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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 OSTI2023

Thiol‐Functionalized Conjugated Metal–Organic Frameworks for Stable and Efficient Perovskite Photovoltaics

Abstract Metal–organic frameworks (MOFs) have been investigated recently in perovskite photovoltaics owing to their potential to boost optoelectronic performance and device stability. However, the impact of variations in the MOF side chain on perovskite characteristics and the mechanism of MOF/perovskite film formation remains unclear. In this study, three nanoscale thiol‐functionalized UiO‐66‐type Zr‐based MOFs (UiO‐66‐(SH) 2 , UiO‐66‐MSA, and UiO‐66‐DMSA) are systematically employed and examined in perovskite solar cells (PSCs). Among these MOFs, UiO‐66‐(SH) 2 , with its rigid organic ligands, exhibited a strong interaction with perovskite materials with more efficient suppression of perovskite vacancy defects. More importantly, A detailed and in‐depth discussion is provided on the formation mechanism of UiO‐66‐(SH) 2 ‐assisted perovskite film upon in situ GIWAXS performed during the annealing process. The incorporation of UiO‐66‐(SH) 2 additives substantially facilitates the conversion of PbI 2 into the perovskite phase, prolongs the duration of stage I, and induces a delayed phase transformation pathway. Consequently, the UiO‐66‐(SH) 2 ‐assisted device demonstrates reduced defect density and superior optoelectronic properties with optimized power conversion efficiency of 24.09% and enhanced long‐term stability under ambient environment and continuous light illumination conditions. This study acts as a helpful design guide for desired MOF/perovskite structures, enabling further advancements in MOF/perovskite optoelectronic devices.

14 SOLAR ENERGY↗
DOE OSTI2021

On-Device Lead Detention for Perovskite Solar Cells

As the power conversion efficiency (PCE) of perovskite solar cells (PSCs) have reached above 25.5%, the commercialization of PSCs appears to be imminent due to its lower fabrication cost, simpler manufacturing processes, and larger processing area over Si-based solar cells that dominate the current photovoltaic (PV) market. While many efforts have focused on tackling the stability and scalability issues with promising advances, the potential lead (Pb) toxicity issue has remained a concern of PSCs. Unlike the metallic Pb, the Pb 2+ in perovskite generally exhibit high solubility in water. However, Pb 2+ has so far appeared to be a necessary component in all high-efficiency PSCs. Handful methods have been explored to mitigate the potential Pb2+ leaking issue, which can be generally categorized as physical encapsulation and our pioneering chemical absorption method, which was extended by others later. Since device damage is inevitable in outdoor conditions, physical encapsulation alone is not sufficient to mitigate the long-term risk of leakage of soluble Pb 2+ to the environment under severe weather conditions. As a result, the chemical absorption approach has recently attracted significant attention as a more effective solution to confine the potential lead leakage. Hence, it is of great value to develop durable and highly efficient Pb-absorbing components that can be conveniently mounted onto the standard PSC stack as an add-on accessory in line with the encapsulation of PSCs instead of modifying the standard device fabrication and/or device configuration.

14 SOLAR ENERGY↗
DOE OSTI2026

Understanding Defect Activation and Kinetics in Next Generation CdTe Absorbers

This project investigated the role of defects and dopants in cadmium telluride (CdTe) solar cells to improve efficiency and long-term stability. Advanced X-ray microscopy and spectroscopy techniques were used to map composition, identify defect structures, and measure charge collection at the nanoscale. These experimental results were combined with computational modeling to understand how dopants such as copper and arsenic interact with other elements during processing. The study found that many dopants become electrically inactive due to the formation of complexes with chlorine and oxygen, limiting carrier concentration and device performance. It also showed that selenium, used to enhance efficiency, can migrate within the material during both manufacturing and operation, altering local structure and potentially affecting stability. The project developed new diagnostic and analysis tools for studying photovoltaic materials and provided a mechanistic understanding of key performance limitations. These insights support the development of more efficient, stable, and cost-effective CdTe solar technologies for large-scale energy deployment.

14 SOLAR ENERGY↗
DOE OSTI2026

Security Constrained Economic Optimization of Photovoltaic and Other Distributed Assets

The rapid growth of distributed energy resources (DERs), especially photovoltaic (PV) systems, has introduced new complexities in maintaining grid reliability, stability, and cost-effective operation. This project addresses these challenges by developing and demonstrating a scalable GridOS Distributed Energy Resource Management System (DERMS) that enables secure, real-time optimization and control of DERs at the distribution feeder level.

14 SOLAR ENERGY↗
DOE OSTI2023

PV Inverter Testing for Momentary Cessation and Rate-of-Change-of-Frequency Events: Preprint

To understand the power system stability and develop better electromagnetic transient (EMT) models of field deployed photovoltaic (PV) inverters, it is important to characterize inverters' response to abnormal voltage and frequency scenarios. Because EMT models are not typically available for small distribution-connected PV inverters, and because inerterconnection standards historically did not specify desired ride-through behaviors, we tested two such inverters in the lab to characterize their responses to severe undervoltage events and high rate-of-change-of-frequency (ROCOF) conditions. The inverters tested were pre-IEEE 1547-2018 residential PV inverters widely used in the Hawaiian Electric territory and many other areas. The testing results for undervoltage scenarios showed that the inverter from one vendor exhibited momentary cessation while the inverter from the other vendor did not exhibit momentary cessation behavior or tripping for most of the events below the 120 ms undervoltage trip threshold duration set by IEEE 1547-2003. The testing results for ROCOF scenarios showed that the inverter from one vendor temporarily lost synchronization during ROCOF conditions while the inverter from the other vendor did not lose synchronization or cease generation for any ROCOF conditions. Both the inverters were also tested for EMT-simulated grid events with severe changes in frequency and voltage. The observed responses of the inverters were different from the simulated response of PV inverters represented the best available assumptions from pre-existing information. The results from these experiments can be used to update the inverter models used in bulk power system studies.

IEEE 1547 2018↗
DOE OSTI2021

Buried Interfaces in Halide Perovskite Photovoltaics

Understanding the fundamental properties of buried interfaces in perovskite photovoltaics is of paramount importance to the enhancement of device efficiency and stability. Nevertheless, accessing buried interfaces poses a sizeable challenge because of their non-exposed feature. In this paper, the mystery of the buried interface in full device stacks is deciphered by combining advanced in situ spectroscopy techniques with a facile lift-off strategy. By establishing the microstructure-property relations, the basic losses at the contact interfaces are systematically presented, and it is found that the buried interface losses induced by both the sub-microscale extended imperfections and lead-halide inhomogeneities are major roadblocks toward improvement of device performance. The losses can be considerably mitigated by the use of a passivation-molecule-assisted microstructural reconstruction, which unlocks the full potential for improving device performance. The findings open a new avenue to understanding performance losses and thus the design of new passivation strategies to remove imperfections at the top surfaces and buried interfaces of perovskite photovoltaics, resulting in substantial enhancement in device performance.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Antisolvent‐Mediated Air Quench for High‐Efficiency Air‐Processed Carbon‐Based Planar Perovskite Solar Cells

Perovskite solar cells (PSCs) have becoma a leading low‐cost photovoltaic technology, achieving power conversion efficiencies (PCEs) of up to 26.1%. However, their commercialization is hindered by stability issues and the need for controlled processing environments. Carbon‐electrode‐based PSCs (C‐PSCs) offer enhanced stability and cost‐effectiveness compared to traditional metal‐electrode PSCs, i.e., Au and Ag. However, processing challenges persist, particularly in air conditions where moisture sensitivity poses a significant hurdle. Herein, a novel air processing technique is presented for planar C‐PSCs that incorporates antisolvent vapors, such as chlorobenzene, into a controlled air‐quenching process. This method effectively mitigates moisture‐induced instability, resulting in champion PCEs exceeding 20% and robust stability under ambient conditions. The approach retains 80% of initial efficiency after 30 h of operation at maximum power point without encapsulation. This antisolvent‐mediated air‐quenching technique represents a significant advancement in the scalable production of C‐PSCs, paving the way for future large‐scale deployment.

14 SOLAR ENERGY↗
DOE OSTI2021

Manipulating the Crystallization Kinetics by Additive Engineering toward High-Efficient Photovoltaic Performance

Additive processing is proven to be an effective method to improve the efficiency and stability of perovskite solar cells; however, its intrinsic role in directing the crystallization pathway and thus morphology formation remains unknown. In situ grazing-incidence wide-angle x-ray scattering (GIWAXS) is applied to study the function of a 1,8-diiodooctane (DIO) additive in manipulating the crystallization behavior of perovskite thin films. It is seen that the DIO additive could induce multi-stage intermediate crystallization phases and increases the activation energy for nucleation and growth, which postpones the perovskite phase transformation time and broadens the transition zone. The elongated crystallization process affords improved perovskite thin film crystallinity and reduces defect density, which enables a longer carrier diffusion length. As a result, improved device efficiency, moisture, and thermal stability can be achieved. The following study provides a new prospective in understanding the additive function in perovskite thin film morphology control from fundamental parameters, indicating the importance of minor processing conditions in global property management toward high device performance.

36 MATERIALS SCIENCE↗
DOE OSTI2020

On-device lead sequestration for perovskite solar cells

Perovskite solar cells, as an emerging high-efficiency and low-cost photovoltaic technology face challenges on their way towards commercialization. Substantial improvements have been made to device stability but potential issues with lead toxicity and leaching from devices remain relatively unexplored. The potential for lead leakage could be perceived as an environmental and public health risk when using perovskite solar cells in building-integrated photovoltaics. Here we present a chemical approach for on-device sequestration of more than 96 per cent of lead leakage caused by severe device damage. A coating of lead-absorbing material is applied to the front and back sides of the device stack. On the glass side of the front transparent conducting electrode, we use a transparent lead-absorbing molecular film containing phosphonic acid groups that bind strongly to lead. On the back (metal) electrode side, we place a polymer film blended with lead-chelating agents between the metal electrode and a standard photovoltaic packing film. The lead-absorbing films on both sides swell to absorb the lead, rather than dissolve, when subjected to water soaking, thus retaining structural integrity for easy collection of lead after damage.

14 SOLAR ENERGY↗
NASA NTRS1985

Light-induced effects-impacts to module performance measurements and reliability testing: An overview

The stability of solar cells is a key factor in determining the reliability of photovoltaic modules and is of great interest in the case of solar cells having a new technology which has not yet been fully developed. In particular this question arises with hydrogenated amorphous silicon (a-Si) solar cells because a-Si exhibits reversible light induced changes in its electronic properties, commonly referred to as the Staebler-Wronski effect (SWE). Continuous progress is being made in the peak conversion efficiencies of a-Si solar cells and efficiencies in excess of 11% have been achieved. However, stability is still a problem. ARCO Solar reports results on solar cells which, after over a year's exposure to sunlight, under open circuit conditions, still have about 7% conversion efficiency. Other results show a region of fast degradation for about a month, after which the degradation diminishes rapidly.

Wronski, C. R.↗
DOE OSTI2020

Stabilization of light-induced effects in Si modules for IEC 61215 design qualification

Standardized testing of commercial photovoltaic modules is widely used around the world and decreases risks of module failures. Such testing also reduces financial risks for module manufacturers and customers. This work examines the expected impact of certain defects in silicon (Si) modules during standardized accelerated testing. Specifically, the behavior of boron-oxygen (BO) light-induced degradation (LID) and light- and elevated temperature-induced degradation (LeTID) are simulated during some of the stress tests in IEC 61215. LID and LeTID reaction rates at qualification temperatures are estimated from earlier published data. It is demonstrated the BO-related LID may cause some false positives and false negatives when IEC 61215 tests are performed as prescribed in the 2016 published version. Possible stabilization steps to avoid these false results are suggested. State changes for the defects causing LeTID occur much more slowly than those causing BO LID, and therefore LeTID is predicted to have a lesser impact on the IEC 61215 stress tests results.

14 SOLAR ENERGY↗
DOE OSTI2021

Improving Photostability of Cesium-Doped Formamidinium Lead Triiodide Perovskite

Using time-resolved in situ X-ray photoelectron spectroscopy, we identify and suppress rapid degradation mechanisms for cesium-stabilized formamidinium lead iodide perovskite materials used in state-of-the-art photovoltaics. Accelerated degradation under high light intensity and heating reveals a photocatalytic reaction pathway responsible for rapid decomposition in iodide-rich compositions and a slower pathway for more stoichiometric samples. Using Avrami–Erofe’ev kinetic analysis, we find that the fast process is consistent with a 2D crystallization and growth mechanism fueled by excess halide salt at grain boundaries and surfaces. Moreover, the rate of decomposition varies dramatically with the wavelength of light used to illuminate the thin films. Furthermore, our results reveal the photodegradation mechanisms of PbI 2 and excess iodide and provide a path to increasing perovskite stability under photoexcitation.

14 SOLAR ENERGY↗
NASA NTRS1994

Static stability of a three-dimensional space truss

Space station requirements for power have resulted in a need for photovoltaic solar arrays possessing large blanket surface area. However, due to the limited shuttle payload volume solar array designers have been driven to a deployable concept that by nature is extremely flexible. The principal support for this array system is the Folding Articulating Square Truss Mast (FASTMast). In order to accomodate service loads the FASTMast is expected to exhibit nonlinear behavior which could possibly result in structural instability. Presented herein are the results of the Lewis Research Center test and analysis efforts performed in an effort to characterize the FASTMast structural behavior in terms of stability. Results include those obtained from recent nonlinear testing and analysis involving a 1/10 segment of the FASTMast flight article. Implications of these results as they relate to expected behavior of the flight unit will also be discussed.

Shaker, John F.↗
NASA NTRS1994

Static Stability of a Three-Dimensional Space Truss

Space Station requirements for power have resulted in a need for photovoltaic solar arrays possessing large blanket surface area. However, due to the limited Shuttle payload volume solar array designers have been driven to a deployable concept that by nature is extremely flexible. The principal support for this array system is the Folding Articulating Square Truss Mast (FASTMast). In order to accommodate service loads the FASTMast is expected to exhibit nonlinear behavior which could possibly result in structural instability. Presented herein are the results of the Lewis Research Center test and analysis efforts performed in an effort to characterize the FASTMast structural behavior in terms of stability. Results include those obtained from recent nonlinear testing and analysis involving a 1/10 segment of the FASTMast flight article. Implications of these results as they relate to expected behavior of the flight unit will also be discussed.

Shaker, John F.↗
DOE OSTI2020

Surface Ligands for Methylammonium Lead Iodide Films: Surface Coverage, Energetics, and Photovoltaic Performance

Surface ligand treatment provides a promising approach for passivating defect states, improving material and device stability, manipulating interfacial energetics, and improving the performance of perovskite solar cells (PSCs). To facilitate targeted selection and design of surface ligands for PSCs, it is necessary to establish relationships between ligand structure and perovskite surface properties. In this work, surface ligands with different binding groups are investigated to determine their extent of surface coverage, whether they form a surface monolayer or penetrate the perovskite, how they influence material energetics and photoluminescence, and how this combination of factors affects PSC performance. Ultraviolet and inverse photoelectron spectroscopy measurements show that surface ligands can significantly shift the ionization energy and electron affinity. Lastly, these changes in surface energetics substantially impact PSC performance, with the performance decreasing for ligands that create less favorable energy landscapes for electron transfer from MAPbI 3 to the electron transport layer, C 60 .

14 SOLAR ENERGY↗
DOE OSTI2023

Facile, Versatile and Stepwise Synthesis of High‐Performance Oligomer Acceptors for Stable Organic Solar Cells

Abstract Oligomer acceptors have recently emerged as promising photovoltaic materials for achieving high power conversion efficiency (PCE) and long‐term stability in organic solar cells (OSCs). However, the limited availability of diverse acceptors, resulting from the sole synthetic approach, has hindered their potential for future industrialization. In this study, we present a facile and effective stepwise approach that utilizes two consecutive Stille coupling reactions for the synthesis of oligomer acceptors. To demonstrate the feasibility of the novel approach, we successfully synthesize a trimer acceptor, Tri‐Y6‐OD, and further systematically investigate the impact of oligomerization on device performance and stability. The results reveal that this approach has significant advantages compared to the conventional method, including reduced formation of unwanted by‐products and lower difficulties in purification. Remarkably, the OSC based on PM6 : Tri‐Y6‐OD achieves an impressive PCE of 18.03 % and maintains 80 % of the initial PCE (T 80 ) for 1523 h under illumination, surpassing the performance of the corresponding small molecule acceptor Y6‐OD‐based device. Furthermore, the versatility of the synthetic strategy in obtaining diverse acceptors is further demonstrated. Overall, our findings provide a facile, versatile and stepwise way for synthesizing oligomer acceptors, thereby facilitating the development of stable and efficient OSCs.

Chemistry↗
DOE OSTI2025

An improved guess for the variational calculation of charge-transfer excitations in large systems

Ab initio quantum-chemical methods that perform well for computing the electronic ground state are not straightforwardly transferable to electronically excited states, particularly in large molecular systems. Wave function theory offers high accuracy, but is often prohibitively expensive. Methods based on time-dependent density functional theory (TD-DFT) are crucially sensitive to the chosen exchange-correlation functional (XCF) parameterization, and system-specific tuning protocols were therefore proposed to address the method's robustness. Methods based on the variational relaxation of the excited-state electron density showcased promising results for the calculation of charge-transfer excitations, but the complex shape of the electronic hypersurface makes convergence to a specific excited state much more difficult than for the ground state when standard variational techniques are applied. We address the latter aspect by providing suitable initial guesses, which we obtain by two separate constrained algorithms. Combined with the squared-gradient minimization algorithm for all-electrons relaxation in a freeze-and-release scheme (FRZ-SGM), we demonstrate that orbital-optimized density functional theory (OO-DFT) calculations can reliably converge to the charge-transfer states of interest even for large molecular systems. We test the FRZ-SGM method on a phenothiazine-anthraquinone CT excitation in a supramolecular Pd(II) coordination cage complex as a function of the cage conformation. This compound has been studied experimentally prior to our work. We compare this freeze-and-release scheme to two XCF reparameterizations, which were recently proposed as low-cost TD-DFT-based alternatives to variational methods. Two dye-semiconductor complexes, which were previously investigated in the context of photovoltaic applications, serve as a second example to investigate the convergence and stability of the FRZ-SGM approach. Our results demonstrate that FRZ-SGM provides reliable convergence for charge-transfer excited states and avoids variational collapse to lower-lying electronic states, whereas time-dependent DFT calculations with an adequate tuning procedure for the range-separation parameter provide a computationally efficient initial estimate of the corresponding energies, with a computational cost comparable to that of configuration-interaction singles (CIS) calculations.

Bogo, Nicola↗
DOE OSTI2025

Screening Metal Halide Perovskite Solar Modules for Premature Field Failures

Developing metal halide perovskite (MHP) photovoltaic (PV) devices into reliable large-area solar modules could accelerate global solar energy deployment. Many MHP devices are susceptible to degradation under light and elevated temperature (LT). Published research on LT testing is limited at the module level, and LT testing has not yet been developed for qualification testing of commercial PV products. This report assesses whether results of LT testing at moderately elevated temperatures correlate with those of field-tested modules from the same batch. Six batches of samples from four manufacturers are assessed. It is shown that modules with a robust package that can maintain over 80% of their peak efficiency during LT testing at 55 °C for 100 h are more likely to retain over 80% of their peak efficiency during outdoor operation for 10 weeks. This finding is a step towards developing a validated test protocol that could be incorporated into a qualification standard for the commercialization of MHP PV technologies.

14 SOLAR ENERGY↗