Preface .........................................................xi
Acknowledgements ............................................. xiii
List of Contributors ........................................... xv
1 The Different PV Technologies and How They Degrade ........... 1
Frederik С. Krebs
1.1 The Photovoltaic Effect and the Overview ................ 1
1.2 The Photovoltaic Technologies ........................... 2
1.3 Intrinsic Versus Extrinsic Stability .................... 3
1.3.1 Intrinsic Stability .............................. 3
1.3.2 Extrinsic Stability .............................. 3
1.4 Degradation - The Culprits, the What, the Why and the
How ..................................................... 3
1.5 Some Representative Technologies and How They Degrade ... 4
1.5.1 Mono- and Polycrystalline Silicon Solar Cells .... 5
1.5.2 Amorphous, Micro- and Nanocrystalline Silicon
Solar Cells ...................................... 6
1.5.3 CIS/CIGS Solar Cells ............................. 8
1.5.4 CdS/CdTe Solar Cells ............................. 9
1.5.5 Dye-Sensitized Solar Cells (DSSC) ............... 10
1.5.6 Organic and Polymer Solar Cells (OPV) ........... 11
References .................................................. 12
2 Chemical and Physical Probes for Studying Degradation ....... 17
Birgitta Andreasen and Kion Norrman
2.1 Introduction ........................................... 17
2.2 Physical Probes ........................................ 18
2.2.1 UV-vis Spectroscopy ............................. 18
2.2.2 Atomic Force Microscopy (AFM) ................... 18
2.2.3 Interference Microscopy ......................... 20
2.2.4 Scanning Electron Microscopy (SEM) .............. 21
2.2.5 Fluorescence Microscopy ......................... 23
2.2.6 Light-Beam Induced-Current Microscopy (LBIC) .... 24
2.2.7 Electroluminescence and Photoluminescence
Imaging Microscopy (ELI and PLI) ................ 25
2.2.8 X-ray Reflectometry ............................. 26
2.3 Chemical Probes ........................................ 27
2.3.1 Infrared Spectroscopy (IR) ...................... 27
2.3.2 Time-of-Flight Secondary Ion Mass Spectrometry
(TOF-SIMS) ...................................... 28
2.3.3 X-ray Photoelectron Spectroscopy (XPS) .......... 32
2.4 Summary and Outlook .................................... 35
References .................................................. 36
3 Imaging Techniques for Studying OPV Stability and
Degradation ................................................. 39
Marco Seeland, Roland Rösch and Harald Hoppe
3.1 Introduction to Imaging Techniques ..................... 39
3.1.1 Microscopy and Optical Scanning ................. 39
3.1.2 Luminescence Imaging ............................ 40
3.1.3 Lock-In Thermography ............................ 43
3.1.4 Light-Beam Induced Current ...................... 45
3.2 Reports ................................................ 46
3.2.1 Background: Degradation of OLED Devices ......... 46
3.2.2 Light-Beam Induced Current ...................... 50
3.2.3 Luminescence Imaging ............................ 54
3.2.4 Optical Microscopy .............................. 57
3.2.5 Dark Lock-In Thermography and LBIC .............. 58
3.2.6 Dark Lock-In Thermography and Optical Scanning
for Failure Analysis ............................ 62
3.3 Discussion: Comparison of Imaging Techniques ........... 63
3.4 Summary ................................................ 66
Acknowledgement ............................................. 66
References .................................................. 66
4 Photochemical Stability of Materials for OPV ................ 71
Matthieu Manceau, Agnès Rivaton and Jean-Luc Gardette
4.1 Introduction ........................................... 71
4.2 Methods ................................................ 72
4.2.1 Aging Condition ................................. 72
4.2.2 Degradation Monitoring .......................... 74
4.3 State-of-the-Art ....................................... 82
4.3.1 Degradation of the π-Conjugated Polymer ......... 82
4.3.2 Acceptor Material Aging and Blend Degradation ... 99
References ................................................. 102
5 Degradation of Small-Molecule-Based OPV .................... 109
Martin Hermenau, Moritz Riede and Karl Leo
5.1 Comparison to Small-Molecule OLEDs .................... 110
5.1.1 Number of Photoexcitations per Molecule ........ 113
5.2 Comparison to Polymer Solar Cells ..................... 115
5.2.1 Sensitivity to Air ............................. 115
5.2.2 Temperature Stability .......................... 115
5.3 Small-Molecule Organic Materials ...................... 116
5.3.1 Active Materials ............................... 116
5.3.2 Transport- and Exciton-Blocking Materials ...... 119
5.4 Degradation Conditions ................................ 125
5.4.1 Oxygen and Water ............................... 125
5.4.2 UV Radiation ................................... 132
5.5 State-of-the-Art in Lifetime Studies .................. 134
5.6 Summary and Outlook ................................... 138
References ................................................. 139
6 Degradation of Polymer-Based OPV ........................... 143
Mikkel Jørgensen and Frederik С. Krebs
6.1 Focus on the Degradation and Stability of Polymer
Solar Cells ........................................... 143
6.2 A Chart of Degradation and Stability of Polymer
Solar Cells ........................................... 143
6.3 A Short Account of the OPV Stability/Degradation
History ............................................... 144
6.3.1 The Divisions of Degradation Mechanisms ........ 146
6.3.2 The Methodologies .............................. 148
6.4 Modus Operandi for Evolving OPV ....................... 148
6.5 The Recent Developments ............................... 149
6.5.1 The Photocatalytic Oxides ...................... 149
6.5.2 Interlayers .................................... 150
6.5.3 The Inverted Structure ......................... 151
6.5.4 R2R Processing ................................. 152
6.5.5 Lamination and Encapsulation ................... 153
6.5.6 Water Processing ............................... 154
6.5.7 Mechanical Degradation - Delamination .......... 155
6.6 Interlaboratory Studies and Round Robins .............. 156
6.7 Outside Studies ....................................... 157
6.8 How Far Can OPV Be Taken in Terms of Stability? ....... 158
References ................................................. 158
7 Test Equipment for OPV Stability ........................... 163
Olivier Haillant
7.1 Introduction .......................................... 163
7.2 Reliability and Durability Testing of PV Products ..... 165
7.2.1 Reliability, a Function of Durability .......... 165
7.2.2 Environmental Durability ....................... 166
7.2.3 Durability and Weathering Testing .............. 167
7.3 Laboratory Weathering Testing ......................... 168
7.3.1 Acceleration ................................... 168
7.3.2 Relevance ...................................... 169
7.3.3 Precision ...................................... 170
7.3.4 Introduction to Determination of Acceleration
Factors ........................................ 170
7.4 Durability Testing Techniques ......................... 172
7.4.1 Outdoor Weathering ............................. 172
7.4.2 Laboratory Weathering .......................... 175
7.4.3 Laboratory Photoaging .......................... 180
7.4.4 Others ......................................... 183
7.5 Conclusion ............................................ 185
References ................................................. 186
8 Characterization and Reporting of OPV Device Lifetime ...... 193
Suren A. Gevorgyan
8.1 Introduction .......................................... 193
8.2 Photoelectric Characterization of OPV Devices ......... 194
8.2.1 Photoelectric Characterization Tools ........... 194
8.2.2 Characterization in Controlled Environments .... 197
8.3 Interlaboratory Studies of OPVs ....................... 202
8.3.1 Introduction ................................... 202
8.3.2 Interlaboratory Studies of Flexible Large-
Area Roll-to-Roll Processed Polymer Solar
Cell Modules ................................... 203
8.3.3 Interlaboratory Stability Studies of OPVs ...... 204
8.4 Lifetime Testing and Reporting: Standardized
Approach .............................................. 213
8.4.1 Introduction ................................... 213
8.4.2 Procedures for Standard Lifetime
Measurements ................................... 214
8.4.3 Reporting Lifetime ............................. 235
8.5 Conclusions ........................................... 238
List of Abbreviations ...................................... 238
References ................................................. 238
9 Concentrated Light for Organic Photovoltaics ............... 243
Thomas Tromholt
9.1 Introduction .......................................... 243
9.2 Light-Concentration Setups ............................ 245
9.2.1 Refractive Sunlight Concentration .............. 245
9.2.2 Reflective Sunlight Concentration .............. 246
9.2.3 Concentrated Solar Simulation .................. 249
9.3 Experimental Work Performed with Concentrated Light ... 251
9.3.1 IPV Response to Concentrated Sunlight .......... 251
9.3.2 Polymer Response to Concentrated Light ......... 253
9.3.3 Organic Solar Cell Response to Concentrated
Light .......................................... 257
9.4 Physical Characterization by Concentrated Sunlight .... 261
9.5 Conclusion ............................................ 265
References ................................................. 265
10 Barrier Technology and Applications ........................ 269
Lars Müller-Meskamp, John Fahlteich and Frederik С. Krebs
10.1 Encapsulation Requirements ............................ 269
10.1.1 Types of Encapsulation ......................... 270
10.1.2 Glass/Glass Encapsulation ...................... 271
10.1.3 Lamination of Barrier Films .................... 272
10.1.4 Thin-Film Encapsulation ........................ 273
10.1.5 Perimeter Sealing .............................. 273
10.2 Thin-Film Permeation Physics .......................... 274
10.2.1 Solid-State Diffusion and Diffusion in
Polymers ....................................... 274
10.2.2 Fick's First Law of Diffusion .................. 275
10.2.3 Sorption ....................................... 276
10.2.4 Permeation in Thin Films ....................... 277
10.2.5 Models for the Permeation Barrier Coated
Polymer Films .................................. 278
10.2.6 Temperature Dependence of Permeation ........... 279
10.2.7 Dependence of Water Permeation on Layer
Thickness ...................................... 280
10.2.8 Time Dependence of Permeation .................. 282
10.2.9 Permeation in Multilayer Barriers .............. 284
10.2.10 Pinholes in Multilayer Systems ................ 287
10.3 Measurement of Barrier Properties ..................... 288
10.3.1 Gravimetric Cup ................................ 289
10.3.2 Carrier-Gas-Based Coulometric Barrier
Measurement .................................... 289
10.3.3 Mass Spectrometer .............................. 290
10.3.4 Direct Pressure Measurement .................... 291
10.3.5 Radioactive Isotopes ........................... 292
10.3.6 Calcium Test (Optical or Electrical) ........... 293
10.3.7 Device Testing ................................. 294
10.3.8 Standards and Typical Measurement Conditions ... 295
10.3.9 Test Method Overview ........................... 295
10.4 Barrier Technologies .................................. 295
10.4.1 Single-Layer Technologies ...................... 297
10.4.2 Multilayer Technologies ........................ 309
10.5 Barrier Application in OPV ............................ 315
10.5.1 Products ....................................... 316
10.5.2 Barrier Cost and Manufacturability ............. 318
10.6 Conclusion ............................................ 321
References ............................................ 322
11 Summary and Outlook ........................................ 331
Frederik C. Krebs
Index ......................................................... 333
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