Copper Zinc Tin Sulphide–Based Thin Film Solar Cells

Kentaro Ito Department of Electrical and Electronic Engineering, Shinsu University, Japan

Preface ix List of Contributors xi Part I Introduction 1 1 An Overview of CZTS-Based Thin-Film Solar Cells 3 Kentaro Ito 1.1 Introduction 3 1.2 The Photovoltaic Effect 4 1.3 In Pursuit of an Optimal Semiconductor for Photovoltaics 22 1.4 Conclusions 36 Acknowledgements 37 References 37 2 Market Challenges for CZTS-Based Thin-Film Solar Cells 43 Arnulf Jager-Waldau 2.1 Introduction 43 2.2 Compound Thin-Film Technologies and Manufacturing 45 2.3 Challenges for CZTS Solar Cells in the Market 49 2.4 Conclusion 51 References 51 Part II The Physics and Chemistry of Quaternary Chalcogenide Semiconductors 53 3 Crystallographic Aspects of Cu2ZnSnS4 (CZTS) 55 Susan Schorr 3.1 Introduction: What Defines a Crystal Structure? 55 3.2 The Crystal Structure of CZTS 57 3.3 Point Defects in CZTS and the Role of Stoichiometry 68 3.4 Differentiation between Intergrown Kesterite- and Stannite-Type Phases: A Simulational Approach 71 3.5 Summary 72 References 73 4 Electronic Structure and Optical Properties from First-Principles Modeling 75 Clas Persson, Rongzhen Chen, Hanyue Zhao, Mukesh Kumar and Dan Huang 4.1 Introduction 75 4.2 Computational Background 77 4.3 Crystal Structure 80 4.4 Electronic Structure 82 4.5 Optical Properties 97 4.6 Summary 101 Acknowledgements 102 References 102 5 Kesterites: Equilibria and Secondary Phase Identification 107 Dominik M. Berg and Phillip J. Dale 5.1 Introduction 107 5.2 Chemistry of the Kesterite Reaction 108 5.3 Phase Identification 116 Acknowledgements 128 References 128 6 Growth of CZTS Single Crystals 133 Akira Nagaoka and Kenji Yoshino 6.1 Introduction 133 6.2 Growth Process 134 6.3 Properties of CZTS Single Crystals 141 6.4 Conclusion 145 Acknowledgements 146 References 146 7 Physical Properties: Compiled Experimental Data 149 Sadao Adachi 7.1 Introduction 149 7.2 Structural Properties 150 7.3 Thermal Properties 152 7.4 Mechanical and Lattice Dynamic Properties 157 7.5 Electronic Energy-Band Structure 162 7.6 Optical Properties 169 7.7 Carrier Transport Properties 170 References 176 Part III Synthesis of Thin Films and Their Application to Solar Cells 181 8 Sulfurization of Physical Vapor-Deposited Precursor Layers 183 Hironori Katagiri 8.1 Introduction 183 8.2 First CZTS Thin-Film Solar Cells 184 8.3 ZnS as Zn-Source in Precursor 184 8.4 Influence of Absorber Thickness 187 8.5 New Sulfurization System 188 8.6 Influence of Morphology 189 8.7 Co-Sputtering System with Annealing Chamber 190 8.8 Active Composition 191 8.9 CZTS Compound Target 192 8.10 Conclusions 201 References 201 9 Reactive Sputtering of CZTS 203 Charlotte Platzer-Bjorkman, Tove Ericson, Jonathan Scragg and Tomas Kubart 9.1 Introduction 203 9.2 The Reactive Sputtering Process 205 9.3 Properties of Sputtered Precursors 206 9.4 Annealing of Sputtered Precursors 214 9.5 Device Performance 215 9.6 Summary 217 References 217 10 Coevaporation of CZTS Films and Solar Cells 221 Thomas Unold, Justus Just and Hans-Werner Schock 10.1 Introduction 221 10.2 Basic Principles 221 10.3 Process Variations 227 Acknowledgements 236 References 236 11 Synthesis of CZTSSe Thin Films from Nanocrystal Inks 239 Charles J. Hages and Rakesh Agrawal 11.1 Introduction 239 11.2 Nanocrystal Synthesis 241 11.3 Nanocrystal Characterization 249 11.4 Sintering 251 11.5 Conclusion 264 References 264 12 CZTS Thin Films Prepared by a Non-Vacuum Process 271 Kunihiko Tanaka 12.1 Introduction 271 12.2 Sol-Gel Sulfurization Method 272 12.3 Preparation of CZTS Thin Films by Sol-Gel Sulfurization Method 274 12.4 Chemical Composition Dependence 279 12.5 H2S Concentration Dependence 282 12.6 CZTS Solar Cell Prepared by Non-vacuum Processes 284 References 285 13 Growth of CZTS-Based Monograins and Their Application to Membrane Solar Cells 289 Enn Mellikov, Mare Altosaar, Marit Kauk-Kuusik, Kristi Timmo, Dieter Meissner, Maarja Grossberg, Juri Krustok and Olga Volobujeva 13.1 Introduction 289 13.2 Monograin Powder Growths, Basics of the Process 291 13.3 Influence of Chemical Etching on the Surface Composition of Monograins 295 13.4 Thermal Treatment of CZTS-Based Monograins 298 13.5 Optoelectronic Properties of CZTS-Based Monograins and Polycrystals 300 13.6 Conclusion 306 References 306 Part IV Device Physics of Thin-Film Solar Cells 311 14 The Role of Grain Boundaries in CZTS-Based Thin-Film Solar Cells 313 Joel B. Li and Bruce M. Clemens 14.1 Introduction 313 14.2 CIGSe and CdTe Solar Cells 314 14.3 CZTS-Based Thin-Film Solar Cells 318 14.4 Conclusion 327 References 328 15 CZTS-Based Thin-Film Solar Cells Prepared via Coevaporation 335 Byungha Shin, Talia Gershon and Supratik Guha 15.1 Introduction 335 15.2 Preparation of CZTS and CZTSe Absorbers 337 15.3 Fundamental Properties of Coevaporated CZTS and CZTSe Absorbers 338 15.4 Device Characteristics of Full-Sulfide CZTS Thin-Film Solar Cells 348 15.5 Device Characteristics of Full-Selenide CZTSe Thin-Film Solar Cells 354 15.6 Summary 358 References 358 16 Loss Mechanisms in Kesterite Solar Cells 363 Alex Redinger and Susanne Siebentritt 16.1 Introduction 363 16.2 Current State-of-the-Art CZTS-Based Thin-Film Solar Cells 364 16.3 Dominant Recombination Path 366 16.4 Band-Gap Variations 372 16.5 Series Resistance and its Relation to Voc Losses 376 16.6 Conclusion 381 Acknowledgements 382 References 382 17 Device Characteristics of Hydrazine-Processed CZTSSe 387 Oki Gunawan, Tayfun Gokmen and David B. Mitzi 17.1 Introduction 387 17.2 Device Characteristics 389 17.3 Summary 406 Acknowledgements 407 References 408 Subject Index 413