Photon Management in Solar Cells

Written by renowned experts in the field of photon management in solar cells, this one-stop reference gives an introduction to the physics of light management in solar cells, and discusses the different concepts and methods of applying photon management.
The authors cover the physics, principles, concepts, technologies, and methods used, explaining how to increase the efficiency of solar cells by splitting or modifying the solar spectrum before they absorb the sunlight. In so doing, they present novel concepts and materials allowing for the cheaper, more flexible manufacture of solar cells and systems.
For educational purposes, the authors have split the reasons for photon management into spatial and spectral light management.
Bridging the gap between the photonics and the photovoltaics communities, this is an invaluable reference for materials scientists, physicists in industry, experimental physicists, lecturers in physics, Ph.D. students in physics and material sciences, engineers in power technology, applied and surface physicists.

Auteur

Ralf B. Wehrspohn studied physics at the University of Oldenburg, Germany, and received his PhD degree from the Ecole Polytechnique in Paris in 1997. Until 1999 he worked on thin-fi lm transistors for AMLCDs at Philips Research. From 1999 until 2003 he led the Porous Materials/Photonic Crystals group at the Max
Planck Institute of Microstructure Physics in Halle, after which he held a chair at the Physics department of the University of Paderborn for three years. Since 2006, he has been the director of the Fraunhofer-Institute for Mechanics of Materials and a Professor of Physics at the Martin-Luther-University Halle-Wittenberg. Professor Wehrspohn was awarded the Maier-Leibnitz Prize of the German Science Foundation in 2003.

Uwe Rau studied physics at the University of Tübingen, Germany, and at the University Claude Bernard, Lyon, France. He obtained his PhD 1991 from the Physical Institute of the University Tübingen. From 1991-1993 he worked at the Max Planck Institute for Solid-State Research. He was scientifi c group leader from 1993-2007 at the University Bayreuth and at the University Stuttgart. Since 2007 he is full professor at RWTH Aachen (Faculty Electrical Engineering and Information Technology, Chair of Photovoltaics). Simultaneously he is director of the Institute of Energy and Climate Research IEK5-Photovoltaics at Forschungszentrum Jülich).

Andreas Gombert studied photo engineering and optics in Cologne, Germany, and Strasbourg, France, and received his PhD from the University Louis Pasteur, Strasbourg. His professional career started in 1986 at the Fraunhofer Institute for Physical Measurement Techniques in the fi eld of integrated optics. From 1991
to 2008, he worked at the Fraunhofer Institute for Solar Energy Systems where headed the department Materials Research and Applied Optics. Since 2008 he is Vice President System Platform and R&D and since 2014 also Managing Director of Soitec Solar GmbH, Freiburg, Germany, a division of the Soitec Group. He lectures at Technical Faculty of the University of Freiburg, Germany where he also habilitated.

Contenu

Preface XIII

List of Contributors XV

1 Current Concepts for Optical Path Enhancement in Solar Cells 1
Alexander N. Sprafke and Ralf B. Wehrspohn

1.1 Introduction 1

1.2 Planar Antireflection Coatings 2

1.3 Optical Path Enhancement in the Ray Optical Limit 4

1.4 Scattering Structures for Optical Path Enhancement 5

1.5 Resonant Structures for Optical Path Enhancement 7

1.6 Ultra-Light Trapping 10

1.7 Energy-Selective Structures as Intermediate Reflectors for Optical Path Enhancement in Tandem Solar Cells 13

1.8 Comparison of the Concepts 16

1.9 Conclusion 17

References 17

2 The Principle of Detailed Balance and the Opto-Electronic Properties of Solar Cells 21
Uwe Rau and Thomas Kirchartz

2.1 Introduction 21

2.2 Opto-Electronic Reciprocity 21

2.2.1 The Principle of Detailed Balance 21

2.2.2 The Shockley-Queisser Limit 22

2.2.3 Derivation of the Reciprocity Theorem 24

2.3 Connection to Other Reciprocity Theorems 29

2.3.1 Emitter and Collector Currents in Transistors 29

2.3.2 Tellegens's NetworkTheorem 30

2.3.3 Differential Reciprocity Relations byWong and Green 31

2.3.4 Würfel's Generalization of Kirchhoff's Law 33

2.3.5 Reciprocity Relation for LED Quantum Efficiency 33

2.3.6 Shockley-Queisser Revisited 34

2.3.7 Influence of Light Trapping 35

2.4 Applications of the Opto-Electronic Reciprocity Theorem 37

2.4.1 Experimental Verifications 37

2.4.2 Spectrally Resolved Luminescence Analysis 39

2.4.3 Luminescence Imaging 40

2.5 Limitations to the Opto-Electronic Reciprocity Theorem 43

2.6 Conclusions 44

References 44

3 Rear Side Diffractive Gratings for Silicon Wafer Solar Cells 49
Marius Peters, Hubert Hauser, Benedikt Bläsi, Matthias Kroll, Christian Helgert, Stephan Fahr, SamuelWiesendanger, Carston Rockstuhl, Thomas Kirchartz, Uwe Rau, AlexanderMellor, Lorenz Steidl, and Rudolf Zentel

3.1 Introduction 49

3.1.1 Gratings for Solar Cells - Basic Idea and Challenges 49

3.1.2 A Short Literature Review 50

3.2 Principle of Light Trapping with Gratings 52

3.3 Fundamental Limits of Light Trapping with Gratings 56

3.4 Simulation of Gratings in Solar Cells 58

3.4.1 Optical Simulation Using RCWA/FMM 58

3.4.2 Optical Simulation Using the Matrix Method 61

3.4.3 Electro-Optically Coupled Simulation Using RCWA and Sentaurus Device 65

3.5 Realization 67

3.5.1 Electron-Beam Lithography 68

3.5.2 Self-Organizing Photonic Crystals 72

3.5.3 Fabrication of Rear Side Gratings via Interference Lithography and Nanoimprint Lithography 75

3.6 Topographical Characterization 78

3.6.1 Atomic Force Microscopy 78

3.6.2 Scanning Electron Microscopy 80

3.6.3 Focused Ion Beam Milling 81

3.7 Summary 84

References 84

4 Randomly Textured Surfaces 91
Carsten Rockstuhl, Stephan Fahr, Falk Lederer, Karsten Bittkau, Thomas Beckers, Markus Ermes, and Reinhard Carius

4.1 Introduction 91

4.2 Methodology 93

4.2.1 Structure of a Referential Solar Cell and Description of Available Substrates 94

4.2.2 Rigorous Methods 96

4.2.3 Scalar Methods 97

4.2.4 Properties of Interest 98

4.2.5 Near-Field Scanning Optical Microscopy 99

4.3 Properties of an Isolated Interface 100

4.3.1 Near-Field Properties 100

4.3.2 Far-Field Properties 102

4.4 Single-Junction Solar Cell 104

4.4.1 Absorption Enhancement 104

4.4.2 Design of Optimized Randomly Textured Interfaces 106

4.5 Intermediate Layer in Tandem Solar Cells 110

4.6 Conclusions 112

Acknowledgments 113

References 113

5 Black Silicon Photovoltaics 117
Kevin Füchsel, Matthias Kroll, Martin Otto, Martin Steglich, Astrid Bingel, Thomas Käsebier, Ralf B.Wehrspohn, Ernst-Bernhard Kley, Thomas Pertsch, and Andreas Tünnermann

5.1 Introduction 117

5.1.1 Fabrication Methods 117

5.1.2 Reactive Ion Etching 119

5.1.3 Laser Processing 122

5.1.4 Chemical and Electrochemical Etching 124

5.2 Optical Properties and Light Trapping Possibilities 126

5.2.1 Overview 126

5.2.2 ICP-RIE Black Silicon 128

5.2.3 Influence of Dielectric Coatings 130

5.2.4 Influence of the SubstrateThickness and Limiting Efficiency 132

5.3 Surface Passivation of Black Silicon 135

5.3.1 Requirements for Black Silicon Passivation 136

5.3.2 Possible Passivation Schemes 136

5.3.3 Passivation of Black Silicon Surfaces 139

5.3.3.1 Surface Damage and Sample Cleaning 139

5.3.3.2 Effective Passivation of ICP-RIE Black Silicon 140

5.4 Black Silicon Solar Cells 142

References 144

6 Concentrator Optics for Photovoltaic Systems 153
Andreas Gombert, Juan C.Mi~nano, Pablo Benitez, and Thorsten Hornung

6.1 Fundamentals of Solar Concen…