Multiscale Modelling of Organic and Hybrid Photovoltaics (Topics in Current Chemistry Book 352)

The series Topics in Current Chemistry presents critical reviews of the present and future trends in modern chemical research. The scope of coverage is all areas of chemical science including the interfaces with related disciplines such as biology, medicine and materials science. The goal of each thematic volume is to give the non-specialist reader, whether in academia or industry, a comprehensive insight into an area where new research is emerging which is of interest to a larger scientific audience. Each review within the volume critically surveys one aspect of that topic and places it within the context of the volume as a whole. The most significant developments of the last 5 to 10 years are presented using selected examples to illustrate the principles discussed. The coverage is not intended to be an exhaustive summary of the field or include large quantities of data, but should rather be conceptual, concentrating on the methodological thinking that will allow the non-specialist reader to understand the information presented. Contributions also offer an outlook on potential future developments in the field. Review articles for the individual volumes are invited by the volume editors. Readership: research chemists at universities or in industry, graduate students.--Provided by publisher Preface 6 Contents 8 Small Optical Gap Molecules and Polymers: Using Theory to Design More Efficient Materials for Organic Photovoltaics 10 1 Introduction 11 2 Processes Involved in OPV Operation 12 3 Rationale Behind DA Polymers and Molecules 13 4 Application of Quantum-Chemical Methods for DA Copolymers 14 5 Geometric and Electronic Structures and Their Impact on Redox Properties 17 6 Excited-State Properties 20 7 Exciton Migration 28 8 Exciton Dissociation and Charge Separation 28 9 Charge-Carrier Transport 30 10 Charge Collection 31 11 Outlook 31 References 32 Supramolecular Organization of Functional Organic Materials in the Bulk and at Organic/Organic Interfaces: A Modeling and Comp... 48 1 Introduction 50 2 Levels of Modeling 51 2.1 Atomistic Models 53 2.2 Coarse Graining 56 2.3 Simple Empirical Models 60 3 Simulation Techniques and Observables 65 3.1 Simulation Techniques 65 3.1.1 Monte Carlo 65 3.1.2 Molecular Dynamics 68 3.2 Computation of Physical Observables 70 3.3 Timescales of Different Phenomena 74 4 Applications to Bulk Systems and Interfaces 77 4.1 Small Molecules 77 4.1.1 Solid State 78 4.1.2 Liquid Crystal Phases 80 4.2 Polymers 84 4.2.1 Mesoscale Models 87 4.2.2 Atomistic Models 88 4.2.3 Coarse-Grained Models 91 4.3 Interfaces 92 4.3.1 Bulk Heterojunctions 93 4.3.2 Planar Interfaces 95 4.3.3 Organic Crystal Growth 98 5 Conclusions 100 Appendix: Simulation Packages 101 References 104 Electronic and Optical Properties at Organic/Organic Interfaces in Organic Solar Cells 111 1 Introduction 112 2 Computational Methods 115 2.1 Single-Scale Methods 116 2.2 Multi-Scale Methods 120 3 What Can Computations Tell Us? 123 3.1 Band Offsets 123 3.2 Band Bending 125 3.3 Singlet Excited State 136 3.4 Charge Transfer States 139 3.5 Coupling and Rates 141 4 Device Implications 144 4.1 Hot Charge Transfer 146 4.2 Localization/Delocalization 147 4.3 Band Bending 149 5 Conclusion 152 References 154 Modeling Materials and Processes in Dye-Sensitized Solar Cells: Understanding the Mechanism, Improving the Efficiency 159 1 Introduction 160 1.1 Device Functioning and Conversion Efficiency 160 1.2 First Principles DSCs Modeling 164 2 Materials 167 2.1 Dyes 167 2.1.1 Ruthenium Dyes 167 2.1.2 Zinc Porphyrins 169 2.1.3 Organic Dyes 172 2.2 Semiconductor Metal Oxides: TiO2 and ZnO 174 2.2.1 TiO2 Models Relevant for DSCs 174 2.2.2 ZnO Models Relevant to DSCs 180 3 Dye Adsorption on Semiconductor Surfaces 183 3.1 Organic Dyes on TiO2 183 3.1.1 Binding Modes: Theory vs Experiment 183 3.1.2 Effect of Different Anchoring Groups on the Electron Injection/Recombination Dynamics 187 3.2 Ruthenium-Dyes on TiO2 194 3.2.1 N3/N719 Dyes 196 3.2.2 Black Dye 203 3.3 Dye Binding to ZnO: Quantum Size Effect on the DSCs Properties 206 4 Dye Effect on the TiO2 Conduction Band 211 5 Multiple-Dye Adsorption on TiO2: Dye Aggregation and Aggregate Properties 215 5.1 Organic Dyes 216 5.2 Ruthenium Dyes 221 6 Co-sensitization of TiO2 222 6.1 TiO2 Co-sensitized by Different Dyes 222 7 Conclusions 225 References 227 Monte Carlo Studies of Electronic Processes in Dye-Sensitized Solar Cells 245 1 Introduction 246 2 Electrical Transport Models in DSSC 248 3 Monte Carlo Methods and Results 253 3.1 Continuous Time Random Walk Model of Dispersive Transport 254 3.2 MC Models Testing Morphology Dependence of Electron Transport 256 4 Summary, Conclusions, Outlook 262 References 262 Monte Carlo Simulations of Organic Photovoltaics 265 1 Introduction 266 2 Model Implementation 268 3 Losses in OPVs 273 3.1 Geminate Recombination 275 3.1.1 Morphology 275 3.1.2 Energetic Structure at the Donor-Acceptor Interface 278 3.1.3 Delocalization 279 3.1.4 Summary 281 3.2 Non-Geminate Recombination 282 3.2.1 Morphology 282 3.2.2 Transport 283 4 Conclusions 284 References 284 Device Modelling of Organic Bulk Heterojunction Solar Cells 287 1 Introduction 288 1.1 Introducing Organic Bulk Heterojunction Solar Cells 288 1.2 Differential Equations 290 1.3 Equivalent Circuit Models 292 1.4 Approximations Based on the Mobility-Lifetime Product 293 1.5 Trap Free Drift-Diffusion Models 294 1.6 Drift Diffusion Including Localized States 295 1.7 1D Versus 2D Simulations 295 1.8 Monte Carlo Simulations 295 2 Description of Physical Phenomena 297 2.1 Optical Generation 297 2.2 Distribution of Localized States 298 2.3 Transport and Recombination 299 2.4 Doping 300 2.5 Band Diagram and Boundary Conditions 301 2.6 Solving Continuity and Poisson Equation in Steady State 304 2.7 Solving Continuity and Poisson Equation for Transient Simulations 304 3 Experimental Methods Relevant to Device Modelling 305 3.1 Methods to Determine Optical Properties of Layers 305 3.2 Methods to Measure Recombination 306 3.3 Methods to Measure the Density of States 306 3.4 Methods to Measure Transport 307 3.5 Methods to Measure Doping 308 4 Case Studies of the Use of Device Simulation 309 4.1 Current/Voltage Curves 309 4.1.1 The Effect of Diffusion on the Photocurrent in Organic Solar Cells 309 4.1.2 Relation Between the Density of Traps and the Current/Voltage Curve 313 4.2 Space Charge Limited Current Measurements 314 4.3 Transient Measurements 316 4.4 Capacitance/Voltage Measurements 317 4.5 Optical Losses and Parasitic Absorption 318 5 Conclusions 320 Appendix 1: Transfer Matrix Formalism 320 Appendix 2: Shockley-Read-Hall Recombination 322 Appendix 3: Software 324 ASA (Zeman Group, Delft) 324 SCAPS (Burgelman Group, Ghent) 325 References 326 Device Modeling of Dye-Sensitized Solar Cells 333 1 Introduction 334 2 The Electron Subsystem 336 3 The Fundamental Diode Model 337 4 Features of Current-Voltage Curves: Photocurrent and Photovoltage 340 5 Interfaces and Mass Transport 346 6 Energy Disorder in the Semiconductor: Combined Description of Free and Trapped Electrons 352 7 Shift of Conduction Band and Change of Redox Level 357 8 Electron Lifetime 358 9 Trapping Factors in the Kinetic Constants 361 10 Chemical Diffusion Coefficient and Electron Conductivity 367 11 Delocalized Electrons in the Conduction Band 369 12 Diffusion-Recombination in Small Signal Methods 371 13 General Picture of Recombination in a DSC 375 14 Fundamental Factors Determining Rates of Electron Transfer 375 15 Carrier Transfer at Semiconductor/Electrolyte Interface 382 16 Recombination Resistance and Lifetime Models 385 17 Conclusion 393 References 393 Index 404 Front Matter....Pages i-viii Small Optical Gap Molecules and Polymers: Using Theory to Design More Efficient Materials for Organic Photovoltaics....Pages 1-38 Supramolecular Organization of Functional Organic Materials in the Bulk and at Organic/Organic Interfaces: A Modeling and Computer Simulation Approach....Pages 39-101 Electronic and Optical Properties at Organic/Organic Interfaces in Organic Solar Cells....Pages 103-150 Modeling Materials and Processes in Dye-Sensitized Solar Cells: Understanding the Mechanism, Improving the Efficiency....Pages 151-236 Monte Carlo Studies of Electronic Processes in Dye-Sensitized Solar Cells....Pages 237-256 Monte Carlo Simulations of Organic Photovoltaics....Pages 257-278 Device Modelling of Organic Bulk Heterojunction Solar Cells....Pages 279-324 Device Modeling of Dye-Sensitized Solar Cells....Pages 325-395 Back Matter....Pages 397-400