session: led phosphorssession: led phosphors...session: led phosphorssession: led phosphors ... •...
TRANSCRIPT
Session: LED PhosphorsSession: LED Phosphors
Luminescent Materials for LEDs with Ultimate Efficiency and Color Qualityy Q y
By
Prof. Dr. Thomas Jüstel
Department Head Chemical Engineering
Münster University of Applied Sciences
Almost 20% of produced electrical energy is consumed by lighting (source: NASA)
in( )
East Berlin1989 “The wind of change”
21st Development of daylight white LEDs with century luminous efficiency > 120 lm/W replacement of
East Berlin Na lamps
West Berlincentury luminous efficiency > 120 lm/W replacement of Na and Hg low and high pressure discharge lamps
2014 “The light of change”
West Berlin Hg lamps
Outline
1. Advances in LED Technology
2. White Light Generation
3. Luminescent Materials (Phosphors)
4. Phosphor Converted LEDs (pcLEDs)
5. Towards Ultimate Efficiency and CRI
6. Conclusions and Outlook
1. Advances in LED Technology
1970(Ga,As)P< 0 1 W
2014(Al,In,Ga)P, (In,Ga)N, (Al,Ga)N0 6 5 W< 0.1 W
< 1.0 lm< 10 lm/W< 120 °C
0.6 - 5 W> 100 lmup to 303 lm/W (CREE)120 200 °C< 120 C
< 100 W/cm2
> 120 K/WYellow red NIR
120 – 200 C100 – 200 W/cm2
2 – 12 K/WAll colours and UV!Yellow, red, NIR All colours and UV!
1. Advances in LED Technology(Al,In,Ga)P 580 nm – 700 nm Yellow Orange Red
Yellow Orange Red
(In,Ga)N0,30
0,35
sity
[a.u
.]
( , ) 370 – 530 nm UV-A Blue Green
0,15
0,20
0,25
ion
inte
ns
(Al,Ga)N 210 370 nm
0,05
0,10
,
Emis
s 210 – 370 nm UV-C UV-A 400 450 500 550 600 650 700 750
0,00
Wavelength [nm]
• All spectral colours by LEDs without colour filter accessible!• EL of semiconductors results in emission bands with small FWHM < 30 nm• But white light cannot be efficiently produced by a single LED type so far• But white light cannot be efficiently produced by a single LED type so far....
1. Advances in LED TechnologyTechnical Status 2014
Lumen output: > 200 lm/W (cool white)> 100 lm/W (warm white)
CRI: 70 – 95Liftime: > 30000 hDesign: Very flexibleDesign: Very flexible
Presently: Retrofits für fluorescent tubes and light bulbs
Advantages of LED over Incandescent lamps Fluorescent lamps (CFL +TL)Higher lifetime Simpler driving and dimmingg p g gHigher effiziency Higher colour renderingBetter robustness Better robustnessNo IR radiation No UV radiationNo IR radiation No UV radiation
2. White Light GenerationGeneral concepts
1 Gl i lid i ibl li h IR1. Glowing solids visible light + IR2. Gas discharges VUV + UV-C/B/A + visible light3. Semiconductors UV-A or visible light or IR-A
White Red Green Blue (V)UV
g
Y or YR or RGphosphor
CO or RGB phosphor
blend
colour filter
White light byluminescence
White light byadditive colour mixing
Coloured lightby absorption luminescenceadditive colour mixingby absorption
2. White Light GenerationRed + Green + Blue LEDs
Blue LED + yellow phosphor
Blue LED + RG phosphor blend
UV LED + RGB phosphor blend
2. White Light GenerationMultichip LEDs• Narrow band emitter
= 30 nm typical
5 LED4 LED
99.5999895– ½ = 30 nm typical
– 2 - 5 monochromatic LEDs• Theoretical limit de
ring
3 LED2 LED
95908070– 430 lm/W with
– CCT = 4870 K– CRI = 3 (!) C
olou
r re
nd
Source: Zukauskas, A., et. al.., "Optimization of white polychromatic semiconductor lamps", Applied Physics Letters 80 (2002) 234-6
7060504030CRI 3 (!)
• Possible values– 360 lm/W for CRI 90, n = 3 - 4
320 l /W f CRI 99C
y ( )20
105– 320 lm/W for CRI 99, n = 5
• Problems– Thermal quenching of (Al,In,Ga)P
300 350 400 450Lumen output [lm/Welectric]
50
q g ( )– LED Efficiency
• Red / Blue high• Green low “The green gap”• Green low The green gap
2. White Light Generation
440 - 490 nm 440 - 490 nm 440 - 490nmLED ChipLED Chip
LuminescentScreen
LuminescentScreen
300 350 lm/W 250 300 lm/W 280 330 lm/W300 – 350 lm/Wopt.
CRI = 70 – 85
250 – 300 lm/Wopt.
CRI = 85 – 95
280 – 330 lm/Wopt.
CRI = 80 – 85
low CRI at low Tc high CRI at low Tcbut decreases with Tc
CRI ~ independent of Tc
single phosphor screen phosphor blend phosphor blend
2. White Light Generation
Blue band emitter + green + red converter
88
90
100
102
m/W
]
84
86
CR96
98
effic
acy
[lm
80
82
RI
92
94
Lum
inou
s e
440 450 460 470 480 490
78
440 450 460 470 480 49090
L
Wavelength [nm]Wavelength [nm]
Conclusion: Blue LEDs emitting in the range 460 – 470 nm yield best compromise between CRI and luminous efficacyyield best compromise between CRI and luminous efficacy
2. White Light Generation
Lumen output of a light source Emission of lines or narrow bands in the blue and or red desired….
InGaN LED / Eu2+ Eu2+/ Eu3+/Mn4+
• Strongly dependent on emission spectrum
• Optimal for pure 555 nm radiation ]
InGaN LED / Eu Eu / Eu /Mn
• Optimal for pure 555 nm radiation– V() = 683 lm/W ( = 100%)
L i fl
[ lm
/W
• Luminous flux– 1000 lm for 555 nm
requires solely 1.5 W radiationli ht“
outp
ut
– „green light“
• Blue and red radiation Lum
en
– V() < 70 lm/W (<10%)– reduces lumen equivalent– is required for generating white light with high CRI
[ nm ]
3. Luminescent Materials (Phosphors)DefinitionAn (inorganic) luminescent material (phosphor) is a material which
t b b d i t l t ti di ti b d
Emission
converts absorbed energy into electromagnetic radiation beyond thermal equilibrium
ExcitationHeatHeat
Layer of Y3Al5O12:Ceµ-particles
Heat
SET
DA
A AET
ETET
Emission Average particle size ~ 1 – 10 µm
HeatHeat
size 1 10 µm
3. Luminescent Materials (Phosphors)Type of converter materials1. Inorganic phosphors
Microscale powdersMicroscale powdersSrYSi4N7:Ce(Ba,Sr)2SiO4:Eu(Ca,Sr,Ba)Si2N2O2:EuSrYSi4N7:EuSrYSi4N7:Eu(Y,Gd,Tb,Lu)AG:CeCaAlSiN3:Ce(Ca,Sr)2SiO4:Eu(Ca,Sr)S:Eu(Ca,Sr)S:Eu(Ca,Sr,Ba)2Si5N8:Eu(Ca,Sr)AlSiN3:Eu
Nanoscale powders(Y,Gd,Tb,Lu)AG:Ce
0,8
1,0
n in
tens
ity
( , , , )Quantum dots
(Zn,Cd)(S,Se), (In,Ga)(P,As), 2. Organic dyes
Polycyclic aromatic compounds0,4
0,6
mal
ised
em
issi
on
PerylenesCoumarines
Metal complexesLn3+-complexes Ln = Tm, Tb, EuR d I l
300 400 500 600 700 8000,0
0,2Nor
m
Wavelength [nm]Ru- and Ir-complexes Wavelength [nm]
3. Luminescent Materials (Phosphors)Garnets• (Y,Tb)3Al5O12:Ce• Lu3Al5O12:Ce
Selection criteria for LED phosphors• Patent situation• Price and access3 5 12
• Lu3(Ga,Al)5O12:Ce• (Lu,Y)3Sc2Al3O12:Ce• (Y,Lu)3(Al,Mg,Si)5O12:Ce
• Price and access• (Photo)Chemical stability• Colour point stability • Conversion efficiency (IQA and EQA)( , u)3( , g,S )5O12 Ce
• Ca(Y,Lu)2Al4SiO12:CeOrtho-silicates• (Ca,Sr,Ba)2SiO4:Eu
• Conversion efficiency (IQA and EQA)• Thermische quenching• Absorption strength• Saturation/Linearity(Ca,Sr,Ba)2SiO4:Eu
• (Ca,Sr,Ba)3SiO5:Eu(Oxy)Nitrides• (Sr Ca Ba)2Si5N8:Eu 2-5-8“
Saturation/Linearity• Environmental issues
(Sr,Ca,Ba)2Si5N8:Eu „2-5-8• (Sr,Ca,Ba)Si2N2O2:Eu „1-2-2-2“• (Ca,Sr)AlSiN3:Eu „1-1-1-3“• (Ca Sr Ba)SiN :Eu 1-1-2“• (Ca,Sr,Ba)SiN2:Eu „1-1-2• La3Si6N11:Ce „3-6-11“• Ba3Si6O12N2:Eu• ß SiAlONes:Eu• ,ß-SiAlONes:Eu
4. Phosphor Converted LEDs
High Power LEDs low thermal resistance ~ 2-3 K/W typical
phosphor
plasticlens
contact
InGaN-
gold wire semi-
conductor
(In,Ga)N semiconductor + phosphor (converter) Colour temperature rangeBl 420 480 Y ll l hit
cooling element (Cu)
Blue 420 – 480 nm Yellow cool whiteYellow + Red warm whiteGreen + Red cool and warm white
N UV 370 420 Bl + G + R d l d hitNear UV 370 – 420 nm Blue + Green + Red cool and warm white
4. Phosphor Converted LEDs
70(In,Ga)N LED Yellow/orange phosphorLuminescent screen
50
60
70
ensi
ty
Tc = 5270 K CRI = 82Tc = 4490 K CRI = 79Tc = 4110 K CRI = 76
0,8
1,0
rity [a
.u.]
Ce3+or Eu2+ Phosphor
20
30
40
mis
sion
inte
Tc = 3860 K CRI = 73Tc = 3540 K CRI = 70
0,2
0,4
0,6
llow
Con
vert
er
Blu
e O
LED
Em
issi
on in
tens
0
10
400 500 600 700 800
Em
Wavelength [nm]
400 450 500 550 600 650 700 750 8000,0
,
YelB
Wavelength [nm]
Wavelength [nm]Status quo cool white pcLEDs @ 2014• Phosphor (Y,Gd,Tb,Lu)3Al5O12:Ce3+
(Ca,Sr,Ba)2SiO4:Eu2+(Ca,Sr,Ba)2SiO4:Eu• Luminous efficacy LE = 303 lm/W! (WPE ~ 80%)• Colour rendering index CRI ~ 70 - 80• Corr colour temperature Tc > 5000 K• Corr. colour temperature Tc > 5000 K
4. Phosphor Converted LEDsYellow ConvertersOrtho-Silicates A2SiO4:Eu, Sr2LiSiO4:EuOxynitrides (Ca,Sr)Si2N2O2:Euy ( ) 2 2 2-SiAlONes -SiAlON:Eu
Garnets A3B2B’3O12:CeOxynitrides (Sr1-xBax)2SiO4:Ce,N 470 – 525 nm UCSBNitrides La3Si6N11:Ce 560 nm Mitsubishi
Sr2Si5N8:Ce 535 nm PhilipsC id Gd (CN ) C 540 U iTübi /Mü t
5
6Gd2(CN2)3:Ce3+
Ce3+ 4f-5d (412 nm)5
6Gd2(CN2)3:Ce3+
540 nm
Cyanamides Gd2(CN2)3:Ce 540 nm UniTübingen/Münster
3
4
5
ty [1
05 cou
nts]
3
4
5
ty [1
05 cou
nts]
250 275 300 325 350 375 400 425 450 475 5000
1
2
Sample: 174b
Inte
nsit
400 425 450 475 500 525 550 575 600 625 650 6750
1
2
Inte
nsi
Sample: 174bWavelength [nm] Sample: 174bWavelength [nm]
4. Phosphor Converted LEDsCRI Enhancement and colour temperature reduction of pcLEDs
LUXEON LEDs (Philips Lumileds)(I G )N LED Y Al O C R d h h
4
4
JAZZ 3300K
0 8
1
1.2(In,Ga)N LED Y3Al5O12:Ce Red phosphor
4
4
4
4JAZZ 3300K
BB 3300K
0.4
0.6
0.8
0
5
4
4
0
0.2
400 450 500 550 600 650 700 750 800nm
400 450 500 550 600 650 700 750nm
Wavelength [nm]Status quo warm white pcLEDs @ 2014• Red phosphor Eu2+ activated• Luminous efficacy LE 80 - 150 lm/W
black body 3600 K
fluorescent, CCT=3600 K
Wavelength [nm]
• Luminous efficacy LE 80 - 150 lm/W• Colour rendering index CRI 85 – 95• Corr. colour temperature Tc 2500 - 4000 KR. Mueller-Mach, G.O. Mueller, P.J. Schmidt, T. Jüstel,R d D fi i C ti Ph h LED Li ht E itti D i US P t t 20030006702
400 450 500 550 600 650 700 750 800nm
Red Deficiency Compensating Phosphor LED , Light Emitting Device, US Patent 20030006702
4. Phosphor Converted LEDsRed emitting LED phosphors Eu2+ doped nitrides
Ba2Si5N8:EuSr2Si5N8:EuC S
650 nm625 nm Ba2Si5N8:Eu
585 nm
Ca2Si5N8:Eu(Ca,Sr)AlSiN3:EuCaAlSiN3:Eu
0,8
1,0 Sr2Si5N8:Eu CaAlSiN3:Eu
y [a
.u.]
CaAlSiN3:Eu
0 4
0,6
sion
inte
nsity
0,2
0,4
Em
iss
500 550 600 650 700 750 8000,0
Wavelength [nm]
4. Phosphor Converted LEDs
Blue LED + Green + Red (band emitter) CRI will only slightly depend on Tc
0,8
1,0 Emission spectrum Excitation spectrum ###
y [a
.u.]y g y p c
1,0
0,2
0,4
0,6
Em
issi
on in
tens
ity
0,6
0,8
rter
vert
er
inte
nsity
[a.u
.]
200 300 400 500 600 700 8000,0
Wavelength (nm)
1,0
Emission spectrum Excitation spetrum
0,2
0,4R
ed C
onve
r
Gre
en C
onv
Blu
e LE
D
Em
issi
on
0,4
0,6
0,8
Rel
ativ
e in
tens
ity
G itt th Sili t AE SiO E
400 450 500 550 600 650 700 750 8000,0
G
Wavelength [nm]
CaSi N O - SrSi N O Solid
200 300 400 500 600 700 8000,0
0,2
Wavelength [nm]
Green emitter ortho-Silicates AE2SiO4:Eu(AE = Ca, Sr, Ba) Oxynitrides AESi2N2O2:Eu
ß-SiAlONes ß-SiAlON:EuGarnets Lu3Al5O12:Ce
CaSi2N2O2 - SrSi2N2O2 Solid solution without miscibility gap fine-tuning of green emission
band position possibleGarnets Lu3Al5O12:Ce band position possible
4. Phosphor Converted LEDs
First all nitride LED demonstrated in 2005 (QE > 0.9, QErel(200 °C) > 0.95)
(In,Ga)N LED + SrSi2N2O2:Eu + (Sr,Ca,Ba)2Si5N8:EuColour rendering index > 88
Excellent colour point stability
2.50E-06
3.00E-06
1.11E-01
Drive at 25 °C
45005000
99
Excellent colour point stability with drive is achieved
1.50E-06
2.00E-064.75E-01
1.30E+00
1.92E+00
2.78E+00
4 09E+0020002500300035004000
CC
T, K
91
93
95
97
Ra
5.01E-07
1.00E-064.09E+00
0500
10001500
0 1 2 3 4 585
87
89
1.00E-09380 430 480 530 580 630 680 730 780
Current , A (pulsed)
CCT_25C CCT_125C Ra_25C Ra_125C
R. Mueller-Mach, G.O. Mueller, M.R. Krames, H.A. Höppe, F. Stadler, W. Schnick, T. Jüstel, P.J. Schmidt, All Nitride White Light Emitting Diodes, Phys. Stat. Sol. A 202 (2005) 1727
4. Phosphor Converted LEDs
Eu2+ and Yb2+ Phosphors
Phosphor Emission atEu2+ [Xe]4f7 1,0
Band d
Excitation and emission spectrum of SrSi2N2O2:Yb2+
BaSi2N2O2:Eu 490 nmSrSi2N2O2:Eu 540 nmCaSi2N2O2:Eu 565 nmBa2Si5N8:Eu 580 nm
0,6
0,8
e in
tens
ity
edge
Ba2Si5N8:Eu 580 nmSr2Si5N8:Eu 610 nm(Ca,Sr)AlSiN3:Eu 630 nmCa2Si5N8:Eu 650 nmCaAlSiN :Eu 650 nm
0,2
0,4
Rel
ativ
e
4f14 - 4f135d1
CaAlSiN3:Eu 650 nm
Yb2+ [Xe]4f14
Cam/2Si12-m-nAlm+nOnN16-n:Yb 550 nm
100 200 300 400 500 600 700 8000,0
Wavelength [nm]
m/2 12 m n m n n 16 nM. Mitomo, K. Uheda et al., J. Phys. Chem. B 109 (2005) 9490
SrSi2N2O2:Yb 615 nm Problem: Thermal quenchingV. Bachmann, T. Jüstel, A. Meijerink, C.R. Ronda, P.J. Schmidt, J. Luminescence (2006), , j , , , ( )
4. Phosphor Converted LEDs
Thermal quenching of a typical LED converter material
600000
700000Mitsubishi CaAlSiN3:Eu2+(0,7%)
350 K 400 K 450 K500 K 60000000
70000000
Mitsubishi CaAlSiN3:Eu2+(0,7%)
]
SSL-EX-037 CaAlSiN3:Eu2+
Boltzmann fit of Data14_B
300000
400000
500000
ität [
a.u.
]
500 K 550 K 600 K 650 K 700 K 750 K 40000000
50000000
60000000
sint
egra
l [co
unts
erat
ur-B
erei
ch
100000
200000
300000
Inte
ns
10000000
20000000
30000000
Em
issi
ons
Chi
p-Te
mpe
500 600 700 8000
Wellenlänge [nm]300 400 500 600 700 800
0
Temperatur [K]
• Thermal quenching is a reversible process and occurs for all kind of phosphors• The quenching temperature is a strong function of the activator, host, and its interaction
Tb3+ Ln3+
5. Towards Ultimate Efficiency and CRICauses for the reduction in luminous efficacy
1 Spectral interaction due to re-absorption
Eu2+ Mn2+ Mn4+
1. Spectral interaction due to re absorption2. Reduction in lumen equivalent
„Waste“
lm/W
]
Band width [nm] Position (nm) LE (lm/W) Red LED Phosphor90 - 120 635 257 (Ca,Sr)S:Eu
(Ca,Sr,Ba)2Si5N8:Eu
[ nm ]y [
(Ca,Sr,Ba)2Si5N8:Eu(Ca,Sr)AlSiN3:Eu
20 – 30 655 278 Mg2TiO4:Mn4+
20 – 30 620 320 Ln3+ activated(Ln = Pr, Sm, Eu)Mn4+ activated
50 – 60 655 269 Eu2+- activated
50 – 60 620 300 Eu2+- activated
A. Zukauskas et al., Appl. Phys.Lett. 93 (2008) 051115
5. Towards Ultimate Efficiency and CRI
Narrow-band red-emitting Sr[LiAl3N4]:Eu2+
as a next-generation LED-phosphor material”as a next-generation LED-phosphor materialW. Schnick et al., Nature Materials (2014) 1-6Appeared on-line June 22nd
SynthesisLiAlH4 + (1-x) SrH2 + x EuF3 + 2 AlN + N2 (Sr1 xEux)[LiAl3N4] + 3x HF + (3-x) H2 (S 1-x ux)[ 3 4] 3 (3 ) 2RF-furnace, 1000 °C
Optical Propertiesp pmax = 651 nm for 5% Eu2+
FWHM = 1180 cm-1
QE(200 °C) > 95% of QE(RT)Decay time Eu2+ ~ 1.1 µsExc. @ 410 nm Photoionisation!Strong re-absorption of YAG/LuAG PL
5. Towards Ultimate Efficiency and CRI
LED Blue 420 – 480 nm ChippConverter Yellow (Y,Gd,Tb,Lu)Al5O12:Ce
Red Mn4+- phosphor(GE Patent US2006/0169998) Tb3Al5O12:3%Ce + K2[TiF6]:Mn4+(GE Patent US2006/0169998) Tb3Al5O12:3%Ce K2[TiF6]:Mn
Problems: Absorption strength, decay time and stability of red line emitter
5. Towards Ultimate Efficiency and CRI
Challenges• Red narrow band or line emitter 0,8
1,0
CaAlSiN3:Eu (Mitsubishi Chemicals)
[a.u
.]
[Xe]4f65d1
- [Xe]4f7
• Red narrow band or line emitter to increase lumen equivalent
0,4
0,6
mal
ised
inte
nsity
[
• Reduced re-absorption to increase package gain 300 400 500 600 700 800
0,0
0,2
Emission spectrum Excitation spectrum
Nor
m
Wavelength [nm]Wavelength [nm]
0,8
1,0 Emission spectrum Excitation spectrum
QE465 = 48.1%RQ465 = 75.8%QE394 = 54.8%RQ394 = 63.5%a.
u.]
NaGdW2O8:Eu3+(60%)Red emitting ion LE [lm/Wopt.]Eu2+ 80 - 200Eu3+ 220 360
0,4
0,6
RQ394 63.5%x = 0.668y = 0.331LE = 268 lm/Wmax = 616 nmcentroid= 627 nm
alis
ed in
tens
ity [aEu3+ 220 – 360
Sm3+ 240 – 260 Pr3+ 200 – 220
4+
300 400 500 600 700 8000,0
0,2Nor
maMn4+ 80 – 150
Cr3+ < 100 Fe3+ < 100
Wavelength [nm]
5. Towards Ultimate Efficiency and CRI
Luminescence spectra T-dependent integral emission intensity
Eu3+ doped Molybdates, e.g. LiLaMo2O8:Eu and Tb2Mo3O12:Eu
1 0
4x106
5x106
Integral intensity
unts
]
0,6
0,8
1,0 Emission spectrum Excitation spectrum
d in
tens
ity
5% Eu3+
2x106
3x106
sion
max
ima
[Cou
0,2
0,4
Nor
mal
ised
0
1x106Em
iss
1,0
250 300 350 400 450 500 550 600 650 700 7500,0
Wavelength [nm]
100% Eu3+
100 200 300 400 500Temperature [K]
0,5
Nor
mal
ized
Inte
nsity
QE465 ~ 100% LE = 269 lm/WoptR465 = 75% max = 614 nmR 60% 623
250 300 350 400 450 500 550 6000,0
Wavelength [nm]•
R395 = 60% centroid = 623 nmCIE x = 0.665 1/e = 0.39 ms (0.2 x Y2O3:Eu)CIE y = 0.333 d50 = 4.2 µm
• Patent Application Publication US2007/0090327, “Novel red fluorescent powder”, Industrial Technology Research Institute, Taiwan• M. Rico, U. Giebner, et.al, “Growth, spectroscopy, and tunable laser operation of the disordered crystal LiGd(MoO4)2 doped with ytterbium”, J. Opt. Soc. Am. B22 (2006) 1083
5. Towards Ultimate Efficiency and CRI
Phosphor converted LED comprising Tb2Mo3O12:Eu1,0 465 nm LEDs]
1,0 465 nm LED N
0,5
nten
sity
[~co
unts
0,5
+ Tb2Mo3O12:Eu3+ (40%) ceramic
Norm
alized Inten
465 nm InGaN LED 0,0
Nor
mal
ized
In0,0
nsity [~counts]
Tb3+
465 nm InGaN LED400 450 500 550
0,0
400 450 500 550 600 650 700 750 800
0,0
Wavelength [nm]1,0 380 nm LED
ount
s]
1,0 380 nm LED
+ Tb2Mo3O12:Eu3+ (40%) ceramic
Norm
a
0,5
zed
Inte
nsity
[~c
0,5
alized Intensity [
380 nm InGaN LED Full conversionLED possible 360 380 400 420
0,0
Nor
mal
iz
350 400 450 500 550 600 650 700 750 8000,0
[~counts]
Wa elength [nm]poss b e Wavelength [nm]
5. Towards Ultimate Efficiency and CRILE and CRI calculations of warm-white phosphor converted LEDs
Tb2Mo3O12:EuTb2Mo3O12:Eugives 20% higher LE comparedto SrLiAl N :Euto SrLiAl3N4:Eu
The reduced reThe reduced re-absorption in Eu3+
phosphor i i LEDcomprising LEDs
gives potentially higher package gain as well …..
5. Towards Ultimate Efficiency and CRIPowder/polymer composites CeramicsVariable layer thickness Homogeneous layer thicknessStrong scattering Little scatteringStrong scattering Little scatteringHigh thermal resistance Low thermal resistanceDrop-Stop Pick & Place
Blue LED + inorganic luminescentpowder in epoxy- or silicon resin
Blue LED + ceramic converter(Lumiramic or c2)
5. Towards Ultimate Efficiency and CRI
Eu3+ doped molybdates as red colour converter in white-emitting pcLEDs
Useful in near UV emitting LEDs (380 - 420 nm)
C i f d itti d i t i Conversion of red emitting powders into ceramics
1,0
0,8
1,0LiEuMo2O8 LED Max = 394 nm LED Max= 464 nm
u.]
0,4
0,6
Inte
nsity
[a.u
250 300 350 400 450 500 5500,0
0,2
Wavelength [nm]
6. Summary and Outlook
LiEuMo2O8, Li3Ba2Eu3Mo8O32, Tb2Mo3O12:Eu (Sm) - Are these luminescent converters applicable in white light emitting pcLEDs?luminescent converters applicable in white light emitting pcLEDs?
+ Cost effective and scalable synthesis routes+ ~ 20% higher lumen equivalent than Eu2+ doped sulphides and nitrides+ Quantum yield at ambient temperature close to unity+ Less than 20% thermal quenching upon heating to 150 °C+ Reasonable absorption strength between 370 and 410 nm
- Narrow width of absorption 4f-4f line multipletsa o dt o abso pt o e u t p ets- Diffuse reflectance at 465 and 535 nm still 70 - 80%
Useful in pcLEDs comprising a near UV emitting (In Ga)N die (370 – 410 nm) Useful in pcLEDs comprising a near UV emitting (In,Ga)N die (370 410 nm) as a pump source
Further optimisation by ceramic preparation or multiple activator ion sites, as inTb2MoO6:Euas inTb2MoO6:Eu
6. Summary and Outlook
Cool white LEDs Warm white LEDs Warm White LEDs (near UV)1. Blue chip Blue chip Blue/cyan luminescent materialp p y2. Ln3Al5O12:Ce Ln3Al5O12:Ce Ln3Al5O12:Ce3. None CaS:Eu/Sr2Si5N8:Eu CaS:Eu/Sr2Si5N8:Eu/CaAlSiN3:Eu
CaAlSiN3:Eu Eu3+-doped molybdatesCaAlSiN3:Eu Eu doped molybdates
Red line emitters Eu3+ doped molybdates/tungstates• Strong absorption at 395, 465, 535 nm
1,0 5D0 - 7FJ
Emission spectrum Excitation spectrumReflection spectrum
LiLaMo2O8:5%Eu3+
Strong absorption at 395, 465, 535 nm• Quantum efficiency ~ 100%• Problem: Absorption strength in the blue
weak compared to CaS:Eu and Sr2Si5N8:Eu 0 4
0,6
0,8Reflection spectrum
QE465 = 41%RQ465 = 65%
ive
inte
nsity
weak compared to CaS:Eu and Sr2Si5N8:Eu
Next steps 150 200 250 300 350 400 450 500 550 600 650 700 7500,0
0,2
0,4
Rel
at
Next steps• Increase average particle size to enhance absorption strength• Final goal: Transparent ceramics?• Development of further stable green yellow and red line phosphors with
150 200 250 300 350 400 450 500 550 600 650 700 750Sample DU084-06
Wavelength [nm]
• Development of further stable green, yellow and red line phosphors withhigh luminous efficiency
10006. Summary and Outlook
100
W/c
m2 ]Increase of the
power density
10
of L
ED [W 8000 lm module (CREE)
1
dens
ity o
0.1al
pow
er
0.001
0.01
Opt
ic
Further power density1960 1970 1980 1990 2000 2010
YearDevelopment of the power density of LED
(source: fairchildsemi com)
p yincrease will requirephosphors with improvedlinearity (source: fairchildsemi.com)
Acknowledgement• Research Group “Tailored Optical Materials“
for synthesis, photographs, spectroscopy, and so on….
• University Tübingen, GermanyProf. Jürgen Meyer for inspiring discussions on solid state chemistryon solid state chemistry
• Universiteit Utrecht, The NetherlandsProf. Andries Meijerink for fruitful discussions on luminescence physics
• FEE Idar-Oberstein for crystal growth andfr itf l collaboration on laser gain mediafruitful collaboration on laser gain media
• Merck KGaA Darmstadt for generous financial supportpp