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Results for “Solid State Lighting”

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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Electrothermal Micromirror Adaptive Illumination

As part of the Cyclotron Road program, Helux Lighting aimed to develop a highly adaptive illumination source based on microelectromechanical system (MEMS) technology and next-generation solid state lighting. Solid state lighting has caused a paradigm shift in the industry. Developing systems that put light only where it is needed can reduce energy consumption and have an impact on the well-being of the population by eliminating glare and wasted light. Full control could also reduce the disruption of sensitive ecosystems caused by light pollution. The most advanced fixtures available today are based on mechanical components that are bulky and expensive. The track light is the only inexpensive lighting system that permits redirection and, in some cases, spot size by motorized optical components. The most advanced light fixtures today are composed of a strategically arranged array of LEDs. More recent developments in the research community include dynamic liquid crystal lenses but fail to realize simultaneous dynamic steering and spot size. In this project, Helux worked on the capability development of their controllable micromirror combined with state-of-the-art solid state lighting to electronically adjusting light position, brightness, and illumination area.

42 ENGINEERING↗
DOE OSTI2015

2015 Project Portfolio: Solid-State Lighting

Overview of SSL projects currently funded by DOE, and those previously funded but since completed. Each profile includes a brief technical description, as well as information about project partners, funding, and the research period. This report is updated annually.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2012

Solid-State Lighting: Cantilever Epitaxy Process Wins R&D 100 Award

Sandia National Laboratories received an R&D 100 Award from R&D Magazine for development of a new process for growing gallium nitride on an etched sapphire substrate. The process, called cantilever epitaxy, promises to make brighter and more efficient green, blue, and white LEDs.

R&D 100 Award↗
DOE OSTI2015

Solid-State Lighting R&D Plan - 2015

Provides analysis and direction for ongoing R&D activities to advance SSL technology and increase energy savings, reviewing SSL technology status and trends for both LEDs and OLEDs and offering an overview of the current DOE SSL R&D project portfolio.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2011

High Extraction Phosphors for Solid State Lighting

We have developed high-index, high efficiency bulk luminescent materials and novel nano-sized phosphors for improved solid-state white LED lamps. These advances can potentially contribute to reducing the loss in luminous efficiencies due to scattering, re-absorption, and thermal quenching. The bulk and nanostructured luminescent materials investigated are index matched to GaN and have broad and size-tunable absorption bands, size and impurity tuned emission bands, size-driven elimination of scattering effects, and a separation between absorption and emission bands. These innovations were accomplished through the use of novel synthesis techniques suitable for high volume production for LED lamp applications. The program produced a full-color set of high quantum yield phosphors with high chemical stability. In the bulk phosphor study, the ZnSeS:Cu,Ag phosphor was optimized to achieve >91% efficiency using erbium (Er) and other activators as sensitizers. Detailed analysis of temperature quenching effects on a large number of ZnSeS:Cu,Ag,X and strontium- and calcium-thiogallate phosphors lead to a breakthrough in the understanding of the anti-quenching behavior and a physical bandgap model was developed of this phenomena. In a follow up to this study, optimized phosphor blends for high efficiency and color performance were developed and demonstrated a 2-component phosphor system with good white chromaticity, color temperature, and high color rendering. By extending the protocols of quantum dot synthesis, large nanocrystals, greater than 20 nm in diameter were synthesized and exhibited bulk-like behavior and blue light absorption. The optimization of ZnSe:Mn nanophosphors achieved ~85% QE The limitations of core-shell nanocrystal systems were addressed by investigating alternative deltadoped structures. To address the manufacturability of these systems, a one-pot manufacturing protocol was developed for ZnSe:Mn nanophosphors. To enhance the stability of these material systems, the encapsulation of ZnSeS particle phosphors and ZnSeS screens with Al 2 O 3 and TiO 2 using ALD was shown to improve the stability by >8X and also increased the luminescence efficiency due to improved surface passivation and optical coupling. A large-volume fluidized bed ALD system was designed that can be adapted to a commercial ALD or vapor deposition system. Throughout the program, optical simulations were developed to evaluate and optimize various phosphor mixtures and device configurations. For example, to define the scattering properties of nanophosphors in an LED device or in a stand-off screen geometry. Also this work significantly promoted and assisted in the implementation of realistic phosphor material models into commercial modeling programs.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2015

Efficient Solid‐State Light‐Emitting CuCdS Nanocrystals Synthesized in Air

Abstract Semiconductor nanocrystals (NCs) possess high photoluminescence (PL) typically in the solution phase. In contrary, PL rapidly quenches in the solid state. Efficient solid state luminescence can be achieved by inducing a large Stokes shift. Here we report on a novel synthesis of compositionally controlled CuCdS NCs in air avoiding the usual complexity of using inert atmosphere. These NCs show long‐range color tunability over the entire visible range with a remarkable Stokes shift up to about 1.25 eV. Overcoating the NCs leads to a high solid‐state PL quantum yield (QY) of ca. 55 % measured by using an integrating sphere. Unique charge carrier recombination mechanisms have been recognized from the NCs, which are correlated to the internal NC structure probed by using extended X‐ray absorption fine structure (EXAFS) spectroscopy. EXAFS measurements show a Cu‐rich surface and Cd‐rich interior with 46 % Cu I being randomly distributed within 84 % of the NC volume creating additional transition states for PL. Color‐tunable solid‐state luminescence remains stable in air enabling fabrication of light‐emitting diodes (LEDs).

Khan, Ali Hossain↗
DOE OSTI2017

Novel Transparent Phosphor Conversion Matrix with High Thermal Conductivity for Next Generation Phosphor-Converted LED-based Solid State Lighting

The low thermal conductivity of state-of-the-art polymer encapsulants (k ~ 0.15 Wm-1K-1) limits the efficiency and power density of current phosphor conversion light emitting diodes (pc-LEDs). The technical objective of this project was to demonstrate synthesis and processing schemes for the fabrication of polymer hybrid encapsulants with a thermal conductivity exceeding k = 0.4 Wm-1K-1 for LED applications. The ‘hybrid polymer’ approach encompasses the dispersion of high thermal conductivity particle fillers (zinc oxide, ZnO as well as the alpha-polymorph of alumina, Al2O3) within a polysiloxane matrix (poly(dimethylsiloxane), PDMS as well as poly(phenyl methyl siloxane), PPMS) to increase the thermal conductivity while maintaining optical transparency and photothermal stability at levels consistent with LED applications. To accomplish this goal, a novel synthesis method for the fabrication of nanosized ZnO particles was developed and a novel surface chemistry was established to modify the surface of zinc oxide particle fillers and thus to enable their dispersion in poly(dimethyl siloxane) (PDMS) matrix polymers. Molecular dynamics and Mie simulations were used to optimize ligand structure and to enable the concurrent mixing of particles in PDMS/PPMS embedding media while also minimizing the thermal boundary resistance as well as optical scattering of particle fillers. Using this approach the synthesis of PDMS/ZnO hybrid encapsulants exhibiting a thermal conductivity of 0.64 Wm-1K-1 and optical transparency > 0.7 mm-1 was demonstrated. A forming process based on micromolding was developed to demonstrate the forming of particle filled PDMS into film and lens shapes. Photothermal stability testing revealed stability of the materials for approximately 4000 min when exposed to blue light LED (450 nm, 30 W/cm2). One postgraduate and seven graduate students were supported by the project. The research performed within this project led to fifteen publications in peer-reviewed journals and one patent application. The grant stimulated a multi-investigator research collaborations among seven investigators at Carnegie Mellon University to address the challenge of encapsulants in pc-LED applications. The grant also catalyzed the future collaboration between researchers at Carnegie Mellon University and OSRAM Sylvania to address challenges associated with the use if polymers in LED applications.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Li{sub 3}Gd{sub 3}Te{sub 2}O{sub 12}:Eu{sup 3+}- an intense red phosphor for solid state lighting applications

Li{sub 3}Gd{sub 3−3x}Eu{sub 3x}Te{sub 2}O{sub 12} (x=0.05−1.0) phases with garnet structure were synthesized by high temperature solid state reaction and the photoluminescence properties were investigated. The appearance of bands due to intra 4 f transitions of Gd{sup 3+} in the excitation spectra recorded by monitoring the 612 nm emission line of the activator indicates Gd{sup 3+}→Eu{sup 3+} energy transfer in this host lattice. Under 395 nm excitation, the electric dipole transition is predominant in the emission spectrum of Eu{sup 3+} and is in agreement with the C{sub 2} point group (noncentrosymmetric) of the EuO{sub 8} polyhedron. The critical concentration of the Eu{sup 3+} activator in this series was found to be 0.6 (x=0.2) above which, concentration quenching occurs. The emission intensity of the phosphor composition, Li{sub 3}Gd{sub 2.4}Eu{sub 0.6}Te{sub 2}O{sub 12} is ~4 times that of the commercial sample of Y{sub 2}O{sub 3}:Eu{sup 3+} phosphor. - Highlights: • New Eu{sup 3+} doped garnet. • Intense electric dipole emission. • Gd{sup 3+}→Eu{sup 3+} energy transfer.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗