Hiroyuki Fujiwara is a Professor at the Department of Electrical, Electronic and Computer Engineering, Gifu University. He received his Ph.D. degree from Tokyo Institute of Technology. He was a research associate at The Pennsylvania State University during 1996-1998. In 1998, he joined the Electrotechnical Laboratory, Ministry of International Trade and Industry, Japan. In 2007, he became a team leader of Research Center for Photovoltaics, National Institute of Advanced Industrial Science and Technology(AIST) in Japan.

• Preface xvAbout the Editor xix1 Introduction 1Hiroyuki Fujiwara1.1 Hybrid Perovskite Solar Cells 11.2 Unique Natures of Hybrid Perovskites 41.2.1 Notable Characteristics of Hybrid Perovskites 51.2.2 Fundamental Properties of MAPbI3 81.2.3 Why Hybrid Perovskite Solar Cells Show High Efficiency? 111.3 Advantages of Hybrid Perovskite Solar Cells 121.3.1 Band Gap Tunability 121.3.2 High Voc 131.3.3 Low Temperature Coefficient 161.4 Challenges for Hybrid Perovskites 161.4.1 Requirement of Improved Stability 171.4.2 Large-Area Solar Cells 191.4.3 Toxicity of Pb and Sn Compounds 201.5 Overview of this Book 22Acknowledgment 23References 232 Overview of Hybrid Perovskite Solar Cells 29Tsutomu Miyasaka and Ajay K. Jena2.1 Introduction 292.2 Historical Backgrounds of Halide Perovskite Photovoltaics 322.3 Semiconductor Properties of Organo Lead Halide Perovskites 342.4 Working Principle of Perovskite Photovoltaics 372.5 Compositional Design of the Halide Perovskite Absorbers 402.6 Strategy for Stabilizing Perovskite Solar Cells 412.7 All Inorganic and Lead-Free Perovskites 482.8 Development of High-Efficiency Tandem Solar Cells 522.9 Conclusion and Perspectives 54References 55Part I Characteristics of Hybrid Perovskites 653 Crystal Structures 67Mitsutoshi Nishiwaki, Tatsuya Narikuri, and Hiroyuki Fujiwara3.1 What Is Hybrid Perovskite? 673.2 Structures of Hybrid Perovskite Crystals 683.2.1 Crystal Structure of MAPbI3 683.2.2 Lattice Parameters of Hybrid Perovskites 713.2.3 Secondary Phase Materials 753.3 Tolerance Factor 773.3.1 Tolerance Factor of Hybrid Perovskites 793.3.2 Tolerance Factor of Mixed-Cation Perovskites 823.4 Phase Change by Temperature 843.5 Refined Structures of Hybrid Perovskites 863.5.1 Orientation of Center Cations 863.5.2 Relaxation of Center Cations 88Acknowledgment 89References 894 Optical Properties 91Hiroyuki Fujiwara, Yukinori Nishigaki, Akio Matsushita, and Taisuke Matsui4.1 Introduction 914.2 Light Absorption in MAPbI3 934.2.1 Visible/UV Region 964.2.2 IR Region 984.2.3 THz Region 994.3 Band Gap of Hybrid Perovskites 1014.3.1 Band Gap Analysis of MAPbI3 1014.3.2 Band Gap of Basic Perovskites 1034.3.3 Band Gap Variation in Perovskite Alloys 1054.4 True Absorption Coefficient of MAPbI3 1064.4.1 Principles of Optical Measurements 1074.4.2 Interpretation of α Variation 1084.5 Universal Rules for Hybrid Perovskite Optical Properties 1114.5.1 Variation with Center Cation 1114.5.2 Variation with Halide Anion 1124.6 Subgap Absorption Characteristics 1144.7 Temperature Effect on Absorption Properties 1164.8 Excitonic Properties of Hybrid Perovskites 117References 1195 Physical Properties Determined by Density Functional Theory 123Hiroyuki Fujiwara, Mitsutoshi Nishiwaki, and Yukinori Nishigaki5.1 Introduction 1235.2 What Is DFT? 1245.2.1 Basic Principles 1245.2.2 Assumptions and Limitations 1265.3 Crystal Structures Determined by DFT 1285.3.1 Hybrid Perovskite Structures 1285.3.2 Organic-Center Cations 1315.4 Band Structures 1325.4.1 Band Structures of Hybrid Perovskites 1325.4.2 Direct–Indirect Issue of Hybrid Perovskite 1345.4.3 Density of States 1395.4.4 Effective Mass 1405.5 Band Gap 1415.5.1 What Determines Band Gap? 1425.5.2 Effect of Center Cation 1435.5.3 Effect of Halide Anion 1435.6 Defect Physics 144Acknowledgment 147References 1476 Carrier Transport Properties 151Hiroyuki Fujiwara and Yoshitsune Kato6.1 Introduction 1516.2 Carrier Properties of Hybrid Perovskites 1536.2.1 Self-Doping in Hybrid Perovskites 1536.2.2 Effect of Carrier Concentration on Mobility 1556.3 Carrier Mobility of MAPbI3 1556.3.1 Variation of Mobility with Characterization Method 1566.3.2 Temperature Dependence 1596.3.3 Effect of Effective Mass 1606.3.4 What Determines Maximum Mobility of MAPbI3? 1616.4 Diffusion Length 1646.5 Carrier Transport in Various Hybrid Perovskites 166References 1687 Ferroelectric Properties 173Tobias Leonhard, Holger Röhm, Alexander D. Schulz, and Alexander Colsmann7.1 On the Importance of Ferroelectricity in Hybrid Perovskite Solar Cells 1737.2 Ferroelectricity 1747.2.1 Crystallographic Considerations 1747.2.2 Ferroelectricity in Thin Films 1787.2.3 Crystallography of MAPbI3 Thin Films 1787.3 Probing Ferroelectricity on the Microscale 1797.3.1 Atomic Force Microscopy 1797.3.2 Piezoresponse Force Microscopy 1807.3.3 Characterization of MAPbI3 Thin Films with sf-PFM 1837.3.4 Correlative Domain Characterization 1887.3.4.1 Transmission Electron Microscopy 1887.3.4.2 X-ray Diffraction 1897.3.4.3 Electron Backscatter Diffraction 1897.3.4.4 Kelvin Probe Force Microscopy 1917.3.5 Polarization Orientation 1917.3.6 Ferroelastic Effects in MAPbI3 Thin Films 1937.4 Ferroelectric Poling of MAPbI3 1957.4.1 AC Poling of MAPbI3 1967.4.2 Creeping Poling and Switching Events on the Microscopic Scale 1977.4.3 Macroscopic Effects of Poling 2007.5 Impact of Ferroelectricity on the Performance of Solar Cells 2017.5.1 Pitfalls During Sample Measurements 2017.5.2 Charge Carrier Dynamics in Solar Cells 203References 2038 Photoluminescence Properties 207Yasuhiro Yamada and Yoshihiko Kanemitsu8.1 Introduction 2078.2 Overview of Luminescent Properties 2088.3 Room-Temperature PL Spectra of a Hybrid Perovskite Thin Film 2098.4 Time-Resolved PL of a Hybrid Perovskite 2138.5 PL Quantum Efficiency 2188.6 Temperature-Dependent PL 2208.7 Material and Device Characterization by PL Spectroscopy 2228.7.1 Degradation and Healing of Hybrid Perovskites 2228.7.2 Charge Transfer Mechanism in Perovskite Solar Cell 2238.8 Conclusion 224Acknowledgment 225References 2259 Role of Grain Boundaries 229Jae Sung Yun9.1 Introduction 2299.2 Role of Grain Boundaries in Device Performance 2309.2.1 Potential Barrier at GBs and Charge Transport 2319.2.2 Engineering of GB Properties 2349.3 Ion Migration Through Grain Boundaries 2419.3.1 Enhanced Ion Transport at Grain Boundaries 2419.3.2 Role of GBs for Ion Migration 2449.4 Role of Grain Boundaries in Stability 2469.4.1 MAPbI3 Hydrated Phase at GBs 2479.4.2 Formation of Non-perovskite Phase at GBs of FAPbI3 248References 25010 Roles of Center Cations 253Biwas Subedi, Juan Zuo, Marie Solange Tumusange, Maxwell M. Junda, Kiran Ghimire, and Nikolas J. Podraza10.1 Introduction 25310.2 Cubic Perovskite Phase Tolerance Factor 25610.3 Thin Film Stability 25810.4 Optoelectronic Property Variations 26310.5 Solar Cell Performance 268References 271Part II Hybrid Perovskite Solar Cells 27511 Operational Principles of Hybrid Perovskite Solar Cells 277Hiroyuki Fujiwara, Yoshitsune Kato, Yuji Kadoya, Yukinori Nishigaki, Tomoya Kobayashi, Akio Matsushita, and Taisuke Matsui11.1 Introduction 27711.2 Operation of Hybrid Perovskite Solar Cells 27811.2.1 Operational Principle and Basic Structures 27811.2.2 Band Alignment 28111.3 Band Diagram of Hybrid Perovskite Solar Cells 28311.3.1 Device Simulation 28311.3.2 Experimental Observation 28511.4 Refined Analyses of Hybrid Perovskite Solar Cells 28711.4.1 Carrier Generation and Loss 28711.4.2 Power Loss Mechanism 29111.4.3 e-ARC Software 29511.5 What Determines Voc? 29511.5.1 Effect of Interface 29711.5.2 Effect of Passivation 30011.5.3 Effect of Grain Boundary 303References 30512 Efficiency Limits of Single and Tandem Solar Cells 309Hiroyuki Fujiwara, Yoshitsune Kato, Masayuki Kozawa, Akira Terakawa, and Taisuke Matsui12.1 Introduction 30912.2 What Is the SQ Limit? 31012.2.1 Physical Model 31112.2.2 Blackbody Radiation 31312.2.3 SQ Limit 31512.3 Maximum Efficiencies of Perovskite Single Cells 31912.3.1 Concept of Thin-Film Limit 31912.3.2 EQE Calculation Method 32112.3.3 Maximum Efficiencies of Single Solar Cells 32312.3.4 Performance-Limiting Factors of Hybrid Perovskite Devices 32512.4 Maximum Efficiency of Tandem Cells 32712.4.1 Optical Model and Assumptions 32812.4.2 Calculation of Tandem-Cell EQE Spectra 32912.4.3 Maximum Efficiencies of Tandem Devices 33112.4.4 Realistic Maximum Efficiency of Tandem Cell 33412.5 Free Software for Efficiency Limit Calculation 335References 33613 Multi-cation Hybrid Perovskite Solar Cells 339Jacob N. Vagott and Juan-Pablo Correa-Baena13.1 Introduction 33913.2 Types of A-Site Multi-cation Hybrid Perovskite Solar Cells 34113.2.1 Pb-Based Multi-cation Hybrid Perovskite Solar Cells 34113.2.2 Sn-Based Multi-cation Hybrid Perovskite Solar Cells 34413.3 Cation Selection in Mixed-Cation Hybrid Perovskite Solar Cells 34513.3.1 Organic A-Cations 34513.3.2 Inorganic A-Cations 34713.4 Fabrication of Mixed-Cation Hybrid Perovskite Solar Cells 34913.4.1 Traditional Fabrication Approach 34913.4.2 Emerging Fabrication Technologies 35013.5 Charge Transport Materials 35313.6 Surface Passivation 35713.7 Mixed B-Cation Hybrid Organic–Inorganic Perovskite Solar Cells 36113.8 Basic Characterization of Mixed-Cation Hybrid Perovskite Solar Cells 362References 36514 Tin Halide Perovskite Solar Cells 373Gaurav Kapil and Shuzi Hayase14.1 Introduction 37314.1.1 Device Structure and Operating Principle 37414.1.2 Crystal Structure 37514.2 Tin Perovskite Solar Cells 37614.2.1 Intrinsic Properties 37714.2.2 Carrier Lifetime and Diffusion Length 37814.3 The Status of Sn Perovskite Solar Cells 37914.3.1 Different Type of Sn Perovskite Solar Cells 38014.3.1.1 CsSnI3 38014.3.1.2 MASnI3 38314.3.1.3 FASnI3 38414.3.1.4 FAxMA1-xSnI3 38514.3.1.5 2D/3D FASnI3 38714.3.1.6 Sn–Ge mixed PSCs 38714.3.2 Strategies to Improve the Efficiency 38914.3.2.1 Film Fabrication Methods 38914.3.2.2 Use of Reducing Agents 38914.3.2.3 Doping Effect of Large Organic Cations 39014.3.2.4 Device Engineering and Lattice Relaxation 39114.4 Sn–Pb Perovskite Solar Cells 39314.4.1 Anomalous Bandgap of SnPb (The Bowing Effect) 39614.4.2 Physical Properties 39814.4.2.1 Intrinsic Carrier Concentration 39814.4.2.2 Carrier Lifetime and Diffusion Length 39914.5 The Status of Sn–Pb Perovskite Solar Cells 39914.5.1 Different Types of Sn–Pb Perovskite Solar Cells 40114.5.1.1 First Kind of Sn–Pb PSC absorber: MASnxPb1-xI3 40114.5.1.2 Multi Cation Sn–Pb Perovskites: (FA, MA, Cs) (Sn, Pb)(I, Br, Cl)3 40114.5.2 Strategies to Improve the Efficiency 40314.5.2.1 Use of Additives 40314.5.2.2 Device Engineering 40414.6 Conclusion and Outlook 406References 40615 Stability of Hybrid Perovskite Solar Cells 411Seigo Ito15.1 Introduction: Trigger of the Degradation 41115.2 Crystal Quality for Stable Perovskite Solar Cells 41315.3 Water-Stable and MA-Free Perovskites 41515.4 Defects and Grain-Surface Ion Migration, and Passivation (Including 2-D Crystal) 41715.5 Degradation at Interface with Metal Oxides 42015.6 Porous Carbon Electrode to Be Very Stable Multiporous-Layered- Electrode Perovskite Solar Cells (MPLE-PSC) 42015.7 Damp Heat Tests 42115.8 Conclusion 422References 42516 Hysteresis in J–V Characteristics 429Wolfgang Tress16.1 Introduction and Definitions: What Do We Mean by Hysteresis? 42916.2 The JV Curve of a Solar Cell: What Does It Tell? 43116.3 Characteristics of Hysteresis: What Does It Depend on? 43716.4 Mechanistic and Microscopic Origin of Hysteresis: What Changes Slowly? 44216.5 Issues with Hysteresis: How to Tune/Avoid/Suppress? 45316.6 Conclusion and Open Questions 453References 45417 Perovskite-Based Tandem Solar Cells 463Klaus Jäger and Steve Albrecht17.1 Introduction 46317.2 Architectures of Tandem Solar Cells 46517.2.1 Monolithic Two-Terminal Solar Cells 46617.2.2 Four-Terminal Tandem Solar Cells 46717.2.3 Other Concepts 46817.2.4 Bifacial Solar Cells 46917.3 Efficiency Limits of Multi-Junction Solar Cells 46917.3.1 Efficiency Limit for Four-Terminal Tandem Solar Cells 47017.3.2 Efficiency Limit for Two-Terminal Tandem Solar Cells 47217.3.3 Efficiency Limit for Cells with More Junctions 47417.4 Perovskites as Tandem Solar Cell Materials 47417.5 Experimental Results on Perovskite-Based Tandem Solar Cells 47717.5.1 Perovskite/Silicon Tandem Solar Cells 48217.5.2 Perovskite-Chalcogenide Tandem Solar Cells 48917.6 Energy Yield Calculations 49317.6.1 Illumination Model 49417.6.2 Optical Model 49417.6.3 Electrical Model 49617.6.4 Temperature Model 49817.6.5 Energy Yield Calculation 49817.7 Conclusions and Outlook 499Acknowledgments 500References 50018 All Perovskite Tandem Solar Cells 509Zhaoning Song and Yanfa Yan18.1 Introduction 50918.2 Working Principles of Tandem Solar Cells 51118.2.1 Why to Use Tandem Solar Cells 51118.2.2 Tandem Device Architectures 51318.2.3 PCE of Tandem Solar Cells 51418.3 Wide-Bandgap Perovskite Solar Cells 51618.3.1 Wide-Bandgap Mixed I-Br Perovskites 51618.3.2 Current State of Wide-Bandgap Perovskite Solar Cells 51818.3.3 Critical Issues of Wide-Bandgap Perovskite Cells 51918.4 Low-Bandgap Perovskite Solar Cells 52018.4.1 Low-Bandgap Mixed Sn-Pb Perovskites 52018.4.2 Current State of Low-Bandgap Perovskite Solar Cells 52418.4.3 Critical Issues of Low-Bandgap Perovskite Cells 52518.5 All-Perovskite Tandem Solar Cells 52718.5.1 4-T All-Perovskite Tandem Solar Cells 52718.5.2 2-T All-Perovskite Tandem Solar Cells 52818.5.3 Limitations and Challenges of All-Perovskite Tandem Solar Cells 53318.6 Conclusion and Outlooks 534Acknowledgments 535References 535A Optical Constants of Hybrid Perovskite Materials 541Yukinori Nishigaki, Akio Matsushita, Alvaro Tejada, Taisuke Matsui, and Hiroyuki FujiwaraReferences 562B Numerical Values of Shockley–Queisser Limit 563Yoshitsune Kato and Hiroyuki FujiwaraIndex 567

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