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NASA NTRS2004

Gas Hydrate Stability at Low Temperatures and High Pressures with Applications to Mars and Europa

Gas hydrates are implicated in the geochemical evolution of both Mars and Europa [1- 3]. Most models developed for gas hydrate chemistry are based on the statistical thermodynamic model of van der Waals and Platteeuw [4] with subsequent modifications [5-8]. None of these models are, however, state-of-the-art with respect to gas hydrate/electrolyte interactions, which is particularly important for planetary applications where solution chemistry may be very different from terrestrial seawater. The objectives of this work were to add gas (carbon dioxide and methane) hydrate chemistries into an electrolyte model parameterized for low temperatures and high pressures (the FREZCHEM model) and use the model to examine controls on gas hydrate chemistries for Mars and Europa.

Marion, G. M.↗

DOE OSTI2022

Electrical-Discharge-Machining Contamination Removal from Metal Additively Manufactured Components

The use of an electrochemical dissolution process is shown to remove the recast layer contamination from the surfaces of electrical-discharge-machining cut components, as well as the interior exposed surfaces of the structure. The solution chemistry, cell potential, and exposure time are all relevant interdependent variables. Optimization of the electrode geometry should be made for each type of component. For the case of Cu-Zn recast contamination of 300-series alloy components, surface composition analysis indicates that complete electrochemical dissolution is achieved using a dilute solution of nitric acid (HNO 3 ). For example, electrochemical dissolution of the Cu-Zn recast is accomplished at 1.2 V cell potential using a 20% nitric solution and an exposure time of 4 h. The use of a nitric acid bath was specifically chosen since it’s chemically compatible and will not degrade the host alloy or the component. In sum, an electrochemically driven dissolution process can be tailored to remove of the recast contamination without affecting the integrity of the host component structure and its dimensional tolerances.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS1989

High performance alloy electroforming

Electroformed copper and nickel are used in structural applications for advanced propellant combustion chambers. An improved process has been developed by Bell Aerospace Textron, Inc. wherein electroformed nickel-manganese alloy has demonstrated superior mechanical and thermal stability when compared to previously reported deposits from known nickel plating processes. Solution chemistry and parametric operating procedures are now established and material property data is established for deposition of thick, large complex shapes such as the Space Shuttle Main Engine. The critical operating variables are those governing the ratio of codeposited nickel and manganese. The deposition uniformity which in turn affects the manganese concentration distribution is affected by solution resistance and geometric effects as well as solution agitation. The manganese concentration in the deposit must be between 2000 and 3000 ppm for optimum physical properties to be realized. The study also includes data regarding deposition procedures for achieving excellent bond strength at an interface with copper, nickel-manganese or INCONEL 718. Applications for this electroformed material include fabrication of complex or re-entry shapes which would be difficult or impossible to form from high strength alloys such as INCONEL 718.

Malone, G. A.↗

DOE OSTI2022

Redox chemistry of plutonium and plutonium surrogates in vitrified nuclear wastes

Lanthanide borosilicate glasses containing Pu and the analog element, Ce, were subjects of an X-ray absorption spectroscopy investigation to quantify the +3/+4 ratio of the redox-sensitive element. The data show that the dominant oxidation states are +4 for Pu and +3 for Ce. The data also indicate that the reductive potential of glasses can be quantified, although allowances must be made for glass composition, from a solution chemistry method adapted to glass chemistry. These data can therefore be used to formulate glass compositions and processing schedules that lead to knowledge of the oxidation state of Pu in melts. Furthermore, the data show that Ce is a poor analog for Pu behavior in melt and that the suitability of surrogates can be evaluated by this method. The methods demonstrated in this paper can be used to estimate the oxidation states of a range of multi-valent elements as functions of temperature and composition with data from only a single redox couple.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗

DOE OSTI2021

Uptake of aqueous heavy metal ions (Co2+, Cu2+ and Zn2+) by calcium-aluminium-silicate-hydrate gels

Highlights: • C-A-S-H gels containing metal ions (Co{sup 2+}, Cu{sup 2+} or Zn{sup 2+}) were precipitated by a sol-gel technique. • Uptake mechanism and immobilization capacity of divalent metal ions by C-A-S-H are elucidated. • Up to ~55–60 mol% of Zn can be incorporated in defective tobermorite-type C-A-S-H. • Metal uptake by C-A-S-H is controlled mainly by isomorphous substitution for Ca ions. • Crystal-chemical features of C-A-S-H gels and implications for practical application are discussed. Calcium-aluminium-silicate-hydrate (C-A-S-H) gels containing heavy metal ions (Me: Co{sup 2+}, Cu{sup 2+} or Zn{sup 2+}) were precipitated at different Me/Si molar ratios to study the uptake mechanism and immobilization capacity. Aqueous solution chemistry and solid-phase characterization using XRD, FTIR, ESEM-EDX, TEM-HAADF and TG-DSC methods reveal threshold values for ion substitution of ~55–60 mol% for Zn, ~30–40 mol% for Co and ~25–30 mol% for Cu in defective tobermorite-type C-A-S-H with (Ca + Me)/(Si + Al) molar ratios from 0.86 to 1.04. At higher aqueous Me concentrations, Me (chloride) hydroxides start to co-precipitate. The uptake mechanism of Me ions by C-A-S-H is based on (i) isomorphous substitution of Me for Ca in the CaO layer, (ii) ion exchange in the interlayer, (iii) tetrahedral substitution (Zn) within the dreierketten chains and (iv) surface adsorption onto the C-A-S-H gel structure. Systematics in crystal-chemistry of Me-bearing C-A-S-H and implications for application and performance in natural and man-made settings are discussed.

36 MATERIALS SCIENCE↗

DOE OSTI2025

Non-stoichiometry Governs the Pathway from Amorphous to Crystalline Calcium Carbonate

The controlled crystallization of calcium carbonate underlies the elaborate architectures of marine corals, the design of biomimetic materials, and the global carbon cycle. Despite its ubiquity, the chemical mechanisms that govern the crystallization of calcium carbonate from its amorphous precursor, amorphous calcium carbonate (ACC), remain elusive, largely due to the difficulty in resolving the structure and chemistry of this transient amorphous state. Here, we use time-lapse photography, image analysis, spatially resolved pH determination, in situ synchrotron pair distribution function (PDF) analysis, and dynamic nuclear polarization (DNP) solid-state nuclear magnetic resonance (NMR) spectroscopy to reveal pervasive compositional variability in ACC that underpins its metastability and crystallization. By evaluating the kinetics of the amorphous-to-crystalline transition across different solution chemistries, we demonstrate that ACC is non-stoichiometric and CO 3 -deficient. Counterions from the precursor (e.g., NO 3 - from Ca(NO 3 ) 2 ) substitute into the ACC network, displacing CO 3 ions and mediating both ACC stability and transformation. Crystallization proceeds through refinement of the stoichiometry toward CaCO 3 and uptake of free CO 3 2- anions. Furthermore, these findings are consistent across a wide range of concentrations and different carbonate sources, explaining the diverse behaviors observed for ACC and providing a chemical framework for controlling calcium carbonate crystallization.

77 NANOSCIENCE AND NANOTECHNOLOGY↗

DOE OSTI2023

Amine-Thiol/Selenol Chemistry for Efficient and Stable Perovskite Solar Cells

Controlling the crystallization of perovskites is imperative to reduce defect densities in perovskite thin films and extend device lifetimes. In this work, combinations of amine and chalcogenide ligands were introduced in the sequential deposition method to fabricate highly crystalline and orientated formamidinium lead iodide thin films with reduced defect densities and increased charge carrier lifetimes. The dual additives can tune the perovskite intermediate state and control the crystallization leading to devices with improved efficiencies and stabilities. While thiophenol failed to prevent the amine ligand from degrading the perovskite precursors, benzene selenol combinations with amine-ligands drastically changed the solution chemistry to increase the PbI 2 conversion to highly crystalline and orientated α-FAPbI 3 films with lower defect densities. X-ray photoelectron spectroscopy studies reveal benzene selenol evaporates from the thin film leaving behind a modified surface, which is associated with the amine additive. These results indicate the amine selection can be used to tune the surface properties. Lastly, we propose a highly tunable I 2 reduction strategy using chalcogenide chemistry to help enable the realization of perovskite solar cells with high performance and stability.

defects↗

DOE OSTI2021

Modeling of aqueous species interaction energies prior to nucleation in cement-based gel systems

Arguably the most ubiquitous construction material in modern civilization, concrete is enabling the development of megacities around the globe together with increasing living standards in developing nations. However, the exact formation mechanisms of the strength-giving calcium-rich gels remain a topic of debate. Using density functional modeling, we simulate the fundamental solution-based building blocks of cement hydrates (calcium ions and silicate and aluminate monomers) and their propensity to form pair-wise complexes with bonding environments characteristic of those found in calcium-silicate-hydrate, calcium-alumino-silicate-hydrate and sodium-containing calcium-alumino-silicate-hydrate gels, as assessed from Gibbs free energies of chemical reactions. By accurately simulating the high pH pore solution chemistry in Portland cements and related systems, along with discrete solvation of the species, we hypothesize potential early age formation routes of the gels and discuss limitations and future work associated with this approach.

36 MATERIALS SCIENCE↗

DOE OSTI2020

An Overview of Nanomaterials for Environmental Remediation Applications

The environmental remediation capabilities of nanoparticles were reviewed and evaluated. Nanoparticles (NPs) have been used to remediate various forms of environmental contamination. Various materials, morphologies, and conditions are required to remediate different contaminants. Nanoparticles may have benefits and/or limitations compared with traditional remediation methods. New techniques are being applied to mitigate the limitations of NPs. Nanomaterials are a promising technology for the environmental remediation. NPs have been used for the remediation of aqueous and atmospheric contaminants. Nanoparticles have been used to sequester contaminants toxic to human and environmental health. Various materials, morphologies, and conditions are necessary for the remediation of different contaminants. The remediation of heavy metals is of significant concern. Contaminants may be remediated by means of sorption or reduction. The remediation capability of nanoparticles is promising due to their high surface area and reactivity. Reaction kinetics are, therefore, notably fast. These characteristics make NPs attractive for environmental remediation. Various NPs have been used as sequestering agents for environmental contaminants. NPs have been used to remediate heavy metals as well as organic contaminants. Technical Objectives: Assess viability of nanoparticles (NPs) for environmental remediation; Review benefits and limitations of NPs; Design future experiments to test remediation capabilities of NPs. Future Plans: Create NP filters for remediation - Grow Au NPs on Stainless Steel Wool: Stainless steel wool has many defects and crevices allowing the Au NPs to grow on the surface; Stainless steel wool will not react with the heavy metal contaminants tested; NPs are embedded, so they do not have to be removed from solution. Test sorption capabilities with heavy metal contaminants in aqueous solution. Benefits of Gold NPs: Corrosion/oxidation resistant; Exhibit visible/near IR plasmon resonance; Can be synthesized by solution chemistry: cost efficient and easily scalable. Surfactants: Used to lower surface energy and prevent aggregation; Sodium citrate: anionic surfactant (-); Cetyltrimethylammonium bromide (CTAB): cationic surfactant (+); Ionic surfactants create charged NPs; Charged NPs can be used to sequester ionic contaminants (eg. heavy metals)

54 ENVIRONMENTAL SCIENCES↗

NASA NTRS2006

Lab-Scale Study of the Calcium Carbonate Dissolution and Deposition by Marine Cyanobacterium Phormidium subcapitatum

Suggestions that calcification in marine organisms changes in response to global variations in seawater chemistry continue to be advanced (Wilkinson, 1979; Degens et al. 1985; Kazmierczak et al. 1986; R. Riding 1992). However, the effect of [Na+] on calcification in marine cyanobacteria has not been discussed in detail although [Na+] fluctuations reflect both temperature and sea-level fluctuations. The goal of these lab-scale studies therefore was to study the effect of environmental pH and [Na+] on CaCO3 deposition and dissolution by marine cyanobacterium Phormidium subcapitatum. Marine cyanobacterium P. subcapitatum has been cultivated in ASN-III medium. [Ca2+] fluctuations were monitored with Ca(2+) probe. Na(+) concentrations were determined by the initial solution chemistry. It was found that the balance between CaCO3 dissolution and precipitation induced by P. subcapitatum grown in neutral ASN III medium is very close to zero. No CaCO3 precipitation induced by cyanobacterial growth occurred. Growth of P. subcapitatum in alkaline ASN III medium, however, was accompanied by significant oscillations in free Ca(2+) concentration within a Na(+) concentration range of 50-400 mM. Calcium carbonate precipitation occurred during the log phase of P. subcapitatum growth while carbonate dissolution was typical for the stationary phase of P. subcapitatum growth. The highest CaCO3 deposition was observed in the range of Na(+) concentrations between 200-400 mM. Alkaline pH also induced the clamping of P. subcapitatum filaments, which appeared to have a strong affinity to envelop particles of chemically deposited CaCO3 followed by enlargement of those particles size. EDS analysis revealed the presence of Mg-rich carbonate (or magnesium calcite) in the solution containing 10-100 mM Na(+); calcite in the solution containing 200 mM Na(+); and aragonite in the solution containing with 400 mM Na(+). Typical present-day seawater contains xxmM Na(+). Early (Archean) seawater was likely less saline. The division of marine cyanobacterium P. subcapitatum is associated with periodic deposition and dissolution of CaCO3, the rhythms and intensity of which are dependent on concentrations of both OH(-) and Na(+). Thus, the role of present-day marine cyanobacteria in the global carbonate cycle might be reduced to aggregation and recrystallization of available CaCO3 particles in marine water rather than long-term precipitation and accumulation of CaCO3 deposits. For lower Na(+) concentrations, precipitation of carbonates by cyanobacteria would be even less significant. These results suggest that the lack of calcified cyanobacteria in stromatalite-bearing Precambrian sequences can be explained not only by high dissolved inorganic carbon concentrations but also by lower salinity, as well as possible lower pH compared to present-day oceans.

Karakis, S. G.↗

NASA NTRS1996

Aerothermodynamic Analysis of Commercial Experiment Transporter (COMET) Reentry Capsule

An aerothermodynamic analysis of the Commercial Experiment Transporter (COMET) reentry capsule has been performed using the laminar thin-layer Navier-Stokes solver Langley Aerothermodynamic Upwind Relaxation Algorithm. Flowfield solutions were obtained at Mach numbers 1.5, 2, 5, 10, 15, 20, 25, and 27.5. Axisymmetric and 5, 10, and 20 degree angles of attack were considered across the Mach-number range, with the Mach 25 conditions taken to 90 degrees angle of attack and the Mach 27.5 cases taken to 60 degrees angle of attack. Detailed surface heat-transfer rates were computed at Mach 20 and 25, revealing that heating rates on the heat-shield shoulder ,can exceed the stagnation-point heating by 230 percent. Finite-rate chemistry solutions were performed above Mach 10, otherwise perfect gas computations were made. Drag, lift, and pitching moment coefficients are computed and details of a wake flow are presented. The effect of including the wake in the solution domain was investigated and base pressure corrections to forebody drag coefficients were numerically determined for the lower Mach numbers. Pitching moment comparisons are made with direct simulation Monte Carlo results in the more rarefied flow at the highest Mach numbers, showing agreement within two-percent. Thin-layer Navier-Stokes computations of the axial force are found to be 15 percent higher across the speed range than the empirical/Newtonian based results used during the initial trajectory analyses.

Wood, William A.↗

DOE OSTI2022

Contrasting Trivalent Lanthanide and Actinide Complexation by Polyoxometalates via Solution-State NMR

Deciphering the solution chemistry and speciation of actinides is inherently difficult due to radioactivity, rarity, and cost constraints, especially for transplutonium elements. In this context, the development of new chelating platforms for actinides and associated spectroscopic techniques is particularly important. In this study, we investigate a relatively overlooked class of chelators for actinide binding, namely, polyoxometalates (POMs). We provide the first NMR measurements on americium–POM and curium–POM complexes, using one-dimensional (1D) 31 P NMR, variable-temperature NMR, and spin-lattice relaxation time (T 1 ) experiments. The proposed POM–NMR approach allows for the study of trivalent f-elements even when only microgram amounts are available and in phosphate-containing solutions where f-elements are typically insoluble. The solution-state speciation of trivalent americium, curium, plus multiple lanthanide ions (La 3+ , Nd 3+ , Sm 3+ , Eu 3+ , Yb 3+ , and Lu 3+ ), in the presence of the model POM ligand PW 11 O 39 7– was elucidated and revealed the concurrent formation of two stable complexes, [M III (PW 11 O 39 )(H 2 O) x ] 4– and [M III (PW 11 O 39 ) 2 ] 11– . Interconversion reaction constants, reaction enthalpies, and reaction entropies were derived from the NMR data. The NMR results also provide experimental evidence of the weakly paramagnetic nature of the Am 3+ and Cm 3+ ions in solution. Furthermore, the study reveals a previously unnoticed periodicity break along the f-element series with the reversal of T 1 relaxation times of the 1:1 and 1:2 complexes and the preferential formation of the long T 1 species for the early lanthanides versus the short T 1 species for the late lanthanides, americium, and curium. Furthermore, given the broad variety of POM ligands that exist, with many of them containing NMR-active nuclei, the combined POM–NMR approach reported here opens a new avenue to investigate difficult-to-study elements such as heavy actinides and other radionuclides.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS2003

Crystallization Physics in Biomacromolecular Systems

The crystals are built of molecules of protein, nucleic acid and their complexes, like viruses, approx. 5x10(exp 3)+ 3x10(exp 6) Da in weight and 2 + 20 nm in effective diameter. This size strongly exceeds action range of molecular forces and makes a big difference with inorganic crystals. Intermolecular contacts form patches on the biomacromolecular surface. Each patch may occupy only a small percent of the whole surface and vary from polymorph to polymorph of the same protein. Thus, under different conditions (pH, solution chemistry, temperature, any area on the macromolecular surface may form a contact. The crystal Young moduli, E approx. equals 0.1 + 0.5 GPa are more than 10 times lower than that of inorganics and the biomolecules themselves. Water within biocrystals (30-70%) is unable to flow unless typical deformation time is longer than approx. 10(exp -5)s. This explains the discrepancy between light scattering and static measurements of E. Nucleation and Growth requires typically concentrations exceeding the equilibrium ones up to 100 times - because of the new size scale results in 10 - 10(exp 3) times lower kinetic coefficients than that needed for inorganic solution growth. All phenomena observed in the latter occur with protein crystallization and are even better studied by AFM. Crystals are typically facetted. Among unexpected findings of general significance are - net molecular exchange flux at kinks is much lower than that expected from supersaturation, steps with low (< approx. 10(exp -2)) kink density at steps follow Gibbs-Thomson law only at very low supersaturations, step segment growth rate may be independent of step energy. Crystal perfection is a must of biocrystallization to achieve the major goal to find 3-D atomic structure of biomacromolecules by x-ray diffraction. Poor diffraction resolution (> 3Angstrom) makes crystallization a bottleneck for structural biology. All defects typical of small molecule crystals are found in biocrystals, but the defects responsible for poor resolution are not identified. Conformational changes are one of them. Biocrystallization in microgravity reportedly results in 20% cases of better crystals. The mechanism of how lack of convection can do this is still not clear. Lower supersaturation, self-purification &om preferentially trapped homologous impurities and step bunching are viable hypotheses.

Chernov, A. A.↗

DOE OSTI2024

Sulfide precipitation characteristics of Mn, Ni, Co, and Zn in the presence of contaminant metal ions

In this study, the effects of Al 3+ and Fe 2+ on the precipitation characteristics of four valuable metals, including Mn 2+ , Ni 2+ , Co 2+ , and Zn 2+ , were investigated by conducting solution chemistry calculations, sulfide precipitation tests, and mineralogy characterizations. It was found that the ability of the valuable metals to form sulfide precipitates followed an order of Zn 2+ > Ni 2+ > Co 2+ > Mn 2+ . The sulfide precipitate of Zn 2+ was the most stable and did not re-dissolve under the acidic condition (pH 4.00 ± 0.05). In addition, the sulfide precipitation characteristics of Zn 2+ was barely affected by the contaminant metal ions. However, in the presence of Al 3+ , the precipitation recoveries of Mn 2+ , Ni 2+ , and Co 2+ were noticeably reduced due to simultaneous hydrolysis and competitive adsorption. The precipitation recoveries of Ni 2+ and Co 2+ in solutions containing individual valuable metals also reduced when Fe 2+ was present, primarily due to competitive precipitation. However, the recovery of Mn 2+ was enhanced due to the formation of ferrous sulfide precipitate, providing abundant active adsorption sites for Mn species. Here, in the solution containing all the valuable metals, Fe 2+ promoted the recovery of the valuable metals due to the higher concentration of Na 2 S and the formation of ferrous sulfide precipitate.

58 GEOSCIENCES↗

DOE OSTI2023

Predicting Outcomes of Nanoparticle Attachment by Connecting Atomistic, Interfacial, Particle, and Aggregate Scales

Predicting nanoparticle aggregation and attachment phenomena requires a rigorous understanding of the interplay among crystal structure, particle morphology, surface chemistry, solution conditions, and interparticle forces, yet no comprehensive picture exists. We used an integrated suite of experimental, theoretical, and simulation methods to resolve the effect of solution pH on the aggregation of boehmite nanoplatelets, a case study with important implications for the environmental management of legacy nuclear waste. Real-time observations showed that the particles attach preferentially along the (010) planes at pH 8.5 and the (101) planes at pH 11. To rationalize these results, we established the connection between key physicochemical phenomena across the relevant length scales. Starting from molecular-scale simulations of surface hydroxyl reactivity, we developed an interfacial-scale model of the corresponding electrostatic potentials, with subsequent particle-scale calculations of the resulting driving forces allowing successful prediction of the attachment modes. Finally, we scaled these phenomena to understand the collective structure at the aggregate-scale . Here, our results indicate that facet-specific differences in surface chemistry produce heterogeneous surface charge distributions that are coupled to particle anisotropy and shape-dependent hydrodynamic forces, to play a key role in controlling aggregation behavior.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2023

MacroSheds: A synthesis of long-term biogeochemical, hydroclimatic, and geospatial data from small watershed ecosystem studies

The US Federal Government supports hundreds of watershed monitoring efforts from which solute fluxes can be calculated. Although instrumentation and methods vary between studies, the data collected and their motivating questions are remarkably similar. Nevertheless, little effort toward their compilation has previously been made. The MacroSheds project has developed a future-friendly system for harmonizing daily time series of streamflow, precipitation, and solute chemistry from 169+ watersheds, and supplementing each with watershed attributes. Here, we describe the breadth of MacroSheds data, and detail the steps involved in rendering each data product. We provide recommendations for usage and discuss when other datasets might be more suitable. The MacroSheds dataset is an unprecedented resource for watershed science, and for hydrology, as a small-watershed supplement to existing collections of streamflow predictors, like CAMELS and GAGES-II. The MacroSheds platform includes a web dashboard for visualization and an R package for data access and analysis.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2022

Plasma-induced inactivation of Staphylococcus aureus biofilms: The role of atomic oxygen and comparison with disinfectants and antibiotics

Microbial biofilms are of critical concern because of their recalcitrance to antimicrobials. Cold atmospheric plasmas (CAP) represent a promising biofilm remediation strategy as they generate reactive oxygen and nitrogen species (RONS), but mechanisms underpinning CAP-biofilm interactions remain unknown. We assess the impact of treatment modality on biofilm inactivation and show that CAP killing of Staphylococcus aureus biofilms is dependent on treatment conditions, including solution chemistry. In dry treatments, biofilms are locally ablated due to plasma-produced O flux. For saline-submerged biofilms, while we show that ClO – is generated at high concentrations in larger treatment volumes, CAP inactivation at low ClO – concentrations implicates other reaction pathways. Finally, we demonstrate CAP efficacy over conventional antimicrobials, underscoring its promise as a biofilm treatment approach.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2021

Predicting Low Toxicity and Scalable Solvent Systems for High–Speed Roll–to–Roll Perovskite Manufacturing

Printed lead-based perovskite photovoltaics (PV) have gained interest due to their potential to be manufactured with scalable roll-to-roll techniques. In industrial scale-up, toxicity of inks can constrain roll-to-roll manufacturing due to the added cost of managing toxic effluents. Due to solvent toxicity, few perovskite solution chemistries in published works are scalable to gigawatt production capacity at low cost. Herein, it is shown that for scalable PV production, the use of aprotic polar solvents should be avoided due to their overall toxicity. Compliance with worldwide worker safety regulations for solvent exposure limits could require additional air handling requirements for some solvents, which in turn would affect cost-effectiveness. It is shown that costs associated with handling of hazardous substances can be significant and estimate an added cost of ¢3.7/W for dimethylformamide (DMF)-based inks. To solve this problem, a new perovskite ink solvent system is developed that is composed entirely of ether and alcohol, which has an effective exposure limit 14× higher than DMF, making it suitable for industrial coating processes. Here, it is shown that the new ink solvent system is capable of fabricating high-efficiency perovskite solar cells processed in 1 min on a standard roll-to-roll system.

36 MATERIALS SCIENCE↗