Lighting Your Path to the Future

Transcription

1 Lighting Your Path to the Future M. George Craford, CTO Philips Lumileds Lighting Company IMAPS Global Business Council November 14, 2007

2 Outline Power LED Technology Status and Trends Existing and Emerging Applications Challenges and Recent Developments for Solid State Lighting Buckingham Palace, London, England Lit by LUXEON LEDs 2

3 Outlook: LEDs vs. Conventional Light Sources Luminous Efficacy (lm/w) Light Source Description η L (lm/w) 500W High-pressure Na W Metal Halide 122 TL HE Tube Fluorescent 105 Halogen-IR Incandescent 30 Standard Incandescent 16 Hg vapor halogen high-pressure Na fluorescent Best lowcurrent LED metal halide halogen- IR Power LEDs Best highpower LED (LEDs) U.S. DOE roadmap Krames et al., IEEE J. Display Technol. 3, 160 (2007) 0 incandescent Emerging ~ 100 lm/w phosphor white power LEDs Expect ~ 160 lm/w power LED performance within the next 5 years Multi-primary white could outperform (need breakthrough green, red) 3

4 White LED Performance Cool CCT ~ ,000K Small 5mm LEDs Lower current density Lower forward voltage Power LEDs More lumens/package Lower cost per lumen Luminous Efficacy (lm/w) Small LED Lab results Small LED 2007 Small LED 2006 ~20 ma ~350 ma Current Density (A/cm 2 ) Power LED Lab results Power LED 2007 Power LED 2006 Power LED ~ % 60% 50% 40% 30% 20% 10% 0% Pump Blue WPE (est.) 4

5 The Four Elements of LED Technology Phosphors Package Device (chip) design Epitaxy and Materials Important metrics: External quantum efficiency: EQE = IQE x EXE Power conversion efficiency: PCE = EQE x E ph / Vf Luminous efficacy: LE = PCE x V(λ) 5

6 High-Power (> Watt Input) LED Performance External quantum efficiency, η ext 70% 60% 50% 40% 30% 20% 10% 0% In x Ga 1-x N (2) T j = 25 C High-power ( ~ > 1 Watt input) visible-spectrum LEDs (1) (3) (Al x Ga 1-x ) 0.52 In 0.48 P (3) V(λ) (4) 1) Philips Lumileds TFFC LEDs 2) Morita et al., Jpn. J. Appl. Phys. 43, 5945 (2004) 3) Nichia, ICNS-7 4) Philips Lumileds TIP LEDs InGaN Peak wavelength, λ p (nm) Maximum external quantum efficiencies in the blue Lower efficiency with increasing InN % (~ 2x reduction green) AlGaInP Fundamental bandstructure limitations at short wavelengths 6

7 Red, Green, Blue Color Mixing for Warm White RGB 540 Illumination 300 Red R - 615nm Blue - 460nm Green - 540nm CRI 90 CCT White Source Efficiency (lm/w) Blue WPE - 75% R-G540-B White LED for Illumination Red WPE - 75% Red WPE - 40% Red WPE - 20% Wavelength (nm) 0 0% 20% 40% 60% 80% Green LED Efficiency (WPE) If nitride RGB all reach 75% WPE (very unlikely requiring three miracles ) then the source efficacy would be ~280 lm/w before color mixing losses (possibly 15-30% which would imply about 200 lm/w 240 lm/w) If RGB all reach >40% WPE (much more reasonable to expect) then ~150 lm/w source would be achieved which would be color tuneable Green is the key for enabling color tuneable white illumination to occur 7

8 Recent Development: Improved Epitaxial Materials Process Reduces Efficiency Droop at High Current Densities * 100% 100% Normalized EQE (%) 90% 80% 70% 60% 50% 40% 30% 20% 10% PLL high current efficiency solution Current Production Normalized radiant flux (% max. W) 90% 80% 70% 60% 50% 40% 30% 20% 10% PLL high current efficiency solution Current Production 0% % Device input current (ma) Device current (ma) High efficiency maintained to over 1.5A >20% flux gain at high current densities (> 1.0A) Key step forward for achieving a high efficiency 1000lm emitter in a single 1mm 2 chip Auger effect is key issue. Improvement is to use a thicker active layer. (DH vs QW s) *Nate Gardner, et. al., presented at ICNS-7, Las Vegas, NV, September 16-21, 2007 *Yu-Chen Shen, et. al., Auger recombination in InGaN measured by photoluminescence, APL, (2007) 8

9 LED Chip Design (Al,Ga)InP-GaAs or (Al,Ga)InP-GaP wb pad (a) Thin AS (Al,Ga)InP GaAs GaAs DBR GaAs n-gap substrate (d) Thick TS p-type n-type n-type p-type host substrate p-gap p-wb pad (b) Thick AS n-gap substrate p-gap (Al,Ga)InP + window layer (e) Shaped TS metal InGaN-GaN-Al 2 O 3 p-spreader Al 2 O 3 (a) Conventional Chip - CC n-wb pad (c) Vertical Thin Film - VTF n-wb pad reflective metal bond n-type p-type light extraction features n-type p-type Al 2 O 3 (b) Flip Chip - FC (d) Thin Film Flip Chip - TFFC (c) Thick AS + DBR host substrate (f) Thick RS n contact reflective p contact n contact reflective p contact Light Light Extraction extraction Efficiency, efficiency, Cext C ext (%) Thin AS Thick AS + DBR Thick AS TS Shaped TS CC CC (PS) Thick RS Improved TS FC (Al) VTF FC (Ag) TFFC CC(PS/ITO) low power CC (PS/ITO) high power Year Dramatic improvement last 15 years Light extraction efficiencies reach ~80% (InGaN) and 60%+ (AlGaInP) 9

10 State-of-Art Power LED Chip Design Flip Chip LED (FC) Excellent heat extraction No wire bonds High extraction efficiency Thin Film Flip Chip LEDs (TFFC) Highest extraction efficiency Lambertian radiation pattern QW(s) Ag p-contact hν Sapphire n-gan p-gan Heat Heat Submount Flip Chip LED Vertical chip LED array with lens TFFC LED Lambertian Sapphire removed hν FC, TFFC LED array with lens TFFC LED Lambertian radiation pattern of TFFC LED QW(s) Ag p-contact Heat p-gan Submount n-gan Heat Thin Film Flip Chip LED 10

11 Key Challenge: PC-White CCT Variation Imperceptible color variation for human eye: 6500 K: ±200 K 3000 K: ±50 K Manufacturing challenge Blue wavelength range Control of phosphor deposition process Phosphor layer Phosphor particles LED Phosphor coating v' inf Phosphor 8000 layer thickness Yellow Phosphor Yellow Phosphor u' 3050 Cool-white color bins Blue wavelength range Warm-white color bins K +/-200K 3000K +/-50K LED chip LED chip Conventional LED: Slurry deposited phosphor particles Luxeon LEDs: Conformal phosphor coating Large variation in CCT 10 20x reduction in CCT distribution desired 11

12 Improvement: Solid-State Phosphor Element Lumiramic phosphor technology Sintered YAG:Ce ceramic Matches TFFC LED chips Optically homogeneous solid-state material White LEDs with Lumiramic phosphor technology Precision in phosphor absorption via plate thickness control 4x Reduction in number of color bins High luminance and excellent color stability QW(s) Ag p-contact Lumiramic YAG:Ce Plate (not to scale) p-gan n-gan Submount TFFC LED with Lumiramic Lumiramic platelets v' Planckian Locus 460 nm Pump WL distribution 440 nm YAG:Ce CCT ~5000 K Increasing absorption CIE Chromaticity Diagram u' 12

13 State-of-Art LED Packages - Power Handling Power handling capability LUXEON K2 >5 W Luxeon Rebel ~3 W Future >10 W Lumen maintenance Strong function of Junction temperature (T J ) Drive Current (I f ) Typical: 50,000 hour (B50, L70) Lifetime Power handling per LED (W) mm lamp Superflux LUXEON K2 LUXEON I Year Power Handling per LED Future LUXEON Rebel Power handling increased >100 x in last decade LUXEON K2 13

14 State-of-Art LED Packages LUXEON K2 Highest flux Highest drive current (I f 1.5 A) Highest operating temperature (T J 185 C) Lowest cost of light LUXEON Rebel Highest flux-density (footprint: 3 x 4.5 mm 2 ) High operating temperature (T J 150 C) High drive current (I f 1 A) Highest flux/$ power LED r = 2.13 mm d ~15 mm Example: Color mixing LUXEON K2 LUXEON Rebel Small size reduces focal length smaller optical systems smoother mixing in small spaces First power LED pixel solution 14

15 Ultra Small, Low Cost Power Packaging LUXEON Rebel Platform Performance: Size: 3x4.5mm vs. 7.2 x 7.2mm Light output, efficiency, reliability leader in 350mA 1A class Packing density: Up to 6x other power LEDs Lowest cost/improved Lumens/$ Outperforms Chip-on-Board (performance, reliability) Winner: Technical Excellence Award 15

16 Introducing LUXEON K2 with TFFC Utilizes the latest TFFC die for dramatically improved light output Light output bins start at min 160 lumens in white Lowest Thermal Resistance: 5.5 C/W Highest Maximum Junction Temperatures: 185 C for direct colors, 150 C for white Tested and binned exclusively at 1000mA Available first in cool-white to be followed by warm-white, neutral-white, blue and green Lead-free reflow solder JEDEC 020c compatible 16

17 LUXEON Automotive Forward Lighting Source Key Performance Attributes: Automotive Reliability High Power Density (> 4 W/mm2) High Temperature Operation World class lumen output: Today: 750 1A per 1x4 Future: >> A High luminance Today: 45 1A per 1x4 Future: >90MNits 2008 Audi R8 AFL LED elements LAFLS: ~ 45 MNits Prototype package Prototype AFL LED Package Halogen: ~ 20 MNits 17

18 Performance: Evolution of LED source brightness Luminance (cd/m 2 ) Luminance (cd/m 2 ) 1.E+09 1.E+08 1.E+07 1.E+06 1.E+05 1.E+04 Halogen Fluorescent UHP HID unfiltered* filtered LEDs TFFC LED, 1 A Projection Illumination general spot Automotive Indicator Displays 1.E *collected flux of 4500 lm within 15 mm2-sr, an étendue typical for micro-display projection (G. Derra, J. Phys. D: Appl. Phys. Vol. 38, pp , 2005) Focus on power LEDs has accelerated luminance performance. LED brightness on target to match that of the UHP bulb. 18

19 Heat Management: Easier in the Future Heat Generation (W) Lumen Single Emitter (White) Active Cooling 1000 lm Single Emitter (White) Passive Cooling Luminous Efficiency (lm/w) If PCE = 50 %, LE = 150 lm/w LEDs pass all heat back to heat-sink and fixture Today s efficiency: Thermal management remains an issue and adds cost Future efficiency: Heat management should be straightforward Circuitry for driving LED is a large cost factor for replacement lamps. As LED efficiency goes up circuit cost will go down, but will likely remain a key issue 19

20 LUXEON Applications Around the World Mega Bridge, Bangkok, Thailand Philips Bosphorus Bridge, Istanbul, Turkey Philips Technopolis, Athens, Greece Philips 20

21 High-power LED Applications: RGB White Illumination LCD Backlighting Projection Pocket Projectors Flux: lm Power: W Weight: lb Battery life: 2.5 h Toshiba TDP-FF1A LUXEON I and LUXEON III Replicates day-light without harmful ultraviolet or infra-red radiation Exact color rendition Mona Lisa Lighting by Fraen Corporation Mitsubishi PK-10 SONY Qualia 005 Triluminos TM LED backlight for LCD panel Ultra-high color gamut (105 % NTSC) LEDs eliminate motion artifact Mercury free Long life Samsung SP-P300M 21

22 High-power LED Applications: PC White Portable lighting Mobile phone camera flash Illumination Automotive forward lighting Casino Breda, Netherlands by Bocom LUXEON V 2 80 variable lumens 1-40 variable hours Non imaging optics Functional flash (<~3m) LUXEON Flash LUXEON Module Surefire DEF 1 Daytime Running Light (DRL) Multiple LEDs per DRL 100 C ambient temperature S8 S6 22

23 Why are LEDs Not Yet Widely Used for General Illumination? Cost has been too high Efficiency has been too low White color needs to be warmer and better controlled Engineering challenges: thermal, optical, electrical Other Issues: Standards, complimentary infrastructure, stable supply, etc. 23

24 Key Challenge: Cost/lumen The conventional technologies are much lower in cost $/1000 lm Incandescents: Fluorescents: CFLs: White LEDs: ~0.4 ~0.6 ~2.0 (and going lower) ~10.0 (best case-without driver!) Need > 10x reduction! How do LEDs get closer? Gain Factor Efficiency improvement (75 lm/w to 150 lm/w) 2x Higher drive currents (700 ma to 2A) 3x LEDs are more competitive when total cost of ownership and environmental factors (no mercury) are considered Lower chip and packaging costs 2x Total 12x 24

25 Outlook: Goals for Phosphor White for Illumination Single-emitter Flux ( Power LED) 1000 lm target same as 60 W light bulb today s LEDs: lm ea. Max. White Lumens Early LUXEON I 5 mm lamp Cost of Ownership (COO) Analysis 1000 lm source LUXEON K2 LUXEON III Year Input Power Source cost Energy cost/yr COO (1 yr) COO (5yrs) 1 X 60 W incandescent 60 W $ <1 $ 48 $ 48 $ x 20 W Compact Fluor. 20 W ~ $ 2 $ 18 $ 20 $ x 1-W TFFC emitters 14 W $ 20 $ 13 $ 33 $ 85 1 x 160 lm/w LED ~ 6 W ~ $ 1 $ 5 ~ $ 6 ~ $ 26 at $0.10 per kwh Target: ~160 lm/w, 1000-lm LED 25

26 Outlook: How achievable is 160 lm/w, 1000-lm LED? For single 1000-lm emitter, 2 A drive current needed Light Extraction Eff. Internal Quantum Eff. Forward Voltage Luminous Efficacy* C ext (%) IQE (%) EQE (%) V f (V) PCE (%) 2000 ma : 1x1 mm 2 LE (lm/w) Today ~90 ~40 ~36 ~4.2 ~25 ~61 PC White Future ~90 ~90 ~80 ~2.9 ~75 ~160 *assumes 250 lm/wopt phosphor conversion for cool white CCT ~6000 High-current-density (~ 250 A/cm 2 ) efficiency is critical Blue internal quantum efficiency (IQE) must increase by > 2x Must reduce forward voltage (ongoing programs) Warm white would be lower by (10-30%) 26

27 Summary Power LEDs are improving rapidly. Commercial performance in the 100 lm/w range is beginning, and ~150 lm/w should happen within five years Key issues for conversion to LEDs include: More lumens, lower cost, complementary infrastructure, standards, and consistent high volume supply Performance improvement for green devices is a key issue for RGB tuneable white It is clear that LEDs will dominate general illumination. The only question is timing Full conversion at 150 lm/w will reduce electricity used for lighting by ~50% and save over 100 nuclear reactors worldwide 27