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  • 1
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    The properties of polycrystalline silicon solar cells with controlled titanium additions (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: By coupling the results of electrical measurements, such as spectral response, lighted and dark I-V determinations, and deep-level-transient spectroscopy with optical and laser scan photomicroscopy, the effects of grain boundaries and impurities on silicon solar cells were evaluated. Titanium, which produces two deep levels in silicon, degrades cell performance by reducing bulk lifetime and thus cell short-circuit current. Electrically active grain boundaries induce carrier recombination in the bulk and depletion regions of the solar cell. Experimental data imply a small but measurable segregation of titanium into some grain boundaries of the polycrystalline silicon containing high Ti concentration. However, for the titanium-contaminated polycrystalline material used in this study, solar cell performance is dominated by the electrically active titanium concentration in the grains. Microstructural impacts on the devices are of secondary importance
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: IEEE Transactions on Electron Devices; ED-28; Jan. 198
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  • 2
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    Effect of impurities and processing on silicon solar cells. Volume 1: Characterization methods for impurities in silicon and impurity effects data base (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Two major topics are treated: methods to measure and evaluate impurity effects in silicon and comprehensive tabulations of data derived during the study. Discussions of deep level spectroscopy, detailed dark I-V measurements, recombination lifetime determination, scanned laser photo-response, conventional solar cell I-V techniques, and descriptions of silicon chemical analysis are presented and discussed. The tabulated data include lists of impurity segregation coefficients, ingot impurity analyses and estimated concentrations, typical deep level impurity spectra, photoconductive and open circuit decay lifetimes for individual metal-doped ingots, and a complete tabulation of the cell I-V characteristics of nearly 200 ingots.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA-CR-162627 , DOE/JPL-954331-80/9 , JPL-9950-299 , QR-17
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  • 3
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    Low cost silicon solar array project large area silicon sheet task: Silicon web process development (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Growth configurations were developed which produced crystals having low residual stress levels. The properties of a 106 mm diameter round crucible were evaluated and it was found that this design had greatly enhanced temperature fluctuations arising from convection in the melt. Thermal modeling efforts were directed to developing finite element models of the 106 mm round crucible and an elongated susceptor/crucible configuration. Also, the thermal model for the heat loss modes from the dendritic web was examined for guidance in reducing the thermal stress in the web. An economic analysis was prepared to evaluate the silicon web process in relation to price goals.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA-CR-156984 , ERDA/JPL-954654-77/3 , QR-3
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  • 4
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    Silicon materials task of the Low Cost Solar Array Project: Effect of impurities and processing on silicon solar cells (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The effects of impurities and processing on the characteristics of silicon and terrestrial silicon solar cells were defined in order to develop cost benefit relationships for the use of cheaper, less pure solar grades of silicon. The amount of concentrations of commonly encountered impurities that can be tolerated in typical p or n base solar cells was established, then a preliminary analytical model from which the cell performance could be projected depending on the kinds and amounts of contaminants in the silicon base material was developed. The impurity data base was expanded to include construction materials, and the impurity performace model was refined to account for additional effects such as base resistivity, grain boundary interactions, thermal processing, synergic behavior, and nonuniform impurity distributions. A preliminary assessment of long term (aging) behavior of impurities was also undertaken.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA-CR-169051 , DOE/JPL-954331-82/13 , JPL-9950-655 , NAS 1.26:169051
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  • 5
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    Phase 2 of the array automated assembly task for the low cost solar array project (1979)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The process sequence for the fabrication of dendritic web silicon into solar panels was modified to include aluminum back surface field formation. Plasma etching was found to be a feasible technique for pre-diffusion cleaning of the web. Several contacting systems were studied. The total plated Pd-Ni system was not compatible with the process sequence; however, the evaporated TiPd-electroplated Cu system was shown stable under life testing. Ultrasonic bonding parameters were determined for various interconnect and contact metals but the yield of the process was not sufficiently high to use for module fabrication at this time. Over 400 solar cells were fabricated according to the modified sequence. No sub-process incompatibility was seen. These cells were used to fabricate four demonstration modules. A cost analysis of the modified process sequence resulted in a selling price of $0.75/peak watt.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA-CR-162628 , DOE/JPL-954873-79/08
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  • 6
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    Silicon web process development (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Thirty-five (35) furnace runs were carried out during this quarter, of which 25 produced a total of 120 web crystals. The two main thermal models for the dendritic growth process were completed and are being used to assist the design of the thermal geometry of the web growth apparatus. The first model, a finite element representation of the susceptor and crucible, was refined to give greater precision and resolution in the critical central region of the melt. The second thermal model, which describes the dissipation of the latent heat to generate thickness-velocity data, was completed. Dendritic web samples were fabricated into solar cells using a standard configuration and a standard process for a N(+) -P-P(+) configuration. The detailed engineering design was completed for a new dendritic web growth facility of greater width capability than previous facilities.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA-CR-157098 , ERDA/JPL-954654-77/2 , QR-2
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  • 7
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    Silicon materials task of the low cost solar array project, phase 2 (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The object of phase 2 of this program is to investigate and define the effects of various processes, contaminants and process-contaminant interactions in the performance of terrestrial solar cells. The major effort this quarter was in the areas of crystal growth and thermal processing, comparison of impurity effects in low and high resistivity silicon, modeling the behavior of p-type ingots containing Mo, and C and, quantitative analysis of bulk lifetime and junction degradation effects in contaminated solar cells. The performance of solar cells fabricated on silicon web crystals grown from melts containing about 10 to the 18th power/cu cm of Cr, Mn, Fe, Ni, Ti, and V, respectively were measured. Deep level spectroscopy of metal-contaminated ingots was employed to determine the level and density of recombination centers due to Ti, V, Ni, and Cr.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA-CR-157082 , DOE/JPL-954431-78/1 , QR-9
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  • 8
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    Array Automated Assembly Task for the Low Cost Solar Array Project, Phase 2 (1979)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Using silk screened evaporated and sputtered Al as the metal source, the formation of Al back surface fields was studied. The most satisfactory results were those obtained with the sputtered A1 and in which open circuit voltages (V sub oc) of 0.585 v (12 ohm cm FZ silicon) were achieved. The ultrasonic interconnect process is discussed. The process is shown to be satisfactory, but increased pull-strength may be obtained if some form of sintering is carried out on the metallized contacts. Plasma etching is shown to be feasible as a replacement for wet chemical cleaning prior to diffusion. Initial results on cells prepared by using electroless Pd/Ni plus either electroplated Ag or Cu show slightly poor performance than cells with the baseline evaporated Ti/Pd/Ag system. A mask designed for the 1.6 x 7.0 cm and 2.0 x 7.0 cm cells is described. This mask has a lower area coverage and total lower resistive loss than the previous mask design. It is also shown that the cell width should not exceed 2.0 - 3.0 cm for optimum efficiency.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA-CR-158727 , AR-6 , QR-6
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  • 9
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    Characterization of the effects of metallic impurities on silicon solar cell performance (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The effects of controlled concentrations of secondary impurities (Al, C, Ca, Cr, Cu, Fe, Mg, Mn, Mo, Ta, Ti, V, Zn, and Zr), incorporated alone or in combinations into Czochralski and float zone crystals, on the performance of silicon solar cells were investigated. Impurity concentrations ranged from 10 to the 11th to 10 to the 17th/cu cm. Solar cells were fabricated by a conventional diffusion process and characterized by computer reduction of current-voltage data. The data suggest that performance loss primarily results from reduction of the base diffusion length. On the basis of this assumption, a first order analytic model which predicts cell performance as a function of impurity concentrations is developed. Calculated performance parameters are in good agreement with observation, except for some impurities, such as Fe, Cu and Ni, which degrade cells via recombination and defects in the junction space-charge region. N-base devices are less affected by impurities, although degradation mechanisms appear to be the same as in p-devices. There seems to be very limited interaction between impurities in multiply-doped cells.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: Photovoltaic Specialists Conference; Jun 05, 1978 - Jun 08, 1978; Washington, DC
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  • 10
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    Solar cell contacts (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Two experimental contact systems were examined and compared to a baseline contact system consisting of evaporated layers of titanium, palladium, and silver and an electroplated layer of copper. The first experimental contact system consisted of evaporated layers of titanium, nickel, and copper and an electroplated layer of copper. This system performed as well as the baseline system in all respects, including its response to temperature stress tests, to a humidity test, and to an accelerated aging test. In addition, the cost of this system is estimated to be only 43 percent of the cost of the baseline system at a production level of 25 MW/year. The second experimental contact system consisted of evaporated layers of nickel and copper and an electroplated layer of copper. Cells with this system show serious degradation in a temperature stress test at 350 C for 30 minutes. Auger electron spectroscopy was used to show that the evaporated nickel layer is not an adequate barrier to copper diffusion even at temperatures as low as 250 C. This fact brings into question the long-term reliability of this contact system.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Format: text
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