Organic Photovoltaics: Mechanisms, Materials, and Devices (Optical Science and Engineering)

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

Recently developed organic photovoltaics (OPVs) show distinct advantages over their inorganic counterparts due to their lighter weight, flexible shape, versatile materials synthesis and device fabrication schemes, and low cost in large-scale industrial production. Although many books currently exist on general concepts of PV and inorganic PV materials and devices, few are available that offer a comprehensive overview of recently fast developing organic and polymeric PV materials and devices.

Organic Photovoltaics: Mechanisms, Materials, and Devices fills this gap. The book provides an international perspective on the latest research in this rapidly expanding field with contributions from top experts around the world. It presents a unified approach comprising three sections: General Overviews; Mechanisms and Modeling; and Materials and Devices. Discussions include sunlight capture, exciton diffusion and dissociation, interface properties, charge recombination and migration, and a variety of currently developing OPV materials/devices. The book also includes two forewords: one by Nobel Laureate Dr. Alan J. Heeger, and the other by Drs. Aloysius Hepp and Sheila Bailey of NASA Glenn Research Center.

Organic Photovoltaics equips students, researchers, and engineers with knowledge of the mechanisms, materials, devices, and applications of OPVs necessary to develop cheaper, lighter, and cleaner renewable energy throughout the coming decades.

"Organic Photovoltaics: Mechanisms, Materials, and Devices provides an international perspective on the latest research in the rapidly expanding field of organic and polymeric PV materials with contributions from top experts around the world. It presents a unified approach comprising three sections: General Overviews; Mechanisms and Modeling; and Materials and Devices. Discussions include sunlight capture, exciton diffusion and dissociation, interface properties, charge recombination and migration, and a variety of currently developing OPV materials/devices. Twenty tables, nearly 400 figures (18 in color), and over 1400 references complement the material." "This invaluable, authoritative reference: provides a comprehensive, unified survey of the background, current research, and applications of organic and polymeric photovoltaic devices; contains nearly 400 figures and contributions from international experts; directs students, researchers, and designers to the next generation of clean, renewable energy production; and offers a look at emerging technologies and a discussion of future directions from an industry expert." "Organic Photovoltaics equips students, researchers, and engineers with knowledge of the mechanisms, materials, devices, and applications of OPVs necessary to develop cheaper, lighter, and cleaner renewable energy throughout the coming decades."--Jacket. The book provides an international perspective on the latest research in this rapidly expanding field with contributions from top experts around the world. It presents a unified approach comprising three sections : General Overviews; Mechanisms and Modeling; and Materials and Devices. Discussions include sunlight capture, exciton diffusion and dissociation, interface properties, charge recombination and migration, and a variety of currently developing OPV materials/devices. The book also includes two forewords : one by Nobel Laureate Dr. Alan J. Heeger, and the other by Drs. Aloysius Hepp and Sheila Bailey of NASA Glenn Research Center. Organic Photovoltaics equips students, researchers, and engineers with knowledge of the mechanisms, materials, devices, and applications of OPVs necessary to develop cheaper, lighter, and cleaner renewable energy throughout the coming decades. (Midwest)