Lighting Your Path To The Future - IMAPS · PDF fileLighting Your Path to the Future ... Lit...

Lighting Your Path to the Future

IMAPS Global Business Council November 14, 2007

M. George Craford, CTO Philips Lumileds Lighting Company

2Philips Lumileds Lighting Company, M. George Craford, IMAPS November 14, 2007

Outline

Buckingham Palace, London, England

Lit by LUXEON LEDs

• Power LED Technology Status and Trends

• Existing and Emerging Applications

• Challenges and Recent Developments for Solid State Lighting


• 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)

Outlook: LEDs vs. Conventional Light Sources

Krames et al., IEEE J. Display Technol. 3, 160 (2007)

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Light Source Description ηL(lm/W)500W High-pressure Na 150140W Metal Halide 122‘TL HE’ Tube Fluorescent 105Halogen-IR Incandescent 30Standard Incandescent 16

Best low-current

LED

halogen

metal halidehigh-pressure Na

fluorescent

Pow

er L

EDs

Hg vaporhalogen-

IR

U.S

. DO

E ro

adm

ap

(LED

s)

incandescent

Best high-power LED

Lum

inou

s Eff

icac

y (lm

/W)


White LED Performance“Cool” CCT ~ 4500 – 10,000K

• Small 5mm LEDs– Lower current density– Lower forward voltage

• Power LEDs– More lumens/package– Lower cost per lumen

Pum

p B

lue

WP

E (e

st.)

Current Density (A/cm2)

Lum

inou

s E

ffica

cy (l

m/W

)

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Power LED~2004

Power LEDLab results

Small LEDLab results

Small LED 2006

~20 mA ~350 mA

Power LED2006

Power LED2007

Small LED 2007


The Four Elements of LED TechnologyEpitaxy and

MaterialsDevice (chip)

designPackagePhosphors

Important metrics:External quantum efficiency:

EQE = IQE x EXE

Power conversion efficiency:PCE = EQE x Eph / Vf

Luminous efficacy:LE = PCE x V(λ)


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350 450 550 650

1) Philips Lumileds TFFC LEDs 2) Morita et al., Jpn. J. Appl. Phys. 43, 5945 (2004)3) Nichia, ICNS-74) Philips Lumileds TIP LEDs

InxGa1-xNInxGa1-xN (AlxGa1-x)0.52In0.48P(AlxGa1-x)0.52In0.48P

(2)

(1)

Tj = 25°CTj = 25°C

Exte

rnal

qua

ntum

eff

icie

ncy,

ηex

tEx

tern

al q

uant

um e

ffic

ienc

y, η

ext

Peak wavelength, λp (nm)Peak wavelength, λp (nm)

(4)

High-power ( 1 Watt input) visible -spectrum LEDs~>~>High-power ( 1 Watt input) visible -spectrum LEDs~>~>

(3)

V(λ)

(3)

• InGaN– Maximum external quantum efficiencies in the blue– Lower efficiency with increasing InN % (~ 2x reduction green)

• AlGaInP– Fundamental bandstructure limitations at short wavelengths

High-Power (> Watt Input) LED Performance


RGB 540

400 450 500 550 600 650 700

Wavelength (nm)

R

R-G540-B White LED for Illumination

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Green LED Efficiency (WPE)

Whi

te S

ourc

e Ef

ficie

ncy

(lm/W

)

0.20.40.75

•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

Red - 615nmBlue - 460nmGreen - 540nm

CRI – 90CCT - 3270

Blue WPE - 75%Red WPE - 75%

Red WPE - 40%

Red WPE - 20%

Red, Green, Blue Color Mixing for Warm White Illumination


Recent Development: Improved Epitaxial Materials Process Reduces “Efficiency Droop” at High Current Densities *

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Device input current (mA)

Nor

mal

ized

EQ

E (%

)

PLL high currentefficiency solutionCurrent Production

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Device current (mA)

Nor

mal

ized

rad

iant

flux

(% m

ax. W

)

PLL high currentefficiency solutionCurrent Production

• 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 1mm2 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)


Thin ASThick AS

Thick AS + DBRTS

Improved TS

Shaped TS

Thick RS

CC(PS/ITO)low power

CC (PS/ITO)high power

TFFC

CC

FC (Al)

CC (PS)FC (Ag)

VTF

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1990 1995 2000 2005 2010Year

Lig

ht E

xtra

ctio

n E

ffici

ency

, Cex

t (%

)Li

ght e

xtra

ctio

n ef

ficie

ncy,

Cex

t(%)

Year

(f) Thick RS

(a) Thin AS

(e) Shaped TS

(b) Thick AS (c) Thick AS + DBR

(d) Thick TS

(Al,Ga)InPwb pad

host substrate

GaAs GaAs GaAs

(Al,Ga)InP + window layer

DBR

n-GaP substrate

p-GaPn-GaP

substrate

p-GaPmetal

(Al,Ga)InP-GaAs or (Al,Ga)InP-GaP

InGaN-GaN-Al2O3

LED Chip Design

• Dramatic improvement last 15 years• Light extraction efficiencies reach

~80% (InGaN) and 60%+ (AlGaInP)

(a) Conventional Chip - CC (b) Flip Chip - FC

(c) Vertical Thin Film - VTF (d) Thin Film Flip Chip - TFFC

Al2O3

n-type

p-wb pad

p-type

p-spreader

n-wb pad

Al2O3

p-typen-type n contact

n-wb pad

n-typep-type

reflective metal bond

host substrate

n-typep-type

n contact

reflective p contact

reflective p contact

light extraction features


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 Flip Chip LED

QW(s)p-GaN

n-GaN

Sapphire

Submount

hν

Agp-contact

Thin Film Flip Chip LED

QW(s)p-GaN

n-GaN

Submount

hν

Agp-contact

LambertianTFFC LED

TFFC LED

FC, TFFCLED array with lens

Vertical chipLED array with lens

Lambertian radiation patternof TFFC LED

Heat Heat

Heat Heat

Sapphireremoved


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in f

Y e l lo w P h o s p h o r

6 5 0 0 K + /-2 0 0 K3 0 0 0 K + /-5 0 K

Key Challenge: PC-White CCT Variation

• Imperceptible color variationfor human eye:

– 6500 K: ±200 K– 3000 K: ±50 K

• Manufacturing challenge– Blue wavelength range– Control of phosphor

deposition process

Phosphor layer LED

LED chip LED chip

Phosphor coating

Luxeon LEDs:

Conformal phosphorcoating

Phosphorparticles

10…20x reduction inCCT distribution desired

Conventional LED:

“Slurry deposited”phosphor particles

Blue wavelength range

Phosphorlayer

thickness

Yellow Phosphor

Warm-whitecolor bins

Cool-whitecolor bins

Large variation in CCT


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u'v'

Pump WLdistribution

YAG:Ce

PlanckianLocus

Increasingabsorption

CIE Chromaticity

Diagram

460 nm

440 nm

CCT ~5000 K

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)p-GaN

n-GaN

Submount

Agp-contact

Lumiramic™ YAG:Ce Plate(not to scale)

TFFC LED with Lumiramic™

Lumiramic platelets


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YearP

ower

han

dlin

g pe

r LE

D (

W)

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 (TJ)• Drive Current (If)

– Typical: 50,000 hour

Power handling increased>100 x in last decade

(B50, L70) Lifetime

Power Handling per LED

“5 mm”lamp

“Superflux”LUXEON I

LUXEON K2

LUXEONRebel

Future

LUXEON K2


State-of-Art LED Packages

• LUXEON K2– Highest flux– Highest drive current (If ≤1.5 A)– Highest operating temperature (TJ ≤185°C)– Lowest cost of light

• LUXEON Rebel– Highest flux-density (footprint: 3 x 4.5 mm2)– High operating temperature (TJ ≤150°C)– High drive current (If ≤1 A)– Highest flux/$ power LED

LUXEON K2

d ~1

5 m

md

~15

mmr = 2.13 mmr = 2.13 mm

Example: Color mixing

• Small size reducesfocal length

– smaller optical systems– smoother mixing in small spaces

• First power LED “pixel solution”

LUXEON Rebel


Ultra Small, Low Cost Power PackagingLUXEON 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


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


LUXEON Automotive Forward Lighting SourceKey Performance Attributes:

– Automotive Reliability– High Power Density (> 4 W/mm2)– High Temperature Operation– World class lumen output:

• Today: 750 lumens @ 1A per 1x4• Future: >>1500 lm @ 2.3 A

– High luminance• Today: 45 MNits @ 1A per 1x4• Future: >90MNits

2008 Audi R8

Halogen: ~ 20 MNits

LAFLS: ~ 45 MNits

Prototype AFL LED Package

AFL LED elements

Prototype package


Performance: Evolution of LED source brightness

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

1.E+08

1.E+09

1960 1970 1980 1990 2000 2010 2020

Lum

inan

ce (c

d/m2 )

Fluorescent

Halogen HID

unfiltered*

LEDs

Indi

cato

r D

ispl

ays

Aut

o-m

otiv

e

Proj

ectio

nIl

lum

inat

ion

gene

ral

sp

otPr

ojec

tion

Lum

inan

ce (c

d/m

2 )

TFFCLED, 1 A

• Focus on power LEDs has accelerated luminance performance.• LED brightness on target to match that of the UHP bulb.

filtered

UHP

*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. 1995-3110, 2005)


1000-Lumen Single Emitter (White)

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Luminous Efficiency (lm/W)

Heat

Gen

erat

ion

(W)

Active Cooling

Passive Cooling

1000 lm Single Emitter(White)


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erat

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Active Cooling

Passive Cooling



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Heat

Gen

erat

ion

(W)

Active Cooling

Passive Cooling


Heat Management: Easier in the Future

• 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

If PCE = 50 %,LE = 150 lm/W


LUXEON Applications Around the World

Mega Bridge, Bangkok, ThailandPhilips

Bosphorus Bridge, Istanbul, TurkeyPhilips

Technopolis, Athens, GreecePhilips


High-power LED Applications: RGB White

• Illumination• LCD Backlighting• Projection

• LUXEON I and LUXEON III• Replicates day-light

without harmful ultra-violet or infra-red radiation

• Exact color rendition

SONY Qualia 005

• TriluminosTM LED backlightfor LCD panel

• Ultra-high color gamut(105 % NTSC)

• LEDs eliminate motion artifact• Mercury free• Long life

Pocket Projectors• Flux: 12 – 100 lm• Power: 10 – 25 W• Weight: 1 – 1.5 lb• Battery life: 2.5 hToshiba TDP-FF1A

Mitsubishi PK-10

Samsung SP-P300M

Mona Lisa Lighting by Fraen Corporation


High-power LED Applications: PC White

• Portable lighting• Mobile phone camera flash• Illumination• Automotive forward lighting

S6

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

S6S8

Daytime Running Light (DRL)• Multiple LEDs per DRL• 100°C ambient temperature


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.


Key Challenge: Cost/lumenThe conventional technologies are much lower in cost

~10.0 (best case-without driver!)White LEDs:

~2.0 (and going lower)CFLs:

~0.6Fluorescents:

~0.4Incandescents:

$/1000 lm

Need > 10xreduction!

How do LEDs get closer?

Total 12x

2xLower chip and packaging costs

3xHigher drive currents (700 mA to 2A)2xEfficiency improvement (75 lm/W to 150 lm/W)

Gain Factor LEDs are more competitive when total cost of ownership and

environmental factors (no mercury) are considered


1

10

100

1000

1995 2000 2005 2010

Year

Max

. Whi

te L

umen

s

Outlook: Goals for Phosphor White for Illumination

• Single-emitter Flux (“Power” LED)

1000 lm target– same as 60 W light bulb– today’s LEDs: 100-200lm ea.

• Cost of Ownership (COO) Analysis – 1000 lm source

$ 240$ 48$ 48$ <160 W1 X 60 W incandescent

$ 90$ 20$ 18~ $ 220 W1 x 20 W Compact Fluor.

~ $ 6

$ 33

COO(1 yr)

~ 6 W

14 W

InputPower

~ $ 26$ 5~ $ 11 x 160 lm/W LED

$ 85 $ 13$ 2010 x 1-W TFFC emitters

COO (5yrs)

Energy cost/yr

Source cost

Target: ~160 lm/W, 1000-lm LED

5 mm lamp

Early LUXEON I LUXEON III

LUXEON K2

at $0.10 per kWh


Outlook: How achievable is 160 lm/W, 1000-lm LED?

• High-current-density (~ 250 A/cm2) 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%)

Light Extraction Eff.Internal Quantum Eff.

Forward Voltage

Luminous Efficacy*

~80~36EQE (%)

~2.9~4.2Vf (V)

~75~25PCE (%)

PC White

~160~61LE (lm/W)

~90~40IQE (%)

~90~90Cext (%)

FutureToday

2000 mA : 1x1 mm2For single 1000-lm emitter, 2 A drive current needed

*assumes 250 lm/Wopt phosphor conversion for cool white CCT ~6000


• 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 RGBtuneable 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

Summary

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