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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Dimer Acceptor Adopting a Flexible Linker for Efficient and Durable Organic Solar Cells

Abstract Organic solar cells (OSCs) have advanced rapidly due to the development of new photovoltaic materials. However, the long‐term stability of OSCs still poses a severe challenge for their commercial deployment. To address this issue, a dimer acceptor ( d T9TBO) with flexible linker is developed for incorporation into small‐molecule acceptors to form molecular alloy with enhanced intermolecular packing and suppressed molecular diffusion to stabilize active layer morphology. Consequently, the PM6 : Y6 : d T9TBO‐based device displays an improved power conversion efficiency (PCE) of 18.41 % with excellent thermal stability and negligible decay after being aged at 65 °C for 1800 h. Moreover, the PM6 : Y6 : d T9TBO‐based flexible OSC also exhibits excellent mechanical durability, maintaining 95 % of its initial PCE after being bended repetitively for 1500 cycles. This work provides a simple and effective way to fine‐tune the molecular packing with stabilized morphology to overcome the trade‐off between OSC efficiency and stability.

Chemistry↗
DOE OSTI2021

Low-temperature sprayed SnO x nanocomposite films with enhanced hole blocking for efficient large area perovskite solar cells

Scalable fabrication of charge transport layers with high uniformity and compactness is essential for the commercialization of perovskite solar cells (PSCs). Cost-effective deposition of high-quality electron transport layers (ETLs) is a particularly important step to achieve low-cost, efficient and large-area PSCs. Here, an open-air (relative humidity of 40–50%) and low-temperature (≤100 °C) ultrasonic spray coating of tin oxide (SnO 2 ) nanocomposite films incorporating nanocrystalline SnO 2 nanoparticles in an amorphous SnO x matrix is demonstrated to fabricate large-area ETLs for planar PSCs. The optimized SnO 2 /SnO x nanocomposite exhibits significantly enhanced hole-blocking and high-power conversion efficiencies of 18% and 16% for planar PSCs with an active area of 0.2 cm 2 and 1 cm 2 , respectively. More importantly, the devices show little current–voltage hysteresis as well as good shelf-life stability by maintaining ~90% of the initial performance without encapsulation after 2500 hours storage under inert conditions. Additionally, high voltages of >6.0 V have been obtained for solar modules of 2.1 cm 2 aperture area comprising six sub-cells in series, suggesting that the low-temperature, open-air and fast spray coating is suitable and transferable to deposit large-area charge transport layers for scalable PSCs or other optoelectronic devices.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2022

Versatile Sequential Casting Processing for Highly Efficient and Stable Binary Organic Photovoltaics

Forming an ideal bulk heterojunction (BHJ) morphology is a critical issue governing the photon to electron process in organic solar cells (OSCs). Complementary to the widely-used blend casting (BC) method for BHJ construction, sequential casting (SC) can also enable similar or even better morphology and device performance for OSCs. Here, BC and SC methods on three representative donor:acceptor (D:A) blends are utilized, that is, PM6:PC 71 BM, PM6:IT-4F and PM6:L8-BO. Higher power conversion efficiencies (PCEs) in all cases by taking advantage of beneficial morphology from SC processing are achieved, and a champion PCE of 18.86% (certified as 18.44%) based on the PM6:L8-BO blend is reached, representing the record value among binary OSCs. The observations on phase separation and vertical distribution inspire the proposal of the swelling–intercalation phase-separation model to interpret the morphology evolution during SC processing. Further, the vertical phase segregation is found to deliver an improvement of device performance via affecting the charge transport and collection processes, as evidenced by the D:A-ratio-dependent photovoltaic properties. Besides, OSCs based on SC processing show advantages on device photostability and upscale fabrication. Finally, this work demonstrates the versatility and efficacy of the SC method for BHJ-based OSCs.

14 SOLAR ENERGY↗
DOE OSTI2025

Advances in Carbon Electrode Integration for Stable and Efficient Perovskite Solar Cells and Modules

Carbon-electrode-based perovskite solar cells (C-PSCs) have emerged as a cost-effective and scalable alternative to noble-metal-based PSCs, addressing critical challenges related to device stability, fabrication complexity, and commercialization potential. This review explores the recent progress in C-PSC development, focusing on the benefits of carbon electrodes (CEs), including their hydrophobicity, chemical inertness to halide corrosion, and compatibility with low-temperature cost-effective solution-based deposition methods. Despite relatively lower power conversion efficiencies (PCEs) than their metal (e.g., Au/Ag) counterparts, recent advances in carbon paste formulation, interfacial contact engineering, and work function modification have elevated C-PSC efficiencies above 22%. This review further examines strategies to enhance electrode conductivity, interfacial properties, and charge selectivity to further increase C-PSC performance. Progress in carbon-electrode-based perovskite solar modules (C-PSMs), particularly within mesoporous and planar architectures, is also analyzed, revealing significant developments in active area scaling and long-term stability. Notably, the limited research in inverted (PIN) C-PSCs is also highlighted as a compelling opportunity for innovation, given the architecture's inherent advantages in flexibility, tandem integration, and low-temperature processing. Collectively, these insights affirm the potential of C-PSCs and C-PSMs to deliver affordable, stable, and high-performance photovoltaics suitable for scalable deployment.

Carbon Electrodes↗
DOE OSTI2021

Hot carrier relaxation and inhibited thermalization in superlattice heterostructures: The potential for phonon management

One of the main loss mechanisms in photovoltaic solar cells is the thermalization of photogenerated hot carriers via phonon-mediated relaxation. By inhibiting these relaxation mechanisms and reducing thermalization losses, it may be possible to improve the power conversion efficiency of solar cells beyond the single gap limit. Here, type-II InAs/AlAsSb multi-quantum well (MQW) structures are investigated to study the impact of the phononic properties of the AlAsSb barrier material in hot carrier thermalization. Experimental and theoretical results show that by increasing the barrier thickness (increasing the relative contribution of AlAsSb content in the superlattices), the relaxation of hot carriers is reduced as observed in power-dependent photoluminescence and thermalization analysis. Furthermore, this is attributed to an increase in the phononic bandgap of the MQW with increasing AlAsSb composition reducing the efficiency of the dominant Klemens mechanism as the phononic properties shift toward a more AlSb-like behavior.

14 SOLAR ENERGY↗
DOE OSTI2023

Improving Cooperative Interactions Between Halogenated Aromatic Additives and Aromatic Side Chain Acceptors for Realizing 19.22% Efficiency Polymer Solar Cells

Processing additive plays an important role in the standard operation procedures for fabricating top performing polymer solar cells (PSCs) through efficient interactions with key photovoltaic materials. However, improving interaction study of acceptor materials to high performance halogenated aromatic additives such as diiodobenzene (DIB) is a widely neglected route for molecular engineering toward more efficient device performances. Here, in this work, two novel Y-type acceptor molecules of BTP-TT and BTP-TTS with different aromatic side chains on the outer positions are designed and synthesized. The resulting aromatic side chains significantly enhanced the interactions between the acceptor molecules and DIB through an arene/halogenated arene interaction, which improved the crystallinity of the acceptor molecules and induced a polymorph with better photovoltaic performances. Thus, high power conversion efficiencies (PCEs) of 18.04% and 19.22% are achieved in binary and ternary blend devices using BTP-TTS as acceptor and DIB as additive. Aromatic side chain engineering for improving additive interactions is proved to be an effective strategy for achieving much higher performance photovoltaic materials and devices.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Surface Ligand Management Aided by a Secondary Amine Enables Increased Synthesis Yield of CsPbI 3 Perovskite Quantum Dots and High Photovoltaic Performance

Lead-halide perovskite quantum dots (PQDs) or more broadly, nanocrystals possess advantageous features for solution-processed photovoltaic devices. The nanocrystal surface ligands play a crucial role in the transport of photogenerated carriers and ultimately affect the overall performance of PQD solar cells. Here, significantly improved CsPbI 3 PQD synthetic yield and solar-cell performance through surface ligand management are demonstrated. The treatment of a secondary amine, di- n -propylamine (DPA), provides a mild and efficient approach to control the surface ligand density of PQDs, which has an apparently different working mechanism compared to previously reported surface treatments. Using an optimal DPA concentration, the treatment can simultaneously remove both long-chain insulating surface ligands of oleic acid and oleylamine, even for unpurified PQDs with high ligand density. As a result, the electrical coupling between PQDs is enhanced, leading to improved charge transport, reduced carrier recombination, and a high power conversion efficiency approaching 15% for CsPbI 3 -PQD-based solar cells. In addition, the production yield of CsPbI 3 PQDs can be increased by a factor of 8. These results highlight the importance of developing new ligand-management strategies, specifically for emerging PQDs to achieve scalable and high-performance perovskite-based optoelectronic devices.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Low-dimensional carbon materials decorated FAPbI 3 for carbon-based perovskite solar cells

Carbon nanomaterials are at the forefront of research in perovskite solar cells (PSCs) due to their exceptional electrical, optical, and stability properties. Their diverse applications include serving as interfacial layers, additives, hole and electron transport materials, and back electrodes. While the influence of various low-dimensional carbon nanomaterial structures on crystallinity, optical and electrical performance, and overall device efficiency has been a topic of interest, it has not been thoroughly explored until now. In this study, we effectively integrated carbon quantum dots (CQDs), multi-walled carbon nanotubes (MWCNTs), and graphene into the FAPbI 3 photoactive layer using a two-step sequential deposition method. Our experiments revealed marked improvements in the photovoltaic performance of PSCs that incorporated all three types of carbon nanomaterials. In particular, the data shows significant enhancements in power conversion efficiency, demonstrating the effectiveness of these materials in optimizing device functionality. Notably, MWCNTs distinguished themselves by exhibiting a remarkable potential for enhancing long-term stability. This finding underscores the importance of selecting the right carbon nanomaterials for future PSC developments, paving the way for more reliable and efficient solar energy solutions. As a result, our research highlights the critical role of carbon nanomaterials in advancing perovskite solar technology.

14 SOLAR ENERGY↗
DOE OSTI2020

Secondary Ion Mass Spectrometry (SIMS) for Chemical Characterization of Metal Halide Perovskites

Metal halide perovskite (MHP) solar cells have attracted much attention due to the rapidly growing power conversion efficiency that has reached 25.2% in a decade, comparable to established commercial photovoltaic modules. Compositional engineering is one of the most effective methods to boost the performance of MHP solar cells. Further improving the efficiency and the stability of MHP solar cells necessitates good understanding of the chemical–efficiency correlation and the chemical evolution during the degradation of MHP solar cells. In this regard, time-of-flight secondary ion mass spectrometry (ToF-SIMS) is a powerful tool to investigate the chemical aspect of MHPs and has played an important role in advancing the development of MHP optoelectronics. However, up to date, a review that can guide future utilization of ToF-SIMS in the MHP development is missing. In this paper, the capabilities of ToF-SIMS in MHP investigations are summarized and analyzed from simple material synthesis and chemical distribution to more complicated device operation mechanism and stability. The strength of ToF-SIMS in resolving important issues in this field, such as interface composition, ion migration, and degradation in MHP is highlighted. Finally, an outlook with an emphasis on making the utmost of ToF-SIMS in developing MHP devices is provided.

36 MATERIALS SCIENCE↗
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 OSTI2019

Semitransparent Sb 2 S 3 thin film solar cells by ultrasonic spray pyrolysis for use in solar windows

The integration of photovoltaic (PV) solar energy in zero-energy buildings requires durable and efficient solar windows composed of lightweight and semitransparent thin film solar cells. Inorganic materials with a high optical absorption coefficient, such as Sb 2 S 3 (>10 5 cm -1 at 450 nm), offer semitransparency, appreciable efficiency, and long-term durability at low cost. Oxide-free throughout the Sb 2 S 3 layer thickness, as confirmed by combined studies of energy dispersive X-ray spectroscopy and synchrotron soft X-ray emission spectroscopy, semitransparent Sb 2 S 3 thin films can be rapidly grown in air by the area-scalable ultrasonic spray pyrolysis method. Integrated into a ITO/TiO 2 /Sb 2 S 3 /P3HT/Au solar cell, a power conversion efficiency (PCE) of 5.5% at air mass 1.5 global (AM1.5G) is achieved, which is a record among spray-deposited Sb 2 S 3 solar cells. An average visible transparency (AVT) of 26% of the back-contact-less ITO/TiO 2 /Sb 2 S 3 solar cell stack in the wavelength range of 380–740 nm is attained by tuning the Sb 2 S 3 absorber thickness to 100 nm. In scale-up from mm 2 to cm 2 areas, the Sb 2 S 3 hybrid solar cells show a decrease in efficiency of only 3.2% for an 88 mm 2 Sb 2 S 3 solar cell, which retains 70% relative efficiency after one year of non-encapsulated storage. A cell with a PCE of 3.9% at 1 sun shows a PCE of 7.4% at 0.1 sun, attesting to the applicability of these solar cells for light harvesting under cloud cover.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Efficient Organic Solar Cell with 16.88% Efficiency Enabled by Refined Acceptor Crystallization and Morphology with Improved Charge Transfer and Transport Properties

Abstract Single‐layered organic solar cells (OSCs) using nonfullerene acceptors have reached 16% efficiency. Such a breakthrough has inspired new sparks for the development of the next generation of OSC materials. In addition to the optimization of electronic structure, it is important to investigate the essential solid‐state structure that guides the high efficiency of bulk heterojunction blends, which provides insight in understanding how to pair an efficient donor–acceptor mixture and refine film morphology. In this study, a thorough analysis is executed to reveal morphology details, and the results demonstrate that Y6 can form a unique 2D packing with a polymer‐like conjugated backbone oriented normal to the substrate, controlled by the processing solvent and thermal annealing conditions. Such morphology provides improved carrier transport and ultrafast hole and electron transfer, leading to improved device performance, and the best optimized device shows a power conversion efficiency of 16.88% (16.4% certified). This work reveals the importance of film morphology and the mechanism by which it affects device performance. A full set of analytical methods and processing conditions are executed to achieve high efficiency solar cells from materials design to device optimization, which will be useful in future OSC technology development.

Zhu, Lei↗
DOE OSTI2021

Stabilizing perovskite-substrate interfaces for high-performance perovskite modules

The interfaces of perovskite solar cells (PSCs) are important in determining their efficiency and stability, but the morphology and stability of imbedded perovskite-substrate interfaces have received less attention than have top interfaces. We found that dimethyl sulfoxide (DMSO), which is a liquid additive broadly applied to enhance perovskite film morphology, was trapped during film formation and led to voids at perovskite-substrate interfaces that accelerated the film degradation under illumination. Partial replacement of DMSO with solid-state carbohydrazide reduces interfacial voids. A maximum stabilized power conversion efficiency (PCE) of 23.6% was realized for blade-coated p-type/intrinsic/n-type (p-i-n) structure PSCs with no efficiency loss after 550-hour operational stability tests at 60°C. The perovskite mini-modules showed certified PCEs of 19.3 and 19.2%, with aperture areas of 18.1 and 50.0 square centimeters, respectively.

Chen, Shangshang↗
DOE OSTI2021

Polymer Solar Cells with 18.74% Efficiency: From Bulk Heterojunction to Interdigitated Bulk Heterojunction

The most popular approach to fabricating organic solar cells (OSCs) is solution processing a mixture of donor (D) and acceptor (A) materials into an active layer with a bulk heterojunction (BHJ) nanostructure. In this work, it is demonstrated that the interdigitated heterojunction (IHJ) is a more suitable nanostructure of the active layer for high-performance OSCs whereas it is a long standing challenge to realize well-defined IHJ structures. Here, a facile and versatile sequential solution processing method is developed to produce an IHJ nanostructure with power conversion efficiency reaching 18.74% (18.10% for BHJ the counterpart) by fabricating a donor film with nanopores created by a wax additive, sequentially casting the acceptor on top of infiltrating the nanopores. Compared to the BHJ, the IHJ structure with an interpillar distance within the exciton diffusion length can afford a large bulk D/A interface for efficient exciton dissociation with a minimized charge recombination while free electrons and holes can transport to the respective electrodes through more straightforward pathways, thus enhance performance. Furthermore, the D or A phase in the IHJ device contacts with only one electrode, which can prevent shunting between the anode and cathode and facilitate the industrial mass production of OSCs.

36 MATERIALS SCIENCE↗
DOE OSTI2024

A Difluoro‐Methoxylated Ending‐Group Asymmetric Small Molecule Acceptor Lead Efficient Binary Organic Photovoltaic Blend

Abstract Developing a new end group for synthesizing asymmetric small molecule acceptors (SMAs) is crucial for achieving high‐performance organic photovoltaics (OPVs). Herein, an asymmetric small molecule acceptor, BTP‐BO‐4FO, featuring a new difluoro‐methoxylated end‐group is reported. Compared to its symmetric counterpart L8‐BO, BTP‐BO‐4FO exhibits an upshifted energy level, larger dipole moment, and more sequential crystallinity. By adopting two representative and widely available solvent additives (1‐chloronaphthalene (CN) and 1,8‐diiodooctane (DIO)), the device based on PM6:BTP‐BO‐4FO (CN) photovoltaic blend demonstrates a power conversion efficiency (PCE) of 18.62% with an excellent open‐circuit voltage (V OC ) of 0.933 V, which surpasses the optimal result of L8‐BO. The PCE of 18.62% realizes the best efficiencies for binary OPVs based on SMAs with asymmetric end groups. A series of investigations reveal that optimized PM6:BTP‐BO‐4FO film demonstrates similar molecular packing motif and fibrillar phase distribution as PM6:L8‐BO (DIO) does, resulting in comparable recombination dynamics, thus, similar fill factor. Besides, it is found PM6:BTP‐BO‐4FO possesses more efficient charge generation, which yields betterV OC –J SC balance. This study provides a new ending group that enables a cutting‐edge efficiency in asymmetric SMA‐based OPVs, enriching the material library and shed light on further design ideas.

Chemistry↗
DOE OSTI2022

Kinetic processes of phase separation and aggregation behaviors in slot-die processed high efficiency Y6-based organic solar cells

Morphological optimization has proved to be one crucial factor contributing to the 19% efficiency of Y6-based organic solar cells (OSCs). Although the relationship between component miscibility and film morphology has been established, it has not been clarified how the film formation processes proceed, especially for methods compatible with large-area fabrication, i.e. slot-die coating, which restricts the further optimization of the morphology. Herein, we comprehensively investigate the effect of miscibility and the film-formation kinetic process on film morphology during processing with different solvents. A highest power conversion efficiency (PCE) of 17.38% can be obtained in a D18:Y6 device processed with slot-die coating in an open-air environment. However, due to their relatively poor miscibility, incorporating a trace amount of chlorobenzene (CB) into CF can sufficiently promote Y6 aggregation, leading to increased phase separation and thus the average PCE drops to 15.16%. In contrast, a PM6:Y6 blend shows insensitive changes in the kinetic process as well as the final morphology, and thus in the comparable PCEs when cast with different solvents, which is ascribed to their relatively good miscibility. As a result, this work provides scientific guidelines for device optimization by combining the intermediate gap from miscibility to kinetic process and their impact on final morphology.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Predicting Device Parameters for Dye-Sensitized Solar Cells from Electronic Structure Calculations to Reproduce Experiment.

Given that improvements to the power-conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs) have slowed in recent years, a means to accurately predict the device parameters yielded by trial dyes in silico, without having to synthesize them, would be extremely valuable to speed up the design process. Currently, the best-performing methods of calculating device parameters rely on a set of experimentally determined kinetic coefficients. In practice, it is very difficult to measure these kinetic parameters accurately, limiting the overall accuracy of such predictive methods. This work proposes a model to obtain key parameters such as J(SC), V-OC, and PCE using only the results from density functional theory (DFT) and time-dependent DFT calculations, noting that rates of electron-transfer steps are ultimately linked to the electronic structure of the dye center dot center dot center dot TiO2 working electrode. Six organic DSSC dyes from dissimilar chemical classes (L0, L1, L2, WS-2, WS-92, and C281) were chosen to demonstrate the power of this approach. Their a priori known experimentally determined device performance metrics served to validate our predictions. The greatest absolute error in our predicted PCE values was 0.36% relative to the experiment, while the greatest fractional error was 0.042. This indicates that the proposed model offers a dramatic improvement on previous predictive methods for DSSC device parameters, both in accuracy and in consistency. Moreover, such a predictive model has great potential to be applied to other photovoltaic applications, further enabling the design of novel, highly efficient photoactive materials.

density functional theory↗
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↗