This book presents a comparison of solar cell materials, including both new materials based on organics, nanostructures and novel inorganics and developments in more traditional photovoltaic materials.
It surveys the materials and materials trends in the field including third generation solar cells (multiple energy level cells, thermal approaches and the modification of the solar spectrum) with an eye firmly on low costs, energy efficiency and the use of abundant non-toxic materials.
Table of Contents:
Series Preface xiii
List of Contributors xv
1 Introduction 1
Gavin Conibeer and Arthur Willoughby
1.1 Introduction 1
1.2 The Sun 1
1.3 Book Outline 3
References 4
2 Fundamental Physical Limits to Photovoltaic Conversion 5
J.F. Guillemoles
2.1 Introduction 5
2.2 Thermodynamic Limits 8
2.2.1 The Sun is the Limit 9
2.2.2 Classical Thermodynamics Analysis of Solar Energy Conversion 10
2.3 Limitations of Classical Devices 12
2.3.1 Detailed Balance and Main Assumptions 13
2.3.2 p-n Junction 14
2.3.3 The Two-Level System Model 17
2.3.4 Multijunctions 19
2.4 Fundamental Limits of Some High-Efficiency Concepts 22
2.4.1 Beyond Unity Quantum Efficiency 23
2.4.2 Beyond Isothermal Conversion: Hot-Carrier Solar Cells (HCSC) 29
2.4.3 Beyond the Single Process/ Photon: Photon Conversion 32
2.5 Conclusion 33
Note 33
References 33
3 Physical Characterisation of Photovoltaic Materials 35
Daniel Bellet and Edith Bellet-Amalric
3.1 Introduction 35
3.2 Correspondence between Photovoltaic Materials Characterisation Needs and Physical Techniques 35
3.3 X-Ray Techniques 36
3.3.1 X-Ray Diffraction (XRD) 37
3.3.2 Grazing-Incidence X-Ray Diffraction (GIXRD) 40
3.3.3 X-Ray Reflectivity (XRR) 42
3.3.4 Other X-Ray Techniques 44
3.4 Electron Microscopy Methods 45
3.4.1 Electron–Specimen Interactions and Scanning Electron Microscopy (SEM) 48
3.4.2 Electron Backscattering Diffraction (EBSD) 49
3.4.3 Transmission Electron Microscopy (TEM) 51
3.4.4 Electron Energy Loss Spectroscopy (EELS) 52
3.5 Spectroscopy Methods 53
3.5.1 X-Ray Photoelectron Spectroscopy (XPS) 53
3.5.2 Secondary Ion Mass Spectrometry (SIMS) 55
3.5.3 Rutherford Backscattering Spectrometry (RBS) 56
3.5.4 Raman Spectroscopy 56
3.5.5 UV-VIS-NIR Spectroscopy 58
3.6 Concluding Remarks and Perspectives 59
Acknowledgements 60
References 60
4 Developments in Crystalline Silicon Solar Cells 65
Martin A. Green
4.1 Introduction 65
4.2 Present Market Overview 66
4.3 Silicon Wafers 67
4.3.1 Standard Process 67
4.3.2 Multicrystalline Silicon Ingots 70
4.3.3 Ribbon Silicon 71
4.4 Cell Processing 73
4.4.1 Screen-Printed Cells 73
4.4.2 Buried-Contact and Laser Doped, Selective-Emitter Solar Cells 76
4.4.3 HIT Cell 77
4.4.4 Rear-Contact Cell 78
4.4.5 PERL Solar Cell 79
4.5 Conclusion 82
Acknowledgements 82
References 82
5 Amorphous and Microcrystalline Silicon Solar Cells 85
R.E.I. Schropp
5.1 Introduction 85
5.2 Deposition Methods 87
5.2.1 Modifications of Direct PECVD Techniques 88
5.2.2 Remote PECVD Techniques 89
5.2.3 Inline HWCVD Deposition 91
5.3 Material Properties 91
5.3.1 Protocrystalline Silicon 92
5.3.2 Microcrystalline or Nanocrystalline Silicon 93
5.4 Single-Junction Cell 96
5.4.1 Amorphous (Protocrystalline) Silicon Cells 98
5.4.2 Microcrystalline (μc-Si:H) Silicon Cells 99
5.4.3 Higher Deposition Rate 101
5.5 Multijunction Cells 102
5.6 Modules and Production 103
Acknowledgments 106
References 106
6 III-V Solar Cells 113
N.J. Ekins-Daukes
6.1 Introduction 113
6.2 Homo- and Heterojunction III-V Solar Cells 115
6.2.1 GaAs Solar Cells 117
6.2.2 InP Solar Cells 120
6.2.3 InGaAsP 121
6.2.4 GaN 121
6.3 Multijunction Solar Cells 122
6.3.1 Monolithic Multijunction Solar Cells 123
6.3.2 Mechanically Stacked Multijunction Solar Cells 129
6.4 Applications 131
6.4.1 III-V Space Photovoltaic Systems 131
6.4.2 III-V Concentrator Photovoltaic Systems 132
6.5 Conclusion 134
References 134
7 Chalcogenide Thin-Film Solar Cells 145
M. Paire, S. Delbos, J. Vidal, N. Naghavi and J.F. Guillemoles
7.1 Introduction 145
7.2 CIGS 148
7.2.1 Device Fabrication 148
7.2.2 Material Properties 162
7.2.3 Device Properties 171
7.2.4 Outlook 181
7.3 Kesterites 185
7.3.1 Advantages of CZTS 185
7.3.2 Crystallographic and Optoelectronic Properties 187
7.3.3 Synthesis Strategies 190
Acknowledgements 196
References 196
8 Printed Organic Solar Cells 217
Claudia Hoth, Andrea Seemann, Roland Steim, Tayebeh Ameri, Hamed Azimi and Christoph J. Brabec
8.1 Introduction 217
8.2 Materials and Morphology 218
8.2.1 Organic Semiconductors 219
8.2.2 Control of Morphology in oBHJ Solar Cells 224
8.2.3 Monitoring Morphology 233
8.2.4 Numerical Simulations of Morphology 235
8.2.5 Alternative Approaches to Control the Morphology 235
8.3 Interfaces in Organic Photovoltaics 237
8.3.1 Origin of Voc 237
8.3.2 Determination of Polarity-Inverted and Noninverted Structure 238
8.3.3 Optical Spacer 239
8.3.4 Protection Layer between the Electrode and the Polymer 240
8.3.5 Selective Contact 240
8.3.6 Interface Material Review for OPV Cells 240
8.4 Tandem Technology 243
8.4.1 Theoretical Considerations 243
8.4.2 Review of Experimental Results 248
8.4.3 Design Rules for Donors in Bulk-Heterojunction Tandem Solar Cells 255
8.5 Electrode Requirements for Organic Solar Cells 257
8.5.1 Materials for Transparent Electrodes 258
8.5.2 Materials for Nontransparent Electrodes 263
8.6 Production of Organic Solar Cells 265
8.7 Summary and Outlook 273
References 273
9 Third-Generation Solar Cells 283
Gavin Conibeer
9.1 Introduction 283
9.2 Multiple-Energy-Level Approaches 285
9.2.1 Tandem Cells 285
9.2.2 Multiple-Exciton Generation (MEG) 291
9.2.3 Intermediate-Band Solar Cells (IBSC) 293
9.3 Modification of the Solar Spectrum 294
9.3.1 Downconversion, QE > 1 294
9.3.2 Upconversion of Below-Bandgap Photons 297
9.4 Thermal Approaches 302
9.4.1 Thermophotovoltaics (TPV) 303
9.4.2 Thermophotonics 303
9.4.3 Hot-Carrier Cells 303
9.5 Other Approaches 308
9.5.1 Nonreciprocal Devices 308
9.5.2 Quantum Antennae – Light as a Wave 308
9.6 Conclusions 309
Acknowledgements 309
References 310
Concluding Remarks 315
Gavin Conibeer and Arthur Willoughby
Index 319
