We have developed thin film amorphous silicon alloy (a-Si:H) and nanocrystalline silicon (nc-Si:H) based multijunction solar cells on lightweight polymer substrate ~25 μm thick for space and ...near-space applications. The baseline cells use an a-Si:H/a-SiGe:H/a-SiGe:H structure deposited by conventional Radio Frequency (RF) plasma enhanced CVD using roll-to-roll deposition. The best initial performance for the baseline cells is aperture-area efficiency 9.84% and specific power ~1200 W/kg. The baseline cells are available to potential customers in large quantities. In order to increase the solar cell efficiency, we have pursued two new approaches. In the first, we use a Modified Very High Frequency (MVHF) technique to deposit the multijunction a-SiGe:H based cells. In the second, we have investigated nc-Si:H based multijunction cells. In this paper, we present the solar cell efficiency results on the three different device structures.
Summary form only given. Hydrogenated nanocrystalline silicon (nc-Si:H) has become a promising candidate to replace hydrogenated amorphous silicon-germanium alloy (a-SiGe:H) in multijunction thin ...film silicon solar cells due to its superior long-wavelength response and stability against light-induced degradation. Due to the indirect band gap in crystalline silicon, the absorbing nc-Si:H layer needs to be much thicker than the corresponding a-SiGe:H layer. For nc-Si:H based solar cells to be commercially viable, the greatest challenge is to deposit the absorbing layers at a high rate with good spatial uniformity, while maintaining the same superior quality achieved at lower deposition rate. In this paper, we report on the development of our proprietary High Frequency (HF) glow discharge deposition technology to fabricate high efficiency, large area, a-Si:H/nc-Si:H/nc-Si:H triple-junction solar cells at a high deposition rate ≥1 nm/s. We have improved our nc-Si:H and a-Si:H processes to fabricate high performance component cells used in the triple-junction solar cells. We have fabricated small area cells (0.25 cm 2 ) and mini module (1.2 cm 2 ) cut out from the large deposited area. We have attained initial, active-area efficiency as high as ~14.0% and light-stabilized, active-area efficiency ~12.8% on these cells. SIMS analysis on the device show low impurity levels in the nc-Si:H absorbing layers. We have also fabricated large area encapsulated modules. We have attained initial aperture-area (~212 cm 2 ) efficiency of ~11.8% on an encapsulated module. These are the highest values measured at United Solar for such high rate samples. Detailed results will be presented at the conference.
Hydrogenated nanocrystalline silicon (nc-Si:H) is a promising candidate to replace the hydrogenated amorphous silicon-germanium alloy (a-SiGe:H) in multijunction thin-film silicon solar cells due to ...its superior long-wavelength response and stability against light-induced degradation. Due to its indirect bandgap, the absorbing nc-Si:H layer needs to be much thicker than its amorphous counterpart. For nc-Si:H-based solar cells to be commercially viable, the challenge is to deposit the nc-Si:H layer at a high rate with good quality. In this paper, we report on the development of our proprietary high-frequency glow discharge deposition technology to fabricate high-efficiency, large-area, a-Si:H/nc-Si:H/nc-Si:H triple-junction solar cells at a high deposition rate >;1 nm/s. The National Renewable Energy Laboratory (NREL) has confirmed stable efficiency of 12.41% on a 1.05-cm 2 solar cell. We have attained initial efficiency of 12.33% on an encapsulated cell of aperture area ~400 cm 2 ; the corresponding stable efficiency is projected to be 11.7-11.9%.
Because of its superior long-wavelength response and stability against light-induced degradation, hydrogenated nanocrystalline silicon (nc-Si:H) has become a promising candidate to replace ...hydrogenated amorphous silicon-germanium alloy (a-SiGe:H) in multijunction thin-film silicon solar cells. In this paper, we report on the development of our proprietary high-frequency (HF) glow discharge deposition technology for nc-Si:H solar cells that has resulted in high-quality nc-Si:H materials with good spatial uniformity. We studied the HF-deposited nc-Si:H material using various analytical techniques. We fabricated a-Si:H/nc-Si:H/nc-Si:H triple-junction solar cells that are deposited on textured Ag/ZnO back reflectors. Large-area cells were fabricated and encapsulated using our proprietary lightweight flexible encapsulants. National Renewable Energy Laboratory (NREL) has confirmed (1) initial aperture-area efficiency of 11.8% on an 807.8-cm 2 encapsulated cell and (2) stable aperture-area efficiency of 11.2% on a 400-cm 2 encapsulated cell.
We present our progress in attaining high efficiency nc-Si:H solar cells at high deposition rates with superior light soaking stability. We have focused our effort on three areas: (i) improving the ...spatial uniformity and homogeneous properties for nc-Si:H, such as crystallite grain size and volume fraction, (ii) optimizing nucleation and seed layer during the initial growth of the nc-Si:H film, and (iii) optimizing nc-Si:H bulk growth and grain evolution. We have conducted an extensive study of the effect of process parameters including hydrogen dilution profiling, VHF power, and substrate temperature on the nc-Si:H film properties and component cell characteristics. We also conducted light soaking tests both indoors and outdoors. The a-Si:H/nc-Si:H/nc-Si:H triple-junction cells incorporating the optimized nc-Si:H component cells show significantly higher performance, achieving an 11.2% AM1.5 stabilized efficiency for both encapsulated large-area (464 cm 2 ) cells and inter-connected modules (2320 cm 2 ). To the best of our knowledge, this is the highest stabilized efficiency for a large-area thin-film silicon module.
Hydrogenated nanocrystalline silicon (nc-Si:H) has become a promising candidate to replace hydrogenated amorphous silicon-germanium alloy (a-SiGe:H) in multijunction thin film silicon solar cells due ...to its superior long-wavelength response and stability against light-induced degradation. In this paper, we report on the development of our proprietary High Frequency (HF) glow discharge deposition technology for nc-Si:H solar cells that has resulted in high quality nc-Si:H materials with good spatial uniformity. We have studied the HF-deposited nc-Si:H material using various analytical techniques, such as X-ray diffraction, Secondary Ion Mass Spectrometry, and Glow Discharge Mass Spectrometry, and optimized the deposition parameters for best device quality. We conducted a systematic study of the quality and spatial uniformity of nc-Si:H solar cells. We fabricated and optimized a-Si:H/nc-Si:H/nc-Si:H triple-junction solar cells deposited on textured Ag/ZnO back reflectors on thin flexible stainless steel substrates using the optimized nc-Si:H component cells. Cells with aperture area ~400 cm 2 and 807 cm 2 were fabricated and encapsulated using our proprietary lightweight flexible encapsulants. We sent representative large-area samples to National Renewable Energy Laboratory (NREL) for confirmation of conversion efficiency. NREL has confirmed an initial aperture-area efficiency of 12.0% for cells with aperture area ~400 cm 2 . The highest initial efficiency for the encapsulated cells with aperture area ~807 cm 2 is ~11.9% as measured at United Solar. We light soaked small-area and large-area cells to obtain stable performance. Detailed results will be presented at the conference.
A polycrystalline-silicon (poly-Si) thin-film transistor (TFT) deposited at low temperature on Corning 7059 glass is reported. It has practical applications for low-cost thin-film display and imaging ...electronics manufacturing. All the process steps used to fabricate the poly-Si device take place at temperatures of 550 degrees C or less. The poly-Si films exhibit crystallite grain sizes on the order of 5000 AA, and the fabricated devices show field-effect mobilities of 10-20 cm/sup 2//V-s and threshold voltages around zero. A plasma process to form the source and drain contacts has also been developed.< >
We fabricated five different types of a-SiGe:H and nc-Si:H based multi-junction solar cell structures using modified very high frequency (MVHF) technology. After optimization, all five structures ...reached similar initial cell performance, i.e. ~12% small active-area (0.25 cm 2 ) efficiency and 10.6-10.8% large aperture-area (¿ 400 cm 2 ) efficiency after encapsulation. However, they showed quite different light soaking stability behavior, which can be attributed to the degradation of component cells. We conducted a comparative study between the MVHF deposited solar cells with those deposited by RF. Materials studies were also conducted to understand the mechanism responsible for better stability for the MVHF deposited a-SiGe:H solar cells. The best stable efficiency achieved for the large-area encapsulated cells is approaching 10% for both a-SiGe:H and nc-Si:H based multi-junction cells.
Composite restorations containing quartz fillers have shown persistent roughness after finishing which contributes to marginal discoloration and staining. Resin finish coatings have been used to ...attempt to overcome this problem. This study was designed to compare the durability of two resin coating materials used on two brands of composite restorative materials. Results showed that composites glazed with resin coating finishes at placement maintained their luster, color match, and surface smoothness significantly better after one year than composites that were not coated. After a year it was concluded that composites on which the resin coating is intact maintain their color match, luster, and smoothness significantly better than uncoated composite restorations.
The Disulfide Bond Connecting the Chains of Ricin Lappi, Douglas A.; Kapmeyer, Wolfgang; Beglau, Janice M. ...
Proceedings of the National Academy of Sciences - PNAS,
03/1978, Letnik:
75, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Studies on the disulfide bond connecting the two polypeptide chains of ricin are reported. Reduction of this bond in the native protein requires approximately 50-fold more mercaptoethanol than the ...reduction of the bond in the protein denatured by sodium dodecyl sulfate. An improved procedure for the formation of this disulfide bond from recombined chains is reported. A and B chains spontaneously and rapidly reassociate into a stable complex with a sedimentation velocity similar to that of native oxidized ricin before the disulfide bond reforms. The mixture of both chains also behaves on Bio-Gel P-100 like native oxidized ricin. However, the complex formed by the two chains, assayed before the disulfide bond can reform, and reduced ricin, carboxymethylated to prevent reoxidation, shows a significant decrease in toxicity to mice and a decrease in ability to inhibit protein synthesis in HeLa cells in culture.
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