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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Phase-stabilized 2D/3D hetero-bilayers via lattice matching for efficient and stable inverted solar cells

2D-on-3D (2D/3D) perovskite heterostructures with engineered energy landscapes offer the potential to realize efficient and stable inverted solar cells. However, managing the energy landscape using 2D perovskites with thicker inorganic layers n > 1 necessitates the usage of the chemically unstable methylammonium MA + . Here, we synthesized formamidinium (FA)-rich and pure-FA n = 3 Ruddlesden-Popper (RPP) and Dion-Jacobson perovskite (DJP) single crystals by identifying ligands with suitably lattice-matched organic and inorganic components of the 2D lattice. These crystals were translated onto 3D perovskites as capping layers, forming 2D/3D hetero-bilayers (HBs). Degradation studies revealed that HBs with butylammonium-based RPPs as capping layers rapidly phase segregate into non-perovskites under combined extrinsic stressors, compromising the underlying 3D layer, whereas FA-rich DJPs based on 3-aminomethylpiperidine retain their phase stability. The DJP HBs also possess a favorable energy landscape and electron transport at the 2D/3D interface, enabling inverted solar cells with a champion PCE of 25.33% and remarkable stability.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2024

Repowering and Retrofitting of Solar Inverters: A Field Case Study [Slides]

A handful of large-scale photovoltaic (PV) plants have undergone retrofitting and/or repowering of inverters for a variety of reasons, such as rapid product life-cycle innovations with lack of reverse compatibility, original equipment manufacturers (OEMs) exiting the inverter business, weather damage, more lucrative revenue opportunities driven by high contractual offtake price, and so on. Insights has been collected via expert elicitation and relevant staff involved in these retrofitting/repowering at the case study site. Selecting and installing inverters from a different OEM at the commercially operating PV plant provides a unique opportunity to thoroughly document inverter retrofitting/repowering. The case study describes compatibility of mechanical, electrical, communications, and other important aspects. The goal is to provide a public case study that improves the general knowledge of the solar industry about what is involved in repowering/retrofitting a PV plant and how others can best prepare.

14 SOLAR ENERGY↗
DOE OSTI2025

Electrostatically Enhanced Buried Interface Binding of Self‐Assembled Monolayers for Efficient And Stable Inverted Perovskite Solar Cells

Inverted p‐i‐n structure perovskite solar cells (PSCs) have outperformed traditional n‐i‐p PSCs in recent years. A key advancement is the use of self‐assembled monolayers (SAMs) as hole transport layers. One class of widely used SAMs is carbazole‐based phosphonic acids. However, it is found that these SAMs lack strong binding with transparent conducting oxides (TCO) and perovskite. The weak binding strength results in suboptimal interfacial adhesion of the buried interface, which limits the device's stability. Here, interfacial binding is enhanced by increasing the dipole moment that creates a strong interfacial electric field that enhances electrostatic interactions at the TCO/perovskite interface, while incorporating tailored functional groups in SAMs to improve chemical anchoring to TCO and binding to perovskite. Specifically, the donor‐acceptor SAM molecule 4‐(7‐(4‐(bis(4‐methoxyphenyl)amino)‐2,5‐difluorophenyl)benzo[c][1,2,5]thiadiazol‐4‐yl)benzoic acid (PAFTB) is employed, which features an enhanced dipole moment along with electron‐donating and electron‐withdrawing functional groups to optimize interfacial interactions. Compared to extensively used [2‐(9H‐carbazol‐9‐yl)ethyl]phosphonic acid (2PACz), PAFTB enhances total interfacial adhesion by 2.8 times, thereby improving the thermal stability of the layer. Using this approach, PSCs are demonstrated with a certified quasi‐steady‐state power conversion efficiency of 24.9% and maintain 80% of the initial efficiency after 900 h of maximum power point tracking at 85 °C.

Interfacial adhesion↗
DOE OSTI2024

In situ energetics modulation enables high-efficiency and stable inverted perovskite solar cells

In contrast to conventional (n-i-p) perovskite solar cells (PSCs), inverted (p-i-n) PSCs offer enhanced stability and integrability with tandem solar cell architectures, which have garnered increasing interest. However, p-i-n cells suffer from energy level misalignment with transport layers, imbalanced transport of photo-generated electrons and holes, and significant defects with the perovskite films. Here we introduce tris(2,4,6-trimethyl-3-(pyridin-3-yl)phenyl)borane (3TPYMB), a nonionic n-type molecule that, through hydrogen bonding and Lewis acid-base reactions with perovskite surfaces or grain boundaries, enables in situ modulation of perovskite energetics, effectively mitigating the key challenges of p-i-n PSCs. The p-i-n PSCs incorporating 3TPYMB achieve a certified quasi-steady-state power conversion efficiency of 24.55 +- 0.33%, with a reverse scan efficiency of 25.58%. Finally, they also exhibit exceptional stability, with unencapsulated devices retaining 97.8% of their initial efficiency after 1,800 h of continuous operation at maximum power point under N 2 atmosphere, 1 sun illumination and 60 °C conditions.

14 SOLAR ENERGY↗
DOE OSTI2025

C60-Based Ionic Salt Electron Shuttle for High-Performance Inverted Perovskite Solar Modules

Although C60 is usually the electron transport layer (ETL) in inverted perovskite solar cells, its molecular nature of C60 leads to weak interfaces that lead to non-ideal interfacial electronic and mechanical degradation. Here, we synthesized an ionic salt from C60, 4-(1',5'-dihydro-1'-methyl-2'H-[5,6] fullereno-C60-Ih-[1,9-c]pyrrol-2'-yl) phenylmethanaminium chloride (CPMAC), and used it as the electron shuttle in inverted PSCs. The CH2-NH3+ head group in the CPMA cation improved the ETL interface and the ionic nature enhanced the packing, leading to ~3-fold increase in the interfacial toughness compared to C60. Using CPMAC, we obtained ~26% power conversion efficiencies (PCEs) with ~2% degradation after 2,100 hours of 1-sun operation at 65degrees C. For minimodules (four subcells, 6 centimeters square), we achieved the PCE of ~23% with <9% degradation after 2,200 hours of operation at 55degrees C.

14 SOLAR ENERGY↗
DOE OSTI2026

Elucidating Compositional Differences in Halide Perovskites for Normal and Inverted Perovskite Solar Cells

Over the recent few years, extensive research efforts have shifted from normal (n-i-p) to inverted (p-i-n) perovskite solar cells (PSCs), owing to their promising efficiency and operational stability, enabled by low-temperature processing. Despite a fundamentally identical operation principle (only structurally inverted), the optimized perovskite compositions for normal and inverted PSCs differ significantly across the literature, suggesting an underlying design principle for perovskite composition. Here, we unveil the role of cesium cation in enhancing interfacial contact between the perovskite layer and the underlying hole-transporting layer (HTL) in inverted PSCs. Comprehensive in situ and device characterization reveal that cesium incorporation promotes the formation of initial nucleation seeds for heterogeneous nucleation at the perovskite/hydrophobic HTL interface, thereby improving their contact. The resulting compositional heterogeneity explains the focus of recent studies on resolving this issue. This study provides mechanistic insight into designing perovskite compositions to further enhance the performance and longevity of PSCs.

Park, Keonwoo↗
DOE OSTI2025

Open-air spray deposition of PCBM/BCP electron transport layer for inverted perovskite solar cells

A [6,6]-phenyl C61 butyric acid methyl ester (PCBM) and bathocuproine (BCP) electron transport layer (ETL) is spray deposited in open air directly on top of a perovskite at linear speeds of 9 m/min. The PCBM precursor ink contains a binary mixture of 1:1 chlorobenzene:chloroform, which optimizes spray wettability on the perovskite surface and allows quick solvent evaporation. A near-infrared heating module additionally provides a flash cure (<5 s) for the formation of smooth, large-area PCBM films (∼20 cm 2 ). A BCP solution in isopropanol is subsequently sprayed to form an ultrathin (<5 nm) film and characterized with a suite of high-resolution metrologies. The spray-deposition processing and near-infrared treatment do not damage the underlying perovskite. Inverted architecture devices containing the sprayed ETL achieve a champion efficiency of 20.3% and demonstrate stable performance without additional interlayers or surface treatments. Here, the technoeconomic cost of the open-air spray process is compared against traditional vacuum-based evaporation, resulting in a decrease in manufacturing costs by 26%.

14 SOLAR ENERGY↗
DOE OSTI2024

Advanced grid-forming (GFM) inverter controls, modeling and system impact study for inverter dominated grids

Our main goals in this project are to understand: 1) the stability of the power system with very high penetration of PV or other inverter-based resources (IBR), 2) the interactions among IBRs and traditional generators, and 3) the impact of the GFM inverters on bulk power system. To achieve these goals, we took a holistic research and development approach. First, an impedance-based large system modeling and stability analysis tool was developed to aid the large IBR system small-signal stability analysis. Second, consensus-based control and transient overload ride through were developed to control and coordinate multiple GFM inverters in a large system to maintain transient stability during big grid events. Third, high fidelity electromagnetic transient (EMT) IBR models were developed and integrated into a large reduced WECC model to study the system impact from IBRs. Lastly, extensive validation tests of the GFM control which was developed in this project and implemented in two 1MW commercial solar inverters were performed using different validation platforms, e.g., control hardware-in-the-loop (CHIL) platform, power hardware- in-the-loop (PHIL) platform, and a real PV plant.

14 SOLAR ENERGY↗
DOE OSTI2024

Spatial-Temporal PV Hosting Capacity Estimation and Evaluation

Evaluating Photovoltaic Hosting Capacity (PVHC) is an essential step in the process of integrating solar energy into power grids, particularly when focusing on the distribution network (DN) as the primary integration target. PVHC needs to be investigated, especially in cases where the grids are unbalanced, and their operational conditions vary spatially and temporally. This motivation prompted us to propose a scalable model tailored to this application. In this paper, we applied linearization to the alternating current optimal power flow (AC-OPF) and solar inverters, transforming the original problem into a mixed-integer linear programming (MILP) problem. Additionally, we accounted for the battery energy storage system (BESS) as a time-coupling factor for calculating PVHC. We then compared the PVHC results between the IEEE-13 bus and SMART-DS San Francisco (SFO) cases and discussed the extent to which BESS can enhance the PVHC of a DN. Furthermore, we designed a web-based graphical visualization for the SFO case, enabling user interaction with raw data and simulation results on a map through a graphical user interface (GUI). In summary, our results and findings provide valuable insights for future three-phase unbalanced AC-OPF PVHC practices and their visualization.

AC-optimal power flow↗
DOE OSTI2026

Cyber Labeling for Energy Industrial IoT

The U.S. Department of Energy’s (DOE) Office of Cybersecurity, Energy Security and Emergency Response (CESER), at the request of the Deputy National Security Advisor for Cyber and Emerging Technologies, Anne Neuberger, initiated research in 2023 to develop a cybersecurity labeling proof-of-concept for energy products to expand on the Federal Communications Commission’s (FCC) proposed U.S. Cyber Trust Mark program. DOE mobilized researchers from six National Laboratories to develop and gather feedback on a proof-of concept label for solar inverters and smart meters, which serve as representative products for market-facing energy sector Industrial Internet of Things (IIoT). This report details the research team’s process across two phases and the resulting findings, which include challenges facing cyber labeling programs and recommendations to implement an expanded IIoT cyber labeling program in the U.S.

32 - ENERGY CONSERVATION, CONSUMPTION, AND UTILIZA↗
DOE OSTI2025

1.1 eV GaInAs Cell Development for Dual-Use Solar and 1070 nm Laser Power Converters

Dual-use photovoltaic cells can receive solar and laser power simultaneously to generate current, an application relevant to space and terrestrial industries. This study investigates two concepts of solar cells optimized for dual-use 1070 nm laser and solar power conversion, a single-junction and triple-junction cell. The cell designs are based upon the 3- junction inverted metamorphic solar cell, previously shown highly efficient for solar conversion. Because it is closely bandgap-tuned for a 1070 nm laser, the 1 eV bottom junction is incorporated into each of the two designs, making its development key to the success of both concepts. However, each design requires some modification for efficient dual use. The single-junction device requires optimization to reduce short wavelength absorption of the broad solar spectrum. In both devices, the graded buffer layers in the GaInAs cell affect the cell's performance by reducing threading dislocations in the active junction. However, the buffer in the three-junction device also acts as a lateral transport layer and so affects the fill factor depending on its sheet resistance. By varying the buffer thickness, we demonstrate a direct relationship between buffer thickness and sheet resistance reduction, while considering implications to open-circuit voltages. We also performed resistance modeling to determine the optimal grid spacing and thickness of the grid fingers to minimize losses due to sheet resistance and grid shading. Efficiency data for a one junction GaInAs cell demonstrates a laser conversion efficiency of 38% at 1070 nm wavelength without an anti-reflection coating.

dual-use↗
DOE OSTI2024

Solar Energy Extension Project

The town of Stratford plans to develop and own a 6 kilowatt (kW) solar array on the roof of a municipal-owned public pavilion on the town green. A SolarEdge level 2 EV charging station will be installed at the pavilion to be used by the public. The charging station will have one charging port. The town will install 3 air source heat pumps in the library located adjacent to the pavilion to reduce the use of propane to heat the library. The town will install 4 air source heat pumps in the Town Hall to reduce the use of #2 heating oil to heat the facility. The 6 kW solar array will provide electricity to the library to offset electricity usage, and when an EV plugs into the charging station the solar will provide electricity to the charging station. There is no ground disturbance or ground trenching associated with this project. The 6 kW solar array on the roof of the pavilion will include 20 (390) watt all black panels. A SolarEdge level 2 EV charger will be installed at the pavilion with the 240 V inverter. The solar array will provide electricity to the library and when a vehicle plugs into the EV charger the solar array will switch to power the charger. Any excess electricity that is generated by the array and not used by the library or the EV charger will be fed onto the grid and the town will receive a net metering credit applied towards future consumption. There is no ground disturbance associated with the EV charger or solar array, and the town will install signage to direct the public to the charger. The library will install 2 (18,000) BTU ductless air source heat pumps and 1 (24,000) BTU unit. This will significantly reduce the amount of propane required to heat the library. The Town Hall will install 2 (36,000) BTU ductless air source heat pumps and 2 (9,000) BTU units to reduce the amount of #2 heating oil required to heat the building.

14 SOLAR ENERGY↗
DOE OSTI2026

Nanoscale Amorphization of Poly(Triarylamine) for Efficient and Stable Inverted Perovskite Photovoltaics

Perovskite solar modules require hole-selective layers that combine efficient charge extraction, interfacial uniformity and scalable processing. Poly(triarylamine) (PTAA) is widely used in high-performance inverted perovskite photovoltaics, but its nanoscale crystallization and aggregation on indium tin oxide can disrupt film continuity, increase interfacial recombination and limit module stability. Here we show that 4-fluorobenzylphosphonic acid (4FBPA) modifies the surface of indium tin oxide to induce nanoscale amorphization of PTAA, forming a uniform sub-10-nm hole-selective layer. The molecule binds to indium tin oxide through a dehydration reaction, tunes the work function and surface free energy of the photoanode, and improves energy-level alignment with PTAA. The resulting amorphous PTAA film shows enhanced conductivity and hole extraction, suppresses non-radiative recombination at the buried interface and promotes more uniform perovskite growth. Inverted perovskite solar cells reach a power conversion efficiency of 26.63%, while blade-coated modules achieve a certified quasi-steady-state efficiency of 23.01%. The modules retain 95.9% of their initial efficiency after 2,600 hours of maximum-power-point operation under 1-sun illumination at 65 +- 5 degrees C in nitrogen. These results identify nanoscale amorphization of polymeric hole-selective layers as a route to efficient and stable inverted perovskite photovoltaics.

14 SOLAR ENERGY↗
DOE OSTI2024

Analysis of Supply Chain Challenges in the U.S. Solar Industry: Focus on Build America, Buy America Act and Inverter Supply Issues

The United States (U.S.) solar industry has been undergoing significant transformation, driven largely by meeting U.S. climate goals while simultaneously maintaining national security. At the forefront of this movement is the Inflation Reduction Act (IRA) and the Build America, Buy America (BABA) Act. The IRA has driven investment in clean energy generation deployments while the BABA Act, enacted under Division G, Title IX of the Infrastructure Investment and Jobs Act (IIJA) establishes domestic content procurement preference for all federal financial assistance obligated for infrastructure projects. While these pieces of legislation aim to reduce reliance on foreign-made solar components and increase domestic production, the sector continues to face notable supply chain challenges. These are particularly pronounced with inverters, a critical component in solar photovoltaic (PV) systems. This report explores the current state of these supply chain challenges, with a specific focus on the impact of the BABA requirements and the associated complexities in inverter manufacturing and supply.

14 SOLAR ENERGY↗
DOE OSTI2025

Secure and Resilient Operations Using Open-Source Distributed Systems Platform (OpenDSP)

The goal of this project is to identify and address cybersecurity gaps by developing a multi-layer multi-channel cyber-physical defense and survival mechanism for operating distribution networks with high penetration of solar / inverter-based resource (IBR) / distributed energy resource (DER). The proposed security enhancements are built upon the distributed framework and solution architecture for both information technology (IT) and operational technology (OT) systems. The technical solutions consist of two composite functionalities and six layers: proactive defense (vulnerability assessment, communication protection, and attack detection, as layers 1-3), and adaptive self-healing (attack-resilient control, adaptive recovery, and resilient survival, as layers 4-6). These layers, built on and extended from DHS CISA Cyber Framework, establish an integrated and robust cybersecurity framework for operating large-scale distribution networks.

14 SOLAR ENERGY↗
DOE OSTI2025

Utility-Scale Operational Consequences for Solar Grid Services

This report delves into the critical aspects of grid services provided by solar inverter-based resources (IBRs), with an emphasis on the evolving landscape of microgrids, virtual power plants (VPPs), aggregators, and distributed energy resource management systems (DERMS). As the energy sector undergoes a transformative shift towards more decentralized and resilient grid architectures, understanding the multifaceted risks associated with these technologies becomes paramount. The report categorizes these risks into organizational, technical, and procedural domains, providing a thorough risk assessment framework that stakeholders can utilize to anticipate and mitigate potential issues. In addressing the increasing complexity of grid interconnections, the report highlights the importance of Cyber-Informed Engineering (CIE). By embedding engineering controls and cybersecurity measures into the early stages of system design, this approach aims to fortify grid infrastructure against emerging cyber threats. The analysis includes an exploration of best practices and strategies for integrating CIE principles to enhance grid security and resilience. To provide practical insights, the report conducts a detailed consequence analysis of various grid services and cyber mitigations that can be applied through the interconnection process. This analysis evaluates the potential impacts of different failure modes and vulnerabilities, offering a clear understanding of the consequences that could arise from disruptions within the energy grid. The findings are further enriched by a series of case studies that illustrate real-world scenarios and lessons learned from past incidents. Through this comprehensive examination of grid services and their criticality, the report aims to prepare industry professionals with the knowledge and tools necessary to navigate the complexities of modern energy systems. By providing a comprehensive approach that includes risk assessment, cybersecurity, and consequence analysis, solar stakeholders can more effectively guarantee the reliability, efficiency, and security of the energy grid.

14 SOLAR ENERGY↗
DOE OSTI2025

An Optimized H5 Hysteresis Current Control with Clamped Diodes in Transformer-Less Grid-PV Inverter

With the rise of renewable energy penetration in the grid, photovoltaic (PV) panels are connected to the grid via inverters to supply solar energy. Transformer-less grid-tied PV inverters are gaining popularity because of their improved efficiency, reduced size, and lower costs. However, they can induce a path for leakage currents between the PV and the grid due to the absence of galvanic isolation. This leads to serious electromagnetic interference, loss in efficiency, and safety concerns. The leakage current is primarily influenced by the nature of the common mode voltage (CMV), which is determined by the switching techniques of the inverter. In this paper, a novel inverter topology of Hysteresis Controlled H5 with Two Clamping Diodes (HCH5-D2) is derived. The HCH5-D2 topology helps decouple the AC part (Grid) and DC part (PV) during the freewheeling period to make the CMV constant, thereby reducing the leakage current. Additionally, the extra diodes help reduce voltage spikes generated during the freewheeling period and maintain the CMV at a constant value. Finally, a 2.2 kW grid-connected single-phase HCH5-D2 PV inverter system’s MATLAB simulation is presented, showing better results compared to a traditional H4 inverter.

42 ENGINEERING↗