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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Europium Addition Reduces Local Structural Disorder and Enhances Photoluminescent Yield in Perovskite CsPbBr 3

Correlative X-ray microscopy, including synchrotron X-ray diffraction and fluorescence, is leveraged to understand the local role of europium as a B-site additive in CsPbBr 3 perovskite crystals. Europium addition reduces microstrain in the perovskite, despite the fact that the degree of europium incorporation into the perovskite varies locally, with a maximum loading over twice the nominal stoichiometry. The presence of europium improves photoluminescence yield and bandwidth, while shifting the emission to bluer wavelengths. Lastly, europium-containing crystals have greatly improved X-ray hardness. The findings show promise for europium as an additive in perovskite optoelectronic devices.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Low‐Temperature Synthesis of Stable CaZn 2 P 2 Zintl Phosphide Thin Films as Candidate Top Absorbers

Abstract The development of tandem photovoltaics and photoelectrochemical solar cells requires new absorber materials with bandgaps in the range of ≈1.5–2.3 eV, for use in the top cell paired with a narrower‐gap bottom cell. An outstanding challenge is finding materials with suitable optoelectronic and defect properties, good operational stability, and synthesis conditions that preserve underlying device layers. This study demonstrates the Zintl phosphide compound CaZn 2 P 2 as a compelling candidate semiconductor for these applications. Phase‐pure, ≈500 nm‐thick CaZn 2 P 2 thin films are prepared using a scalable reactive sputter deposition process at growth temperatures as low as 100 °C, which is desirable for device integration. Ultraviolet‐visible spectroscopy shows that CaZn 2 P 2 films exhibit an optical absorptivity of ≈10 4 cm −1 at ≈1.95 eV direct bandgap. Room‐temperature photoluminescence (PL) measurements show near‐band‐edge optical emission, and time‐resolved microwave conductivity (TRMC) measurements indicate a photoexcited carrier lifetime of ≈30 ns. CaZn 2 P 2 is highly stable in both ambient conditions and moisture, as evidenced by PL and TRMC measurements. Experimental data are supported by first‐principles calculations, which indicate the absence of low‐formation‐energy, deep intrinsic defects. Overall, this study shall motivate future work integrating this potential top cell absorber material into tandem solar cells.

14 SOLAR ENERGY↗
DOE OSTI2022

A phase 2 study of sorafenib combined with conventional therapies in refractory central nervous system leukemia

Background Patients with refractory central nervous system leukemia (CNSL) have a dismal prognosis and lack effective therapy. Case reports have shown that sorafenib is effective against brain metastases, including leukemia. Methods To explore the efficacy of sorafenib combined with conventional therapies for refractory CNSL, a phase 2 study was conducted. The primary end point was the complete remission rate (CRR) within 8 weeks of treatment. Secondary end points included the overall response rate (ORR), event‐free survival (EFS), overall survival (OS), and adverse events (AEs). Results Twenty‐six patients with refractory CNSL were enrolled; they included 17 with isolated CNSL, 7 with hematological relapse, and 2 with another extramedullary relapse. After 8 weeks of treatment, 21 patients achieved complete remission, 2 achieved partial remission, and 3 achieved no remission for a CRR of 80.8% (95% CI, 62.1%‐91.5%) and an ORR of 88.5% (95% CI, 71.0%‐96.0%). Twenty patients survived, and 6 died. The 2‐year EFS and OS rates were 75.0% (95% CI, 54.5%‐88.3%) and 76.9% (95% CI, 54.2%‐90.4%), respectively. Six patients experienced grade 3 or 4 treatment‐related AEs, including moderate chronic graft‐vs‐host disease (n = 3), grade 3 or 4 acute graft‐vs‐host disease (n = 2), and grade 3 skin rash (n = 1). No treatment‐related deaths occurred during the therapy of refractory CNSL. Conclusions Sorafenib combined with conventional therapies is effective and safe for refractory CNSL. Lay Summary Sorafenib combined with conventional therapies is effective and safe for refractory central nervous system leukemia.

Chen, Xiaoxia↗
DOE OSTI2021

A Poisson–Nernst–Planck Model of Ion Transport and Interface Segregation in Metal–Insulator–Semiconductor Structures and Solar Cells

A numerical model that describes the transport of mobile ionic species in metal–insulator–semiconductor (MIS) and photovoltaic (PV) devices subject to temperature and voltage stress is presented. The finite element method (FEM) is used to solve the Nernst–Planck equation while imposing Poisson's equation self-consistently as a restriction for the electrostatic potential. This allows the contribution of the ionic species to the potential to be taken into account. Using a variational formulation eases the implementation of diverse boundary conditions, including the incorporation of segregation kinetics at the device interfaces. Segregation across the dielectric–semiconductor interface is relevant to modeling the electronic device degradation in systems where contamination reaches the semiconductor. The model in closed systems with no-flux boundary conditions is validated first. In the limiting case of low contamination levels with respect to the gate bias, the FEM solution matches analytically derived approximations. Then, the implementation is broadened to include an open boundary at the dielectric–semiconductor interface to account for leakage of ions. The predicted time dependence of the flatband voltage in Na-contaminated MIS test structures agrees well with measurements. This model successfully captures the role of long-range ion transport at concentrations of relevance to electronic and PV device instability and neuromorphic computing.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

Enhanced resistance to helium irradiations through unusual interaction between high-entropy-alloy and helium

Finding high performance plasma-facing materials (PFMs) is one of the most important and challenging tasks for realizing the commercial application of fusion reactors. Herein, we found the CrMoTaWV high entropy alloy (HEA) is highly resistant to low-energy and high-flux He plasma exposure. The nanochannel HEA film has 20 times higher initial fluence for the formation of fuzz and a remarkable 8.9 times slower fuzz growth rate than those of W. Combining the in-situ TEM observation and the Molecular dynamics (MD) simulation of the He bubble growth process, a new mechanism for the enhanced radiation resistance in HEA with the unusual interaction between HEA and He is found, where, differing from traditional metal, bubble growth in HEA leads to non-directional emission of interstitial atoms while HEA greatly suppress the growth of He bubbles. Additionally, the special nanochannel structure further rise the radiation resistance through releasing He out of the HEA film and reducing the He concentration. This new nanochannel refractory HEA material presents a promising choice as the PFMs with excellent performance and a much longer serving lifetime for future commercial fusion reactors.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Optimizing feed modulation for coupled methane and NO x conversion over Pd-Pt/Mn 0.5 Fe 2.5 O 4 /Al 2 O 3 monolith catalyst

Here the impacts of feed modulation (frequency, amplitude) and catalyst design (composition and architecture) parameters are reported for the conversion of methane and NO x over a dual-layer Pt+Pd/Al 2 O 3 + Mn 0.5 Fe 2.5 O 4 /Al 2 O 3 monolith. CH 4 and NO x conversion data show that the dual-layer catalyst outperforms single-layer samples having the same catalyst loadings, with and without spinel. Close proximity of the PGM and MFO functions in the mixed-layer catalyst lowers the CH 4 conversion at high temperature while separating the PGM and spinel layers with an intermediate Al 2 O 3 layer does not. Methane conversion enhancement is linked to its nonmonotonic dependence on O 2 . The performance gains are tied to a transient activity spike that occurs during the lean-to-rich feed transition when water is present in the feed. The transient spike is attributed to the removal of CO and H 2 products via reactions with stored O 2 in the spinel, eliminating inhibition of methane steam reforming.

03 NATURAL GAS↗
DOE OSTI2023

Facile hyperpolarization chemistry for molecular imaging and metabolic tracking of [1– 13 C]pyruvate in vivo

Hyperpolarization chemistry based on reversible exchange of parahydrogen, also known as Signal Amplification By Reversible Exchange (SABRE), is a particularly simple approach to attain high levels of nuclear spin hyperpolarization, which can enhance NMR and MRI signals by many orders of magnitude. SABRE has received significant attention in the scientific community since its inception because of its relative experimental simplicity and its broad applicability to a wide range of molecules, however, in vivo detection of molecular probes hyperpolarized by SABRE has remained elusive. Here we describe a first demonstration of SABRE-hyperpolarized contrast detected in vivo, specifically using hyperpolarized [1– 13 C]pyruvate. Biocompatible formulations of hyperpolarized [1– 13 C]pyruvate in, both, methanol-water, and ethanol-water mixtures followed by dilution with saline and catalyst filtration were prepared and injected into healthy Sprague Dawley and Wistar rats. Effective hyperpolarization-catalyst removal was performed with silica filters without major losses in hyperpolarization. Metabolic conversion of pyruvate to lactate, alanine, and bicarbonate was detected in vivo. Pyruvate-hydrate was also observed as a minor byproduct. Measurements were performed on the liver and kidney at 4.7 T via time-resolved spectroscopy and chemical-shift-resolved MRI. In addition, whole-body metabolic measurements were obtained using a cryogen-free 1.5 T MRI system, illustrating the utility of combining lower-cost MRI systems with simple, low-cost hyperpolarization chemistry to develop safe and scalable molecular imaging.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Absorption dissymmetry factor enhancement: A data-driven approach to unravel the synthesis knobs of chiral 2D perovskites

Chiral 2D metal halide perovskites (MHPs) are promising for spin-optoelectronic applications, yet their absorption dissymmetry factor (g abs ) exhibits significant variability due to complex, co-dependent structural and experimental factors. Here, we established a data-driven framework using Pearson’s correlation, ANOVA, and Gaussian process regression to identify and model key synthesis “knobs” governing these properties. The analysis revealed that solvent choice is the primary factor driving variability. For acetonitrile-based films, g abs was maximized by optimizing annealing temperature and film thickness. Conversely, films from higher boiling point solvents showed complex dependencies on annealing temperature, excitonic integral intensity, and film texture. These statistical correlations provide a roadmap for the rational design of high-performance chiral MHPs and establish a foundation for future machine learning-driven material exploration.

ANOVA↗
DOE OSTI2023

In-situ determination of moisture- and temperature-driven deflection of an encapsulated Si photovoltaic cell

Module reliability and service lifetime are critical factors in improving photovoltaic system performance and reducing the levelized cost of electricity (LCOE). Soldering and lamination of the cell impart residual stresses that persist over time and superimpose additional loads during operation. This paper demonstrates the use of X-ray Topography (XRT) to image in-situ the dynamic response of a glass/backsheet mini-module upon drying at elevated temperature after saturation at humidity levels compatible with accelerated testing. The local water content in the encapsulant is also determined in-situ over time via Water Reflectometric Detection (WaRD), with diffusion of water in the front (glass side) and rear (backsheet side) resolved. As water diffuses out from the back of the glass/backsheet module, the cell curves towards the backsheet concomitantly. Here we find that the cell edges deflect 40μm out-of-plane with respect to its center while the encapsulant dries, compared to ~100 μm deflection when heating from 25°C to 85°C. The local cell deflections (changes in cell orientation) are correlated with the dynamic loss of water in the backside encapsulant. We conclude that the observed cell deflections are the result of hygroscopic stress induced by the encapsulant upon moisture outdiffusion. Therefore, the cell experiences a continually changing stress state and curvature dependent on local humidity and temperature. Depending on cell architecture and interconnection, this “breathing” mode of the cell may induce wear out and fatigue of the interconnects, affect the electrical connection of cracked pieces or cause failure near the interconnected edges of two cells.

14 SOLAR ENERGY↗
DOE OSTI2021

EIF3H knockdown inhibits malignant melanoma through regulating cell proliferation, apoptosis and cell cycle

Highlights: • EIF3H is highly expressed in malignant melanoma and correlated with tumor stage and risk of lymphatic metastasis. • Knockdown of EIF3H inhibits cell proliferation, cell migration and promotes cell apoptosis of melanoma in vitro. • Knockdown of EIF3H suppresses tumor growth in vivo. Malignant melanoma (MM) causes 80% of skin cancer-related deaths and becomes the most lethal type of skin cancer. The molecular mechanism of MM is still not clear. This study aimed to reveal the relationship between MM and EIF3H. Clinical specimens were collected to preliminarily explore the role of EIF3H in MM. MM cell lines with EIF3H knockdown were constructed for investigating the effects of EIF3H on cell proliferation, apoptosis, cell cycle and cell motility. Mice xenograft model was constructed for verification in vivo. We found that EIF3H was obviously upregulated in MM tissues compared with normal skin tissues, which was correlated with tumor stage and risk of lymphatic metastasis. The in vitro results indicated that silencing EIF3H in MM cells could significantly suppress cell proliferation, promote cell apoptosis and induce cell cycle arrest. Moreover, EIF3H knockdown significantly restrained cell motility through regulating EMT-related proteins. The effects of EIF3H knockdown were also verified in mice xenograft model, which were represented by slower growth rate, smaller volume and lighter weight of tumors. Therefore, EIF3H was identified as a critical factor in the development and progression of MM which may be used as a novel therapeutic target in the treatment of MM.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2020

Effects of X-rays on Perovskite Solar Cells

Synchrotron micro- and nanoprobe beamlines have demonstrated great potential to advance photovoltaic devices. Most importantly, their small X-ray spot size has enabled the direct correlation of electrical performance with elemental composition at subgrain resolution for a variety of polycrystalline solar cells. Whereas the bulk of most inorganic semiconductors is stable under the high X-ray flux of focused X-ray beams, semiconductors with organic components are prone to a variety of degradation mechanisms. This is particularly critical to evaluate for the emerging organometal halide perovskite solar cells. In this study, we investigate the effects of hard X-rays on the nanoscale performance and elemental distribution of these solar cells. We show that their composition does not change during common operando and in situ measurements at synchrotron nanoprobes. However, we found a significant X-ray-induced electronic degradation of solar cells with methylammonium lead iodide absorbers. Time- and dose-dependent measurements unveiled two characteristic degradation time constants on the order of 12 and 200 s that are independent of the X-ray flux. On the basis of heat and dose simulations, we attribute the fast decay to the dose-driven creation of recombination centers, while the slow decay is compatible with the observation of compositional changes. Finally, we detail how degradation-induced measurement artifacts can be outrun and showcase the high correlation of the X-ray-beam-induced current with the iodine and lead distribution.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗