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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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Assessment of Present State-of-the-art Sawing Technology of Large Diameter Ingots for Solar Sheet Material
Work is reported on: (1) slicing of the ingots with the multiblade slurry saw, the multiwire slurry saw and the I.D. saw, (2) characterization of the sliced wafers, and (3) analysis of add-on slicing cost based on Solar Array Manufacturing Industry Costing Standard.
Reduction kinetics of hercynite redox materials for solar thermochemical water splitting
Solar thermochemical water splitting (STWS) using a hercynite redox cycle is a promising technology for producing renewable H 2 . Here, the reduction kinetics of hercynite (FeAl 2 O 4 ) is evaluated using thermogravimetric and XRD analyses. The results indicate that as-prepared hercynite materials undergo reduction via two different reaction mechanisms. The reaction first proceeds by a nucleation and growth mechanism (AE1), followed by a third-order kinetic model (F3). XRD analyses show the occurrence of superstoichiometric oxygen in the spinel structure of FeAl 2 O 4+δ in the second reaction mechanism, which indicates the formation of cationic vacancies. TGA and XRD analyses confirm that hercynite maintains its spinel structure when the materials are thermally reduced and oxidized with steam. Differential scanning calorimetry (DSC) performed on FeAl 2 O 4 particles shows two heats of reaction in agreement with the two observed mechanisms. This is the first kinetics study to report on the thermal reduction of hercynite.
Method of mitigating titanium impurities effects in p-type silicon material for solar cells
Microstructural evaluation tests performed on Cu-doped, Ti-doped and Cu/Ti doped p-type silicon single crystal wafers, before and after the solar cell fabrication, and evaluation of both dark forward and reverse I-V characteristic records for the solar cells produced from the corresponding silicon wafers, show that Cu mitigates the unfavorable effects of Ti, and thus provides for higher conversion efficiency, thereby providing an economical way to reduce the deleterious effects of titanium, one of the impurities present in metallurgical grade silicon material.
Terahertz Nanoimaging of Perovskite Solar Cell Materials
Direct visualization and quantitative evaluation of charge filling in grain boundary (GB) traps of hybrid metal halide perovskites require dynamic conductivity imaging simultaneously at the terahertz (THz) frequency and nanometer (nm) spatial scales not accessible by conventional transport and imaging methods used thus far. Here, in this study, we apply a THz near-field nanoconductivity mapping to the archetypal metal halide perovskite photovoltaic films and demonstrate that it is a powerful tool to reveal distinct dielectric heterogeneity due to charge trapping and degradation at the single GB level. Our approach visualizes the filled defect ion traps by local THz charge conductivity and allows for extracting a quantitative profile of trapping density in the vicinity of GBs with sub-20 nm resolution. Furthermore, imaging material degradation by tracking local nanodefect distributions overtime identifies a distinct degradation pathway that starts from the GBs and propagates inside the grains over time. The single GB, nano-THz conductivity imaging demonstrated here can be extended to benchmark various perovskite materials and devices for their global photoenergy conversion performance and local charge transfer proprieties of absorbers and interfaces.
Lifetime and diffusion length measurements on silicon material and solar cells
Experimental methods were evaluated for the determination of lifetime and diffusion length in silicon intentionally doped with potentially lifetime-degrading impurities found in metallurgical grade silicon, impurities which may be residual in low-cost silicon intended for use in terrestrial flat-plate arrays. Lifetime measurements were made using a steady-state photoconductivity method. Diffusion length determinations were made using short-circuit current measurements under penetrating illumination. Mutual consistency among all experimental methods was verified, but steady-state photoconductivity was found preferable to photoconductivity decay at short lifetimes and in the presence of traps. The effects of a number of impurities on lifetime in bulk material, and on diffusion length in cells fabricated from this material, were determined. Results are compared with those obtained using different techniques. General agreement was found in terms of the hierarchy of impurities which degrade the lifetime.
UH cosmic rays and solar system material - The elements just beyond iron
The nucleosynthesis of cosmic-ray elements between the iron peak and the rare-earth region is examined, and compositional changes introduced by propagation in interstellar space are calculated. Theories on the origin of elements heavier than iron are reviewed, a supernova model of explosive nucleosynthesis is adopted for the ultraheavy (UH) cosmic rays, and computational results for different source distributions are compared with experimental data. It is shown that both the cosmic-ray data and the nucleosynthesis calculations are not yet of sufficient precision to pinpoint the processes occurring in cosmic-ray source regions, that the available data do provide boundary conditions for cosmic-ray nucleosynthesis, and that these limits may apply to the origin of elements in the solar system. Specifically, it is concluded that solar-system abundances appear to be consistent with a superposition of the massive-star core-helium-burning s-process plus explosive-carbon-burning synthesis for the elements from Cu to As and are explained adequately by the s- and r-processes for heavier elements.
Photoelectrochemical materials for solar energy conversion
Research and development on semiconductors for applications in solar energy conversion has witnessed rapid growth over the past several decades. With the aim of producing chemical fuels from sunlight, intense research efforts have focused on the discovery of semiconductors with crystalline structures and chemical compositions that have the potential to satisfy the complex set of required photoelectrochemical properties. This chapter focuses on the foundational structure-property relationships of selected oxide and nitride semiconductors relevant to their uses as n-/p-type photoelectrodes and as photocatalysts. Their solid-state structures and compositions are described, with a special emphasis on strategies proven effective at targeting suitable band gaps with strong visible-light absorption, efficient charge separation and diffusion of charge carriers, and optimal band edge energies for driving surface redox reactions for water splitting.
Optical characterisation of alumina–mullite materials for solar particle receiver applications
Not Available
Design, Synthesis and Characterization of Materials for Solar Thermochemical Hydrogen Production.
Abstract not provided.
Predicting and Evaluating New Water Splitting Materials for Solar Thermochemical Hydrogen Production
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Effects of impurities on carrier lifetime in bulk solar-cell material Quarterly report
Lifetime degradation in silicon irradiated with electrons
Effects of impurities on carrier lifetime in bulk solar cell material Final report
Effects of impurities on charge carrier lifetime in irradiated bulk silicon
A performance evaluation of various coatings, substrate materials, and solar collector systems
An experimental apparatus was constructed and utilized in conjunction with both a solar simulator and actual sunlight to test and evaluate various solar panel coatings, panel designs, and scaled-down collector subsystems. Data were taken by an automatic digital data acquisition system and reduced and printed by a computer system. The solar collector test setup, data acquisition system, and data reduction and printout systems were considered to have operated very satisfactorily. Test data indicated that there is a practical or useful limit in scaling down beyond which scaled-down testing cannot produce results comparable to results of larger scale tests. Test data are presented as are schematics and pictures of test equipment and test hardware.
Production of He, Ne, and Ar isotopes and U-236 in lunar materials by solar cosmic ray protons - Production rate calculations
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Preliminary evaluation of Glass Resin materials for solar cell cover use
The glass resins were deposited by several techniques on 200 micron thick cells and on 50 microns thick wafers. The covered cells were exposed to ultraviolet light in vacuum to an intensity of 10 UV energy-equivalent solar constants at air mass zero for 728 hr. The exposure was followed by a single long thermal cycle from ambient temperature to -150 C. Visual inspection of the samples indicated that all samples had darkened to varying degrees. The loss in short-circuit current was found to range from 8 to 24%, depending on the resin formulation. In another test over 40 glass resin-coated silicon wafers withstood 15 thermal cycles from 100 to-196 C in one or more of the thicknesses tested. Several of the resin-coated wafers were tested at 65 C and 90% relative humidity for 170 hr. No change in physical appearance was detected.
Study of electronic properties in proton- and electron-irradiated GaAlAs and GaAs solar cell materials
Diagnostical measurement techniques such as dark I-V, C-V, the thermally insulated capacitance, and the deep level transient spectroscopy methods were employed to study defect properties in the proton-irradiated n-GaAs materials. Defect energy levels, thermal emission rates, and capture cross sections of electrons as well as trap densities were deduced from these measurements and the results are presented. Correlations between the measured defect parameters and the dark I-V characteristics of the n-GaAs Schottky barrier diodes are also discussed. Defect energy levels (i.e., electron traps) determined are also compared with published data in order to identify their physical origins.