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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Fe-single atom catalysts facilitate fast electron transfer with MoS 2 /SnS 2 cathodes in lithium–sulfur batteries

Lithium–sulfur batteries (LSBs) emerge as promising next-generation energy storage systems offering cost-effectiveness, environmental friendliness, and high theoretical energy density. The practical implementation of LSBs faces significant hindrances due to the shuttle effect and sluggish redox reactions. To address these challenges, single-atom catalyst (SAC) based combination materials from d-block elements can offer increased active catalytic sites, rapid charge transfer, accelerated electron migration, and fast sulfur redox conversion kinetics of lithium polysulfides (LiPSs). In this study, we fabricated three different LSB cathodes: pure S, S@MoS 2 /SnS 2 , and S@Fe–MoS 2 /SnS 2 . These cathodes were then used to explore the cycle life, capacity, rate capability, and redox kinetic reactions of LiPSs while assessing the influence of Fe-SACs on their performance. As a result, LSBs with S@Fe–MoS 2 /SnS 2 cathodes demonstrate an extended cycle life of 1000 cycles at a C-rate of 0.2C, maintaining a capacity close to 500 mA h g −1 , the highest initial discharge capacity of 1622 mA h g −1 and 1066 mA h g −1 at 0.05C and 0.2C, and excellent rate capabilities of 708 mA h g −1 and 558 mA h g −1 at 1C and 2C, respectively. The synergistic effect of the Fe-SAC-based combination cathode (S@Fe–MoS 2 /SnS 2 ) creates plentiful adsorptive and highly active catalytic sites, resulting in substantially enhanced capacity for adsorbing soluble long-chain LiPSs. This facilitates ultra-fast redox kinetics, surpassing the performance of the S@MoS 2 /SnS 2 and pure S cathodes. In the ex situ analysis, results from powder X-ray diffraction (XRD) to observe the new phase, soft X-ray absorption spectroscopy (XAS) to investigate the electronic structure, and hard X-ray photoelectron microscopy (HAXPES) with different energies (900 eV, 2000 eV, and 6000 eV) to track the chemical-state evolution of Fe-SACs in MoS 2 /SnS 2 cathodes displayed notable electrochemical reversibility involving S 8 ⇄ LiPSs ⇄ Li 2 S conversion even after 1000 cycles. Additionally, in situ, operando Raman analysis can unveil a novel catalytic mechanism of Fe-SACs in MoS 2 /SnS 2 “facilitating rapid electron transfer” during the discharge and charge processes of LSBs involving the conversion of S 8 ⇄ long-chain LiPSs ⇄ Li 2 S 2 /Li 2 S. This study elucidates the working mechanism of Fe-SAC cathodes, offering insights into overcoming the shuttle effect and facilitating sulfur redox kinetics to advance commercial LSBs.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Onset of magma ocean solidification on Mars inferred from Mn-Cr chronometry

The mantle of Mars probably differentiated through the crystallization of a magma ocean during the first tens of million years (Ma) of Solar System evolution. However, the exact timescale of large-scale silicate differentiation of the martian mantle is debated, and in particular, it remains unclear when differentiation commenced. In this paper, we applied the short-lived 53 Mn- 53 Cr system to martian meteorites in order to date the onset of large-scale mantle differentiation on Mars. The new Cr isotope data demonstrate that martian meteorites exhibit no resolvable radiogenic 53 Cr variations, and instead have a uniform +20.2±1.2 (95% conf.) parts-per-million excess in 53 Cr/ 52 Cr relative to the terrestrial mantle. The investigated groups of martian meteorites are lithologically varied and derive from diverse mantle sources that probably had variable Mn/Cr. Hence, the lack of 53 Cr variability among martian meteorites demonstrates that silicate differentiation on Mars occurred after the extinction of 53 Mn. Provided that the sources of the martian meteorites have Mn/Cr variations that are typical of the terrestrial planets, this result implies that the onset of large-scale silicate differentiation must have occurred later than 20±5 Ma after Solar System formation. The onset of silicate differentiation on Mars inferred here is significantly later than time estimates for segregation of the martian core which conservatively occurred within <10 Ma after Solar System formation. Thus, the new Mn-Cr data imply that there was a small, but resolvable, time gap of at least 5 Ma between core formation and magma ocean solidification on Mars. If the age of core segregation is taken at face value, our results imply that the martian magma ocean remained mostly molten over several Ma. This inferred longevity of the magma ocean is inconsistent with thermal models predicting rapid (<1 Ma) solidification of the martian magma ocean. Although there is currently no unique solution to this conundrum, our results can potentially be explained by a protracted history of impact bombardment that delayed differentiation in a shallow magma ocean on Mars, or perhaps more readily, by the presence of an early and dense atmosphere that acted as an insulator and prevented the magma ocean from cooling quickly.

58 GEOSCIENCES↗
DOE OSTI2023

Chronology of alkali anorthosite 14304 clast “b” records basin forming impact at ~3.95 Ga

Alkali-suite rocks constitute one of three major suites of lunar crustal rocks. As such, constraining their formation timescales and petrogenesis is important for understanding the earliest magmatic history of the Moon. However, the magmatic history of alkali-suite rocks is partly obscured by superimposed effects of major basin-forming impact events on the lunar nearside. Consequently, unambiguous crystallization ages of samples from this suite of rocks have not been determined. Here, the aim of this study is to better understand the petrogenetic history of the alkali-suite and the potential superimposed effects of impact metamorphism by determining Sm-Nd, Rb-Sr, and 40 Ar/ 39 Ar ages for an alkali anorthosite clast from Apollo 14 lithic breccia 14304 termed clast “b”. The new chronologic measurements of clast “b” yield concordant Sm-Nd, Rb-Sr, and 40 Ar/ 39 Ar ages of 3947 ± 13 Ma, 3975 ± 34 Ma, and 3937 ± 37 Ma respectively, resulting in a weighted mean age of 3949 ± 11 Ma. This age is not interpreted to date an igneous event related to production of the lunar highlands crust and instead the chronology and petrography of clast “b” are most readily explained by an impact event at ~3.95 Ga that caused near-complete isotopic re-equilibration of the Sm-Nd, Rb-Sr, and 40 Ar/ 39 Ar chronometers. The weighted mean age of 3949 ± 11 Ma of clast “b” is several hundred Ma younger than 4.3–4.4 Ga ages typically determined for samples of other crustal rock suites but in very good agreement with independent estimates for the formation of Imbrium basin ejecta and other marginally older impact events which are thought to have been sampled at the Apollo 14 landing site. Thus, although petrologic and geochemical examination suggest that clast “b” is a pristine igneous clast, its age likely records an impact event at the Apollo 14 landing site. Whereas the various determined ages of clast “b” do not reflect the timescales of alkali-suite magmatism, the relatively low initial Sr and Nd isotopic compositions of clast “b” indicate that its protolith evolved with very low 147 Sm/ 144 Nd and 87 Rb/ 86 Sr that are distinct from estimates for urKREEP but similar to that of lunar plagioclase. This implies that the igneous protolith of clast “b” derived from a plagioclase-dominated KREEP-rich source that must have formed after the formation of the urKREEP source at ~4.35 Ga but well before the impact event recorded by clast “b” at ~3.95 Ga.

58 GEOSCIENCES↗
DOE OSTI2026

Influence of Pt-Metal Alloy Catalysts with Various Ionomers on Oxygen Reduction Reaction in Fuel Cell Application

Pt-M/C (M = Co, Ni, Mn, etc.) alloy catalysts exhibit superior oxygen reduction reaction (ORR) activity compared to pure Pt/C, leading to a high energy efficiency in hydrogen fuel cells. However, many Pt-M/C alloy catalysts were synthesized and evaluated at the lab scale in model test-bed systems like rotating disc electrodes, which don't always correlate to performance within a fuel cell system; there is a clear need to evaluate catalysts in electrodes that can be prepared at industrially relevant scales to evaluate how factors like ink formulation can greatly affect device-level of fuel cell performance. Herein, three commercial Pt-M/C alloy catalysts (two Pt-Co/C and one Pt-Ni/C) were comprehensively characterized by various techniques. The results show that the average particle sizes of the three catalysts are close to 5 nm; the atomic ratio of Pt/M is around 4; and the M was successfully embedded into Pt lattice, resulting in the positive shift of Pt 4f in XPS spectra and XRD patterns. These catalytic materials were incorporated into 9 different cathode catalyst layers (CCLs) with three kinds of ionomers (Nafion D2020, high oxygen permeability ionomer (HOPI), and Aquivion D79-25BS), and their performance in proton exchange membrane fuel cells (PEMFCs) were investigated. The results demonstrate that the Pt-Co/C catalysts possess a higher mass activity (MA) than Pt-Ni/C; the cathodes with Nafion ionomer provide the highest MA while electrodes with Aquivion ionomer showed the lowest activity, attributed to poor H+ conductivity resulting from suboptimal ionomer incorporation. Finally, these alloys were shown to exceed DOE targets for MA and H2/Air performance reported in the recent publications at beginning of life and after 90k cycle catalyst AST protocol. This study provides valuable performance benchmarks for these materials guiding future Pt-M/C catalyst design and material integration for heavy duty PEMFC applications.

08 HYDROGEN↗
DOE OSTI2020

Ultrastructures and Mechanics of Annealed Nephila clavipes Major Ampullate Silk

The semicrystalline protein structure and impressive mechanical properties of major ampullate (MA) spider silk make it a promising natural alternative to polyacrylonitrile (PAN) fibers for carbon fiber manufacture. However, when annealed using a similar procedure to carbon fiber production, the tensile strength and Young’s modulus of MA silk decrease. Despite this, MA silk fibers annealed at 600 °C remain stronger and tougher than similarly annealed PAN but have a lower Young’s modulus. Although MA silk and PAN graphitize to similar extents, annealing disrupts the hydrogen bonding that controls crystal alignment within MA silk. Consequently, unaligned graphite crystals form in annealed MA silk, causing it to weaken, while graphite crystals in PAN maintain alignment along the fiber axis, strengthening the fibers. Finally, these shortcomings of spider silk when annealed provide insights into the selection and design of future alternative carbon fiber precursors.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Reducing Surface Recombination Velocity of Methylammonium-Free Mixed-Cation Mixed-Halide Perovskites via Surface Passivation

We control surface recombination in the mixed-cation, mixed-halide perovskite, FA0.83Cs0.17Pb(I0.85Br0.15)3, by passivating nonradiative defects with the polymerizable Lewis base (3-aminopropyl)trimethoxysilane (APTMS). We demonstrate average minority carrier lifetimes >4 µs, nearly single exponential monomolecular photoluminescence decays, and high external photoluminescence quantum efficiencies (>20%, corresponding to ~97% of the maximum theoretical quasi-Fermi-level splitting) at low excitation fluence. We confirm both the composition and valence band edge position of the FA0.83Cs0.17Pb(I0.85Br0.15)3 perovskite using multi-institutional, cross-validated, X-ray photoelectron spectroscopy and UV photoelectron spectroscopy measurements. We extend the APTMS surface passivation to higher bandgap double-cation (FA and Cs) compositions (1.7, 1.75, and 1.8 eV) as well as the widely used triple-cation (FA, MA, and Cs) composition. Finally, we demonstrate that the average surface recombination velocity decreases from ~1000 to ~10 cm/s post APTMS passivation for FA0.83Cs0.17Pb(I0.85Br0.15)3. Our results demonstrate that surface-mediated recombination is the primary nonradiative loss pathway in many methylammonium (MA)-free mixed-cation mixed-halide films with a range of different bandgaps, which is a problem observed for a wide range of perovskite active layers and reactive electrical contacts. Our study also provides insights to develop passivating molecules that help reduce surface recombination in MA-free mixed-cation mixed-halide films and indicates that surface passivation and contact engineering will enable near-theoretical device efficiencies with these materials.

14 SOLAR ENERGY↗
DOE OSTI2020

Engineering Surface Oxygenated Functionalities on Commercial Carbon toward Ultrafast Sodium Storage in Ether-Based Electrolytes

The pursuit of a high-capacity anode material has been urgently required for commercializing sodium-ion batteries with a high energy density and an improved working safety. In the absence of thermodynamically stable sodium intercalated compounds with graphite, constructing nanostructures with expanded interlayer distances is still the mainstream option for developing high-performance carbonaceous anodes. In this regard, a surface-functionalized and pore-forming strategy through a facile CO 2 thermal etching route was rationally adopted to engineer negligible oxygenated functionalities on commercial carbon for boosting the sodium storage process. Benefitted from the abundant ionic/electronic pathways and more active reaction sites in the microporous structure with noticeable pseudocapacitive behaviors, the functionalized porous carbon could achieve a highly reversible capacity of 505 mA h g -1 at 50 mA g -1 , an excellent rate performance of 181 mA h g -1 at 16,000 mA g -1 , and an exceptional rate cycle stability of 176 mA h g -1 at 3200 mA g -1 over 1000 cycles. These outstanding electrochemical properties should be ascribed to a synergistic mechanism, fully utilizing the graphitic and amorphous structures for synchronous intercalations of sodium ions and solvated sodium ion compounds, respectively. Finally, the controllable generation and evolution of a robust but thin solid electrolyte interphase film with the emergence of obvious capacitive reactions on the defective surface, favoring the rapid migration of sodium ions and solvated species, also contribute to a remarkable electrochemical performance of this porous carbon black.

25 ENERGY STORAGE↗
DOE OSTI2020

Suppressing Cation Migration in Triple-Cation Lead Halide Perovskites

Ion migration represents an intrinsic instability of metal halide perovskite solar cells. In this work, we show that triple-cation FA x MA y Cs 1–x–y PbI 3 [FA + = (NH 2 ) 2 CH + , MA + = CH 3 NH 3 + ] active layers with mixed orthorhombic, post-perovskite (δ ortho -CsPbI 3 ), and cubic perovskite (α) phases (i.e., α/δ-phase FA x MA y Cs 1–x–y PbI 3 ) exhibit improved cation stability against applied bias relative to pure α-phase perovskites (i.e., FA 0.85 Cs 0.15 PbI 3 and FA 0.76 MA 0.15 Cs 0.09 PbI 3 ). Infrared photothermal heterodyne imaging and time-of-flight secondary ion mass spectrometry are used to visualize exclusive α-phase perovskite lateral device A + cation accumulation (depletion) at perovskite negative (positive) electrode interfaces. The resulting compositional heterogeneities lead to degradation. Operational stability testing of solar cells reveals similar degradation behavior; α/δ-phase FA x MA y Cs 1–x–y PbI 3 lateral devices/solar cells, by contrast, show improved stabilities. Enhanced α/δ-FA x MA y Cs 1–x–y PbI 3 stability is rationalized by δortho-phase inclusions, acting as barriers through which A + cations do not easily migrate. This study thus provides new insights into cation migration in FA x MAyCs 1–x–y PbI 3 perovskites and suggests a materials design strategy toward suppressing cation instabilities in hybrid perovskites.

14 SOLAR ENERGY↗
DOE OSTI2020

Encapsulated Sb and Sb 2 O 3 particles in waste-tire derived carbon as stable composite anodes for sodium-ion batteries

A conductive network of waste-tire derived carbon (WTC) was used to produce homogeneous Sb/WTC and Sb 2 O 3 /WTC composite materials via ball milling as promising anodes for sodium-ion batteries (SIBs). Highly reversible redox peaks at 0.81/0.71, 0.25 V for Sb/WTC and 0.80/0.76, 0.21/0.26 V for Sb 2 O 3 /WTC anodes have been observed related to Na + intercalation and deintercalation in carbon and Na–Sb and Na 3 Sb as plausible conversion/alloy reactions. Sodium half-cells delivered reversible discharge capacities of 206 mA h g -1 and 207 mA h g -1 at a current density of 37 mA g -1 for the composite Sb/WTC and Sb 2 O 3 /WTC materials, respectively. Both the Sb/WTC and Sb 2 O 3 /WTC composite materials showed impressive capacity retention with 85% and 88%, respectively after 100 cycles. Furthermore, rate capability studies at 60 °C yielded an enhanced capacity of 240 mA h g -1 for Sb/WTC and 300 mA h g -1 for Sb 2 O 3 /WTC at 37 mA g -1 .

25 ENERGY STORAGE↗
DOE OSTI2022

Covalently integrated silica nanoparticles in poly(ethylene glycol)-based acrylate resins: thermomechanical, swelling, and morphological behavior

Nanocomposites integrate functional nanofillers into viscoelastic matrices for electronics, lightweight structural materials, and tissue engineering. Herein, the effect of methacrylate-functionalized (MA-SiO 2 ) and vinyl-functionalized (V-SiO 2 ) silica nanoparticles on the thermal, mechanical, physical, and morphological characteristics of poly(ethylene glycol) (PEG) nanocomposites was investigated. The gel fraction of V-SiO 2 composites decreases upon addition of 3.8 wt% but increases with further addition (>7.4 wt%) until it reaches a plateau at 10.7 wt%. The MA-SiO 2 induced no significant changes in gel fraction and both V-SiO 2 and MA-SiO 2 nanoparticles had a negligible impact on the nanocomposite glass transition temperature and water absorption. The Young's modulus and ultimate compressive stress increased with increasing nanoparticle concentration for both nanoparticles. Due to the higher crosslink density, MA-SiO 2 composites reached a maximum mechanical stress at a concentration of 7.4 wt%, while V-SiO 2 composites reached a maximum at a concentration of 10.7 wt%. Scanning electron microscopy, transmission electron microscopy, and small-angle X-ray scattering revealed a bimodal size distribution for V-SiO 2 and a monomodal size distribution for MA-SiO 2 . Although aggregates were observed for both nanoparticle surface treatments, V-SiO 2 dispersion was poor while MA-SiO 2 were generally well-dispersed. Finally, these findings lay the framework for silica nanofillers in PEG-based nanocomposites for advanced manufacturing applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

The fall, recovery, classification, and initial characterization of the Hamburg, Michigan H4 chondrite

Abstract The Hamburg meteorite fell on January 16, 2018, near Hamburg, Michigan, after a fireball event widely observed in the U.S. Midwest and in Ontario, Canada. Several fragments fell onto frozen surfaces of lakes and, thanks to weather radar data, were recovered days after the fall. The studied rock fragments show no or little signs of terrestrial weathering. Here, we present the initial results from an international consortium study to describe the fall, characterize the meteorite, and probe the collision history of Hamburg. About 1 kg of recovered meteorites was initially reported. Petrology, mineral chemistry, trace element and organic chemistry, and O and Cr isotopic compositions are characteristic of H4 chondrites. Cosmic ray exposure ages based on cosmogenic 3 He, 21 Ne, and 38 Ar are ~12 Ma, and roughly agree with each other. Noble gas data as well as the cosmogenic 10 Be concentration point to a small 40–60 cm diameter meteoroid. An 40 Ar‐ 39 Ar age of 4532 ± 24 Ma indicates no major impact event occurring later in its evolutionary history, consistent with data of other H4 chondrites. Microanalyses of phosphates with LA‐ICPMS give an average Pb‐Pb age of 4549 ± 36 Ma. This is in good agreement with the average SIMS Pb‐Pb phosphate age of 4535.3 ± 9.5 Ma and U‐Pb Concordia age of 4535 ± 10 Ma. The weighted average age of 4541.6 ± 9.5 Ma reflects the metamorphic phosphate crystallization age after parent body formation in the early solar system.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Whole-lithosphere shear during oblique rifting

Processes controlling the formation of continental whole-lithosphere shear zones are debated, but their existence requires that the lithosphere is mechanically coupled from base to top. We document the formation of a dextral, whole-lithosphere shear zone in the Death Valley region (DVR), southwest United States. Dextral deflections of depth gradients in the lithosphere-asthenosphere boundary and Moho are stacked vertically, defining a 20–50-km-wide, lower lithospheric shear zone with ~60 km of shear. These deflections underlie an upper-crustal fault zone that accrued ~60 km of dextral slip since ca. 8–7 Ma, when we infer that whole-lithosphere shear began. This dextral offset is less than net dextral offset on the upper-crustal fault zone (~90 km, ca. 13–0 Ma) and total upper-crustal extension (~250 km, ca. 16–0 Ma). We show that, before ca. 8–7 Ma, weak middle crust decoupled upper-crustal deformation from deformation in the lower crust and mantle lithosphere. Between 16 and 7 Ma, detachment slip thinned, uplifted, cooled, and thus strengthened the middle crust, which is exposed in metamorphic core complexes collocated with the whole-lithosphere shear zone. Midcrustal strengthening coupled the layered lithosphere vertically and therefore enabled whole-lithosphere dextral shear. Where thick crust exists (as in pre–16 Ma DVR), midcrustal strengthening is probably a necessary condition for whole-lithosphere shear.

58 GEOSCIENCES↗
DOE OSTI2025

Transmission Electron Microscopy Characterization of Fuel Cladding Chemical Interaction between Minor Actinides bearing U-Pu-Zr Fuel and AIM1 Cladding

Minor actinides (MA) significantly contribute to the long-term radiotoxicity of spent nuclear fuel (SNF). Separating MA from SNF and incorporating it into metallic fuels for fast reactor transmutation is a potential method to reduce this radiotoxicity. Here, this study focuses on transmission electron microscopy characterization of two samples from the fuel cladding chemical interaction (FCCI) region of an americium (Am) and neptunium (Np)-bearing (MA-bearing) uranium-plutonium-zirconium (U-Pu-Zr) fuel irradiated in the Phenix fast reactor to 9.5 % FIMA burnup at approximately 550 °C cladding temperature. The results show that despite the complex chemical interactions between MA and AIM1 cladding elements, excessive FCCI was not induced, and Am penetration depth in the cladding limited to less than 4 µm. Np remained mostly inside fuel. The Zr-rich compounds layer effectively limited the accumulation of lanthanide on the inner cladding surface. Overall, the FCCI behavior between investigated MA-bearing U-Pu-Zr fuel and AIM1 cladding is benign.

Chemical interaction↗
DOE OSTI2021

Detrital U-Pb zircon and 40 Ar/ 39 Ar muscovite geochronology from Middle Pennsylvanian strata in the Anadarko Basin, Texas Panhandle, USA

The Late Mississippian-Permian Anadarko Basin formed in Texas and Oklahoma, USA as the result of inversion of Neoproterozic and Cambrian rift structures. Subsidence was driven by flexural loading of the Amarillo-Wichita Uplift, and this uplift may represent the easternmost element of the Ancestral Rocky Mountains system. The northwestern part of this basin has generally been interpreted to have been filled by sediment derived from the Ancestral Front Range Uplift, ~475 km to the northwest during the early stages of basin filling. We test this model using U-Pb detrital zircon and 40 Ar/ 39 Ar detrital muscovite results from three subsurface samples of the Morrow B sandstone in the northwestern part of the Anadarko Basin. We provide a new maximum depositional age of 310.9 ± 4.9 Ma that indicates the age of the Morrow B to be no older than late Atokan to early Desmoinesian Age (Moscovian), ~10 Myr younger than previously interpreted. In contrast to some previous interpretations, we propose that the most likely source for the sediment in the Morrow B is the Amarillo Uplift to the south. Detrital zircon and detrital muscovite data have age peaks at 900–1300 Ma, 1370 Ma and 1600–1800 Ma corresponding to derivation from Grenville, Granite-Rhyolite and Yavapai-Mazatzal basement provinces, respectively. A dominant detrital zircon peak at 1370 Ma suggests that Mesoproterozoic granites in the Amarillo Uplift were exposed by Middle Pennsylvanian time, and detritus eroded from the Amarillo Uplift dominated the lowstand sediment budget of the Texas Panhandle during this time; small volumes of sediment were likely sourced from the Ancestral Front Range. In conclusion, this study presents the first detrital geochronology data from the subsurface Anadarko Basin and the first detrital muscovite data from late Paleozoic southwestern Laurentia. The results presented here highlight the interpretive power of combined detrital zircon and muscovite datasets.

58 GEOSCIENCES↗
DOE OSTI2023

Effects of Residual DMSO Adduct on Photonically Cured MAPbI 3 Solar Cells

Defects and impurities in halide perovskite solar cells can negatively impact device performance and long-term stability. In this study, we identify photonically cured methylammonium (MA) lead iodide films contain a residual adduct, MA 2 Pb 3 I 8 (dimethyl sulfoxide) 2 (MA 2 Pb 3 I 8 (DMSO) 2 ), that reduces photocurrent generation in perovskite solar cells (PSCs). This is evidenced by a decrease in the external quantum efficiency (EQE) near 400 nm. Similar EQE reductions were observed in PSCs produced using high-speed processes but have not been thoroughly examined. Through X-ray diffraction patterns and Fourier transform infrared spectroscopy, we establish the photo-inactive MA 2 Pb 3 I 8 (DMSO) 2 as the culprit for the EQE reduction. Combined experimental and simulation results reveal that the MA 2 Pb 3 I 8 (DMSO) 2 phase is located at the hole transport layer/ interface, not on the surface, resulting in lower quantum efficiency and surface photovoltage in the short wavelength region. The residual adduct is kinetically trapped due to the short processing time (20 ms) and crystallization direction but can be removed by an additional photonic pulse. Furthermore, this study highlights the need for careful examination of resulting materials beyond device efficiency when transitioning from laboratory processing to industrial high-speed methods.

14 SOLAR ENERGY↗
DOE OSTI2020

Origin of Rashba Spin-Orbit Coupling in 2D and 3D Lead Iodide Perovskites

isaWhittaker-Brooks2 & Tho D. Nguyen1* We studied spin dynamics of charge carriers in the superlattice-like Ruddlesden-Popper hybrid lead iodide perovskite semiconductors, 2D (BA)2(MA)Pb2I7 (with MA= CH3NH3, and BA= CH3(CH2)3NH3), and 3D MAPbI3 using the magnetic field effect (MFE) on conductivity and electroluminescence in their light emitting diodes (LEDs) at cryogenic temperatures. The semiconductors with distinct structural/ bulk inversion symmetry breaking, when combined with colossal intrinsic spin–orbit coupling (SOC), theoretically give rise to giant Rashba-type SOC. We found that the magneto-conductance (MC) magnitude increases monotonically with the emission intensity and saturates at ≈0.05% and 0.11% for the MAPbI3 and (BA)2(MA)Pb2I7, respectively. The magneto-electroluminescence (MEL) response with similar line shapes as the MC response has a significantly larger magnitude, and essentially stays constant at ≈0.22% and ≈0.20% for MAPbI3 and (BA)2(MA)Pb2I7, respectively. The sign and magnitude of the MC and MEL responses can be quantitatively explained in the framework of the Δg-based excitonic model using rate equations. Remarkably, the width of the MEL response in those materials linearly increases with increasing the applied electric field, where the Rashba coefficient in (BA)2(MA) Pb2I7 is estimated to be about 7 times larger than that in MAPbI3. Our studies might have significant impact on future development of electrically-controlled spin logic devices via Rashba-like effects

36 MATERIALS SCIENCE↗
DOE OSTI2021

Structural insight into host plasma membrane association and assembly of HIV-1 matrix protein

Oligomerization of Pr55 Gag is a critical step of the late stage of the HIV life cycle. It has been known that the binding of IP6, an abundant endogenous cyclitol molecule at the MA domain, has been linked to the oligomerization of Pr55 Gag . However, the exact binding site of IP6 on MA remains unknown and the structural details of this interaction are missing. Here, we present three high-resolution crystal structures of the MA domain in complex with IP6 molecules to reveal its binding mode. Additionally, extensive Differential Scanning Fluorimetry analysis combined with cryo- and ambient-temperature X-ray crystallography and GNM-based transfer entropy calculations identify the key residues that participate in IP6 binding. Our data provide novel insights about the multilayered HIV-1 virion assembly process that involves the interplay of IP6 with PIP2, a phosphoinositide essential for the binding of Pr55 Gag to membrane. IP6 and PIP2 have neighboring alternate binding sites within the same highly basic region (residues 18–33). This indicates that IP6 and PIP2 bindings are not mutually exclusive and may play a key role in coordinating virion particles’ membrane localization. Based on our three different IP6-MA complex crystal structures, we propose a new model that involves IP6 coordination of the oligomerization of outer MA and inner CA domain’s 2D layers during assembly and budding.

60 APPLIED LIFE SCIENCES↗