Innovations in LEDs

George Craford Philips Solid Sate Lighting Fellow

2015 DOE Solid State Lighting

R&D Workshop

January 27, 2015

2 January 27, 2015

Outline

• PAST - What Happened and What Can We Learn

• PRESENT – Where Are We and What are the Emerging Trends

• FUTURE – How Do We Get to 250l/w and What is Next in SSL Innovation?

Congratulations!!

3 January 27, 2015

200 Years of Lighting Technology Efficiency

0.0001

0.001

0.01

0.1

1

1850 1900 1950 2000 2050

Eff

icie

nc

y

Year

1850 1900 1950 2000 2050

Year

0.01

0.1

1

10

100

Effi

cie

ncy

(%

)

Fluorescence

Incandescence

Fire

Color-Filtered Incandescence

Oil

Gas Kerosene

Gas Mantle

Carbon Filament

Tungsten Filament

SiC

InGaN

GaAsP

GaP:Zn,O

GaAsP:N

AlGaAs

AlInGaP

Solid-State Lighting

Electric bulb from Neloux,

courtesy of KMJ.

http://commons.wikimedia.org/w

iki/File:Gluehlampe_01_KMJ.jpg

Fluorescent Tube

http://en.wikipedia.org/wiki/File:Leuchtstofflampen-

chtaube050409.jpg

Candle burning.

http://en.wikipedia.org/wik

i/File:Candleburning.jpg

Bridgelux Helieon Solid-State Lamp.

http://www.bridgelux.com/products/hel

ieon.html

- Courtesy of J. Tsao and J.A. Simmons, Sandia National Laboratories

4 January 27, 2015

Evolution of Visible LEDs Selected events

• 1907 Electroluminescence observed in Carborundum (SiC) – H.J. Round

• 1923-1930 Comprehensive study of SiC electroluminescence and discussion of application for communications - O.V. Losev

• 1947 Discovery of transistor – Bardeen and Brattain

• 1951 Explanation of SiC electroluminescence as carrier injection across a p/n junction – K. Lechovec, et al.

• 1955 Visible electroluminescence in GaP – G.A. Wolff, et al.

• 1962 Demonstration of coherent visible light emission from direct bandgap GaAsP alloy semiconductors – N. Holonyak and S.F. Bevacgua

• 1962-Present Continuing development and optimization of various direct bandgap ternary (GaAsP, AlGaAs) and quarternary (AlInGaP, AlInGaN) material systems for high performance LEDs – RCA Monsanto, Hewlett Packard, Stanley, Osram, Toshiba, Toyoda Gosei, Nichia, Cree and others

5 January 27, 2015

Craford Presenting Holonyak with LED Headlight at Symposium at the University of Illinois celebrating the 50th Anniversary of the LED

October 2012

6 January 27, 2015

Evolution of LED Performance

0.1

1

10

100

1000

1960 1970 1980 1990 2000 2010

200

Edison’s First Light Bulb

InGaN

169

lm/W

Latest Value White

First > 100 lm/W Red

GaAsP:N Red-Orange-Yellow

AlGaAs/AlGaAs Red

AlGaAs/GaAs Red

GaP:N Green

GaP:Zn,O Red

Ga0.6As0.4P Red

~10X/decade

Blue

Green

White

Fluorescent Lamp

Yellow Filtered Incandescent Lamp

Red Filtered Incandescent Lamp

Unfiltered Incandescent Lamp AlInGaP/GaAs

Red-Orange-Yellow

Lum

ino

us

Effi

cacy

(lm

/W)

SiC

Holonyak’s First

Commercial LED

GaAsP Red

Transparent Substrate AlInGaP/GaP Red-Orange-Yellow

Shaped AlInGaP/GaP Red-Orange-Yellow

7 January 27, 2015

lm/W improvement is still going…

Source: DOE 2014 SSL Roadmap

lm/W improvement

8 January 27, 2015

Historical Perspective on Department of Energy Performance Projections

0

50

100

150

200

250

2000 2005 2010 2015 2020

Time

Lum

ino

us

Effi

cien

cy

2002 MYPP (White) 2008

Cool White

Warm White 2008 MYPP

2014 MYPP

2014 MYPP Goal

Cool White

Warm White

9 January 27, 2015

Price-Efficacy Tradeoff for LED Packages

2015 2020 Goal CW (Lm/W) 192 231 250 ($/klm) 2 0.7 0.5 WW (Lm/W) 169 225 250 ($/klm) 2.3 0.7 0.5

X

2002 MYPP 2012 <$5/Klm @150

2002 MYPP 2020 <$2/Klm@200 l/w

X

10 January 27, 2015

LED Building Blocks

Epitaxy and

Materials

Device (chip)

design

Phosphors

Package

11 January 27, 2015

LED Building Blocks and Their Impact on Efficacy

The cells with “X” indicates a component of luminous efficiency affected by a particular LED building block.

LED Building Blocks IQE ELE EXE CE

PE LE QD QE epi (substrate, emission wavelength, heterostructure)

X X X X X

die (type, p-, n- contacts, interconnects)

X X X X

package (type, encapsulants, interconnects)

X X X X X

converter (phosphors, encapsulants)

X X X X X

12 January 27, 2015

Efficacy breakdown for a typical warm white phosphor converted LED J=350mA/mm2 and Tj=85oC

0% 20% 40% 60% 80% 100%

QE of Downconversion

Quantum Deficit

Package Efficiency

Extraction Efficiency

Electrical efficeincy

Inernal Quantum Efficiency

0 100 200 300 400

Efficacy Lm/W

Lumen Equivalent

values listed for 3000K 80CRI phosphor converted LEDs at J=30mA/mm2 and Tj=85C

Practical Limit 2015

13 January 27, 2015

Droop Impact for Mid-Power and High-Power LEDs

50

55

60

65

70

75

80

10 100 1000

WP

E (%

)

Current Density (mA/mm2)

• Droop results in reducing efficacy above ~35mA/mm2, so impacts both MP and HP, with greater impact at increasing drive currents

• For lm/$, LEDs are driven harder and harder once the system level efficacy has been reached

• Droop impacts MP • Droop impacts HP

Conclusion: Droop is important for both MP and HP LEDs.

Peak WPE (~35mA)

MP Operating Range (65-240mA/mm2)

HP Operating Range (~175-1000mA/mm2)

14 January 27, 2015

Direct Emitting Green is Still Needed

0%

10%

20%

30%

40%

50%

60%

70%

350 450 550 650

Peak Wavelength (nm)

Ex

tern

al Q

ua

ntu

m E

ffic

ien

cy

In x Ga

1 - x N In

x Ga

1 - x N In

x Ga

1 - x N In

x Ga

1 - x N (Al

x Ga

1 - x )

0.52 In

0.48 P (Al

x Ga

1 - x )

0.52 In

0.48 P (Al

x Ga

1 - x )

0.52 In

0.48 P (Al

x Ga

1 - x )

0.52 In

0.48 P

T j

= 25

C T j

= 25

C

Exte

rnal

quan

tum

eff

icie

ncy,

(4)

V( l )

350 mA Exte

rnal

Qu

antu

m E

ffic

ien

cy

15 January 27, 2015

n-GaN

Ceramic Submount

p-GaN n-GaN

Ceramic Submount

p-GaN

Sapphire

n-GaN p-GaN

Sapphire

Flip Chip Thin Film Flip Chip (TFFC) Chip Scale Package (CSP)

Conventional chip Lateral die

n-GaN

p-GaN

Sapphire

Transparent conductive

oxide contact

Vertical Thin Film (VTF) Embedded-Contact VTF (EC-VTF)

n-GaN

p-GaN Anode

contact

Cathode

contact

Cathode

contact

Anode

contact

Evolution of GaN Blue Die

n-GaN

p-GaN

Sapphire

Semi-transparent

Ni/Au contact

16 January 27, 2015

Narrow Red Phosphor to boost CE for High CRI WW LEDs

350 450 550 650 750S

pectr

al P

ow

er D

istr

ibutio

n(n

ora

maliz

ed

)Wavelength (nm)

CCT ~ 2700KPhotopic Response

30nm FWHM red, 90 Ra, LE ~ 370 lm/Wopt

today ~ 80 Ra, LE ~ 315 lm/Wopt

Lumen loss of

current Phosphors

• Current red phosphors have broad emission

(90-100nm)

• Substantial amount light emitted in far-red reducing lumen output with limited benefit for color rendering

• Reduced width of red phosphor emission could increase efficacy of warm white LEDs by 20%

17 January 27, 2015

Different Approaches for White LEDs

Phosphor-converted LEDs Blue pump LED + phosphor

Direct-emitting LEDs

3 or 4 colors

Hybrid LEDs Combining phosphor-converted

and direct-emitting LEDs

350 450 550 650 750

Wavelength (nm)

Photopicresponse3000 KPlanckianBlue

350 450 550 650 750

Wavelength (nm)

Photopicresponse

350 450 550 650 750

Wavelength (nm)

Photopic response

3000 K Planckian

Off-white

Direct red

18 January 27, 2015

Key Technical Challenges

PHOSPHOR-CONVERTED HYBRID

DIRECT EMITTING

Improved (Narrow) Red Phosphor X

Improved Green/Yellow Phosphor X X

Fix Droop X X X

Improved Blue LED X X X

Improved Red LED X X

Improved Green LED X

19 January 27, 2015

ROI Energy Saving vs. Effort to Improve Lm/W is Getting Less Attractive

Source: DOE 2014 SSL Roadmap

Energy saving effect Lm/W improvement

Ene

rgy

Co

st (

Yen

/lm

)

20 January 27, 2015

1960 1970 1980 1990 2000 2010 2020 Year

0.01

0.1

1

10

100

Pow

er h

and

ling

per

LED

(W

)

3/5mm lamp

Super Flux

LUXEON I

LUXEON Rebel

SnapLED

LUXEON III LUXEON V

LUXEON K2

LUXEON Flash

LUXEON Rebel ES

LUXEON Altilon

LUXEON S

LUXEON M

LUXEON CoB LED Packaging Evolution

21 January 27, 2015

LED Packaging: Reducing Costs & Improving Customer Flexibility

Silicone Lens

L0 Assembly (LED+submount)

CTE Buffer Layer

Leadframe/ Kicked-up WB Leads

Slug Carrier Frame Note: Direct Assembly to Slug

Cu Slug

5mm Indicator Package Example LUXEON High-Power Package Example

Luxeon Rebel LUXEON Flip-Chip High Performance Chip-Scale Package

Substrate

InGaN EPI

Base Metal AuSn Solder Bump

Redistribution Layer

PSS Sapphire

LUXEON Die on Ceramic Package Chip in a Frame Package

22 January 27, 2015

Chip Scale Packages: Flexible & Reliable

Flip chip + Remote Phosphor Film

vs.

• No wire bonding • Failure is short mode

CoB by conventional structure die

LUXEON FlipChip

Flip Chip Architecture High lumen compact COB solutions

23 January 27, 2015

Applications by Luminance and Lumen output

1.E+05

1.E+06

1.E+07

1.E+08

1.E+09

10 100 1000 10000

Lum

inan

ce (c

d/m

2)

lumen output

High-power arrays

Illumination

High brightness emitters

Imaging, Automotive Forward Lighting

Low power emitters

Indicators, small display

Mid-power single

emitters

Illumination

High-power single

emitters

Illumination

Mid-power arrays

Illumination

24 January 27, 2015

Technology for Crisp Whites …by LEDs with application specific spectra

25 January 27, 2015

What’s Next in Lighting After the “Replacement Transient”??

What would lighting look like if we had gone straight from fire to LEDs??

• How widely will the “digital lighting revolution” extend with color tuning, motion sensing, communication, etc?

• Will ceiling lighting move from troffers and spots to large area “skylight” ceilings made up of programmable color changeable LED panels?

• What lighting will be developed that will help us to be healthier and more productive?

• Will the solar / LED “marriage” expand from off-grid lamps and streetlights to solar powered homes?

• Will structures, clothes, furniture, body art, etc. with embedded LEDs become widely utilized?

• What completely new design concepts will emerge?

26 January 27, 2015

“2nd Wave Lighting: Smart and Feature Rich

Integrated Illumination and Displays

Human Health, Well Being and Productivity

Agriculture Communication Light-Field Mapping

Courtesy of pureVLC Ltd. Courtesy of SOA architects

Courtesy of NEONNY Technologies

Co

urt

esy

of

E.F.

Sch

ub

ert

Courtesy of Shuntaro Yamazaki,

AIST

Courtesy of Dan Picasso and the Wall Street Journal

Smart Lighting Applications

M.H. Crawford, J.J. Wierer, A.J. Fischer, G.T. Wang, D.D. Koleske, G.S. Subramania, M.E. Coltrin, J.Y. Tsao, R.F. Karlicek, Jr., “Solid-State Lighting: Toward Smart and Ultra-Efficient Materials, Devices, Lamps and Systems,” in D.L. Andrews, Ed., “Photonics Volume 3: Photonics Technology and Instrumentation” (Wiley, 2014).

Courtesy Jeff Tsao UCSB Presentation Feb 22, 2014

27 January 27, 2015

Historic per Capita Light Consumption Increased with Sinking Cost of Light

Trend to “More light” continues

• 70% of world wide population in cities by 2050

• Developing regions catching up

• New applications and functionalities enabled by digital light

• 20% of world wide power consumption for Light

1.E-06

1.E-03

1.E+00

1.E+03

1.E-06 1.E-03 1.E+00 1.E+03

Ph

i (d

ata

) P

lmh

/y

Phi (PPP model) Plmh/y

J.Y. Tsao and P. Waide, “The World’s Appetite for Light: Empirical Data and Trends Spanning Three Centuries and Six Continents,” LEUKOS 6, 259-281 (2010).

10-6 10-3 1 103

Φ (

Plm

h/y

r)

CN 1993

WRLD-NONGRID 1999

WRLD 2005

UK 1800 UK 1850

UK 1750

UK 1700

UK 1900

UK 1950

UK 2000 AU+NZ 2005

FSU 2000

OECD-EU 2005

JP+KR 2005

CN 2005

CN 2006

US 2001,2010

103

1

10-6

10-3

0.0072

β·GDP/CoL (Plmh/yr)

G$/yr $/Mlmh

Ligh

t U

sage

Decreasing Cost

28 January 27, 2015

Summary

• LED performance appears to be moving from revolutionary to evolutionary improvement

• After decades of focus primarily on lumens/watt and lumens/dollar application specific packaging has become a third innovation focus area

• Future design concepts and applications often including “smart” lighting will revolutionize lighting in ways impossible to predict

Thank you