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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Targeted Adjusting Molecular Arrangement in Organic Solar Cells via a Universal Solid Additive

The incorporation of solid additive has been considered as an effective strategy for developing organic photovoltaics with multi-components, which is independent of dynamics, playing unique roles in morphology adjustment. However, their complex working mechanisms involving specific chemical structures are selective to material systems, hence limiting their university and flexibility in application. Herein, an inert small-molecular compound naphtho[1,2-c:5,6-c′]bis[1,2,5]thiadiazole (NT) is introduced into the bulk-heterojunction blend as the solid additive, which can function with various material systems and solvents, depending on its simple π-conjugated structure and S⋯N interaction for adjusting molecular alignment. It is interesting to note that the introduced NT can not only improve device performance, but also simplify complicated pre- or post-processing methods, reduce impact from batch-to-batch differences, construct sufficient energy transfer channel as well as improve device stability. The resulting devices based on PTzBI-dF:Y6-BO system show an impressive power conversion efficiency of 17.4% with obviously enhanced T 80 lifetime of >1200 h. These findings provide useful guidelines for exploring potential universal solid additives benefitting toward commercial application.

36 MATERIALS SCIENCE↗
DOE OSTI2024

A Pseudo Planar Heterojunction Structure for Eco‐Friendly Printable Organic Solar Cells Achieving 19.05% Efficiency

Abstract Obtaining a well‐accurate vertical distribution active layer morphology through the air‐printing process is an essential task for achieving efficient scalable large‐area organic solar cells (OSCs). In this target, the desired and controllable pseudo planar heterojunction (PPHJ) active layer structure with suitable phase separation is developed by pre‐deposited D18‐Cl layer under the PM6:BTP‐eC9 film via an eco‐friendly manufacturing method. The addition of the D18‐Cl regulates molecular crystallization and leads to an ideal vertical stratification while simultaneously suppressing voltage loss, optimizing energetic disorder, and carrier management. Impressively, the optimal PPHJ devices perform superior power conversion efficiencies (PCEs) of 19.05% (100 nm), 17.33% (300 nm), and 14.14% (4 cm 2 ) compared to the BHJ devices. Importantly, the PPHJ OSCs also exhibit an impressive extrapolated T 80 (the time required to reach 80% of initial PCE) of long‐time storage and operational stability, as well as thermal stability.

Chemistry↗
DOE OSTI2021

Synthesis and Photophysical Properties of Light-Harvesting Gold Nanoclusters Fully Functionalized with Antenna Chromophores

The development of efficient light-harvesting systems is important to understand the key aspects of solar-energy conversion processes and to utilize them in various photonic applications. In this study, atomically well-defined gold nanoclusters are reported as a new platform to fabricate artificial light-harvesting systems. An efficient amide coupling method is developed to synthesize water-soluble Au 22 clusters fully protected with pyrene chromophores by taking advantage of their facile phase-transfer reaction. The synthesized Au 22 clusters with densely packed 18 pyrene chromophores (Au 22 –PyB 18 ) exhibit triple-emission in blue, green, and red wavelength regions arising respectively from pyrene monomer, pyrene excimer, and Au 22 emission, producing bright white light emission together. The photoluminescence of Au 22 is enhanced by more than tenfold, demonstrating that pyrenes at the periphery efficiently channel the absorbed energy to the luminescent Au 22 at the center. A combination of femtosecond transient absorption and anisotropy measurements of Au 22 –PyB 18 explicitly reveals three main decay components of 220 fs, 3.5 ps, and 160 ps that can be assigned to energy migration between pyrenes and energy transfer processes from pyrene monomer and excimer to the central Au 22 , respectively.

14 SOLAR ENERGY↗
DOE OSTI2025

Predicting the evolution of biomass bulk density through feedstock preprocessing: Discrete element modeling, regression analysis, and pilot-scale validation

Bulk density is an important material property of biomass feedstocks, influencing handling, storage, transport costs, and conversion efficiency. In this study, predictive regression models for loose and tapped bulk densities of Alamo and Cave-in-Rock switchgrass are developed using a comprehensive dataset generated via calibrated bonded-sphere discrete element method (DEM) simulations. Here, a key contribution of this study is the use of a DEM-based approach, which correlates density with moisture content and particle size distribution parameters and enables analysis across a continuous particle size range, overcoming limitations of purely experimental data. For comparison, regression models are also developed using only experimental data from pilot-scale runs at the Biomass Feedstock National User Facility at Idaho National Laboratory. Validation against pilot-scale data showed reasonable prediction accuracy for both model types, particularly for smaller particle sizes (post-secondary grinding). While the experimental model showed slightly better performance matching the validation data in some cases, the DEM-based model benefits from a much larger dataset, reduced predictor multicollinearity, and continuous parameter coverage, highlighting the utility of validated simulation models for developing robust predictive tools for biomass preprocessing applications.

09 - BIOMASS FUELS↗
DOE OSTI2016

Efficient Colorful Perovskite Solar Cells Using a Top Polymer Electrode Simultaneously as Spectrally Selective Antireflection Coating

Organometal halide perovskites have demonstrated excellent optoelectronic properties and have been used to demonstrate a variety of semiconductor devices. Colorful solar cells are desirable for photovoltaic integration in buildings and other aesthetically appealing applications. Yet, the realization of colorful perovskite solar cells is challenging because of their broad and large absorption coefficient that commonly leads to cells with dark-brown colors. Herein, for the first time, we report a simple and efficient strategy to achieve colorful perovskite solar cells by using the transparent conducting polymer (poly(3,4-ethylenedioxythiophene):poly- (styrenesulfonate), PEDOT:PSS) as a top electrode and simultaneously as an spectrally selective antireflection coating. Vivid colors across the visible spectrum are attained by engineering optical interference effects among the transparent PEDOT:PSS polymer electrode, the hole-transporting layer and the perovskite layer. The colored perovskite solar cells display power conversion efficiency values from 12.8 to 15.1% (from red to blue) when illuminated from the FTO glass side and from 11.6 to 13.8% (from red to blue) when illuminated from the PEDOT:PSS side. The new method offers an advanced solution for fabricating colorful perovskite solar cells with easy processing and high efficiency.

42 ENGINEERING↗
DOE OSTI2019

Thienopyrroledione-Based Photosensitizers as Strong Photoinduced Oxidants: Oxidation of Fe(bpy) 3 2+ in a >1.3 V Dye-Sensitized Solar Cell

The creation of visible light absorbing organic dyes as strong photoinduced oxidants is needed for many potential applications in energy production and storage. In order to access more positive potentials, the electron deficient thienopyrroledione building block is promising as a π-bridge combined with weak aryl-ether donor groups and the phenyl-cyanoacetic acid acceptor group. The thienopyrroledione (TPD) building block is compared to the ubiquitous benzothiadiazole (BTD) building block which was recently used in a dye-sensitized solar cell (DSC) device with >1.4 V photovoltage output. The variation in dye donor group is studied through UV-Vis absorption spectroscopy and electrochemical methods both in solution and on TiO2 films. The TPD building block resulted in a more positive ground state and excited state oxidation potential, a higher photocurrent (up to 3.5 mA/cm 2 ), and a higher power conversion efficiency (up to 2.9%) than a BTD analogue while retaining comparable photovoltages (~1.3 V versus ~1.4 V). Computational analysis was used to better understand the optical properties of the thienopyrroledione-based dyes showing overlap of orbitals at the TPD bridge in the S 0 and S 1 states. The dyes were analyzed in high voltage-DSC devices with a challenging to oxidize redox shuttle, [Fe(bpy) 3 ] 2+ , at 1.37 V versus NHE.

25 ENERGY STORAGE↗
DOE OSTI2016

Computationally Exploring Confinement Effects in the Methane-to-Methanol Conversion Over Iron-Oxo Centers in Zeolites

Transition metal-oxo centers in zeolites are known to be active in the conversion of methane to methanol. In this work, we examine this reaction over Fe-oxo sites in the zeolite SSZ-13. By comparing calculations for the fully periodic structure and a cluster for two different methods—the standard van der Waals corrected semilocal density functional PBE-D2 and ACFDT-RPA, which is a method where correlation is calculated fully nonlocally—we find that it is actually the confining environment in the zeolite that reduces the barrier for this reaction, by more than 50%, and we find that the two applied methods lead to qualitatively different ends.

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

Ultrafast Photoflash Synthesis of High-Entropy Oxide Nanoparticles

High-entropy metal oxides (HEOs) have recently received growing attention for broad energy conversion and storage applications due to their tunable properties. HEOs typically involve the combination of multiple metal cations in a single oxide lattice, thus bringing distinctive structures, controllable elemental composition, and tunable functional properties. Many synthesis methods for HEOs have been reported, such as solid-state reactions and carbon thermal shock methods. These methods frequently are energy-intensive or require relatively expensive heating equipment. In this work, we report an ultrafast photoflash synthesis method for HEO nanoparticles on diverse substrates. The energy input is provided by a commercial Xe photoflash unit, which triggers exothermic reactions to convert metal salt precursors to HEO nanoparticles within tens of milliseconds. The formation of HEO nanoparticles is attributed to the ultrafast heating (∼106 K/s) and cooling (∼105 K/s) rates of the photoflash and overall high temperature (>1000 K) during the ultrafast synthesis process. When the synthesized CoNiFeCrMn oxide (HEO) is tested as an oxygen evolution reaction electrocatalyst, it shows similar activity to similar materials prepared by other methods. We believe this photoflash synthesis provides a simple method for many others to synthesize diverse HEOs and explore their properties and potential applications.

exothermic reaction synthesis↗
DOE OSTI2016

Numerical investigation of non-perturbative kinetic effects of energetic particles on toroidicity-induced Alfvén eigenmodes in tokamaks and stellarators

The resonant interaction of shear Alfvén waves with energetic particles is investigated numerically in tokamak and stellarator geometry using a non-perturbative MHD-kinetic hybrid approach. The focus lies on toroidicity-induced Alfvén eigenmodes (TAEs), which are most easily destabilized by a fast-particle population in fusion plasmas. While the background plasma is treated within the framework of an ideal-MHD theory, the drive of the fast particles, as well as Landau damping of the background plasma, is modelled using the drift-kinetic Vlasov equation without collisions. Building on analytical theory, a fast numerical tool, STAE-K, has been developed to solve the resulting eigenvalue problem using a Riccati shooting method. The code, which can be used for parameter scans, is applied to tokamaks and the stellarator Wendelstein 7-X. High energetic-ion pressure leads to large growth rates of the TAEs and to their conversion into kinetically modified TAEs and kinetic Alfvén waves via continuum interaction. To better understand the physics of this conversion mechanism, the connections between TAEs and the shear Alfvén wave continuum are examined. It is shown that, when energetic particles are present, the continuum deforms substantially and the TAE frequency can leave the continuum gap. The interaction of the TAE with the continuum leads to singularities in the eigenfunctions. To further advance the physical model and also to eliminate the MHD continuum together with the singularities in the eigenfunctions, a fourth-order term connected to radiative damping has been included. The radiative damping term is connected to non-ideal effects of the bulk plasma and introduces higher-order derivatives to the model. Thus, it has the potential to substantially change the nature of the solution. For the first time, the fast-particle drive, Landau damping, continuum damping, and radiative damping have been modelled together in tokamak- as well as in stellarator geometry.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

Theory, observations, and simulations of kinetic entropy in a magnetotail electron diffusion region

In this work, we examine velocity-space kinetic entropy, a spatially local measure of entropy for systems out of thermal equilibrium, during an encounter of an electron diffusion region at a magnetic reconnection site in Earth’s magnetotail by the Magnetospheric Multiscale (MMS) mission. We start by generalizing the theory of kinetic entropy to the case of non-uniform velocity space grids and transforming the equations into spheri- cal energy coordinates useful to experimental plasma detectors. The theory is then applied to MMS data and compared to particle-in-cell simulations of reconnection. We demonstrate that the entropy-based non-Maxwellianity measure from the MMS data is of sufficiently high precision to reliably identify non-Maxwellian distributions and therefore the measurements when kinetic effects are most significant. By comparing two different non-Maxwellian measures, we show that total entropy density suffers from “information loss” because it lacks a dependence on the velocity space grid, and so has lost information about how well a distribution function is resolved. Local velocity-space kinetic entropy density recovers this information. We quantify information loss and argue that the considerations needed to minimize it are crucial for instruments designed to measure distribution functions in situ.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Excitons: Energetics and spatiotemporal dynamics

The concept of an exciton as a quasiparticle that represents collective excited states was originally adapted from solid-state physics and has been successfully applied to molecular aggregates by relying on the well-established limits of the Wannier exciton and the Frenkel exciton. However, the study of excitons in more complex chemical systems and solid materials over the past two decades has made it clear that simple concepts based on Wannier or Frenkel excitons are not sufficient to describe detailed excitonic behavior, especially in nano-structured solid materials, multichromophoric macromolecules, and complex molecular aggregates. In addition, important effects such as vibronic coupling, the influence of charge-transfer (CT) components, spin-state interconversion, and electronic correlation, which had long been studied but not fully understood, have turned out to play a central role in many systems. This has motivated new experimental approaches and theoretical studies of increasing sophistication. This article provides an overview of works addressing these issues that were published for A Special Topic of the Journal of Chemical Physics on ``Excitons: Energetics and spatio-temporal dynamics" and discusses their implications.

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

Rapid Analysis of Inorganic Species in Herbaceous Materials Using Laser-Induced Breakdown Spectroscopy [plus supplemental information]

Inorganic compounds in biomass, often referred to as ash, are known to be problematic in the thermochemical conversion of biomass to bio-oil or syngas and, ultimately, hydrocarbon fuels because they negatively influence reaction pathways, contribute to fouling and corrosion, poison catalysts, and impact waste streams. The most common ash-analysis methods, such as inductively coupled plasma-optical emission spectrometry/mass spectrometry (ICP-OES/MS), require considerable time and expensive reagents. Laser-induced breakdown spectroscopy (LIBS) is emerging as a technique for rapid analysis of the inorganic constituents in a wide range of biomass materials. This study compares analytical results using LIBS data to results obtained from three separate ICP-OES/MS methods for 12 samples, including six standard reference materials. Analyzed elements include aluminum, calcium, iron, magnesium, manganese, phosphorus, potassium, sodium, and silicon, and results show that concentrations can be measured with an uncertainty of approximately 100 parts per million using univariate calibration models and relatively few calibration samples. These results indicate that the accuracy of LIBS is comparable to that of ICP-OES methods and indicate that some acid-digestion methods for ICP-OES may not be reliable for Na and Al. These results also demonstrate that germanium can be used as an internal standard to improve the reliability and accuracy of measuring many elements of interest, and that LIBS can be used for rapid determination of total ash in biomass samples. Key benefits of LIBS include little sample preparation, no reagent consumption, and the generation of meaningful analytical data instantaneously.

09 BIOMASS FUELS↗
DOE OSTI2024

Thermoelectric properties of SnSe and SnSe 2 single crystals

Thermoelectric materials can serve for conversion between thermal and electrical energy. In the search for new thermoelectric materials, layered SnSe and SnSe 2 are promising candidates. Here we have successfully synthesized SnSe and SnSe 2 single crystals by the modified Bridgman method and studied their thermoelectric properties: thermopower (S), thermal conductivity (κ), and electrical conductivity (σ) in the temperature range between 2 K and 400 K, which are absent in the literature. In particular, the kink observed in the thermopower corresponds to the metallic-nonmetallic crossover temperature for both SnSe and SnSe 2 , reflecting their inherent electronic nature. Compared to SnSe 2 above 100 K, we find that SnSe exhibits higher electrical conductivity, higher thermopower, and lower thermal conductivity, thus resulting in the higher figure of merit. Hall effect measurements reveal that the Hall mobility in SnSe is an order higher than that in SnSe 2 , advancing its thermoelectric performance. These experimental results are supported by first principles calculations, which indicate that the inequivalent Sn-Se bonding lengths help improve the figure of merit of SnSe.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Cyclization strategies of meditopes: affinity and diffraction studies of meditope–Fab complexes

An overview of cyclization strategies of a Fab-binding peptide to maximize affinity. Recently, a unique binding site for a cyclic 12-residue peptide was discovered within a cavity formed by the light and heavy chains of the cetuximab Fab domain. In order to better understand the interactions that drive this unique complex, a number of variants including the residues within the meditope peptide and the antibody, as well as the cyclization region of the meditope peptide, were created. Here, multiple crystal structures of meditope peptides incorporating different cyclization strategies bound to the central cavity of the cetuximab Fab domain are presented. The affinity of each cyclic derivative for the Fab was determined by surface plasmon resonance and correlated to structural differences. Overall, it was observed that the disulfide bond used to cyclize the peptide favorably packs against a hydrophobic ‘pocket’ and that amidation and acetylation of the original disulfide meditope increased the overall affinity ∼2.3-fold. Conversely, replacing the terminal cysteines with serines and thus creating a linear peptide reduced the affinity over 50-fold, with much of this difference being reflected in a decrease in the on-rate. Other cyclization methods, including the formation of a lactam, reduced the affinity but not to the extent of the linear peptide. Collectively, the structural and kinetic data presented here indicate that small perturbations introduced by different cyclization strategies can significantly affect the affinity of the meditope–Fab complex.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Increasing the revenue from lignocellulosic biomass: Maximizing feedstock utilization

The production of renewable chemicals and biofuels must be cost- and performance- competitive with petroleum-derived equivalents to be widely accepted by markets and society. We propose a biomass conversion strategy that maximizes the conversion of lignocellulosic biomass (up to 80% of the biomass to useful products) into high-value products that can be commercialized, providing the opportunity for successful translation to an economically viable commercial process. Our fractionation method preserves the value of all three primary components: (i) cellulose, which is converted into dissolving pulp for fibers and chemicals production; (ii) hemicellulose, which is converted into furfural (a building block chemical); and (iii) lignin, which is converted into carbon products (carbon foam, fibers, or battery anodes), together producing revenues of more than $500 per dry metric ton of biomass. Once de-risked, our technology can be extended to produce other renewable chemicals and biofuels.

09 BIOMASS FUELS↗
DOE OSTI2016

SynTec Final Technical Report: Synthetic biology for Tailored Enzyme cocktails

Using a novel enzyme screening method inspired by synthetic biology, Novozymes developed new technology under SynTec which allows for more rapidly tailoring of enzyme cocktails. The methodology can be applied to specific feedstocks, and or coupled to address a specific hydrolytic conversion process context. Using combinatorial high throughput screening of libraries of enzyme domains, we can quickly assess which combination of catalytic modules delivers the best performance for a specific condition. To demonstrate the effectiveness of the screening process, we measured performance of the output catalytic cocktail compared to CTec3/HTec3. SynTec benchmark cocktail - blend of Cellic® CTec3 and HTec3. The test substrate was - ammonia fiber expansion pretreated corn stover (AFEX™ PCS).CTec3/HTec3 was assayed at the optimal pH and temperature, and also in the absence of any pH adjustment. The new enzyme cocktail discovered under SynTec was assayed in the absence of any pH adjustment and at the optimal temperature. Conversion is delivered by SynTec enzyme at significant dose reduction relative to CTec3/HTec3 at the controlled pH optimum, and without titrant required to maintain pH, which delivers additional cost savings relative to current state of the art process. In this 2.5 year $4M project, the team delivered an experimental cocktail that significantly outperformed CTec3/HTec3 for a specific substrate, and for specific hydrolysis conditions. As a means of comparing performance improvement delivered per research dollar spent, we note that SynTec delivered a similar performance improvement to the previous award, in a shorter time and with fewer resources than for the previously successful DOE project DECREASE, a 3.5 year, $25M project, though this project focused on a different substrate and used different hydrolysis conditions. The newly implemented technology for rapid sourcing of new cellulases and hemicellulases from nature is an example of Novozymes' continued innovation that results in more effective products for the advanced biofuel market.

09 BIOMASS FUELS↗
DOE OSTI2020

Engineering of Lead Selenide Quantum Dot Based Devices and Core/Shell Heterostructures

Near infrared (NIR) emitting colloidal quantum dots (QDs) such as PbSe are interesting materials for implementation in various optoelectronic devices such as solar cells, photodetectors, and radiation detectors. Material properties like size tunable emission wavelengths, facile solution processability, the possibility of carrier multiplication and Auger assisted up-conversion, and high Z number provide PbSe QDs with unique advantages over many currently available commercial materials used in these devices. In this dissertation, after an introduction to QDs in general, we first focus on synthesis of PbSe-based heterostructured QDs for study via optical spectroscopy. PbSe/CdSe QDs synthesized via cation exchange reaction were used as seeds to study the proper conditions for further CdSe or CdS shell growth. Optical spectroscopy studies show that growth of thicker CdSe shells leads to tunable visible emission, while growth of thick CdS shells can greatly increase the photoluminescence quantum yield (PLQY) observed from the intermediate CdSe shell. NIR PL lifetimes can be greatly enhanced by the growth of CdS shells, due to strong delocalization of the hole wavefunction within the PbSe core, while the electron is delocalized throughout the QD including in the CdS shell, resulting in radiative lifetimes in the tens of microseconds. Two pulse delay measurements show that Auger assisted up conversion is also taking place in these engineered QD dot heterostructures. In the sections that follow, we look at QD devices, first with a focus on novel devices fabricated from PbSe QDs, using an amine synthesis method that allows for facile in-solution ligand exchange. QD film mobilities are measured for PbSe QDs capped with various short ionic ligands. Carrier densities in PbSe QD films are calculated from C-V measurements, showing for the first time that carrier densities can be modulated by simply changing the capping ligand. vii Radiation detectors utilizing PbSe QDs capped with KI and NH4I ligands show tangible response to incident alpha radiation. Current output response to alpha radiation is dependent on strength of radiation source and amount of bias voltage applied. In the final section a critical review of hybrid layered 2D-QD photodetectors is presented. In a typical example, PbSe and PbS QDs act as the absorbing layer in phototransistor devices which utilize layered 2D materials such as graphene and transition metal dichalcogenides as transport layers. Resulting devices display high gains and improved directivities compared to QD only and 2D only devices.

36 MATERIALS SCIENCE↗