Organic Photovoltaics: Mechanisms, Materials, and Devices

Contents......Page 0
Organic Photovoltaics Mechanisms, Materials, and Devices......Page 6
Foreword 1......Page 9
Foreword 2......Page 10
Preface......Page 12
Acknowledgments......Page 14
Editors......Page 16
Contributors......Page 17
Contents......Page 20
Section 1 General Overviews......Page 23
1.1. THE FIRST SOLID-STATE SOLAR CELL......Page 24
1.3. THE FIRST PRACTICAL APPLICATION OF SILICON SOLAR CELLS......Page 25
1.4. TERRESTRIAL APPLICATIONS......Page 26
1.5. THE FUTURE OF PHOTOVOLTAICS......Page 37
REFERENCES......Page 38
Inorganic Photovoltaic Materials and Devices: Past, Present, and Future......Page 39
2.1.2. Focus: Advanced Materials and Processing......Page 40
2.1.4. Increased Specific Power......Page 41
2.2.3. Amorphous Silicon......Page 42
2.2.4. Gallium Arsenide and Related III–V Materials......Page 43
2.2.5. Thin-Film Materials......Page 44
2.3.1. Multijunction III–V Devices......Page 45
2.3.3. Advanced Processing for Low-Temperature Substrates......Page 47
2.3.4. Concentrator Cells......Page 49
2.3.5. Integrated Power Devices......Page 50
2.4.2. Aerospace......Page 52
2.5. SUMMARY AND CONCLUSIONS......Page 53
REFERENCES......Page 54
Natural Organic Photosynthetic Solar Energy Transduction......Page 57
3.2. PHOTOSYNTHESIS IS A SOLAR ENERGY STORAGE PROCESS......Page 58
3.4. PHOTOSYNTHETIC PIGMENTS......Page 59
3.6. ANTENNAS AND ENERGY TRANSFER PROCESSES......Page 61
3.7. PRIMARY ELECTRON TRANSFER IN REACTION CENTERS......Page 64
3.9. CONCLUSIONS......Page 67
REFERENCES......Page 68
Solid-State Organic Photovoltaics: A Review of Molecular and Polymeric Devices......Page 69
4.1.2. Device Characterization......Page 70
4.2.1. Organic Heterojunction Solar Cells......Page 73
4.2.2. Molecular OPVs with Bulk Heterojunctions......Page 76
4.2.3. High-Efficiency Molecular OPVs with Exciton Blocking Layers......Page 80
4.2.4. Open-Circuit Voltage and Tandem Solar Cells......Page 84
4.3.1. Single-Layer Polymer Devices......Page 86
4.3.2. Polymer–Dye Solar Cells......Page 88
4.3.3. Polymer Blend and Multilayer Solar Cells......Page 96
4.4.1. Polymer–Quantum Dot Devices......Page 105
4.4.2. Polymer-Sensitized TiO2......Page 109
4.4.3. Solid State Dye-Sensitized Solar Cells......Page 114
4.5. CONCLUDING REMARKS......Page 116
REFERENCES......Page 117
Section 2 Mechanisms and Modeling......Page 125
Simulations of Optical Processes in Organic Photovoltaic Devices......Page 126
5.1. INTRODUCTION......Page 127
5.2.1. Incoupling of the Photon......Page 129
5.2.3. Exciton Formation......Page 130
5.2.6. Charge Transport......Page 131
5.3. ROUTES TO OPTICAL MODELS OF PPVDs......Page 132
5.4.1. General Assumptions......Page 133
5.4.2. Derivation — the Stack Model......Page 134
5.4.3. Taking Into Account the Substrate......Page 139
5.4.5. Efficiencies......Page 141
5.5. SIMULATIONS AND RESULTS......Page 142
5.5.2. Q-Profile for Different Wavelengths......Page 146
5.5.4. Polychromatic Q-Profile......Page 147
5.5.5.1. Optimizing the Double Layer Structure......Page 149
5.5.5.2. Optimizing the Blend Layer Structure......Page 150
5.5.7.1. Optical Power Efficiency......Page 152
5.5.8. Energy Redistribution......Page 153
5.6. SUMMARY......Page 154
REFERENCES......Page 155
Coulomb Forces in Excitonic Solar Cells......Page 158
6.1.1. Differences Between Conventional and Excitonic Semiconductors......Page 159
6.1.2. Characteristics of Excitonic Semiconductors......Page 160
6.2. CHARGE CARRIER PHOTOGENERATION IN CSCs AND XSCs......Page 161
6.2.1. Forces and Fluxes in XSCs......Page 162
6.2.2. The Chemical Potential Energy Gradient in XSCs......Page 163
6.3. DOPING OSCs......Page 164
6.3.2. Purposely Doped Perylene Diimide Films......Page 165
6.3.3. Superlinear Increase in Conductivity with Doping Density......Page 166
6.3.4. No Shallow Dopants in XSCs......Page 169
6.4.2. Adventitiously Doped XSCs......Page 170
6.4.3. The Poole–Frenkel Mechanism......Page 171
6.4.4. Space Charge Limited Currents......Page 173
6.4.5. Field-Dependent Carrier Mobilities......Page 175
6.5. SUMMARY......Page 176
REFERENCES......Page 177
Electronic Structure of Organic Photovoltaic Materials: Modeling of Exciton- Dissociation and Charge- Recombination Processes......Page 179
7.1. INTRODUCTION......Page 180
7.2. THE FAILURE OF THE STATIC VIEW......Page 181
7.3. THEORETICAL APPROACH......Page 183
7.4. DYNAMICAL ASPECTS......Page 187
7.5.1. Specifically Designed Supramolecular Architectures......Page 191
7.5.2. Donor–Bridge–Acceptor Architectures......Page 192
7.5.3. Symmetry Effects......Page 193
7.5.4. Low-Bandgap Polymers......Page 195
ACKNOWLEDGMENTS......Page 196
REFERENCES......Page 197
Optimization of Organic Solar Cells in Both Space and Energy – Time Domains......Page 201
8.1. INTRODUCTION......Page 202
8.2. FUNDAMENTALS AND CURRENT PROBLEMS OF ORGANIC PHOTOVOLTAICS......Page 203
8.2.1. Photon Absorption and Exciton Generation......Page 206
8.2.4. Carrier Diffusion to the Electrodes......Page 207
8.2.5. Carrier Collection at the Electrodes......Page 208
8.3.1. Block Copolymers and Self-Assembled Supramolecular Nanostructures......Page 209
8.3.2. Design and Development of a –DBAB- Type Block Copolymer for a ‘‘Tertiary’’ Supramolecular Nanostructure......Page 210
8.3.3. Materials and Equipment, Experimental......Page 214
8.3.4. Results and Discussion on Spatial Domain Optimization......Page 216
8.4.1. Background......Page 221
8.4.2. Formulation......Page 222
8.4.3. Results and Discussion......Page 224
8.5. CONCLUSIONS AND FUTURE PERSPECTIVES......Page 229
REFERENCES......Page 230
Section 3 Materials and Devices......Page 233
9.1. INTRODUCTION......Page 234
9.2. PHOTOINDUCED ELECTRON TRANSFER FROM CONJUGATED POLYMERS ONTO FULLERENES......Page 235
9.3. THE BULK HETEROJUNCTION CONCEPT......Page 237
9.4. METAL–INSULATOR–METAL (MIM) PICTURE......Page 240
9.5. BILAYER HETEROJUNCTION DEVICES......Page 242
9.6. BULK HETEROJUNCTION DEVICES......Page 243
9.7. THE OPEN CIRCUIT POTENTIAL,......Page 245
9.8. DOUBLE CABLE POLYMERS......Page 248
REFERENCES......Page 249
Organic Solar Cells Incorporating a p–i–n Junction and a p – n Homojunction......Page 255
10.1. INTRODUCTION......Page 256
10.2.2. Direct Heteromolecular Contact as a Photocarrier Generation Site......Page 257
10.2.3. Three-Layered Cells......Page 260
10.2.4. p–i–n Energy Structure......Page 262
10.2.5. Application of Inorganic Semiconductors to the n-Type Layer......Page 265
10.2.6. Sensitization Mechanism of Photocarrier Generation at Heteromolecular Contacts......Page 266
10.3.2. Photovoltaic Properties vs. Substrate Temperature......Page 268
10.3.3. Nanostructure vs. Substrate Temperature......Page 269
10.3.4. Photocurrent Generation in Co-Deposited Films......Page 271
10.3.5. Three-Layered Cells Incorporating Crystalline–Amorphous Nanocomposite Films......Page 272
10.4.1. Motivation......Page 275
10.4.2. Efficient Purification by Reactive Sublimation......Page 276
10.4.3. pn-Control of a Single Organic Semiconductor by Doping......Page 278
10.4.4. p–n Homojunction in Perylene Pigment Film......Page 282
10.5. CONCLUSION......Page 284
REFERENCES......Page 285
Liquid-Crystal Approaches to Organic Photovoltaics......Page 287
11.1. INTRODUCTION......Page 288
11.2. MODELING OF SOLAR CELLS......Page 290
11.3. TRANSPORT IN ORGANIC SEMICONDUCTORS......Page 292
11.3.1. Disorder Formalism for Transport in Amorphous Materials......Page 293
11.3.2. Mobility Measurement Techniques......Page 294
11.4.1. Fundamentals of Liquid Crystals......Page 298
11.4.2. Transport in Liquid Crystals......Page 300
11.4.3. Supramolecular Architectures......Page 305
11.5. OVERVIEW OF LIQUID-CRYSTAL-BASED PHOTOVOLTAIC CELLS......Page 306
11.6. CONCLUSION......Page 309
REFERENCES......Page 310
12.1. INTRODUCTION......Page 314
12.2. NANOPOROUS TITANIA FILMS......Page 316
12.3. FILLING NANOPORES WITH CONJUGATED POLYMERS......Page 317
12.4.1. Photovoltaic Cells with Non-Interpenetrating Semiconductors......Page 320
12.4.2. Interpenetrating Polymer–Titania Nanostructures......Page 322
12.5. FUTURE OUTLOOK......Page 324
REFERENCES......Page 325
Solar Cells Based on Cyanine and Polymethine Dyes......Page 328
13.2.1. Cyanine Dyes......Page 329
13.2.2. Hemicyanine Dyes......Page 332
13.2.3. Merocyanine Dyes......Page 335
13.2.4. Other Polymethine Dyes......Page 336
13.3. THIN FILM HETEROJUNCTION PHOTOVOLTAIC DEVICES......Page 339
13.4. FUTURE PROSPECTS......Page 340
REFERENCES......Page 342
Semiconductor Quantum Dot Based Nanocomposite Solar Cells......Page 345
14.1. INTRODUCTION......Page 346
14.2. QUANTUM DOT–ORGANIC POLYMER COMPOSITE SOLAR CELLS......Page 349
14.2.1. Published Results......Page 350
14.2.2. Power Conversion in Quantum Dot–Polymer Composite Solar Cells......Page 351
14.3.1. Introduction......Page 355
14.3.2. Issues Concerning Materials Used as QDSSCs......Page 357
14.3.3. Challenges in Materials and Device Development......Page 358
14.4. CONCLUSION......Page 359
REFERENCES......Page 360
Solar Cells Based on Composites of Donor Conjugated Polymers and Carbon Nanotubes......Page 365
15.1. INTRODUCTION......Page 366
15.3. CURRENT–VOLTAGE CHARACTERISTICS......Page 370
15.3.1. Light Intensity Dependence Measurements......Page 372
15.3.2. Open Circuit Voltage......Page 374
15.4. NANOTUBE CONCENTRATION DEPENDENCE......Page 375
15.5. FUTURE DIRECTIONS......Page 377
REFERENCES......Page 378
Photovoltaic Devices Based on Polythiophene/ C60......Page 380
16.2. ORGANIC PHOTOVOLTAIC DEVICES......Page 381
16.3. BILAYERS OF POLYTHIOPHENES/ C60......Page 384
16.3.1. Optical Modeling of PEOPT/ C60 Devices......Page 385
16.3.2. Electrical Transport in PEOPT/ C60 Diodes in Dark......Page 387
16.3.3. Electrical Transport in PEOPT/ C60 Photodiodes under Illumination......Page 389
16.4. BLENDS OF POLYTHIOPHENES/ C60......Page 391
16.5. CONCLUSIONS......Page 396
REFERENCES......Page 397
17.1. INTRODUCTION......Page 400
17.2.1. Chemical Synthesis......Page 403
17.3. ALTERNATING POLYFLUORENE COPOLYMERS: ELECTRONIC STRUCTURE AND OPTICAL ABSORPTION......Page 404
17.3.1. Optical Transitions and Electronic Structure......Page 405
17.4. ELECTRONIC TRANSPORT IN APFOs......Page 406
17.5. POLYFLUORENE–FULLERENE BLENDS: MORPHOLOGY AND OPTICAL PROPERTIES......Page 408
17.6. POLYFLUORENE–FULLERENE BLENDS IN DEVICES: PERFORMANCE......Page 410
17.6.1. Temperature Dependence of Photovoltaic Device Performance......Page 411
REFERENCES......Page 413
Solar Cells Based on Diblock Copolymers: A PPV Donor Block and a Fullerene Derivatized Acceptor Block......Page 416
18.1. INTRODUCTION......Page 417
18.1.1 Microphase Separation of Block Copolymers......Page 418
18.2.1. Synthesis of Diblock Rod–Coil Copolymers: General Aspects......Page 420
18.2.2. Synthesis of PPV Macroinitiator......Page 421
18.2.3. Polymerization with the PPV Macroinitiator and Functionalization of the Coil Block......Page 422
18.3. PHASE BEHAVIOR OF THE PPV-BASED DIBLOCK COPOLYMERS......Page 424
18.3.1. Aggregation of PPV-b-PS Diblock Copolymers in Solution......Page 425
18.3.2. Self Organization of PPV-based Block Copolymers in Thin Films......Page 426
18.4. PHOTOVOLTAIC RESPONSE OF THE DONOR–ACCEPTOR BLOCK COPOLYMER......Page 428
18.5. CONCLUSIONS AND OUTLOOK......Page 430
REFERENCES......Page 431
Interface Electronic Structure and Organic Photovoltaic Devices......Page 434
19.1. INTRODUCTION......Page 435
19.2. SYMMETRY OF METAL–ORGANIC INTERFACES: PENTACENE WITH Au, Ag, AND Ca......Page 437
19.3. MECHANISMS OF INTERFACE DIPOLE FORMATION......Page 440
19.4. DOPING AND ENERGY LEVEL SHIFT: Cs IN CuPc......Page 442
19.5. INTERFACE ENGINEERING IN OSCs: LiF......Page 445
19.6. ITO SURFACE TREATMENT AND ITS INTERFACE WITH ORGANIC: NPB/ITO......Page 448
19.7. ORGANIC–ORGANIC INTERFACE: NPB AND Alq3......Page 452
19.8. DYNAMICS OF INTERFACE CHARGE TRANSFER: TPD AND DPEP......Page 456
ACKNOWLEDGMENTS......Page 461
REFERENCES......Page 462
The Influence of the Electrode Choice on the Performance of Organic Solar Cells......Page 465
20.1. INTRODUCTION......Page 466
20.2. CRITERIA FOR ELECTRODE CHOICE......Page 467
20.2.2. Heterojunction Solar Cells......Page 468
20.2.2. Dye-Sensitized Solar Cells......Page 469
20.3. COMMONLY USED ANODES......Page 470
20.3.1. Indium Tin Oxide......Page 471
20.3.3. Polyaniline/ITO and Self-Assembled Monolayers on ITO......Page 480
20.4.1. Single Layer Metal Cathode......Page 481
20.4.3. BCP/Ag and BCP/Al......Page 482
20.5. CONCLUSIONS......Page 483
REFERENCES......Page 484
Conducting and Transparent Polymer Electrodes......Page 490
21.1. INTRODUCTION......Page 491
21.2. PROPERTIES OF PEDOT–PSS......Page 492
21.2.2. The Optical Properties of PEDOT–PSS Film......Page 493
21.2.3. Processing and Patterning......Page 494
21.3.1. PEDOT–PSS Used as a Buffer Layer......Page 496
21.3.2. PEDOT–PSS as an Electrode in Polymer PVDs......Page 499
ACKNOWLEDGMENT......Page 501
REFERENCES......Page 502
Progress in Optically Transparent Conducting Polymers......Page 506
22.1. INTRODUCTION......Page 507
22.2.1. Polymers with Electron-Rich Moieties......Page 508
22.2.2. Polymers Containing Electron-Withdrawing Repeat Units......Page 514
22.2.3. Fused Aromatics as Repeat Units......Page 516
22.2.4. Arylvinylenes and Arylmethines......Page 522
22.2.5. Donor–Acceptor Type Polymers......Page 526
22.3. CONCLUSIONS......Page 533
REFERENCES......Page 534
Optoelectronic Properties of Conjugated Polymer/ Fullerene Binary Pairs with Variety of LUMO Level Differences......Page 539
23.1. INTRODUCTION......Page 540
23.2.2. Regioregular P3ATs as Electron Donors......Page 543
23.2.2.1. Electrochemical Properties of Poly(3-alkylthiophene)s......Page 544
23.2.2.3. Photoinduced Electron Transfer in P3AT/Fullerene Systems......Page 545
23.2.2.4. Photovoltaic Devices Based on P3ATs/PCBM......Page 549
23.2.2.5. Summary of P3ATs/Fullerene Systems......Page 552
23.2.3.1. Electrochemical Properties of MDMO-PPV, DE69, and DE21......Page 553
23.2.3.2. Optical Properties of MDMO-PPV, DE69, and DE21......Page 554
23.2.3.3. Photoinduced Electron Transfer in MDMO-PPV, DE69,......Page 555
23.2.3.4. Photovoltaic Devices Based on MDMO-PPV/PCBM, DE69/PCBM,......Page 561
23.2.3.5. Summary of MDMO-PPV/PCBM and PPE–PPV/PCBM Systems......Page 563
REFERENCES......Page 564
Polymer–Fullerene Concentration Gradient Photovoltaic Devices by Thermally Controlled Interdiffusion......Page 568
24.1. INTRODUCTION......Page 569
24.3. MEH-PPV/ C60 DEVICES......Page 570
24.3.1. Thermally Controlled Interdiffusion......Page 571
24.3.2. Dependence on MEH-PPV Thickness......Page 575
24.3.3. In situ Observation of Interdiffusion......Page 578
24.3.4. Morphology of the Interdiffused Devices......Page 579
24.4. P3OT/ C60 DEVICES......Page 581
24.5. SUMMARY......Page 584
ACKNOWLEDGMENTS......Page 585
REFERENCES......Page 586
Vertically Aligned Carbon Nanotubes for Organic Photovoltaic Devices......Page 587
25.1. INTRODUCTION......Page 588
25.2. POLYMER/CARBON NANOTUBE SOLAR CELLS......Page 591
25.3. VERTICALLY ALIGNED CARBON NANOTUBES FOR OPTOELECTRONIC APPLICATIONS......Page 594
25.4. NANO-ENGINEERING FOR THE FUTURE......Page 598
25.5. CONCLUSION......Page 600
REFERENCES......Page 601