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Inorganic Luminescent Materials -1- Thomas Jüstel FH Münster – Philips Research Aachen - Schlüsselmaterialien für hocheffiziente Lichtquellen - Thomas Jüstel [email protected] [email protected] 15. März 2005 Anorganische Leuchtstoffe

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Page 1: Anorganische Leuchtstoffe - FH Münster · FH Münster – Philips Research Aachen - Schlüsselmaterialien für hocheffiziente Lichtquellen - Thomas Jüstel tj@fh-muenster.de thomas.juestel@philips.com

Inorganic Luminescent Materials-1-

Thomas JüstelFH Münster – Philips Research Aachen

- Schlüsselmaterialien für hocheffiziente Lichtquellen -

Thomas Jü[email protected]

[email protected]

15. März 2005

Anorganische Leuchtstoffe

Page 2: Anorganische Leuchtstoffe - FH Münster · FH Münster – Philips Research Aachen - Schlüsselmaterialien für hocheffiziente Lichtquellen - Thomas Jüstel tj@fh-muenster.de thomas.juestel@philips.com

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

Page 3: Anorganische Leuchtstoffe - FH Münster · FH Münster – Philips Research Aachen - Schlüsselmaterialien für hocheffiziente Lichtquellen - Thomas Jüstel tj@fh-muenster.de thomas.juestel@philips.com

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

Page 4: Anorganische Leuchtstoffe - FH Münster · FH Münster – Philips Research Aachen - Schlüsselmaterialien für hocheffiziente Lichtquellen - Thomas Jüstel tj@fh-muenster.de thomas.juestel@philips.com

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

Page 5: Anorganische Leuchtstoffe - FH Münster · FH Münster – Philips Research Aachen - Schlüsselmaterialien für hocheffiziente Lichtquellen - Thomas Jüstel tj@fh-muenster.de thomas.juestel@philips.com

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

Page 6: Anorganische Leuchtstoffe - FH Münster · FH Münster – Philips Research Aachen - Schlüsselmaterialien für hocheffiziente Lichtquellen - Thomas Jüstel tj@fh-muenster.de thomas.juestel@philips.com

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

Page 7: Anorganische Leuchtstoffe - FH Münster · FH Münster – Philips Research Aachen - Schlüsselmaterialien für hocheffiziente Lichtquellen - Thomas Jüstel tj@fh-muenster.de thomas.juestel@philips.com

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

Page 8: Anorganische Leuchtstoffe - FH Münster · FH Münster – Philips Research Aachen - Schlüsselmaterialien für hocheffiziente Lichtquellen - Thomas Jüstel tj@fh-muenster.de thomas.juestel@philips.com

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)

Page 9: Anorganische Leuchtstoffe - FH Münster · FH Münster – Philips Research Aachen - Schlüsselmaterialien für hocheffiziente Lichtquellen - Thomas Jüstel tj@fh-muenster.de thomas.juestel@philips.com

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

Page 10: Anorganische Leuchtstoffe - FH Münster · FH Münster – Philips Research Aachen - Schlüsselmaterialien für hocheffiziente Lichtquellen - Thomas Jüstel tj@fh-muenster.de thomas.juestel@philips.com

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

100 200 300 4000,0

0,2

0,4

0,6

0,8

1,0

365 nm185 nm

254 nm

Emis

sion

inte

nsity

[a.u

.]

Wavelength [nm]

Page 11: Anorganische Leuchtstoffe - FH Münster · FH Münster – Philips Research Aachen - Schlüsselmaterialien für hocheffiziente Lichtquellen - Thomas Jüstel tj@fh-muenster.de thomas.juestel@philips.com

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

0,4

0,6

0,8

1,0

LaPO4:Ce BaSi2O5:Pb

UV-AUV-B

Em

issi

on in

tens

ity [a

.u.]

Wavelength[nm]

Page 12: Anorganische Leuchtstoffe - FH Münster · FH Münster – Philips Research Aachen - Schlüsselmaterialien für hocheffiziente Lichtquellen - Thomas Jüstel tj@fh-muenster.de thomas.juestel@philips.com

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

200 300 400 500 600 700 8000,0

20,0

40,0

60,0

80,0

100,0

R

efle

ctio

n [%

]

Wavelength [nm]

Reflection spectrum

Page 13: Anorganische Leuchtstoffe - FH Münster · FH Münster – Philips Research Aachen - Schlüsselmaterialien für hocheffiziente Lichtquellen - Thomas Jüstel tj@fh-muenster.de thomas.juestel@philips.com

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

0,4

0,6

0,8

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

0,6

0,8

1,0

Inte

nsity

(a.u

.)

Wavelength [nm]

Page 14: Anorganische Leuchtstoffe - FH Münster · FH Münster – Philips Research Aachen - Schlüsselmaterialien für hocheffiziente Lichtquellen - Thomas Jüstel tj@fh-muenster.de thomas.juestel@philips.com

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]

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

Page 15: Anorganische Leuchtstoffe - FH Münster · FH Münster – Philips Research Aachen - Schlüsselmaterialien für hocheffiziente Lichtquellen - Thomas Jüstel tj@fh-muenster.de thomas.juestel@philips.com

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

Page 16: Anorganische Leuchtstoffe - FH Münster · FH Münster – Philips Research Aachen - Schlüsselmaterialien für hocheffiziente Lichtquellen - Thomas Jüstel tj@fh-muenster.de thomas.juestel@philips.com

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

Page 17: Anorganische Leuchtstoffe - FH Münster · FH Münster – Philips Research Aachen - Schlüsselmaterialien für hocheffiziente Lichtquellen - Thomas Jüstel tj@fh-muenster.de thomas.juestel@philips.com

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

0,6

0,8

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

Page 18: Anorganische Leuchtstoffe - FH Münster · FH Münster – Philips Research Aachen - Schlüsselmaterialien für hocheffiziente Lichtquellen - Thomas Jüstel tj@fh-muenster.de thomas.juestel@philips.com

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

Page 19: Anorganische Leuchtstoffe - FH Münster · FH Münster – Philips Research Aachen - Schlüsselmaterialien für hocheffiziente Lichtquellen - Thomas Jüstel tj@fh-muenster.de thomas.juestel@philips.com

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

Page 20: Anorganische Leuchtstoffe - FH Münster · FH Münster – Philips Research Aachen - Schlüsselmaterialien für hocheffiziente Lichtquellen - Thomas Jüstel tj@fh-muenster.de thomas.juestel@philips.com

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

100 200 300 400 500 600 700 8000,0

0,2

0,4

0,6

0,8

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

Page 21: Anorganische Leuchtstoffe - FH Münster · FH Münster – Philips Research Aachen - Schlüsselmaterialien für hocheffiziente Lichtquellen - Thomas Jüstel tj@fh-muenster.de thomas.juestel@philips.com

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+

100 200 300 400 500 600 700 8000,0

0,2

0,4

0,6

0,8

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

0,2

0,4

0,6

0,8

1,0

0,0

0,2

0,4

0,6

0,8

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

Page 22: Anorganische Leuchtstoffe - FH Münster · FH Münster – Philips Research Aachen - Schlüsselmaterialien für hocheffiziente Lichtquellen - Thomas Jüstel tj@fh-muenster.de thomas.juestel@philips.com

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

Page 23: Anorganische Leuchtstoffe - FH Münster · FH Münster – Philips Research Aachen - Schlüsselmaterialien für hocheffiziente Lichtquellen - Thomas Jüstel tj@fh-muenster.de thomas.juestel@philips.com

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

0,4

0,6

0,8

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

Page 24: Anorganische Leuchtstoffe - FH Münster · FH Münster – Philips Research Aachen - Schlüsselmaterialien für hocheffiziente Lichtquellen - Thomas Jüstel tj@fh-muenster.de thomas.juestel@philips.com

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

Page 25: Anorganische Leuchtstoffe - FH Münster · FH Münster – Philips Research Aachen - Schlüsselmaterialien für hocheffiziente Lichtquellen - Thomas Jüstel tj@fh-muenster.de thomas.juestel@philips.com

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

0,4

0,6

0,8

1,0

Inte

nsity

[a.u

.]

Wavelength [nm]

0,0

0,2

0,4

0,6

0,8

1,0

Emission ofphosphor converterLight

Source

Absorption

Page 26: Anorganische Leuchtstoffe - FH Münster · FH Münster – Philips Research Aachen - Schlüsselmaterialien für hocheffiziente Lichtquellen - Thomas Jüstel tj@fh-muenster.de thomas.juestel@philips.com

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

Page 27: Anorganische Leuchtstoffe - FH Münster · FH Münster – Philips Research Aachen - Schlüsselmaterialien für hocheffiziente Lichtquellen - Thomas Jüstel tj@fh-muenster.de thomas.juestel@philips.com

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

0,2

0,4

0,6

0,8

1,0

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

Page 28: Anorganische Leuchtstoffe - FH Münster · FH Münster – Philips Research Aachen - Schlüsselmaterialien für hocheffiziente Lichtquellen - Thomas Jüstel tj@fh-muenster.de thomas.juestel@philips.com

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

100 200 300 400 500 600 700 8000,0

0,2

0,4

0,6

0,8

1,0

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)

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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

500 600 700 8000,0

0,2

0,4

0,6

0,8

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]

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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

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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

0,2

0,4

0,6

0,8

1,0

Red

Pho

spho

r

Yello

w P

hosp

hor

Blu

e L

ED

Inte

nsity

[a.u

.]

Wavelength [nm]

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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

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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

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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

0,2

0,4

0,6

0,8

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]

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Inorganic Luminescent Materials-35-

Thomas JüstelFH Münster – Philips Research Aachen

Phosphor Converted LEDs (pcLEDs)

LUXEON-warm white -the components

0

0.2

0.4

0.6

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

0.4

0.6

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)

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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

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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)

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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]

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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)

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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

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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

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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!

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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