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Results for “open-circuit measurement”

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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Electrochemical behavior of SnCl 2 and influence of Cu and Ni ions in molten LiCl−KCl−CaCl 2 eutectic

Reliable transport and thermodynamic data for multivalent ions in complex molten salts are scarce, limiting model fidelity for electrorefining and impurity control. Here, we report a comprehensive electrochemical characterization of SnCl₂ in LiCl–KCl–CaCl₂ (50.5–44.2–5.3 mol%) at 685 K, including the effects of Ni 2+ and Cu + impurities. Using cyclic voltammetry (CV), chronoamperometry (CA), and chronopotentiometry (CP), we quantified Sn 2+ and Ni 2+ diffusion with exceptional agreement across methods: Sn 2+ averaged (1.03 ± 0.10) × 10 −5 cm 2 s −1 , and Ni 2+ averaged (0.75 ± 0.19) × 10 −5 cm 2 s −1 . The tight confidence-interval overlap across CV, CA, and CP strengthens confidence in these values and is uncommon in molten chloride studies. Open-circuit-potential measurements provided standard apparent reduction potentials that closely match LiCl–KCl literature, indicating minimal shift with CaCl₂ present. The Sn 2+ /Sn couple behaves as a reversible two-electron soluble–insoluble process at 685 K; the Sn 4+ /Sn 2+ couple transitions to soluble–soluble behavior near 788 K, which may correlate with the decomposition of surface bound chlorostannates, though direct characterization remains to be established. In mixed systems, Cu+/Cu overlaps Sn 2+ /Sn, limiting Cusingle bondSn electroseparation, whereas the larger potential gap between Ni 2+ /Ni and Sn 2+ /Sn supports selective Ni removal. These internally consistent transport and thermodynamic data establish a validated basis for process modeling and optimization of Sn electrorefining and impurity management in LiCl–KCl–CaCl₂.

Berzins-Delahay↗
DOE OSTI2026

Electrolyte Organization Leads to Potential-Dependence in Thermochemical Catalysis of Nonpolar Reactions

Electrochemical polarization is now known to play a key role in thermochemical catalysis at solid–liquid interfaces. However, existing frameworks cannot account for why even nonpolar, nonfaradaic reactions are sensitive to interfacial polarization. In order to uncover the molecular basis of this phenomenon, we herein study the potential-dependent reaction kinetics of ethylene and trans-2-butene hydrogenation at Pt–liquid interfaces. Measurements were performed in aqueous and ortho-difluorobenzene (o-DFB) solutions, spontaneously polarizing the Pt–liquid interfaces by, respectively, varying the pH or dissolving distinct metallocene redox buffers into solution. Here, we find that at comparable mechanistic regimes, the rates of both ethylene and trans-2-butene hydrogenation are maximized near the same electrochemical potential, E. Moreover, the potential-dependence, defined as $\frac{∂ln 𝑟}{∂𝐸}$, of trans-2-butene hydrogenation is approximately 2.2× greater than that of ethylene hydrogenation across the full potential range studied. These observations are all consistent with a model in which polarization of the Pt surface away from the local potential of zero free charge (E PZFC ) induces electrostatic organization of the polar solvent and charged ions near the interface, which impedes olefin adsorption and surface reaction because these surface reactions induce electrolyte displacement. Accordingly, interfacial polarization alters the free energy landscape and thus the rate of nonpolar heterogeneous catalysis by controlling the degree of electrostatic organization of polar and charged spectators at the interface, which do not in general need to be specifically chemisorbed onto the surface but could simply be close enough to the surface to be perturbed by the olefin adsorption. These results point toward electrochemical design handles, namely, the electrolyte, catalyst potential, and local E PZFC of the catalyst, with which to tune interfacial catalysis of thermochemical organic transformations.

adsorption↗
DOE OSTI2025

Imaging Power Losses in CdSeTe Solar Cells

Much of the research on CdSeTe photovoltaics is focused on improving the open-circuit voltage (V oc ) of the solar cell. But solar cells operate at the maximum power point (MPP) rather than at V oc . The recombination processes at MPP may be different than those at V oc , and increasing the power output at MPP is the key to advancing efficiency. Here, we introduce a camera-based PL imaging system that enables power loss analysis under operating conditions and across cm-sized areas covering multiple cells. The instrument is demonstrated with CdSeTe devices having efficiencies greater than 19%. An implied current density versus implied voltage (iJV) curve can be produced at each pixel with <20 µm resolution. We find that regions with high implied open circuit voltage are often those with low implied fill factor, showing that voltage loss analysis at open circuit is not sufficient to understand power losses under operating conditions. Measurement of JV curves as a function of irradiance can also be performed in the system, which allows series resistance-free pseudo JV (pJV) curves to be produced. Comparison of pJV to measured JV and iJV curves allows further analysis of the operational losses, pointing the way to higher efficiency.

14 SOLAR ENERGY↗
DOE OSTI2025

Scintillator based nuclear photovoltaic batteries for power generation at microwatts level

A nuclear photovoltaic battery uses scintillator to convert radiation into visible light, which is then collected by a photovoltaic (PV) cell to generate electricity. If the radiation is gamma-rays emitted from external sources, the battery may also be referred as gammavoltaic battery. In this study, a polycrystalline CdTe solar cell was optically coupled with a 2.0 cm × 2.0 cm × 1.0 cm Gadolinium Aluminum Gallium Garnet (GAGG) scintillator, and the resulting device was tested using intense gamma radiation fields from a Cs-137 (1.5 kRad/h) and a Co-60 (10 kRad/h) irradiator. Measurements with Cs-137 provided a maximum power output (P max ) of ~288 nW, with a short-circuit current density (J sc ) of ~1.22 μA/cm 2 and an open-circuit voltage (V oc ) of ~0.34 V. In contrast, Co-60 irradiator gave a P max of 1.5 μW, with a J sc of ~4.73 μA/cm 2 and a V oc of ~0.38 V. The CdTe was also paired with a Lutetium-Yttrium Oxyorthosilicate (LYSO) crystal and tested with the Cs-137 source. The experiment presents a scalable option to reach to higher power outputs by harvesting gamma radiation fields in many cases where high radiation field demands heavy shielding and is often regarded as unwanted waste.

25 ENERGY STORAGE↗
DOE OSTI2024

Effect of ZnO and PEDOT:PSS charge selective layers on photovoltage of cuprous oxide (Cu 2 O) heterojunction solar cells

Electrochemical deposition (ECD) of Cu 2 O provides a scalable and low temperature pathway to solar cells with a theoretical high energy conversion efficiency of 23%, based on the 2.0–2.2 eV band gap of Cu 2 O. However, existing ECD-Cu 2 O devices are plagued by poor crystallinity and low selectivity of the electron and hole transport layers. Here we use Vibrating Kelvin Probe Surface Photovoltage Spectroscopy (VKP-SPV) to probe the charge transfer selectivity in FTO/ZnO/Cu 2 O/PEDOT:PSS/Ni heterojunction solar cells. Selective electron extraction is achieved at the ZnO back contact to Cu 2 O, as confirmed by a negative surface photovoltage signal. While the uncoated Cu 2 O surface is electron-selective due to the formation of a hole depletion layer, spin coating of a PEDOT:PSS film turns it into a hole-selective interface. After adding nickel metal ink top electrodes, functional 1.0 cm 2 solar cells with power conversion efficiency (PCE) of up to 0.07%, 195 mV open-circuit voltage, and 1.28 mA cm –2 short-circuit photocurrent are achieved. The photovoltaic performance is higher for aluminum doped zinc oxide (AZO) substrates than for fluorine doped tin oxide (FTO) due to the presence of a n-/p-junction that further increases the electron selectivity of the AZO/ZnO/Cu 2 O contacts. Overall, this work demonstrates the first application of PEDOT:PSS as a hole transport layer (HTL) for Cu 2 O and the use of VKP-SPV to measure the photovoltage contributions of the Cu 2 O interfaces. Furthermore, the ability to fabricate Cu 2 O solar cells at near room temperature without the use of vacuum methods or rare elements is an important step towards a scalable Cu 2 O PV technology.

14 SOLAR ENERGY↗
DOE OSTI2022

Monocrystalline 1.7-eV MgCdTe solar cells

Monocrystalline 1.7-eV Mg 0.13 Cd 0.87 Te/Mg x Cd 1-x Te (x > 0.13) double-heterostructure (DH) solar cells with varying Mg composition in the barrier layers are grown by molecular beam epitaxy. Furthermore, a Mg 0.13 Cd 0.87 Te/Mg 0.37 Cd 0.63 Te DH solar cell featuring abrupt interfaces between barriers and absorber and the addition of a SiO 2 anti-reflective coating demonstrates open-circuit voltage (V OC ), short-circuit current density (J SC ), fill factor (FF), and device active-area efficiencies up to 1.129 V, 17.3 mA/cm 2 , 77.7% and 15.2%, respectively. The V OC and FF vary oppositely with the Mg x Cd 1-x Te barrier height indicating an optimal design of the MgCdTe DHs as a tradeoff between carrier confinement and carrier transport. Temperature-dependent V OC measurements reveal the majority of carrier recombination in the devices occurs outside the DHs, in the a-Si:H hole-contact layer and at the interface between the a-Si:H layer and the Mg x Cd 1-x Te top barrier at room temperature. Simulation results for the device with the highest efficiency show that the p-type a-Si:H layer and Mg 0.37 Cd 0.63 Te top barrier contribute 1.3 mA/cm 2 and 2.4 mA/cm 2 J SC loss, respectively.

14 SOLAR ENERGY↗
DOE OSTI2023

Light-trapping structures fabricated in situ for ultrathin III-V solar cells

Here, we describe a fully in situ method of fabricating light-scattering structures on III-V materials that generates a rough morphology via vapor phase etching and redeposition. Fully in situ methods support higher industrial throughput by utilizing the growth reactor to generate the light-trapping structures after device growth without removal from the reactor. We use HCl and PH 3 to etch and redeposit scattering morphologies on Ga 0.5 In 0.5 P in a dynamic hydride vapor phase epitaxy (D-HVPE) reactor. We show that the addition of PH 3 leads to redeposition during the vapor phase HCl etching of Ga 0.5 In 0.5 P and that HCl flow rate and time exposed to HCl-PH 3 each independently cause a linear increase in the redeposited feature size, indicating that redeposition proceeds by island growth in a III-Cl-limited, hydride-enhanced HVPE regime. Auger electron spectroscopy and scanning transmission electron microscopy with energy dispersive spectroscopy (STEM-EDS) reveal redeposition to be highly Ga-rich GaInP, i.e., Ga(In)P. The Ga-rich nature of the redeposition results from the higher thermodynamic driving force for Ga incorporation than for In during HVPE growth and the difference in the volatility of the III-Cl etch products. The resulting morphologies have high broadband scattering, as determined by normal specular reflectance and integrating sphere measurements, indicating effectiveness as light-scattering structures. In a 270-nm-thick GaAs photovoltaic device with a textured back surface, we achieve a 4.9% increase in short circuit current density (J SC ) without any loss in open-circuit voltage (V OC ) relative to a planar control using only a 60 s in situ texturing treatment.

14 SOLAR ENERGY↗
NASA NTRS1973

Parametric performance characteristics and treatment of temperature coefficients of silicon solar cells for space application

The electrical performance characteristics of 2 and 10 ohms-cm N/P-type silicon solar cells were measured at simulated solar intensities of 5, 50, 100, 140, 250, 400, 550, 700, and 850 mW/sq cm. At each intensity, the temperature was varied in increments of 20 deg between extremes of +160 and -160 C. Short-circuit current, open-circuit voltage, and maximum power are presented in graphical format. Also described are three methods for predicting solar cell electrical performance as a function of temperature and intensity. Two of the methods are suitable for use at extreme temperature-intensity conditions. These methods were used sucessfully to predict the performance of the transducer on board the Mariner Mars 1971 spacecraft.

Patterson, R. E.↗
NASA NTRS1978

Mechanisms of photon-induced changes in silicon solar cell parameters

Reversible changes in solar cell performance were induced by AM1 illumination and evaluated by measuring short-circuit current, weak light spectral response, and minority carrier diffusion length. In n(+)p cells the change manifests itself as a reduced short-circuit current, a loss of the red response, and a reduction in minority carrier diffusion length. In p(+)n cells there are two-photon induced effects: (1) enhancement of the blue spectral response, presumably occurring in the p(+) layer and (2) degradation in open-circuit voltage at low light levels due to increased leakage occurring only after the junction edge is exposed to bright light. Most of these photon effects are attributed to defects in the silicon.

Cheng, L. J.↗
NASA NTRS1981

Nickel-doped silicon for solar cells

Large grain boundaries in polycrystals act as gettering centers for nickel precipitates, improving cell performance. Effects are described in report. Data on open-circuit voltage, short-circuit current, maximum power, and conversion efficiency for illuminated cells are compared with values for undoped cells. Dark forward current versus voltage is also measured for cell types.

Salama, A. M.↗
NASA NTRS1982

Photovoltaic properties of ferroelectric BaTiO3 thin films RF sputter deposited on silicon

Ferroelectric thin films of BaTiO3 have been successfully deposited on n-type silicon substrates at temperatures above 500 C by RF sputtering in an O2/Ar atmosphere. Analysis by X-ray diffraction patterns show that films deposited at room temperature are amorphous. At temperatures above 500 C, crystalline BaTiO3 films with a tetragonal structure are obtained. The polarization-electric field (P-E) hysteresis loops and a broad peak in the dielectric constant versus temperature curve at Curie point indicate that the RF sputtered BaTiO3 films are ferroelectric. An anomalous photovoltaic effect is observed in these thin films which is related to the remanent polarization of the material. The results on open-circuit and short-circuit measurements provide an important basis for a better understanding of the role of photovoltaic field, photovoltaic current, and the pyroelectric properties in photoferroelectric domain switching.

Dharmadhikari, V. S.↗
NASA NTRS1984

Surface and allied studies in silicon solar cells

Measuring small-signal admittance versus frequency and forward bias voltage together with a new transient measurement apparently provides the most reliable and flexible method available for determining back surface recombination velocity and low-injection lifetime of the quasineutral base region of silicon solar cells. The new transient measurement reported here is called short-circuit-current decay (SCCD). In this method, forward voltage equal to about the open-circuit or the maximum power voltage establishes excess holes and electrons in the junction transition region and in the quasineutral regions. The sudden application of a short circuit causes an exiting of the excess holes and electrons in the transition region within about ten picoseconds. From observing the slope and intercept of the subsequent current decay, the base lifetime and surface recombination velocity can be determined. The admittance measurement previously mentioned then enters to increase accuracy particularly for devices for which the diffusion length exceeds the base thickness.

Lindholm, F. A.↗
NASA NTRS1986

Effect of low-energy hydrogen ion implantation on dendritic web silicon solar cells

The effect of a low-energy (0.4 keV), short-time (2-min), heavy-dose (10 to the 18th/sq cm) hydrogen ion implant on dendritic web silicon solar cells and material was investigated. Such an implant was observed to improve the cell open-circuit voltage and short-circuit current appreciably for a number of cells. In spite of the low implant energy, measurements of internal quantum efficiency indicate that it is the base of the cell, rather than the emitter, which benefits from the hydrogen implant. This is supported by the observation that the measured minority-carrier diffusion length in the base did not change when the emitter was removed. In some cases, a threefold increase of the base diffusion length was observed after implantation. The effects of the hydrogen implantation were not changed by a thermal stress test at 250 C for 111 h in nitrogen. It is speculated that hydrogen enters the bulk by traveling along dislocations, as proposed recently for edge-defined film-fed growth silicon ribbon.

Rohatgi, A.↗
NASA NTRS1990

1.00 MeV proton radiation resistance studies of single-junction and single gap dual-junction amorphous-silicon alloy solar cells

A comparative study of the radiation resistance of a-Si:H and a-SiGe:H single-junction and a-Si:H dual-junction solar cells was conducted. The cells were irradiated with 1.00-MeV protons with fluences of 1.0 x 10 to the 14th, 5.0 x 10 to the 14th and 1.0 x 10 to the 15th/sq cm and characterized using I-V and quantum efficiency measurements. The radiation resistance of single-junction cells cannot be used to explain the behavior of dual-junction cells at a fluence of 1.0 x 10 to the 15th/sq cm. The a-Si H single-junction cells degraded the least of the three cells; a-SiGe:H single-junction cells showed the largest reduction in short-circuit current, while a-Si:H dual-junction cells exhibited the largest degradation in the open-circuit voltage. The quantum efficiency of the cells degraded more in the red part of the spectrum; the bottom junction degrades first in dual-junction cells.

Abdulaziz, Salman↗
NASA NTRS2007

Recovery of Electron/Proton Radiation-Induced Defects in n+p AlInGaP Solar Cell by Minority-Carrier Injection Annealing

A high efficient In0.48Ga0.52P/In0.01Ga0.99As/Ge triple junction solar cell has been developed for application in space and terrestrial concentrator PV system [1-3]. Recently, a high conversion efficiency of 31.5% (AM1.5G) has been obtained in InGaP/(In)GaAs/Ge triple junction solar cell, and as a new top cell material of triple junction cells, (Al)InGaP [1] has been proposed to improve the open-circuit voltage (Voc) because it shows a higher Voc of 1.5V while maintaining the same short-circuit current (ISC) as a conventional InGaP top cell under AM1.5G conditions as seen in figure 1 (a). Moreover, the spectral response of 1.96eV AlInGaP cell with a thickness of 2.5..m shows a higher response in the long wavelength region, compared with that of 1.87eV InGaP cell with 0.6..m thickness, as shown in figure 1 (b). Its development will realize next generation multijunction (MJ) solar cells such as a lattice mismatched AlInGaP/InGaAs/Ge 3-junction and lattice matched AlInGaP/GaAs/InGaAsN/Ge 4-junction solar cells. Figure 2 shows the super high-efficiency MJ solar cell structures and wide band spectral response by MJ solar cells under AM1.5G conditions. For realizing high efficient MJ space solar cells, the higher radiation-resistance under the electron or proton irradiation is required. The irradiation studies for a conventional top cell InGaP have been widely done [4-6], but little irradiation work has been performed on AlInGaP solar cells. Recently, we made the first reports of 1 MeV electron or 30 keV proton irradiation effects on AlInGaP solar cells, and evaluated the defects generated by the irradiation [7,8]. The present study describes the recovery of 1 MeV electron / 30 keV proton irradiation-induced defects in n+p- AlInGaP solar cells by minority-carrier injection enhanced annealing or isochronal annealing. The origins of irradiation-induced defects observed by deep level transient spectroscopy (DLTS) measurements are discussed.

Lee, H. S.↗
NASA NTRS2013

RF Reference Switch for Spaceflight Radiometer Calibration

The goal of this technology is to provide improved calibration and measurement sensitivity to the Soil Moisture Active Passive Mission (SMAP) radiometer. While RF switches have been used in the past to calibrate microwave radiometers, the switch used on SMAP employs several techniques uniquely tailored to the instrument requirements and passive remote-sensing in general to improve radiometer performance. Measurement error and sensitivity are improved by employing techniques to reduce thermal gradients within the device, reduce insertion loss during antenna observations, increase insertion loss temporal stability, and increase rejection of radar and RFI (radio-frequency interference) signals during calibration. The two legs of the single-pole double-throw reference switch employ three PIN diodes per leg in a parallel-shunt configuration to minimize insertion loss and increase stability while exceeding rejection requirements at 1,413 MHz. The high-speed packaged diodes are selected to minimize junction capacitance and resistance while ensuring the parallel devices have very similar I-V curves. Switch rejection is improved by adding high-impedance quarter-wave tapers before and after the diodes, along with replacing the ground via of one diode per leg with an open circuit stub. Errors due to thermal gradients in the switch are reduced by embedding the 50-ohm reference load within the switch, along with using a 0.25-in. (approximately equal to 0.6-cm) aluminum prebacked substrate. Previous spaceflight microwave radiometers did not embed the reference load and thermocouple directly within the calibration switch. In doing so, the SMAP switch reduces error caused by thermal gradients between the load and switch. Thermal issues are further reduced by moving the custom, highspeed regulated driver circuit to a physically separate PWB (printed wiring board). Regarding RF performance, previous spaceflight reference switches have not employed high-impedance tapers to improve rejection. The use of open-circuit stubs instead of a via to provide an improved RF short is unique to this design. The stubs are easily tunable to provide high rejection at specific frequencies while maintaining very low insertion loss in-band.

Knuble, Joseph↗
DOE OSTI2022

Design and Verification of An Open-Circuit Electro-Hydraulic Actuator System with An Integrated Electro-Hydraulic Unit

This paper proposes an electro-hydraulic actuator (EHA) system, and two novel-designed electro-hydraulic units (EHU) consisting of a fixed-displacement hydraulic pump and a variable-speed electric motor. Both the novel EHU designs integrate an electric machine and a hydraulic machine in a single unit, featuring compactness and power density. However, they differ for salient aspects such as power and electric machine cooling system. The EHA system features an open circuit design, where hydraulic hoses connect the EHU with a tank, a valve manifold, and the hydraulic cylinder. In this way, the proposed EHA technology can be used to implement distributed hydraulic actuation in a vehicle without requiring changes to the hydraulic actuators or at the overall layout of the hydraulic components with respect to the original vehicle design. A dedicated test rig is developed to verify the performance of the proposed EHA system. The efficiency of the EHA is measured in a steady state and under a realistic duty cycle of a commercial compact loader. The measured efficiency of the system can reach 54% with up to 20kN load and 6kW power level.

42 ENGINEERING↗