Solar Cell Device Physics » (2nd Edition)

There has been an enormous infusion of new ideas in the field of solar cells over the last 15 years; discourse on energy transfer has gotten much richer, and nanostructures and nanomaterials have revolutionized the possibilities for new technological developments. However, solar energy cannot become ubiquitous in the world's power markets unless it can become economically competitive with legacy generation methods such as fossil fuels.

The new edition of Dr. Stephen Fonash's definitive text points the way toward greater efficiency and cheaper production by adding coverage of cutting-edge topics in plasmonics, multi-exiton generation processes, nanostructures and nanomaterials such as quantum dots. The book's new structure improves readability by shifting many detailed equations to appendices, and balances the first edition's semiconductor coverage with an emphasis on thin-films. Further, it now demonstrates physical principles with simulations in the well-known AMPS computer code developed by the author.

*Classic text now updated with new advances in nanomaterials and thin films that point the way to cheaper, more efficient solar energy production

*Many of the detailed equations from the first edition have been shifted to appendices in order to improve readability

*Important theoretical points are now accompanied by concrete demonstrations via included simulations created with the well-known AMPS computer code

Preface xi

Acknowledgments xiii

List of Symbols xv

List of Abbreviations xxvii

1 Introduction 1

1.1 Photovoltaic Energy Conversion 1

1.2 Solar Cells and Solar Energy Conversion 2

1.3 Solar Cell Applications 7

References 8

2 Material Properties and Device Physics Basic to Photovoltaics 9

2.1 Introduction 9

2.2 Material Properties 10

2.2.1 Structure of solids 10

2.2.2 Phonon spectra of solids 13

2.2.3 Electron energy levels in solids 18

2.2.4 Optical phenomena in solids 28

2.2.5 Carrier recombination and trapping 36

2.2.6 Photocarrier generation 45

2.3 Transport 46

2.3.1 Transport processes in bulk solids 46

2.3.2 Transport processes at interfaces 53

2.3.3 Continuity concept 58

2.3.4 Electrostatics 60

2.4 The Mathematical System 60

2.5 Origins of Photovoltaic Action 63

References 64

3 Structures, Materials, and Scale 67

3.1 Introduction 67

3.2 Basic Structures for Photovoltaic Action 69

3.2.1 General comments on band diagrams 69

3.2.2 Photovoltaic action arising from built-in electrostatic fields 73

3.2.3 Photovoltaic action arising from diffusion 83

3.2.4 Photovoltaic action arising from effective fields 85

3.2.5 Summary of practical structures 92

3.3 Key Materials 95

3.3.1 Absorber materials 95

3.3.2 Contact materials 102

3.4 Length Scale Effects for Materials and Structures 107

3.4.1 The role of scale in absorption and collection 107

3.4.2 Using the nano-scale to capture lost energy 115

3.4.3 The role of scale in light management 116

References 117

4 Homojunction Solar Cells 121

4.1 Introduction 121

4.2 Overview of Homojunction Solar Cell Device Physics 124

4.2.1 Transport 124

4.2.2 The homojunction barrier region 131

4.3 Analysis of Homojunction Device Physics: Numerical Approach 132

4.3.1 Basic p-n homojunction 133

4.3.2 Addition of a front HT-EBL 141

4.3.3 Addition of a front HT-EBL and back ET-HBL 145

4.3.4 Addition of a front high-low junction 149

4.3.5 A p-i-n cell with a front HT-EBL and back ET-HBL 154

4.3.6 A p-i-n cell using a poor μτ absorber 155

4.4 Analysis of Homojunction Device Physics: Analytical Approach 166

4.4.1 Basic p-n homojunction 167

4.5 Some Homojunction Configurations 179

References 181

5 Semiconductor-semiconductor Heterojunction Cells 183

5.1 Introduction 183

5.2 Overview of Heterojunction Solar Cell Device Physics 189

5.2.1 Transport 189

5.2.2 The heterojunction barrier region 193

5.3 Analysis of Heterojunction Device Physics: Numerical Approach 202

5.3.1 Absorption by free electron-hole pair excitations 203

5.3.2 Absorption by exciton generation 237

5.4 Analysis of Heterojunction Device Physics: Analytical Approach 247

5.4.1 Absorption by free electron-hole excitations 247

5.4.2 Absorption by excitons 259

5.5 Some Heterojunction Configurations 259

References 261

6 Surface-barrier Solar Cells 263

6.1 Introduction 263

6.2 Overview of Surface-barrier Solar Cell Device Physics 268

6.2.1 Transport 268

6.2.2 The surface-barrier region 271

6.3 Analysis of Surface-barrier Device Physics: Numerical Approach 273

6.4 Analysis of Surface-barrier Device Physics: Analytical Approach 283

6.5 Some Surface-barrier Configurations 291

References 293

7 Dye-sensitized Solar Cells 295

7.1 Introduction 295

7.2 Overview of Dye-sensitized Solar Cell Device Physics 297

7.2.1 Transport 297

7.2.2 The dye-sensitized solar cell barrier region 300

7.3 Analysis of DSSC Device Physics: Numerical Approach 301

7.4 Some DSSC Configurations 307

References 308

Appendix A The Absorption Coefficient 311

Appendix B Radiative Recombination 313

Appendix C Shockley-Read-Hall (Gap-state-assisted) Recombination 317

Appendix D Conduction- and Valence-band Transport 325

Appendix E The Quasi-neutral-region Assumption and Lifetime Semiconductors 335

Appendix F Determining p(x) and n(x) for the Space-charge-neutral Regions of a Homojunction 339

Appendix G Determining n(x) for the Space-charge-neutral Region of a Heterojunction p-type Bottom Material 343

Index 347