Solid State Lighting Michael Shur Rensselaer Polytechnic Institute ECSE, Physics and Broadband Center http://nina.ecse.rpi.edu/shur From a Torch to Blue and White LEDs and to Solid State Lamps Blue LED on Si, Courtesy of SET, Inc. http://nina.ecse.rpi.edu/shur/ 1 Research Areas • Plasma wave electronics –THz resonant emission and detection • Wide band gap materials and devices – MOSHFET, UV LEDs, SAW, polarization, transport • Sensitive skin – Flexible substrates, nano gauges, electrotextiles, TFTs, OTFTs • Novel device CAD – AIM-Spice, opto/thermo/micro CAD •Lab-on-the-WEB – http://nina.ecse.rpi.edu/shur/remote • Broadband center http://nina.ecse.rpi.edu/shur • Solid state lighting http://nina.ecse.rpi.edu/shur/ 2 Talk Outline • History of General and Electric Lighting • Advantages of Solid State Lighting • Introduction to Photometry and Colorimetry • Optimization of Solid State Lamps • Emerging applications • Vision http://nina.ecse.rpi.edu/shur/ 3 Lighting – prerequisite of human civilization • 500,000 years ago- first torch • 70,000 years ago – first lamp (wick) • 1,000 BC – the first candle • 1772 - gas lighting Yablochkov candle (1876) • 1784 Agrand lamp - Agrand lamp the first lamp relied on research (Lavoisier) • 1826 -Limelight - solid- state lighting device • 1876 – Yablochkov candle • 1879 – Edison bulb Limelight Edison bulb (1879) http://nina.ecse.rpi.edu/shur/ 4 History of Electric Lighting • 1876 Pavel Yablochkov. First electric lighting device • 1879 Thomas Alva Edison. Incandescent lamp • 1897 Nernst. Filament made of cerium oxide-based solid electrolyte. • 1900 Peter Cooper Hewitt. Mercury vapor lamp. 1903. A. Just and F. Hanaman. Tungsten filament • 1904 Moor. Discharge lamps with air • 1907 H. J. Round. First LED (SiC) • 1910 P. Claude. Discharge lamps with inert gases • 1938 GE and Westinghouse Electric Corporation Fluorescent lamps. http://nina.ecse.rpi.edu/shur/ 5 First LED (1907) http://nina.ecse.rpi.edu/shur/ 6 Lighting in James Joyce Room Shakespeare Hotel, Bernadinu 8/8 Vilnius, Lithuania (09/05/02) Incandescent First LED stamp Fluorescent http://nina.ecse.rpi.edu/shur/ 7 An improvementof luminousefficiencyby1%saves Innovation in Semiconductor Illumination: Data fromR. Haitz,F.Kish,J.Tsao, andJ.Nelson LED Penetration(%) 10 6 8 4 2 0 2000 2010 2020 2030 Benefits ofLEDLighting 2 billionsdollarsper year. Opportunities for National Impact (2000) Year 100 120 “Low Investment Model” 80 60 20 40 http://nina.ecse.rpi.edu/shur/ Cost Savings $USB/yr Investment Model” “High 8 Solid State Lighting 100 80 Efficiency (lm/W) 60 40 20 0 Incandescent Halogen Fluorescent White LED White LED (2000) (2010) 120 100 Lifetime (1000 h) 80 2002 60 40 20 0 Incandescent Halogen Fluorescent White LED White LED (2000) (2010) http://nina.ecse.rpi.edu/shur/ 9 Challenges of Solid State Lighting • Reduce cost • Improve efficiency of light generation • Improve efficiency of light extraction • Improve quality of light http://nina.ecse.rpi.edu/shur/ 10 Cost of Light Fluorescent tubes: •Incandescent bulbs: dollar per lumen 0.01 Dollar per lumen 1/1100 White LED: dollar per lumen Re LED: 0.25 (Lumileds) dollar per lumen0.1 0.66 (Nichia) http://nina.ecse.rpi.edu/shur/ 11 Evolution of lm/package and cost/lm for red LEDs After Roland Haitz Agilent Technologies http://nina.ecse.rpi.edu/shur/ 12 Challenges in epoxy ne light extraction θc ns Conventional LED chip grown active layer on an absorbing substrate. absorbing substrate High-brightness LED chip design (b) with thick transparent window layers Light escapes through 6 cones From A. Žukauskas, M. S. Shur, R. Gaska, MRS Bull. 26, 764, 2001. http://nina.ecse.rpi.edu/shur/ 13 Progress in AlInGaP LEDs After http://www.lumileds.com/technology/tutorial/slide2.htm http://nina.ecse.rpi.edu/shur/ 14 Light Extraction : TIP-LEDs from LumiLeDs 1000 high pressure sodium 1 kW TIP-LED t t 100 fluorescent 1 W a w mercury vapor 1 kW / n halogen 30 W e m Standard tungsten 60 W u 10 L AlGaInP/GaP red filtered tungsten 60 W Top contact 1 550 600 650 700 750 Peak wavelength (nm) After M.O. HOLCOMB et al. (2001), Compound Semiconductor 7, 59, 2001). http://nina.ecse.rpi.edu/shur/ 15 Photometry: Eye sensitivity 0 10 Photopic vision (cones) V'(λ) V(λ) @ High Illumination 10-1 10-2 Scotopic vision (rods) @ Low illumination 10-3 Relative Sensitivity 10-4 10-5 400 500 600 700 800 Wavelength (nm) Cones are red, green, and blue http://nina.ecse.rpi.edu/shur/ 16 Radiometry and Photometry Photopic vision eye sensitivity Watt Φ = 683 lm W × Φ V λ dλ υ ∫ e ( ) W/nm W/nm Luminous flux Wavelength (nm) I = dΦ dω = 683 lm W × I V λ dλ υ υ ∫ e ( ) Luminous intensity 1/60 of the luminous intensity per square centimeter of a (Candela = lm/sr – SI unit) blackbody radiating at the temperature of 2,046 Luminous efficiency: power into degrees Kelvin actuation of vision (lm/W) http://nina.ecse.rpi.edu/shur/ 17 How much light do you need? Type of Activity Illuminance (lx =lm/m2) Orientation and simple visual 30-100 tasks (public spaces) Common visual tasks (commercial, 300-1000 industrial and residential applications) Special visual tasks, including 3,000-10,000 those with very small or very low contrast critical elements http://nina.ecse.rpi.edu/shur/ 18 Colorimetry: Chromaticity Coordinates 1931 CIE color matching functions: purple, green, and blue 2.0 X = x λ S λ dλ _ ( ) ( ) blue ∫ z Y = y(λ) S(λ) dλ 1.5 green_ ∫ _ y Z = z(λ) S(λ) dλ x purple ∫ 1.0 X x = X + Y + Z 0.5 Y y = 0.0 X + Y + Z 350 400 450 500 550 600 650 700 750 Wavelength (nm) x+y+z = 1 http://nina.ecse.rpi.edu/shur/ 19 Color Coordinates [Y] 1.0 520 [G] Green 530 Planckian locus 0.8 540 510 (black body radiation) 560 0.6 500 580 A 2 3 0.4 E , 600 D , 0 65 B 0 0 4 0 0 Red , 0 0 620 6,00 0 490 C 0 [R] 0 10 640 ,0 00 700 Is it really that bad? 0.2 y Chromaticity Coordinate Just remember: 480 Blue [B] White is Black! [Z] 460 0.0 400 [X] 0.0 0.2 0.4 0.6 0.8 1.0 x Chromaticity Coordinate http://nina.ecse.rpi.edu/shur/ 20 Color Mixing •Red, green, blue appear as white •Red and blue appear as magenta •Green and blue give cyan 520 0.8 530 •Red and green give yellow 540 510 YG G 560 0.6 500 Y 580 0.4 600 C(W) O 620 490 640 700 0.2 y Chromaticity Coordinate Chromaticity y B 480 P 460 400 0.0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 x Chromaticity Coordinate http://nina.ecse.rpi.edu/shur/ 21 Color Rendering 1.0 0.8 Light grayish red Light bluish green 0.6 0.4 General Color Rendering 0.2 Index 0.0 1.0 R (CRI) 0.8 Dark grayish yellow Light blue a 0.6 integrates the reflectivity 0.4 y t i 0.2 data for 8 v i t 0.0 c e 1.0 specified samples l f e 0.8 Strong yellow green Light violet R Special color rendering 0.6 0.4 indices, 0.2 0.0 refer to six additional test 1.0 0.8 Moderate yellowish green Light reddish purple samples 0.6 R varies up to 100 0.4 a 0.2 100 is the best. 0.0 400 500 600 700 400 500 600 700 R might be negative Wavelength (nm) a http://nina.ecse.rpi.edu/shur/ 22 Generating White Light Phosphor-conversion Multichip white white LED LED Phosphor layer InGaN chip http://nina.ecse.rpi.edu/shur/ 23 How to Optimize Solid State lamp: maximize the objective function (K ) Fσ ()λ1, …, λn , I1, …, I n = σK + (1−σ )Ra where σ is the weight that controls the trade-off between the efficacy, K, and color rendering index, Ra λ1, λ2, λ3,… and I1, I2, I3 are the peak wavelengths and relative powers of the primary LEDs, respectively For a dichromatic lamp (two primary LEDs), the optimal solutions can be obtained by simple searching within the wavelength space involving complementary pairs of blue and yellow-green LEDs. http://nina.ecse.rpi.edu/shur/ 24 Optimization of Polychromatic Solid-State White Lamps 100 481/580 nm 464/543/613 nm 456/537/601 nm 20 80 489/591 nm 454/543/597 nm 0 60 380/569 nm -20 450/571 nm 40 3 Primary LEDs -40 2 primary LEDs 20 496/635 nm -60 0 General Color Rendering Color General Index 0 100 200 300 400 General Color Rendering Index 300 350 400 Luminous Efficacy (lm/W) Luminous Efficacy (lm/W) http://nina.ecse.rpi.edu/shur/ 25 General CRI, Luminous Efficacy, and LED Wavelengths of Optimized Polychromatic Lamps 99.5 660 2 LEDs 99 5 640 3 LEDs 98 4 4 LEDs 2 LEDs 620 95 3 LEDs 5 LEDs 600 90 4 LEDs 3 580 80 5 LEDs 560 70 60 540 50 520 40 30 500 20 General CRI 480 10 460 5 2 440 Peak wavelength (nm)Peak wavelength 420 320 340 360 380 400 420 440 2 5 10 20 30 40 50 60 70 80 90 95 98 9999.5 Luminous Efficacy (lm/W) General CRI The 30-nm line widths (A. Žukauskas, R. Vaicekauskas, F. Ivanauskas, R. Gaska and M. S. Shur, Optimization of White Polychromatic Semiconductor Lamps, Appl.