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Solid State Lighting: A Bright Opportunity for Nanotechnology to Impact Energy Efficiency

Solid State Lighting: A Bright Opportunity for Nanotechnology to Impact Energy Efficiency. Paul E. Burrows Pacific Northwest National Laboratory Richland, WA 99352 National Science Foundation Joint U.S. Korea NanoForum April 26 th 2007. Items for Discussion.

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Solid State Lighting: A Bright Opportunity for Nanotechnology to Impact Energy Efficiency

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  1. Solid State Lighting: A Bright Opportunity for Nanotechnology to Impact Energy Efficiency Paul E. Burrows Pacific Northwest National Laboratory Richland, WA 99352 National Science Foundation Joint U.S. Korea NanoForum April 26th 2007

  2. Items for Discussion • Solid state lighting as a high payoff research area in energy efficiency • The Department of Energy’s Basic Research Needs Report in Solid State Lighting • The role of nanoscience in optimizing next generation solid state lighting 2

  3. Artificial lighting was among the first inventions of mankind… • WARMTH • COOKING • LIGHT The First Invention 3

  4. Candle: 0.05 lumens per watt Gaslamp: 0.5 lumens per watt “Incandescent” Lightbulb 15 lumens per watt (5% efficient) Each subsequent improvement in lighting led to major lifestyle improvementsand improvements in the energy efficiency of the light 4

  5. Why does lighting impact energy conservation? • Lighting consumes 22% of the electricity generated in the U.S.A. • That’s 8% of the total energy consumption • Costs $50 billion per year • Releases 150 million tons of CO2 into the atmosphere each year • Much of it is 19th century technology with poor efficiency 5

  6. Lighting is a highly attractive target for reducing energy consumption! 1000 94 Quads 100 Energy 34 Quads Energy Consumption (Quads) Electricity 10 Lighting 6.9 Quads Projected U.S. 1998 1 1970 1980 1990 2000 2010 2020 Year We should be able to do better Efficiencies of energy technologies in buildings: Heating: 70 - 80% Elect. motors: 85 - 95% Fluorescent:20% Incandescent:5% 6

  7. Basic Research Needs for Solid State Lighting May 22-24, 2006 Workshop Chairs: Julia Phillips (Sandia National Labs) Paul Burrows (Pacific Northwest National Lab) Science Panel Chairs: LED: Jerry Simmons (SNL) Bob Davis (Carnegie Mellon U) OLED: Franky So (U of Florida) George Malliaras (Cornell) Cross-Cutting: Jim Misewich (BNL) Arto Nurmikko (Brown U) Darryl Smith (LANL) Total 79 participants 33% DOE Nat’l Labs 33% Universities Charge: identify transformational science Output:www.sc.doe.gov/bes/reports/list.html 20% Federal 14% Industry & others 7

  8. LED Science 12 Priority Research Directions (PRDs), each specific to an individual panel 2 Grand Challenges (GCs) which overarch all panels Workshop Output OLED Science Cross-cutting Science www.sc.doe.gov/bes/reports/list.html 8

  9. GRAND CHALLENGE 1:Rational design of solid-state lighting structures Today, light-emitting solid state materials are discovered rather than designed. The CHALLENGE: Can we designoptimized device components that assemble into a high efficiency charge-to-light conversion system? 9

  10. GRAND CHALLENGE 2: Control of radiative and nonradiative processes in light-emitting materials Light-emitting efficiency is determined by competition between radiative and non-radiative processes. The CHALLENGE: Can we understand and control the physics of photon generation and emission? 10

  11. Inorganic solid state lightingComposition and nanostructure determine color Colored LEDs: Red, Yellow - AlInGaP Blue, Green–InGaN White LEDs: Red + Green + Blue, or Blue + phosphor Postively charged carriers Semiconductor Bandgap Determines Color Negativelycharged carriers _ + - With applied voltage positive and negative charge carriers recombine - Energy may be released as light or heat - Theoretically they can be 100% efficient with unlimited life! (compared to incandescent which is 5% efficient, 2000 hour life) -Commercial LEDs can be expected to reach 50% efficiency and possibly more Buckingham Palace, London, England Lit by Lumileds LEDs Courtesy George Craford, Philips Lumileds 11

  12. Polymeric Molecular Light Emitting Materials:Molecular Structure Determines Color Phosphorescent Blue Green Red Fluorescent Weakly interacting molecules mean the photophysics of a film is controlled by the molecular structure of the fundamental building block

  13. Research-Scale Organic Lightbulbs General Electric: 2 ft OLED panel Universal Display Corporation Note the lack of a luminaire,- these are large area, low intensity emitters)

  14. Efficiency performance of OLED • Showa Denko K.K.:single layer phosphorescent polymer OLEDs external quantum efficiency of 17% (green) and 16% (blue) with durability of 350,000 hours at 100 cd/m2.  They will build a trial volume-production line by the middle of this year.  • Novaled claims "groundbreaking" results with its p-i-n OLED technology.. White top emission devices achieved a lifetime of 18,000 hours at 3 V and 1,000 cd/m2. Green top-emission OLEDs achieve 1,000 cd/m2 at 2.5 V and 95 cd/A (about 110 lm/W) These green devices are based on Ir(ppy)3. • Universal Display Corporation achieved 30 lm/W at 1000 cd/m2 (warm white). • Osram: 25 lm/W white polymer devices • Konica Minolta 60 lm/W, details unclear Novaled UDC Konica-Minolta Osram 14

  15. The problem of efficient white electrophosphorescence S1 Exciton levels must be even higher than blue T1 > 2.9 eV Triplet Excitons What is this molecule? ENERGY phosphorescence Ground state PHOSPHORESCENT DOPANTS CHARGE TRANSPORTING HOST MOLECULES

  16. The problem of efficient white electrophosphorescence S1 Exciton levels must be even higher than blue Triplet Excitons T1 ENERGY phosphorescence Ground state PHOSPHORESCENT DOPANT CHARGE TRANSPORTING MOLECULES

  17. 2.55 eV 2.64 eV 2.81 eV 2.84 eV 2.92 eV Aromatic and Heteroaromatic Chromophores with Interesting Triplet Exciton Energies All too volatile and do not form stable films! 3.08 eV TOO LOW 3.12 eV 3.04 eV Can we use these as building blocks?

  18. O A c t i v e P B r i d g e P O Phosphine Oxide (PO) CompoundsLinda Sapochak, Paul Burrows, Asanga Padmaperuma and Paul Vecchi inductive effect of P=O renders aryl groups electron deficient d+ d+ High triplet energy small molecule fragment Phosphine oxide point of saturation to isolate photophysics on bridge Outer groups enhance thermal properties 18

  19. Phosphorescence of phosphine oxides compared to brominated bridges (77K in DCM) PO1

  20. UV Light CuPc Ultraviolet Emission from PO1 OLEDs ?? ! eV EL Spectra 3.6 eV LiF/Al PO1 ITO ~4.7eV 338 nm 5.3 eV ?? ! eV LiF/Al PO1 NPD emission NPD ITO LiF/Al Alq3 No light PO1 ITO

  21. Summary • New lighting technology is “low-hanging fruit” in the drive for energy efficiency • Increase efficiency by 10X • Extrapolations of current technologies will not meet this goal • Old technologies; fundamental limits • Solid-state lighting can transform the way we light the world • Success requires: • Fundamental understanding to optimize current SSL approaches • Discovery research to reveal the basis for breakthrough efficiencies • SSL research will also drive discoveries in photon-matter interactions, new materials/structures, and new tools/methods www.sc.doe.gov/bes/reports/list.html 21

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