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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Induced junction solar cell and method of fabrication

An induced junction solar cell is fabricated on a p-type silicon substrate by first diffusing a grid of criss-crossed current collecting n+ stripes and thermally growing a thin SiO2 film, and then, using silicon-rich chemical vapor deposition (CVD), producing a layer of SiO2 having inherent defects, such as silicon interstices, which function as deep traps for spontaneous positive charges. Ion implantation increases the stable positive charge distribution for a greater inversion layer in the p-type silicon near the surface. After etching through the oxide to parallel collecting stripes, a pattern of metal is produced consisting of a set of contact stripes over the exposed collecting stripes and a diamond shaped pattern which functions as a current collection bus. Then the reverse side is metallized.

Maserjian, J.↗
NASA NTRS1978

Silicon Sheet Growth Development for the Large Area Sheet Task of the Low Cost Solar Array Project. Heat Exchanger Method - Ingot Casting Fixed Abrasive Method - Multi-Wire Slicing

Solar cells fabricated from HEM cast silicon yielded up to 15% conversion efficiencies. This was achieved in spite of using unpurified graphite parts in the HEM furnace and without optimization of material or cell processing parameters. Molybdenum retainers prevented SiC formation and reduced carbon content by 50%. The oxygen content of vacuum cast HEM silicon is lower than typical Czochralski grown silicon. Impregnation of 45 micrometers diamonds into 7.5 micrometers copper sheath showed distortion of the copper layer. However, 12.5 micrometers and 15 micrometers copper sheath can be impregnated with 45 micrometers diamonds to a high concentration. Electroless nickel plating of wires impregnated only in the cutting edge showed nickel concentration around the diamonds. This has the possibility of reducing kerf. The high speed slicer fabricated can achieve higher speed and longer stroke with vibration isolation.

Schmid, F.↗
NASA NTRS1986

Laser-assisted solar cell metallization processing

The status of the laser-assisted solar cell metallization processing is described. Metallo-organic silver films were spun-on by argon ion laser beam pyrolysis. The metallo-organic decomposition (MOD) film was spun-on an evaporated Ti/Pd film to produce tood adhesion. In a maskless process, the argon ion laser writes the contact pattern. The film is then built up to obtain the required conductivity using conventional silverplating process. The Ti/Pd film in the field is chemically etched using the plated silver film as the mask. The width of the contact pattern is determined by the power of the laser. Widths as thin as 20 microns were obtained using 0.66 W of laser power. Cells fabricated with the 50 micron line widths of 4 ohm-cm floating zone (Fz) silicon-produced efficiencies of 16.6% (no passivation) which were equivalent to the best cells using conventional metallization/lithography and no passivation.

Meier, D. L.↗
NASA NTRS2015

High-Volume Production of Lightweight Multijunction Solar Cells

MicroLink Devices, Inc., has transitioned its 6-inch epitaxial lift-off (ELO) solar cell fabrication process into a manufacturing platform capable of sustaining large-volume production. This Phase II project improves the ELO process by reducing cycle time and increasing the yield of large-area devices. In addition, all critical device fabrication processes have transitioned to 6-inch production tool sets designed for volume production. An emphasis on automated cassette-to-cassette and batch processes minimizes operator dependence and cell performance variability. MicroLink Devices established a pilot production line capable of at least 1,500 6-inch wafers per month at greater than 80 percent yield. The company also increased the yield and manufacturability of the 6-inch reclaim process, which is crucial to reducing the cost of the cells.

Youtsey, Christopher↗
NASA NTRS1973

The multiple junction edge illuminated solar cell

The multiple junction edge illuminated solar cell was devised for high voltage low current applications. Devices to be flight tested in early 1974 with 96 series connected PNN+ junctions in a 2 cm X 2.3 cm size deliver 36 volts at 1 milliampere. Test data of M-J cells fabricated with resistivities of 10, 50, 100, 200, 450, and 1000 ohm cm silicon are presented and problem areas are discussed. An additional potential application of the M-J cell lies in ultilization of its high intensity performance that has been demonstrated at levels in excess of 100 AMO suns.

Sater, B. I.↗
NASA NTRS1981

Silicon solar cell process development, fabrication, and analysis

Work has progressed in fabrication and characterization of solar cells from ubiquitous crystallization process (UCP) wafers and LASS ribbons. Gettering tests applied to UCP wafers made little change on their performance compared with corresponding baseline data. Advanced processes such as shallow junction (SJ), back surface field (BSF), and multilayer antireflection (MLAR) were also applied. While BSF by Al paste had shunting problems, cells with SJ and BSF by evaporated Al, and MLAR did achieve 14.1% AMI on UCP silicon. The study of LASS material was very preliminary. Only a few cells with SJ, BSR, (no BSF) and MLAR were completed due to mechanical yield problems after lapping the material. Average efficiency was 10.7% AMI with 13.4% AMI for CZ controls. Relatively high minority carrier diffusion lengths were obtained. The lower than expected Jsc could be partially explained by low active area due to irregular sizes.

Yoo, H. I.↗
NASA NTRS1981

Development and fabrication of a solar cell junction processing system

A solar cell junction processing system was developed and fabricated. A pulsed electron beam for the four inch wafers is being assembled and tested, wafers were successfully pulsed, and solar cells fabricated. Assembly of the transport locks is completed. The transport was operated successfully but not with sufficient reproducibility. An experiment test facility to examine potential scaleup problems associated with the proposed ion implanter design was constructed and operated. Cells were implanted and found to have efficiency identical to the normal Spire implant process.

Bunker, S.↗
NASA NTRS1974

The multiple junction edge illuminated solar cell

The multiple junction edge illuminated solar cell (M-J Cell) was devised for high voltage, low current applications. Devices to be flight-tested in early 1974 with 96 series-connected PNN+ junctions in a 2 cm x 2.3 cm size deliver 36 volts at 1 milliampere. Test data of M-J Cells fabricated with resistivities of 10, 50, 100, 200, 450, and 1000 ohm-cm silicon are presented and problem areas are discussed. An additional potential application of the M-J Cell lies in utilization of its high-intensity performance that has been demonstrated at levels in excess of 100 AMO suns.

Sater, B. L.↗
NASA NTRS1982

Non-mass-analyzed ion implantation from a solid phosphorus source

A phosphorus ion beam, extracted from a Freeman ion source charged with elemental phosphorus, has been investigated for use in solar cell fabrication. Mass spectroscopy of the beam indicates the absence of both minority-carrier lifetime degrading impurities and hydrogen. The ion beam, without mass analysis, was used for ion implantation of solar cells, and performance for all cells was found to be equivalent to mass-analyzed controls.

Spitzer, M. B.↗
NASA NTRS1985

Hot-Dipped Metal Films as Epitaxial Substrates

Multistep process forms semiconductor devices on macrocrystalline films of cadmium or zinc. Solar-cell fabrication processes use hot-dipped macrocrystalline films on low-cost sheet-metal base as substrates for epitaxy. Epitaxial layers formed by variety of methods of alternative sequence paths. Solar cells made economically by forming desired surface substance directly on metal film by chemical reactions.

Shlichta, P. J.↗
NASA NTRS1985

Heat treatment of bulk gallium arsenide using a phosphosilicate glass cap

n-type bulk GaAs crystals, capped with chemically vapor-deposited phosphosilicate glass, were heat treated at temperatures in the range of 600 to 950 C. Measurements on Schottky diodes and solar cells fabricated on the heat-treated material, after removal of a damaged surface layer, show an increase in free-carrier concentration, in minority-carrier-diffusion length, and in solar-cell short-circuit current. The observed changes are attributed to a removal of lifetime-reducing acceptorlike impurities, defects, or their complexes.

Mathur, G.↗
NASA NTRS1984

High-efficiency silicon solar cells

Silicon solar cells are described which operate at energy conversion efficiencies independently measured at 18.7 percent under standard terrestrial test conditions (AM1.5, 100 mW/sq cm, 28 C). These are apparently the most efficient silicon cells fabricated to date. The high-efficiency results from a combination of high open-circuit voltage due to the careful attention paid to the passivation of the top surface of the cell, high fill factor due to the high open-circuit voltage and low parasitic resistance losses, and high short-circuit current density due to the use of shallow diffusions, a low grid coverage, and an optimized double layer antireflection coating.

Green, M. A.↗
NASA NTRS1991

Advances in Li-TiS2 cell technology

JPL is involved in a NASA sponsored program to develop ambient temperature secondary cells for future space missions. After several years of research on various cathode materials, Titanium Disulfide (TiS2) was selected in view of its intrinsic reversibility and high faradaic utilization. In the last two years, the efforts were focused on improving the cycle life of the system and developing 1 Ah cells. Several approaches including the use of mixed solvent electrolytes, the operation of cells at low temperature, and the cycling of cells under different voltage limits, were initially examined to improve the cycle life performance of the Li-TiS2 system. Spiral wound 1 Ah cells fabricated incorporating the improvements from the above studies have delivered more than 600 cycles at 50% DOD. Work is in progress to identify alternate anode materials that can improve the cycle life of the cells to 1000 cycles at 50% DOD. This paper summarizes the advances made in the Li-TiS technology at JPL since 1989.

S Surampudi↗
NASA NTRS1994

SP-100 Thermoelectric Cell Testing at JPL

Three prototypic SP-100 thermoelectric cells, fabricated by Martin Marietta Astro Space in Valley Forge, Pennsylvania, were tested in vacuum at prototypic temperatures at JPL. Their thermal and electrical performance were characterized with 200, 300, 400, and 500 degree Celsius temperature gradients across the cell. The latter was representative of prototypic operating conditions with a 1050 degree Celsius hot side temperature and a 550 degree Celsius cold side temperature. The initial thermal and electrical performance of all three cells closely matched predictions.

thermoelectric↗
NASA NTRS1982

Photovoltaic characteristics of diffused P/+N bulk GaAs solar cells

The photovoltaic characteristics of P(+)N junction solar cells fabricated on bulk GaAs by an open tube diffusion technique are described in this paper.Spectral response measurements were analyzed in detail and compared to a computer simulation in order to determine important material parameters. It is projected that proper optimization of the cell parameters can increase the efficiency of the cells from 12.2 percent to close to 20 percent.

Borrego, J. M.↗
NASA NTRS1975

Damage coefficients in low resistivity silicon

Electron and proton damage coefficients are determined for low resistivity silicon based on minority-carrier lifetime measurements on bulk material and diffusion length measurements on solar cells. Irradiations were performed on bulk samples and cells fabricated from four types of boron-doped 0.1 ohm-cm silicon ingots, including the four possible combinations of high and low oxygen content and high and low dislocation density. Measurements were also made on higher resistivity boron-doped bulk samples and solar cells. Major observations and conclusions from the investigation are discussed.

Srour, J. R.↗
NASA NTRS1985

New high-efficiency silicon solar cells

A design for silicon solar cells was investigated as an approach to increasing the cell open-circuit voltage and efficiency for flat-plate terrestrial photovoltaic applications. This deviates from past designs, where either the entire front surface of the cell is covered by a planar junction or the surface is textured before junction formation, which results in an even greater (up to 70%) junction area. The heavily doped front region and the junction space charge region are potential areas of high recombination for generated and injected minority carriers. The design presented reduces junction area by spreading equidiameter dot junctions across the surface of the cell, spaced about a diffusion length or less from each other. Various dot diameters and spacings allowed variations in total junction area. A simplified analysis was done to obtain a first-order design optimization. Efficiencies of up to 19% can be obtained. Cell fabrication involved extra masking steps for selective junction diffusion, and made surface passivation a key element in obtaining good collection. It also involved photolithography, with line widths down to microns. A method is demonstrated for achieving potentially high open-circuit voltages and solar-cell efficiencies.

Daud, T.↗