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Inorganic Luminescent Materials-1-
Thomas JüstelFH Münster – Philips Research Aachen
- Schlüsselmaterialien für hocheffiziente Lichtquellen -
Thomas Jüsteltj@fh-muenster.de
thomas.juestel@philips.com
15. März 2005
Anorganische Leuchtstoffe
Inorganic Luminescent Materials-2-
Thomas JüstelFH Münster – Philips Research Aachen
Outline• Inorganic luminescent materials
– Application areas– Performance criteria– Fundamental aspects
• Fluorescent lamps– Ce3+ and Tb3+ doped LaPO4
• Plasma displays – Eu2+ and Mn2+ doped BaMgAl10O17
• Phosphor converted LEDs– Ce3+ doped Ln3Al5O12– Eu2+ doped AES– Eu2+ doped AE2Si5N8
• Conclusions and outlook
Inorganic Luminescent Materials-3-
Thomas JüstelFH Münster – Philips Research Aachen
Inorganic Luminescent Materials Application Areas
High energy particles
x-rays (< 1 nm)
VUV (100 – 200 nm)
UV-C (200 – 280 nm)
UV-B (280 – 320 nm)
UV-A (320 – 400 nm)
Blue light (400 – 480 nm)
Exc
itatio
n e
nerg
y
Act
ivat
or
S
ensi
tiser
H
ost l
attic
e
Inorganic Luminescent Materials-4-
Thomas JüstelFH Münster – Philips Research Aachen
Inorganic Luminescent Materials
Excitation EmissionHeatHeat
S AEnergy Transfer
Emission
Application AreasFluorescent light sources comprise a luminescent screen (layer), which convert absorbed energy into visible light
How does a phosphor work?It converts absorbed energy into electro-magnetic radiation beyond thermal equilibrium
100 200 300 400 500 600 700 8000,0
0,2
0,4
0,6
0,8
1,0
x = 0.481y = 0.508LE = 395 lm/WQE254 = 89%RQ254 = 20%
Sample YAGaG:Ce
Emission spectrum Excitation spectrum Reflection spectrum
Rel
ativ
e in
tens
ity
Wavelength [nm]
Layer of YAG:Ceµ-particles
Inorganic Luminescent Materials-5-
Thomas JüstelFH Münster – Philips Research Aachen
Inorganic Luminescent MaterialsPerformance criteria
Luminescent material = Host lattice + dopants + defects
Host lattice and dopants (Y1-xEux)2O3 x = 0.0 – 0.1• Selection in accordance to the requirements defined by the application (excitation
energy, absorption strength, chemical environment, temperature....)• Dopant → host lattice: concentration, ion size vs. lattice site size, oxidation state ...
⇒ minimise defect concentration to optimise energy (quantum) efficiency
Defects VK, VA, interstitials• Afterglow• Luminescence quenching (concentration and thermal quenching)
– competitive absorption – energy transfer to defects + non-radiative relaxation– re-absorption of emission
• Stability reduction– formation of colour centres due to electron trapping
Inorganic Luminescent Materials-6-
Thomas JüstelFH Münster – Philips Research Aachen
Inorganic Luminescent Materials
Eu3+
4f6
5423
1 0
4f65d1
5D3
0.0
4.0x104
Ener
gy[c
m-1
]
5d1
5D2
5D15D0
8S7/2
2F7/2
2F5/2
7F6
4f72p-1
Eu2+
4f7Ce3+
4f1Gd3+
4f7Tb3+
4f8
54
2310
7F6
4f75d1
8S7/2
5D4
5D3
6P7/2
6I7/2
254 nm
Excitation via
a) CT transitions
b) 4fn-4fn-15d1 transitions(energetic position isgoverned by host lattice)
c) SensitiserBi3+ → Gd3+
Ce3+ → Tb3+
Eu2+ → Mn2+
Ce3+ → Mn2+
Host lattice → Eu2+
3.5x104
3.0x104
2.5x104
2.0x104
1.5x104
1.0x104
0.5x104
Fundamentals aspects: Simplified energy level schemes of some RE ions
Inorganic Luminescent Materials-7-
Thomas JüstelFH Münster – Philips Research Aachen
Inorganic Luminescent Materials
Free ion Nephelauxetic effect
Crystal field
Free ion: Eu2+ Ce3+ Pr3+ Nd3+
4fn-15d1 level: 34000 cm-1 50000 cm-1 62000 cm-1 70000 cm-1
ec: centroid energy, proportional to spectroscopic polarizability ecfs: crystal field splitting
E
Stokes Shift
5d
4f
εc
εcfs
Fundamentals aspects: Energy Distance between 4f and 5d States
Inorganic Luminescent Materials-8-
Thomas JüstelFH Münster – Philips Research Aachen
Inorganic Luminescent MaterialsFundamental Aspects: Covalency and its translation to chemical composition
Polarizibility (type) of anions• sulphides > nitrides > oxides > fluorides
Charge density on the surrounding anions • Type of network former:
oxides > aluminates > silicates > borates > phosphates > sulphatesO2- AlO6
9- SiO44- BO3
3- PO43- SO4
2-
Degree of connectivity of the network formerSi3O10
8- < Si2O76- < SiO4
4- (ortho-silicates, e.g. Sr2SiO4)
Comment: High charge density on the anions results in high basicity→ sensitivity towards electrophilic agents, i.e. H+ and CO2)
Inorganic Luminescent Materials-9-
Thomas JüstelFH Münster – Philips Research Aachen
Inorganic Luminescent MaterialsColor of Eu2+ Phosphors
Chemical composition λmax– CaS:Eu 655 nm– Sr2Si5N8:Eu 615 nm– SrS:Eu 610 nm– Ba2Si5N8:Eu 580 nm– Sr2SiO4:Eu 575 nm– SrSi2N2O2:Eu 540 nm– SrGa2S4:Eu 535 nm– SrAl2O4:Eu 520 nm– Ba2SiO4:Eu 505 nm
– Sr4Al14O25:Eu 490 nm
– SrSiAl2O3N:Eu 480 nm– BaMgAl10O17:Eu 450 nm– Sr2P2O7:Eu 420 nm– SrB4O7:Eu 368 nm In
crea
seof
cov
alen
cy o
r cr
ysta
l-fie
ld st
reng
th
Nitrides +Sulfides
Oxynitrides+ Oxides
Inorganic Luminescent Materials-10-
Thomas JüstelFH Münster – Philips Research Aachen
Fluorescent Lamps
Hg discharge 185 + 254 nm visible lightPhosphor
Atomic Hg Emission
DesiredSpectrum
Phosphorlayer
Hg atom Electrons
Electrode
CapGlass Tube
Purification Disinfection Illumination
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0,2
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1,0
365 nm185 nm
254 nm
Emis
sion
inte
nsity
[a.u
.]
Wavelength [nm]
Inorganic Luminescent Materials-11-
Thomas JüstelFH Münster – Philips Research Aachen
Fluorescent Lamps
Medical therapy/tanning
Illumination
300 400 500 600 700 8000,0
0,2
0,4
0,6
0,8
1,0Eye-sensitivity curve
Eu3+Tb3+Eu2+
Em
issi
on in
tens
ity [a
.u.]
Wavelength [nm]
UV-B Ce3+
LaPO4:Ce (Monazite)
UV-A Pb2+
BaSi2O5:Pb (Sanbornite)
Blue Eu2+
Sr5(PO4)3(F,Cl):Eu (Halophosphate)BaMgAl10O17:Eu (ß-Alumina)
Green Tb3+
LaPO4:Ce,Tb (Monazite)LaMgAl11O19:Ce,Tb (Magnetoplumbite)
Red Eu3+
Y2O3:Eu (Bixbyite)
280 300 320 340 360 380 4000,0
0,2
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0,8
1,0
LaPO4:Ce BaSi2O5:Pb
UV-AUV-B
Em
issi
on in
tens
ity [a
.u.]
Wavelength[nm]
Inorganic Luminescent Materials-12-
Thomas JüstelFH Münster – Philips Research Aachen
Fluorescent LampsCe3+ and Tb3+ doped LaPO4 (Monazite structure)
• High thermal stability and radiation hardness• Wide band gap (8.2 eV ~ 150 nm)• CePO4 and TbPO4 crystallises in the same structure type
⇒ (La1-x-yCexTby)PO4 with x, y = 0.0 – 1.0• Low covalency and weak crystal field (CN = 9)
⇒ Ce3+ absorption and emission bands are located in the UV range
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100,0
R
efle
ctio
n [%
]
Wavelength [nm]
Reflection spectrum
Inorganic Luminescent Materials-13-
Thomas JüstelFH Münster – Philips Research Aachen
Fluorescent LampsCe3+ and Tb3+ doped LaPO4 (Monazite structure)
LaPO4:CeCe3+ → (Ce3+)* Absorption 4f - 5d(Ce3+)* → Ce3+ Emission 5d - 4f
LaPO4:TbTb3+ → (Tb3+)** Absorption 4f - 5d(Tb3+)** → (Tb3+)* Relaxation to 4f level(Tb3+)* → Tb3+ Emission 4f - 4f
LaPO4:Ce, TbCe3+ → (Ce3+)* Absorption 4f - 5d(Ce3+)* + Tb3+ → Ce3+ + (Tb3+)* ET from Ce to Tb(Tb3+)* → Tb3+ Emission 4f - 4f
Efficiently excited by 254 nm radiation!200 300 400 500 600 700 800
0,0
0,2
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1,0Tb3+ absorption
Tb3+ 4f4f emission
Ce3+ absorption
Inte
nsity
(a.u
.)
Wavelength [nm]
200 300 400 500 600 700 8000,0
0,2
0,4
0,6
0,8
1,0 Tb3+ 4f5d absorption
Sample V1377
Inte
nsity
(a.
u.)
Wavelength [nm]
Tb3+ 4f4f emission
200 300 400 500 600 700 8000,0
0,2
0,4
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1,0
Inte
nsity
(a.u
.)
Wavelength [nm]
Inorganic Luminescent Materials-14-
Thomas JüstelFH Münster – Philips Research Aachen
0
0,05
0,1
0,15
0,2
0,25
0,3
0,35
350 400 450 500 550 600 650 700 750 800
Inte
nsity
[W/n
m]
λ [nm]
Vλ
BaMgAl10O17:Eu
LaPO4:Ce,Tb
Y2O3:Eu
Prad / P ≈ 60 %Prad,vis / P ≈ 30 %
P = 36 W
Fluorescent LampsSpectrum of a trichromatic compact or tubular lamp
Inorganic Luminescent Materials-15-
Thomas JüstelFH Münster – Philips Research Aachen
R G B
Display Electrode (ITO)
Bus electrode (CrCuCr)
Barrier ribs
Rear glass plate (PD200)
Front glass plate (PD200)
Dielectric layer
Address electrode (Ag)
Protection layer (MgO)
Phosphors (R, G, B)
Dielectric layer
Assembly (NeXe fill)
Process flow
Plasma DisplaysSchematic build-up
Inorganic Luminescent Materials-16-
Thomas JüstelFH Münster – Philips Research Aachen
Plasma Displays
Xe/Ne plasma emission occurs from• Xe (3P1) 147 nm line (145 - 149 nm)• Xe2*-excimers 172 nm band (160 - 190 nm)
Light generation in PDPs
Inorganic Luminescent Materials-17-
Thomas JüstelFH Münster – Philips Research Aachen
Plasma Displays
BlueBaMgAl10O17:Eu
GreenZn2SiO4:MnBaAl12O19:MnBaMgAl10O17:(Eu),Mn
Red(Y,Gd)BO3:Eu (Y,Gd)2O3:Eu (Y,Gd)(V,P)O4:Eu 400 450 500 550 600 650 700
0,0
0,2
0,4
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1,0
Nor
mal
ized
em
issi
on in
tens
ity
(Y,Gd)BO3:Eu
Zn2SiO4:Mn
BaM
gAl10 O
17 :Eu
Wavelength [nm]
Emission spectra of standard phosphors
VUV Phosphors for PDPs
Strong absorption and efficiency under VUV excitation required
Inorganic Luminescent Materials-18-
Thomas JüstelFH Münster – Philips Research Aachen
Plasma Displays
Incorporation of dopants• Eu2+ → conduction layers• Yb2+ → conduction layers• Ti3+ → spinel blocks• Cr3+ → spinel blocks • Mn2+→ spinel blocks• Co3+ → spinel blocks
Derived from β-alumina NaAl11O17
Spinel block MgAl10O16
Conduction layer BaO
Spinel block MgAl10O16
Conduction layer BaO
Spinel block MgAl10O16
Unit cell
Structure of BaMgAl10O17
Inorganic Luminescent Materials-19-
Thomas JüstelFH Münster – Philips Research Aachen
Plasma Displays
Ba2+ (Eu2+) is ninefold co-ordinated (tri-capped trigonal prisma D3h)Relatively small crystal field splitting ⇒ blue emission band
Ba2+ coordination sphereLayer structure
Structure of BaMgAl10O17
Inorganic Luminescent Materials-20-
Thomas JüstelFH Münster – Philips Research Aachen
• Optical band gap Eg = 7.0 eV (~180 nm)• Excitation bands at 170, 250, and 310 nm (4f7 → 4f65d1)• Emission band at 453 nm ⇒ x = 0.150 y = 0.060• QE254nm > 90%
100 200 300 400 500 600 700 8000,0
20,0
40,0
60,0
80,0
100,0Host lattice
Eu2+
4f7 - 4f65d1
R
efle
ctio
n [%
]
Wavelength [nm]
Reflection spectra Emission and excitation spectra
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1,04f65d1 - 4f7Host lattice
Rel
ativ
e In
tens
ity
Wavelength [nm]
4f7 - 4f65d1
Luminescence of BAM doped by 10% Eu2+ (solubility limit ~ 30%)
Plasma Displays
Inorganic Luminescent Materials-21-
Thomas JüstelFH Münster – Philips Research Aachen
BaMgAl10O17: exc. at λmax at x y transitionCr3+ 190 nm 694 nm 0.596 0.257 3d3-3d3
Mn2+ 180 nm 515 nm 0.146 0.722 3d5-3d5
Luminescence spectra ofBaMgAl10O17:Cr3+
Luminescence spectra ofBaMgAl10O17:Mn2+
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1,0
0
20
40
60
80
100
Reflection (%
)
Emission spectrum Excitation spectrum Reflection spectrum
Rel
ativ
e in
tens
ity
Wavelength [nm]
100 200 300 400 500 600 700 8000,0
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1,0
Reflection (%
)
Emission spectrum Excitation spectrum Reflectionspectrum
Rel
ativ
e in
tens
ity
Sample WM123Wavelength [nm]
Plasma DisplaysBAM:Eu doped by transition metal ions
Inorganic Luminescent Materials-22-
Thomas JüstelFH Münster – Philips Research Aachen
Divalent RE ions Ba2+ sites in the conduction layer Eu2+, Yb2+
Divalent TM ions tetrahedral gaps in the spinel blocks Mn2+, Co2+
Trivalent TM ions octahedral gaps in the spinel blocks Cr3+, Ti3+
λ1
λ2
λUV
BaMgAl10O17:Eu co-doped by transition metal ions
Plasma Displays
Energy Transfer
Inorganic Luminescent Materials-23-
Thomas JüstelFH Münster – Philips Research Aachen
• Efficient energy transfer from Eu2+ to Mn2+
• Eu2+ improves VUV efficiency of Mn2+ doped BaMgAl10O17
• High Mn2+ concentration reduces VUV efficiency of BaMgAl10O17:Eu,Mn
300 350 400 450 500 550 6000,0
0,2
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1,0 BAM-I:0.05Mn BAM-I:0.10Eulow Mn BAM-I:0.10EumediumMn BAM-I:0.10EuhighMn
Rel
ativ
e in
tens
ity
Wavelength [nm]150 200 250 300 350
0,0
0,2
0,4
0,6
0,8
1,0
BAM-I:0.05Mn BAM-I:0.1EumediumMn BAM-I:0.1EuhighMn
Ligh
t out
put L
O =
QE*
(1-R
)
Wavelength [nm]
Emission spectra Light output
BaMgAl10O17:Eu doped by Mn2+
Plasma Displays
Inorganic Luminescent Materials-24-
Thomas JüstelFH Münster – Philips Research Aachen
CB
VB
4f65d1
3d5
Eu2+ Mn2+
ET
Eg = 7.0 eV(< 180 nm)
250 nm
Host lattice Eu2+(4f65d1) Mn2+(3d5*)sensitizer for Mn2+ luminescence
Mn2+(3d5)
ET ET
515 nm
450 nm 515 nm310 nm
3d5*
4f7(8S7/2)
170 nm
Energy pathways in BaMgAl10O17:Eu,Mn
Plasma Displays
Inorganic Luminescent Materials-25-
Thomas JüstelFH Münster – Philips Research Aachen
Phosphor Converted LEDs (pcLEDs)
Blue LED chip 420 – 480 nm emitting InGaNPhosphor conversion layerpcLED with Tc > 4000 K „Cool white“ (Y,Gd)3(Al,Ga)5O12:CepcLED with Tc < 4000 K „Warm white“ (Y,Gd)3(Al,Ga)5O12:Ce + red
InGaN die Silicone
phosphor
Ag-Mirror
400 450 500 550 600 650 700 750 8000,0
0,2
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1,0
Inte
nsity
[a.u
.]
Wavelength [nm]
0,0
0,2
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0,8
1,0
Emission ofphosphor converterLight
Source
Absorption
Inorganic Luminescent Materials-26-
Thomas JüstelFH Münster – Philips Research Aachen
Phosphor Converted LEDs (pcLEDs)
Dodecahedral coordination of YNetwork former: PO4
3- group
Average charge on Oxygen atoms is 0.75 or 6.75 e-/OFew charge flow back to Ln3+
Dodecahedral coordination of YNetwork former: AlO4
5- and AlO69-
Average charge on Oxygen atoms is 1.35 or 7.35 e-/OMuch charge flow back to Ln3+
Ce3+ Emission in YPO4 and Y3Al5O12
Inorganic Luminescent Materials-27-
Thomas JüstelFH Münster – Philips Research Aachen
Phosphor Converted LEDs (pcLEDs)
Crystal-field splitting ~ 18000 cm-1
Centroid shift ~ 9600 cm-1
(P. Dorenbos, Phys. Rev. B, 64, 2001, 1251)⇒ large 4f-5d energy distance⇒ UV emission at 335, 355 nm
1st coordination sphere of Ce3+
(dodecahedral) 100 200 300 400 500 600 700 8000,0
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4f5d
4f5d
Em
issi
on in
tens
ity [a
.u.]
Wavelength [nm]
4f5dFree ion
εcfs
εc
dxzdyz
dz2
dx2-y2
dxy
Y-O distances
4x 2.24 Å4x 2.24 Å1
E
Ce3+ Luminescence in YPO4
Inorganic Luminescent Materials-28-
Thomas JüstelFH Münster – Philips Research Aachen
Crystal-field splitting ~ 27000 cm-1
Centroid shift ~ 14700 cm-1
(P. Dorenbos, Phys. Rev. B, 65, 2002, 2351)⇒ small 4f-5d energy distance⇒ visible emission at 560 nm
1st coordination sphere of Ce3+
(dodecahedral)Y-O distances
4x 2.30 Å4x 2.44 ÅE
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4f5d 4f5d
4f5d
Ban
d ga
p
Em
issi
on in
tens
ity
Wavelength [nm]
Free ion
εcfs
εcfs
εc
Ce3+ Luminescence in Y3Al5O12
Phosphor Converted LEDs (pcLEDs)
Inorganic Luminescent Materials-29-
Thomas JüstelFH Münster – Philips Research Aachen
Phosphor Converted LEDs (pcLEDs)
Garnet structure Ln3Me5O12
• Ln = Y, Ce, Gd, Lu dodecahedral• Me = Al, Ga tetrahedral(3), octahedral(2) • Substitute Y3+ by Ce3+ 560 nm → 565 nm (Red-Shift)• Substitute Y3+ by Gd3+ or Tb3+ 560 nm → 580 nm (Red-Shift)• Substitute Al3+ by Ga3+ or Y3+ by Lu3+ 560 nm → 520 nm (Blue-Shift)
Emission spectra and colour points of Ln3Al5O12:Ce
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1,0 YAG:Ce1% YAG:Ce2% (Gd,Y)AG:Ce2% (Lu,Y)AG:Ce1% LuAG:Ce1%
N
orm
alis
ed e
mis
sion
inte
nsity
Wavelength [nm]
Inorganic Luminescent Materials-30-
Thomas JüstelFH Münster – Philips Research Aachen
Phosphor Converted LEDs (pcLEDs)Spectra of cool white pcLEDs based on (Y,Gd)3Al5O12:Ce
• Colour rendition CRI = 70 – 80• Cool white light emission• Wall plug efficiency:
high brightness 50 lm/Wlow brightness 70 - 80 lm/W
• Lifetime 50000h, 90% at 12000h• Lack of red radiation
0
10
20
30
40
50
60
70
400 500 600 700 800
Emis
sion
inte
nsity
Tc = 5270 K: CRI = 82Tc = 4490 K: CRI = 79Tc = 4110 K: CRI = 76Tc = 3860 K: CRI = 73Tc = 3540 K: CRI = 70
Wavelength [nm]• (Y,Gd)3Al5O12:Ce is very efficient and (photo)chemically stable• Typical Ce3+ concentration is ~ 1%• Higher Ce3+ concentration results in a red-shift of the emission band and
thus in a higher colour rendering, but results in concentration quenchingr(Y3+) = 1.16 Å r(Ce3+) = 1.28 Å r(Ce4+) = 1.11 Å for CN = 8
Inorganic Luminescent Materials-31-
Thomas JüstelFH Münster – Philips Research Aachen
Phosphor Converted LEDs (pcLEDs)
InGaN die Silicone
yellow phosphorred
phosphor
White pcLEDs with a high colour rendering require additional red phosphor
1. Blue LED + (Y,Gd)AG:Ce ⇒ CRI > 75 only for Tc > 4000 K
2. Blue LED + YAG:Ce + Red ⇒ CRI > 85 for Tc < 4000 K
400 500 600 700 8000,0
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1,0
Red
Pho
spho
r
Yello
w P
hosp
hor
Blu
e L
ED
Inte
nsity
[a.u
.]
Wavelength [nm]
Inorganic Luminescent Materials-32-
Thomas JüstelFH Münster – Philips Research Aachen
Phosphor Converted LEDs (pcLEDs)Red-emitting LED phosphors
Shortcomings of Ce3+
• Rather narrow absorption band• Rather broad emission band• No known red-emitting Ce3+ phosphor with a high thermal quenching
temperature at the same time
Alternative activators• Mn2+: Sensitisation required, saturation• Eu3+: Y2O2S:Eu, CT band < 360 nm, thermal quenching• Eu2+: Strong covalency and CFS required
Best choice are Eu2+ activated luminescent materials⇒ AES:Eu⇒ AE2Si5N8:Eu
Inorganic Luminescent Materials-33-
Thomas JüstelFH Münster – Philips Research Aachen
Phosphor Converted LEDs (pcLEDs)
• Rock salt structure
• High sensitivity towards O2, H2O, diluted acids, etc.
• Activator: Eu2+
– on octahedral AE2+ sites– strong 4f-5d absorption bands
below 550 nm– quantum efficiency > 90% – red emission tunable by
adjustment of Sr/Ca content
S
Ca,Sr
Eu
Structure and luminescence of (Ca,Sr)S:Eu
Inorganic Luminescent Materials-34-
Thomas JüstelFH Münster – Philips Research Aachen
Phosphor Converted LEDs (pcLEDs)Spectra of (Ca1-xSrx)S:Eu
Substitution of Sr by Ca yields a red-shift and improves stability
SrS:Eu CaS:Eustability
Crystal field strength
Centroid shift
Composition QE [%] Abs. [%] LE [lm/W] x yCaS:Eu > 95 > 80 90 0.697 0.303SrS:Eu > 95 > 80 260 0.629 0.370
500 600 700 8000,0
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1,0 SrS:Eu (Sr0.75Ca0.25)S:Eu (Sr0.5Ca0.5)S:Eu (Sr0.25Ca0.75)S:Eu CaS:Eu
Emis
sion
inte
nsity
[a.u
.]
Wavelength [nm]
Inorganic Luminescent Materials-35-
Thomas JüstelFH Münster – Philips Research Aachen
Phosphor Converted LEDs (pcLEDs)
LUXEON-warm white -the components
0
0.2
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0.8
1
1.2
400 450 500 550 600 650 700 750 800nm
blue YAG:Ce CaS: Eu
LUXEON-warm white -the components
0
0.2
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0.8
1
1.2
400 450 500 550 600 650 700 750 800nm
blue YAG:Ce CaS: Eu
Blue LED + YAG:Ce + CaS:Eu2+
More red: lower CCT, more blue: higher CCT
2700 < CCT < 5500 K Excellent colour rendition 400 450 500 550 600 650 700 750 800
nm
black body 3600 K
fluorescent, CCT=3600 K
0
5
4
4
4
4
4
4
4
4
400 450 500 550 600 650 700 750nm
JAZZ 3300K
BB 3300K
Warm white LEDs (LumiLeds)
Inorganic Luminescent Materials-36-
Thomas JüstelFH Münster – Philips Research Aachen
Phosphor Converted LEDs (pcLEDs)Nitride phosphors
Advantages over oxides and sulfides• highly condensed anionic networks
⇒ high density⇒ high chemical stability⇒ high hardness⇒ high quenching temperature
• higher charge density between activator and nitride ligands: oxides < oxynitrides < nitrides < nitridocarbides⇒ large red-shift of emission band (5d-4f emitter)
Si X = O2- X = N3- X = C4-
r [pm] 26 138 146 160Electronegativity χ 1.92 3.61 3.07 2.54Ionic bonding Si-X [%] - 51 28 9
Inorganic Luminescent Materials-37-
Thomas JüstelFH Münster – Philips Research Aachen
Nitridosilicates AE2Si5N8:Eu2+ (AE = Ca, Sr, Ba)
2 Sr + Eu + 5 Si(NH)2
Sr2Si5N8:Eu + N2 + 5 H2
Structure of Sr2Si5N8 Synthesis
Ca2Si5N8:Eu monoclinic 650 nmSr2Si5N8:Eu orthorhombic 615 nm Ba2Si5N8:Eu orthorhombic 580 nm
Phosphor Converted LEDs (pcLEDs)
Inorganic Luminescent Materials-38-
Thomas JüstelFH Münster – Philips Research Aachen
Phosphor Converted LEDs (pcLEDs)
Composition Body color Emission band x y LE______Sr2Si5N8:Eu orange-red 615 nm 0.615 0.384 271 lm/WBa2Si5N8:Eu orange 580 nm 0.516 0.482 472 lm/W
550 600 650 700 750 8000
100
200
300
400
500
600
700
800
900
1000
Inte
nsity
[cou
nts]
Wavelength [nm]
Increasing Eu2+ concentration
Reflection spectra of Emission spectra of (Ba1-xEux)2Si5N8Sr2Si5N8:Eu and Ba2Si5N8:Eu
Optical properties of (Sr,Ba)2Si5N8:Eu
300 400 500 600 700 8000,0
20,0
40,0
60,0
80,0
100,0
Sr2Si5N8:Eu Ba2Si5N8:Eu
R
efle
ctio
n [%
]
Wavelength [nm]
Inorganic Luminescent Materials-39-
Thomas JüstelFH Münster – Philips Research Aachen
• Replacement of Nitrogen by Oxygen is charge compensated by thesubstitution of Silicon by Aluminum
• Substitution of Si, N by Al, O yields red shift of the emission band
300 400 500 600 700 8000,0
0,5
1,0
0,0
0,5
1,0
Si,N --> Al,O
Emission spectraExcitation spectra
Rel
ativ
e in
tens
ity
Wavelength [nm]
Luminescence spectra of Sr2Si5-xAlxN8-xOx:Eu
Phosphor Converted LEDs (pcLEDs)
Inorganic Luminescent Materials-40-
Thomas JüstelFH Münster – Philips Research Aachen
Structure and optical properties of SrSi2N2O2:Eu
„Formal“ synthesis (by accident)Sr2Si5N8:Eu + 6 H2O → 2 SrSi2N2O2:Eu + SiO2 + 4 NH3
Layer structure Emission spectra as function of c(Eu2+)
Phosphor Converted LEDs (pcLEDs)
500 550 600 650 700 750 8000,0
0,2
0,4
0,6
0,8
1,0
Em
issi
on In
tens
ity (a
.u.)
wavelength/ nm
Inorganic Luminescent Materials-41-
Thomas JüstelFH Münster – Philips Research Aachen
400 500 600 700 8000,00
0,02
0,04
0,06
0,08
0,10
0,12
0,14 Ra8 Ra14
90 8692 8889 8589 8586 8186 8385 83
Tc2700K Tc2900K Tc4000K TC5000K Tc6300K Tc8000K Tc8600K
Em
issi
on in
tens
ity [a
.u.]
Wavelength [nm]
InGaN LED 460 nmSrSi2N2O2:Eu 540 nmSr2Si5N8:Eu,Al,O 615 nm
Colour rendition > 88 for 2800 < CCT < 6000 KWhite, green, yellow, red is possible by tuning composition and Eu2+ conc.
Phosphor Converted LEDs (pcLEDs)All nitride white pcLED
Inorganic Luminescent Materials-42-
Thomas JüstelFH Münster – Philips Research Aachen
Conclusions and OutlookPhosphors consist of host lattices doped with high concentrations of activators ions
Application in fluorescent lamps• selected phosphors are at their physical limits• invention of novel materials is very unlikely• development deals with particle morphology and coatings
Novel application areas are• Xe/Ne discharge light sources (plasma displays and excimer lamps)• AlInGaN LEDs
Novel host lattices for phosphors: Nitrides, oxynitrides, SiONes, SiAlONes...• most exciting area in phosphor research since early 1990ties• many new materials at the horizon• nitride phosphors: Large 5d level splitting, high stability, little quenching, ....
Inorganic luminescent materials are the key to high performance and lifetime of gas discharge and solid state light sources!
Inorganic Luminescent Materials-43-
Thomas JüstelFH Münster – Philips Research Aachen
AcknowledgementPFL Aachen IPM Maarheeze Lumileds San JoseVolker Bachmann Jan Broere Mike KramesWolfgang Busselt Rene Hochstenbach Gerd MuellerPetra Huppertz Jan Migchels Regina Mueller-MachWalter Mayr Wouter SchramaJörg Meyer Dick vd Voort LMU MunichCees Ronda Henning HöppePeter J. Schmidt Wolfgang SchnickDieter Wädow Florian StadlerDetlef U. Wiechert
FH MünsterDominik UhlichHelga Bettentrup