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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS2011

Feasibility of Ultraviolet Light Emitting Diodes as an Alternative Light Source for Photocatalysis

The objective of this study was to determine whether ultraviolet light emitting diodes (UV-LEDs) could serve as an alternative photon source efficiently for heterogeneous photocatalytic oxidation (PCO). An LED module consisting of 12 high-power UV-A LEDs was designed to be interchangeable with a UV-A fluorescent black light blue (BLB) lamp in a Silica-Titania Composite (STC) packed bed annular reactor. Lighting and thermal properties were characterized to assess the uniformity and total irradiant output. A forward current of (I(sub F)) 100 mA delivered an average irradiance of 4.0 m W cm(exp -2), which is equivalent to the maximum output of the BLB, but the irradiance of the LED module was less uniform than that of the BLB. The LED- and BLB-reactors were tested for the oxidization of 50 ppmv ethanol in a continuous flow-through mode with 0.94 sec space time. At the same irradiance, the UV-A LED reactor resulted in a lower PCO rate constant than the UV-A BLB reactor (19.8 vs. 28.6 nM CO2 sec-I), and consequently lower ethanol removal (80% vs. 91%) and mineralization efficiency (28% vs. 44%). Ethanol mineralization increased in direct proportion to the irradiance at the catalyst surface. This result suggests that reduced ethanol mineralization in the LED- reactor could be traced to uneven irradiance over the photocatalyst, leaving a portion of the catalyst was under-irradiated. The potential of UV-A LEDs may be fully realized by optimizing the light distribution over the catalyst and utilizing their instantaneous "on" and "off' feature for periodic irradiation. Nevertheless, the current UV-A LED module had the same wall plug efficiency (WPE) of 13% as that of the UV-A BLB. These results demonstrated that UV-A LEDs are a viable photon source both in terms of WPE and PCO efficiency.

Levine, Langanf H.↗
DOE OSTI2020

Lighting controls: not just for lighting anymore!

For the last few years, networked lighting controls (NLCs) have promised significant energy savings beyond what is achieved through a basic LED retrofit. At the same time, NLCs can substantially increase the cost and complexity of the lighting retrofit. And as lighting system wattage declines because of the increasing efficiency of LEDs, advanced controls have less lighting energy to save and the cost-effectiveness of the NLC investment decreases. But NLCs can be leveraged to achieve significant energy savings and value by enhancing control of other building systems. Integrating NLC with control of heating, ventilation and air conditioning (HVAC), plug load control, space utilization, and grid services all enhance the value of your NLC investment. There are already a few NLC products on the market that are capable of providing these enhanced benefits. Manufacturers and entrepreneurs are working hard to expand the impact of these products. But does system interoperability work? Can it be deployed at scale? Slipstream, NEEA and Pacific Northwest National Laboratory (PNNL) have all been attempting to answer these questions in recent pilot projects and describe the outcomes in this paper.

Hackel, Scott↗
DOE OSTI2022

Light mesons with one dynamical gluon on the light front

We obtain the light meson mass spectroscopy from the light-front quantum chromodynamics (QCD) Hamiltonian, determined for their constituent quark-antiquark and quark-antiquark-gluon Fock components, together with a three-dimensional confinement. The eigenvectors of the light-front effective Hamiltonian provide a good quality description of the pion electromagnetic form factor, decay constant, and the valence quark distribution functions following QCD scale evolution. We also show that the pion's gluon densities can be probed through the pion-nucleus induced $J/ψ$ production data. Our pion parton distribution functions provide excellent agreement with $J/ψ$ production data from widely different experimental conditions.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Angular distribution of polarized spontaneous emissions and its effect on light extraction behavior in InGaN-based light emitting diodes

Angular intensity distributions of differently polarized light sources in multiple quantum wells (MQWs) and their effects on extraction behavior of spontaneous emission from light emitting diode (LED) chips have been studied. Theoretical calculation based on k·p approximation, ray tracing simulation and angular electroluminescence measurement were applied in this work. It is found that the electron-hole recombination in the InGaN MQWs produces a spherical distribution of an s-polarized source and a dumbbell-shaped p-polarized source. Light rays from different polarized sources experience different extraction processes, determining the polarization degree of electro-luminescence and extraction efficiency of LEDs.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Using Light for Research at the Advanced Light Source

Ziheng Yao, ALS Doctoral Fellow in Residence and a Ph.D. student at Stony Brook University, will share how he uses infrared light at the ALS to study a range of samples, including battery and biological materials, meteors, and more. The Advanced Light Source is a DOE Office of Science User Facility. The International Day of Light is recognized by the United Nations Educational, Scientific and Cultural Organization (UNESCO).

36 MATERIALS SCIENCE↗
DOE OSTI2017

Troffer Retrofits: Northern Arizona University Building Shines with Innovative Lighting Design - Interior Lighting Campaign

This case study describes lighting efficiency measures in Northern Arizona University's Student and Academic Services Building. The building was designed with space-by-space lighting controls to enable scheduling and dimming in offices, conference rooms, and classrooms, and achieved 46% energy savings compared to standard code-compliant lighting.

education, lighting, controls, dimming, classroom,↗
DOE OSTI2018

Blue photons excited highly chromatic red light emitting K3La(PO4)2:Pr3+ phosphors for white light emitting diodes

Highlights: • K{sub 3}La(PO{sub 4}){sub 2}:Pr{sup 3+} phosphors were investigated as an alternative for red light. • Highly chromatic red emission was realized upon blue excitation. • The phosphor has high color purity ∼ 97.8% and yield ∼27%. - Abstract: Highly chromatic blue photons excited red emitting K{sub 3}La(PO{sub 4}){sub 2}:Pr{sup 3+} (0–1.8 mol%) phosphors were synthesized by solution combustion method. The resulted phosphors showed peanut like morphology and had a monoclinic phase with space group P2{sub 1}/m. The photoluminescence studies disclosed that the phosphor emits red light due to the {sup 1}D{sub 2} → {sup 3}H{sub 4} and {sup 1}D{sub 2} → {sup 3}H{sub 5} transition of the Pr{sup 3+} ions under blue photons excitation. The optimal concentration for the Pr{sup 3+} ions were optimized to be 1.2 mol% after which concentration quenching occurred. Dipole-dipole interaction among the dopant ions was found to be responsible for the concentration quenching. X-ray photoelectron spectroscopy results depicted that Pr was present in the (+3) valance state in the phosphor. The photometric results suggest that the phosphor with a high color purity ∼ 97.8% and enough quantum yield ∼27% could be an eventual choice as the red component for white light emitting diodes.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Computational Modeling of Exciton-Bath Hamiltonians for Light Harvesting 2 and Light Harvesting 3 Complexes of Purple Photosynthetic Bacteria at Room Temperature

Light harvesting 2 (LH2) complex is the primary component of the photosynthetic unit of purple bacteria that is responsible for harvesting and relaying excitons. The electronic absorption line shape of LH2 contains two major bands at 800 and 850 nm wavelength regions. Under low light conditions, some species of purple bacteria replace LH2 with light harvesting 3 (LH3), a variant form with almost the same structure as the former but with distinctively different spectral features. The major difference between the absorption line shapes of LH2 and LH3 is the shift of the 850 nm band of the former to a new 820 nm region. The microscopic origin of this difference has been the subject of some theoretical/computational investigations. However, the genuine molecular level source of such a difference is not clearly understood yet. This work reports a comprehensive computational study of LH2 and LH3 complexes so as to clarify different molecular level features of LH2 and LH3 complexes and to construct simple exciton-bath models with a common form. All-atomistic molecular dynamics simulations of both LH2 and LH3 complexes provide detailed molecular level structural differences of bacteriochlorophylls (BChls) in the two complexes, in particular, in their patterns of hydrogen bonding (HB) and torsional angles of the acetyl group. Time-dependent density functional theory calculation of the excitation energies of BChls for structures sampled from the MD simulations suggests that the observed differences in the HB and torsional angles cannot fully account for the experimentally observed spectral shift of LH3. Potential sources that can explain the actual spectral shift of LH3 are discussed, and their magnitudes are assessed through fitting of experimental line shapes. Furthermore, these results demonstrate the feasibility of developing simple exciton-bath models for both LH2 and LH3, which can be employed for large-scale exciton quantum dynamics in their aggregates.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

An Efficient Copper-Based Redox Shuttle Bearing a Hexadentate Polypyridyl Ligand for DSCs under Low-Light Conditions

A Cu complex featuring a hexadentate ligand was synthesized and evaluated as a redox shuttle in dye-sensitized solar cell (DSC) devices, which exhibited excellent performance under low-light conditions. Cu-based redox shuttles (RSs) have been shown to perform remarkably well under low-light conditions; however, most of the known Cu-based RSs employ bidentate pyridyl ligands and often require bulky flanking groups adjacent to the nitrogen donors of these ligands to prevent distortion and binding of exogenous Lewis bases such as 4- tert -butylpyridine (TBP) that are added to enhance cell performance. Without the bulky substituents, the bidentate ligands are susceptible to ligand exchange with TBP. In this context, we have developed a Cu-based RS with a preorganized multidentate ligand designed to facilitate efficient electron transfer kinetics and high stability via the chelate effect. The Cu system, [Cu(bpyPY4)] 2+/+ , reported here is supported by the hexadentate polypyridyl ligand bpyPY4 (6,6'-bis(1,1-di(pyridine-2-yl)ethyl)-2,2'-bipyridine) and examined as a RS in DSCs. From X-ray crystallography and variable-temperature 1 H NMR studies, bpyPY4 provides a dynamic coordination environment around the metal center. Cyclic voltammetry and UV–visible and NMR spectroscopy indicate that noncoordinated pyridyl donors block binding of TBP to copper. DSC devices using [Cu(bpyPY4)] 2+/+ as the redox electrolyte gave a power conversion efficiency (PCE) value of 4.9% under 1 sun illumination (100 mW/cm 2 ). Strikingly, the device performance increased to 11.11% when irradiated with 2400 lux (0.5 mW/cm 2 ) via a fluorescent lamp light source and improved further to 15.2% PCE at 13500 lux (2.10 mW/cm 2 ). In conclusion, the Cu redox shuttle is an intriguing candidate for implementation with narrow band gap sensitizers with low oxidation potentials, which are important for high photocurrent DSC devices.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Enhancing light out-coupling of organic light-emitting devices using indium tin oxide-free low-index transparent electrodes

With its increasing and sufficient conductivity, the conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has been capable of replacing the widely used but less cost-effective indium tin oxides (ITOs) as alternative transparent electrodes for organic light-emitting devices (OLEDs). Intriguingly, PEDOT:PSS also possesses an optical refractive index significantly lower than those of ITO and typical organic layers in OLEDs and well matching those of typical OLED substrates. Optical simulation reveals that by replacing ITO with such a low-index transparent electrode, the guided modes trapped within the organic/ITO layers in conventional OLEDs can be substantially suppressed, leading to more light coupled into the substrate than the conventional ITO device. By applying light out-coupling structures onto outer surfaces of substrates to effectively extract radiation into substrates, OLEDs using such low-index transparent electrodes achieve enhanced optical out-coupling and external quantum efficiencies in comparison with conventional OLEDs using ITO.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Ultrastrong light-matter coupling in electrically doped microcavity organic light emitting diodes

The coupling of the electromagnetic field with an electronic transition gives rise, for strong enough light-matter interactions, to hybrid states called exciton-polaritons. When the energy exchanged between light and matter becomes a significant fraction of the material transition energy an extreme optical regime called ultrastrong coupling (USC) is achieved. We report a microcavity embedded p-i-n monolithic organic light emitting diode working in USC, employing a thin film of squaraine dye as active layer. A normalized coupling ratio of 30% has been achieved at room temperature. These USC devices exhibit a dispersion-less angle-resolved electroluminescence that can be exploited for the realization of innovative optoelectronic devices. Our results may open the way towards electrically pumped polariton lasers.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Exploring Mbar shock conditions and isochorically heated aluminum at the MEC end station of the LCLS

Recent experiments performed at the Matter in Extreme Conditions end station (MEC) of the Linac Coherent Light Source (LCLS) have demonstrated the first spectrally resolved measurements of plasmons from isochorically heated aluminum. The experiments have been performed using a seeded 8-keV x-ray laser beam as a pump and probe to both volumetrically heat and scatter x-rays from aluminum. Collective x-ray Thomson scattering spectra show a well-resolved plasmon feature that is down-shifted in energy by 19 eV. In addition, Mbar shock pressures from laser-compressed aluminum foils using Velocity Interferometer System for Any Reflector (VISAR) have been measured. The combination of experiments fully demonstrates the possibility to perform warm dense matter studies at the LCLS with unprecedented accuracy and precision.

INST, MATSCI, PHYS, XFEL↗
DOE OSTI2014

High light extraction efficiency in bulk-GaN based volumetric violet light-emitting diodes

We report on the light extraction efficiency of III-Nitride violet light-emitting diodes with a volumetric flip-chip architecture. We introduce an accurate optical model to account for light extraction. We fabricate a series of devices with varying optical configurations and fit their measured performance with our model. We show the importance of second-order optical effects like photon recycling and residual surface roughness to account for data. We conclude that our devices reach an extraction efficiency of 89%.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Texturing the cathode of white organic light-emitting diodes with a lattice of nanoscale scatterers for enhanced light out-coupling

The external quantum efficiency of white organic light-emitting diodes is often limited by light out-coupling losses due to surface plasmons. We demonstrate how texturing of the metal-cathode surface using a two-dimensionally periodic lattice of nanoscale scatterers with limited disorder can be used to reduce plasmonic losses while simultaneously enhancing both the light out-coupling and the spontaneous-emission rate of the excitons. We use electrodynamic simulations and statistical modeling to explore the relationship between the topology of the surface texture and its corresponding scattering efficiency. From this, we outline attributes of textures that can most enhance device performance.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Light weakly interacting massive particles

Light WIMPs are dark matter particle candidates with weak scale interaction with the known particles, and mass in the GeV to 10's of GeV range. Hints of light WIMPs have appeared in several dark matter searches in the last decade. The unprecedented possible coincidence into tantalizingly close regions of mass and cross section of four separate direct detection experimental hints and a potential indirect detection signal in gamma rays from the galactic center, aroused considerable interest in our field. Even if these hints did not so far result in a discovery, they have had a significant impact in our field. Herein we discuss the evidence for and against light WIMPs as dark matter candidates and discuss future relevant experiments and observations

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Light mesons within the basis light-front quantization framework

In this work, we study the light-unflavored mesons as relativistic bound states in the nonperturbative Hamiltonian formalism of the basis light-front quantization approach. The dynamics for the valence quarks of these mesons is specified by an effective Hamiltonian containing the one-gluon exchange interaction and the confining potentials both introduced in our previous work on heavy quarkonia, supplemented additionally by a pseudoscalar contact interaction. We diagonalize this Hamiltonian in our basis function representation to obtain the mass spectrum and the light-front wave functions (LFWFs). Based on these LFWFs, we then study the structure of these mesons by computing the electromagnetic form factors, the decay constants, the parton distribution amplitudes, and the parton distribution functions. Our results are comparable to those from experiments and other theoretical models.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

GATEWAY Report Brief: OLED Lighting in the Offices of Aurora Lighting Design, Inc.

Summary of a GATEWAY report evaluation at the offices of Aurora Lighting Design, Inc., in Grayslake, IL, where the GATEWAY program conducted its first investigation involving OLED lighting. The project experienced several challenges, but also highlighted a number of promising attributes – which indicate that with continued improvements in efficacy, longevity, size, and flexibility, OLEDs could provide a new tool for creative and effective lighting.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2016

GATEWAY Demonstrations: Tuning the Light in Senior Care: Evaluating a Trial LED Lighting System at the ACC Care Center in Sacramento, CA

The GATEWAY program documented the performance of tunable-white LED lighting systems installed in several spaces within the ACC Care Center, a senior-care facility in Sacramento, CA. The project results included energy savings and improved lighting quality, as well as other possible health-related benefits that may have been attributable, at least in part, to the lighting changes.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗