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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Toward Superb Perovskite Oxide Electrocatalysts: Engineering of Coupled Nanocomposites

Abstract A significant issue that bedeviled the commercialization of renewable energy technologies, ranging from low‐temperature water electrolyzers to high‐temperature solid oxide cells, is the lack of high‐performance catalysts. Among various candidates that could tackle such a challenge, perovskite oxides are rising‐star materials because of their unique structural and compositional flexibility. However, single‐phase perovskite oxides are challenging to satisfy all the requirements of electrocatalysts concurrently for practical applications, such as high catalytic activity, excellent stability, good ionic and electronic conductivities, and superior chemical/thermo‐mechanical robustness. Impressively, perovskite oxides with coupled nanocomposites are emerging as a novel form offering multifunctionality due to their intrinsic features, including infinite interfaces with solid interaction, tunable compositions, flexible configurations, and maximum synergistic effects between assorted components. Considering this new configuration has attracted great attention owing to its promising performances in various energy‐related applications, this review timely summarizes the leading‐edge development of perovskite oxide‐based coupled nanocomposites. Their state‐of‐art synthetic strategies are surveyed and highlighted, their unique structural advantages are highlighted and illustrated through the typical oxygen reduction reaction and oxygen evolution reactions in both high and low‐temperature applications. Opinions on the current critical scientific issues and opportunities in this burgeoning research field are all provided.

08 HYDROGEN↗
DOE OSTI2020

Blading Phase–Pure Formamidinium–Alloyed Perovskites for High–Efficiency Solar Cells with Low Photovoltage Deficit and Improved Stability

Currently, blade-coated perovskite solar cells (PSCs) with high power conversion efficiencies (PCEs), i.e. greater than 20%, normally employ methylammonium lead tri-iodide with a sub-optimal bandgap. Alloyed perovskites with formamidinium (FA) cation have narrower bandgap and thus enhance device photocurrent. However, FA-alloyed perovskites show low phase stability and high moisture sensitivity. Here, we report that incorporating 0.83 molar percent organic halide salts (OHs) into the perovskite inks enables phase-pure, highly crystalline FA-alloyed perovskites with extraordinary optoelectronic properties. Here, the OH molecules modulate the crystal growth, enhance the phase stability, passivate ionic defects at the surface and/or grain boundaries, and enhance the moisture stability of the perovskite film. We demonstrate a high efficiency of 22.0% under 1 sun illumination for blade-coated PSCs with an open-circuit voltage of 1.18 V, corresponding to a very small voltage deficit of 0.33 V, and significantly improved operational stability with 96% of the initial efficiency retained under one sun illumination for 500 hours.

14 SOLAR ENERGY↗
DOE OSTI2023

Sustainable materials acceleration platform reveals stable and efficient wide-bandgap metal halide perovskite alloys

The vast chemical space of emerging semiconductors, like metal halide perovskites, and their varied requirements for semiconductor applications have rendered trial-and-error environmentally unsustainable. Here, in this work, we demonstrate RoboMapper, a materials acceleration platform (MAP), that achieves 10-fold research acceleration by formulating and palletizing semiconductors on a chip, thereby allowing high-throughput (HT) measurements to generate quantitative structure-property relationships (QSPRs) considerably more efficiently and sustainably. We leverage the RoboMapper to construct QSPR maps for the mixed ion FA 1-y Cs y Pb(I 1-x Br x ) 3 halide perovskite in terms of structure, bandgap, and photostability with respect to its composition. We identify wide-bandgap alloys suitable for perovskite-Si hybrid tandem solar cells exhibiting a pure cubic perovskite phase with favorable defect chemistry while achieving superior stability at the target bandgap of ~1.7 eV. RoboMapper’s palletization strategy reduces environmental impacts of data generation in materials research by more than an order of magnitude, paving the way for sustainable data-driven materials research.

36 MATERIALS SCIENCE↗
DOE OSTI2022

High-throughput oxygen chemical potential engineering of perovskite oxides for chemical looping applications

Chemical looping (CL) represents a versatile, emerging strategy for sustainable chemical and energy conversion. Designing metal oxide oxygen carriers with suitable redox properties remains one of the most critical challenges to CL due to the considerably different thermodynamic property requirements for different applications. Here, taking SrFeO 3–δ as a base-structure, this study seeks to rationally substitute its A- and/or B-site cations to tailor the equilibrium oxygen partial pressure over 20 orders of magnitude. 2401 Sr x A 1–x Fe y B 1–y O 3–δ perovskite-phase structures were investigated using high-throughput density functional theory (DFT) and 227, 273 high-entropy perovskites were screened via machine learning (ML). This significantly expands the materials design space. While most of the compositions predicted are new and nonobvious, 19 previously reported oxygen carriers, with excellent redox properties, were correctly identified by the algorithm. Moreover, we experimentally demonstrated 15 new oxygen carriers with superior redox performance. These results support the effectiveness of the high-throughput approaches for accelerated materials discovery.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

GdWN 3 is a nitride perovskite

Nitride perovskites ABN3 are an emerging and highly underexplored class of materials that are of interest due to their intriguing calculated ferroelectric, optoelectronic, and other functional properties. Incorporating novel A-site cations is one strategy to tune and expand such properties; for example, Gd 3+ is compelling due to its large magnetic moment, potentially leading to multiferroic behavior. However, the theoretically predicted ground state of GdWN 3 was a non-perovskite monoclinic structure. Here, we experimentally show that GdWN 3-y crystallizes in a perovskite structure. High-throughput combinatorial sputtering with activated nitrogen is employed to synthesize thin films of Gd 2-x W x N 3-y O y with oxygen content y < 0.05. Ex situ annealing crystallizes a polycrystalline perovskite phase in a narrow composition window near x = 1. LeBail fits of synchrotron grazing incidence wide angle x-ray scattering data are consistent with a perovskite ground-state structure. Refined density functional theory calculations that included antiferromagnetic configurations confirm that the ground-state structure of GdWN 3 is a distorted Pnma perovskite with antiferromagnetic ordering, in contrast to prior predictions. Initial property measurements find that GdWN 3-y is paramagnetic down to T = 2 K with antiferromagnetic correlations and that the absorption onset depends on cation stoichiometry. This work provides an important path toward both the rapid expansion of the emerging family of nitride perovskites and understanding their potential multiferroic properties.

14 SOLAR ENERGY↗
NASA NTRS1994

The stability of hibonite, melilite and other aluminous phases in silicate melts: Implications for the origin of hibonite-bearing inclusions from carbonaceous chondrites

Phase fields in which hibonite and silicate melt coexist with spinel CaAl4O7, gehlenitic melilite, anorthite or corundum at 1 bar in the system CaO-MgO-Al2O3-SiO2-TiO2 were determined. The hibonites contain up to 1.7 wt% SiO2. For TiO2, the experimentally determined partition coefficients between hibonite and coexisting melt D(sub i)(sup Hib/L), vary from 0.8 to 2.1 and generally decrease with increasing TiO2 in the liquid. Based on Ti partitioning between hibonite and melt, bulk inclusion compositions and hibonite-saturated liquidus phase diagrams, the hibonite in hibonite-poor fluffy Type A inclusions from Allende and at least some hibonite from hibonite-rich inclusions is relict, although much of the hibonite from hibonite-glass spherules probably crystallized metasably from a melt. Bulk compositions for all of these CAIs are consistent with an origin as melite + hibonite + spinel + perovskite phase assembalges that were partially altered and in some cases partially or completely melted. The duration of the melting event was sufficient to remove any Na introduced by the alteration process but frequently insufficient to dissolve all of the original hibonite. Simple thermochemical models developed for meteoritic melilite and hibonite solid solutions were used to obtain equilibration temperatures of hibonite-bearing phase assemblages with vapor. Referenced to 10(exp -3) atm, hibonite + corundum + vapor equilibrated at approximately 1260 C and hibonite + spinel +/- melilite + vapor at 1215 +/- 10 C. If these temperatures reflect condensation in a cooling gas of solar composition, then hibonite +/- corundum condensed first, followed by spinel and then melilite. The position of perovskite within this sequence is uncertain, but it probably began to condense before spinel. This sequence of phase appearances and relative temperatures is generally consistent with observed textures but differs from expectations based on classical condensation calculations in that equilibration temperatures are generally lower than predicted and melilite initially condenses with or even after spinel. Simple thermochemical modes for the substitution of trace elements into the Ca site of meteoritic hibonites suggest that virtually all Eu is divalent in early condensate hibonites but that Eu(2+)/Eu(#+) decreases by a factor of 20 or more during the course of condensation primarily because the ratio is proportional to the partial pressure of Al, which decreases dramatically as aluminous phase condense. The relative sizes of Eu and Yb anomalies in meteoritic hibonites and inclusions may be partly due to this effect.

Beckett, J. R.↗
DOE OSTI2023

Light-Induced Structural Dynamics and Charge Transport in Layered Halide Perovskite Thin Films

The dynamic nature of the metal halide perovskite lattice upon photoexcitation plays a vital role in their properties. Here we report an observation of light-induced structure dynamics in quasi-2D Ruddlesden–Popper phase perovskite thin films and its impact on the carrier transport properties. By a time-resolved X-ray scattering technique, we observe a rapid lattice expansion upon photoexcitation, followed by a slow relaxation over the course of 100 ns in the dark. Theoretical modeling suggests that the expansion originates from the lattice’s thermal fluctuations caused by photon energy deposition. Power dependent optical spectroscopy and photoconductivity indicate that high laser powers triggered a strong local structural disorder, which increased the charge dissociation activation energy that results in localized transport. Finally, our study investigates the impact of laser energy deposition on the lattices and the subsequent carrier transport properties, that are relevant to device operations.

2D perovskites↗
DOE OSTI2021

A Facile, One-Step Synthesis for Core–Shell Perovskite Materials via Molten Salt

Core–shell La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 (LSCF)–La 0.8 Sr 0.2 MnO 3 (LSM) heterostructure crystalline materials have been synthesized in a simple, one-step feeding method via a KNO 3 molten salt solvent. Two-phase perovskite composites can be synthesized in times as short as 10 minutes and is demonstrated for the first time in a molten salt. Further, a combination of X-ray diffraction and S/TEM energy dispersive X-ray spectroscopy has been utilized to confirm the formation of an LSM shell on LSCF cores in all samples when adjusting dwell time, core size, weight ratio between core and shell precursors, and weight ratio of powder to salt. Specifically, decreasing the LSCF core size increases core–shell yield. Smaller cores introduce a greater density of facets on the crystal surface and provide more favorable sites for LSM heterogeneous nucleation.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Eco–Friendly Solvent Engineered CsPbI 2.77 Br 0.23 Ink for Large–Area and Scalable High Performance Perovskite Solar Cells

The performance of large-area perovskite solar cells (PSCs) has been assessed for typical compositions, such as methylammonium lead iodide (MAPbI 3 ), using a blade coater, slot-die coater, solution shearing, ink-jet printing, and thermal evaporation. However, the fabrication of large-area all-inorganic perovskite films is not well developed. This study develops, for the first time, an eco-friendly solvent engineered all-inorganic perovskite ink of dimethyl sulfoxide (DMSO) as a main solvent with the addition of acetonitrile (ACN), 2-methoxyethanol (2-ME), or a mixture of ACN and 2-ME to fabricate large-area CsPbI 2.77 Br 0.23 films with slot-die coater at low temperatures (40–50 °C). The perovskite phase, morphology, defect density, and optoelectrical properties of prepared with different solvent ratios are thoroughly examined and they are correlated with their respective colloidal size distribution and solar cell performance. Here, the optimized slot-die-coated CsPbI 2.77 Br 0.23 perovskite film, which is prepared from the eco-friendly binary solvents dimethyl sulfoxide:acetonitrile (0.8:0.2 v/v), demonstrates an impressive power conversion efficiency (PCE) of 19.05%. Moreover, the device maintains ≈91% of its original PCE after 1 month at 20% relative humidity in the dark. It is believed that this study will accelerate the reliable manufacturing of perovskite devices.

binary and ternary solvent↗
DOE OSTI2023

Improved Solid-State Reaction Method for Scaled-Up Synthesis of Ceramic Proton-Conducting Electrolyte Materials

Protonic ceramic electrochemical cells (PCECs) represent promising technologies in the production of clean electricity, decarbonized hydrogen, chemicals, and fuels at intermediate temperatures. One of the challenges in commercializing PCECs is to produce the electrolyte materials on a large scale. The conventional solid-state reaction (SSR) method suffers from tedious synthesis procedures and low phase purity of the products due to the formation of unwanted secondary phases. Herein, we report an improved SSR (i-SSR) method for kilogram-scale production of high phase-purity electrolyte material BaZr 0.4 Ce 0.4 Y 0.1 Yb 0.1 O 3–δ (BZCYYb4411). In this method, the ball-milled precursor powders are pelletized prior to calcination, which effectively reduces the length of the diffusion paths between the components during perovskite phase formation. In this study, the synthesis procedure and calcination temperature are carefully optimized for efficient and repeatable production based on the powder crystallization behavior. A combined technoeconomic analysis and life cycle assessment modeling suggest that the i-SSR method could reduce the total production cost and greenhouse gas emissions by up to 19% and 39%, respectively, compared to the conventional SSR method. The high quality of the synthesized electrolyte material is corroborated by the excellent electrical conductivity and electrochemical performance of the fabricated PCEC cells.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Triple-halide wide–band gap perovskites with suppressed phase segregation for efficient tandems

Wide–band gap metal halide perovskites are promising semiconductors to pair with silicon in tandem solar cells to pursue the goal of achieving power conversion efficiency (PCE) greater than 30% at low cost. However, wide–band gap perovskite solar cells have been fundamentally limited by photoinduced phase segregation and low open-circuit voltage. Here, we report efficient 1.67–electron volt wide–band gap perovskite top cells using triple-halide alloys (chlorine, bromine, iodine) to tailor the band gap and stabilize the semiconductor under illumination. We show a factor of 2 increase in photocarrier lifetime and charge-carrier mobility that resulted from enhancing the solubility of chlorine by replacing some of the iodine with bromine to shrink the lattice parameter. We observed a suppression of light-induced phase segregation in films even at 100-sun illumination intensity and less than 4% degradation in semitransparent top cells after 1000 hours of maximum power point (MPP) operation at 60°C. By integrating these top cells with silicon bottom cells, we achieved a PCE of 27% in two-terminal monolithic tandems with an area of 1 square centimeter.

14 SOLAR ENERGY↗
DOE OSTI2022

Phase Transition Dynamics in a Complex Oxide Heterostructure

Understanding the behavior of defects in the complex oxides is key to controlling myriad ionic and electronic properties in these multifunctional materials. The observation of defect dynamics, however, requires a unique probe-one sensitive to the configuration of defects as well as its time evolution. Here, we present measurements of oxygen vacancy ordering in epitaxial thin films of SrCoO x and the brownmillerite-perovskite phase transition employing x-ray photon correlation spectroscopy. These and associated synchrotron measurements and theory calculations reveal the close interaction between the kinetics and the dynamics of the phase transition, showing how spatial and temporal fluctuations of heterointerface evolve during the transformation process. The energetics of the transition are correlated with the behavior of oxygen vacancies, and the dimensionality of the transformation is shown to depend strongly on whether the phase is undergoing oxidation or reduction. Finally, the experimental and theoretical methods described here are broadly applicable to in situ measurements of dynamic phase behavior and demonstrate how coherence may be employed for novel studies of the complex oxides as enabled by the arrival of fourth-generation hard x-ray coherent light sources.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Design of a custom vapor transport co-deposition system for scalable production of perovskite solar cells

Vacuum-deposited perovskites provide a more direct path to manufacturing large area solar cells because of ready compatibility with multilayered architectures and historic use in the electronics industry. However, vacuum compatible co-deposition of organic-inorganic perovskites remains difficult due to issues of precisely controlling the organic precursor flux. Here, we demonstrate a manufacturing prototype specifically designed for co-depositing organic-inorganic perovskites and evaluate it with respect to the influence of process parameters on film growth. Through depositing and characterizing methylammonium lead iodide (MAPbI3) perovskite films, we highlight the necessary design requirements while measuring the influence of film growth parameters on deposition rate and perovskite phases.

14 SOLAR ENERGY↗
DOE OSTI2022

Synthesis of an Isostructural Series of 12-Coordinate Lanthanide Nitrate Hybrid Double Perovskites with Cubic Symmetry

In efforts to study the periodic chemical properties of the rare earth elements and their structural chemistry, a hybrid double perovskite phase A 2 B'BX 6 with the formula ((CH 3 ) 4 N) 2 KLn(NO 3 ) 6 (Ln = La–Lu, Y ex. Pm) was synthesized that crystallizes in the cubic space group, $Fm$$\bar{3}$$m$. This series was obtained via evaporative crystallization from a mixture of Ln(NO 3 ) 3 , KNO 3 , and (CH 3 ) 4 N·NO 3 in a 1:1:2 ratio from either H 2 O or 4.0 M HNO 3 . In this double perovskite structure, the B site containing the lanthanide ion is coordinated by six bidentate nitrate ligands, with the distal N$=$O oxygen atoms coordinating the potassium on the B' site in an octahedral six-coordinate environment. The two-remaining charge-compensating (CH 3 ) 4 N + cations occupy the interstitial voids in the lattice on the A site. This periodic series was characterized via single-crystal X-ray diffraction, powder X-ray diffraction, IR, and Raman spectroscopy. Emission spectra of the Eu complex indicate a phase transition to trigonal symmetry upon cooling. In conclusion, this series is unique as it represents a rare isostructural series spanning the entirety of the rare earth elements excluding promethium with homoleptic 12-coordinate rare earth metal ions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Theoretical Investigations of Anharmonic Effects and Phonon Transport in the Cubic Phase of Crystalline Perovskite CsPbCl 3

The role of anharmonic effects on lattice dynamics and thermal transport has been investigated in the cubic phase of the CsPbCl 3 perovskite. Limitations of the harmonic approximation, which lead to phonon instabilities in the Brillouin zone, were addressed based on self-consistent phonon theory in combination with first-principles calculations and by incorporation of frequency renormalization effects from bubble and loop diagrams. This theoretical approach demonstrates significant improvements compared to results obtained using a self-consistent phonon dynamic matrix. Both the cubic-to-tetragonal phase transition temperature as well as the predicted lattice thermal conductivity values show good agreement with selected sets of available experimental data. In conclusion, the accuracy of the predicted thermal conductivity data is also tested against systems significantly larger than those allowed by quantum calculations, by using molecular dynamic simulations with machine-learning force fields.

Lattices↗
DOE OSTI2025

Coherent Strain-Inhibiting Phase Construction of Lithium-Rich Manganese-Based Oxide Toward High Mechanochemical Stability

A layered lithium-rich manganese-based oxide cathode, containing $R\overline{3}m$ (LiTMO 2 , TM = Mn, Ni, Co) and $C2/m$ (Li 2 MnO 3 ) nanodomains, utilizes both transition metals and oxygen redox to yield substantial energy density. However, the inherent heterogeneous nature and distinct nanodomain redox chemistries of layered lithium-rich oxides will inevitably cause pernicious lattice strain and structural displacement, which can hardly be eliminated by conventional doping or coating strategies and result in accelerated performance decay. Herein, we incorporate a strain-inhibiting perovskite phase coherently grown within the layered structure to effectively restrain the displacement and lattice strain during uneven Li-ion extraction. The enhanced mechanochemical stability of the designed cathode benefits the persistent structure and reversible oxygen redox, thereby achieving high initial Coulombic efficiency and stable cycling and voltage profiles. In conclusion, our approach of lattice engineering alleviates the strain and displacement caused by inhomogeneous reactivity between heterogeneous nanodomains and promotes the development of advanced cathode materials with long durability.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2003

Dopant Studies in the BaCe0.9-xZrxY0.103- System

Protonic separation membranes for the hydrogen industry require thermo-chemical stability and high conductance. The perovskite BaCe0.9Y0.1O3- exhibits excellent proton conduction at high temperatures, but shows poor thermo-chemical tability. Substituting Zr for Ce in BaZr0.9Y0.1O3- improves the thermo-chemical stability but reduces proton conduction. The objective of this work was to study the optimization of protonic conductance and thermo-chemical by changing the ratio of Ce to Zr in BaCe0.9-xZrxY0.1O3-. To elucidate the dopant effect, co-precipitation method has been developed to produce single phase perovskites of composition BaCe0.9-xZrxY0.1O3- (0=x=0.9). The co-precipitation method has been optimized to yield high purity and homogeneous powders with a particle size of 100-200 nm in diameter. The sintering characteristics were studied in temperature range of 1400-1600 C. The effect of Zr substitution on sintering behavior and thermo-chemical stability will be reported.

Zhong, Zhimin↗