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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

Performance Trade-Offs for MBG Using Different Bandgap Pairs

Present GAInP2/GAAs cell grown on Ge (or GaAs) substrates have demonstrates high efficiency, However, the individual bandgaps (1.85 eV, 1.42 eV respectively) are not the optimum match to convert the AM0 spectrum efficiently, although by reducing the thickness of the GaInP2 cell, good efficiencies have been achieved. Within the III-V alloys, modeling shows that several dual junction cells, comprising different bandgap pairs, could give higher efficiency. This paper outlines the modeling used, the bandgap pairs selected, and projections for the AM0 efficiency assuming that the effects of lattice mismatch associated with the bandgap can be reduced. We also present preliminary data on I-V performance for the selected top and bottom cells and for some full cascade cells. We have included some characterization results to check the bandgaps and lattice strain, to check how closely the fabricated cells conform to the model,

Iles, P. A.↗
NASA NTRS1976

Silicon materials task of the low cost solar array project, part 2

Purity requirements for solar cell grade silicon material was developed and defined by evaluating the effects of specific impurities and impurity levels on the performance of silicon solar cells. Also, data was generated forming the basis for cost-tradeoff analyses of silicon solar cell material. Growth, evaluation, solar cell fabrication and testing was completed for the baseline boron-doped Czochralski material. Measurements indicate Cn and Mn seriously degrade cell performance, while neither Ni nor Cu produce any serious reduction in cell efficiency.

Hopkins, R. H.↗
NASA NTRS1977

High efficiency thin-film GaAs solar cells

Several oxidation techniques are discussed which have been found to increase the open circuit (V sub oc) of metal-GaAs Schottky barrier solar cells, the oxide chemistry, attempts to measure surface state parameters, the evolving characteristics of the solar cell as background contamination (has been decreased, but not eliminated), results of focused Nd/YAG laser beam recrystallization of Ge films evaporated onto tungsten, and studies of AMOS solar cells fabricated on sliced polycrystalline GaAs wafers. Also discussed are projected materials availability and costs for GaAs thin-film solar cells.

Stirn, R. J.↗
NASA NTRS1998

Electro-Optical Effects in Thin Organic Films

Meta-nitroaniline (mNA) and 2-cyclo-octylamino-5-nitropyridine (COANP) single crystals were grown between two transparent fused quartz plates on which indium-tin-oxide layers were deposited. Both linear and quadratic electro-optic effects of the crystals were examined by an ac modulation method. The figures of merit for mNA and COANP are estimated to be 3.2(10-12 m/V and 4.2(10-12 m/V, respectively. It was found that the crystals were under good protection of the cells and the figure of merits of the crystals did not decrease with time. It is believed that the method adopted in the paper is applicable to electro-optic cell fabrication with other compounds if those crystals growth from melt is feasible. It is suggested that the electro-optic cells have potential fortune because of their durability and relative easy manipulation processes of crystal growth.

Leyderman, Alexander↗
NASA NTRS1981

Silicon-on ceramic process: Silicon sheet growth and device development for the large-area silicon sheet task of the low-cost solar array project

The technical feasibility of producing solar-cell-quality sheet silicon to meet the Department of Energy (DOE) 1986 overall price goal of $0.70/watt was investigated. With the silicon-on-ceramic (SOC) approach, a low-cost ceramic substrate is coated with large-grain polycrystalline silicon by unidirectional solidification of molten silicon. This effort was divided into several areas of investigation in order to most efficiently meet the goals of the program. These areas include: (1) dip-coating; (2) continuous coating designated SCIM-coating, and acronym for Silicon Coating by an Inverted Meniscus (SCIM); (3) material characterization; (4) cell fabrication and evaluation; and (5) theoretical analysis. Both coating approaches were successful in producing thin layers of large grain, solar-cell-quality silicon. The dip-coating approach was initially investigated and considerable effort was given to this technique. The SCIM technique was adopted because of its scale-up potential and its capability to produce more conventiently large areas of SOC.

Grung, B. L.↗
NASA NTRS1994

Investigation of the stability and 1.0 MeV proton radiation resistance of commercially produced hydrogenated amorphous silicon alloy solar cells

The radiation resistance of commercial solar cells fabricated from hydrogenated amorphous silicon alloys is reported. A number of different device structures were irradiated with 1.0 MeV protons. The cells were annealing at 200 C. The annealing time was dependent on proton fluence. Annealing devices for one hour restores cell parameters or fluences below 1(exp 14) cm(exp -2); fluences above 1(exp 14) cm(exp -2) require longer annealing times. A parametric fitting model was used to characterize current mechanisms observed in dark I-V measurements. The current mechanisms were explored with irradiation fluence, and voltage and light soaking times. The thermal generation current density and quality factor increased with proton fluence. Device simulation shows the degradation in cell characteristics may be explained by the reduction of the electric field in the intrinsic layer.

Lord, Kenneth R., II↗
NASA NTRS1994

Radiation Resistance Studies of Amorphous Silicon Alloy Photovoltaic Materials

The radiation resistance of commercial solar cells fabricated from hydrogenated amorphous silicon alloys was investigated. A number of different device structures were irradiated with 1.0 MeV protons. The cells were insensitive to proton fluences below 1E12 sq cm. The parameters of the irradiated cells were restored with annealing at 200 C. The annealing time was dependent on proton fluence. Annealing devices for one hour restores cell parameters for fluences below lE14 sq cm require longer annealing times. A parametric fitting model was used to characterize current mechanisms observed in dark I-V measurements. The current mechanisms were explored with irradiation fluence, and voltage and light soaking times. The thermal generation current density and quality factor increased with proton fluence. Device simulation shows the degradation in cell characteristics may be explained by the reduction of the electric field in the intrinsic layer.

Woodyard, James R.↗
NASA NTRS1994

Investigation of the Stability and 1.0 MeV Proton Radiation Resistance of Commercially Produced Hydrogenated Amorphous Silicon Alloy Solar Cells

The radiation resistance of commercial solar cells fabricated from hydrogenated amorphous silicon alloys is reported. A number of different device structures were irradiated with 1.0 MeV protons. The cells were insensitive to proton fluences below 1E12 sq cm. The parameters of the irradiated cells were restored with annealing at 200 C. The annealing time was dependent on proton fluence. Annealing devices for one hour restores cell parameters for fluences below 1E14 sq cm fluences above 1E14 sq cm require longer annealing times. A parametric fitting model was used to characterize current mechanisms observed In dark I-V measurements. The current mechanism were explored with irradiation fluence, and voltage and light soaking times. The thermal generation current density and quality factor increased with proton fluence. Device simulation shows the degradation in cell characteristics may be explained by the reduction of the electric field in the intrinsic layer.

Lord, Kenneth R., II↗
NASA NTRS1987

Characterization and modelling of open tube diffused n+p bulk InP solar cells

The authors describe the photovoltaic characteristics of an n+p junction solar cell fabricated on bulk InP by an open-tube-diffusion technique. Analysis of the forward characteristics shows that the forward current is dominated by recombination in the quasineutral regions, indicating that the fabrication technique produces a clean junction. Spectral response measurements are analyzed and more realistic boundary conditions are used to model the solar cell to determine important material and device parameters.

Bothra, S.↗
NASA NTRS1978

Strip cell test and evaluation program

The performance characteristics of alkaline fuel cells to be used for space power systems were tested. Endurance tests were conducted on the cells during energy conversion operations. A feature of the cells fabricated and tested was the capability to evaporate the product water formed during the energy conversion reaction directly to space vacuum. A fuel cell powerplant incorporating these cells does not require a condenser and a hydrogen recirculating pump water separator to remove the product water. This simplified the fuel cell powerplant system, reduced the systems weight, and reduced the systems parasite power.

Gitlow, B.↗
NASA NTRS1978

The effects of copper and titanium on silicon solar cells

Copper-doped N/P silicon solar cells fabricated from the Czochralski grown single-crystal wafers were found to have good electrical characteristics, but the titanium-doped N/P silicon solar cells has considerably lower conversion efficiency. However, in the copper/titanium-doped solar cells, copper seems to mitigate the unfavorable effects of titanium. To explain this behavior, microstructural tests were performed on silicon wafers and solar cells doped with copper, titanium and copper/titanium. Dark forward and reverse I-V measurements were performed on the solar cells to correlate the microstructural defects with the p-n junction properties. It was found that copper precipitates were formed in the copper-doped and copper/titanium-doped wafers and cells. There was a significant voltage drop in the dark reverse I-V measurements of the titanium solar cells. Also, there were some electronically active defects in the depletion region of some titanium-doped cells. Reasons that lead to the above results are given in detail.

Salama, A. M.↗
NASA NTRS1984

Characterization of physiochemical properties of polymeric and electrochemical materials for aerospace flight

Nickel-cadmium rechargeable batteries are a vital and reliable energy storage source for aerospace applications. As the demand for longer life and more reliable space batteries increases, the understanding and solving of cell aging factors and mechanisms become essential. Over the years, many cell designs and manufacturing process changes have been developed and implemented. Cells fabricated with various design features were life cycled in a simulated low-Earth orbit regime. Following the test program, a comprehensive electrochemical analysis of cell components was undertaken to study cell degradation mechanisms. Discharge voltage degradation or voltage plateau has been observed during orbit cycling, but, its cause and explanation have been the subject of much discussion. A Hg/HgO reference electrode was used to monitor the reference versus each electrode potential during the discharge of a cycled cell. The results indicate that the negative electrode was responsible for the voltage plateau. Cell analysis revealed large crystals of cadmium hydroxide on the surface of the negative electrode and throughout the separator.

Rock, M.↗
NASA NTRS1980

Radiation damage in lithium-counterdoped N/P silicon solar cells

The radiation resistance and low-temperature annealing properties of lithium-counterdoped n(+)-p silicon solar cells are investigated. Cells fabricated from float zone and Czochralski grown silicon were irradiated with 1 MeV electrons and their performance compared to that of 0.35 ohm-cm control cells. The float zone cells demonstrated superior radiation resistance compared to the control cells, while no improvement was noted for the Czochralski grown cells. Annealing kinetics were found to lie between first and second order for relatively short times, and the most likely annealing mechanism was found to be the diffusion of lithium to defects with the subsequent neutralization of defects by combination with lithium. Cells with zero lithium gradients exhibited the best radiation resistance.

Hermann, A. M.↗
NASA NTRS1984

Diffused junction p(+)-n solar cells in bulk GaAs. II - Device characterization and modelling

The photovoltaic characteristics of p(+)-n junction solar cells fabricated on bulk GaAs by an open tube diffusion technique are presented in detail. Quantum efficiency measurements were analyzed and compared to computer simulations of the cell structure in order to determine material parameters such as diffusion length, surface recombination velocity and junction depth. From the results obtained it is projected that proper optimization of the cell parameters can increase the efficiency of the cells to close to 20 percent.

Keeney, R.↗
NASA NTRS1977

Summary of the NASA space photovoltaic research and technology program

Low cost solar cells and arrays with high end-of-life efficiency are evaluated through two approaches: one, to obtain increased device efficiency at no increase in cost and two, to reduce the manufacturing costs of space solar cells and arrays. Technology efforts encompass high efficiency epitaxial cells, high efficiency wraparound contact solar cells, economical diffusion sources, automated cell fabrication and development of easily applied, durable cover glasses. The examination of ion-implanted profile tailored junctions and additional development of screen printed contact technology to cell development are also considered.

Brandhorst, H. W., Jr.↗
NASA NTRS1978

EFG solar modules

Six photovoltaic modules using solar cells fabricated from silicon ribbons were assembled and delivered to JPL. Each module was comprised of four separate submodules which were parallel connected. The submodules contained 45 EFG cells which were series interconnected by a shingle or overlapping design. The inherent rectangular shape of the cells allowed a high packing factor to be achieved. The average efficiency of the six modules, corrected to AM1 at 28 C was 8.7%, which indicates that the average encapsulated cell efficiency was 10.0%.

Source record↗
NASA NTRS1978

Effect of multiblade slurry saw induced damage on silicon solar cells

A correlation between the optimum etch loss and the depth of damage is established using wafers produced by the Multiblade Slurry (MBS) and the Internal Diameter (ID) saws. The observations are based on the measurement of the performance of solar cells fabricated on these wafers. Sample preparation and test results are described and the following conclusions are made: (1) the amount of silicon removal necessary for optimum solar cell performance coincides with the depth of saw-induced damage; (2) optimization of cell performance is not affected by the method of silicon removal; (3) sawing conditions should be optimized to minimize the extent of saw-induced damage; (4) the MBS saw is found to induce damage to a lesser extent; (5) since the extent of damage in MBS-sawn wafers is in the limit of etch loss required in texture etching, it is possible to achieve optimum improvement in cell performance by merely texture etching the surface of as-sawn wafers.

Daud, T.↗