Session: LED PhosphorsSession: LED Phosphors...Session: LED PhosphorsSession: LED Phosphors ... •...

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


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


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


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


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]


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


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


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 , , , ( )


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


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


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


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]


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


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)


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


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


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

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