SEARCH · Engineering Papers

Results for “reversible process”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,387 records · Page 77

All sources NASA NTRS DOE OSTI

NASA NTRS2012

Post-Flight EDL Entry Guidance Performance of the 2011 Mars Science Laboratory Mission

The 2011 Mars Science Laboratory was the first successful Mars mission to attempt a guided entry which safely delivered the rover to a final position approximately 2 km from its target within a touchdown ellipse of 19.1 km x 6.9 km. The Entry Terminal Point Controller guidance algorithm is derived from the final phase Apollo Command Module guidance and, like Apollo, modulates the bank angle to control the range flown. For application to Mars landers which must make use of the tenuous Martian atmosphere, it is critical to balance the lift of the vehicle to minimize the range error while still ensuring a safe deploy altitude. An overview of the process to generate optimized guidance settings is presented, discussing improvements made over the last nine years. Key dispersions driving deploy ellipse and altitude performance are identified. Performance sensitivities including attitude initialization error and the velocity of transition from range control to heading alignment are presented. Just prior to the entry and landing of MSL in August 2012, the EDL team examined minute tuning of the reference trajectory for the selected landing site, analyzed whether adjustment of bank reversal deadbands were necessary, the heading alignment velocity trigger was in union with other parameters to balance the EDL risks, and the vertical L/D command limits. This paper details a preliminary postflight assessment of the telemetry and trajectory reconstruction that is being performed, and updates the information presented in the former paper Entry Guidance for the 2011 Mars Science Laboratory Mission (AIAA Atmospheric Flight Mechanics Conference; 8-11 Aug. 2011; Portland, OR; United States)

Mendeck, Gavin F.↗

NASA NTRSDate not supplied

Least Squares Reverse Time Migration (LSRTM) for Damage Imaging in Composite Laminates

A method for adapting least squares reverse time migration (LSRTM) for ultrasonic guided wave imaging of composite laminates is proposed in this paper. As composites become more widely used in fields such as the aerospace industry, the need for high-resolution imaging in structural health monitoring (SHM) and nondestructive evaluation (NDE) is also growing. For instance, delamination is a common problem in composite laminates, which has led to a certain degree of apprehension in the use of composite materials for load-bearing structures. Although the solver-based imaging techniques using conventional reverse time migration (RTM) methods illuminate damage with a wide range of damage-scattering effects, the resulting images do not fully define the damage regions due to the limited data acquisition aperture, sensor density, frequencies/wavelengths, and incompleteness of adjoint reconstruction. Previously, the LSRTM theory was derived by incorporating a least squares migration (LSM) algorithm into RTM, and benchmarked its high-resolution damage imaging performance for isotropic plates. To improve damage imaging in composite laminates, a process to create an ultrasonic guided wave-based LSRTM method for anisotropic materials is proposed in this paper. The derivation of the forward modeling operator and the adjoint operator is presented. Numerical case studies were conducted to show the improvement of LSRTM over RTM in mapping damage in composite plates. Multiple damage sites or damage with a complex shape were created in the numerical studies based on 1) Born approximation-based modeling or 2) reduction of the plate stiffness-based modeling. LSRTM begins by using a forward modeling process. The forward modeling accuracy for the flexural wave solver used in this study for LSRTM was also compared with the results from a three-dimensional rotated staggered grid (RSG) elastodynamic finite difference solver, previously open-sourced by NASA Langley Research Center. These benchmarking studies have shown that the LSRTM method is more effective in reducing artifacts, improving resolution, and enhancing damage model reconstruction compared to RTM in composite laminates.

Jiaze He↗

DOE OSTI2024

Controlling reversible phase transitions in rare-earth nickelates for novel memory devices

Resistive switching in correlated complex oxides is lucrative for emerging applications in neuromorphic computing, and densely scaled non-volatile memory. Electrical conductance of such complex oxides can be controllable switched across multiple orders of magnitude by either (a) electroforming a conduction channel (e.g., in tungsten oxide), or (b) inducing Mott-Hubbard transition (e.g., in rare-earth nickelates)– both via controlled migration of defects (such as oxygen vacancies) under applied bias. Nevertheless, the promise of such defect-driven electronic transitions are far from realized due to a lack of fundamental understanding of the atomic-scale processes that underlie migration and spatiotemporal evolution of oxygen vacancies over nano-to-mesoscopic length/timescales under applied electric field. In this project, we employ a synergistic integration of density functional theory (DFT) calculations, ab initio/classical molecular dynamics (AIMD/CMD) simulations, machine learning (ML), precision synthesis, and multi-modal X-ray imaging experiments to address this knowledge gap. Such an integrated approach offers to elucidate the correlations between subtle structural distortion and oxidation states; treat localized charge carriers; describe defect/ion transport in the presence of electric field; and, in turn, greatly advance the current understanding of microstructural evolution in complex oxides under applied bias. The fundamental knowledge gained from this work will enable precise control over hierarchical defect structures and unravel new routes to manipulate resistance states in complex oxides. This, in turn, will accelerate design of novel devices with desired set of neural functionalities, and high-speed densely-scaled resistive random access memory technologies.

36 MATERIALS SCIENCE↗

DOE OSTI2025

Impacts of Disulfide‐Containing Monomers in Alternating Diene Metathesis Polymerization

ABSTRACT Among the classes of synthetic polymers, disulfide‐containing structures offer unique opportunities due to their accessibility to redox chemistry that allows for degradation or reversible disulfide formation and exchange under mild conditions. Here, we examine the role of disulfides in olefin metathesis polymerization, specifically alternating diene metathesis (ALTMET) polymerization, for synthesizing unsaturated polyolefins with embedded disulfides. Our synthetic strategy hinged on the use of α,ω‐diacrylate monomers, including those connected by a disulfide unit, via copolymerization by the ALTMET mechanism to yield copolymers containing a range of disulfide content. In addition, the potential impacts of sulfur‐ruthenium interactions on the ALTMET process were investigated spectroscopically, while the degradation of the resultant polymers was affected by mild reducing agents. Overall, this study contributes to the development of degradable synthetic polymers using olefin metathesis methods, with an increased understanding of the potential for further use of disulfide groups in such metathesis reactions.

Lee, Kyoungwon↗

DOE OSTI2021

Investigations of the stability of etched or platinized p-InP(100) photocathodes for solar-driven hydrogen evolution in acidic or alkaline aqueous electrolytes

Here, the stability of p-InP photocathodes performing the hydrogen-evolution reaction (HER) has been evaluated in contact with either 1.0 M H 2 SO 4 (aq) or 1.0 M KOH(aq), with a focus on identifying corrosion mechanisms. Stability for the solar-driven HER was evaluated using p-InP electrodes that were either etched or coated with an electrodeposited Pt catalyst (p-InP/Pt). Variables such as trace O 2 were systematically controlled during the measurements. Changes in surface characteristics after exposure to electrochemical conditions as well as electrode dissolution processes were monitored using X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma mass spectrometry (ICP-MS). In either H 2 SO 4 or KOH, etched p-InP photoelectrodes corroded cathodically under illumination, forming metallic In 0 at the electrode surface. In contrast, electrodeposition of Pt kinetically stabilized illuminated p-InP photocathodes in both H 2 SO 4 and KOH by inhibiting the cathodic corrosion pathway. Notably, when held at 0 V vs. the reversible hydrogen electrode (RHE) in 1.0 M H 2 SO 4 (aq), p-InP/Pt exhibited a stable current density (J) of ~–18 mA cm –2 for >285 h under simulated 1 Sun illumination. The long-term current density vs. potential (J–E) behavior at pH 0 and pH 14 of p-InP/Pt photocathodes correlated with changes in the surface chemistry as well as the dissolution of p-InP. In acidic media, the J–E behavior of p-InP/Pt photocathodes remained nearly constant with time, but the surface of a p-InP/Pt electrodes gradually turned P-rich via a slow and continuous leaching of In ions. In alkaline electrolyte, the surface of p-InP/Pt electrodes was passivated by formation of an InO x layer that exhibited negligible dissolution but led to a substantial degradation in the J–E characteristics. Consequently, changes in the catalytic kinetics and surface stoichiometry are both important considerations for determining the corrosion chemistry and the long-term operational stability of InP photoelectrodes.

14 SOLAR ENERGY↗

DOE OSTI2024

Constraining Cross Section and Beam Systematics for Future NOvA Sterile Neutrino Search

he NOvA (NuMI Off-axis $\nu_e$ Appearance) experiment measures neutrino oscillations in a nearly pure muon (anti)neutrino beam over a 810 km baseline. We search for sterile neutrino driven oscillations in both neutral current (NC) and charged current (CC) muon neutrino samples. A deficit of NC interactions at the Far Detector could occur since sterile neutrinos do not couple to the Z boson. A modulation of the muon neutrino disappearance probability is possible due to a new mass splitting. The NuMI beam line is capable of running in forward or reverse horn current modes, which creates a neutrino or antineutrino beam, respectively. Samples collected in forward horn current (FHC) or reverse horn current (RHC) modes are subject to beam optics uncertainties, in addition to cross section and hadron production uncertainties. We explore the ategories. To tackle reduction of cross section uncertainties, we study how splitting the neutral current (NC) samples can impact the systematic reduction and its implications on oscillation parameters, leveraging results from Monte Carlo simulations. Additionally, we look at the possibility of using a $\nu$-on-e scattering sample. The $\nu$-on-e scattering process has minimal cross section uncertainties compared to that of neutrino-nucleus interactions, which can help constrain the overall flux normalizations. Using both the ZHC sample, NC split sample, and $\nu$-on-e scattering sample jointly with FHC samples would reduce the focusing uncertainties and the hadron production uncertainties in the future sterile analysis.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2025

Leveraging Electrons for Electrochemical CO 2 Capture Using a Hemi‐Labile Iron Complex

Climate change, driven by anthropogenic carbon emissions, demands urgent action to prevent a 2050 tipping point. With CO 2 levels at 427 ppm (50% above pre-industrial levels), deploying energy-efficient carbon capture technologies is crucial. Electrochemical carbon capture processes that have been touted to have the potential to meet these needs rely on the applied cell voltage, and electron utilization (CO 2 molecules separated per electron), which has generally been asserted to have a theoretical limit of one. Here, we introduce an electron-leveraging strategy to enhance electron utilization beyond this limit to 1.43 by employing Fe-EDDHA, a redox-active coordination complex having a ligand with multiple hemi-labile coordination sites. The reversibility and robustness of the system were enabled by the efficient prevention of CO 2 reduction upon the introduction of nicotinamide as a guardian of the iron(2+) center. The proof-of-concept cyclic system exhibits a minimum operational energy of 22.6 kJ e mol −1 and an average of 63.7 kJ e mol −1 over 29 cycles, using a simulated flue gas (15% CO 2 ). Our electron-leveraging strategy holds promise for advancing energy-efficient electrochemical carbon capture technologies, and offers an alternative to prevalent redox potential shifting methods proposed to mitigate undesired electron transfer reactions in redox-active materials across diverse operational conditions.

carbon storage↗

DOE OSTI2021

Comparison of the Forward and Reverse Photocycle Dynamics of Two Highly Similar Canonical Red/Green Cyanobacteriochromes Reveals Unexpected Differences

Cyanobacteriochromes (CBCRs) are cyanobacterial photoreceptors that exhibit photochromism between two states: a thermally stable dark-adapted state and a metastable light-adapted state with bound linear tetrapyrrole (bilin) chromophores possessing 15Z and 15E configurations, respectively. The photodynamics of canonical red/green CBCRs have been extensively studied; however, the time scales of their excited-state lifetimes and subsequent ground-state evolution rates widely differ and, at present, remain difficult to predict. Here, we compare the photodynamics of two closely related red/green CBCRs that have substantial sequence identity (~68%) and similar chromophore environments: AnPixJg2 from Anabaena sp. PCC 7120 and NpR6012g4 from Nostoc punctiforme. Using broadband transient absorption spectroscopy on the primary (125 fs to 7 ns) and secondary (7 ns to 10 ms) time scales together with global analysis modeling, our studies revealed that AnPixJg2 and NpR6012g4 have comparable quantum yields for initiating the forward ( 15Z P r → 15E P g ) and reverse ( 15E P g → 15Z P r ) reactions, which proceed through monotonic and nonmonotonic mechanisms, respectively. In addition to small discrepancies in the kinetics, the secondary reverse dynamics resolved unique features for each domain: intermediate shunts in NpR6012g4 and a Meta-Gf intermediate red-shifted from the 15Z P r photoproduct in AnPixJg2. Altogether, this study supports the conclusion that sequence similarity is a useful criterion for predicting pathways of the light-induced evolution and quantum yield of generating primary intermediate Φ p within subfamilies of CBCRs, but more studies are still needed to develop a comprehensive molecular level understanding of these processes.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2021

Cost and Energy Metrics for Municipal Water Reuse

Municipal water reuse can contribute to a circular water economy in different contexts and with various treatment trains. This study synthesized information regarding the current technological and regulatory statuses of municipal reuse. It provides process-level information on cost and energy metrics for three potable reuse and one nonpotable reuse case studies using the new Water Techno-economic Assessment Pipe-Parity Platform (WaterTAP3). WaterTAP3 enabled comparisons of cost and energy metrics for different treatment trains and for different alternative water sources consistently with a common platform. A carbon-based treatment train has both a lower calculated levelized cost of water (LCOW) ($0.40/m3) and electricity intensity (0.30 kWh/m3) than a reverse osmosis (RO)-based treatment train ($0.54/m3 and 0.84 kWh/m3). In comparing LCOW and energy intensity for water production from municipal reuse, brackish water, and seawater based on the largest facilities of each type in the United States, municipal reuse had a lower LCOW and electricity than seawater but higher values than for production from brackish water. For a small (2.0 million gallon per day) inland RO-based municipal reuse facility, WaterTAP3 evaluated different deep well injection and zero liquid discharge (ZLD) scenarios for management of RO concentrate. Adding ZLD to a facility that currently allows surface discharge of concentrate would approximately double the LCOW. For all four case studies, LCOW is most sensitive to changes in weighted average cost of capital, on-stream capacity, and plant life. Baseline assessments, pipe parity metrics, and scenario analyses can inform greater observability and understanding of reuse adoption and the potential for cost-effective and energy-efficient reuse.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

DOE OSTI2024

Phase control of spin waves in the van der Waals antiferromagnet NiPS 3

Here we demonstrate phase control of magnons in the van der Waals antiferromagnet NiPS3 using optical excitation by polarized light. The sign of the coherent precession of spin amplitude changes upon (i) reversing the helicity of a circularly polarized pump beam, or (ii) rotating the polarization of a linearly polarized pump by π/2. Because these two excitation pathways have comparable generation efficiency, the phase of spin precession can be continuously tuned from 0 to 2π by controlling the polarization state of the pump pulse. The ability to excite magnons with a desired phase has potential applications in the design of a spin-wave phased array and ultrafast spin information processing.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

NASA NTRS1990

The effect of hydrogen and microstructure on the deformation and fracture behavior of a single crystal nickel-base superalloy

A study was conducted on the effects of internal hydrogen and microstructure on the deformation and fracture of a single crystal nickel-base superalloy. In particular, room temperature plane strain fracture toughness and tensile tests were performed on hydrogen-free and hydrogen charged samples of PWA 1480. The role of microstructure was incorporated by varying the levels of porosity and eutectic gamma/gamma prime through hot isostatic pressing and heat treatment. The room temperature behavior of PWA 1480 was unusual because precipitate shearing was not the primary deformation mechanism at all strains. At strains over 1 percent, dislocations were trapped in the gamma matrix and an attempt was made to relate this behavior to compositional differences between PWA 1480 and other superalloys. Another unique feature of the tensile behavior was cleavage of the eutectic gamma/gamma prime, which is believed to initiate the failure process. Fracture occurred on (111) planes and is likely a result of shear localization along these planes. Elimination of the eutectic gamma/gamma prime greatly improved the tensile ductility, but pososity had no effect on tensile properties. Large quantities of hydrogen (1.74 at. percent) were gas-phase charged into the material, but surprisingly this was not a function of the amount of porosity or eutectic gamma/gamma prime present. Desorption experiments suggest that the vast majority of hydrogen is at reversible lattice trapping sites. This large, uniform concentration of hydrogen dramatically reduced the tensile strain to failure, but only slightly affected the reduction in area. Available hydrogen embrittlement models were examined in light of these results and it was found that the hydrogen enhanced localized plasticity model can explain much of the tensile behavior. K(IC) fracture toughness tests were conducted, but it was necessary to also perform J(IC) tests to provide valid data.

Walston, William S.↗

NASA NTRS2001

Electro-Thermal Simulation Studies of SiC Junction Diodes Containing Screw Dislocations Under High Reverse-Bias Operation

The objective of this work was to conduct a modeling study of SiC P-N junction diodes operating under high reverse biased conditions. Analytical models and numerical simulation capabilities were to be developed for self-consistent electro-thermal analysis of the diode current-voltage (I-V) characteristics. Data from GRC indicate that screw dislocations are unavoidable in large area SiC devices, and lead to changes in the SiC diode electrical response characteristics under high field conditions. For example, device instability and failures linked to internal current filamentation have been observed. The physical origin of these processes is not well understood, and quantitative projections of the electrical behavior under high field and temperature conditions are lacking. Thermal calculations for SiC devices have not been reported in the literature either. So estimates or projections of peak device temperatures and power limitations do not exist. This numerical study and simulation analysis was aimed at resolving some of the above issues. The following tasks were successfully accomplished: (1) Development of physically based models using one- and two-dimensional drift-diffusion theory for the transport behavior and I-V characteristics; (2) One- and two-dimensional heat flow to account for internal device heating. This led to calculations of the internal temperature profiles, which in turn, were used to update the electrical transport parameters for a self-consistent analysis. The temperature profiles and the peak values were thus obtainable for a given device operating condition; (3) Inclusion of traps assumed to model the presence of internal screw dislocations running along the longitudinal direction; (4) Predictions of the operating characteristics with and without heating as a function of applied bias with and without traps. Both one and two-dimensional cases were implemented; (5) Assessment of device stability based on the operating characteristics. The presence of internal non-uniformities, particularly filamentary structures, was probed and demonstrated; (6) Cause and physical origins of filamentary behavior and unstable I-V characteristics were made transparent; (7) It was demonstrated that diodes containing defects would be more prone to thermal breakdown associated with the temperature dependent decrease in the thermal conductivity; and (8) Finally, negative differential resistance (S-shaped NDR) which can potential lead to device instability and filamentary behavior was shown to occur for diodes containing a line of defects such as could be associated with a screw dislocation line.

Joshi, R. P.↗

NASA NTRSDate not supplied

Single-Cell mRNA Sequencing of Bone Marrow Mesenchymal Stem Cell Lineages Shows that Gravity Mechanical Loading Regulates Regenerative Osteogenesis in a CDKN1A-Dependent Manner

Weight-bearing at 1g is increasingly recognized as an important stimulus driving stem cell-based tissue regenerative homeostasis and health. In the bone marrow compartment, mechanical stimuli from gravity can drive osteogenesis from mesenchymal progenitors and hematopoiesis from hematopoietic progenitors. Conversely, hematopoietic monocyte/macrophage progenitors can also be driven into osteoclastogenesis by mechanical unloading in microgravity. Although the cell cycle inhibitor gene Cdkn1a is known to be upregulated in microgravity, the great diversity of stem cell lineages and stages of differentiation in bone marrow, make it difficult to attribute gene expression changes to specific cell types. To overcome this limitation, we used single-cell mRNAseq analyses with both in-vitro and in-vivo strategies, including in-vitro stretch of marrow osteogenic cultures, and in-vivo hindlimb unloading, running wheels, treadmills, and exposure to real microgravity. For in-vitro studies marrow osteoprogenitors from WT and Cdkn1a-null mice were subjected to substrate stretch during osteogenesis, with static cultures simulating unloading. From those experiments we determined Cdkn1a-null cells transition more readily from progenitors to early osteoblasts and further to mineralizing osteoblasts. Additionally, single-cell mRNAseq resolution identified Cdkn1a suppression in response to mechanical loading predominantly in early proliferative osteoblasts rather than progenitor or mineralizing osteoblasts. These findings support the hypothesis that CDKN1A plays a mechano-reversible, anti-proliferative role during bone regenerative osteogenesis. To investigate in-vivo mechanoregulation of osteogenesis, mice were flown in microgravity during the Rodent Research-10 experiment comparing wildtype and Cdkn1a-null mice kept on ISS for 30 days. The mice were euthanized and dissected on-orbit in microgravity and femur bone marrow was collected using a custom sample isolation and live-cell cryo-preservation technique allowing for single cell transcriptomics post-flight processing. Ground control experiments with hindlimb-unloading, running wheels, and treadmills, were also conducted for a comprehensive analysis of mechanical loading effects on the regenerative health of bone tissue and its marrow stem cell progenitor lineages.

single cell sequencing↗

NASA NTRS2025

Diverse and Highly Differentiated Lava Suite in Jezero Crater, Mars: Constraints on Intracrustal Magmatism Revealed By Mars 2020 PIXL

The Jezero crater floor features a suite of related, iron-rich lavas that were examined and sampled by the Mars 2020 rover Perseverance , and whose textures, minerals, and compositions were characterized by the Planetary Instrument for X-ray Lithochemistry (PIXL). This suite, known as the Máaz formation (fm), includes dark-toned basaltic/trachy-basaltic rocks with intergrown pyroxene, plagioclase feldspar, and altered olivine and overlying trachy-andesitic lava with reversely zoned plagioclase phenocrysts in a K-rich groundmass. Feldspar thermal disequilibrium textures indicate that they were carried from their crustal staging area. Bulk and mafic minerals have very high FeO and low MgO to FeO total ratios, which are partially reproduced by thermodynamic models involving high-degree fractional crystallization of a gabbroic assemblage and possibly also assimilation of iron-rich basement. Together, these in situ constraints on petrogenesis provide a uniquely detailed record of intracrustal processes beneath Jezero crater during a time period not represented by Mars samples to date.

Jezero Crater floor↗

DOE OSTI2024

Discovering neutrino tridents at the Large Hadron Collider

Neutrino trident production of di-lepton pairs is well recognized as a sensitive probe of both electroweak physics and physics beyond the Standard Model. Although a rare process, it could be significantly boosted by such new physics, and it also allows the electroweak theory to be tested in a new regime. We demonstrate that the forward neutrino physics program at the Large Hadron Collider offers a promising opportunity to measure for the first time, dimuon neutrino tridents with a statistical significance exceeding $5\sigma$. We present predictions for various proposed experiments and outline a specific experimental strategy to identify the signal and mitigate backgrounds, based on "reverse tracking" dimuon pairs in the FASER$\nu$2 detector. We also discuss prospects for constraining beyond Standard Model contributions to neutrino trident rates at high energies.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

NASA NTRS1985

Buoyancy Effects upon Vapor Flame and Explosion Processes

The objective of this microgravity project is to develop an experimental and theoretical analyses critical to the understanding of the coupling of buoyancy and turbulence generation and its effect on fuel-air mixing, flame intensity and flame propagation in jet diffusion flames. The experiment is designed to examine certain effects of buoyancy acting on a diffusion flame in which the flame is directed either upward or downward. This change from negative to positive g is observed to significantly alter the flame shape although all other operating conditions are the same for both configurations. However, to perform this experiment a significant coaxial secondary air flow is needed in order to prevent flow reversal when the flame is inverted. The theoretical analysis that has been developed handles the secondary air flow and the extreme change in gravity vector direction. Thus the data will provide a measure of credibility of the analysis which will then be used to assist in the design of the actual zero-g experiment.

Edelman, R. B.↗

NASA NTRS1993

Integrating interface slicing into software engineering processes

Interface slicing is a tool which was developed to facilitate software engineering. As previously presented, it was described in terms of its techniques and mechanisms. The integration of interface slicing into specific software engineering activities is considered by discussing a number of potential applications of interface slicing. The applications discussed specifically address the problems, issues, or concerns raised in a previous project. Because a complete interface slicer is still under development, these applications must be phrased in future tenses. Nonetheless, the interface slicing techniques which were presented can be implemented using current compiler and static analysis technology. Whether implemented as a standalone tool or as a module in an integrated development or reverse engineering environment, they require analysis no more complex than that required for current system development environments. By contrast, conventional slicing is a methodology which, while showing much promise and intuitive appeal, has yet to be fully implemented in a production language environment despite 12 years of development.

Beck, Jon↗

DOE OSTI2022

Ruddlesden–Popper Perovskites with Narrow Phase Distribution for Air-Stable Solar Cells

2D Ruddlesden-Popper perovskites have risen to prominence as stable and efficient photovoltaic materials because of their structural diversity, rich photophysics, and low moisture ingression. However, thin films processed from stoichiometric precursor solutions possess a broad phase distribution of different number of inorganic layers with random crystal orientation, crippling device performance. The effect of methylammonium chloride (MACI) and 3-amino4-phenolsulfonic acid (APSA) on the fabrication of perpendicularly oriented (PEA) 2 MA 4 Pb 5 I 16 films with narrow phase distribution using antisolvent and hot-casting processing techniques is investigated. MACI plays a critical role in suppressing parasitic n ≤ 2 and 3D-like phases. APSA performs the dual function of trap passivation and further narrowing phase polydispersity through strong coordination with Pb 2+ . Ex situ grazing-incident wide-angle X-Ray scattering (GIWAXS) and ultrafast spectroscopic characterization reveal uniformly mixed-phase distribution with disordered orientation in antisolvent treated films, while additive-assisted hot-casting treatment results in oriented, reverse-graded phase distribution, i.e., small-n on the film surface and large-n at the bottom. Arising thin films enable efficient p-i-n solar cells with an efficiency of 14.34%, and a V oc of 1.20 V, retaining 96% initial efficiency after 1440 h under ambient conditions (RH = 50-60%) without encapsulation.

36 MATERIALS SCIENCE↗