Optical Properties of Materials and Their Applications

Edited by Jai Singh, AM, PhD, College of Engineering, IT and Environment, Charles Darwin University, Darwin, Australia. Series Editors Arthur Willoughby University of Southampton, Southampton, UK Peter Capper formerly of Ex-Leonardo M. W. Ltd, Southampton, UK Safa Kasap University of Saskatchewan, Saskatoon, Canada

List of Contributors xv

Series Preface xvii

Preface xix

1 Fundamental Optical Properties of Materials I 1
S.O. Kasap, W.C. Tan, Jai Singh, and Asim K. Ray

1.1 Introduction 1

1.2 Optical Constants n and K 2

1.2.1 Refractive Index and Extinction Coefficient 2

1.2.2 n and K, and Kramers–Kronig Relations 5

1.3 Refractive Index and Dispersion 7

1.3.1 Cauchy Dispersion Relation 7

1.3.2 Sellmeier Equation 8

1.3.3 Refractive Index of Semiconductors 10

1.3.3.1 Refractive Index of Crystalline Semiconductors 10

1.3.3.2 Bandgap and Temperature Dependence 11

1.3.4 Refractive Index of Glasses 11

1.3.5 Wemple–DiDomenico Dispersion Relation 14

1.3.6 Group Index 15

1.4 The Swanepoel Technique: Measurement of n and 𝛼 for Thin Films on Substrates 16

1.4.1 Uniform Thickness Films 16

1.4.2 Thin Films with Non-uniform Thickness 22

1.5 Transmittance and Reflectance of a Partially Transparent Plate 25

1.6 Optical Properties and Diffuse Reflection: Schuster–Kubelka–Munk Theory 27

1.7 Conclusions 31

Acknowledgments 31

References 32

2 Fundamental Optical Properties of Materials II 37
S.O. Kasap, K. Koughia, Jai Singh, Harry E. Ruda, and Asim K. Ray

2.1 Introduction 37

2.2 Lattice or Reststrahlen Absorption and Infrared Reflection 40

2.3 Free Carrier Absorption (FCA) 42

2.4 Band-to-Band or Fundamental Absorption (Crystalline Solids) 45

2.5 Impurity Absorption and Rare-Earth Ions 48

2.6 Effect of External Fields 54

2.6.1 Electro-Optic Effects 54

2.6.2 Electro-Absorption and Franz–Keldysh Effect 55

2.6.3 Faraday Effect 56

2.7 Effective Medium Approximations 58

2.8 Conclusions 61

Acknowledgments 61

References 62

3 Optical Properties of Disordered Condensed Matter 67
Koichi Shimakawa, Jai Singh, and S.K. O’Leary

3.1 Introduction 67

3.2 Fundamental Optical Absorption (Experimental) 69

3.2.1 Amorphous Chalcogenides 69

3.2.2 Hydrogenated Nano-Crystalline Silicon (nc-Si:H) 72

3.3 Absorption Coefficient (Theory) 74

3.4 Compositional Variation of the Optical Bandgap 79

3.4.1 In Amorphous Chalcogenides 79

3.5 Conclusions 80

References 80

4 Optical Properties of Glasses 83
Andrew Edgar

4.1 Introduction 83

4.2 The Refractive Index 84

4.3 Glass Interfaces 86

4.4 Dispersion 88

4.5 Sensitivity of the Refractive Index 90

4.5.1 Temperature Dependence 90

4.5.2 Stress Dependence 91

4.5.3 Magnetic Field Dependence—The Faraday Effect 92

4.5.4 Chemical Perturbations—Molar Refractivity 94

4.6 Glass Color 95

4.6.1 Coloration by Colloidal Metals and Semiconductors 95

4.6.2 Optical Absorption in Rare-Earth-Doped Glass 96

4.6.3 Absorption by 3d Metal Ions 99

4.7 Fluorescence in Rare-Earth-Doped Glass 102

4.8 Glasses for Fiber Optics 104

4.9 Refractive Index Engineering 106

4.10 Glass and Glass–Fiber Lasers and Amplifiers 109

4.11 Valence Change Glasses 111

4.12 Transparent Glass Ceramics 114

4.12.1 Introduction 114

4.12.2 Theoretical Basis for Transparency 116

4.12.3 Rare-Earth-Doped Transparent Glass Ceramics for Active Photonics 120

4.12.4 Ferroelectric Transparent Glass Ceramics 121

4.12.5 Transparent Glass Ceramics for X-ray Storage Phosphors 121

4.13 Conclusions 124

References 124

5 Concept of Excitons 129
Jai Singh, Harry E. Ruda, M.R. Narayan, and D. Ompong

5.1 Introduction 129

5.2 Excitons in Crystalline Solids 130

5.2.1 Excitonic Absorption in Crystalline Solids 133

5.3 Excitons in Amorphous Semiconductors 135

5.3.1 Excitonic Absorption in Amorphous Solids 137

5.4 Excitons in Organic Semiconductors 139

5.4.1 Photoexcitation and Formation of Excitons 140

5.4.1.1 Photoexcitation of Singlet Excitons Due to Exciton–Photon Interaction 141

5.4.1.2 Excitation of Triplet Excitons 142

5.4.2 Exciton Up-Conversion 147

5.4.3 Exciton Dissociation 148

5.4.3.1 Conversion from Frenkel to CT Excitons 151

5.4.3.2 Dissociation of CT Excitons 152

5.5 Conclusions 153

References 154

6 Photoluminescence 157
Takeshi Aoki

6.1 Introduction 157

6.2 Fundamental Aspects of Photoluminescence (PL) in Materials 158

6.2.1 Intrinsic Photoluminescence 159

6.2.2 Extrinsic Photoluminescence 160

6.2.3 Up-Conversion Photoluminescence (UCPL) 162

6.2.4 Other Related Optical Transitions 163

6.3 Experimental Aspects 164

6.3.1 Static PL Spectroscopy 164

6.3.2 Photoluminescence Excitation Spectroscopy (PLE) and Photoluminescence Absorption Spectroscopy (PLAS) 167

6.3.3 Time Resolved Spectroscopy (TRS) 168

6.3.4 Time-Correlated Single Photon Counting (TCSPC) 171

6.3.5 Frequency-Resolved Spectroscopy (FRS) 172

6.3.6 Quadrature Frequency Resolved Spectroscopy (QFRS) 173

6.4 Photoluminescence Lifetime Spectroscopy of Amorphous Semiconductors by QFRS Technique 175

6.4.1 Overview 175

6.4.2 Dual-Phase Double Lock-in (DPDL) QFRS Technique 176

6.4.3 Exploring Broad PL Lifetime Distribution in a-Si:H by Wideband QFRS 178

6.4.3.1 Effects of Excitation Intensity, Excitation, and Emission Energies 179

6.4.3.2 Temperature Dependence 184

6.4.3.3 Effect of Electric and Magnetic Fields 185

6.4.4 Residual PL Decay of a-Si:H 189

6.5 QFRS on Up-Conversion Photoluminescence (UCPL) of RE-Doped Materials 192

6.6 Conclusions 197

Acknowledgments 198

References 198

7 Photoluminescence, Photoinduced Changes, and Electroluminescence in Noncrystalline Semiconductors 203
Jai Singh

7.1 Introduction 203

7.2 Photoluminescence 205

7.2.1 Radiative Recombination Operator and Transition Matrix Element 206

7.2.2 Rates of Spontaneous Emission 211

7.2.2.1 At Nonthermal Equilibrium 212

7.2.2.2 At Thermal Equilibrium 214

7.2.2.3 Determining E0 215

7.2.3 Results of Spontaneous Emission and Radiative Lifetime 216

7.2.4 Temperature Dependence of PL 222

7.2.5 Excitonic Concept 223

7.3 Photoinduced Changes in Amorphous Chalcogenides 225

7.3.1 Effect of Photo-Excitation and Phonon Interaction 226

7.3.2 Excitation of a Single Electron–Hole Pair 228

7.3.3 Pairing of Like Excited Charge Carriers 229

7.4 Radiative Recombination of Excitons in Organic Semiconductors 232

7.4.1 Rate of Fluorescence 233

7.4.2 Rate of Phosphorescence 233

7.4.3 Organic Light Emitting Diodes (OLEDs) 234

7.4.3.1 Second- and Third-Generation OLEDs: TADF 235

7.5 Conclusions 236

Acknowledgments 236

References 237

8 Photoinduced Bond Breaking and Volume Change in Chalcogenide Glasses 241
Sandor Kugler, Rozália Lukács, and Koichi Shimakawa

8.1 Introduction 241

8.2 Atomic-Scale Computer Simulations of Photoinduced Volume Changes 243

8.3 Effect of Illumination 244

8.4 Kinetics of Volume Change 245

8.4.1 a-Se 245

8.4.2 a-As2Se3 246

8.5 Additional Remarks 248

8.6 Conclusions 249

References 249

9 Properties and Applications of Photonic Crystals 251
Harry E. Ruda and Naomi Matsuura

9.1 Introduction 251

9.2 PC Overview 252

9.2.1 Introduction to PCs 252

9.2.2 Nanoengineering of PC Architectures 253

9.2.3 Materials Selection for PCs 255

9.3 Tunable PCs 255

9.3.1 Tuning PC Response by Changing the Refractive Index of Constituent Materials 256

9.3.1.1 PC Refractive Index Tuning Using Light 256

9.3.1.2 PC Refractive Index Tuning Using an Applied Electric Field 256

9.3.1.3 Refractive Index Tuning of Infiltrated PCs 257

9.3.1.4 PC Refractive Index Tuning by Altering the Concentration of Free Carriers (Using Electric Field or Temperature) in Semiconductor-Based PCs 257

9.3.2 Tuning PC Response by Altering the Physical Structure of the PC 258

9.3.2.1 Tuning PC Response Using Temperature 258

9.3.2.2 Tuning PC Response Using Magnetism 258

9.3.2.3 Tuning PC Response Using Strain 258

9.3.2.4 Tuning PC Response Using Piezoelectric Effects 259

9.3.2.5 Tuning PC Response Using MEMS Actuation 260

9.4 Selected Applications of PC 260

9.4.1 Waveguide Devices 261

9.4.2 Dispersive Devices 262

9.4.3 Add/Drop Multiplexing Devices 262

9.4.4 Applications of PCs for Light-Emitting Diodes (LEDs) and Lasers 263

9.5 Conclusions 265

Acknowledgments 265

References 265

10 Nonlinear Optical Properties of Photonic Glasses 269
Keiji Tanaka

10.1 Introduction 269

10.2 Photonic Glass 271

10.3 Nonlinear Absorption and Refractivity 272

10.3.1 Fundamentals 272

10.3.2 Two-Photon Absorption 275

10.3.3 Nonlinear Refractivity 278

10.4 Nonlinear Excitation-Induced Structural Changes 280

10.4.1 Fundamentals 280

10.4.2 Oxides 281

10.4.3 Chalcogenides 283

10.5 Conclusions 285

10.A Addendum: Perspectives on Optical Devices 286

References 288

11 Optical Properties of Organic Semiconductors 295
Takashi Kobayashi and Hiroyoshi Naito

11.1 Introduction 295

11.2 Molecular Structure of π-Conjugated Polymers 296

11.3 Theoretical Models 298

11.4 Absorption Spectrum 300

11.5 Photoluminescence 304

11.6 Non-Emissive Excited States 306

11.7 Electron–Electron Interaction 309

11.8 Interchain Interaction 314

11.9 Conclusions 320

References 321

12 Organic Semiconductors and Applications 323
Furong Zhu

12.1 Introduction 323

12.1.1 Device Architecture and Operation Principle 324

12.1.2 Technical Challenges and Process Integration 325

12.2 Anode Modification for Enhanced OLED Performance 327

12.2.1 Low-Temperature High-Performance ITO 327

12.2.1.1 Experimental Methods 328

12.2.1.2 Morphological Properties 329

12.2.1.3 Electrical Properties 331

12.2.1.4 Optical Properties 333

12.2.1.5 Compositional Analysis 336

12.2.2 Anode Modification 339

12.2.3 Electroluminescence Performance of OLEDs 340

12.3 Flexible OLEDs 345

12.3.1 Flexible OLEDs on Ultrathin Glass Substrate 346

12.3.2 Flexible Top-Emitting OLEDs on Plastic Foils 347

12.3.2.1 Top-Emitting OLEDs 348

12.3.2.2 Flexible TOLEDs on Plastic Foils 350

12.4 Solution-Processable High-Performing OLEDs 353

12.4.1 Performance of OLEDs with a Hybrid MoO3-PEDOT:PSS Hole Injection Layer (HIL) 353

12.4.2 Morphological Properties of the MoO3-PEDOT:PSS HIL 361

12.4.3 Surface Electronic Properties of MoO3-PEDOT:PSS HIL 363

12.5 Conclusions 368

References 369

13 Transparent White OLEDs 373
Choi Wing Hong and Furong Zhu

13.1 Introduction—Progress in Transparent WOLEDs 373

13.2 Performance of WOLEDs 374

13.2.1 Optimization of Dichromatic WOLEDs 374

13.2.2 J-L-V Characteristics of WOLEDs 377

13.2.3 Electron-Hole Current Balance in Transparent WOLEDs 384

13.3 Emission Behavior of Transparent WOLEDs 386

13.3.1 Visible-Light Transparency of WOLEDs 386

13.3.2 L-J Characteristics of Transparent WOLEDs 390

13.3.3 Angular-Dependent Color Stability of Transparent WOLEDs 395

13.4 Conclusions 400

References 400

14 Optical Properties of Thin Films 403
V.-V. Truong, S. Tanemura, A. Haché, and L. Miao

14.1 Introduction 403

14.2 Optics of Thin Films 404

14.2.1 An Isotropic Film on a Substrate 404

14.2.2 Matrix Methods for Multi-Layered Structures 406

14.2.3 Anisotropic Films 407

14.3 Reflection-Transmission Photoellipsometry for Determination of Optical Constants 408

14.3.1 Photoellipsometry of a Thick or a Thin Film 408

14.3.2 Photoellipsometry for a Stack of Thick and Thin Films 410

14.3.3 Remarks on the Reflection-Transmission Photoellipsometry Method 412

14.4 Application of Thin Films to Energy Management and Renewable-Energy Technologies 412

14.4.1 Electrochromic Thin Films 413

14.4.2 Pure and Metal-Doped VO2 Thermochromic Thin Films 414

14.4.3 Temperature-Stabilized V1-xWxO2 Sky Radiator Films 417

14.4.4 Optical Functional TiO2 Thin Film for Environmentally Friendly Technologies 420

14.5 Application of Tunable Thin Films to Phase and Polarization Modulation 424

14.6 Conclusions 430

References 430

15 Optical Characterization of Materials by Spectroscopic Ellipsometry 435
J. Mistrík

15.1 Introduction 435

15.2 Notions of Light Polarization 436

15.3 Measureable Quantities 438

15.4 Instrumentation 441

15.5 Single Interface 442

15.6 Single Layer 448

15.7 Multilayer 454

15.8 Linear Grating 458

15.9 Conclusions 462

Acknowledgments 463

References 463

16 Excitonic Processes in Quantum Wells 465
Jai Singh and I.-K. Oh

16.1 Introduction 465

16.2 Exciton–Phonon Interaction 466

16.3 Exciton Formation in QWs Assisted by Phonons 467

16.4 Nonradiative Relaxation of Free Excitons 474

16.4.1 Intraband Processes 475

16.4.2 Interband Processes 479

16.5 Quasi-2D Free-Exciton Linewidth 485

16.6 Localization of Free Excitons 491

16.7 Conclusions 499

References 500

17 Optoelectronic Properties and Applications of Quantum Dots 503
Jørn M. Hvam

17.1 Introduction 503

17.2 Epitaxial Growth and Structure of Quantum Dots 504

17.2.1 Self-Assembled Quantum Dots 504

17.2.2 Site-Controlled Growth on Patterned Substrates 505

17.2.3 Natural or Interface Quantum Dots 506

17.2.4 Quantum Dots in Nanowires 507

17.3 Excitons in Quantum Dots 508

17.3.1 Quantum-Dot Bandgap 509

17.3.2 Optical Transitions 510

17.4 Optical Properties 513

17.4.1 Radiative Lifetime, Oscillator Strength, and Internal Quantum Efficiency 514

17.4.2 Linewidth, Coherence, and Dephasing 516

17.4.3 Transient Four-Wave Mixing 517

17.5 Quantum Dot Applications 520

17.5.1 Quantum Dot Lasers and Optical Amplifiers 520

17.5.1.1 Gain Dynamics 522

17.5.1.2 Homogeneous Broadening and Dephasing 524

17.5.1.3 Long-Wavelength Lasers 526

17.5.1.4 Nano Lasers 527

17.5.2 Single-Photon Emitters 527

17.5.2.1 Micropillars and Nanowires 530

17.5.2.2 Photonic Crystal Waveguide 531

17.6 Conclusions 533

Acknowledgments 534

References 534

18 Perovskites – Revisiting the Venerable ABX3 Family with Organic Flexibility and New Applications 537
Junwei Xu, D.L. Carroll, K. Biswas, F. Moretti, S. Gridin, and R.T.Williams

18.1 Introduction 537

18.1.1 Review 537

18.1.2 The Structures 538

18.1.2.1 Simple Cubic Frameworks 538

18.1.2.2 The Multiplicity of Hybrids 539

18.1.2.3 Structural Variation 540

18.2 Hybrid Perovskites in Photovoltaics 544

18.2.1 Review 544

18.2.2 The Phenomena Characterized as “Defect Tolerance” 548

18.3 Light-Emitting Diodes Using Solution-Processed Lead Halide Perovskites 549

18.3.1 Review 549

18.3.2 Construction and Characterization of LEDs Utilizing CsPbBr3 Nano-Inclusions in Cs4PbBr6 as the Electroluminescent Medium 553

18.4 Ionizing Radiation Detectors Using Lead Halide Perovskite Materials: Basics, Progress, and Prospects 562

18.5 Conclusions 582

Acknowledgments 583

References 583

19 Optical Properties and Spin Dynamics of Diluted Magnetic Semiconductor Nanostructures 589
Akihiro Murayama and Yasuo Oka

19.1 Introduction 589

19.2 Quantum Wells 591

19.2.1 Spin Injection 591

19.2.2 Study of Spin Dynamics by Pump-Probe Spectroscopy 594

19.3 Fabrication of Nanostructures by Electron-Beam Lithography 596

19.4 Self-Assembled Quantum Dots 599

19.5 Hybrid Nanostructures with Ferromagnetic Materials 604

19.6 Conclusions 607

Acknowledgments 608

References 609

20 Kinetics of the Persistent Photoconductivity in Crystalline III-V Semiconductors 611
Ruben Jeronimo Freitas and Koichi Shimakawa

20.1 Introduction 611

20.2 A Review of PPC in III-V Semiconductors 613

20.3 Key Physical Terms Related to PPC 615

20.3.1 Dispersive Reaction 615

20.3.2 SEF and Power Law 616

20.3.3 Waiting Time Distribution 617

20.4 Kinetics of PPC in III-V Semiconductors 617

20.5 Conclusions 623

Acknowledgments 623

20.A On the Reaction Rate Under the Uniform Distribution 623

References 625

Index 627