Foreword ........................................................ V
Preface ...................................................... XIII
List of Contributors ........................................... XV
1. Emission and Excitation Mechanisms of Phosphors .............. 1
Cees R. Ronda
1.1. Introduction ............................................... 1
1.2. General Considerations - Fluorescent Lamps ................. 1
1.3. General Considerations - Cathode Ray Tubes ................. 2
1.4. Luminescence Mechanisms .................................... 3
1.4.1. Center Luminescence ................................. 4
1.4.2. Charge Transfer Luminescence ........................ 8
1.4.3. Donor Acceptor Pair Luminescence .................... 8
1.4.4. Long Afterglow Phosphors ........................... 11
1.5. Excitation Mechanisms ..................................... 12
1.5.1. Optical Excitation of Luminescence and Energy
Transfer ........................................... 12
1.6. Energy Transfer Mechanisms between Optical Centers ........ 14
1.6.1. Mechanisms Underlying Energy Transfer .............. 14
1.6.2. Energy Transfer Governed by Electrostatic
Interaction ........................................ 15
1.6.3. Energy Transfer by Higher-order Coulomb
Interaction ........................................ 18
1.6.4. Energy Transfer Governed by Exchange
Interactions ....................................... 19
1.6.5. Cross-relaxation and Energy Transfer ............... 19
1.6.6. Practical Implications ............................. 20
1.7. Excitation with High-energy Particles ..................... 21
1.8. Electroluminescence (EL) .................................. 24
1.8.1. High-voltage Electroluminescence ................... 24
1.8.2. Low-voltage Electroluminescence .................... 26
1.9. Factors Determining the Emission Color .................... 27
1.10.Energy Efficiency Considerations of Important
Luminescent Devices ....................................... 29
1.11.Luminescence Quantum Yield and Quenching Processes ........ 29
1.11.1. The Energy does not Reach the Luminescent Ion ..... 31
1.11.2. The Absorbed Energy Reaches the Luminescent
Ion but there are Nonradiative Channels to
the Ground State .................................. 31
1.11.3. The Luminescence Generated is Absorbed by the
Luminescent Material .............................. 33
1.12.Acknowledgement ........................................... 34
2. Quantum Dots and Nanophosphors .............................. 35
Cees R. Rondo and Thomas Jüstel
2.1. Introduction .............................................. 35
2.1.1. Optical Properties of Quantum Dots ................. 35
2.1.2. Particle in a One-dimensional Potential Well ....... 36
2.1.3. Particle in Three-dimensional Potentials ........... 40
2.1.3.1. Particle in a General Three-dimensional
Potential ................................. 40
2.1.3.2. Electron in a Coulomb Potential ........... 41
2.1.3.3. The Hydrogen Atom ......................... 42
2.2. Density of States in Low-dimensional Structures ........... 43
2.3. Electrons, Holes, and Excitons ............................ 45
2.4. Low-dimensional Structures ................................ 46
2.4.1. The Weak Confinement Regime ........................ 46
2.4.2. The Strong Confinement Regime ...................... 47
2.5. Quantum Confinement in Action ............................. 49
2.6. Photoluminescence of Quantum Dots Prepared by Wet-
chemical Precipitation .................................... 52
2.7. Photoluminescence from Doped Quantum Dots ................. 53
2.8. Luminescence of Nano Particles of Rare-Earth Phosphors .... 55
2.9. Nanoscale Particles for Molecular Imaging ................. 56
2.10.Conclusions ............................................... 58
2.11.Acknowledgements .......................................... 58
3. Phosphors for Plasma Display Panels ......................... 61
Thomas Jüstel
3.1. Introduction .............................................. 61
3.2. Principle of Operation of Plasma Display Panels ........... 61
3.3. Performance of Applied Phosphors in PDPs .................. 65
3.3.1. Phosphor Efficiency ................................ 66
3.3.2. Electronic Transitions Involved in Europium
Luminescence ....................................... 68
3.3.3. Color point and efficiency of the red phosphors .... 68
3.3.4. Stability and Color Point of BaMgAl10O17:Eu ......... 70
3.4. Summary and Prospects ..................................... 72
4. Quantum-Splitting Systems ................................... 75
Alok M. Srivastava and Cees R. Ronda
4.1. Introduction .............................................. 75
4.2. Quantum-splitting Phosphors Based on Pr3+-activated
Fluoride Materials ........................................ 76
4.3. Quantum-splitting Phosphors Based on Pr3+-activated
Oxide Materials ........................................... 82
4.3.1. SrAl12O19: Pr3+ ...................................... 83
4.3.1.1. LaMgB5O10 and LaB3O6 Doped with Pr3+ ........ 85
4.4. The Quantum Efficiency of the Quantum-splitting Process ... 88
4.5. Limitations of Pr3+-based Quantum-splitting Phosphors ...... 91
4.6. Quantum-splitting Phosphors Based on Gd3+ and Rare
Earth Ion-Activated Fluoride Materials .................... 92
4.6.1. The Electronic Energy Level Structure of the
Gd3+Ion ............................................. 92
4.6.2. Quantum Splitting in the Gd3+-Eu3+ System ........... 94
4.6.3. Quantum Splitting in the Er3+-Gd3+-Tb3+ System ....... 97
4.7. Multiphoton Emission through High-energy Excitation ....... 98
4.8. Applications of Quantum-splitting Phosphors ............... 99
4.9. Conclusions .............................................. 100
4.10.Acknowledgements ......................................... 101
5. Scintillators .............................................. 205
Cees R. Ronda and Alok M. Srivastava
5.1. Introduction ............................................. 105
5.2. Positron Emission Tomography and Computed Tomography ..... 106
5.2.1. Physical Principles of Positron Emission
Tomography (PET) .................................. 106
5.2.2. Computed Tomography (CT) .......................... 107
5.3. General Requirements for Scintillating Materials used
in Medical Imaging ....................................... 107
5.4. Scintillators for Pet Application ........................ 112
5.4.1. General Description of Phosphors for PET
Scintillators ..................................... 112
5.4.2. Scintillating Composition Used in PET ............. 114
5.4.2.1. Bi4Ge3012 (BGO) .......................... 115
5.4.2.2. NaI:Tl+ .................................. 116
5.4.2.3. Lu2SiO5:Ce3+ (LSO) ....................... 116
5.4.2.4. Lu2Si2O7:Ce (Lutetium Pyrosilicate,
LPS) ..................................... 117
5.4.2.5. LaBr3:Ce ................................. 118
5.4.2.6. LuI3:Ce .................................. 119
5.4.3. Other PET Scintillators ........................... 119
5.5. Scintillators for CT Application ......................... 120
5.5.1. General Description of Scintillators for CT ....... 120
5.5.2. Scintillating Compositions Used in CT ............. 120
5.5.2.1. CdWO4 .................................... 120
5.5.2.2. (Y,Gd)203:Eu3+ ............................ 121
5.5.2.3. Gd202S:Pr3+ (GOS) ......................... 122
5.6. X-ray Intensifying Screens ............................... 123
5.6.1. General Description of Scintillators for
Intensifying Screens .............................. 123
5.6.2. Phosphor Compositions for Use in X-ray
Intensifying Screens .............................. 123
5.7. FDXD Detectors ........................................... 124
5.8. Storage Phosphors ........................................ 124
5.8.1. General Description of Storage Phosphors .......... 124
5.9. Semiconductor Scintillators .............................. 127
6. Upconversion Phosphors ..................................... 133
J. Freek Suijver
6.1. Introduction ............................................. 133
6.2. Theory of Upconversion ................................... 137
6.2.1. Absorption and Excitation Spectroscopy ............ 139
6.2.2. Time Evolution of UC Emission ..................... 143
6.2.3. Power Dependence of Upconversion .................. 146
6.2.4. Photon Avalanche Effects in Upconversion .......... 150
6.2.5. Determination of the Upconversion Efficiency ...... 153
6.3. Examples ................................................. 154
6.3.1. Rare Earth Upconverters ........................... 155
6.3.2. Transition Metal Upconverters ..................... 162
6.3.3. Mixed Rare Earth/Transition Metal Upconverters .... 165
6.3.4. Organic Upconverters .............................. 169
6.3.5. Nanocrystalline Upconverters ...................... 171
6.4. Conclusions and Outlook .................................. 175
6.5. Acknowledgements ......................................... 276
7. Luminescent Materials for Phosphor-Converted LEDs .......... 179
Thomas Jüstel
7.1. Inorganic Light-Emitting Diodes (LEDs) ................... 179
7.2. White and Colored LEDs ................................... 180
7.3. Phosphor-Converted LEDs .................................. 183
7.4. Future Trends ............................................ 188
8. Organic Electroluminescence ................................ 191
Joseph J. Shiang and Anil R. Duggal
8.1. Introduction ............................................. 191
8.2. OLED Fundamentals ........................................ 192
8.3. Key OLED Trends and Innovations .......................... 197
8.3.1. Electroluminescence from Vapor-deposited
Organic Films ..................................... 197
8.3.2. Electroluminescence from Solution-Deposited
Organic Films ..................................... 202
8.4. Prospects for General Illumination ....................... 207
8.4.1. A First OLED Lighting Demonstration ............... 208
8.4.1.1. Downconversion for White Light
Generation ............................... 209
8.4.1.2. Scattering for Outcoupling Efficiency
Enhancement .............................. 210
8.4.1.3. A Scalable Monolithic Series
Architecture ............................. 211
8.4.2. Efficiency Challenge for General Illumination ..... 212
8.5. Conclusions .............................................. 213
8.6. Acknowledgements ......................................... 214
9. Experimental Techniques .................................... 219
Peter Vergeer
9.1. Introduction ............................................. 219
9.2. Energy of Optical Transitions: Absorption, Excitation,
and Emission Spectroscopy ................................ 220
9.2.1. Broadband Light Sources ........................... 223
9.2.2. Dispersing Elements ............................... 224
9.2.2.1. Gratings ................................. 224
9.2.2.2. Interferometers .......................... 227
9.2.3. Detectors ......................................... 229
9.3. The Transition Dipole Moment: Absorption Strengths and
Luminescence Lifetimes ................................... 233
9.3.1. Lasers ............................................ 235
9.3.2. Luminescence Lifetimes ............................ 237
9.4. Quantum Efficiency and Nonradiative Relaxation ........... 238
9.5. Homogeneous Broadening and Dephasing ..................... 240
9.6. Detection of Luminescence from Individual Optical
Centers .................................................. 244
9.7. Acknowledgement .......................................... 248
Index ......................................................... 251
|
