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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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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Tin–Lead Alloying for Efficient and Stable All-Inorganic Perovskite Solar Cells

Cesium containing all-inorganic perovskites have received considerable interest in photovoltaics research because of their potential for improved stability compared to their organic-inorganic hybrid counterparts. However, the inorganic perovskites studied thus far still suffer from lower power conversion efficiency and long-term instability, due to an unfavorable bandgap and either phase instability or air-sensitivity. Herein, A strategy to mitigate these concerns is investigated by alloying tin and lead on the B site to form tin-lead alloyed low-bandgap (~1.34 eV) inorganic CsSn 0.3 Pb 0.7 I 3 perovskites. Solar cells made using this material in an inverted full-structured architecture with a PEDOT:PSS hole transport materials (HTM) attain power conversion efficiency (PCE) up to 9.41% (stabilized PCE 7.23%). Furthermore, a simple HTM-free device without PEDOT:PSS layer is demonstrated more stable than the full-structured device and exhibits a PCE of 7.60% (stabilized PCE 7.31%) – the highest efficiency to date for an inorganic perovskite with a bandgap below 1.40 eV. This simplified device structure shows good reproducibility and stability. Finally, this work provides a possible route for fabricating low-cost, high stability devices with competitive efficiencies.

14 SOLAR ENERGY↗
DOE OSTI2023

Y-Type Non-Fullerene Acceptors with Outer Branched Side Chains and Inner Cyclohexane Side Chains for 19.36% Efficiency Polymer Solar Cells

Raising the lowest unoccupied molecular orbital (LUMO) energy level of Y-type non-fullerene acceptors can increase the open-circuit voltage (V oc ) and thus the photovoltaic performance of the current top performing polymer solar cells (PSCs). One of the viable routes is demonstrated by the successful Y6 derivative of L8-BO with the branched alkyl chains at the outer side. This will introduce steric hindrance and reduce intermolecular aggregation, thus open up the bandgap and raise the LUMO energy level. To take further advantages of the steric hindrance influence on optoelectronic properties of Y6 derivatives, two Y-type non-fullerene acceptors of BTP-Cy-4F and BTP-Cy-4Cl are designed and synthesized by adopting outer branched side chains and inner cyclohexane side chains. An outstanding V oc of 0.937 V is achieved in the D18:BTP-Cy-4F binary blend devices along with a power conversion efficiency (PCE) of 18.52%. With the addition of BTP-eC9 to extend the absorption spectral coverage, a remarkable PCE of 19.36% is realized finally in the related ternary blend devices, which is one of the highest values for single-junction PSCs at present. The results illustrate the great potential of cyclohexane side chains in constructing high-performance non-fullerene acceptors and their PSCs.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Polynomial Chaos Surrogate Construction for Random Fields with Parametric Uncertainty

Engineering and applied science rely on computational experiments to rigorously study physical systems. The mathematical models used to probe these systems are highly complex, and sampling-intensive studies often require prohibitively many simulations for acceptable accuracy. Surrogate models provide a means of circumventing the high computational expense of sampling such complex models. In particular, polynomial chaos expansions (PCEs) have been successfully used for uncertainty quantification studies of deterministic models where the dominant source of uncertainty is parametric. We discuss an extension to conventional PCE surrogate modeling to enable surrogate construction for stochastic computational models that have intrinsic noise in addition to parametric uncertainty. We develop a PCE surrogate on a joint space of intrinsic and parametric uncertainty, enabled by Rosenblatt transformations, which are evaluated via kernel density estimation of the associated conditional cumulative distributions. Furthermore, we extend the construction to random field data via the Karhunen–Loève expansion. We then take advantage of closed-form solutions for computing PCE Sobol indices to perform a global sensitivity analysis of the model which quantifies the intrinsic noise contribution to the overall model output variance. Additionally, the resulting joint PCE is generative in the sense that it allows generating random realizations at any input parameter setting that are statistically approximately equivalent to realizations from the underlying stochastic model. The method is demonstrated on a chemical catalysis example model and a synthetic example controlled by a parameter that enables a switch from unimodal to bimodal response distributions.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2025

Next-generation perovskite photovoltaics: improving, stabilizing, and lead-sealing of record-setting laboratory solar cells towards commercialization

Summary: In the proposed program we plan to improve perovskite photovoltaic performance by developing (1) orientational control of 3D/2D perovskite heterostructures to simplify device architectures, thus improving device efficiencies and stability; (2) high-throughput optical measurements and real-time device simulations for device optimization; (3) robust, dual-pronged lead-sealing and oxygen/moisture/UV barrier films for long-term stability. Specifically, we seek to develop an in-depth understanding of the perovskite film formation, interface passivation, device stability, and environmentally friendly encapsulation, which together will lead to perovskite devices with PCE of over 28%, stability of T80 at 85/85 (85% humidity at 85 degrees C) for 10,000, expected to be equivalent to T90 of 100 hours), and architectures that would satisfy the U.S. EPA and RoHS limits of lead-leaching. The knowledge generated with this project will be applicable to tandem devices with wider-bandgap perovskites.

14 SOLAR ENERGY↗
DOE OSTI2022

The synergistic effects of central core size and end group engineering on performance of narrow bandgap nonfullerene acceptors

Understanding the relationship between the molecular structure and photoelectric properties of fused-ring non-fullerene acceptors (NFAs) is of far-reaching significance to the development of organic solar cells (OSCs). Herein, six NFAs based on multiple thiophenes (4 T, 6 T and 8 T) are employed to systematically probe the synergistic effects of extending central core size and terminal fluorination. The absorption results manifest that the molecular absorption is comprehensively affected by molecular crystallinity, planarity, conjugation length and intramolecular electron push–pull effect, simultaneously. The intensity of electron push–pull effect is not only related to the electron-donating ability of central core and the electron-withdrawing ability of end group, but also may be related to the distance between the positive and negative centers. The extension of central core leads to the more planar backbone and stronger crystallinity of NFAs, and less energy loss (E loss ) in its based OSC. Compared with the extension of central core, terminal fluorination has a greater impact on molecular photoelectric properties. The terminal fluorination significantly enhances the push–pull effect, lowers the energy levels, and slightly increases the vibrational relaxation. As a result, the strongest crystallinity and coplanarity of 8TIC-4F lead to a low vibrational relaxation of 0.18 eV, which makes PTB7-Th:8TIC-4F device exhibit a small E loss of 0.51 eV and a high efficiency of 10.4%. In addition, the fluorinated 6TIC-4F with suitable core size exhibits suitable energy level, absorption, crystallization, and phase separation morphology, making its as-cast device up to 11.61% efficiency. Finally, to the best of the authors’ knowledge, the PCE of 11.61% for PTB7-Th:6TIC-4F based device without any treatment is one of the highest values reported for the NAFs with over 1000 nm absorption.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Reducing Non-Radiative Recombination in Perovskite Solar Cells with a SiO2-Graphene Oxide Buried Interface Layer

Perovskite solar cells (PSCs) have emerged as a transformative photovoltaic technology. However, the device performance of inverted PSCs is dramatically limited by surface defects and the underlying film morphology of metal halide perovskite (MHP) thin film. Herein, we report a novel buried interface layer consisting of SiO2 nanoparticles (NPs) chemically bonded to graphene oxide (GO), deposited atop a hydrophobic hole extraction layer (HEL) to address this limitation. The SiO2 NPs serve as insoluble scaffolds that immobilize GO sheets on the hydrophobic HEL surface, enabling the formation of homogeneous MHP thin films. Meanwhile, the GO functional groups interact with surface-uncoordinated Pb2+, suppressing interfacial defects and guiding crystal grain growth of the resultant MHP thin films. This synergistic effect suppresses non-radiative charge recombination and enhances charge extraction efficiency. As a result, a 26.07% efficiency with significantly suppressed photocurrent hysteresis is observed from PSCs incorporating the SiO2-GO buried interface layer. Moreover, the above PSCs maintain 92% of their initial PCE after 1800 h of continuous operation at the maximum power point under AM 1.5 G (100 mW/cm2) illumination at 25 degrees C in air with 50-60% relative humidity. These results demonstrate that we have developed a facile and effective way to realize high-performance inverted PSCs.

14 SOLAR ENERGY↗
DOE OSTI2025

Proton radiation resilience of CdSeTe photovoltaics: High predicted end-of-life performance for space applications

Two types of cadmium selenide telluride (CdSeTe) photovoltaic devices have been exposed to high-energy (150–1500 keV) protons with fluences ranging from 1 × 10 11 to 9 × 10 13 cm −2 . Pre- and post-irradiation current density vs voltage characteristic data were collected and analyzed. Arsenic-doped CdSeTe devices retained 80% of the power conversion efficiency (PCE) relative to control devices after exposure to 10 12 cm −2 650 keV protons, while copper-doped CdSeTe devices retained about 95% of the control PCE under the same irradiation condition. Displacement damage dose analysis coupled with simulations for duration-dependent performance in a medium Earth orbit space mission revealed superior PCE remaining factors, indicating greater resilience to proton bombardment than state-of-the-art multijunction III-V based space photovoltaic technologies.

CdTe solar cells↗
DOE OSTI2023

Anthradithiophene (ADT)-Based Polymerized Non-Fullerene Acceptors for All-Polymer Solar Cells

Realizing efficient all-polymer solar cell (APSC) acceptors typically involves increased building block synthetic complexity, hence potentially unscalable syntheses and/or prohibitive costs. Here we report the synthesis, characterization, and implementation in APSCs of three new polymer acceptors P1–P3 using a scalable donor fragment, bis(2-octyldodecyl)anthra[1,2-b : 5,6-b’]dithiophene-4,10-dicarboxylate (ADT) co-polymerized with the high-efficiency acceptor units, NDI, Y6, and IDIC. Further, all three copolymers have comparable photophysics to known polymers; however, APSCs fabricated by blending P1, P2 and P3 with donor polymers PM5 and PM6 exhibit modest power conversion efficiencies (PCEs), with the champion P2-based APSC achieving PCE=5.64 %. Detailed morphological and microstructural analysis by AFM and GIWAXS reveal a non-optimal APSC active layer morphology, which suppresses charge transport. Despite the modest efficiencies, these APSCs demonstrate the feasibility of using ADT as a scalable and inexpensive electron rich/donor building block for APSCs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1995

Development of CFC-Free Cleaning Processes at the NASA White Sands Test Facility

The NASA White Sands Test Facility (WSTF) is developing cleaning and verification processes to replace currently used chlorofluorocarbon-113- (CFC-113-) based processes. The processes being evaluated include both aqueous- and solvent-based techniques. The presentation will include the findings of investigations of aqueous cleaning and verification processes that are based on a draft of a proposed NASA Kennedy Space Center (KSC) cleaning procedure. Verification testing with known contaminants, such as hydraulic fluid and commonly used oils, established correlations between nonvolatile residue and CFC-113. Recoveries ranged from 35 to 60 percent of theoretical. WSTF is also investigating enhancements to aqueous sampling for organics and particulates. Although aqueous alternatives have been identified for several processes, a need still exists for nonaqueous solvent cleaning, such as the cleaning and cleanliness verification of gauges used for oxygen service. The cleaning effectiveness of tetrachloroethylene (PCE), trichloroethylene (TCE), ethanol, hydrochlorofluorocarbon-225 (HCFC-225), tert-butylmethylether, and n-Hexane was evaluated using aerospace gauges and precision instruments and then compared to the cleaning effectiveness of CFC-113. Solvents considered for use in oxygen systems were also tested for oxygen compatibility using high-pressure oxygen autoignition and liquid oxygen mechanical impact testing.

Beeson, Harold↗
DOE OSTI2023

Carbon Electrode with Sputtered Au Coating for Efficient and Stable Perovskite Solar Cells

Halide perovskite solar cells (PSCs) represent a low-cost and high-efficiency solar technology. However, most of the highly efficient PSCs need a noble electrode, such as Au, through thermal evaporation. Here it is reported that a sputtered Au electrode on a PSC could damage the organic hole transport layer (HTL) and the perovskite layer. Here, we report a simple, yet effective sputtered gold nanoparticle decorated carbon electrode to fabricate efficient and stable planar PSCs. The sputtered Au layer on the doctor-bladed coated carbon electrode can be directly applied to the perovskite semicells by mechanical stacking. By optimizing the gold thickness, a power conversion efficiency (PCE) of 16.87% was obtained for the composite electrode-based PSC, while the reference device recorded a PCE of 12.38%. The composite electrode-based device demonstrated 96% performance retention after being stored under humid conditions (50-60%) without encapsulation for ~100 h. This demonstrates a promising pathway toward the commercialization of large-scale manufacturable sputtered electrodes for the PSC solar module.

14 SOLAR ENERGY↗
DOE OSTI2021

Western Sector In-Situ Chemical Oxidation Project: Additional Injection Pilot Testing Supplemental Results (U)

Trichloroethylene (TCE) and tetrachloroethylene (PCE) are persistent at elevated concentrations in the Western Sector of the M-Area Hazardous Waste Management Facility (HWMF) groundwater plume. Migration of these chlorinated ethenes as Dense Non-Aqueous Phase Liquids (DNAPLs) occurred from the M-Area Settling Basin along geologic strata resulting in a high concentration groundwater plume in Western Sector. Pump-and-treat has been active for over 30 years at the M-Area HWMF to hydraulically contain the primary sources of the plume in addition to other remediation strategies throughout the contaminated zone, like soil vapor extraction, dynamic underground stripping, groundwater recirculation wells, and bioremediation. In-situ chemical oxidation (ISCO) has been identified as a viable treatment method for removal of these volatile organic compounds (VOCs) due to the complex lithology and high concentrations in this part of the aquifer. In addition to ISCO, a new recovery well (i.e., RWM018) was also installed in Western Sector to contain the high concentration VOC plume. The ISCO projects have utilized the gradient induced by RWM018 to help plan the injection and monitoring locations. The combination of ISCO and the additional pump and treat in Western Sector with the installation of RWM018 will help to control the plume and maximize remediation efforts.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2025

Hydrophobic Carbon Nanosheets as Passivation Layer for Perovskite Solar Cells with High Efficiency and Stability (Final Technical Report)

Hybrid organic-inorganic metal halide perovskites have continually demonstrated competitive advantages for photovoltaic applications due to their high light absorption coefficient, tunable bandgaps, ambipolar charge mobility and high tolerance of defects. However, there are many challenges yet to overcome to bring this technology to the market. For instance, bridging the ‘scaling gap’ and transitioning PSCs from a lab scale to an industrial scale is a serious challenge. This project developed a high stability and inexpensive perovskite solar cell (PSC) by incorporating hydrophobic carbon nanosheets as counter electrodes (CEs). We demonstrated that the hydrogenated carbon nanosheets with tunable hydrophobic properties as CEs can improve life-time stability of PSCs in operating conditions (i.e. humid air) while achieving impressive power conversion efficiency (PCE).

14 SOLAR ENERGY↗
NASA NTRS1997

Replacement Technologies for Precision Cleaning of Aerospace Hardware for Propellant Service

The NASA White Sands Test Facility (WSTF) is developing cleaning and verification processes to replace currently used chlorofluorocarbon-l13- (CFC-113-) based processes. The processes being evaluated include both aqueous- and solvent-based techniques. Replacement technologies are being investigated for aerospace hardware and for gauges and instrumentation. This paper includes the findings of investigations of aqueous cleaning and verification of aerospace hardware using known contaminants, such as hydraulic fluid and commonly used oils. The results correlate nonvolatile residue with CFC 113. The studies also include enhancements to aqueous sampling for organic and particulate contamination. Although aqueous alternatives have been identified for several processes, a need still exists for nonaqueous solvent cleaning, such as the cleaning and cleanliness verification of gauges used for oxygen service. The cleaning effectiveness of tetrachloroethylene (PCE), trichloroethylene (TCE), ethanol, hydrochlorofluorocarbon 225 (HCFC 225), HCFC 141b, HFE 7100(R), and Vertrel MCA(R) was evaluated using aerospace gauges and precision instruments and then compared to the cleaning effectiveness of CFC 113. Solvents considered for use in oxygen systems were also tested for oxygen compatibility using high-pressure oxygen autogenous ignition and liquid oxygen mechanical impact testing.

Harold Beeson↗
DOE OSTI2023

Recycling the Energy of Indoor Light: Highly Efficient Organic Photovoltaics via a Ternary Strategy

A ternary approach in organic photovoltaics (OPV) is simple and reliable to effectively tune the optical, electrical and morphological properties of the photoactive layer for high efficiency as well as long-term stability under 1 sun. However, there have been few papers reporting spectra and weak illumination compared to outdoor light. In this study, by using two compatible 16 structures, we demonstrate a simultaneous modulation of light absorption and molecular donor polymers (PM7 and PM7 D1) with slightly-different band gaps and similar chemical packing under ambient conditions, which resulted in efficient indoor OPVs exhibiting power conversion efficiency (PCE) over 20% under 1000 lux of warm white light-emitting diode (2900 K). From morphological analysis, we infer that PM7 serves to seed nucleation of PM7 D1 in the ternary blend, templating its crystallization and alignment along the PM7 backbone. Such templating effect leads to increased domain spacing and relative degree of crystallinity (rDoC) compared to those of each binary system. We further show that higher rDoC helps suppress both bimolecular and trap-assisted recombination of photogenerated charges in the ternary devices. As a result, the complementary absorption and synergistic molecular assembly of the two donor polymers enhance the short-circuit current density as to increase the average PCEs from 9.6 to 10.3% under 1 sun and from 18.7 to 20.0% under 1000 lux. We envision that our strategy of incorporating both a planar and a flexible donor polymer with similar chemical structures can be generally applicable to attain a high performance ternary OPV under both 1 sun and indoor light.

14 SOLAR ENERGY↗
DOE OSTI2024

Tetrahydrofuran Processable Organic Solar Cells with 19.45% Efficiency Realized by Introducing High Molecular Dipole Unit Into the Terpolymer

Developing organic solar cells (OSCs) processable with halogen‐free, non‐aromatic solvents is crucial for practical applications, yet challenging due to the limited solubility of most photoactive materials. Here, this study introduces high‐performance terpolymers processable in tetrahydrofuran (THF) by incorporating dithienophthalimide (DPI) into the PM6 backbone. DPI extends the absorption band, lowers HOMO levels, and improves THF solubility and film crystallinity through its large dipole moment effect. Optimal PBD‐10:L8‐BO devices processed with THF achieved a competitive power conversion efficiency (PCE) of 18.79%, approaching chloroform‐processed devices (19.04%). By introducing PBTz‐F as a second donor, ternary OSCs reached an impressive 19.45% PCE when processed with THF. This improvement stems from enhanced photon generation, improved morphology, better charge transport, longer exciton lifetimes, efficient charge dissociation and collection, and suppressed recombination. These PCEs of 18.79% and 19.45% for binary and ternary blend OSCs, respectively, represent the highest reported efficiencies for OSCs processed with halogen‐free, non‐aromatic solvents. This work demonstrates significant progress in eco‐friendly OSC fabrication, paving the way for more sustainable and commercially viable organic photovoltaic technologies.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Bayesian model updating with finite element vs surrogate models: Application to a miter gate structural system

Bayesian finite element (FE) model updating using direct model evaluations of large-scale high-fidelity FE models is extremely computationally expensive. Surrogate models can be used as fast emulators of FE models to accelerate the model calibration process. The physics/mechanics-based FE models are still the underpinning behind the surrogate models. Here, this paper evaluates the loss in accuracy and the gain in computational time while performing Bayesian model updating by using surrogate model evaluations compared to using direct FE model evaluations. This evaluation is crucial before entirely relying on surrogate models in model updating for structural health monitoring (SHM) and damage prognosis (DP) purposes. This paper also demonstrates Bayesian updating and surrogate model construction of large-scale high-fidelity FE models of infrastructure systems. In this regard, the miter gate structural system is considered as the testbed structure. Three predominant damage modes (loss of contact between gate and wall, loss of thickness due to corrosion, and loss of tension in the diagonal rods) are considered for model updating purposes. Bayesian model updating is performed using direct FE evaluations by leveraging parallel computing. Two types of surrogates, namely polynomial chaos expansion (PCE) and Gaussian process regression (GPR), are developed for the miter gate. Model updating is performed again using the trained surrogate models, and the updating results are compared with their counterparts obtained using the direct FE evaluation results. The posterior distribution of the FE model parameters obtained using the trained surrogates are sufficiently accurate with respect to the posterior obtained utilizing the direct FE evaluations. In addition, an approximate 4-fold decrease in the computational time was observed when using surrogate model evaluations instead of direct FE evaluations for model updating.

42 ENGINEERING↗
DOE OSTI2021

High-specific-power flexible transition metal dichalcogenide solar cells

Abstract Semiconducting transition metal dichalcogenides (TMDs) are promising for flexible high-specific-power photovoltaics due to their ultrahigh optical absorption coefficients, desirable band gaps and self-passivated surfaces. However, challenges such as Fermi-level pinning at the metal contact–TMD interface and the inapplicability of traditional doping schemes have prevented most TMD solar cells from exceeding 2% power conversion efficiency (PCE). In addition, fabrication on flexible substrates tends to contaminate or damage TMD interfaces, further reducing performance. Here, we address these fundamental issues by employing: (1) transparent graphene contacts to mitigate Fermi-level pinning, (2) MoO x capping for doping, passivation and anti-reflection, and (3) a clean, non-damaging direct transfer method to realize devices on lightweight flexible polyimide substrates. These lead to record PCE of 5.1% and record specific power of 4.4 W g −1 for flexible TMD (WSe 2 ) solar cells, the latter on par with prevailing thin-film solar technologies cadmium telluride, copper indium gallium selenide, amorphous silicon and III-Vs. We further project that TMD solar cells could achieve specific power up to 46 W g −1 , creating unprecedented opportunities in a broad range of industries from aerospace to wearable and implantable electronics.

42 ENGINEERING↗
DOE OSTI2024

Effect of Molecular Conformation on Intermolecular Interactions and Photovoltaic Performances of Giant Molecule Acceptors

The molecular conformation of giant molecule acceptors (GMAs) plays a significant role in regulating the intermolecular interactions and their photovoltaic performances in organic solar cells (OSCs). For the linear GMA GT‐l, the stronger homo‐molecular interaction causes its aggregation being weakly affected by the donor, thus forming an ordered molecular stacking and proper phase separation in its blend film. The star‐shaped GMA GT‐s‐based blend film shows a dominant hetero‐molecular interaction that suppresses the aggregation of the donor and acceptor, resulting in smaller phase separation and more uniform vertical phase distribution. While for another star‐shaped GMA GTs, the weakest hetero‐molecular interaction causes its blend film to form larger phase separation. Therefore, the GT‐l based OSC with PM6 as donor shows the highest charge mobilities, the fastest charge transfer (CT) process, reduced energy loss and less charge recombination, contributing to a higher power conversion efficiency (PCE) of 19.03%. Comparatively, the PCEs of the OSCs based on GTs and GT‐s are 18.05% and 17.58% respectively. Notably, all the three GMAs based OSCs show excellent thermal stability and long‐term storage stability. This study provides a facile strategy by tuning the linking unit and its connecting mode for designing highly efficient and stable organic photovoltaic materials.

Chemistry↗