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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

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

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

CdTe solar cells↗
DOE OSTI2023

Hot carrier extraction from 2D semiconductor photoelectrodes

Hot carrier-based energy conversion systems could double the efficiency of conventional solar energy technology or drive photochemical reactions that would not be possible using fully thermalized, “cool” carriers, but current strategies require expensive multijunction architectures. Using an unprecedented combination of photoelectrochemical and in situ transient absorption spectroscopy measurements, we demonstrate ultrafast (<50 fs) hot exciton and free carrier extraction under applied bias in a proof-of-concept photoelectrochemical solar cell made from earth-abundant and potentially inexpensive monolayer (ML) MoS 2 . Our approach facilitates ultrathin 7 Å charge transport distances over 1 cm 2 areas by intimately coupling ML-MoS 2 to an electron-selective solid contact and a hole-selective electrolyte contact. Our theoretical investigations of the spatial distribution of exciton states suggest greater electronic coupling between hot exciton states located on peripheral S atoms and neighboring contacts likely facilitates ultrafast charge transfer. Our work delineates future two-dimensional (2D) semiconductor design strategies for practical implementation in ultrathin photovoltaic and solar fuel applications.

2D materials↗
DOE OSTI2021

Lamination of transparent conductive adhesives for tandem solar cell applications

A transparent conductive adhesive (TCA) interlayer for mechanically stacked multijunction solar cells provides adhesive strength and electrical connection between sub-cells when stacked. The fabrication of TCA sheets from an ethyl-vinyl acetate (EVA) matrix and silver coated compliant conductive microspheres, similar to industry-standard EVA encapsulant sheets, compatible with a standard lamination process was developed. Blade coating TCA sheets using 3D printed blades and testing of vertical conduction through the interlayer with a TCA conductivity jig allowed for reproducible measurements and low-cost fabrication. The supplemental information provides design files to enable other researchers to produce their own blades and testing jigs. We identified 0.5 mm as an optimal blade height for producing lab-scale TCA sheets and 120 °C at 3 psi for 10 min as the optimal vacuum lamination process to minimize resistance and possible damage to samples. For TCA sheets with coverages between 0.75% and 9%, the series resistance was approximately 0.2 O cm2 which should result in minimal losses for one-sun photovoltaic applications.

14 SOLAR ENERGY↗
DOE OSTI2026

Performance Modeling of Tandem Photovoltaics: A Yearlong Outdoor Degradation Analysis of a Ga⁢As//Si Minimodule

We present a performance modeling and degradation analysis framework for tandem photovoltaic modules, building upon established procedures for crystalline silicon devices and adapting them to account for the spectral sensitivity of multijunction technologies. The methodology employs filter criteria to select outdoor measurements close to standard test conditions (STC) under stable spectral and ambient conditions, followed by normalization of power production data with corrections for temperature, irradiance, and precipitable water vapor. We demonstrate this framework using a mechanically stacked four-terminal gallium arsenide (Ga⁢As) // silicon (Si) tandem solar minimodule deployed outdoors from October 2019 to January 2021 in Golden, Colorado, USA. We determined degradation rates of −4.1 ±0.2%/year for the Ga⁢As subcell and −2.5 ±0.9%/year for the Si subcell, with analysis of individual performance metrics indicating that packaging degradation, particularly delamination, was the dominant failure mode. Simulations using PVcircuit, an open-source equivalent-circuit solver, confirmed these findings. The presented methodology provides a reproducible foundation for performance modeling and degradation analysis of emerging tandem technologies.

14 SOLAR ENERGY↗
DOE OSTI2025

Topological Rigidity and Non-Abelian Defect Junctions in Chiral Nematic Systems with Effective Biaxial Symmetry

We study topologically stable defect structures in systems where the defect line classification in three dimensions and associated algebra of interactions (the fundamental group) are governed by the non-Abelian eight-element group, the quaternions 𝑄 8 . The non-Abelian character of the defect algebra leads to a topological rigidity of bound defect pairs, and trivalent junctions which are the building blocks of multijunction trivalent networks. We realize such structures in laboratory chiral nematics and analyze their behavior analytically, along with numerical modeling.

Liquid crystals↗
DOE OSTI2023

Disruptive Photovoltaic Technologies Can Accelerate Global Decarbonization

This contribution explores PV manufacturing capacity expansion trajectories needed to achieve the goal of global decarbonization assuming that investors make financially rational decisions avoiding stranded production assets while still effectively exploiting experience curve benefits in both manufacturing process and product design. Substantial production cost savings and timely decarbonization risk mitigation could accrue by adoption and scaling of high efficiency multijunction device architectures and thin film direct bandgap semiconductor technologies that provide lower manufacturing capital intensity. We demonstrate that there is a $1-2 trillion market opportunity for such disruptive technologies while also providing hundreds of billions of dollars of cost savings to reach total decarbonization.

decarbonization↗
DOE OSTI2019

Reverse Heterojunction (Al)GaInP Solar Cells for Improved Efficiency at Concentration

Mitigating series resistance is crucial to the efficiency of concentrator solar cells at high current density. Conventional AlGaInP junction designs for the top junction of III-V multijunction cells present a challenging tradeoff between series resistance on the one hand and current collection and voltage on the other hand. In this article we discuss the physics of a reverse heterojunction solar cell that aims to improve on this tradeoff by combining a high bandgap Al 0.18 Ga 0.33 In 0.49 P base and a lower bandgap (Al)GaInP emitter. The high mobility of the emitter leads to a relatively low series resistance, compared with a high bandgap homojunction cell. Furthermore, the electroluminescence spectrum shows emission peaks from both the emitter and base, leading to an open-circuit voltage that is not strictly dominated by either layer. The reverse heterojunction design is increasingly beneficial as the one-sun voltage increases.

14 SOLAR ENERGY↗
DOE OSTI2021

Proton Radiation Tolerance of Wide and Narrow Band Gap Perovskite Solar Cells

Two different single junction mixed organic-inorganic halide perovskite solar cells (PSCs) were assessed for their tolerance to high energy proton radiation. Both the narrow band gap mixed tin-lead iodide and wide band gap lead iodide-bromide show remarkable tolerance for fluences up to 1x10 11 p/cm 2 . Both materials show a retention of open circuit voltage and decrease in dark current densities indicating minimal effect on SRH recombination that typically plagues traditional III-V based solar cells. Additionally, a control device that was processed without the perovskite absorber layer showed better diode characteristics and lower dark current densities after proton irradiation. The tolerance of these perovskite as a class of materials is promising for multijunction tandem flexible photovoltaic devices.

perovskite↗
DOE OSTI2021

Compensated Contacts for Three-Terminal Transistor Solar Cells

The heterojunction bipolar transistor solar cell (HBTSC) is an alternative to conventional double-junction solar cells that combines the advantages of three-terminal architectures with a compact design. A critical part of the HBTSC fabrication is the implementation of the middle contact, the one associated to the base layer in the transistor structure, because this layer can be damaged by the diffusion of metallic species during contact annealing. As a solution we propose to implement a "compensated contact", that is, to leave a thin (< 200 nm) portion of emitter or collector between the base layer and the contact metals and compensate its doping during contact annealing. Using an Au/Zn/Au metal structure to compensate a 150 nm thick portion of the collector, we obtain a specific contact resistance ~8 10-4 ..omega.. cm2. This value is fairly invariant for annealing temperatures between 400 and 460 degrees C and annealing times between 2 and 5 minutes, and it does not improve by adding Pd to the metallic stack. Optimizing the compensated contact technology opens the path to the realization of III-V-material-based HBTSCs with open-circuit voltages and fill factors comparable to those of conventional multijunction architectures.

contact resistance↗
DOE OSTI2022

Evaluation of an LED Simulator for Single- and Multi-Junction PV Cell Performance Testing

We present the evaluation of a solar simulator comprising a Light Emitting Diode (LED) array as its light source. While multiple applications can be envisioned for such a light source, here we focus on its use for performance testing of solar cells at Standard Test Conditions. With this in mind, we present characterization of the spatial uniformity of the irradiance and its temporal stability as well as the spectral range and spectral class. For a multisource simulator, the spectral uniformity across the test plane should also be evaluated and we discuss a method for performing this evaluation that is well suited to a solar cell performance testing application. One major advantage of this simulator is the ability to easily adjust the spectral output as needed in multijunction PV cell measurements and we also discuss this application here.

LED↗
DOE OSTI2025

Eye-Safe 1.5 and 2.0 Micron Laser Power Conversion Using Metamorphic InGaAs Photovoltaic Devices

Laser power transmission at 1.5 and 2.0 microns are considered eye-safe up to 0.1 W/cm2 irradiance. Further, the atmospheric bands at these two wavelengths may provide the highest optical transmission through the atmosphere in hazy conditions. By slowly changing the lattice-constant of InGaAs with a Compositionally Graded Buffer (CGB), we have fabricated InGaAs photovoltaic (PV) devices over a wide range of bandgaps useful for multijunction concentrating photovoltaic devices, thermophotovoltaic devices, and Laser Power Converters (LPC). Here, we have demonstrated monochromatic power conversion of 1.5-micron light with an eye-safe efficiency of 39.8% at 0.1 W/cm2 with InGaAs devices lattice-matched to InP with an Antireflection Coating (ARC). We have also demonstrated 30.2% and 24.5% eye-safe LPC efficiency of metamorphic InGaAs devices grown on GaAs substrates using GaInP and AlGaAsP CGBs, respectively. Finally, we have demonstrated metamorphic InGaAs devices grown on InP and GaAs substrates that are estimated to have eye-safe LPC efficiencies at 2.0 microns of 27.4% and 20.9% respectively. The efficiencies of all these LPC devices continues to increase up to about 30-70 times the eye-safe irradiance.

eye-safe↗
DOE OSTI2020

GaAsP/Si Tandem Solar Cells: Pathway to Low-Cost, High-Efficiency Photovoltaics

Si is the dominant PV technology, now and for the foreseeable future, due to its extensive manufacturing infrastructure, supply chain, feedstock availability, and highly optimized degree of fabrication processes, which altogether has produced an economic scenario where PV electricity generation is often cheaper than conventional fossil based generation. In many places, the overarching goal of grid parity has been achieved, but further improvement in performance-cost metrics are still needed to sustain the continued LCOE reductions needed to not only compete with conventional generation, but displace it on a global scale; a matter of critical importance if we stand any hope of slowing climate change. Nevertheless, single-junction Si PV is already nearing its physical limit, both in performance and cost, and is thus cannot meet these long-term goals alone. To this end, we are working on the development of monolithic III-V/Si tandem solar cells, which improve upon the performance of pure Si by providing enhanced utilization (reduced thermalization) of high-energy photons. This architecture nominally combines the substantial existing knowledge base, manufacturing infrastructure, and low cost of Si PV with the high efficiencies afforded by the well-established multijunction approach — the only proven way to break the single-junction limit. Although the metal-halide perovskite/Si tandem architecture has garnered substantial attention in recent years, serious questions regarding reliability and service lifetime remain, whereas III-V PV has a proven track record, including in the harsh concentrator and space environments. Additionally, there are multiple fabrication approaches to producing III-V/Si tandem cells, but we are focused on monolithic epitaxial integration as it is the most likely to yield the lowest ultimate LCOE in a fully mature, scaled technology. In this work we have produced multiple generations of GaAsP/Si tandem solar cells, demonstrating a more than 10% absolute AM1.5G efficiency improvement within the time frame of the project, including two verified world records. We have done this using industry-standard fabrication methods, showing that this platform can ultimately be manufactured at scale using existing or only slightly upgraded Si and III-V tooling. Our scientific and engineering advances across a range of fundamental and applied areas – III-V/Si heteroepitaxial integration, defect control in metamorphic III-V epitaxy, fundamental materials-oriented solar cell design and modeling methodology, and more – have created clear pathways for continued advances toward the goal of >30% AM1.5G cell efficiency (and >25% module) and will serve to inform the broader research community for well beyond this immediate application. Techno-economic modeling indicates that our approach can indeed meet SunShot/SETO LCOE targets, but as with any “post-Si” technology there are difficult, but not insurmountable barriers, requiring continued focused research and development efforts.

14 SOLAR ENERGY↗
DOE OSTI2024

Controlling Interfacial Charge Separation Energetics and Kinetics

The overall goal is to probe electron transfer kinetics of the Marcus inverted region at interfaces. This project specifically uses a dye‐semiconductor interface with a reversible electron transfer reagent in solution where the semiconductor conduction band and electron transfer reagent ideally have a potential energy difference firmly within the Marcus inverted region. The goals of this project are: (Goal 1) Identify dye design elements that give dyes with low energy ground‐state oxidation potentials while retaining desirable electron transfer kinetics at the semiconductor interface. (Goal 2) Identify dye designs with excited‐state oxidation potentials set to fixed energies through molecular design while the dye ground‐state oxidation potentials are varied to allow for the evaluation of varied electron transfer reagents/redox shuttles (RS) with different free energies for electron transfer. (Goal 3) Within the context of the functionality identified in goals 1 and 2, goal 3 seeks to design dyes with features maximizing charge carrier lifetimes by minimizing recombination losses at metal oxide interfaces with high voltage systems. (Goal 4) Probe electron transfer kinetics in a high voltage‐dye sensitized solar cell with both the oxidized dye and RS firmly within the Marcus inverted region with regard to the TiO2 CB. (Goal 5) Identify tailored sensitizer/redox shuttle pairs with desirable electron transfer kinetics in defined spectral regions capable of “banding off” incident solar irradiation to give high voltage multijunction systems capable of exceeding the Shockley‐Queisser limit and powering catalytic processes.

14 SOLAR ENERGY↗
DOE OSTI2024

A Perspective on Solar-Driven Electrochemical Routes for Sustainable Methanol Production

The transition towards sustainable and renewable energy sources is imperative in mitigating the environmental impacts of escalating global energy consumption. Methanol, with its versatile applications and potential as a clean energy carrier, a precursor chemical, and a valuable commodity, emerges as a promising solution within the realm of renewable energy technologies. This work explores the integration of electrochemistry with solar power to drive efficient methanol production processes, focusing on electrochemical reduction (ECR) of CO 2 and methane oxidation reaction (MOR) as pathways for methanol synthesis. Through detailed analysis and calculations, we evaluate the thermodynamic limits and realistic solar-to-fuel (STF) efficiencies of ECR and MOR. Our investigation encompasses the characterization of multijunction light absorbers, determination of thermoneutral potentials, and assessment of STF efficiencies under varying conditions. We identify the challenges and opportunities inherent in both ECR and MOR pathways, shedding light on catalyst stability, reaction kinetics, and system optimization, thereby providing insights into the prospects and challenges of solar-driven methanol synthesis, offering a pathway towards a cleaner and more sustainable energy future.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2026

Data Associated with "Identifying Suitable Front Contacts for High-Efficiency Cd(Se,Te) Solar Cells on Space-Qualified Cover Glass"

This is data associated with the publication " Identifying Suitable Front Contacts for High-Efficiency Cd(Se,Te) Solar Cells on Space-Qualified Cover Glass " by Aesha P. Patel, Ryan Muzzio, Matthew R. Young, Robert Morrissey, Suresh Chaulagain, B. Edward Sartor, Prabodika N. Kaluarachchi, Christian Velez, Joshua A. Brown, Joel N. Duenow, Stephen Glynn, Michael J. Heben, Zhaoning Song, Nikolas J. Podraza, Adam B. Phillips, Randy J. Ellingson, Matthew O. Reese. All data associated with each figure in the manuscript and supplementary should be available in this dataset. A readme file is also included to provide some guidance. Abstract: Deployment of photovoltaics in space requires devices that combine high-efficiency, low areal mass, and resilience to harsh environments. Historically, high-efficiency multijunction III–V materials have dominated space power systems; however, their high cost and limited manufacturing throughput motivate the exploration of scalable alternatives. While CdTe-based thin-film photovoltaics offer an attractive option, their performance on non-conventional substrates can suffer from front-contact instability under higher-temperature processing. Here, the role of front-contact chemistry in limiting cell performance is investigated using CdTe-based devices fabricated on 150 μm thick Ceria-doped space-qualified 0214 Corning glass. A matrix of four transparent conducting oxides (TCOs: CTO, AZO, ITO, IZO) combined with two n-type emitters (MZO, IGO) reveals chemical stability at the front interface—rather than absorber composition alone—governs recombination losses, voltage deficits, and device reproducibility. Chemically stable front-contact combinations suppress elemental diffusion and interfacial degradation, resulting in significantly improved carrier lifetimes and junction quality. These insights are validated through record-certified Cd(Se,Te) cell efficiencies of 18.4% under AM1.5G and 16.2% under AM0 illumination on ultra-thin glass. Beyond CdTe, this work provides a general framework for the rational selection of TCO/emitter interfaces in superstrate thin-film photovoltaics, including emerging technologies like metal halide perovskites, while enabling high-efficiency, lightweight photovoltaics for space applications.

14 SOLAR ENERGY↗
DOE OSTI2022

Triple-Junction III-V Solar Cells with 39.5% AM1.5G and 34.2% AM0 Efficiencies

III-V multijunction solar cells have the highest efficiencies of any PV technology. These devices are currently the dominant space PV technology, and are being investigated for a wide range of other applications where efficiency is a key metric. In this presentation, we describe a 3-junction cell with the highest 1-sun efficiency to date: 39.5% under the global spectrum, which is higher than previous 6-junction devices. When tuned for the space spectrum, the cell achieves 34.2% beginning-of-life efficiency, without consideration for radiation hardness. These efficiency improvements are enabled by combining advances in device architectures and extended-defect control strategies. This latest 3-junction device includes a high-performance front-junction GaInP top cell, an optically-thick strain-balanced quantum well middle cell, and a lattice-mismatched GaInAs bottom cell with record performance despite dislocations. These advances not only allow high efficiency photovoltaics for both space and terrestrial PV applications, but also help enable new applications of III-V materials.

GaInAs↗
DOE OSTI2022

Coalescence of GaP on V-Groove Si

With an increase of control over crystalline defects, metallorganic vapor phase epitaxy (MOVPE)-grown III-V-on-Si multijunction solar cells have seen rapid increases in efficiency in recent years, pointing to a promising path to lower cost III-V solar cells. However, the cost of chemo-mechanical polishing the Si wafers to prepare them for epitaxy is high. The use of V-groove nanopatterns enables similar defect reduction to that achieved on planar wafers, but the nanopatterns can be fabricated with a low-cost process. While V-grooves offer advantages over planar Si, they add complexity to the growth process. In particular, coalescence can cause the formation of threading dislocations, and the highly-directional growth conditions required for coalescence are unusual for MOVPE. We have studied the coalescence of GaP films nucleated directly on V-groove Si by MOVPE. We observed that for optimized growth conditions (V/III=5,000 and T=800 C) two growth modes were possible, and the resulting morphology depended on the exact geometry of the SiNx cap used to cover the (0 0 1)-oriented Si at the tops of the grooves. For caps with a width >100 nm, noncoalescing, nano ridge-like growth terminating in f1 1 1g facets was observed. For narrower caps, coalescence with an RMS roughness of 0.2 nm as measured by atomic force microscopy was observed. We will discuss mechanisms responsible for this phenomenon, including the role of Si from the substrate surface. The dislocation dynamics of this system were studied with electron channeling contrast imaging (ECCI) and transmission electron microscopy (TEM). We find that V-grooves do not block dislocation glide; ECCI measurements show misfit dislocations greater than 10 micrometers long observed to continue perpendicularly across neighboring V-grooves. In addition, all threading dislocations appear to lie on f1 1 1g planes, consistent with the GaP relaxing via glided-in glissile dislocations. The dislocation dynamics and morphological evolution of the coalescence of GaP on Si, possible mechanisms behind the observed phenomenons, and further dislocation mitigation strategies for these materials will be presented.

dislocation dynamics↗
DOE OSTI2022

Dyes, dye-sensitized solar cells, and methods of making and using the same

Provided herein are dyes, dye-sensitized solar cells, and sequential series multijunction dye-sensitized solar cell devices. The dyes include an electron deficient acceptor moiety, a medium electron density π-bridge moiety, and an electron rich donor moiety comprising a biaryl, a substituted biaryl, or an R 1 , R 2 , R 3 substituted phenyl where each of R 1 , R 2 , and R 3 independently comprises H, aryl, multiaryl, alkyl substituted aryl, alkoxy substituted aryl, alkyl substituted multiaryl, alkoxy substituted multiaryl, OR 4 , N(R 5 ) 2 , or a combination thereof; each R 4 independently comprises H, alkyl, aryl, alkyl substituted aryl, alkoxy substituted aryl, or a combination thereof; and each R 5 independently comprises aryl, multiaryl, alkyl substituted aryl, alkoxy substituted aryl, alkyl substituted multiaryl, alkoxy substituted multiaryl, or a combination thereof. The solar cells include a glass substrate, a dye-sensitized active layer, and a redox shuttle. The devices include at least two dye-sensitized solar cells connected in series.

Delcamp, Jared Heath↗