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  • 1
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    The sawtooth cover slide (1977)
    In:  CASI
    Details
    Publication Date: 2006-05-22
    Description: A novel cover slide is reported which increases solar cell output by reducing the reflection of light from the cover slide surface and by redirecting incident light so that none falls on the collection grids of the cell. The new cover slide is fabricated with a sawtooth surface having a periodicity equal to that of the solar cell grids. This configuration refracts the light so that it is directed onto the semiconductor surface between the grid lines. Conventional grid patterns obstruct 7-10 percent of the light incident on the cell; at least half of this loss has been recovered by using the sawtooth cover slide. In addition, surface reflection from the conventional coated cover slide is suppressed by presenting a second surface to any light reflected at the first plane of contact. This double reflection results in a greater reduction of the reflection loss from the cover slide than does an antireflection coating on a flat surface.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA. Lewis Res. Center Solar Cell High Efficiency and Radiation Damage; p 95-98
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Ultraviolet damage in solar cell assemblies with various UV filters (1977)
    In:  CASI
    Details
    Publication Date: 2006-05-24
    Description: Ultraviolet damage to the new violet and non-reflective type solar cell assemblies, was studied, and potential advantages of using coverslides with no filters or filters with cut-off wavelengths below 0.35 micron were determined. The experiments consisted of three types of tests on fused silica coverslides with 0.35- and 0.30-micron cut-off filters and no cut-off filters, as well as on ceria-doped microsheet coverslides. Ultraviolet irradiation for over 1500 hours at one sun conditions (AMO) was carried out under vacuum of about 1 million torr. Nearly identical results for non-reflective type cells with 0.35-micro cut-off filters or ceria-doped coverslides were obtained. The 0.30-um filtered cell shows greater than average degradation. The unfiltered cell shows an abrupt drop in the first 20 UVSH and very little subsequent degradation.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA. Lewis Res. Center Solar Cell High Efficiency and Radiation Damage; p 227-229
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Ionization induced damage in crystalline silicon (1977)
    In:  CASI
    Details
    Publication Date: 2006-05-24
    Description: Close examination of the interaction of the energetic knock-on atoms with the local lattice environment reveals a damage mechanism which does satisfy the experimental data on proton irradiation of silicon. A proton-atom interaction with high energy transfer is considered where the proton path is delineated by a trail of ionization, and the silicon ion path is characterized by much heavier ionization terminating in a dense displacement cluster. At collision, many of the silicon electrons are stripped off, and the resulting energetic ion subsequently loses energy rapidly by Coulomb interaction with bound electrons. The rate of energy loss depends on the charge state and velocity of the knock-on ion. For ion energies in excess of 1 MeV, the intensity of ionization is sufficient to permit lattice atoms, stripped of their binding electrons, to reorient randomly before having an opportunity to recombine with electrons and re-establish the lattice. The path of a knock-on ion thus becomes a thin cylinder of amorphous material within the crystal. Amorphous silicon has a Fermi level closer to mid-band than does single crystal silicon, and a strong field therefore, results around this damaged region. The field produces a large depletion region, representing a very large capture cross section for minority carriers.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA. Lewis Res. Center Solar Cell High Efficiency and Radiation Damage; p 221-223
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    NASA TECHNICAL REPORTS
  • 4
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    Investigations of radiation-induced and carrier-enhanced conductivity (1985)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A steady-state carrier computer code, PECK (Parker Enhanced Carrier Kinetics), that predicts the radiation-induced conductivity (RIC) produced in a dielectric by an electron beam was developed. The model, which assumes instantly-trapped holes, was then applied to experimental measurements on thin Kapton samples penetrated by an electron beam. Measurements at high bias were matched in the model by an appropriate choice for the trap-modulated electron mobility. A fractional split between front and rear currents measured at zone bias is explained on the basis of beam-scattering. The effects of carrier-enhanced conductivity (CEC) on data obtained for thick, free-surface Kapton samples is described by using an analytical model that incorporates field injection of carriers from the RIC region. The computer code, LWPCHARGE, modified for carrier transport, is also used to predict partial penetration effects associated with CEC in the unirradiated region. Experimental currents and surface voltages, when incorporated in the appropriate models, provide a value for the trap modulated mobility that is in essential agreement with the RIC results.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: NASA. Lewis Research Center Spacecraft Environ. Interactions Technol., 1983; p 571-590
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    Silicon Research and Technology Workshop report (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The materials, structures, processing, modeling and measurements of high efficiency silicon solar cells were surveyed. In the materials area, highlights included: (1) the possibility of improving cell voltages by reducing minority carrier mobilities in critical regions of the solar cells; (2) the need for and possibility of lowering the surface recombination velocity for improvement of open circuit voltage in shallow junction cells; (3) the present need for improved lifetime in high resistivity cells; and (4) the potential for new materials such as polycrystalline or dendritic web material to perform well at end of life in a radiation environment. In the area of structures, distinction was made between those for terrestrial use and those that would survive radiation environments. Areas such as epitaxial growth and laser or elctron beam annealing (and diffusion) were proposed as having certain advantages over more conventional techniques.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA. Lewis Research Center Space Photovoltaic Res. and Technol.; p 71-72
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  • 6
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    Limitations on solar cell open-circuit voltage and efficiency (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Techniques used to determine the open-circuit voltage of solar cells are analyzed. It is noted that the computational procedures for determining the output characteristics of a solar cell depend on a thorough understanding of the behavior of individual components. However, amorphous materials and combination solar cells exhibit increasingly complex behaviors and theoretical analyses therefore are continually more dependent on experimental data for verification. Formulations are defined for the base region and for diffusion length measurement. Experimental results are cited to show that, for low resistivity, planar surface cells, the dark current from the emitter is the dominant factor limiting increases in the Voc, which can be enhanced by improving the efficiency of the doping levels and profile to minimize the effects of bandgap narrowing, junction recombination current, and diffusion length of the emitter region.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: COMSAT Technical Review; 13; Spring 1
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    NASA TECHNICAL REPORTS
  • 7
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    Thin n-i-p radiation-resistant solar cell feasibility study (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Silicon solar cells were fabricated to verify the predictions that: (1) thin n(+)pp(+) cells can provide high values of open circuit voltage even when high resistivity base material ( 1000 omega-cm) is used; (2) cells with good p(+) back contacts will display an increase in open circuit voltage with decreasing cell thickness; and (3) high quality, thin, high resistivity, solar cells can be made using processing compatible with conventional practice. Analysis of I-V and spectral response measurements of these cells confirmed theoretical predictions and thereby pointed to voltages beyond the near 600 mV obtained in this study.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA-CR-159871
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    NASA TECHNICAL REPORTS
  • 8
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    Developments toward an 18% efficient silicon solar cell (1983)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Limitations to increased open-circuit voltage were identified and experimentally verified for 0.1 ohm-cm solar cells with heavily doped emitters. After major reduction in the dark current contribution from the metal-silicon interface of the grid contacts, the surface recombination velocity of the oxide-silicon interface of shallow junction solar cells is the limiting factor. In deep junction solar cells, where the junction field does not aid surface collection, the emitter bulk is the limiting factor. Singly-diffused, shallow junction cells have been fabricated with open circuit voltages in excess of 645 mV. Double-diffusion shallow and deep junctions cells have displayed voltages above 650 mV. MIS solar cells formed on 0.1 ohm-cm substrates have exibited the lowest dark currents produced in the course of the contract work.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA-CR-168141 , NAS 1.26:168141
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  • 9
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    High- and low-resistivity silicon solar cells (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Attention is given to recent work at COMSAT Laboratories on improving silicon solar cell efficiencies and open-circuit voltages for both high (more than 1000 ohm-cm) and low (less than 1 ohm-cm) resistivities. It is noted that open-circuit voltages above 650 mV have been obtained for 0.1 ohm-cm cells and that air mass zero efficiencies of 12.5% have been measured from 4-mil 1,250 ohm-cm.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: In: Intersociety Energy Conversion Engineering Conference; Aug 09, 1981 - Aug 14, 1981; Atlanta, GA
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  • 10
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    Thin n-i-p silicon solar cell (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A space solar cell concept which combines high cell output with low diffusion length damage coefficients is presented for the purpose of reducing solar cell susceptibility to degradation from the radiation environment. High resistivity n-i-p silicon solar cells ranging from upward of 83 micron-cm were exposed to AM0 ultraviolet illumination. It is shown that high resistivity cells act as extrinsic devices under dark conditions and as intrinsic devices under AM0 illumination. Resistive losses in thin n-i-p cells are found to be comparable to those in low resistivity cells. Present voltage limitations appear to be due to generation and recombination in the diffused regions.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: Photovoltaic Specialists Conference; Jan 07, 1980 - Jan 10, 1980; San Diego, CA
    Format: text
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    NASA TECHNICAL REPORTS
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