7. Luminescent Materials

Transcription

7. Luminescent Materials
Content
Cd(S,Se) Quantum dots
7.1 History
7.2 Definition and Working Principle
7.3 Luminescence Mechanisms
7.4 Chemical Composition
7.5 Composition and Function
7.6 Application Areas
7.7 Broadband Phosphors
7.8 Line Phosphors
7.9 UV-A Phosphors
7.10 UV-B Phosphors
7.11 UV-C Phosphors
7.12 IR-A Phosphors
Incoherent Light Sources
Prof. Dr. T. Jüstel
Chapter Luminescent Materials
Slide 1
7.1 History
Some milestones
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Stone of Bologna: Barit (Galilei 1600)
Discovery of phosphors (phosphorescence) (Brand 1669)
First phosphor by reaction of shells with sulfur (Canton 1768)
Application of a phosphor in combination with a Hg-discharge (Becquerel 1859)
Patent on the use of CaWO4 in fluorescent lamps (Edison 1896)
Fluorescent lamps with MgWO4 + (Zn,Be)2SiO4:Mn (GE 1938)
Development of Ca5(PO4)3(F,Cl):Sb,Mn (McKeag 1942)
ZnS:Ag, (Zn,Be)2SiO4:Mn and Zn3(PO4)2:Mn for first color CRT (1958)
Fluorescent lamps with Eu- and Tb- phosphors (Verstegen 1974)
First oxidic afterglow pigment SrAl2O4:Eu,Dy (Nemoto 1993)
Nitride phosphors (Schnick 1995)
Transparent ceramics converter for LEDs (Philips 2007)
Narrow band red nitride phosphor Sr[LiAl3N4]:Eu (Schnick 2014)
Slide 2
Definition
A phosphor is a micro-or nanoscale pigment, that after excitation by radiation
(NIR-,VIS-, UV-, X-ray-, gamma-), high-energy particles or matter vibrations
(phonons), emits electromagnetic radiation beyond thermal equilibrium.
In daylight
When excited by electrons or UV radiation
Slide 3
Working principle
1. Excitation:
2. Energy transfer:
3. Relaxation :
Excitation
Source
Absorption of energy from an external source
To activator ions (luminescence) or defects (storage)
Radiative: Emission (luminescence)  Luminescent pigm.
Non-radiative: Heat (phonons)  Pigment
Emission
S
Heat
Heat
Heat
SEM image of (Y,Gd)BO3:Eu
D
A
ET
ET
A
ET
Emission
A
Heat
Heat
ET
Typical particle size 1 - 10 µm
Slide 4
7.3 Luminescence Mechanisms
Typ
Fluorescence
Phosphorescence
Afterglow (pers. luminescence)
Physical process (time scale)
Spin-allowed transition (ns - µs)
Spin-forbidden transition (ms)
Thermal activation of charge carriers (s)
Typ
Photoluminescence
X-rays luminescence
Cathodoluminescence
Electroluminescence
Thermoluminescence
Chemiluminescence
Bioluminescence
Sonoluminescence
Mechanoluminescence
Excitation source
UV photons
X-rays
Electrons
Electric field
Heat
Chemical reaction
Biochemical reaction
Ultrasound
Mechanical energy
Applications
Fluorescent lamps
X-rays intensifier
TVs, monitors
LEDs, EL displays
Age determination
Emergency signals
Fireflies, jellyfish
Slide 5
Organic phosphors
• Usually aromatic compounds
with extended -electron systems
• Examples: Perylenes, coumarines
• Low phonon frequency
O O
O
O
N
N
O
O
O O
Inorganic phosphors
• Host material + Dopants
• Dopants = Activators + Sensitizers + Impurities
• Defects = 0-Dim., 1-Dim., 2-Dim., 3-Dim.
• Example: (La,Ce,Tb)PO4 = LaPO4:Ce,Tb
Ce,Tb:LaPO4 = La1-x-yCexTby(PO4)
Slide 6
Composition  Host material + Dopants + Defects + Impurities
Dopants = Activator/ Sensitizers = RE-, TM- and s2-ions
1
1
2
Zn
H
3
4
Li
Be
11
12
4
5
19
20
21
22
23
K
Ca
Sc
37
38
39
Rb
Sr
Y
Ti
40
Zr
V
41
6
24
7
25
8
14
15
16
17
He
Zn
5
6
7
8
9
10
12
Co
Ni
Cu Zn
Ga
42
45
46
47
49
43
44
29
30
48
Nb Mo Tc
Ru Rh
Pd
Ag Cd
76
78
79
72
73
74
75
Cs
Ba
La
Hf
Ta
W
Re Os
87
88
89
104
105
106
107
108
77
Ir
Pt
109
110
80
Au Hg
111
112
Db Sg
Bh Hs
Mt Ds
Rg
Cn
58
60
62
64
65
Ce
90
Al
Cr Mn Fe
57
59
Pr
91
Th Pa
11
28
56
Ra Ac Rf
10
13
27
26
55
Fr
9
61
63
31
In
81
Tl
93
U
94
95
96
97
C
N
14
15
Si
32
33
Ge
50
P
As
51
O
16
S
34
Se
52
Sn
Sb
Te
82
83
84
Pb
Bi
F
17
Cl
35
Ne
18
Ar
36
Br Kr
53
I
85
Po At
54
Xe
86
Rn
1
2
3
4
5
6
7
66
Nd Pm Sm Eu Gd Tb Dy
92
2
13
B
3
Na Mg
18
98
Np Pu Am Cm Bk Cf
67
68
Ho Er
69
70
71
Tm Yb
Lu
101
102
103
Es Fm Md No
Lr
99
100
Slide 7
6
7
Composition: Preparation listed by the activator (trans. metal and s2-ions)
Activator
Mn2+
Mn2+/Sb3+
Host material
Zn2SiO4 (Willemit)
BaMgAl10O17 (ß-Alumina)
Ca5(PO4)3(Cl,F) (Halophosphat)
Emission at [nm]
Color
Applications
525
515
Green
Green
PDPs, CRTs
PDPs, FLs
480, 580
White
FLs
Mn4+
Mg4GeO5.5F
655
Red
Hg high-pressure lamps
Fe3+
LiAlO2
735
Red
FLs
Cu+
ZnS
530
Green
CRTs
Ag+
ZnS
450
Blue
CRTs
Sn2+
(Sr,Mg)3(PO4)2
630
Red
Sb3+
(Sr,Ca)5(PO4)3(Cl,F)
480
Blue-Green
FLs
NaI
CsI
415
560
Blue
Yellow
x/-ray detectors
x/-ray detectors
Pb2+
BaSi2O5 (Sanbornit)
Sr2MgSi2O7 (Akermanit)
350
365
UV-A
UV-A
FLs for tanning
Bi3+
Bi4Ge3O12
480
Blue-Green
x/-ray detectors
Tl+
Slide 8
Composition: Preparation listed by the activator (trans. metal and s2-ions)
Activator
Host material
Emission at (nm)
Color
Applications
LaPO4
YPO4
Y3Al5O12
320
335, 355
560
UV-B
UV-A
Yellow
FLs for tanning
FLs for tanning
FLs, LEDs
Pr3+
Gd2O2S
CaTiO3
510
610
Green
Red
CT Scanner
FEDs
Sm3+
Y3Al5O12 (Granat)
620
Red
LASER
Eu2+
SrB4O7
BaMgAl10O17
Sr4Al14O25
368
453
490
UV-A
Blue
Blue-green
FLs for tanning
FLs, PDPs
FLs
Eu3+
Y2O3
YVO4
611
615
Red
Red
FLs
Gd3+
(La,Bi)B3O6
311
UV-B
FLs for medical skin treat.
LaPO4
CeMgAl11O19
(Gd,Ce)MgB5O10
544
544
544
Green
Green
Green
FLs
FLs
FLs
SrSi2N2O2
620
Red
-
Ce3+
Tb3+
Yb2+
Slide 9
Excitation energy
Activator
Excitation source
Electrons
X-rays
147, 172 nm
172 nm
200 – 350 nm
185, 254 nm
370 – 400 nm
370 – 480 nm
Host lattice
Application in
Cathode ray tubes
X-rays intensifier
Plasma screens
Xe-discharge lamps
Hg-high pressure discharge lamps
Hg-low pressure discharge lamps
Emissive LCDs
pcLEDs
Main application areas: lighting, imaging, detection
Slide 10
TV
Fluorescent lamps
LEDs
Tomography
Plasma TVs
Electroluminescent
screens
Slide 11
Function
Application field
Optical brighteners
Paint, paper, clothing, detergent
Copy protection
Banknotes, stamps, credit cards,
certificate, tickets
Product protection
Pharmaceuticals, plastics
Security labeling
Emergency exit lighting, emergency exits
Advertising / visualization
Discharge lamps, logos
Conversion of high-energy radiation or X-ray films, CTs, positron emission
particles
tomography, EUV-amplifier
Cosmetics
Dental ceramics, tanning lamps
Marker for the analysis
Detection of nucleic acids + proteins
Lithographie
Photocopier
Photochemistry and biology
Water purification, disinfection, breeding
boxes and cabinets, air pollution control
Medicine
Diagnostics, photodynamic therapy
Slide 12
7.7 Broadband Phosphors
Examples
• (Zn,Be)2SiO4:Mn
• CaWO4
• MgWO4
• Ca5(PO4)3(F,Cl):Sb,Mn
Emission intensity [a.u.]
Suitable activators
• VO43-, WO42• Sn2+, Sb3+, Bi3+, Pb2+
• Ce3+, Eu2+
• Mn2+
MgWO4
CaWO4
1,0
FWHM
Optical transitions
• Charge-Transfer
• 5s-5p, 6s-6p
• 4f-5d
• 3d-3d
0,8
0,6
0,4
0,2
0,0
300
350
400
450
500
550
600
650
700
750
Wavelength [nm]
Willemite
Scheelite
Wolframite
Apatite
Slide 13
800
7.8 Line Phosphors
Optical transitions
• 4f-4f (Sm3+, Eu3+, Tb3+, Er3+, Dy3+, Tm3+)
• Very low electron-phonon coupling
• Lines or line multiplets
0,6
0,4
0,2
1,0
0,8
1,0
0,6
0,4
0,2
0,0
400
450
500
550
600
650
Wavelength [nm]
LaPO4:Tm
YBO3:Tm
700
750
800
0,0
400
500
600
700
Wavelength [nm]
LaPO4:Ce,Tb
LaMgB5O10;Ce,Tb
LaMgAl11O19:Ce,Tb
800
0,8
0,6
0,4
0,2
0,0
400
500
600
700
Wavelength [nm]
Y2O3:Eu
(Y,Gd)BO3:Eu
YVO4:Eu
Slide 14
800
7.9 UV-A Phosphors
Optical transitions
• 4f-5d
• 6s-6p
Suitable activators
• Eu2+ (>365 nm)
• Ce3+
• Pb2+
Commercial materials
• LaMgAl11O19:Ce
• YPO4:Ce
• BaSi2O5:Pb
• Sr2MgSi2O7:Pb
• SrB4O7:Eu
BaSi2O5:Pb
1,0
SrB4O7:Eu
LaMgAl11O19:Ce
0,8
YPO4:Ce
0,6
Sr2MgSi2O7:Pb
0,4
0,2
0,0
280
300
320
340
360
380
400
420
440
Wavelength [nm]
345 nm
335, 355 nm
350 nm
365 nm
368 nm
Magnetoplumbite
Xenotime
Sanbornit
Akermanite
Slide 15
460
7.10 UV-B Phosphors
Optical transitions
• 4f-5d
• 4f-4f
• 6s-6p
1,0
Suitable activators
• Ce3+
• Bi3+
• Gd3+ (311 nm)
Commercial materials
• SrAl12O19:Ce
• LaB3O6:Bi,Gd
• LaPO4:Ce
0,8
LaB3O6:Bi,Gd
SrAl12O19:Ce
LaPO4:Ce
0,6
0,4
0,2
0,0
260
280
300
320
340
360
380
400
420
Wavelength [nm]
300 nm
311 nm
320 nm
Magnetoplumbite
(Bi3+  Gd3+ energy transfer)
Monazite
Slide 16
440
7.11 UV-C Phosphors
Optical transitions
• 4f-5d
• 6s-6p
1,0
CaSO4:Pb YPO4:Bi
YBO3:Pr
Suitable activators
• Pr3+
• Bi3+
• Pb2+
0,8
0,6
0,4
0,2
0,0
200
250
300
Wavelength [nm]
Examples
• YBO3:Pr
• YAlO3:Pr
• YPO4:Bi
• CaSO4:Pb
265 nm
245 nm
240 nm
230 nm
Vaterite
Perovskite
Xenotime
Anhydrite
Slide 17
350
7.12 IR-A Phosphors
Optical transitions
• 3d-3d
• 4f-4f
1,0
Y3Al5O12:Nd
Suitable activators
• Cr3+
680 – 750 nm
• Fe3+
700 – 800 nm
• Nd3+
~ 1060 nm
• Yb3+
~ 950 - 1050 nm
Examples
• Al2O3:Cr
• LiAlO2:Fe
• Y3Al5O12:Nd
• Y3Al5O12:Yb
694 nm
735 nm
1064 nm
1028 nm
Relative intensity
0,8
0,6
0,4
0,2
0,0
200
400
600
800
1000
Wavelength [nm]
Corundum
Garnet
Garnet
1200
1400
1600
Sample: Y3Al5O12:Nd
→ Ruby laser
→ Fluorescent lamps
→ YAG:Nd-laser
→ YAG:Yb-laser
Slide 18

7. Luminescent Materials

Transcription

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