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NASA NTRS2007

Advanced Stirling Convertor Testing at NASA Glenn Research Center

The U.S. Department of Energy (DOE), Lockheed Martin Space Systems (LMSS), Sunpower Inc., and NASA Glenn Research Center (GRC) have been developing an Advanced Stirling Radioisotope Generator (ASRG) for use as a power system on space science and exploration missions. This generator will make use of the free-piston Stirling convertors to achieve higher conversion efficiency than currently available alternatives. The ASRG will utilize two Advanced Stirling Convertors (ASC) to convert thermal energy from a radioisotope heat source to electricity. NASA GRC has initiated several experiments to demonstrate the functionality of the ASC, including: in-air extended operation, thermal vacuum extended operation, and ASRG simulation for mobile applications. The in-air and thermal vacuum test articles are intended to provide convertor performance data over an extended operating time. These test articles mimic some features of the ASRG without the requirement of low system mass. Operation in thermal vacuum adds the element of simulating deep space. This test article is being used to gather convertor performance and thermal data in a relevant environment. The ASRG simulator was designed to incorporate a minimum amount of support equipment, allowing integration onto devices powered directly by the convertors, such as a rover. This paper discusses the design, fabrication, and implementation of these experiments.

Oriti, Salvatore↗

NASA NTRS2007

Advanced Stirling Convertor Testing at NASA Glenn Research Center

Oriti, Salvatore M.↗

NASA NTRS2013

Feasibility of Traveling Wave Direct Energy Conversion of Fission Reaction Fragments

Fission fragment direct energy conversion has been considered in the past for the purpose of increasing nuclear power plant efficiency and for advanced space propulsion. Since the fragments carry electric charge (typically in the order of 20 e) and have 100 MeV-range kinetic energy, techniques utilizing very high-voltage DC electrodes have been considered. This study is focused on a different approach: the kinetic energy of the charged fission fragments is converted into alternating current by means of a traveling wave coupling scheme (Traveling Wave Direct Energy Converter, TWDEC), thereby not requiring the utilization of high voltage technology. A preliminary feasibility analysis of the concept is introduced based on a conceptual level study and on a particle simulation model of the beam dynamics.

Tarditi, A. G.↗

DOE OSTI2017

Highly Efficient Photocatalytic Water Splitting over Edge-Modified Phosphorene Nanoribbons

Two-dimensional phosphorene with desirable optoelectronic properties (ideal band gap, high carrier mobility, and strong visible light absorption) is a promising metal-free photocatalyst for water splitting. However, the band edge positions of the valence band maximum (VBM) and conduction band maximum (CBM) of phosphorene are higher than the redox potentials in photocatalytic water splitting reactions. Here, phosphorene can only be used as the photocathode for hydrogen evolution reaction as a low-efficiency visible-light-driven photocatalyst for hydrogen production in solar water splitting cells. Here, we propose a new mechanism to improve the photocatalytic efficiency of phosphorene nanoribbons (PNRs) by modifying their edges for full reactions in photocatalytic water splitting. By employing first-principles density functional theory calculations, we find that pseudohalogen (CN and OCN) passivated PNRs not only show desired VBM and CBM band edge positions induced by edge electric dipole layer, but also possess intrinsic optoelectronic properties of phosphorene, for both water oxidation and hydrogen reduction in photocatalytic water splitting without using extra energy. Furthermore, our calculations also predict that the maximum energy conversion efficiency of heterojunction solar cells consisting of different edge-modified PNRs can be as high as 20% for photocatalytic water splitting.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2016

Multifluid geo-energy systems: Using geologic CO 2 storage for geothermal energy production and grid-scale energy storage in sedimentary basins

We present an approach that uses the huge fluid and thermal storage capacity of the subsurface, together with geologic carbon dioxide (CO 2 ) storage, to harvest, store, and dispatch energy from subsurface (geothermal) and surface (solar, nuclear, fossil) thermal resources, as well as excess energy on electric grids. Captured CO 2 is injected into saline aquifers to store pressure, generate artesian flow of brine, and provide a supplemental working fluid for efficient heat extraction and power conversion. Concentric rings of injection and production wells create a hydraulic mound to store pressure, CO 2 , and thermal energy. This energy storage can take excess power from the grid and excess/waste thermal energy, and dispatch that energy when it is demanded and thus enable higher penetration of variable renewable energy technologies (e.g., wind, solar). CO 2 stored in the subsurface functions as a cushion gas to provide enormous pressure-storage capacity and displace large quantities of brine, some of which can be treated for a variety of beneficial uses. Geothermal power and energy-storage applications may generate enough revenues to compensate for CO 2 capture costs. While our approach can use nitrogen (N 2 ), in addition to CO 2 , as a supplemental fluid, and store thermal energy, this study focuses using CO 2 for geothermal energy production and grid-scale energy storage. We conduct a techno-economic assessment to determine the levelized cost of electricity of using this approach to generate geothermal power. We present a reservoir pressure-management strategy that diverts a small portion of the produced brine for beneficial consumptive use to reduce the pumping cost of fluid recirculation, while reducing the risk of seismicity, caprock fracture, and CO 2 leakage.

15 GEOTHERMAL ENERGY↗

DOE OSTI2025

A Comparison Between Industrial Energy Efficiency Measures in Guatemala and the United States

Energy auditing has been cited as a key tool in closing the gap between the actual energy consumption in industrial facilities and what should be at an environmentally sustainable level. Several factors affect the likelihood that energy audits will be effective in closing that gap, and more analysis is needed to understand these factors, especially for developing nations. This study compares three energy efficiency measures (EEMs) frequently recommended in both the United States and Guatemala, namely, installing solar panels to generate electricity, installing higher-efficiency lighting, and upgrading to premium efficiency motors. The implementation of each of these EEMs contributes to more sustainable energy consumption, and each of these EEM’s payback periods is affected by capital costs, energy costs, and other local factors analyzed in this study. Projected payback periods for each EEM based on Guatemalan and U.S. capital cost and energy cost ranges are assessed via EEM-specific payback period calculations and compared to the energy audit data from each country. While lower capital costs incentivize EEM implementation and reduce payback periods, there is an interplay between energy cost and capital cost that impacts the trends in the U.S. and Guatemala. As in the case of the solar panel installation EEM, though Guatemalan companies pay ~110% more for electricity than U.S. companies, when Guatemalan capital costs are lower, payback periods are lower than in the U.S. Conversely, in cases where Guatemalan capital costs are higher—as for higher-efficiency lighting and motor installation—Guatemalan payback periods are roughly the same as those in the U.S. because of the higher Guatemalan energy costs.

Khosla, Radhika↗

DOE OSTI2020

Microreactor Agile Nonnuclear Experimental Testbed Test Plan

Microreactors are an attractive technology option for kick-starting nuclear innovation if they can be operated at high temperature, yielding high power conversion thermal efficiencies comparable or better than in commercial light water reactors. Microreactors are currently the smallest variation of Small Modular Reactors (SMRs). SMRs are “newer generation reactors designed to generate electric power up to 300 MWe and whose components and systems can be shop-fabricated and then transported as modules to the sites for installation as demand arises.” (IAEA, 2016). Vendors are developing microreactor designs to provide an affordable, potentially mobile source of electricity - see Fig. 1 for an example of a microreactor on a semi-truck. Various microreactor designs are possible including heat pipe- and gascooled options, which are the focus of the nonnuclear testing described in this document. In heat pipe microreactors, high-temperature heat pipes using liquid sodium or potassium working fluid transport fission heat from the core to a heat removal section which in turn transfers heat to the power conversion system working fluid. In a gas-cooled design, He or other gas will flow through a solid monolith of material and transfer heat as the temperature of the gas increases through a heat exchanger to a power conversion unit. The logistics of all these processes will be examined and tested through a series of articles at the nonnuclear test bed at Idaho National Laboratory (INL), the Microreactor Agile Nonnuclear Experiment Testbed (MAGNET) facility. Microreactors designed to produce power of 0.1-20 MWt offer the potential for more affordable nuclear energy for a range of applications. In a heat pipe microreactor, heat pipes, fuel rods, and/or moderator are intermixed in the reactor core assembly. Heat pipes extend from the core region into the heat removal section where the power conversion unit working fluid flows through holes or channels, transferring heat from the heat pipes to the working fluid. In a gas-cooled microreactor, gas flows through the solid monolith region and up into the heat exchanger region, transferring heat to the working fluid. For initial testing, the heat removal working fluid can be a low pressure gas for testing that addresses thermal stresses. In the final application, heat addition to the power conversion working fluid typically occurs at high pressure, supporting operation of an air-Brayton, supercritical CO 2 (SCO2), or He-recuperated Brayton cycle. Various stages of the steps above will be demonstrated through the tests described in this report.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

DOE OSTI2026

Buried Interfaces in Organic Photocathodes for H 2 Evolution: Fermi-Level Pinning and Recombination

Herein, we demonstrate how Fermi-level pinning at buried contacts impacts solar fuel generation in all-polymer photocathodes by systematically comparing the effects of work function, hydroxyl coverage, and hydrogen evolution using chemically modified indium tin oxide (ITO) supports. Photovoltages and net photocathode performance are improved when the ITO is passivated using phosphonic acids, independent of work function, suggesting that the passivation reduces Fermi-level pinning at the buried interface arising from blended heterojunction interactions with surface metal hydroxyls. Transient photovoltage decay reveals differences in recombination mechanisms, supported by light intensity-dependent measurements. Briefly, nonpassivated, hydrophilic contacts exhibit trap-assisted recombination, while passivated, hydrophobic contacts follow bimolecular recombination. We then investigate changes in electroactivity of hole-transfer processes as a function of scan rate and repetitive cycling using a diffusion-controlled molecular redox probe, analogous to a hole-only device achieved via the electrolyte. The nonpassivated buried contacts exhibit higher overpotentials for oxidation, indicative of hole injection/extraction barriers. We observe irreversible electron transfer via the hole-transport level of the blended heterojunction and a strong cycle dependence, consistent with changes in the hole trap state density. Passivation results in more reversible redox behaviors, consistent with more Ohmic-like contacts. Collectively, these results provide context toward the realization of durable organic photoelectrodes with optimized photovoltages and net solar-to-hydrogen conversion efficiencies via fundamental understanding of the rates of carrier generation, recombination, and transport in high-dielectric aqueous environments and opportunities to characterize buried interfaces under device-relevant electric fields.

buried interfaces↗

DOE OSTI2017

Waste Heat-to-Power Using Scroll Expander for Organic Rankine Bottoming Cycle

The objective of this program was to develop a novel, scalable scroll expander for conversion of waste heat to power; this was accomplished and demonstrated in both a bench-scale system as well as a full-scale system. The expander is a key component in Organic Rankine Cycle (ORC) waste heat recovery systems which are used to convert medium-grade waste heat to electric power in a wide range of industries. These types of waste heat recovery systems allow for the capture of energy that would otherwise just be exhausted to the atmosphere. A scroll expander has the benefit over other technologies of having high efficiency over a broad range of operating conditions. The speed range of the TIAX expander (1,200 to 3,600 RPM) enables the shaft power output to directly drive an electric generator and produce 60 Hz electric power without incurring the equipment costs or losses of electronic power conversion. This greatly simplifies integration with the plant electric infrastructure. The TIAX scroll expander will reduce the size, cost, and complexity of a small-scale waste heat recovery system, while increasing the system efficiency compared to the prevailing ORC technologies at similar scale. During this project, TIAX demonstrated the scroll expander in a bench-scale test setup to have isentropic efficiency of 70-75% and operated it successfully for ~200 hours with minimal wear. This same expander was then installed in a complete ORC system driven by a medium grade waste heat source to generate 5-7 kW of electrical power. Due to funding constraints, TIAX was unable to complete this phase of testing, although the initial results were promising and demonstrated the potential of the technology.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2019

Heat Transfer from Glass Melt to Cold Cap: Gas Evolution and Foaming

In electric melters, the conversion heat is transferred through the foam layer at the cold cap bottom. Understanding cold cap foaming is thus important for enhancing the efficiency of both commercial and waste glass melters as well as for the development of advanced batch-to-glass conversion models. Observing foam behavior “in-situ” is still impossible, i.e., viewing directly in glass melters. To investigate the feed foaming behavior in laboratory conditions, we employed the feed volume expansion test, evolved gas analysis, and thermogravimetry. Combining these techniques helps assess the cold cap bottom temperature that directly influences the temperature gradient at the melt/cold cap interface, and thus the rate of melting. We also discuss the behavior of cavities formed by coalescing primary foam bubbles and ascending secondary bubbles.

Hrma, Pavel R.↗

DOE OSTI2023

Light-Induced Spin Trapping in Transition Metal Compounds (DOE-DE-SC0017889-Final-Report)

In solar cells, devices that convert the energy of light directly into electricity, dye sensitized solar cells (DSSC) are some of the most capable devices for energy conversion. Ruthenium is a key component for these high-power conversion efficiencies in DSSC. Ruthenium, unfortunately, is among one of the rarest elements, and, thus, more earth-abundant replacements are needed. Though the properties of ruthenium are unique, these properties may be possible to mimic with other elements. To do this, the ability to control how other more earth-abundant elements like iron behave is essential. In this work, a method was developed to enable better control over iron species, for example, and their interaction with light.

14 SOLAR ENERGY↗

NASA NTRS1978

A review of the thermoelectronic laser energy converter (TELEC) program at Lewis Research Center

The investigation of the Thermoelectronic Laser Energy Converter (TELEC) concept began with a feasibility study of a 1 megawatt sized TELEC system. The TELEC was to use either cesium vapor or hydrogen as the plasma medium. The cesium vapor TELEC appears to be the more practical device studied with an overall calculated conversion efficiency of greater than 48%. Following this study, a small TELEC cell was fabricated which demonstrated the conversion of a small amount of laser power to electrical power. The cell developed a short circuit current of 0.7 amperes and an open circuit voltage, as extrapolated from volt-ampere curves, of about 1.5 volts.

Alger, D. L.↗

NASA NTRS1978

A review of the Thermoelectronic Laser Energy Converter /TELEC/ Program at Lewis Research Center

The investigation of the Thermoelectronic Laser Energy Converter (TELEC) concept at the Lewis Research Center (LeRC) began with a feasibility study of a 1 megawatt sized TELEC system. The TELEC was to use either cesium vapor or hydrogen as the plasma medium. The cesium vapor TELEC appears to be the more practical device studied with an overall calculated conversion efficiency of greater than 48%. Following this study, a small TELEC cell was fabricated which demonstrated the conversion of a small amount of laser power to electrical power. The cell developed a short circuit current of 0.7 amperes and an open circuit voltage, as extrapolated from volt-ampere curves, of about 1.5 volts. Work is now in progress to construct and test a cesium vapor TELEC capable of absorbing 20% of an incident 10 kW, 10.6 micrometer beam, and converting 35% of this power to electrical power.

Alger, D. L.↗

NASA NTRS1992

Advanced materials for high-temperature thermoelectric energy conversion

A number of refractory semiconductors are under study at the Jet Propulsion Laboratory for application in thermal to electric energy conversion for space power. The main thrust of the program is to improve or develop materials of high figure of merit and, therefore, high conversion efficiencies over a broad temperature range. Materials currently under investigation are represented by silicon-germanium alloys, lanthanum telluride, and boron carbide. The thermoelectric properties of each of these materials, and prospects for their further improvements, are discussed. Continued progress in thermoelectric materials technology can be expected to yield reliable space power systems with double to triple the efficiency of current state of the art systems.

Vining, Cronin B.↗

NASA NTRS2015

Lightweight Damage Tolerant, High-Temperature Radiators for Nuclear Power and Propulsion

NASA is increasingly emphasizing exploration to bodies beyond near-Earth orbit. New propulsion systems and new spacecraft are being built for these missions. As the target bodies get further out from Earth, high energy density systems, e.g., nuclear fusion, for propulsion and power will be advantageous. The mass and size of these systems, including supporting systems such as the heat exchange system, including thermal radiators, will need to be as small as possible. Conventional heat exchange systems are a significant portion of the total thermal management mass and size. Nuclear electric propulsion (NEP) is a promising option for high-speed, in-space travel due to the high energy density of nuclear fission power sources and efficient electric thrusters. Heat from the reactor is converted to power for use in propulsion or for system power. The heat not used in the power conversion is then radiated to space as shown in figure 1. Advanced power conversion technologies will require high operating temperatures and would benefit from lightweight radiator materials. Radiator performance dictates power output for nuclear electric propulsion systems. Pitch-based carbon fiber materials have the potential to offer significant improvements in operating temperature, thermal conductivity, and mass. These properties combine to allow significant decreases in the total mass of the radiators and significant increases in the operating temperature of the fins. A Center-funded project at NASA Marshall Space Flight Center has shown that high thermal conductivity, woven carbon fiber fins with no matrix material, can be used to dissipate waste heat from NEP systems and because of high specific power (kW/kg), will require less mass and possibly less total area than standard metal and composite radiator fins for radiating the same amount of heat. This project uses an innovative approach to reduce the mass and size required for the thermal radiators to the point that in-space NEP and power is enabled. High thermal conductivity carbon fibers are lightweight, damage tolerant, and can be heated to high temperature. Areal densities in the NASA set target range of 2 to 4 kg/m2 (for enabling NEP) are achieved and with specific powers (kW/kg) a factor of about 7 greater than conventional metal fins and about 1.5 greater than carbon composite fins. Figure 2 shows one fin under test. All tests were done under vacuum conditions.

Craven, Paul D.↗

NASA NTRS2005

Performance test results of a skutterudite-based unicouple with a metallic coating

A performance test of a Skutterudite-based unicouple (MAY-04) with a metallic coating to suppress the sublimation of antimony from the legs near the hot junction is performed in vacuum (~ 9 x10-7 torr) for ~ 2,000 hours at hot and cold junction temperatures of 892.1 + 11.9 K and 316.1 + 5.5 K, respectively. The p-leg is made of CeFe3.5Co0.5Sb12 and the n-leg is made of CoSb3. Presented are the measured voltage-current characteristics, electrical power, open-circuit voltage, and Seebeck coefficients of the legs as functions of cumulative test time. Also presented is the estimate of the conversion efficiency, shortly (~ 96 hrs) after the start of test. To demonstrate the effectiveness of the metallic coating, the measurements for MAY-04 are compared with those of two uncoated unicouples of the same leg materials (MAR-03 and JUN-03), which had been tested earlier. The cross-sectional areas of the legs in MAY-04 are larger than those in MAR-03 and JUN-03, tested in argon cover gas at ~ 0.051-0.068 MPa for 450 and 1200 hours, respectively. The open circuit voltage, Voc (204 mV) of MAY-04 at Beginning-Of-Test (BOT) is almost the same as that of MAR-03, but higher than that of JUN-03 (~180 mV). Although the argon gas effectively decreased antimony loss from legs of MAR-03 and JUN-03, marked degradations in performance occurred with time in these tests. Conversely, the metallic coating in MAY-04 effectively reduced the performance degradation with cumulative test time. The estimated peak efficiency of MAY-04, shortly after BOT (10.65%) is only ~ 0.37 percentage point lower than the theoretical value, assuming zero side heat losses and zero contact resistance per leg. The peak power of MAY- 04 decreased by only ~12%, from its BOT value of ~1.6 We to ~ 1.4 We after ~ 2,000 of cumulative testing

Caillat, Thierry↗

DOE OSTI2018

Collaborative atomic-scale design, analysis, and nanofabrication for record breaking, single-crystal Zn(x)Cd(1-x)Te solar cell arrays

Cadmium telluride (CdTe) based photovoltaics provide a viable solar energy solution because of their short payback time, low manufacturing cost, and high theoretical efficiency ~29%. However, the highest record laboratory efficiency is only 22.1% and long-term performance degradation is ~1 % per year which hinders greater economic viability. Higher open circuit voltage (Voc) and fill factor (FF) are needed to increase the efficiency of the solar cell. Cells with record energy conversion efficiencies report short current (Jsc) values close to their theoretical maximum. However, Voc and FF in these devices remain well below their anticipated optimum. These electrical parameters depend on the quality of the various layers in the solar cell. In particular they depend on the crystalline quality including the defect and impurity concentrations. Therefore understanding how defects and impurities form and evolve in the material layers is important to design devices with higher efficiency and stability. The aim of this project is to create a novel path around the fundamental barriers to achieve high open-circuit voltages (VOC ≥ 1.0 V) in CdTe/CdS solar cells. The idea of the project was to combine nanopatterned crystal growth and alloy compositional grading (with concomitant lattice parameter and energy band gap grading) to reduce the defect density and dramatically improve spatial uniformity of ZnxCd(1-x)Te/CdS cells. The lattice mismatch between ZnTe and CdS is 3.9% compared to a much larger 9.2% between CdTe and CdS. Importantly, when crystal growth is contained to the nanoscale, the strain in each layer is reduced by a factor of two due to strain partitioning and 3D strain relief mechanisms that come into play. This reduces the strain in the ZnTe from 3.9% to 1.95% which is within the range of metamorphic crystal growth. In preliminary studies, molecular dynamics simulation of ZnTe/CdS islands predicted dislocation-free material when the patterning was reduced to ~80 nm in diameter. The energy band gap of ZnxCd(1-x)Te is also graded in conjunction with alloy composition. ZnTe has an energy band gap of 2.3 eV. Finally, an added benefit of patterned growth is that it enables direct one-to-one study of the relationships between fabrication, microstructure and performance of individual crystal grains within the array. Experimental characterization techniques such as atomic probe tomography (APT) and transmission electron microscopy (TEM) have elucidated much about the microstructure of the layers. However, the techniques are destructive, costly and have limitations on the information they convey. For example, TEM gives information with atomic scale resolution but on 2-dimensional substrates. On the other hand, APT gives 3-dimensional information but is not able to resolve atomic scale structure. Alternatively, Molecular Dynamics (MD) simulations offer a solution to rapidly generate time-resolved, 3-dimensional, atomic scale structures of crystal growth. Direct MD simulations of microstructures of Cu-doped II-VI compound multilayers can impact the research on CdTe/CdS solar cells. Such MD simulations require an interatomic potential database that includes at least four elements Cu, Cd, Te, and S. The Stillinger-Weber (SW) potential is the most widely used interatomic potential for semiconductors. However, while SW potentials have been developed for Ga-In-As-Se-Te, Al-Ga-In-P-As-Sb, Cd-Te-Zn-As-Si, In-Ga-N systems, no potentials existed to simulate Cd-Zn-Hg-Se-S-Te-Cu. The goal of this effort was to fill the knowledge gap by developing a Zn-Cd-Hg-S-Se-Te-Cu SW potential database to enable MD simulations of microstructures of Cu-doped CdTe/CdS solar cells. The new potential was then applied, via MD crystal growth simulations, to study the growth mechanisms and atomic structures of the ZnTe/Cu/CdTe/CdS multilayers under various conditions. The objective of the project was to inform the solar cell community on crystal growth and defect formation at the interface between CdTe-based epilayers grown on CdS substrates. MD simulations offered a unique opportunity to analyze the 3-dimensional crystal growth evolution of Cu doped ZnxCd(1-x)TeyS(1-y) alloys with atomic scale resolution under a variety of conditions. The effect of substrate orientation and polycrystallinity on crystal growth was studied. Substrates with grain boundaries were created and the growth evolution on these substrates were analyzed. Another focus was to elucidate the effect of dopant incorporation on the nature of polycrystallinity crystal growth. Dopants available through the Stillinger-Weber potential developed in this project included Cu, Zn, S, Se, Hg and native vacancies.

14 SOLAR ENERGY↗

DOE OSTI2023

Enhancing Crystallization in Hybrid Perovskite Solar Cells Using Thermally Conductive 2D Boron Nitride Nanosheet Additive

Controlling crystallization and grain growth is crucial for realizing highly efficient hybrid perovskite solar cells (PSCs). In this work, enhanced PSC photovoltaic performance and stability by accelerating perovskite crystallization and grain growth via 2D hexagonal boron nitride (hBN) nanosheet additives incorporated into the active perovskite layer are demonstrated. Specifically, in situ X-ray scattering and infrared thermal imaging during the perovskite annealing process revealed the highly thermally conductive hBN nanosheets promoted the phase conversion and grain growth in the perovskite layer by facilitating a more rapid and spatially uniform temperature rise within the perovskite film. Complementary structural, physicochemical, and electrical characterizations further showed that the hBN nanosheets formed a physical barrier at the perovskite grain boundaries and the interfaces with charge transport layers, passivating defects, and retarding ion migration. As a result, the power conversion efficiency of the PSC is improved from 17.4% to 19.8%, along with enhanced device stability, retaining ≈90% of the initial efficiency even after 500 h ambient air storage. Here, the results not only highlight 2D hBN as an effective additive for PSCs but also suggest enhanced thermal transport as one of the pathways for improved PSC performance by 2D material additives in general.

2D materials↗