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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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Stoichiometric comproportionation of a dialuminyne and aluminum halides in hexane or ether cleanly yields a dialuminene which rapidly decomposes. In benzene a dialuminene/benzene cycloaddition product is generated.
Designs for an open source environmental chamber for stability testing of metal halide perovskites and other materials using optical degradation fingerprints. The design suite can accommodate bulk samples, thin films or full photovoltaic devices.
A deep understanding of the interaction of the surface of cathode materials with solid electrolytes is crucial to design advanced solid-state batteries (SSBs). This is especially true for the new class of lithium metal chloride (Li-M-Cl) solid electrolytes which are receiving rapidly growing attention due to their very high oxidative stability (>4 V) in combination with good ionic conductivity that can enable long cell cycle life. While Li-M-Cl electrolytes typically contain resource-limited metals (M) such as indium or rare earths, work has focused on substituting M with more abundant elements such as zirconium. Via operando resistance measurements using intermittent current interruption we explore the dynamic evolution of the interphase at the surface of Ni-rich NCM85 or NCM111 cathode particles inside a working SSB with three different Li-(M 1 ,M 2 )-Cl catholytes (Li 3 InCl 6 , Li 2 Sc 1/3 In 1/3 Cl 4 and Li 5/2 Y 1/2 Zr 1/2 Cl 6 ) to reveal the impact of the cationic metal substitution on the interfacial chemistry. We show that the metal plays a critical role in determining high voltage stability, contrary to prior assumptions. Using a combination of cyclic voltammetry and ultraviolet photoelectron spectroscopy measurements of the electronic band structure to assess oxidative stability; coupled with DFT calculations and ToF-SIMS to evaluate products formed at the interface at different upper cutoff potentials and degrees of delithiation, we are able to differentiate between electrochemical and chemical degradation. We find that Li 2 Sc 1/3 In 1/3 Cl 4 yields the highest (and Li 3 InCl 6 the lowest) stability against electrochemical oxidation, while Li 5/2 Y 1/2 Zr 1/2 Cl 6 undergoes a detrimental chemical reaction with oxygen released from Ni-rich NCM85 at high potentials, resulting in fast capacity fading. Altogether, our work establishes a platform for the metrics and an approach that can be utilized to efficiently evaluate the stability of new halide SEs in SSB cells.
Inorganic-based thin-film photovoltaics (TFPV) represents an important component of the growing low-carbon energy market and plays a vital role in the drive toward lower cost and increased penetration of solar energy. Yet, commercialized thin-film absorber technologies suffer from some non-ideal characteristics, such as toxic or non-abundant element use (e.g., CdTe and Cu(In,Ga)(S,Se) 2 , which bring into question their suitability for terawatt deployment. Numerous promising chalcogenide, halide, pnictide and oxide semiconductors are being pursued to bridge these concerns for TFPV and several promising paths have emerged, both as prospective replacements for the entrenched technologies, and to serve as partner (i.e., higher bandgap) absorbers for tandem junction devices—e.g., to be used with a lower bandgap Si bottom cell. The current perspective will primarily focus on emerging chalcogenide-based technologies and provide both an overview of absorber candidates that have been of recent interest and a deeper dive into an exemplary Cu 2 BaSnS 4 -related family. Altogether, considering the combined needs of high-performance, low-cost, and operational stability, as well as the experiences gained from existing commercialized thin-film absorber technologies, chalcogenide-based semiconductors represent a promising direction for future PV development and also serve to highlight common themes and needs among the broader TFPV materials family.
With promising solar cell applications, organic–inorganic lead halide perovskites belong to a novel and rapidly developing class of semiconducting materials. Unlike its well-investigated iodide counterparts, formamidinium lead chloride (FAPbCl 3 ) is a much less studied perovskite that shows superior stability and surprisingly high selectivity and sensitivity towards certain gas analytes. The origin of the sensing ability of this perovskite material can be traced to its high defect tolerance and the existence of some defects which act as the “lock” to a certain gas analyte's “key”. In this work, we deepen the understanding of this proven perovskite sensor through first-principles computational study of its defect formation energies, charge transition energies, and optical properties. These studies are done with the widely used GGA exchange–correlation functional PBE and the newer meta-GGA functional SCAN, both incorporating the Grimme's D3 dispersion correction. Additionally, we also consider experimental conditions and the effect of temperature on electron screening in the simulations, which demonstrates that screening is particularly important when considering high oxidation states of the defects. We also note the importance of antisites in the Fermi Pinning as well as the importance of FA disorder, which are previously unreported insights.
Chiral metal halide perovskites have garnered substantial interest because of their promising properties for application in optoelectronics and spintronics. Understanding the mechanism of chiral imprinting is paramount for optimizing their utility. To elucidate the nature of the underlying chiral imprinting mechanism, we investigated how the circular dichroism (CD) intensity varies with nanoparticle size for quantum confined sizes of colloidal CsPbBr 3 perovskite nanoparticles (NPs) capped by chiral β-methylphenethylammonium bromide ligands. We find that the CD intensity decreases strongly with increasing NP size, which, along with the shape of the CD spectra, points to electronic interactions between ligand and NP as the dominant mechanism of chiral imprinting in smaller NPs. We observe that as the NP size increases and crosses the quantum confinement threshold, the dominant mechanism of chirality transfer switches and is dominated by surfaces effects, e.g., structural distortions. Furthermore, these findings provide a benchmark for quantitative models of chiral imprinting.
Uranium- and thorium-iridium multimetallic species with unprecedented actinide–iridium interactions are prepared via salt-elimination reactions between U/Th halides and K[IrCp*H 3 ].
The study exhibits the beneficial effect of A-cation mixing in hybrid halide perovskites for efficient hot carrier harvesting.
Organometal halide perovskites are promising materials for optoelectronic applications, whose commercial realization depends critically on their stability under multiple environmental factors. In this study, a methylammonium lead bromide (MAPbBr 3 ) single crystal was cleaved and exposed to simultaneous oxygen and light illumination under ultrahigh vacuum (UHV). The exposure process was monitored using X-ray photoelectron spectroscopy (XPS) with precise control of the exposure time and oxygen pressure. It was found that the combination of oxygen and light accelerated the degradation of MAPbBr 3 , which could not be viewed as a simple addition of that by oxygen-only and light-only exposures. The XPS spectra showed significant loss of carbon, bromine, and nitrogen at an oxygen exposure of 10 10 Langmuir with light illumination, approximately 17 times of the additive effects of oxygen-only and light-only exposures. It was also found that the photoluminescence (PL) emission was much weakened by oxygen and light co-exposure, while previous reports had shown that PL was substantially enhanced by oxygen-only exposure. Measurements using a scanning electron microscope (SEM) and focused ion beam (FIB) demonstrated that the crystal surface was much roughened by the co-exposure. Furthermore, Density functional theory (DFT) calculations revealed the formation of superoxide and oxygen induced gap state, suggesting the creation of oxygen radicals by light illumination as a possible microscopic driving force for enhanced degradation.
Four heteroanionic oxyhalides, CeClMoO 4 , CeBrMoO 4 , CeClWO 4 , and CeBrWO 4 , have been studied as multifunctional materials, which show a combination of good second harmonic generation (SHG) response and photocurrent signals. Millimeter-sized CeHaVIO 4 (Ha = Cl, Br; VI = Mo, W) crystals were grown by halide salt flux. The crystal structure of CeHaVIO 4 crystals was accurately determined by single-crystal X-ray diffraction. CeClMoO 4 , CeBrMoO 4 , and CeBrWO 4 are isostructural to each other, and crystallize in the acentric LaBrMoO 4 structure type. CeClWO 4 crystallizes in a new structure type with unit cell parameters of a = 19.6059(2) Å, b = 5.89450(10) Å, c = 7.80090(10) Å, and β = 101.4746(8)°. The bandgaps of CeHaVIO 4 fall into the range of 2.8(1)–3.1(1) eV, which are much smaller than those of isotypic LaHaVIO 4 (Ha = Cl, Br; VI = Mo, W) in the range of 3.9(1)–4.3(1) eV. The narrowing of bandgaps in CeHaVIO 4 originates from the presence of partially filled 4f orbitals of cerium atoms, which was confirmed by density functional theory (DFT) calculations. The moderate bandgaps make CeHaVIO 4 suitable for infrared nonlinear optical (IR NLO) applications. CeBrMoO 4 and CeBrWO 4 exhibit moderate SHG responses of 0.58× AGS and 0.46× AGS, respectively, and are both type-I phase-matching materials. Moderate SHG response, easy growth of crystals, high ambient stability, and type-I phase-matching behavior make CeBrMoO 4 and CeBrWO 4 great materials for IR NLO applications. CeHaVIO 4 films also exhibited good photocurrent response upon light radiation. Furthermore, this work demonstrates the rich structural chemistry of the REHaVIO 4 (RE = Y, La–Lu; Ha = Cl, Br; VI = Mo, W) family and the potential presence of more multifunctional materials.
Dithiolene-based N-heterocyclic silane demonstrates unusual dual nucleophilic reactivity toward boron halides.
Reaction of a terphenyl bis(anilide) ligand with trivalent halide precursors of Ce and early actinides yield both neutral and “-ate” complexes. These molecules afford comparative insight into f-block metal–arene bonding.
We show in this work how lithium tellurolate Li(X) n TeCH 2 SiMe 3 (X = THF, n = 1, 1; X = 12- crown -4, n = 2, 2), can serve as an effective Te-atom transfer reagent to all group 5 transition metal halide precursors irrespective of their oxidation state.
Mn 2+ doping imposes intriguing optoelectronic properties on lead-halide perovskites; however, its impact on their crystal structure remains unclear.
Ligand-passivated ErOCl nanocrystals have been synthesized using a non-hydrolytic sol–gel method. Anisotropic sintering of ErOCl nanocrystals enhances 2D chloride-ion diffusion along theabplane, yielding a promising candidate for halide batteries.
Large and faceted nanoparticles, such as gold bipyramids, presently require synthesis using alkyl ammonium halide ligands in aqueous conditions to stabilize the structure, which impedes subsequent transfer and suspension of such nanoparticles in low polarity solvents despite success with few nanometer gold nanoparticles of shapes such as spheres. Phase transfer methodologies present a feasible avenue to maintain colloidal stability of suspensions and move high surface energy particles into organic solvent environments. Here, we present a method to yield stable suspensions of gold bipyramids in low-polarity solvents, including methanol, dimethylformamide, chloroform, and toluene, through the requisite combination of two capping agents and the presence of a co-solvent. By utilizing PEG-SH functionalization for stability, dodecanethiol (DDT) as the organic-soluble capping agent, and methanol to aid in the phase transfer, gold bipyramids with a wide-range of aspect ratios and sizes can be transferred between water and chloroform readily and maintain colloidal stability. Subsequent transfer to various organic and low-polarity solvents is then demonstrated for the first time.
Phase stability and the optoelectronic performance of the metastable CsPbI 3 host can be improved with triple-halide alloying, without excessive Br addition which widens the gap beyond that ideal for tandem-photovoltaics.
This work presents a comparative study of six types of oxide and halide solid-state electrolytes. It has been demonstrated that the electrochemical stability not only depends on metal species, but alsk the Li content and other factors.