl₂ had a positive one. Curing by supercritical CO₂ fluid gave a conspicuous enhancement in the performances of cement-bonded particleboards compared to conventional curing. MgCl₂ 3%-added PB particle had the highest properties, and MgCl₂1%-added Korean pine particle had the second class with the conditions of cement/wood ratio of 2.7, a small fraction-screened particle and supercritical curing. On the contrary, the composition of non-hammermilled or large fraction-screened particle at cement/wood ratio of 2.2 was poorer. Also, the feasibility for actual use of 3%-added, small PB particle-screened fraction was greatest of all the conventional curing treatments. Relative superiority of supercritical curing vs, conventional curing at dimensional stability was not so apparent as in strength properties. Through the thermogravimetric analysis, it was ascertained that the peak of a component CaCO₃ was highest, and the two weak peaks of calcium silicate hydrate and ettringite and Ca(OH)₂were present in supercritical treatment. Accordingly, it was inferred that the increased formation of carbonates in board contributes to strength enhancement.
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