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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 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Characterization of the effects of metallic impurities on silicon solar cell performance

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.

Davis, J. R.↗
NASA NTRS1986

Thermoelectric converter for SP-100 space reactor power system

Conductively coupling the thermoelectric converter to the heat source and the radiator maximizes the utilization of the reactor and radiator temperatures and thereby minimizes the power system weight. This paper presents the design for the converter and the individual thermoelectric cells that are the building block modules for the converter. It also summarizes progress on the fabrication of initial cells and the results obtained from the preparation of a manufacturing plan. The design developed for the SP-100 system utilizes thermally conductive compliant pads that can absorb the displacement and distortion caused by the combinations of temperatures and thermal expansion coefficients. The converter and cell designs provided a 100 kWe system which met the system requirements. Initial cells were fabricated and tested.

Terrill, W. R.↗
NASA NTRS1996

Strategies for "minimal growth maintenance" of cell cultures: a perspective on management for extended duration experimentation in the microgravity environment of a Space station

How cells manage without gravity and how they change in the absence of gravity are basic questions that only prolonged life on a Space station will enable us to answer. We know from investigations carried out on various kinds of Space vehicles and stations that profound physiological effects can and often to occur. We need to know more of the basic biochemistry and biophysics both of cells and of whole organisms in conditions of reduced gravity. The unique environment of Space affords plant scientists an unusual opportunity to carry out experiments in microgravity, but some major challenges must be faced before this can be done with confidence. Various laboratory activities that are routine on Earth take on special significance and offer problems that need imaginative resolution before even a relatively simple experiment can be reliably executed on a Space station. For example, scientists might wish to investigate whether adaptive or other changes that have occurred in the environment of Space are retained after return to Earth-normal conditions. Investigators seeking to carry out experiments in the low-gravity environment of Space using cultured cells will need to solve the problem of keeping cultures quiescent for protracted periods before an experiment is initiated, after periodic sampling is carried out, and after the experiment is completed. This review gives an evaluation of a range of strategies that can enable one to manipulate cell physiology and curtail growth dramatically toward this end. These strategies include cryopreservation, chilling, reduced oxygen, gel entrapment strategies, osmotic adjustment, nutrient starvation, pH manipulation, and the use of mitotic inhibitors and growth-retarding chemicals. Cells not only need to be rendered quiescent for protracted periods but they also must be recoverable and further grown if it is so desired. Elaboration of satisfactory procedures for management of cells and tissues at "near zero or minimal growth" will have great value and practical consequences for experimentation on Earth as well as in Space. All of the parameters and conditions and procedural details needed to meet all the specific objectives will be the basis of the design and fabrication of cell culture units for use in the Space environment. It is expected that this will be an evolutionary process.

STS-61A Shuttle Project↗
DOE OSTI2023

Tuning the Intermolecular Electrostatic Interaction toward High-Efficiency and Low-Cost Organic Solar Cells

Organic solar cells (OSCs) have achieved much progress with rapidly increasing power conversion efficiencies (PCEs). It should be noted that the top-performance OSCs are generally consisted of active materials with complex chemical structures, resulting in high costs. Here, combining the material design and morphology control, high-efficiency OSCs are fabricated by a low-cost donor: acceptor blend. A completely non-fused electron acceptor named Tz is designed and synthesized via introducing thiazole units on both sides of a bithiophene core, which shows an outstanding PCE of 13.3% with a typical polythiophene donor. More importantly, optimization guidelines are presented to get excellent morphology for low-cost donor:acceptor systems. Three polythiophenes are selected, poly(3-hexylthiophene) and its two derivatives with electron-withdrawing substitutions (PDCBT and PDCBT-2F), as donors to fabricate the cell devices. The computational and experimental data reveal that decreasing the electrostatic interaction between polythiophene and Tz is the key to getting a suppressed miscibility and thus a high phase purity. Finally, this study provides insight into the molecular design and donor:acceptor matching requirements for high-efficiency and low-cost OSCs.

14 SOLAR ENERGY↗
NASA NTRS1982

Planar multijunction high voltage solar cell chip

A new innovative planar multijunction solar cell chip for concentrated sunlight applications is proposed. The chip consists of many voltage-generating regions, called unit cells, which are connected in series within a single silicon wafer, thereby providing a high open-circuit voltage at multiple sun illumination levels. The unit cells are fabricated on 75 micron thick p-type single crystal silicon substrate. Each chip consists of 1.42 x 9.63 mm n(+)/p collecting junctions on the back of the wafer, while the illuminated front surface area is divided into 0.3 micron deep n(+) regions. The fabrication sequence includes standard degreasing and cleaning procedures, double-sided alignment photomasking, introduction of boron and phosphorus impurities, and photolithography. The open circuit voltage of the chip increased rapidly with illumination up to about 4 AM1 suns, and then began to saturate at the sum of the individual unit cell voltages of 3.5 above 4 AM1 suns. A short circuit density per unit cell of 300 mA/sq cm at 20 AM1 suns was observed.

Valco, G. J.↗
NASA NTRS1988

A V-grooved GaAs solar cell

V-grooved GaAs solar cells promise the benefits of improved optical coupling, higher short-circuit current, and increased tolerance to particle radiation compared to planar cells. A GaAs homojunction cell was fabricated by etching a V-groove pattern into an n epilayer (2.1 x 10 to the 17th power per cu cm) grown by metalorganic chemical vapor deposition (MOCVD) on an n+ substrate (2.8 x 10 to the 18th power per cu cm) and then depositing and MOCVD p epilayer (4.2 x 10 to the 18th power per cu cm). Reflectivity measurements on cells with and without an antireflective coating confirm the expected decrease in reluctance of the microgrooved cell compared to the planar structure. The short circuit current of the V-grooved solar cell was 13 percent higher than that of the planar control.

Bailey, S. G.↗
NASA NTRS1979

The Establishment of a Production-ready Manufacturing Process Utilizing Thin Silicon Substrates for Solar Cells

During the months of February and March, work towards the goals of the contract were started as scheduled. The first shipment of thin substrates were received and wafer processing was initiated. The objective of the contract is to investigate, develop and characterize the methods for establishing a production-ready manufacturing process which utilizes thin silicon substrates for solar cells. The thin substrates to be manufactured are three inches diameter, p-type Czochralski wafers of approximately 1 Omega cm resistivity. The wafers are prepared by sawing directly to thickness of 8 mils and 5 mils. To ensure removal of residual saw damage, most substrates are chemically etched to final thicknesses of 7 mils and 4 mils. The thin substrates are used to fabricate solar cells by standard processing techniques.

Pryor, R. A.↗
NASA NTRS1988

A V-grooved GaAs solar cell

V-grooved GaAs solar cells promise the benefits of improved optical coupling, higher short-circuit current, and incrased tolerance to particle radiation compared to planar cells. A GaAs homojunction cell was fabricated by etching a V-groove pattern into an n-epilayer (2.1 x 10 to the 17th power per cu cm) grown by metalorganic chemical vapor deposition (MOCVD) on an n+ substrate (2.8 x 10 to the 18th power per cu cm) and then depositing an MOCVD p epilayer (4.2 x 10 to the 18th power per cu cm). Reflectivity measurements on cells with and without an antireflective coating confirm the expected decrease in reflectance of the microgrooved cell compared to the planar structure. The short-circuit current of the V-grooved solar cell was 13 percent higher than that of the planar control.

Bailey, S. G.↗
NASA NTRS2000

Development and Testing of Cooled CMCs for High Thermal Flux Applications

Ceramic Matrix Composites (CMCS) offer the potential for significant weight savings and improved performance for a range of propulsion components utilizing refractory materials. This paper describes the fabrication and testing of functionally graded CMCs produced via a low cost process that represents an order of magnitude cost savings over conventionally fabricated CMCS. Test cylinders were fabricated, characterized and evaluated during exposure to high thermal fluxes of up to 10MW/meters squared at the Laser Hardened Materials Evaluation Laboratory (LHMEL). The bulk density of the CMC tubes was approximately 2.2 grams per cubic centimeters. The performance of cryogenically cooled CMCs was compared with uncooled CMCs against similar thermal loads, and fundamental property data collected for this relatively new breed of CMC. Finally, test thrust cells were fabricated from the functionally graded composite and tested using liquid H2 and O2 propellants at NASA Glen.

Patterson , Mark↗
NASA NTRS1987

Further study of inversion layer MOS solar cells

A group of inversion layer MOS solar cells has been fabricated. The highest value of open-circuit voltage obtained for the cells is 0.568V. One of the cells has produced a short-circuit current of 79.6 mA and an open-circuit voltage of 0.54V. It is estimated that the actual area AMO efficiency of this cell is 6.6 percent with an assumed value of 0.75 for its fill factor. Efforts made for fabricating an IL/MOS cell with reasonable efficiencies are reported. Future work for 4 sq cm IL cells and 25 sq cm IL cells is discussed.

Ho, Fat Duen↗
NASA NTRS1976

Silicon solar cells from transition metal doped Czochralski and web crystals

The influence of metallic impurities on solar cell characteristics has been examined to establish the cost sensitive purity versus performance trade-offs. Solar cells were fabricated on 2 to 4 ohm-cm p-type substrates obtained by Czochralski and dendritic web growth processes. Controlled amounts of metallic impurities were introduced into the melt during growth and included Fe, Cr, Mn, Ni, Cu, Ti, V, Zr, Mg, Zn, and Al. Impurity concentrations in the crystals were determined using emission and mass spectrographic techniques and in some cases by neutron activation analysis. The solar cells were characterized by means of a computer program to curve-fit measured voltage-current data. The principal effect of the added impurities is a degradation of lifetime and diffusion length.

Davis, J. R.↗
DOE OSTI2021

SnS Homojunction Solar Cell with n-Type Single Crystal and p-Type Thin Film

Herein, a pn homojunction SnS solar cell is fabricated for the first time by the deposition of p-type SnS polycrystalline thin films on the recently reported large n-type SnS single crystals. The p-type thin films consist of columnar grains that grow along the <100> direction, which is the same orientation as the n-type single crystal. In addition, the interface of the pn homojunctions is void-free and compositionally sharp. The SnS homojunction solar cell achieves an open-circuit voltage (VOC) of 360 mV, which is as large as the highest VOC of previously reported SnS-based heterojunction solar cells. The built-in potential of the homojunction cell is 0.92 eV, which is close to the bandgap energy of SnS (≈1.1 eV), and larger than reported for heterojunctions (≈0.7 eV). The resulting 1.4% conversion efficiency (n) of the homojunction solar cell is smaller than the record 4–5% in heterojunctions, mainly due to the low short-circuit current density (J SC ) of 7.5 mA cm -2 . Once the device structure of the homojunction cell is optimized to efficiently collect the photogenerated carriers and achieve a comparable J SC as the conventional heterojunction cells (≈25 mA cm -2 ), high n exceeding 4–5% will be realized with improving the VOC.

14 SOLAR ENERGY↗
DOE OSTI2025

Effect of high scandium doping in barium zirconate on nickel diffusion and performance of proton-conducting solid oxide electrolyzer cells

Proton-conducting solid oxide electrolyzer cells (p-SOECs) are emerging but promising technologies for hydrogen production. However, due to the lack of a robust electrolyte, p-SOECs struggle simultaneously to display high performance, Faradaic efficiency, and durability. Motivated by its high proton concentrations and stability as a barium zirconate, we have investigated BaZr 0.6 Sc 0.4 O 3-δ (BZSc40) as a potential next-generation p-SOEC electrolyte. Here, we found elevated levels of NiO diffusion through BZSc40 electrolytes during high-temperature sintering, attributed to the large oxygen vacancy concentrations present in BZSc40, as revealed by first-principle computational results. Controlling NiO diffusion is critical, as it can facilitate densification and grain size growth, but it may also detrimentally impact performance by causing electronic leakage. By optimizing sintering temperature when fabricating BZSc40 cells, we successfully controlled NiO diffusion, achieving sufficient electrolyte densification along with high performance and Faradaic efficiency. BZSc40 cells reached −0.99 A/cm 2 at 1.3 V and 600 °C and exhibited enhanced durability with a 3.37 mV/kh degradation rate at −0.8 A/cm 2 over a 200-h testing period. BZSc40 electrolytes demonstrated superior performance over BaZr 0.8 Y 0.2 O 3-δ (BZY20). In addition to elevated current densities and grain sizes, BZSc40 cells achieved Faradaic efficiencies of 76 % compared to 54 % for BZY20 at −0.2 A/cm 2 and 600 °C. This work lays the foundation for BZSc40 as a potential electrolyte due to its advantages over BZY20 while demonstrating the significance of controlling NiO diffusion when fabricating p-SOECs.

Electrolyzer↗
NASA NTRS2004

The First Cell Membranes

Organic compounds are synthesized in the interstellar medium and can be delivered to planetary surfaces such as the early Earth, where they mix with endogenous organic mixtures. Some of these compounds are amphiphilic, having polar and non-polar groups on the same molecule. Amphiphilic compounds spontaneously self-assembly into more complex structures such as bimolecular layers, which in turn form closed membranous vesicles. The first forms of cellular life required self-assembled membranes that were likely to be available on the prebiotic Earth. Laboratory simulations show that such vesicles readily encapsulate functional macromolecules, including nucleic acids and polymerases. A goal of future investigations is to fabricate artificial cells as models of the origin of life.

Deamer, David↗
NASA NTRS1997

Thermophotovoltaic Cell Technology Transferred to the Department of Energy Laboratory and a Commercial Manufacturer

Researchers in the NASA Lewis Research Center's Photovoltaic Branch have developed novel photovoltaic device, called a Monolithically Interconnected Module (MIM), for use in thermophotovoltaic (TPV) power systems. TPV power systems function by heating an emitter to produce light. This light is then converted into electricity by a photovoltaic device or a solar cell. Possible heat sources for the system include concentrated solar energy, the combustion of various fuels, and nuclear decay. NASA has an interest in TPV systems for deep space (nuclear-powered) and near-Sun (solar-powered) missions. There also are many commercial and military applications for TPV, given its potential for high efficiency, low noise, and reliable power. The Monolithically Interconnected Module consists of many small solar cells that are series-interconnected on a common substrate. The cells are fabricated from indium gallium arsenide (InGaAs), which can convert the near-infrared portion of the emitter output spectrum into electricity. The InGaAs devices are deposited on an indium phosphide (InP) substrate that provides electrical isolation. On the bottom the InP substrate is an infrared reflector that returns all the photons that are not converted by the InGaAs device back to the emitter where they are absorbed. This process helps maintain the emitter temperature and dramatically improves the system efficiency. Monolithically Interconnected Module InGaAs thermophotovoltaic cell developed by Lewis. Compared with conventional TPV cells, this TPV device has higher output voltages and lower resistive losses, higher output power density, simplified thermal management, improved reliability, and higher efficiency. The Monolithically Interconnected Module was initially developed under an internally funded effort (Director's Discretionary Fund). Development is now being funded by another government agency, and prototype devices are being produced by a commercial solar cell manufacturer.

Wilt, David M.↗
DOE OSTI2022

Post‐Annealing Treatment on Hydrothermally Grown Antimony Sulfoselenide Thin Films for Efficient Solar Cells

Herein, antimony sulfoselenide (Sb 2 (S, Se) 3 ) thin‐film solar cells are fabricated by a hydrothermal method followed by a post‐deposition annealing process at different temperatures and the impact of the annealing temperature on the morphological, structural, optoelectronic, and defect properties of the hydrothermally grown Sb 2 (S, Se) 3 films is investigated. It is found that a proper annealing temperature leads to high‐quality Sb 2 (S, Se) 3 films with large crystal grains, high crystallinity, preferred crystal orientation, smooth and uniform morphology, and reduced defect density. These results show that suppressing deep‐level defects is crucial to enhance solar cell performance. After optimizing the annealing process, Sb 2 (S, Se) 3 solar cells with an improved power conversion efficiency 2.04 to 8.48% are obtained.

14 SOLAR ENERGY↗
DOE OSTI2021

3D Printed, Low Tortuosity Garnet Framework For Beyond 500 Wh/kg Batteries

In this project, we developed LLZO garnet ink recipes and processes for 3D-printing highly ordered ionically conductive garnet porous structures on dense garnet separators. Using this technique, we are able to fabricate controlled architecture LLZO garnet solid-state electrolyte (SSE) trilayers for application in solid-state lithium batteries. The trilayer comprises a thin dense center layer sandwiched between a 3D-printed patterned porous layer and a random porous layer. The dense layer functions as the ionic separator between the anode and cathode. The random porous layer hosts the lithium-metal anode and provides the structural support. The 3D-printed SSE patterned porous layer hosts the cathode, providing continuous, low tortuosity pathways for fast 3D Li+ transport through the cell while increasing the electrode/electrolyte interface area to decrease the interfacial resistance. Compared to the random porous structure, this ordered patterned structure possesses more vacant space for higher cathode loading without sacrificing ionically conducting capability, thus potentially greatly increasing the cell energy density. For demonstration purposes, we developed two patterns for the 3D-printed porous layer: grids and columns, for hosting sulfur and NMC cathode, respectively. The corresponding two types of cells were fabricated and tested, and have demonstrated achievement of theoretical discharge capacity without cathode calendaring. In addition, we developed a fundamental solid-state ionic and electronic transport model to optimize the 3D-printed structures for maximum energy and power density. The model was validated by experiment and provides the critical design criteria for achieving the >500 Wh/kg energy goal as function of C-rate.

25 ENERGY STORAGE↗