innovations in leds - us department of...
TRANSCRIPT
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