Preface .......................................................... xvii
Part 1 Current Developments ........................................ 1
1 Design Considerations for Efficient and Stable Polymer
Solar Cells .................................................... 3
Prajwal Adhikary, Jing Li, and Qiquan Qiao
1.1 Introduction ................................................... 4
1.1.1 Background .............................................. 4
1.1.2 Theory .................................................. 6
1.1.2.1 Photovoltaic Processes in Donor-Acceptor (D-A)
System .............................................. 7
1.1.2.2 Equivalent Circuit Diagram of a PV Cell under
Illumination ........................................ 9
1.1.2.3 Parameters Governing Performance of Solar Cells ..... 9
1.2 Role of Interfacial Layer for Efficient BHJ Solar Cells ....... 11
1.2.1 Role of Interfacial Layer on Voc ....................... 12
1.2.2 Influence on Active Layer Vertical Morphology
Based on underneath Interfacial Layer .................. 14
1.2.3 Light Trapping Strategies and Plasmonic Effects for
Efficient Light Harvesting ............................. 16
1.2.4 Morphology Control of Active Layer and ETL by
Processing ............................................. 19
1.3 Selection of Interfacial Layer for Stable and Longer
Lifetime ...................................................... 20
1.3.1 Stability of Active Layer Materials .................... 21
1.3.2 Stability of Metal Electrodes .......................... 23
1.3.3 Stability of Transparent Electrode ..................... 23
1.3.1 Stability by Electron Transport Layers (ETLs) .......... 24
1.3.5 Stability by Hole Transport Layers (HTLs) .............. 25
1.4 Materials Used as Interfacial Layer ........................... 26
1.4.1 Conventional Solar Cell Devices ........................ 26
1.4.1.1 Cathode and Electron Transport Layers .............. 26
1.4.1.2 Anode and Hole Transport Layers .................... 28
1.4.2 Inverted Device Structure .............................. 31
1.4.2.1 Cathode and Electron Transport Layers .............. 31
1.4.2.2 Anode and Hole Transport Layers .................... 33
1.5 Conclusion and Outlook ........................................ 34
Acknowledgement ............................................... 34
References .................................................... 35
Carbazole-Based Organic Dyes for Dye-Sensitized Solar Cells: Role
of Carbazole as Donor, Auxiliary Donor and π-linker ................ 41
A. Venkateswararao and K.R. Justin Thomas
2.1 Introduction .................................................. 42
2.2 Carbazole as a Donor for Dye-Sensitized Solar Cells ........... 44
2.2.1 Carbazole as Donor via C3-Position ..................... 45
2.2.2 Carbazole as Donor and Linked through N9-position ...... 60
2.3 Carbazole as a π-Linker ....................................... 64
2.3.1 Carbazole as a Bridge via C2, C7 Positions ............. 65
2.3.2 Carbazole as a Linker via C3, C6 Positions ............. 67
2.4 Carbazole as Auxiliary Donor for DSSC ......................... 75
2.4.1 Carbazole as Auxiliary Donor via C2-position ........... 76
2.4.2 Carbazole as Auxiliary Donor via C3-Position ........... 77
2.4.3 Carbazole as Auxiliary Donor via N9-Position ........... 80
2.4.4 Carbazole as Auxiliary Donor via C3, С6-positions ...... 87
2.5 Carbazole as Donor as Well as Linker for DSSC ................. 87
2.6 Conclusion and Outlook ........................................ 91
Acknowledgements .............................................. 92
References .................................................... 92
3 Colloidal Synthesis of CuInS2 and CuInSe2 Nanocrystals
for Photovoltaic Applications ................................. 97
Joanna Kolny-Olesiak
3.1 Introduction .................................................. 97
3.2 Synthesis of CuInS2 and CuInSe2 Nanocrystals .................. 99
3.2.1 Ligand Shell and Colloidal Stability .................. 100
3.2.2 Adjusting the Reactivity of the Precursors ............ 102
3.2.3 Shape Control ......................................... 103
3.2.4 Crystallographic Structure ............................ 106
3.2.5 Composition ........................................... 107
3.3 Application of Colloidal CuInS2 and CuInSe2 Nanoparticles
in Solar Energy Conversion ................................... 109
3.3.1 All-Inorganic Solar Cells ............................. 109
3.3.2 Organic-Inorganic Hybrid Solar Cells .................. 110
3.3.3 Nanocrystal Sensitized Solar Cells .................... 111
3.4 Conclusion and Outlook ....................................... 112
References ................................................... 112
4 Two Dimensional Layered Semiconductors: Emerging Materials
for Solar Photovoltaics ...................................... 117
Mariyappan Shanmugam and Bin Yu
4.1 Introduction ................................................. 118
4.2 Material Synthesis ........................................... 119
4.2.1 Chemical Exfoliation .................................. 119
4.2.2 CVD Synthesis of 2D Layered Semiconductors
MoS2 and WS2 .......................................... 120
4.2.3 Material Characterization ............................. 122
4.3 Photovoltaic Device Fabrication .............................. 122
4.3.1 Bulk Heterojunction Solar Cells ....................... 122
4.3.2 Schottky Barrier Solar Cells .......................... 122
4.3.3 Device Characterization ............................... 123
4.4 Microstructural and Raman Spectroscopic Studies of
MoS2 and WS2 ................................................. 124
4.5 Photovoltaic Performance Evaluation .......................... 126
4.5.1 BHJ Solar Cells ....................................... 126
4.5.2 Schottky Barrier Solar Cells .......................... 127
4.6 Electronic Transport and Interfacial Recombination ........... 129
4.6.1 BHJ Solar Cells ....................................... 129
4.6.2 Schottky Barrier Solar Cells .......................... 131
4.7 Conclusion and Outlook ....................................... 132
References ................................................... 133
5 Control of ZnO Nanorods for Polymer Solar Cells .............. 135
Hsin-Yi Chen, Ching-Fuh Lin
5.1 Introduction ................................................. 136
5.2 Preparation and Characterization of ZnO NRs .................. 137
5.2.1 ZnO NRs Prepared by Hydrothermal Method ............... 137
5.2.1.1 Control of HMT and Zn(NO3)2 ....................... 138
5.2.1.2 Control of Seed Layer Synthesis and Heating
Temperature ....................................... 140
5.2.2 Morphology Control of ZnO NRs ......................... 144
5.2.3 Summary of ZnO NR Growth .............................. 146
5.3 Application of ZnO NR in Polymer Solar Cells ................. 147
5.3.1 ZnO-NR/Polymer Solar Cells Based on Vertically-
Aligned Zno NRs ....................................... 148
5.3.2 ZnO NR as a Cathode Buffer Layer in Polymer Solar
Cells ................................................. 150
5.4 Conclusion and Outlook ....................................... 154
References ................................................... 154
Part 2 Noble Approaches .......................................... 159
6 Dye-Sensitized Solar Cells ................................... 161
Lakshmi V. Munukutla, Aung Htun, Sailaja Radhakrishanan,
Laura Main, and Arunachala M. Kannan
6.1 Introduction ................................................. 161
6.2 Background ................................................... 163
6.2.1 DSCC Operation Principle .............................. 164
6.2.2 DSSC Structure ........................................ 166
6.2.3 DSSC Challenges ....................................... 168
6.2.4 DSSC Components ....................................... 168
6.2.4.1 Working Electrode ................................. 168
6.2.4.2 Dye Sensitizer .................................... 169
6.2.4.3 Electrolyte ....................................... 170
6.2.4.4 Platinum-Coated Counter Electrode ................. 171
6.2.4.5 Equivalent Circuit of DSSC ........................ 172
6.3 DSSC Key Performance Parameters .............................. 173
6.4 Device Improvements .......................................... 174
6.4.1 Experimental .......................................... 175
6.4.1.1 Working Electrode Preparation ..................... 175
6.4.1.2 Cell Assembly ..................................... 175
6.4.1.3 Electrolyte Injection ............................. 176
6.4.2 DSSC Performance Results .............................. 176
6.4.2.1 ТIO2 Film Thickness Optimization .................. 176
6.4.2.2 Optimization of Nanoparticle Size in ТIO2 ......... 178
6.4.2.3 Scaling Down the DSS Cell Size .................... 180
6.5 DSSC Performance with Different Electrolytes ................. 180
6.5.1 Liquid Electrolyte .................................... 180
6.5.2 Quasi-Solid Electrolyte ............................... 181
6.6 Conclusion and Outlook ....................................... 183
References ................................................... 183
7 Nanoimprint Lithography for Photovoltaic Applications ........ 185
Benjamin Schumm and Stefan Kaskel
7.1 Introduction ................................................. 186
7.2 Soft Lithography ............................................. 186
7.2.1 Soft Lithography Methods .............................. 186
7.2.2 Stamp Materials Used for Nanoimprint Lithography ...... 188
7.3 NIL-Based Techniques for PV .................................. 190
7.3.1 Antireflection Layers Prepared with NIL Methods ....... 190
7.3.1.1 Structured Substrates - Outside ................... 191
7.3.1.2 Structured Wafers ................................. 191
7.3.1.3 Structured Substrates - Inside .................... 192
7.3.2 NIL-Patterned Films as Etching Masks .................. 193
7.3.3 NIL for Organic Solar Cell Processing ................. 194
7.3.4 Plasmonic Films Prepared with NIL Methods ............. 196
7.3.5 Up-Scaling Potential of NIL Processes ................. 197
7.4 Conclusion and Outlook ....................................... 198
References ................................................... 199
8 Indoor Photovoltaics: Efficiencies, Measurements and Design .. 203
Monika Freunek (Müller)
8.1 Introduction ................................................. 203
8.2 Indoor Radiation ............................................. 205
8.2.1 Spectra and Intensities ............................... 205
8.3 Maximum Efficiencies ......................................... 208
8.3.1 Maximum Indoor Efficiencies and Ideal Materials ....... 208
8.3.2 Monochromatic Radiation ............................... 209
8.3.3 Intensity Effects ..................................... 211
8.4 Optimization Strategies ...................................... 213
8.5 Characterization and Measured Efficiencies ................... 216
8.6 Irradiance Measurements ...................................... 217
8.7 Characterization ............................................. 217
8.8 Conclusion and Outlook ....................................... 219
References ................................................... 221
9 Photon Management in Rare Earth Doped Nanomaterials for
Solar Cells .................................................. 223
Jiajia Zhou, Jianrong Qiu
9.1 Introduction ................................................. 223
9.2 Basic Aspects of Solar Cell .................................. 224
9.2.1 Mechanism of Efficiency Limitation .................... 224
9.2.2 EQEs of Solar Cells ................................... 225
9.2.3 Photon Management Approaches to Enhance the
Efficiency of Solar Cell .............................. 227
9.3 Up-Con version Nanomaterials for Solar Cell Application ...... 228
9.3.1 Principles of Photon Up-Conversion .................... 228
9.3.2 Spectroscopy Analysis and Application Demonstration ... 229
9.4 Down-Conversion Nanomaterials for Solar Cell Application ..... 232
9.4.1 Principles of Photon Down-Conversion .................. 232
9.4.2 Experimental and Spectroscopy Analysis ................ 233
9.4.3 Evaluation ............................................ 235
9.5 Conclusion and Outlook ....................................... 236
9.5.1 Solution-Processable Nano-Coating for Broadband
Up-Converter or Down-Converter ........................ 237
9.5.2 Efficient Photon Management Using Nanoplasmonic
Effect ................................................ 238
References ................................................... 238
Part 3 Developments in Prospective ............................... 241
10 Advances in Plasmonic Light Trapping in Thin-Film Solar
Photovoltaic Devices ......................................... 243
/. Gwamuri, D. Ö. Güney, and J. M. Pearce
10.1 Introduction ................................................. 244
10.1.1 Plasmonics Basics ..................................... 245
10.1.2 Metamaterials ......................................... 246
10.2 Theoretical Approaches to Plasmonic Light Trapping
Mechanisms in Thin-film PV ................................... 247
10.2.1 Optimal Cell Geometry Modeling ........................ 248
10.2.2 Optical Properties Simulations ........................ 250
10.2.3 Electrical Properties Simulations ..................... 255
10.3 Plasmonics for Improved Photovoltaic Cells Optical
Properties ................................................... 256
10.3.1 Light Trapping in Bulk Si Solar Cells ................. 256
10.3.2 Plasmonic Light-Trapping Mechanisms for Thin-Film PV
Devices ............................................... 257
10.3.3 Experimental Results .................................. 260
10.4 Fabrication Techniques and Economics ......................... 260
10.4.1 Lithography Nanofabrication Techniques ................ 260
10.4.2 Physical/Chemical Processing Techniques ............... 263
10.5 Conclusion and Outlook ....................................... 263
Acknowledgements ............................................. 266
References ................................................... 266
11 Recent Research and Development of Luminescent Solar
Concentrators ................................................ 271
Yun Seng Lint, Shin Yiing Kee, and Chin Kim Lo
11.1 Introduction ................................................. 272
11.2 Mechanisms of Power Losses in Luminescent Solar
Concentrator ................................................. 274
11.3 Modeling ..................................................... 276
11.3.1 Thermodynamic Modeling ................................ 276
11.3.2 Ray Tracing Modeling .................................. 277
11.3.3 Hybrid of Thermodynamic and Ray-Tracing Method ........ 278
11.3.4 Monte Carlo Simulations ............................... 279
11.4 Polymer Materials ............................................ 279
11.5 Luminescent Materials for Luminescent Solar Concentrator ..... 280
11.5.1 Organic Dyes in LSC ................................... 280
11.5.2 Quantum Dots .......................................... 283
11.5.3 Rare Earth ............................................ 285
11.5.4 Semiconducting Polymer ................................ 286
11.6 New Designs of Luminescent Solar Concentrator ................ 286
11.7 Conclusion and Outlook ....................................... 287
References ................................................... 289
12 Luminescent Solar Concentrators - State of the Art
and Future Perspectives ...................................... 293
M. Tonezzer, D. Gutierrez, and D. Vincenzi
12.1 Introduction to the Third Generation of Photovoltaic
Systems ...................................................... 294
12.2 Luminescence Solar Concentrators (LSCs) ...................... 294
12.2.1 Description of LSC Devices ............................ 294
12.2.2 The Efficiency and Losses Mechanism in LSC Devices .... 295
12.3 Components of LSC Devices .................................... 299
12.3.1 Waveguide Slab ........................................ 300
12.3.2 Fluorophore ........................................... 301
12.3.2.1 Organic Fluorescent Dyes .......................... 301
12.3.2.2 Quantum Dots ...................................... 303
12.3.2.3 Rare-Earth Materials .............................. 305
12.3.3 Solar Cells ........................................... 306
12.3.4 Experimental Results .................................. 307
12.4 Pathways for Improving LSC Efficiency ........................ 308
12.4.1 Escape-Cone losses (PTIR) ............................. 308
12.4.2 Absorption Losses ..................................... 309
12.4.3 Self Absorption Losses ................................ 310
12.5 Conclusion and Outlook ....................................... 311
Acknowledgments .............................................. 312
References ................................................... 312
13 Organic Fluorophores for Luminescent Solar Concentrators ..... 317
Luca Beverina and Alessandro Sanguineti
13.1 Introduction ................................................. 318
13.2 LSCs: Device Operation and Main Features ..................... 321
13.3 Luminophores in LSCs ......................................... 324
13.3.1 Colloidal Quantum Dots (QDs) .......................... 325
13.3.2 Luminescent Lanthanides Chelates ...................... 327
13.3.3 Organic Dyes .......................................... 333
13.4 Conclusion and Outlook ....................................... 349
References ................................................... 351
14 PAn-Graphene-Nanoribbon Composite Materials for Organic
Photovoltaics: A DFT Study of Their Electronic and Charge
Transport Properties ......................................... 357
Javed Mazher, Asefa A. Desta, and Shabina Khan
14.1 Introduction ................................................. 358
14.1.1 Organic Photovoltaic Technology ....................... 359
14.1.2 Bulk Heterojunction Solar Cells ....................... 362
14.1.3 Conjugated Polymers: Polyaniline (PAn) ................ 365
14.1.4 Carbon Nanostructure: Graphene ........................ 367
14.1.5 Graphene Nanoribbons (GNRs) ........................... 372
14.1.5.1 Types of Graphene Nanoribbons ..................... 372
14.1.6 Nanocomposites and Their Percolation: GNR-
Polyaniline Composites ................................ 374
14.1.7 Origin of an Equilibrium Conductance in
Nanodevices ........................................... 376
14.1.8 Singularities Due to the Quantum Confinement of
Nanostructures ........................................ 378
14.2 Review of Computational Background ........................... 379
14.2.1 Modern Theoretical Methods: Ab-initio Nanocomposite
Theory ................................................ 379
14.2.2 Density Functional Theory (DFT) ....................... 380
14.2.3 Nonequilibrium Green's Function (NEGF) ................ 384
14.3 Atomistic Computational Simulations: Modeling and
Methodology .................................................. 385
14.3.1 Atomistix Toolkit (ATK): Ab-initio DFT Software
Package for Nanosystems ............................... 385
14.3.2 Nanodevice Characteristics Simulation: PAn and
GNR-PAn Composites .................................... 386
14.4 Results and Discussions ...................................... 389
14.4.1 Device Characteristics of Chlorinated PAn ............. 390
14.4.2 Device Characteristics of ZZGNR-PAn Nanocomposite ..... 393
14.4.3 Device Characteristics of ACGNR-PAn Nanocomposite ..... 395
14.4.4 Device Characteristics HGNR-PAn Nanocomposite ......... 397
14.5 Conclusion and Outlook ....................................... 398
References ................................................... 400
15 Analytical Modeling of Thin-Film Solar Cells -
Fundamentals and Applications ................................ 409
Kurt Taretto
15.1 Introduction ................................................. 409
15.2 Basics ....................................................... 410
15.2.1 Equivalent Solar Cell Circuit and Current-Voltage
Equation .............................................. 414
15.3 Fundamental Semiconductor Equations .......................... 417
15.3.1 Electric Field and Free Carrier Currents .............. 417
15.3.2 Steady-State Continuity Equations ..................... 419
15.3.3 Considerations for Excitonic Solar Cells .............. 422
15.3.4 Characteristic Lengths ................................ 422
15.3.5 Tunneling Recombination Occurring at the Nanometer
Scale ................................................. 423
15.4 Analytical Models for Selected Solar Cells ................... 425
15.4.1 Horizontal PN Junction ................................ 425
15.4.1.1 PN Junction under Moderately Absorbed Light ....... 430
15.4.1.2 Open-Circuit Voltage Limitations .................. 431
15.4.2 PN Heterojunction ..................................... 433
15.4.3 Vertical PN Multijunction ............................. 434
15.4.4 Considerations for Nanorod Solar Cells ................ 438
15.4.5 PIN Junction .......................................... 439
15.4.5.1 Enhanced Uniform Field Approximation .............. 439
15.4.5.2 Drift-Diffusion Model ............................. 440
15.5 The Importance of the Temperature Dependence of VOC .......... 442
15.6 Conclusions and Outlook ...................................... 444
Acknowledgements ............................................. 444
References ................................................... 444
16 Efficient Organic Photovoltaic Cells: Current Global
Scenario ..................................................... 447
Sandeep Rai and Atul Tiwari
16.1 Introduction ................................................. 448
16.2 Current Developments in OPVs ................................. 455
16.2.1 Development of Low Optical Gap Materials .............. 461
16.2.2 Designing of Higher IP Polymers and Lower EA
Acceptors ............................................. 461
16.2.3 Control of Blend Microstructure ....................... 463
16.3 Economics of Solar Energy .................................... 464
16.3.1 Scenario in US ........................................ 466
16.3.2 Solar Potential in India .............................. 467
16.3.3 Global Solar Cell Demand .............................. 467
16.4 Conclusions and Future Trends in Photovoltaic ................ 468
References ................................................... 471
17 Real and Reactive Power Control of Voltage Source
Converter-Based Photovoltaic Generating Systems .............. 475
S. Mishra and P. C. Sekhar
17.1 Introduction ................................................. 476
17.2 State of Art ................................................. 478
17.3 Proposed Solution ............................................ 479
17.4 Modeling of the PV Generator ................................. 480
17.5 Control of the PV Generator .................................. 483
17.5.1 Maximum Power Point Tracking and the Perturb and
Observe Algorithm ..................................... 483
17.5.2 Control of Reactive Power Output from the PV
System ................................................ 484
17.5.3 DC Link Voltage Control for Maximum Power
Extraction ............................................ 487
17.5.4 Reference Current Generation for Voltage Source
Converter ............................................. 488
17.5.5 Decoupled Control of VSC-based PV Generating
System ................................................ 489
17.6 Validation of the Proposed Control Architecture .............. 491
17.6.1 Control of Real Power Feeding of PV Generator and
PCC Voltage under Reverse Power Flow in a
Distribution System ................................... 491
17.6.2 Control of Real and Reactive Power Feedings of PV
Generator ............................................. 497
17.7 Conclusion and Outlook ....................................... 501
References ................................................... 502
Index ............................................................. 505
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