Rational Design of Solar Cells for Efficient Solar Energy Conversion
Description
Rational Design of Solar Cells for Efficient Solar Energy Conversion explores the development of the most recent solar technology and materials used to manufacture solar cells in order to achieve higher solar energy conversion efficiency. The text offers an interdisciplinary approach and combines information on dye-sensitized solar cells, organic solar cells, polymer solar cells, perovskite solar cells, and quantum dot solar cells.
The text contains contributions from noted experts in the fields of chemistry, physics, materials science, and engineering. The authors review the development of components such as photoanodes, sensitizers, electrolytes, and photocathodes for high performance dye-sensitized solar cells. In addition, the text puts the focus on the design of material assemblies to achieve higher solar energy conversion. This important resource:
* Offers a comprehensive review of recent developments in solar cell technology
* Includes information on a variety of solar cell materials and devices, focusing on dye-sensitized solar cells
* Contains a thorough approach beginning with the fundamental material characterization and concluding with real-world device application.
* Presents content from researchers in multiple fields of study such as physicists, engineers, and material scientists
Written for researchers, scientists, and engineers in university and industry laboratories, Rational Design of Solar Cells for Efficient Solar Energy Conversion offers a comprehensive review of the newest developments and applications of solar cells with contributions from a range of experts in various disciplines.
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Alagarsamy Pandikumar, Ph.D., is a Scientist at the Functional Materials Division, CSIR-Central Electrochemical Research Institute, and leads the Solar Energy Materials Research Group.
Ramasamy Ramaraj, Ph.D., is a CSIR-Emeritus Scientist in the School of Chemistry, at Madurai Kamaraj University, where he continues his research work on photoelectrochemistry.
Content
Biographies xiii
List of Contributors xv
Preface xix
1 Metal Nanoparticle Decorated ZnO Nanostructure Based Dye-Sensitized Solar Cells 1
Gregory Thien Soon How, Kandasamy Jothivenkatachalam, Alagarsamy Pandikumar, and Nay Ming Huang
1.1 Introduction 1
1.2 Metal Dressed ZnO Nanostructures as Photoanodes 3
1.2.1 Metal Dressed ZnO Nanoparticles as Photoanodes 4
1.2.2 Metal Dressed ZnO Nanorods as Photoanodes 6
1.2.3 Metal Dressed ZnO Nanoflowers as Photoanodes 8
1.2.4 Metal Dressed ZnO Nanowires as Photoanodes 8
1.2.5 Less Common Metal Dressed ZnO Nanostructures as Photoanodes 10
1.2.6 Comparison of the Performance of Metal Dressed ZnO Nanostructures in DSSCs 10
1.3 Conclusions and Outlook 11
References 13
2 Cosensitization Strategies for Dye-Sensitized Solar Cells 15
Gachumale Saritha, Sambandam Anandan, and Muthupandian Ashokkumar
2.1 Introduction 15
2.2 Cosensitization 18
2.2.1 Cosensitization of Metal Complexes with Organic Dyes 19
2.2.1.1 Phthalocyanine-based Metal Complexes 19
2.2.1.2 Porphyrin-based Metal Complexes 21
2.2.1.3 Ruthenium-based Metal Complexes 27
2.2.2 Cosensitization of Organic-Organic Dyes 41
2.3 Conclusions 51
Acknowledgements 51
References 52
3 Natural Dye-Sensitized Solar Cells - Strategies and Measures 61
N. Prabavathy, R. Balasundaraprabhu, and Dhayalan Velauthapillai
3.1 Introduction 61
3.1.1 Mechanism of the Dye-Sensitized Solar Cell Compared with the Z-scheme of Photosynthesis 62
3.2 Components of Dye-sensitized Solar Cell 63
3.2.1 Photoelectrode 63
3.2.2 Dye 64
3.2.3 Liquid Electrolyte 64
3.2.4 Counterelectrode 65
3.3 Fabrication of Natural DSSCs 65
3.3.1 Preparation of TiO2 Nanorods by the Hydrothermal Method 65
3.3.2 Characterization of the Photoelectrode for DSSCs 66
3.3.3 Preparation of Natural Dye 67
3.3.4 Sensitization 68
3.3.5 Arrangement of the DSSC 68
3.4 Efficiency and Stability Enhancement in Natural Dye-Sensitized Solar Cells 68
3.4.1 Effect of Photocatalytic Activity of TiO2 Molecules on the Photostability of Natural Dyes 69
3.4.1.1 Important Points to be Considered for the Preparation of Photoelectrodes 70
3.4.2 Citric Acid - Best Solvent for Extracting Anthocyanins 70
3.4.3. Algal Buffer Layer to Improve Stability of Anthocyanins in DSSCs 72
3.4.3.1 Preparation of Buffer Layers - Sodium Alginate and Spirulina 73
3.4.4 Sodium-doped Nanorods for Enhancing the Natural DSSC Performance 75
3.4.4.1 Preparing Sodium-doped Nanorods as the Photoelectrode 75
3.4.5 Absorber Material for Liquid Electrolytes to Avoid Leakage 77
3.5 Other Strategies and Measures taken in DSSCs Using Natural Dyes 79
3.6 Conclusions 82
References 82
4 Advantages of Polymer Electrolytes for Dye-Sensitized Solar Cells 85
L.P. Teo and A.K. Arof
4.1 Why Solar Cells? 85
4.2 Structure and Working Principle of DSSCs with Gel Polymer Electrolytes (GPEs) 86
4.3 Gel Polymer Electrolytes (GPEs) 87
4.3.1 Chitosan (Ch) and Blends 88
4.3.2 Phthaloylchitosan (PhCh) and Blends 91
4.3.3 Poly(Vinyl Alcohol) (PVA) 98
4.3.4 Polyacrylonitrile (PAN) 105
4.3.5 Polyvinylidene Fluoride (PVdF) 109
4.4 Summary and Outlook 110
Acknowledgements 111
References 111
5 Advantages of Polymer Electrolytes Towards Dye-sensitized Solar Cells 121
Nagaraj Pavithra, Giovanni Landi, Andrea Sorrentino, and Sambandam Anandan
5.1 Introduction 121
5.1.1 Energy Demand 121
5.1.1.1 Generation of Solar Cells 122
5.1.2 Types of Electrolyte Used in Third Generation Solar Cells 124
5.1.2.1 Liquid Electrolytes (LEs) 124
5.1.2.2 Room Temperature Ionic Liquids (RTILs) 125
5.1.2.3 Solid State Hole Transport Materials (SS-HTMs) 126
5.2 Polymer Electrolytes 127
5.2.1 Mechanism of Ion Transport in Polymer Electrolytes 128
5.2.2 Types of Polymer Electrolyte 129
5.2.2.1 Solid Polymer Electrolytes 129
5.2.2.2 Gel Polymer Electrolytes 129
5.2.2.3 Composite Polymer Electrolyte 130
5.3 Dye- sensitized Solar Cells 130
5.3.1 Components and Operational Principle 131
5.3.1.1 Substrate 133
5.3.1.2 Photoelectrode 134
5.3.1.3 Photosensitizer 135
5.3.1.4 Redox Electrolyte 137
5.3.1.5 Counter Electrode 140
5.3.2 Application of Polymer Electrolytes in DSSCs 140
5.3.2.1 Solid-state Dye-Sensitized Solar Cells (SS-DSSCs) 140
5.3.2.2 Quasi-solid-state Dye-Sensitized Solar Cells (QS-DSSC) 142
5.3.2.3 Types of Additives in GPEs 144
5.3.3 Bifacial DSSCs 148
5.4 Quantum Dot Sensitized Solar Cells (QDSSC) 150
5.5 Perovskite- Sensitized Solar Cells (PSSC) 152
5.6 Conclusion 153
Acknowledgements 154
References 154
6 Rational Screening Strategies for Counter Electrode Nanocomposite Materials for Efficient Solar Energy Conversion 169
Prabhakarn Arunachalam
6.1 Introduction 169
6.2 Principles of Next Generation Solar Cells 171
6.2.1 Dye-sensitized Solar Cells 171
6.2.2 Principles of Quantum Dot Sensitized Solar Cells 173
6.2.3 Principles of Perovskite Solar Cells 174
6.3 Platinum- free Counterelectrode Materials 175
6.3.1 Carbon-based Materials for Solar Energy Conversion 175
6.3.2 Metal Nitride and Carbide Materials 178
6.3.3 Metal Sulfide Materials 179
6.3.4 Composite Materials 182
6.3.5 Metal Oxide Materials 183
6.3.6 Polymer Counterelectrodes 184
6.4 Summary and Outlook 185
References 186
7 Design and Fabrication of Carbon-based Nanostructured Counter Electrode Materials for Dye-sensitized Solar Cells 193
Jayaraman Theerthagiri, Raja Arumugam Senthil, and Jagannathan Madhavan
7.1 Photovoltaic Solar Cells - An Overview 193
7.1.1 First Generation Solar Cells 194
7.1.2 Second Generation Solar Cells 194
7.1.3 Third Generation Solar Cells 194
7.1.4 Fourth Generation Solar Cells 195
7.2 Dye- sensitized Solar Cells 195
7.2.1 Major Components of DSSCs 196
7.2.1.1 Transparent Conducting Glass Substrate 197
7.2.1.2 Photoelectrode 197
7.2.1.3 Dye Sensitizer 198
7.2.1.4 Redox Electrolytes 199
7.2.1.5 Counterelectrode 200
7.2.2 Working Mechanism of DSSCs 200
7.3 Carbon- based Nanostructured CE Materials for DSSCs 201
7.4 Conclusions 216
References 217
8 Highly Stable Inverted Organic Solar Cells Based on Novel Interfacial Layers 221
Fang Jeng Lim and Ananthanarayanan Krishnamoorthy
8.1 Introduction 221
8.2 Research Areas in Organic Solar Cells 222
8.3 An Overview of Inverted Organic Solar Cells 224
8.3.1 Transport Layers in Inverted Organic Solar Cells 227
8.3.2 PEDOT:PSS Hole Transport Layer 227
8.3.3 Titanium Oxide Electron Transport Layer 229
8.4 Issues in Inverted Organic Solar Cells and Respective Solutions 232
8.4.1 Wettability Issue of PEDOT:PSS in Inverted Organic Solar Cells 233
8.4.2 Light-soaking Issue of TiOx-based Inverted Organic Solar Cells 234
8.5 Overcoming the Wettability Issue and Light-soaking Issue in Inverted Organic Solar Cells 235
8.5.1 Fluorosurfactant-modified PEDOT:PSS as Hole Transport Layer 235
8.5.2 Fluorinated Titanium Oxide as Electron Transport Layer 239
8.6 Conclusions and Outlook 245
Acknowledgements 246
References 246
9 Fabrication of Metal Top Electrode via Solution-based Printing Technique for Efficient Inverted Organic Solar Cells 255
Navaneethan Duraisamy, Kavitha Kandiah, Kyung-Hyun Choi, Dhanaraj Gopi, Ramesh Rajendran, Pazhanivel Thangavelu, and Maadeswaran Palanisamy
9.1 Introduction 255
9.2 Organic Photovoltaic Cells 257
9.3 Working Principle 258
9.4 Device Architecture 260
9.4.1 Single Layer or Monolayer Device 260
9.4.2 Planar Heterojunction Device 261
9.4.3 Bulk Heterojunction Device 261
9.4.4 Ordered Bulk Heterojunction Device 261
9.4.5 Inverted Organic Solar Cells 262
9.5 Fabrication Process 263
9.5.1 Hybrid-EHDA Technique 263
9.5.1.1 Flow Rate 265
9.5.1.2 Applied Potential 265
9.5.1.3 Pneumatic Pressure 265
9.5.1.4 Stand-off Distance 265
9.5.1.5 Nozzle Diameter 266
9.5.1.6 Ink Properties 266
9.5.2 Mode of Atomization 267
9.5.2.1 Dripping Mode 267
9.5.2.2 Unstable Spray Mode 267
9.5.2.3 Stable Spray Mode 267
9.6 Fabrication of Inverted Organic Solar Cells 267
9.6.1 Deposition of Zinc Oxide (ZnO) on ITO Substrate 268
9.6.2 Deposition of P3HT:PCBM 268
9.6.3 Deposition of PEDOT:PSS 268
9.6.4 Deposition of Silver as a Top Electrode 269
9.7 Device Morphology 272
9.8 Device Performance 273
9.9 Conclusion 277
Acknowledgements 277
References 277
10 Polymer Solar Cells - An Energy Technology for the Future 283
Alagar Ramar and Fu-Ming Wang
10.1 Introduction 283
10.2 Materials Developments for Bulk Heterojunction Solar Cells 284
10.2.1 Conjugated Polymer-Fullerene Solar Cells 284
10.2.2 Non-Fullerene Polymer Solar Cells 289
10.2.3 All-Polymer Solar Cells 290
10.3 Materials Developments for Molecular Heterojunction Solar Cells 291
10.3.1 Double-cable Polymers 291
10.4 Developments in Device Structures 293
10.4.1 Tandem Solar Cells 295
10.4.2 Inverted Polymer Solar Cells 297
10.5 Conclusions 300
Acknowledgements 300
References 301
11 Rational Strategies for Large-area Perovskite Solar Cells: Laboratory Scale to Industrial Technology 307
Arunachalam Arulraj and Mohan Ramesh
11.1 Introduction 307
11.2 Perovskite 308
11.3 Perovskite Solar Cells 309
11.3.1 Architecture 310
11.3.1.1 Mesoporous PSCs 310
11.3.1.2 Planar PSCs 313
11.4 Device Processing 313
11.4.1 Solvent Engineering 313
11.4.2 Compositional Engineering 314
11.4.3 Interfacial Engineering 314
11.5 Enhancing the Stability of Devices 316
11.5.1 Deposition Techniques 317
11.5.1.1 Spin Coating 317
11.5.1.2 Blade Coating 319
11.5.1.3 Slot Die Coating 320
11.5.1.4 Screen Printing 321
11.5.1.5 Spray Coating 324
11.5.1.6 Laser Patterning 324
11.5.1.7 Roll-to-Roll Deposition 325
11.5.1.8 Other Large Area Deposition Techniques 326
11.6 Summary 329
Acknowledgement 329
References 329
12 Hot Electrons Role in Biomolecule-based Quantum Dot Hybrid Solar Cells 339
T. Pazhanivel, G. Bharathi, D. Nataraj, R. Ramesh, and D. Navaneethan
12.1 Introduction 339
12.2 Classifications of Solar Cells 341
12.2.1 Inorganic Solar Cells 342
12.2.2 Organic Solar Cells (OSCs) 343
12.2.3 Hybrid Solar Cells 344
12.3 Main Losses in Solar Cells 344
12.3.1 Recombination Loss 345
12.3.2 Contact Losses 345
12.4 Hot Electron Concept in Materials 346
12.5 Methodology 347
12.5.1 Hot Injection Method 348
12.5.1.1 Nucleation and Growth Stages 349
12.5.1.2 Merits of this Method 350
12.6 Material Synthesis 350
12.6.1 CdSe QD Preparation 350
12.6.2 QD-ßC Hybrid Formation 351
12.7 Identification of Hot Electrons 351
12.7.1 Photoluminescence (PL) Spectrum 351
12.7.2 Time-correlated Single Photon Counting (TCSPC) 355
12.7.3 Transient Absorption 357
12.8 Quantum Dot Sensitized Solar Cells 360
12.8.1 Working Principle 360
12.8.2 Device Preparation 361
12.8.2.1 Preparation of TiO2 Nanoparticle Electrode 361
12.8.2.2 QDs Deposition on TiO2 Nanoparticle 362
12.8.2.3 Counterelectrode and Assembly of QDSSC 362
12.8.3 Performance 362
12.9 Conclusion 363
References 363
Index 369
1
Metal Nanoparticle Decorated ZnO Nanostructure Based Dye-Sensitized Solar Cells
Gregory Thien Soon How1, Kandasamy Jothivenkatachalam2, Alagarsamy Pandikumar3, and Nay Ming Huang4
1 Department of Physics, University of Malaya, Malaysia
2 Department of Chemistry, Anna University-BIT Campus, Tiruchirappalli-620024, Tamilnadu, India
3 Functional Materials Division, CSIR-Central Electrochemical Research Institute, Karaikudi-630006, India
4 Faculty of Engineering, University Xiamen Malaysia, Malaysia
1.1 Introduction
Solar energy has always been an ideal renewable energy source that is clean, abundant, inexpensive, and widely distributed regionally in the world [1-3]. Understanding this, the emergence of dye-sensitized solar cells (DSSCs) for converting solar energy to electricity has been very promising due to the ease of the manufacturing process, the low fabrication cost, the fact that it is nonpolluting, and the relatively high efficiency [1, 4-6]. It is known that a typical DSSC consists of various subsections, includinng a nanocrystalline semiconductor oxide photoanode, dye sensitizer, redox couple electrolyte, and counterelectrode [3, 4]. The main idea behind the operating principle of DSSCs is based on the optical excitation of a dye that results in the injection of an electron into the conduction band of a wide band gap semiconductor oxide. The oxidized dye molecule is regenerated afterwards when it is reduced to its ground state by gaining one electron from a redox couple that is found in the electrolyte around the sensitized semiconductor oxide nanostructured film [3-5]. Since the first outstanding research work on DSSC was demonstrated by O'Regan and Gratzel in 1991 [5], each of its components has been extensively investigated and optimized, with the aim to maximize the power conversion efficiency (PCE) of DSSCs [4, 7, 8]. Recently, a PCE of 12.3% has been achieved by using the cosensitization of two dyes and a Co(II/III) tris(bipyridyl)-based redox electrolyte [9]. Hence, study to find a suitable and high performance DSSC output has greatly increased over the years.
Amongst all the materials studied for use in DSSCs, nanocrystalline TiO2 has been most commonly employed as the metal oxide semiconductor material in high efficiency DSSCs [4-6]. Several methods were used for the preparation of the TiO2 nanoparticles in DSSCs, such as sol-gel [10, 11], gas-phase pyrolysis [12], or the commonly used hydrothermal synthesis method [13, 14]. However, hydrothermal methods are not ideal because both synthesis and purification processes take a prolonged time to achieve well-formed and highly crystalline TiO2 particles [12]. To minimize the costs of metal oxide semiconductor materials for DSSCs, simple preparation methods are essential to control the formation of crystal structure, crystallization, and particle size [15]. Besides TiO2, there are reports of other alternative metal oxides, such as SnO2, Nb2O5, and ZnO, being used as porous semiconductor materials for DSSC photoelectrodes [16-20].
ZnO is an another attractive and alternative photoanode to replace TiO2 as an electron conductor owing to its higher bulk electron mobility and easily tunable morphology, which allows the rational design and development of hierarchical ZnO nanostructures able to simultaneously optimize charge carrier path and dye loading [19, 20]. Hence, ZnO is considered an excellent backbone to produce high-efficiency DSSCs. The ZnO characteristic of higher electron mobility (~205-1000 cm2 V-1 s-1) than TiO2 (~0.1 - 4 cm2 V-1 s-1), enables the rapid diffusion transport of photoinjected electrons when it is employed as a photoanode material in DSSCs. In addition, ZnO is a suitable material for the fabrication of mesoporous photoanodes in DSSCs; it has a band gap of 3.2 eV and a conduction band edge position of -4.3 eV, both of which are similar to TiO2 [15-17]. Moreover, ZnO can be easily prepared into tunable nanostructures, such as nanoparticles, nanowires, nanotubes, nanorods, nanosheets, and tetrapods, providing numerous alternatives for optimizing photoanode morphology so as to improve the charge collection. However, the conversion efficiency of ZnO-based DSSCs reported so far still remains lower than those fabricated from TiO2, leaving plenty of room to improve the efficiency through structural and morphology modifications of the ZnO nanostructures. Previous review articles [16, 17] have explored recent developments in ZnO nanostructures for application in DSSCs and suggest that the nanostructured ZnO can significantly enhance solar cell performance due to the large surface area for dye adsorption, direct transport pathways for photoexcited electrons, and efficient scattering centers for enhanced light-harvesting efficiency. Furthermore, the limitations of ZnO-based DSSCs are also discussed and a few suggestions are also given for the conversion efficiency improvement.
1.2 Metal Dressed ZnO Nanostructures as Photoanodes
One of the major challenges in the development of high efficiency DSSCs is the competition between the generation and recombination of photoexcited carriers. The use of low-dimensional nanostructures is able to support a direct pathway for the rapid collection of photogenerated electrons and, hence, reduce the charge recombination [21, 22]. Thus, the possible alternative way to improve the charge separation in DSSCs is to introduce a barrier layer at the semiconductor/electrolyte interface to block the back electron transfer from the semiconductor to the redox electrolyte. Doping of metals on ZnO nanostructures significantly reduces the charge recombination, which is another way to improve the charge separation in DSSCs. Rapid charge transfer and improved charge separation upon incorporation of metal nanoparticles on ZnO, leading to enhanced DSSC performance, have been demonstrated [23-33]. Moreover, the metal nanoparticles (namely silver and gold) that possess surface plasmon resonance can couple to visible light, which increases the optical absorption of the photoelectrode in the visible region.
Metal nanoparticles doped on ZnO exhibit unusual redox activity by readily accepting electrons either from a dye molecule or an electrode. Such metal nanoparticles, when in contact with a ZnO nanostructure, can equilibrate and undergo Fermi-level equilibration, thus forming a Schottky barrier at the metal/ZnO nanocomposite interfaces (Figure 1.1) [22].
Figure 1.1 Schematic representation of photoinduced charge separation and charge distribution in ZnO/metal nanocomposites. EF and E´F represent Fermi levels attained before and after charge distribution.
Source: Adapted from Subramanian 2003 [22]. Reprinted with permission of American Chemical Society.
The charge equilibration between the metal and ZnO nanocomposite interfaces in contact drives the Fermi level close to the conduction band edge of the semiconductor and, thus, influences the photovoltaic performance of DSSCs. So far, ZnO-based DSSC performance has been reviewed but there is no summary of the metal dressed ZnO based DSSC performance. In this review, the recent progress on metal dressed ZnO based DSSC and the role of metal nanoparticles on various ZnO nanostructures in DSSCs (Figure 1.2) in improving the device performance (through improved charge separation introduced by the Schottky barrier formed at the metal/ZnO nanocomposite interface) are discussed. Furthermore, the influence of silver and gold nanoparticles leading to enhanced optical absorption on the performance of DSSCs is also discussed.
Figure 1.2 Various types of metal dressed ZnO nanostructure used as photoanodes in DSSCs.
1.2.1 Metal Dressed ZnO Nanoparticles as Photoanodes
There are few related works reported involving metal dressed ZnO nanoparticles as photoanodes in DSSC applications. Among them, Tripathi [23] and coworkers reported a bilayer TiO2:Ag/ZnO:Ag (TZO:Ag) oxide film using a sol-gel process for DSSCs. They have investigated the effect of Eosin-Y dye and a cocktail dye (C) (Rhodamine B, Rose Bengal, Fast Green, Acridine Orange, Fast Green) for DSSC application. In comparison to the undoped ZnO/C film, their TZO/Ag/C film exhibits higher Voc, Jsc, and PCE of 0.158%. This is due to the surface plasmon resonance effect of the silver nanoparticles in enhancing visible light absorption and also the Schottky barrier established at the semiconductor/metal interface. Sarkar et al. reported a nanocomposite consisting of gold and ZnO nanoparticles (NPs) for photocatalysis and DSSC applications [24]. Their ZnO-Au nanocomposite (NC) was synthesized based on the formation of gold NPs on the surface of ZnO NPs, using chloroauric acid ethanolic solution added into readily prepared ZnO NP colloid solution. To obtain the gold NPs, they added sodium borohydride (through a chemical reduction method) in order for gold chloride to undergo reduction. Interestingly, the ZnO-Au NC morphology (Figure 1.3) reveals the uniform distribution of gold on spherical...
