In this paper, we describe the formation and luminescence of a new garnet phosphor for light emitting diode (LED) based lighting, Lu2CaMg2(Si,Ge)3O12:Ce3+. The regions for garnet phase formation are initially described with respect to larger rare earth substitution and show reasonable correlation to previous crystal chemistry studies for the garnet parent structure. While the pure silicate phosphor also has apatite second phases, a significant amount of Ce3+ enters the garnet phase, giving Ce3+ luminescence that is significantly redder when compared to typical Al3+ garnet phosphors with quantum efficiencies comparable to commercial Ce3+ garnet phosphors. Potential reasons for the emission red shift and the high quantum efficiency are discussed. Finally, the performance of these new phosphors is tested within LED based lamps. Lamps using these phosphors can reach color temperatures required for general illumination lighting and also have comparable phosphor conversion efficiencies when compared to lamps using typical garnet phosphors.

A matrix addressable diode flat panel display has been fabricated using a carbon nanotube–epoxy composite as the electron emission source. Field-emission uniformity has been confirmed by measuring the I–V curves of pixels across the panel. This prototype display demonstrates well-lit pixels under ±150 V biasing signals. The “on” and “off” of the pixels are well controlled by the half voltage “off-pixel” method. Further improvement of this technology may lead to easy-to-make and inexpensive flat panel displays.

Advances in renewable and sustainable energy technologies critically depend on our ability to design and realize materials with optimal properties. Materials discovery and design efforts ideally involve close coupling between materials prediction, synthesis and characterization. The increased use of computational tools, the generation of materials databases, and advances in experimental methods have substantially accelerated these activities. It is therefore an opportune time to consider future prospects for materials by design approaches. The purpose of this Roadmap is to present an overview of the current state of computational materials prediction, synthesis and characterization approaches, materials design needs for various technologies, and future challenges and opportunities that must be addressed. The various perspectives cover topics on computational techniques, validation, materials databases, materials informatics, high-throughput combinatorial methods, advanced characterization approaches, and materials design issues in thermoelectrics, photovoltaics, solid state lighting, catalysts, batteries, metal alloys, complex oxides and transparent conducting materials. It is our hope that this Roadmap will guide researchers and funding agencies in identifying new prospects for materials design.

LED lamps using phosphor downconversion can be designed to replace incandescent or halogen sources with a "warm-white" correlated color temperature (CCT) of 2700-3200 K and a color rendering index (CRI) greater than 90. However, these lamps have efficacies of ∼70% of standard "cool-white" LED packages (CCT = 4500-6000 K; CRI = 75-80). In this report, we describe structural and luminescence properties of fluoride and oxyfluoride phosphors, specifically a (Sr,Ca) 3 (Al,Si)O 4 (F,O):Ce 3þ yellow-green phosphor and a K 2 TiF 6 :Mn 4þ red phosphor, that can reduce this gap and therefore meet the spectral and efficiency requirements for high-efficacy LED lighting. LED lamps with a warm-white color temperature (3088 K), high CRI (90), and an efficacy of ∼82 lm/W are demonstrated using these phosphors. This efficacy is ∼85% of comparable cool-white lamps using typical Y 3 Al 5 O 12 :Ce 3þ -based phosphors, significantly reducing the efficacy gap between warm-white and cool-white LED lamps that use phosphor downconversion.

The effect of Si4+−N3− incorporation on Ce3+ doped RE3Al5O12:Ce3+ (RE = Lu3+, Y3+, or Tb3+) garnet phosphors is described in this report. The addition of Si4+−N3− leads to distinct low-energy Ce3+ absorption and emission bands that are assigned to Ce3+ ions that have N3− in their local coordination. The combination of the typical Ce3+ emission in garnets with the low energy Ce3+ emission band results in a broad emission spectrum suited for white LED lamps with low color temperatures and good color rendering using only a single phosphor. The low-energy Ce3+ emission band has stronger quenching at high temperatures, a potential limitation. The mechanism for this quenching is discussed.

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The efficacy of solid-state lighting (SSL) based upon InGaN LEDs has improved by >10x over the past decade: the efficacy of cool white LEDs surpasses linear fluorescent lamp (LFLs) efficacies (>100 lm/W) and warm white 1W LEDs surpasses compact fluorescent lamps (CFLs) efficacies (>60-70 lm/W).

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