Organic and Hybrid Solar Cells (eBook)

Contents 5
Contributors 6
Chapter 1 8
Introduction to Organic Solar Cells 8
1.1 Introduction 8
1.2 Materials 9
1.3 Operating Principles of OSCs 11
1.3.1 Exciton Generation 11
1.3.2 Exciton Diffusion 11
1.3.3 Exciton Dissociation 12
1.3.4 Charge Transport to the Electrodes for Collection 12
1.4 Device Configurations 13
1.4.1 Planar Bilayer Configuration 13
1.4.2 Bulk Heterojunction Configuration 14
1.4.3 Tandem Device Configuration 15
1.5 Characterization of OSCs 17
1.6 Degradation of OSCs 19
1.7 Hybrid Solar Cells 20
Conclusions 21
References 21
Chapter 2 26
Charge Transport and Recombination in Organic Solar Cells (OSCs) 26
2.1 Basic Concepts of Charge Transport in Organic Semiconductors 26
2.1.1 General Approach to Charge Transfer Mechanisms 27
2.2 Operation of Organic Photovoltaic (OPV) 29
2.2.1 Photovoltaic Effect 29
2.2.1.1 Photon Absorption 29
2.2.1.2 Semiconductor Photovoltaic Effect and Charge Transport Equations 30
2.2.2 Solar Cell Equivalent Circuit Model 30
2.2.3 Organic Photovoltaic Cells 32
2.2.4 Basic Charge Transport Expressions in Organic Solar Cells 33
2.2.5 Origin of Voc, Jsc, and FF 34
2.2.5.1 Voc 34
2.2.5.2 Jsc 35
2.2.5.3 FF 35
2.2.6 Geminate and Nongeminate Recombination 37
2.2.6.1 Geminate Recombination 37
2.2.6.2 Nongeminate Recombination 39
2.3 Development of Carrier Transport and Recombination Measurement for OPV Cells 40
2.3.1 Time-of-Flight (TOF) 40
2.3.2 Field Effect Transistor 41
2.3.3 Space Charge Limited Current (SCLC) 43
2.3.4 Transient Photovoltage/Photocurrent Measurement 46
2.3.5 Charge Extraction by Linearly Increasing Voltage (CELIV) and Photo-CELIV Measurement 48
2.3.6 Microwave Conductivity 50
2.4 Outlook 53
Reference 53
Chapter 3 60
Donor Materials for Organic Solar Cell (OSC) 60
3.1 Introduction 60
3.2 Donor–Acceptor Alternating Polymers for OPV 62
3.2.1 Classification of Donor Building Blocks 62
3.2.2 Classification of Acceptor Building Blocks 63
3.2.3 BT-Containing D–A Polymers 64
3.2.3.1 BT-based Donor Polymers for Photovoltaic Application 64
3.2.3.2 Alkoxyl Substituted BT-based Donor Polymers for Photovoltaic Applications 67
3.2.3.3 Fluorine Substituted BT (F-BT)-based Donor Units for Photovoltaic Applications 69
3.2.3.4 NT-based Donor Polymers for Photovoltaic Application 72
3.2.4 DPP-Containing D–A Polymers for PSC Applications 73
3.2.5 IID-Containing D–A Polymers 76
3.2.6 TPD-Containing D–A Polymers 78
3.2.7 QX-Containing D–A Polymers 80
3.2.8 TQX-Containing D–A Polymers 82
3.2.9 Tz-Containing D–A Polymers 83
3.2.10 Other Types 86
3.2.10.1 Conjugated Polymers with Pendant D–A Side Chains 86
3.2.10.2 D–A Conjugated Polymers with Three Components in the Main Chains 88
3.3 Donor–Acceptor-based SMs for OPV 90
3.3.1 SM for Solar Cells Fabricated by Thermal Evaporation 90
3.3.2 SM for Solar Cells Made by Solution Processing 92
3.3.2.1 DPP-based SMs 92
3.3.2.2 DTS-based SMs 94
3.3.2.3 Oligothiophenes and Its Derivatives 95
Conclusion 97
References 98
Chapter 4 104
?n?-Type Electron-Accepting Materials for Organic Solar Cells (OSC) 104
4.1?????Introduction 104
4.2?????Principle and Design 105
4.3?????Fullerene-Based Materials 107
4.4?????Non-fullerene Materials 113
Conclusions and Remarks 121
References 122
Chapter 5 127
Interfacial Layers in Organic Solar Cells 127
5.1 Introduction 127
5.2 Need for Interfacial Layer in OSCs 128
5.2.1 Large Exciton Binding Energy in Organic Semiconductors 128
5.2.2 Tradeoff Between the Short Exciton Diffusion Distance and Large Absorption Thickness of Organic Absorber 129
5.2.3 The Demand of Charge Selectivity at Electrode Interface for Bulk Heterojunction OSCs 130
5.2.4 Low Stability of Organic Semiconductors 130
5.2.5 The Key Role of Ohmic Contact in Determining Open Circuit Voltage for OSCs 131
5.3 Function of Interfacial Layers in OSCs 133
5.3.1 Interfacial Layers for Hole Collection 133
5.3.1.1 PEDOT:PSS Interlayer 133
5.3.1.2 Transition Metal Oxide Interfacial Layers 138
5.3.1.3 Other Interfacial Layers for Hole Collection 141
5.3.2 Interfacial Layers for Electron Collection 143
5.3.2.1 Metal Compound as Interfacial Layer 143
5.3.2.2 ZnO and TiO2 Interfacial Layers 147
5.3.2.3 Organic/Polymer Interlayers 150
5.3.2.4 Other Cathode Buffer Layer 153
5.3.3 Interfacial Layers for Exciton Dissociation 154
5.3.4 Interconnecting Layers (ICLs) in Tandem Structure OSCs 157
5.3.5 Interfacial Layers for Morphology Control 164
5.3.6 Interfacial Layers for Light Harvesting 167
5.4 Final Thoughts and Future Developments 170
References 171
Chapter 6 183
Alternative Electrodes for OSC 183
6.1 Introduction 183
6.2 Inorganic Nanomaterial-Based Alternative TCEs 186
6.2.1 Thin Metal Layers 186
6.2.2 Metal Nanoparticles and Grids 188
6.2.3 Silver Nanowires (Ag NWs) 191
6.3 Organic and Carbon-Based Alternative TCEs 195
6.3.1 PEDOT:PSS 195
6.3.2 CNTs 199
6.3.3 Graphene 203
6.4 Hybrid Materials-Based Alternative TCEs 208
6.4.1 PEDOT:PSS-Metal-Based Hybrid TCEs 208
6.4.2 PEDOT:PSS-CNTs-Based Hybrid TCEs 210
6.4.3 Graphene and GO-Based Hybrid TCEs 210
6.5 Outlook 212
References 214
Biography 219
Chapter 7 220
Inverted Organic Solar Cells (OSCs) 220
7.1 Introduction 220
7.2 Interface Engineering for High-Performance Inverted OSCs 222
7.2.1 Engineering of CBLs 222
7.2.1.1 Low WF Metals and Alkali Metal Compounds as CBLs 222
7.2.1.2 Semiconducting Metal Oxides as CBLs 224
7.2.1.3 Organic CBLs 227
7.2.1.4 Hybrid CBLs 229
7.2.2 Engineering of ABLs 229
7.2.2.1 PEDOT: PSS ABLs 230
7.2.2.2 MoO3 and Other Transition Metal Oxide ABLs 232
7.2.2.3 GO and Their Composites as ABLs 233
7.2.3 ICLs for Inverted Tandem OSCs 233
7.2.3.1 Thermally Evaporated ICLs 235
7.2.3.2 All Solution-Processed ICLs 236
7.3 Optimization of BHJ Layers for Inverted OSCs 238
7.3.1 Thermal Annealing 239
7.3.2 Additives 239
7.3.3 BHJ Film Thickness 240
7.3.4 Plasmonic Enhancement 241
Conclusion and Outlook 242
References 243
Chapter 8 248
Stability of Organic Solar Cells (OSCs) 248
8.1 Introduction 248
8.2 Measurement of OSC Stability 249
8.2.1 Controlling of Testing Environment 249
8.2.2 Accelerated Testing of OSC Stabilities 250
8.2.3 Inter-laboratory Studies of OSC Stabilities 251
8.3 Photo-oxidation of Organic Semiconductors 252
8.3.1 Photo-oxidation of Donor Semiconductors 252
8.3.2 Photo-oxidation of Fullerene Acceptors 256
8.4 Morphology Degradations and Strategies for Morphology Stabilization 256
8.4.1 Organic Semiconductors with Thermocleavability 257
8.4.2 Regularity and Crystallinity Control 258
8.4.3 Organic Semiconductors with Cross-linkable Capability 260
8.4.4 Hydrogen Bonding Interactions 266
8.4.5 Covalent Bonded Donor and Acceptor Dyad 267
8.4.6 Compatibilizer for Improving Performance Stability 267
8.5 Degradation and Stability of Metal Electrode 269
8.6 Interfacial layer for Stable OSCs 269
8.6.1 Cathode Interfacial Layer for Stable OSCs 269
8.6.2 Anode Interfacial Layer for Stable OSCs 271
Conclusion and Outlook 274
References 275
Chapter 9 280
Research Progress and Manufacturing Techniques for Large-Area Polymer Solar Cells 280
9.1 Introduction 280
9.2 Structure and Operation Principle of OPV 282
9.2.1 Structure of OPV Devices 282
9.2.2 Operation Principle 283
9.2.3 Performance Characteristics 284
9.2.3.1 Short-Circuit Current Density 285
9.2.3.2 Fill Factor 285
9.2.3.3 Open-Circuit Voltage 286
9.2.4 Manufacturing Techniques in Large-Area OPV 286
9.2.4.1 Spin Coating 286
9.2.4.2 Screen Printing 290
9.2.4.3 Inkjet Printing 292
9.2.4.4 Doctor Blading 294
9.2.4.5 R2R Printing 295
9.2.4.6 Other Techniques 301
Conclusion 303
References 304
Chapter 10 306
Colloidal Inorganic-Organic Hybrid Solar Cells 306
10.1 Introduction 306
10.2 Introducing Inorganic Nanocrystals 308
10.3 Hybrid Solar Cells 309
10.3.1 Charge Transfer at Hybrid Interfaces 309
10.3.2 Tailoring the Polymer-NC Interface 311
10.3.3 Charge Transport: The Roles of Nanocrystal Shape and Film Morphology 314
10.3.4 NIR Light Harvesting by Lead Chalcogenide Nanocrystals 316
10.4 Quantum Dot Solids 317
10.4.1 Electronic Structure and Transport in QD Solids 318
10.4.2 QD Solid Solar Cells 320
10.5 Recent Progress in Hybrid Solar Cells 322
10.6 Recent Progress in Quantum Dot Solid Solar Cells 329
10.6.1 Role of Device Structure 330
10.6.2 The Role of Surface Chemistry 332
10.7 Future Prospects of Hybrid Solar Cells 333
References 335