High Power White LED Technology for Solid State Lighting Paul S ...

High Power White LED Technologyfor Solid State LightingPaul S. MartinJ. Bhat, , C.-H. Chen, D. Collins, W. Goetz, R. Khare, , A. Kim, M. Krames, , C.Lowery, M. Ludowise, , G. Mueller, R. Mueller-Mach, Mach, S. Rudaz, , D. Steigerwald,S. Stockman, S. Subramanya, , S-C S C Tan, J. Thompson, T. Trottier1 Copyright (c) Lumileds Lighting LLC Company Confidential

High Power White LEDsWho is Lumileds• Fully integrated light source supplier that co-develops optimized system solutions!• LED dice• LuxeonPower Light Sources• Arrays of High Flux LEDs ona metal core PCB• Automotive, Traffic Signals, Signage & Contour Solutions2 Copyright (c) Lumileds Lighting LLC Company

High Power White LEDsOutline• Competition in the market for Illumination, Incandescent & Fluorescent Bulbs.• LED Metrics• Options for making white light from LEDs• Lumileds power white LED performance• Some interesting demos3 Copyright (c) Lumileds Lighting LLC Company

Illumination MarketsHow Much Energy is Used for Lighting• In 1999 the US used 3 Trillion kWhr of Electricity!• 20% or 600 Billion kWhr of Electicity generated was used in Lighting!• Incandescent/Hal. lamps burn 40% of electricity to produce 15% of light!• Fluorescent/HID lamps use 60% to produce 85% of light!• Illumination market is $60Billion/yr and growing slowly, ~2%/yr4 Copyright (c) Lumileds Lighting LLC Company

Illumination MarketsIncandescent Bulbs• Incandescent = hot light, emitted from a (tungsten) filament at around 2800 o K• Disadvantages:• mostly infra-redred• glass vacuum envelope & filament both break easily•

Illumination MarketsFluorescent Bulbs• Fluorescent = cold light, emitted by phosphors excited by gas discharge.• Advantages:• High efficiency 80+lm/W & High Flux klm/lamp• Moderate cost for large lamps 0.002$/lm• Disadvantages:• Lifetime short

Illumination MarketsAssumptions for using LEDs in lighting• LED lamps will be far more expensive than incandescent, halogen orfluorescent lamps for at least a decade.• The expensive LED lamp must pay for itself through lifetime energy andmaintenance savings.• The lighting industry has spoiled the users with superb color rendering andcolor control.• Near term LEDs must dominate monochrome and penetrate white niches!7 Copyright (c) Lumileds Lighting LLC Company

High Power White LEDsOutline• Competition in the market for Illumination, Incandescent & Fluorescent Bulbs.• LED Technology & metrics• Options for making white light from LEDs• Lumileds power white LED performance• Some interesting demos8 Copyright (c) Lumileds Lighting LLC Company

LED MetricsTower of Babble?optical power out / electric power in = Wall-Plug-Efficiency, WPE, (%,W/W)photons out / electrons in = External Quantum Efficiency, EQE, %photons internally generated / electrons in = Internal Quantum Efficiency , IQE, %photons out / photons generated = extraction efficiency, %, h extphoton energy / applied voltage (times electron charge) = electrical efficiency, %, h ellumens out / electric power in = luminous efficiency [lm/W]luminous efficacy, LE [lm/W] = luminous equivalent of the emission spectrumluminous efficiency = IQE*η ext*η el*LEIQE*η ext= EQEEQE*η el= WPEWPE*LE = lm/W9 Copyright (c) Lumileds Lighting LLC Company

LED MetricsLED SkulduggeryPaul’s Top 5 Sins1) Quoting EQE without Vf or WPE2) Quoting low duty factor results3) Quoting WPE without current orcurrent density & total power out.4) Quoting WPE without temperature5) Quoting Cd without FluxWhat am I hiding?1) Vf, power efficiency2) Thermal resistance, heating3) GaN in particular has strongdependence of WPE on currentnot much light comes out of adevice at very low currents!4) WPE is strongly dependent onjunction temperature forAlInGaP, less so for AlInGaN.5) Radiation pattern10 Copyright (c) Lumileds Lighting LLC Company10

LED MetricsTower of Babble take 2 for white LEDsHow well can a source reproduce “natural” colors = Color-Rendering-Index, Ra, %(100 = sunlight, 85 = office, 60 = cabinet/lantern light)Color Correlated Temperature = CCT, Kelvin(x,y coordinates normal to black body curve)Phosphor Converted LED = PCLEDLED photons pump phosphor which emits secondary,and longer, wavelength of light.Stoke’s shift = Difference in wavelength betweenabsorbed and emitted photons. Emitted photonsalways have longer wavelength, i.e. lowerenergy!0.90.80.70.60.50.40.310,000K2500K3300K5000KCIE1931Planckian locustungsten, 2850Khalogen, 3100Kdaylight, 6500K0.20.10.00.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.811 Copyright (c) Lumileds Lighting LLC Company11

High Power White LEDsOutline• Competition in the market for Illumination, Incandescent & Fluorescent Bulbs.• LED Technology & metrics• Options for making white light from LEDs• Lumileds power white LED performance• Some interesting demos12 Copyright (c) Lumileds Lighting LLC Company12

White Light from LEDsThree methods of Generating LED White Light• Each method has potential strengths!Red + Green + Blue LEDsUV LED + RGB PhosphorBinary ComplimentaryBlue PeakGreen PeakRed PeakUV LEDSpectrumCombinedSpectrumPhosphorEmissionPhosphorEmissionCombinedSpectrumBlue LEDSpectrum470 525 590 630 (nm)410 470 525 590 630 (nm)470 525 590 630 (nm)RGB LEDsUV LED + RGB phosphorBlue LED+Yellow phosphor13 Copyright (c) Lumileds Lighting LLC Company13

White Light from LEDsCombining Red, Green and Blue LEDs• Advantages:• Long term likely the most efficient!• Dynamic tuning of color temperature possible!• Excellent color rendering!• Very large color Gamut available!• Challenges• Color Feedback required today to account for LED degradation with h T & t!• Color mixing tricky!• Yellow-Green Gap!LEDCCFLNTSCEBU14 Copyright (c) Lumileds Lighting LLC Company14

Combining Red, Green and Blue LEDsLumileds LCD Backlight!• 20 Green, 10 Red, 10 Blue Luxeon’s, , ~ 1000 lumens!• Today LED Solution has 140% Color Gamut and 120% CCFL power!Both displays showingthe same slide(red only background)via a splitterCCFL solutionLED solution15 Copyright (c) Lumileds Lighting LLC Company15

White from RGB LEDsThe Yellow-Green Gap!• Eye Sensitivity Peaks right in the middle of the Yellow-Green GaP!6050Tj = 25ºCLEDsVCSEL40Conversion3020Best LaboratoryResultProductionAverage100450 470 490 510 530 550 570 590 610 630 650 85016 Copyright (c) Lumileds Lighting LLC Company16Wavelength (nm)

White Light from LEDsUV LED pumped RGB Phosphors• Advantages:• White point determined by phosphors ONLY! (i.e. tolerant to LED variation)• Excellent color rendering possible!• Theoretically “Simple to manufacture!” (Looks like TV or Fluorescent lamp exceptfor pump is now UV LED rather than electrons.)• Temperature stability of phosphors. (Can be great!)• Disadvantages• Potential for damaging UV light leakage.• Fundamental limits on efficiency due to phosphor conversion efficiency, Stokesshift, self absorption,…• Challenges• None available yet!?• Efficient Blue LED pumped phosphor not available yet?!• Color uniformity with angle!• Packaging must be robust to UV exposure.• Temperature stability of phosphors. (Great phosphors not available le in all colors!)17 Copyright (c) Lumileds Lighting LLC Company17

UV LED pumped RGB PhosphorsUV LED must be >2x Green LED WPE for same lm/W!• Downshift in color causes fundamental energy loss.• Scattering in phosphor + absorption in package (inc. phosphor) reduces rextractionefficiency! Today’s best package efficiency is ~50% for Blue + Yellow phosphor,UV + RGB phosphor likely to be even worse!Power Conversion (%)100%90%80%70%60%50%40%30%20%10%0%Assuming 50% pkg. Efficiency!370 380 390 400 410 420 430UV Pump Wavelength (nm)Red 630nmBlue 460nmGreen 540nmWhiteWhite + Pkg18 Copyright (c) Lumileds Lighting LLC Company18

White Light from LEDsWhite from Blue LED + Phosphor(s)• Advantages:• Simple and single Yellow phosphor versions available today!• Decent color rendering (Ra = 75 for Blue LED + Yellow Phosphor)• Temperature stability of phosphors. (Can be great!)• Disadvantages• Limits on efficiency due to phosphor conversion efficiency, Stokes shift, selfabsorption,…• Better color rendering (i.e. multi phosphor comes at cost of efficiency)• Challenges• Temperature stability of phosphors. (Great phosphors not available le in all colors)• Color uniformity vs. angle• Multi phosphor versions to improve color rendering19 Copyright (c) Lumileds Lighting LLC Company19

White from Blue LED + Phosphor(s)Today, PC LEDs are in the 20-30lm/W range!• Todays white LEDs are in the ~20-30lm/W range!0.90.8LED, T = 25CLED,T = 105CYAG:CeCe 3+ doped garnet family,e.g.(Y,Gd) 3 Al 5 O 120.70.6520510530540Planckian locusCIE1931Combined with the same LED, Ce 3+phosphors hit the Planckian at differentcolor temperatures:0.50.40.30.20.1500490480470460450 nm10,000K5000K3300K2500K5906006206300.00.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8640706050403020100CCT=4000K, Ra=75400 500 600 700 800 nmRa = 75 is not great (good FL has 83)but it is OK for some applications.20 Copyright (c) Lumileds Lighting LLC Company20

White from Blue LED + Phosphor(s)Color Uniformity can be good for PC White!• CCT uniformity of 50-100K is sufficient for high quality illumination.CCT (K)5400520050004800460044004200400038003600340032003000800K80K-85 -75 -65 -55 -45 -35 -25 -15 -5 5 15 25 35 45 55 65 75 85Theta (degrees)21 Copyright (c) Lumileds Lighting LLC Company21

White from Blue LED + Phosphor(s)Progress on Temperature stability of Phosphorsmeasured on powders(Y,Gd)AG:Ce120000025 CI(T)/I(25C), %10080604020(Y,Gd)AG, 4 mol% Ce[Gd]0%255075radiance under 460 nm excitation5010000001001208000001506000002004000002000000400 450 500 550 600 650 700 750 800nm025 50 75 100 125 150Temperature, Cnovel phosphors with improvedcolor specs emerge; in this caseusing a Ce 3+ - Pr 3+ transfer ofexcitation energy and yieldingmore temperature stable behavior1200000251000000800000501001206000001502004000002000000400 500 600 700 80022 Copyright (c) Lumileds Lighting LLC Company22

White from Blue LED + Phosphor(s)The 2-phosphor2phosphor-converted LED – 2pcLED0.90.80.70.60.51 LED + 2 phosphors530TG:Eu5205405102.001.501.000.50820671937118combospecRa = 920.00400 500 600 700 800HP LED, T = 25CHP LED,T = 105CPlanckian locusPhosphorsCIE1931Series15Adding green and red to theblue of the LED opens a hugecolor gamut and allows forde-luxe white of any colortemperature – our best choice• SrGa 2 S 4 :Eu 2+ - green• SrS:Eu 2+ - red0.40.350049010,000K2500K3300K5000K590600SrS:Eu610620630combospec0.21.601.40Ra = 924801.201.000.800.10.604700.400.204600.00400 500 600 700 8000.00.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8640The dipole-allowed 5d-4ftransitions of Ce 3+ and Eu 2+are uniquely suited for colorconverters:high absorption, smallStoke’s shift23 Copyright (c) Lumileds Lighting LLC Company23

White Light from LEDsAll three white LED technologies share Threechallenges!1 Maximize efficiency in lm/W2 Maximize flux density in lm/package90 lm/bulb6 lm/W0.005 $/lm3 And of coarse reduce cost $/lm475 lm/bulb10 lm/W0.01 $/lm145 lm/bulb50 lm/W0.02 $/lm24 Copyright (c) Lumileds Lighting LLC Company24

High Power White LEDsOutline• Competition in the market for Illumination, Incandescent & Fluorescent Bulbs.• LED Technology & metrics• Options for making white light from LEDs• Lumileds power white LED performance• Some interesting demos25 Copyright (c) Lumileds Lighting LLC Company25

High Power White LEDsGold Wire BondLED ChipReflector CupCathode LeadEpoxy Dome LensAnode Leadn padsemitransparentcontactp padJunction area ~ 0.06mm 2Limitations of conventional 5mm Indicator LED lamps• Very high thermal resistance, >200°C/W,• Epoxy limited to

Die designLuxeon approach• Large area die for high power capability,• Electrode design for low spreading resistance,• Flip-chip configuration;• high extraction efficiency,• low thermal resistance,• ability to integrate electronics.Package design• Low thermal resistance package,• Stable, soft gel inner encapsulant,• Controlled radiation pattern and efficient optics.System designHigh Power White LEDs• Low thermal resistance board design,• Efficient secondary optical elements.27 Copyright (c) Lumileds Lighting LLC Company27

High Power White LEDsLumileds Luxeon TM Power LED Efficiency• Leading the charge into Solid State IlluminationProduction Typical R&D Demonstrations350mA If lm/W lm/LED lm/W lm/LEDRed 44 43 50 50Red-Orange 55 54 65 65Amber 36 36 44 44Green 25 30 50 55Blue 11 14 15 20White 18 22 30 3628 Copyright (c) Lumileds Lighting LLC Company28

LED TechnologyHaitz’s Law for LED Flux• LED Flux per package has doubled every 18-24 months for 30+ Years!!• 1965 Moore’s Law “# of Transistors/chip will double every 18-24 months!”1000Flux/Package (lumens)1001010.10.01Indicator LEDsLuxeon TM29 Copyright (c) Lumileds Lighting LLC Company290.0011960 1970 1980 1990 2000 2010Year

1000100High Power White LEDsLumileds Luxeon TM Series A & B LEDs• First ever White LED > 100lm!! (100.2lm and 15lm/W to boot!!)Luxeon Series B White LEDFlux output (lm)101Indicator White LEDLuxeon Series A White LED0.1All data AC 1%DF & 25C case30 Copyright (c) Lumileds Lighting LLC Company300.010.1 1 10 100 1000 10000Power input (mW)

High Power White LEDsLumileds 100 lumen Club!• These are the only LEDs that approach “Illumination” flux!Red 1000 105 February-01Amber 700 110 December-99Green 700 108 March-01White 1870 100.2 July-01White 1400 >110 1-Sep31 Copyright (c) Lumileds Lighting LLC Company31

High Power White LEDsWhat about Radiometric Power?!• State of the art 400nm indicator LEDs provide 15mW of power.• How much power can a Luxeon part generate? :-):If (mA) W/LED DateDeep Blue 430nm Dan 1400 Steigerwald >1.0 July-01Talk 4445-19 08:30 8/1/200132 Copyright (c) Lumileds Lighting LLC Company32

High Power White LEDsLumileds Luxeon TM Series B Cyan LED• Single Series B Cyan LED can replace an 80W bulb in an 8” traffic c ball!130 lm/bulb30 lm/W0.20? $/lm33 Copyright (c) Lumileds Lighting LLC Company33

High Power White LEDsLumileds Luxeon TM Ring• Fixture design by Philips Lighting and Lumileds.• 12 Luxeon’s, , ~240 lumens. Ring available Now!34 Copyright (c) Lumileds Lighting LLC Company34

High Power White LEDsOutline• Competition in the market for Illumination, Incandescent & Fluorescent Bulbs.• LED Technology and metrics• Comparison of options for making white LEDs• Lumileds power white LED performance• Some interesting demos35 Copyright (c) Lumileds Lighting LLC Company35

High Power White LEDsEvolution of LED Package Technology• Power LEDs can handle ~50x power of an Indicator LED!1962First Packaged LEDP max ~0.1W150-200 K/W1970Standard 5mm LampIndicator LEDP max ~0.2-0.4W50 K/W1994LumiLeds SnapLED TMFirst Power LEDP max ~0.6-4.0W9-14 K/W1998LumiLeds Luxeon TMToday’s Power LEDIndicator LED36 Copyright (c) Lumileds Lighting LLC Company36

High Power White LEDsLumileds Luxeon TM Power LED• Packages designed to handle 1-5W! 1High-Power Package:Improved thermal propertiesHeat sink body with good thermal interfaceSoft gel inner encapsulantIncluding power AlInGaN or AlInGaP orPhosphor Converted AlInGaN Chip:q jc ~ 12°C/WHigh optical efficiency > 95%37 Copyright (c) Lumileds Lighting LLC Company37

High Power White LEDsPotential Power Savings vs. Traditional Lighting• Todays white LEDs are in the ~20-30lm/W range, but still low flux!10080IncandescentPower Saved (%)604020HalogenCFLFluorescent00 25 50 75 100 125 150 175 200 225 250LED Efficiency (lm/W)38 Copyright (c) Lumileds Lighting LLC Company38

LED TechnologyIndicator LEDs vs. Power LEDs• Indicator LEDs have output powers < ~50mW and Thermal resistances > 50K/W10 0 Operating Point10 -1InGaN LEDsλ ~450 nmOperating PointOutput Power (W)10 -210 -3Power LED39 Copyright (c) Lumileds Lighting LLC Company3910 -4"5 mm" LED10 -3 10 -2 10 -1 10 0 10 1Input Power (W)