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.
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.
Superconductivity at 155 K OVSHINSKY, S. R; YOUNG, R. T; ALLRED, D. D ...
Physical review letters,
06/1987, Letnik:
58, Številka:
24
Journal Article
Recenzirano
Transition to a superconducting zero-resistance state at 155 K is observed for the first time in bulk material. A new five-element compound has been synthesized with nominal composition Y1Ba2Cu3F2Oy. ...Fluorine plays a critical role in achieving this effect. X-ray diffraction and electron microprobe analysis indicate that the samples are multiphasic. Evidence is presented that the samples contain superconducting phases with onset temperatures considerably above 155 K. Magnetic measurements suggest a flux-trapping effect below 260 K, and diamagnetic deviations from Curie-Weiss behavior in the range T of between 250 and 100 K, inclusively, indicate a Meissner effect in a small superconducting volume fraction. (Author)
A top coating has been developed for a-Si:H/a-SiGe:H/a-SiGe:H triple-junction solar cells on polymer substrate for space and stratospheric applications. Several candidate coatings were screened for ...potential use in the space and stratospheric environments. A proprietary coating performed well; however, the coating exhibited darkening after UV exposure in high vacuum or inert atmosphere. The darkening was reversed with a postexposure treatment. An effective pre-treatment technique has been developed to prevent darkening in UV/vacuum, such as in high-orbit space applications. A method has been developed to interconnect lightweight thin film cells on polymer into strings. Strings have been tested for mechanical robustness and have been repeatedly rolled and unrolled with no degradation in cell performance.
Over the last several years, we have continuously increased the conversion efficiency of solar cells and modules. In this paper, we discuss new developments which led to a ~5% increase in conversion ...efficiency of cells and modules made using roll-to-roll deposition. The enhanced efficiency is attributed primarily to the replacement of the conventional Al/ZnO back reflector with a new Ag/ZnO structure. We optimized the deposition parameters to obtain the highest cell efficiency. We used large-area cells to fabricate flexible interconnected modules of dimensions 548.6 cm × 39.4 cm. The initial power output (P max ) of the modules was 180.2-183.3 W which is the highest obtained for roll-to-roll processing. We conducted light soak studies to determine stable module power output.
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.
Eukaryotic cells respond to DNA damage and S phase replication blocks by arresting cell‐cycle progression through the DNA structure checkpoint pathways. In Schizosaccharomyces pombe, the Chk1 kinase ...is essential for mitotic arrest and is phosphorylated after DNA damage. During S phase, the Cds1 kinase is activated in response to DNA damage and DNA replication blocks. The response of both Chk1 and Cds1 requires the six ‘checkpoint Rad’ proteins (Rad1, Rad3, Rad9, Rad17, Rad26 and Hus1). We demonstrate that DNA damage‐dependent phosphorylation of Chk1 is also cell‐cycle specific, occurring primarily in late S phase and G2, but not during M/G1 or early S phase. We have also isolated and characterized a temperature‐sensitive allele of rad3. Rad3 functions differently depending on which checkpoint pathway is activated. Following DNA damage, rad3 is required to initiate but not maintain the Chk1 response. When DNA replication is inhibited, rad3 is required for both initiation and maintenance of the Cds1 response. We have identified a strong genetic interaction between rad3 and cds1, and biochemical evidence shows a physical interaction is possible between Rad3 and Cds1, and between Rad3 and Chk1 in vitro. Together, our results highlight the cell‐cycle specificity of the DNA structure‐dependent checkpoint response and identify distinct roles for Rad3 in the different checkpoint responses.
PDF