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At least 1,549 records · Page 86
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Perovskite-Derived Cs 2 SnCl 6 –Silica Composites as Advanced Waste Forms for Chloride Salt Wastes

Advanced materials and processes are required to separate halides and fission products from complex salt waste streams associated with the chemical reprocessing of used nuclear fuels and molten salt reactor technologies for immobilization into chemically durable waste forms. Here, in this work, we explore an innovative concept using metal-halide perovskites as advanced host phases to incorporate Cs and Cl with very high waste loadings. Wet chemistry-synthesized Cs 2 SnCl 6 powders from CsCl salt solutions are successfully encapsulated into a silica matrix to form a composite using low-temperature spark plasma sintering with tunable Cs and Cl loadings up to 31 wt.% and 26 wt.%, respectively. Chemical durability testing of the composite waste forms by semi-dynamic leaching experiments demonstrates that incongruent leaching mechanism dominated. The metal-halide perovskite-silica composite waste forms display exceptional chemical durability with the long-term release rates of Cs and Cl comparable to or outperforming the state-of-the-art waste form materials but with significantly higher waste loadings. The scalable synthesis of the metal-halide perovskite from wet-chemistry processes opens up new opportunities in designing perovskite-glass composite waste forms for salt wastes with very high waste loadings and exceptional chemical durability for the sustainable development of advanced fuel cycles and next-generation reactor technologies.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Simultaneous Ligand Exchange Fabrication of Flexible Perovskite Solar Cells using Newly Synthesized Uniform Tin Oxide Quantum Dots

Halide perovskite solar cells (HPSCs) have a significant potential for future photovoltaic systems because of a high power conversion efficiency (PCE) exceeding 23% using solution processing methods. A low-temperature processed oxide layer is a challenging issue for large-scale manufacture of flexible and low-cost HPSCs. Here, we propose a simple reverse micelle-water injection method for highly dispersed ligand-capped ultrafine SnO2 quantum dots (QD). Interestingly, we observed that the ligands, which help in the formation of a uniform SnO2 QD thin film, spontaneously exchange for halide through a perovskite solution, and finally we form a suitable SnO2 QD-halide junction for high-performance HPSCs. The flexible HPSC with the SnO2 QD-halide junction formed via the ligand exchange exhibits a high PCE of 17.7% using a flexible substrate. It also shows an excellent flexibility, where the initial PCE is maintained within 92% after 1000 bending cycles with a bending radius of 18 mm.

14 SOLAR ENERGY↗
DOE OSTI2016

Photon Transport in One-Dimensional Incommensurately Epitaxial CsPbX 3 Arrays

One-dimensional nanoscale epitaxial arrays serve as a great model in studying fundamental physics and for emerging applications. With an increasing focus laid on the Cs-based inorganic halide perovskite out of its outstanding material stability, we have applied vapor phase epitaxy to grow well aligned horizontal CsPbX 3 (X: Cl, Br, or I or their mixed) nanowire arrays in large scale on mica substrate. The as-grown nanowire features a triangular prism morphology with typical length ranging from a few tens of micrometers to a few millimeters. Structural analysis reveals that the wire arrays follow the symmetry of mica substrate through incommensurate epitaxy, paving a way for a universally applicable method to grow a broad family of halide perovskite materials. We have studied the unique photon transport in the one-dimensional structure in the all-inorganic Cs-based perovskite wires via temperature dependent and spatially resolved photoluminescence. Furthermore, epitaxy of well oriented wire arrays in halide perovskite would be a promising direction for enabling the circuit-level applications of halide perovskite in high-performance electro-optics and optoelectronics.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Origin of Reversible Photoinduced Phase Separation in Hybrid Perovskites

The distinct physical properties of hybrid organic-inorganic materials can lead to unexpected nonequilibrium phenomena that are difficult to characterize due to the broad range of length and time scales involved. For instance, mixed halide hybrid perovskites are promising materials for optoelectronics, yet bulk measurements suggest the halides reversibly phase separate upon photoexcitation. By combining nanoscale imaging and multiscale modeling, we find that the nature of halide demixing in these materials is distinct from macroscopic phase separation. We propose that the localized strain induced by a single photoexcited charge interacting with the soft, ionic lattice is sufficient to promote halide phase separation and nucleate a light-stabilized, low-bandgap, ~8 nm iodide-rich cluster. The limited extent of this polaron is essential to promote demixing because by contrast bulk strain would simply be relaxed. Photoinduced phase separation is therefore a consequence of the unique electromechanical properties of this hybrid class of materials. Furthermore, exploiting photoinduced phase separation and other nonequilibrium phenomena in hybrid materials more generally could expand applications in sensing, switching, memory, and energy storage.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Multifunctional Thiol-Containing Additives for Improved Photoluminescence and Photovoltaic Performance of Cs 0.15 FA 0.85 PbI 3 Perovskites

Thiol containing molecules as both interfacial surface ligands and additives are promising modulators for enhancing photoluminescence (PL) properties, stability, and photovoltaic (PV) performance of metal halide perovskites. However, alkanethiols are much more effective for improving photoluminescence (PL) intensity and stability in metal halide perovskite nanocrystals than in their thin film analogues. Herein, we investigate how additional functional groups on a pyrimidine core can alter thiol reactivity and influence the PL, stability, and PV performance of organic metal halide perovskites. Through an investigation of five different pyrimidine derivatives, it is shown that all derivatives containing thiol groups form thiolates in the presence of the perovskite precursors and increase the photoluminescence intensity of the perovskite film. The largest all-around improvement to the PL intensity, stability, and photovoltaic performance of Cs 0.15 FA 0.85 PbI 3 perovskites is realized through the addition of a hydroxyl group combined with a trifluoromethyl group to form 4-hydroxy-6-(trifluoromethyl)pyrimidine-2-thiol. Furthermore, this investigation helps illuminate how combinations of functional groups can be employed to further increase the beneficial effects over monofunctional additives in organic metal halide perovskites.

14 SOLAR ENERGY↗
DOE OSTI2025

Interplay Between Metastability and Mechanically Induced Structural Instability in CsPbBr 3 Photovoltaic Perovskite

An atomic-level understanding of the underlying structural metastability is still absent in halide perovskite photovoltaic systems. Focusing on the model material CsPbBr 3 , the impact of mechanically induced atomic structure alteration is elucidated through structural modeling and X-ray diffraction measurements. Sudden Cs–Br bond breaking drives the system metastability, where the first-order transition arises from cation-halide bond strain relief by severing the corner connectivity of the PbBr 6 units. The pressure–volume and entropy terms govern the Gibbs free-energy landscape in halide perovskites. In conclusion, metastability is revealed as a critical factor limiting the performance of lead halide perovskites under extreme but natural environments.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Roll-to-Roll Printing of Perovskite Solar Cells

High efficiency combined with transformative roll-to-roll (R2R) printability makes metal halide perovskite-based solar cells the most promising solar technology to address the terawatt challenge of the future energy demand. However, translation from lab-scale deposition solution processing techniques to large-scale R2R methods has typically led to reduced photovoltaic performance. Here, we demonstrate large-scale, highly crystalline, uniaxially oriented, smooth perovskite films printed at room temperature and in the ambient environment. Confirmed with high speed in situ X-ray diffraction measurements, the perovskite films reach 98% of relative crystallinity at room temperature and display high texture within 1 s of the coating. We demonstrate an all-blade-coated metal halide perovskite cell with power conversion efficiency (PCE) up to 19.6%, a slot-die coated cell with a PCE of 17.3%, and a partially R2R slot-die coated flexible glass-based cell efficiency of 14.1%. As a result the developed printing method can be applied to diverse perovskite compositions, enabling a variety of bandgaps to pave the way for the future R2R printing of highly efficient perovskite–perovskite tandem cells.

14 SOLAR ENERGY↗
DOE OSTI2023

Using Methyl Bromide for Interspecies Cell–Cell Signaling and As a Reporter in a Model Soil Consortium

Synthetic microbial communities are emerging as model systems for studying consortia-scale phenotypes. To establish synthetic biology tools for studying these communities in hard-to-image environmental materials, we evaluated whether a single member of a model soil consortium (MSC) can be programmed to report on gene expression without requiring matrix disruption. For these studies, we targeted a five member MSC that includes Dyadobacter fermentans, Ensifer adhaerens, Rhodococcus sp003130705, Streptomyces sp001905665, and Variovorax beijingensis. By coupling the expression of a methyl halide transferase to a constitutive promoter, we show that Variovorax beijingensis can be programmed to synthesize methyl halides that accumulate in the soil headspace at levels that are ≥24-fold higher than all other MSC members across a range of environmentally-relevant hydration conditions. We find that methyl halide production can report on a MSC promoter that is activated by changes in water potential, and we demonstrate that a synthetic gas signal can be read out directly using gas chromatography and indirectly using a soil-derived Methylorubrum that is programmed to produce a visual output in response to methyl halides. Finally, these tools will be useful for future studies that investigate how MSC respond to dynamic hydration conditions, such as drought and flood events induced by climate change, which can alter soil water potential and induce the release of stored carbon.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Low‐Bandgap Mixed Tin‐Lead Perovskites and Their Applications in All‐Perovskite Tandem Solar Cells

Abstract Efficient organic–inorganic metal halide perovskite absorbers have gained tremendous research interest in the past decade due to their super optoelectronic properties and defect tolerance. Lead (Pb) halide perovskites enable highly efficient perovskite solar cells (PSCs) with a record power conversion efficiency (PCE) of over 23%. However, the energy bandgaps of Pb halide perovskites are larger than the optimal bandgap for single junction solar cells, governed by the Shockley–Queisser (SQ) radiative limit. Mixed tin (Sn)‐Pb halide perovskites have drawn significant attention, since their bandgap can be tuned to below 1.2 eV, which opens a door for fabricating all‐perovskite tandem solar cells that can break the SQ radiative limit. This review summarizes the development of low‐bandgap mixed Sn‐Pb PSCs and their applications in all‐perovskite tandem solar cells. Its aim is to facilitate the development of new approaches to achieve high efficiency low‐bandgap single‐junction mixed Sn‐Pb PSCs and all‐perovskite tandem solar cells.

Wang, Changlei↗
DOE OSTI2024

What Matters for the Charge Transport of 2D Perovskites?

Abstract Compared to 3D perovskites, 2D perovskites exhibit excellent stability, structural diversity, and tunable bandgaps, making them highly promising for applications in solar cells, light‐emitting diodes, and photodetectors. However, the trade‐off for worse charge transport is a critical issue that needs to be addressed. This comprehensive review first discusses the structure of 3D and 2D metal halide perovskites, then summarizes the significant factors influencing charge transport in detail and provides a brief overview of the testing methods. Subsequently, various strategies to improve the charge transport are presented, including tuning A′‐site organic spacer cations, A‐site cations, B‐site metal cations, and X‐site halide ions. Finally, an outlook on the future development of improving the 2D perovskites’ charge transport is discussed.

Zhang, Yixin↗
DOE OSTI2024

Exciton Transport in Perovskite Materials

Halide perovskites have emerged as promising materials for a wide variety of optoelectronic applications, including solar cells, light‐emitting devices, photodetectors, and quantum information applications. In addition to their desirable optical and electronic properties, halide perovskites provide tremendous synthetic flexibility through variation of not only their chemical composition but also their structure and morphology. At the heart of their use in optoelectronic technologies is the interaction of light with electronic excitations in the form of excitons. This review discusses the properties and behavior of excitons in halide perovskite materials, with a particular emphasis on low‐dimensional perovskites and the effects of nanoscale morphology on excitonic behavior. The basic theory of excitonic energy migration in semiconductor nanomaterials is introduced, and novel observations in halide perovskite nanomaterials that have evolved our current understanding are explored. Lastly, many important questions that remain unanswered are presented and exciting emerging directions in low‐dimensional perovskite exciton physics are discussed.

2D materials↗
DOE OSTI2023

Turn‐on Circularly Polarized Luminescence in Chiral Indium Chlorides by 5s 2 Metal Centers

Abstract Introducing chirality into the metal‐halide hybrids has enabled many emerging properties including chiroptical activity, spin‐dependent transport, and ferroelectricity. However, most of the chiral metal‐halide hybrids to date are non‐emissive, and the underlying mechanism remains elusive. Here, we show a new strategy to turn on the circularly polarized luminescence (CPL) in chiral metal‐halide hybrids. We demonstrate that alloying Sb 3+ into chiral indium‐chloride hybrids dramatically increases the photoluminescence quantum yield in two new series of chiral indium‐antimony chlorides. These materials exhibit strong CPL signals with tunable energy and a high dissymmetry factor up to 1.5×10 −2 . Mechanistic studies reveal that the emission originates from the self‐trapped excitons centered in 5s 2 Sb 3+ . Moreover, near‐ultraviolet pumped white light is demonstrated with a polarization up to 6.0 %. Our work demonstrates new strategies towards highly luminescent chiral metal‐halide hybrids.

Wang, Zhiyu↗
DOE OSTI2022

Turn-on Circularly Polarized Luminescence in Chiral Indium Chlorides by 5s 2 Metal Centers

Introducing chirality into the metal-halide hybrids has enabled many emerging properties including chiroptical activity, spin-dependent transport, and ferroelectricity. However, most of the chiral metal-halide hybrids to date are non-emissive, and the underlying mechanism remains elusive. Here, in this study, we show a new strategy to turn on the circularly polarized luminescence (CPL) in chiral metal-halide hybrids. We demonstrate that alloying Sb 3+ into chiral indium-chloride hybrids dramatically increases the photoluminescence quantum yield in two new series of chiral indium-antimony chlorides. These materials exhibit strong CPL signals with tunable energy and a high dissymmetry factor up to 1.5×10 -2 . Mechanistic studies reveal that the emission originates from the self-trapped excitons centered in 5s 2 Sb 3+ . Moreover, near-ultraviolet pumped white light is demonstrated with a polarization up to 6.0 %. Our work demonstrates new strategies towards highly luminescent chiral metal-halide hybrids.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Direct Reduction of Alkyl Monohalides at Silver in Dimethylformamide: Effects of Position and Identity of the Halogen

Abstract Electrochemical reduction of primary (1‐halodecane), secondary (2‐halohexane and cyclohexyl halide), and tertiary halides ( tert ‐butyl halide) at a silver cathode in dimethylformamide (DMF) containing 0.050 M tetramethylammonium perchlorate (TMAP) was investigated with the aid of cyclic voltammetry and controlled‐potential (bulk) electrolysis for iodides, bromides, and chlorides. Selected reductions were probed in dried DMF–TMAP and DMF containing tetra‐ n ‐hexylammonium perchlorate (THAP). Cyclic voltammograms reveal that the number of cathodic peaks and their potentials are highly dependent on the identity and position of the halogen as well as the composition of the solvent–electrolyte. Intermediates arising from bulk electrolysis of these halides at silver undergo both radical and carbanion reactions. Electrolysis products depend on the identity and position of the halogen, amount of residual water, and size of the electrolyte cation in the solvent–electrolyte. Theoretical calculations of molecular dipole moments and polarizabilities were performed and compared to experimental observations.

Strawsine, Lauren M.↗
DOE OSTI2026

Distinct Melt Infusion Architectures of Antiperovskite Solid Electrolytes

Antiperovskite solid electrolytes are an emerging class of lithium‐ion conductors distinguished by their unusually low melting points, enabling scalable, low‐temperature processing routes not accessible to most solid electrolytes. In this work, we synthesize phase‐pure chloride (Cl), bromide (Br), and mixed halide (ClBr) variants of antiperovskites and investigate their ionic conductivities in both powder and hot‐pressed forms. Hot pressing significantly enhances conductivity across all compositions, while energy‐dispersive X‐ray spectroscopy (EDS) of the mixed halide system reveals halide surface migration during densification. We further investigate the melt‐infiltration behavior of these electrolytes into substrates relevant to solid‐state battery architectures, including Al and Cu current collectors, conventional NMC and LFP cathodes, and a foamed NMC cathode with a highly porous architecture. The foamed cathode enables deep and uniform electrolyte penetration, highlighting the role of electrode architecture in facilitating melt infiltration. Across all substrates, electrolyte halide chemistry strongly influences wetting behavior, penetration depth, and resulting microstructural morphology. Together, these results establish clear processing–structure relationships for melt‐infiltrated antiperovskite solid electrolytes and demonstrate how electrolyte chemistry and electrode architecture govern interfacial morphology during integration, providing practical guidelines for processing and structural design in solid‐state battery systems.

antiperovskite↗
DOE OSTI2025

Carboxyl-functionalized perovskite enables ALD growth of a compact and uniform ion migration barrier

Mixed-halide wide-band-gap perovskites are critical components of highly efficient tandem cells, but their operating stability is limited by halide migration. Metal oxides deposited via atomic layer deposition (ALD) have been shown to block halide migration; however, previously pursued methods result in inhomogeneous nucleation and growth. We hypothesized that functionalizing the perovskite surface with ALD-active carboxyl groups could promote nucleation and enable higher-temperature metal oxide growth. We find that 5-ammonium valeric acid iodide (5-AVAI) facilitates the formation of a compact and uniform aluminum oxide (Al 2 O 3 ) layer and allows growth at 100°C compared with the previous limit of 75°C. We demonstrate that halide migration into the C 60 electron transport layer is reduced by a factor of 10 compared with the reference case. Finally, Al 2 O 3 -capped perovskite solar cells with a band gap of 1.78 eV retain 90% of their initial power conversion efficiency after 1,000 h of continuous operation under 1-sun illumination at 55°C.

Al2O3↗
DOE OSTI2018

Evaluation of electronic state of Cs-adsorbed clay minerals by NEXAFS analysis using DFT calculations

In this work, a combined analytical method of NEXAFS measurement and DFT-calculation was employed for the evaluation of Cs states in clay minerals. The measured Cs M 4,5 NEXAFS spectra of Cs halides were analyzed using the DFT-calculations in order to establish the analytical methods. The NEXAFS spectra of the Cs halides were well reproduced by incorporating the core-hole strength. The Cs M 4,5 NEXAFS spectrum of the clay minerals was well reproduced by the DFT-calculations including the major transitions and tail structures with the established method. Further evaluation of this spectrum by charge density analysis suggested that these major transitions and the tail structures likely reflect the bonding state and the local environment around the Cs atoms. Comparison of electronic states of Cs in the clay mineral with those in the Cs halides by DFT-calculations has shown that the interaction between Cs and the nearest-neighbor atom is largest in the clay mineral, which differs from those of Cs halides. This happened due to the energy level of Cs-5s and 5p, which was closer to that of O-2s and 2p than the s and p orbitals of other alkali metal and alkali earth metal elements.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Efficient and stable perovskite solar cells based on blade-coated CH 3 NH 3 PbI 3 thin films fabricated using “green” solvents under ambient conditions

Metal halide perovskites are considered the most promising candidates for solar cells of the decade due to their exceptional optical and electronic properties. The power conversion efficiency of metal halide perovskites, when incorporated as the active layer of solar cells, has become comparable to that observed for conventional silicon solar cells. However, the stability, scaleup, green solvent usage, and fabrication in ambient conditions of metal halide perovskites need to be solved for commercial applications. Here, in this work, we report the fabrication of blade-coated methylammonium lead iodide (MAPbI 3 ) perovskite thin films using methylamine and acetonitrile as “green” solvents under ambient conditions. Our perovskite films are initially prepared from low purity PbI2 (99%) and are blade-coated in dry air at relative humidity (RH) levels above 30%. A significant advantage of fabricating our perovskite thin films via blade-coating protocols is that there is a minimal amount of precursors (5 μL) used compared to spin-coating methods (50μL–60μL) for a 4 cm 2 substrate. With the addition of a small amount of an organic halide salt, namely, phenethylammonium chloride, the film crystallinity is improved and non-radiative recombination is suppressed, resulting in power conversion efficiencies over 20%. In addition, the device maintains more than 95% of its initial efficiency after 500 h under continuous light illumination of 1-sun at open circuit conditions, 50 °C and 60% RH. The above method leads a path towards the commercial fabrication of perovskite solar cells.

14 SOLAR ENERGY↗