Contents

Cover

Title page

Copyright page

Preface

Part I: Hybrid Materials and Process Technologies for Printable Solar Cells

Chapter 1: Organic and Inorganic Hybrid Solar Cells
1. 1.1 Introduction
2. 1.2 Organic/Inorganic Hybrid Solar Cells
3. 1.3 Conclusion
4. References
Chapter 2: Solution Processing and Thin Film Formation of Hybrid Semiconductors for Energy Applications
1. 2.1 Physical Chemical Principles of Film Formation by Solution Processes: From Suspensions of Nanoparticles and Solutions to Nucleation, Growth, Coarsening and Microstructural Evolution of Films
2. 2.2 Solution-Processing Techniques for Thin Film Deposition
3. 2.3 Properties and Characterization of Thin Films: Transport, Active and Electrode Layers in Thin Film Solar Cells
4. 2.4 Understanding the Crystallization Processes in Hybrid Semiconductor Films: Hybrid Perovskite as a Model
5. References
Chapter 3: Organic-Inorganic Hybrid Solar Cells Based on Quantum Dots
1. 3.1 Introduction
2. 3.2 Polymer/QD Solar Cells
3. 3.3 Outlooks and Conclusions
4. Acknowledgment
5. References
Chapter 4: Hole Transporting Layers in Printable Solar Cells
1. 4.1 Introduction
2. 4.2 Hole Transporting Layers in Organic Solar Cells
3. 4.3 Hole Transporting Layers in Dye-Sensitized Solar Cells
4. 4.4 Hole Transporting Layers in Perovskite Solar Cells
5. 4.5 Concluding Remarks
6. References
Chapter 5: Printable Solar Cells
1. 5.1 Introduction
2. 5.2 Printable Solar Cells Working Principles
3. 5.3 Solution-Based Deposition of Thin Film Layers
4. 5.4 Characterization Techniques
5. 5.5 Conclusion
6. References

Part II: Organic Materials and Process Technologies for Printable Solar Cells

Chapter 6: Spray-Coated Organic Solar Cells
1. 6.1 Introduction
2. 6.2 Introduction of Spray-Coating Method
3. 6.3 Materials for Spray Coating
4. 6.4 Application of Spray Coating
5. 6.5 Conclusions
6. Acknowledgment
7. References
Chapter 7: Interface Engineering: A Key Aspect for the Potential Commercialization of Printable Organic Photovoltaic Cells
1. 7.1 Introduction
2. 7.2 SD-PSCs Based on P3HT:PCBM Active Layers
3. 7.3 High Performance BHJ-PSCs with Favorable Molecular Orientation Resulting from Active Layer/Substrate Interactions
4. 7.4 Strongly Bond Metal Leaves as Laminated Top Electrodes for Low-Cost PSC Fabrication
5. 7.5 Conclusions
6. References
Chapter 8: Structural, Optical, Electrical and Electronic Properties of PEDOT: PSS Thin Films and Their Application in Solar Cells
1. 8.1 Introduction
2. 8.2 Chemical Structure of PEDOT:PSS
3. 8.3 Optical and Electrical Characteristics of PEDOT:PSS
4. 8.4 Electronic Characteristics of PEDOT:PSS
5. 8.5 Highly Conductive PEDOT:PSS Thin Films
6. 8.6 Hole-Transporting Materials: PEDOT:PSS Thin Films
7. 8.7 Directions for Future Development
8. 8.8 Conclusion
9. References

Part III: Perovskites and Process Technologies for Printable Solar Cells

Chapter 9: Organometal Trihalide Perovskite Absorbers: Optoelectronic Properties and Applications for Solar Cells
1. 9.1 Introduction
2. 9.2 Optical Properties of Organic-Inorganic Perovskite Materials
3. 9.3 Charge Transport Properties
4. 9.4 Electron Transporting Materials (ETM)
5. 9.5 Hole-Transporting Materials (HTM)
6. 9.6 Perovskite Solar Cells Architectures
7. 9.7 Perovskite Deposition Methods
8. 9.8 Photoexcited States
9. 9.9 Hysteresis
10. 9.10 Stability in Humid Environment
11. 9.11 Stability Under UV Light Exposure
12. 9.12 Stability at High Temperatures
13. 9.13 Additives
14. 9.14 Conclusions and Outlook
15. Acknowledgment
16. References
Chapter 10: Organic-Inorganic Hybrid Perovskite Solar Cells with Scalable and Roll-to-Roll Compatible Printing/Coating Processes
1. 10.1 Introduction
2. 10.2 Optoelectronic Properties
3. 10.3 History
4. 10.4 Device Configurations
5. 10.5 Functional Materials
6. 10.6 Spin Coating
7. 10.7 Roll-to-Roll Processing
8. 10.8 Substrate Limitation
9. 10.9 Printing and Coating Methods
10. 10.10 Future Outlook
11. References
Chapter 11: Inkjet Printable Processes for Dye-Sensitized and Perovskite Solar Cells and Modules Based on Advanced Nanocomposite Materials
1. 11.1 Introduction
2. 11.2 Inkjet Printing Process
3. 11.3 Conclusions
4. References

Part IV: Inorganic Materials and Process Technologies for Printable Solar Cells

Chapter 12: Solution-Processed Kesterite Solar Cells
1. 12.1 Introduction
2. 12.2 Fundamental Aspects of Kesterite Solar Cells
3. 12.3 Keterite Absorber Deposition Strategies
4. 12.4 Electrodeposition
5. 12.5 Direct Solution Coating
6. 12.6 Conclusion
7. References
Chapter 13: Inorganic Hole Contacts for Perovskite Solar Cells: Towards High-Performance Printable Solar Cells
1. 13.1 Introduction
2. 13.2 Transition Metal Oxides
3. 13.3 Non-Oxide Copper Compounds
4. 13.4 Other Inorganic HTMs
5. 13.5 Towards Printable Solar Cells
6. 13.6 Conclusions and Perspectives
7. Acknowledgment
8. References
Chapter 14: Electrode Materials for Printable Solar Cells
1. 14.1 Introduction
2. 14.2 Transparent Conjugated Polymers
3. 14.3 Carbon-Based Nanomaterials
4. 14.4 Metallic Nanostructures
5. 14.5 Multilayer Thin Films
6. 14.6 Printable Metal Back Electrodes
7. 14.7 Carbon-Based Back Electrodes
8. 14.8 Summary and Outlook
9. Acknowledgment
10. References
Chapter 15: Photonic Crystals for Photon Management in Solar Cells
1. 15.1 Introduction
2. 15.2 Fundamentals of PCs
3. 15.3 Fabrication Strategies of PCs for Photovoltaics
4. 15.4 Different Functionalities of PCs in Solar Cells
5. 15.5 Summary and Outlook
6. Acknowledgment
7. References

Index

End User License Agreement

List of Illustrations

Chapter 1

Figure 1.1 General structure of a hybrid solar cell: (a) representation for working principle of polymer/nanoparticles, (b) energy level diagram and charge transfer process, (c) bilayer, (d) bulk, and (e) ordered heterojunction. (Reprinted with permission from [4]; Copyright 2014 © Elsevier)
Figure 1.2 Schematics of (a) a front-junction organic-silicon heterojunction cell and (b) a back-junction (“BackPEDOT”) solar cell on n-type silicon. (Reprinted with permission from [41]; Copyright 2014 © Elsevier)
Figure 1.3 Schematic of a dye-sensitized solar cell.
Figure 1.4 (a) Schematic of the solar cell stack; (b) Freestanding 3-m-thick solar cells with gold top metal; (c) Perovskite solar foil with low-cost copper back contacts; (d) Power-per-weight of ultrathin perovskite solar cells is more than double the nearest competing photovoltaic technology; (e) Dried leaf skeleton covered with a solar array of eight cells; (f) Schematic drawing of the solar-powered model airplane; (g) Power output of the 64-cell solar panel; (h) Snapshot of the model plane during solar-powered outdoor flight; (i) Close-up photograph of the horizontal stabilizer with integrated solar panel. (Reprinted with permission from [148]; Copyright © 2015 Macmillan Publishers Ltd.)

Chapter 2

Figure 2.1 (a) Schematic illustration of nucleation during supersaturation of a wet film solution. (b) Normalized nucleation rate as a function of supersaturation ratio S. (c) Nucleation and growth rate as a function of temperature. Hom. denotes homogeneous and Het. heterogeneous (adapted from [8]).
Figure 2.2 (a) Basic stages during a spin coating process. (b) Supersaturation shifting depending on the ink composition (reprinted from [27]).
Figure 2.3 (a) Basic film formation processes during doctor blade (reprinted from [31]). Besides layer formation, the doctor blade can influence the layer crystallization leading to (b) molecular orientation in a Poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta [2,1-b;3,4-b′] dithiophene)-alt-4,7(2,1,3-benzothiadiazole)] (PCPDTBT) film (reprinted from [35]), (c) crystal orientation in a 5,50-bis(4-butoxyphenyl)-2,20-bithiophene (dbo-P2TP) film (reprinted from [36]), and (d) perovskite crystal size enlargement (reprinted from [31]).
Figure 2.4 (a) Basic parameters governing the slot-die processing. (b) Example of the variation of thickness and roughness of a perovskite film with different solution pumping rates. (c) Resulting perovskite surface coverage percentage as a function of the processing temperature.
Figure 2.5 Basic process during spray coating enabling compositional studies of the resulting films (reprinted from [42]).
Figure 2.6 Approach used to characterize a hybrid perovskite thin film.
Figure 2.7 Calorimetric analysis of the CH₃NH₃PbI_3-xCl_x perovskite. (a) Typical planar solar cell architecture; (b) DSC analysis of CH₃NH₃PbI_3-xCl_x prepared in situ from solution on the DSC pans; (c) Schematic illustration of CH₃NH₃PbI_3-xCl_x embedded into mesoporous Al₂O₃ scaffold with a part of the perovskite forming a capping layer; (d) DSC analysis of CH₃NH₃PbI_3-xCl_x in the presence of Al₂O₃ scaffold as shown in (c). (Adapted from [11, 62])
Figure 2.8 Pin planar perovskite solar cells developed under different crystallization processes. (a) Thermal processing protocol of the CH₃NH₃PbI_3-xCl_x layer. Inset: average PCE correlated in the DSC thermogram. (b) Average J-V curves for the different devices. (Adapted from [11])
Figure 2.9 Thermal stress simulations at different annealing temperatures: (a) Stress distribution in the active layer (m-Al₂O₃ + perovskite); (b) Maximum thermal stress in the alumina scaffold (x), alumina/capping layer interface (y) and capping layer (z) at T1 = 90 °C, T2 = 100 °C, T3 = 110 °C and T4 = 120 °C. (Reprinted from [62])
Figure 2.10 Crystallinity and morphology of perovskite films: (a) XRD study of perovskite films fabricated under different annealing conditions showing crystallinity of the films (reprinted from [11]); (b) SEM images of a perovskite film at the optimum annealing temperature of 130 °C.
Figure 2.11 (a) Short-circuit current of CH₃NH₃PbI_3-xCl_x solar cells fabricated from precursors with different additives. (b,c) Morphology of the CH₃NH₃PbI_3-xCl_x film with water and DMSO added to the precursor solution, respectively. In Figures (b) and (c), “T” denotes thickness and “R” denotes roughness of the film.

Chapter 3

Figure 3.1 Work principle of polymer/QD solar cells.
Figure 3.2 Current density–voltage (J–V) characteristics for polymer/QD solar cells.
Figure 3.3 Device structure of polymer/QD solar cells.

Chapter 4

Figure 4.1 Schematic representation of the working principle in organic solar cells. HTL: Hole Transporting Layer; D: Donor material; A: Acceptor material; ETL: Electron Transporting Layer.
Figure 4.2 Evolution of the energy-level alignment at the substrate interface upon physisorption of a π-conjugated organic material (small molecule or polymer). (a) Ф_sub > E_ICT+: Fermi-level pinning to a positive integer charge-transfer state; (b) Ф_sub < E_ICT-: Fermi-level pinning to a negative integer charge-transfer state; (c) E_ICT- < Ф_sub < E_ICT+: vacuum level alignment. The charge-transfer-induced shift in vacuum level, Δ, is shown where applicable. (Adapted with permission from [17]; Copyright © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
Figure 4.3 Chemical structures of polymer, small molecules and self-assembled monolayers used as hole transporting materials in organic solar cells.
Figure 4.4 Schematic representation of the working principle in DSSCs (left) and ss-DSSCs (right). (1) Light absorption and dye excitation; (2) electron transfer from the LUMO of the dye into the conduction band of the mesoporous oxide; (3) electron transfer from the oxide into the transparent electrode; (4) electron transfer from the electrolyte or the HOMO of the HTM into the HOMO of the oxidized dye; (5) electron transfer from the back electrode into the redox electrolyte or the HOMO of the HTM. Possible relaxation processes: (6) dye relaxation prior to electron transfer; (7) electron transfer from the mesoporous oxide conduction band into the redox electrolyte or the HOMO of the HTM and (8) electron transfer from the mesoporous oxide into the oxidized dye.
Figure 4.5 Chemical structures of small molecules and polymers used as hole transporting materials in dye-sensitized solar cells.
Figure 4.6 Chemical structures of small molecules used as hole transporting materials in perovskite solar cells.
Figure 4.7 Chemical structures of additives or dopants for hole transporting layers in perovskite solar cells.
Figure 4.8 Chemical structures of dopant-free small molecules used as hole transporting materials in perovskite solar cells.
Figure 4.9 Chemical structures of polymers used as hole transporting materials in perovskite solar cells.

Chapter 5

Figure 5.1 Chalcopyrite crystal structure of CIGS unit cell. Red = Cu, Yellow = Se, Blue = In/Ga.
Figure 5.2 CIGS solar cell structure.
Figure 5.3 Band gap tuning of halide perovskite materials [15].
Figure 5.4 Tandem Si/perovskite solar cell structure (left) and absorption spectrum (right).
Figure 5.5 Types of organic solar cell junctions: planar junction (left), controlled heterojunction (center) and bulk heterojunction (right). Donor material and acceptor materials are depicted in blue and red colors respectively.
Figure 5.6 A typical spin-coating process.
Figure 5.7 Illustration of the blade coating technique (left) and image of a blade coater (right) [58].
Figure 5.8 Basic principle of the rotary knife-over-edge and rotary slot-die coating methods [59].
Figure 5.9 Open slot-die head: (from left to right) ink distribution chamber, feed slot, lip and internal mask (shim).
Figure 5.10 Schemes of flat-bed screen printing (top) and rotary screen printing (bottom) [59].
Figure 5.11 Basic principle of the rotogravure printing technique.
Figure 5.12 A simplified scheme of the flexographic printing process.
Figure 5.13 Difference between continuous inkjet (top) and DOD (bottom) [40].
Figure 5.14 Schematic diagram showing four regimes of behavior of liquid drop based on the values of We and Oh [83].
Figure 5.15 J-V curve of a photovoltaic cell and equivalent electrical diagram.
Figure 5.16 Simplified 1 diode equivalent circuit model for a photovoltaic cell.
Figure 5.17 Maximum power for a J-V curve.
Figure 5.18 Getting the fill factor from the J-V curve.
Figure 5.19 Effect of diverging R_s and R_sh.
Figure 5.20 Temperature effect on the J-V curve.
Figure 5.21 The Printed Electronics Association application roadmap, with the forecast for market entry.

Chapter 6

Figure 6.1 Illumination of the architecture of modern airbrush equipment.
Figure 6.2 Generic description of the atomization process involved in ultrasonic nozzle systems; AccuMist™ ultrasonic nozzle with focused beam. (Reprinted with permission from Sono-Tek Corp. [22]; Copyright © 2014 Elsevier)
Figure 6.3 Process scheme of electrospray crystallization. Varied operation conditions: nozzle diameter (d), flow rate (f), concentration (c), potential difference (ΔU), and working distance (D). Solvent evaporation, Coulomb fission, and crystallization occur during the process. (Reprinted from [34]; Copyright © 2011 Wiley)
Figure 6.4 (a) Schematic diagram of the spray-coating apparatus; (b) Illustration of the sintering process of silver nanoparticle inks. (Reprinted from [37]; Copyright © 2014 Springer)
Figure 6.5 Schematic of the evolution of the liquid layer during the drying process: (a) top view of the liquid coverage of the substrate and its surroundings, together with the involved Marangoni flows; (b) Cross-section A-B: the enhanced evaporation rate at the contact line of the liquid layer with the substrate creates Marangoni flows from the bulk of the two-solvent system, establishing an advancing velocity for the contact line, which is able to recover unwetted areas. (Reprinted from [10]; Copyright © 2011 Wiley)
Figure 6.6 (a) Schematic of the alternating spray deposition apparatus. The device structure is shown with a TEM cross-sectional image, indicating the ITO/PEDOT:PSS/P3HT:PCBM layers starting from the left with well-defined interfaces. Zoom-in representative images taken from (b) optical profiler, (c) AFM, and (d) TEM of 150 °C annealed film from P3HT/PCBM alternating deposition. (Reprinted from [4]; Copyright © 2010 ACS)
Figure 6.7 (a) Schematic diagram of the procedures for fabricating AgNW–PEDOT:PSS composite electrodes. (b) Photograph of the AgNW mesh deposited on a PET substrate (13×13 cm). (c) SEM image of the uniformly deposited AgNW mesh without a large difference in the density of nanowires. Inset shows the cross-section view of the AgNW mesh. (d) Photograph of the AgNW–PEDOT:PSS composite film deposited on a PET substrate. The mean transmittance was 81.7% (at 550 nm) and the sheet resistance was 11.3 Ωsq^-1. Their standard deviations were 2.84% and 1.85 Ωsq^-1, respectively. (e) SEM image of the AgNW mesh embedded in the PEDOT:PSS film. Connections between nanowires were maintained upon deposition of PEDOT:PSS. Inset shows the angled cross-section view of the composite film. (Reprinted from [62]; Copyright © 2012 Royal Society of Chemistry)
Figure 6.8 Optical microscopy images of spray-deposited thin films of methylammonium iodide and lead chloride on substrates held at a range of elevated temperatures: (a) 28 °C, (b) 38 °C, (c) 55 °C, (d) 75 °C, (e) 80 °C, (f) 87 °C. The scale bar in each image corresponds to 20 mm. (Reprinted from [79]; Copyright © 2014 Royal Society of Chemistry)

Chapter 7

Figure 7.1 Schematic representation of the bulk-heterojunction (BHJ) and sequentially deposited (SD) active layer PSCs along with the interface-related mechanisms and effects in the device architectures.
Figure 7.2 Schematic representation of face-on and edge-on crystallites and their preferential charge transport direction.
Figure 7.3 AFM micrographs, cross sections and schematic cross sections of nanostructured P3HT films (a) before and (b) after coating with PCBM from DCM, and (c) after removing PCBM molecules with cyclohexanone. (Reprinted with permission from [33]; Copyright © 2012 Royal Society of Chemistry)
Figure 7.4 Evolution of (a) absorption and (b) absorption ratios and PL quenching of P3HT films with increasing RRa-P3HT wt%. (Reproduced with permission from [37]; Copyright © 2012 AIP Publishing LLC)
Figure 7.5 Evolution of the sulfur distribution (white lines), FF and Rs of active layers containing increasing RRa-P3HT wt%. The blue, green and red colors in the EDS images correspond to indium, sulfur and aluminum, respectively. The scale bar corresponds to 50 nm. (Reproduced with permission from [37]; Copyright © 2012 AIP Publishing LLC)
Figure 7.6 J-V curves and photovoltaic characteristics of SD-PSCs prepared with increasing RRa-P3HT wt%. (Adapted with permission from [37]; Copyright © 2012 AIP Publishing LLC)
Figure 7.7 Schematic representation of the fabrication process of rubbed SD-PSCs and EDS profiles of unrubbed and rubbed devices. (Adapted with permission from [42]; Copyright © 2012 American Chemical Society)
Figure 7.8 Average device performances, J-V curves and typical grazing (left) and incident (right) XRD of rubbed SD-PSCs. (Adapted with permission from [42]; Copyright © 2012 American Chemical Society)
Figure 7.9 Comparative J-V curves and photovoltaic performances of PNTz4T associated with either PCBM or PC₇₁BM in regular BHJ-PSCs. (Adapted with permission from [43]; Copyright © 2015 Springer)
Figure 7.10 Comparative 2D-XRD of PNTz4T associated with either PCBM or PC₇₁BM in regular BHJ-PSCs. (Adapted with permission from [43]; Copyright © 2015 Springer)
Figure 7.11 Contact angle measurements of DCB drops on (a) PEDOT:PSS and (b) ZnO surfaces. Comparative GIWAXD profiles (c) and thickness dependence of face-on to edge-on crystallite ratios (d) of active layers deposited on PEDOT:PSS or ZnO. (Adapted from reference [2]; Copyright © 2015 Nature Publishing Group)
Figure 7.12 Schematic representation and device performances of regular and inverted PNTz4T:PC₇₁BM BHJ-PSCs. (Adapted from [2]; Copyright © 2015 Nature Publishing Group)
Figure 7.13 Schematic representations of the evaporation and lamination processes and comparative J-V curves of P3HT:PCBM BHJ-PSCs fabricated with the two metal deposition processes.
Figure 7.14 Surface optical micrographs of evaporated Au (a), Ag (b) and laminated (c) Au, (d) Ag deposited on PEDOT:PSS.

Chapter 8

Figure 8.1 (a) Molecular structures of PEDOT and PSS polymers. (b) Benzoid and quinoid forms of PEDOT polymers. (c) Raman fingerprint of a PEDOT:PSS (1:6 wt%) thin film.
Figure 8.2 (a) Electronic structure of p-doped PEDOTs. (b) Transmittance spectrum of a PEDOT:PSS thin film deposited on glass substrate.
Figure 8.3 Transmittance spectra of the PEDOT:PSS thin films on glass substrate. (Reprinted with permission from [25])
Figure 8.4 Energy level scheme of the self-localized states in PEDOT polymers. (a) Band edge of a neutral PEDOT polymer; (b) polaron state formed upon the addition of an extra electron; (c) spinless bipolaron state formed upon the addition of a second electron.
Figure 8.5 Atomic force microscopic images of PEDOT:PSS thin films: (a–c) images of the topography; (d–f) adhesion images. (Reprinted with permission from [11])
Figure 8.6 Electronic structure of planar solar cells.
Figure 8.7 (a) Work functions of the PEDOT:PSS thin films. (b) Current density-voltage (J-V) curves of the CH₃NH₃PbI₃-based solar cells fabricated with the different PEDOT:PSS thin films under one-sun illumination (AM 1.5G, 100mW/cm²). (Reprinted with permission from [25])
Figure 8.8 Photoluminescence spectra of PCBM/FA_0.4MA_0.6PbI₃/PEDOT:PSS/ITO/glass samples. (Reprinted with permission from [15])
Figure 8.9 Atomic-force microscopic images (a,b,c) and water droplet contact angle images (d,e,f) of the modified PEDOT:PSS thin films (Reprinted with permission from [28]).

Chapter 9

Figure 9.1 Schematic representation of a typical PSC structure.
Figure 9.2 Basic crystal structure of ABX₃ perovskite material. (Reprinted with permission from [6])
Figure 9.3 IPCE curves for CH₃NH₃Sn_xPb_(1-x)I₃/P3HT solar cells. (Reprinted with permission from [14])
Figure 9.4 Schematic representation of the mesoporous, bi-layer, n-i-p and p-i-n architectures in PSCs. (Reprinted with permission from [43])
Figure 9.5 Schematic representation of the dual-source vapor deposition method. (Reprinted with permission from [49])
Figure 9.6 One-step and two-step solution deposition methods. (Reprinted with permission from [53])
Figure 9.7 Ion migration mechanism in perovskite during (a) positive and (b) negative poling. (Reprinted with permission from [62])
Figure 9.8 Ferroelectric polarization mechanism in PSCs. (Reprinted with permission from [65])
Figure 9.9 Degradation mechanism of CH₃NH₃PbI₃ under light exposure. (Reprinted with permission from [68])
Figure 9.10 Reported efficiencies for some thin films based photovoltaic devices. (Reprinted with permission from [86])

Chapter 10

Figure 10.1 (a) Number of publications of PeSCs (bar graph) and record efficiency since 2009. Data on publications collected from Web of Science and on efficiency from NREL and various literature sources (see ref. [6–8]). (b) Crystal structure of cubic metal halide perovskites with the generic chemical formula ABX₃. Absorption coefficients as a function of wavelength of various solar cell technologies. (Figure 10.1b reprinted with permission from [9]; Copyright © 2015 Material Research Society. Figure 10.1c adapted with permission from [10]; Copyright © 2014 Macmillan Publishers Ltd)
Figure 10.2 Schematic illustration of cross section of a dye-sensitized solar cell and the three most common configurations of PeSCs. SEM images correspond to the configurations shown directly above them. (SEM images: Mesoporous structure from ref. [28]; Copyright © 2013 Macmillan Publishers Ltd. Traditional planar structure from ref. [29]; Copyright © 2016 John Wiley & Sons. Inverted planar structure from ref. [30]; Copyright © 2014 American Chemical Society. Reprinted with permission)
Figure 10.3 Collection of materials employed in various functional layers in the PeSCs with their respective energy level. (Reprinted with permission from [40]; Copyright © 2016 Society of Photo Optical Instrumentation Engineers)
Figure 10.4 (a) Process of film formation in spin coating. (b) Perovskite CH₃NH₃PbI₃ film morphology with spin coating on flexible PET substrate via: (a) spin-coating 1-step method and (b) 2-step method. (Figure 10.1a adapted with permission from [101]; Copyright © 2013 The Royal Chemistry Society)
Figure 10.5 A semi-industrial R2R printing and coating machine. (Reprinted with permission from [105]; Copyright © 2012 Woodhead Publishing Ltd.)
Figure 10.6 (a) Snapshot of a model plane powered by flexible and lightweight ITO-free PeSCs based on PEDOT:PSS as transparent conductor. (b) A close-up picture of the PeSCs integrated in the model plane. (c) Power-to-weight ratio of PeSCs in (a) and (b) is compared with other solar cell technologies (d). J-V curves in reverse and forward scan measured under 1000 cm^–2 AM 1.5 G in yet another ultra-thin perovskite solar cell with an Ag grid/PEDOT:PSS as TCE (inset shows a photograph of the solar cell wrapped around a finger). (Figure 10.6–c reprinted with permission from [93] and Figure 10.6d reprinted with permission from [94]; Copyright © 2015 Macmillan Publishers Ltd.)
Figure 10.7 Schematic illustrations of selected printing methods.
Figure 10.8 Schematic illustrations of selected coating methods.
Figure 10.9 (a) A dissembled slot-die head showing meniscus guide (second from left) and flow mask for stripe coating (third from left). (b) Side view of an assembled slot-die head. (c) Slot-die coating of an ink in progress. (d) A gravure printing roll. Insets show the difference in engraving patterns on the printing roll in gravure printing (left) and in reverse gravure (right). (e) Flexographic printing in progress. Relief features on the flexographic printing cylinder can be seen. (f) The inside of rotary screen taken during printing of PEDOT:PSS. (g) Rotary screen printing of silver. View from outside the rotary screen roll. (h) Flat-bed screen printing of Ag in progress. (Copyrights: [a-b] from [113], Copyright © 2014 Technical University of Denmark; [c,g,h] from [114], Copyright © 2015 John Wiley and Sons Inc.; [d] from [115], Copyright © 2016 Elsievier; [e] from [116], Copyright © 2012 Elsievier; [f] from [117], Copyright © 2014 Technical University of Denmark. All figures reprinted with permission)
Figure 10.10 Influence of substrate and coating method on the perovskite absorber morphology processed from one-step and two-step methods. One-step process: (a) spin-coated on glass/ITO/PEDOT:PSS, (c) spin-coated on PET/ITO/PEDOT:PSS, (e) slot-die-coated on PET/ITO/PEDOT:PSS. Two-step process: (b) spin-coated on glass/ITO/ZnO, (d) spin-coated on PET/ITO/ZnO substrate, (f) slot-die-coated on PET/ITO/ZnO. (Reprinted with permission from [75]; Copyright © 2015 John Wiley and Sons Inc.)
Figure 10.11 Nozzle-less ultrasonic spray coating is compared with spin coating. (a) Photographs of the spray-coating head under operation and (b) a close up, (c) spray-coated cell and (d) spin-coated cell (scale-bar inset is 2 mm), ζ J-V curve of spin-coated (Device A) and all spray-coated cell (Device B). (f) Laser beam-induced current (LBIC) mapping of: (f) spin-coated cells and (g) of spray-coated cells. (h) The line profile of the current along the scan direction shown in Figure (f–g). (Reprinted with permission from [136]; Copyright © 2016 John Wiley & Sons)
Figure 10.12 (a) Benchtop blade-coating equipment. A blade-coated perovskite film is shown. (b) SEM cross section of an all-doctor-blade-coated PeSC except for the electrodes. (c) Photographs of a blade-coated large-area (15 mm × 40 mm) perovskite film shown before and after thermal annealing process and the completed cells after electrode deposition. (d) J-V curves measured under AM 1.5 irradiation at 100 mW cm^–2 conditions. All the positions correspond to the cells position on a single substrate, as shown in (c). (e) Variation in the photovoltaic parameters as a function of cell position on the susbtrate which proves excellent film uniformity. These cells were made by modifying the surface ion density of the HSL PEDOT:PSS layer to retard perovskite crystallization. (Copyrights: [a,b] from [145], Copyright © 2015 John Wiley and Sons Inc.; [c–e] from [140], Copyright © 2015 Elsevier. All figures reprinted with permission)
Figure 10.13 Freedom of design offered by inkjet printing and its applicability in printed solar cells. (a) Schematic representation of printed layers lay-out of organic solar cells in the shape of a Christmas tree, (b) a photograph of a fully inkjet printed ITO-free organic solar cell including the electrodes. (Reprinted with permission from [169]; Copyright © 2015 Royal Society of Chemistry)

Chapter 11

Figure 11.1 (a) Scheme of a DSSC: Photons are absorbed by the photosensitizer (S*/S) (red spots). Excited electrons are injected (S⁺/S*) into the lower-lying conduction band of TiO₂ (grey cycles) and they are carried by means of the anode electrode (SnO₂: F, FTO glass) and the external circuit to the platinum functionalized cathode. Eventually, they are exchanged with the redox couple (I^-/I₃^-) which regenerates the oxidized sensitizer (S+/S). (b) Scheme of a DSSC module with the presence of metal fingers to collect photogenerated electrons from each solar stripe.
Figure 11.2 (a) Scheme of perovskite solar cell with perovskite growth on mesostructured oxides as scaffold and (b) planar structure of perovskite solar cell.
Figure 11.3 Freedom of patterning in DSSC technology by inkjet printing selective components.
Figure 11.4 Procedure of film formation using inkjet printing technology.
Figure 11.5 Thin TiO₂ nanocomposite films made with inkjet process: (a) cross-section image, (b) top view.
Figure 11.6 Inkjet-printed dye molecule on TiO₂ surface using various printing parameters such as the type of solvent (first image from the left).
Figure 11.7 Solar windows based on DSSC technology using dyes for fashioning different aesthetic results.
Figure 11.8 Printing method of electrolytes in DSSCs using an inkjet printer.
Figure 11.9 Inkjet-printed perovskite material on mesoporous TiO₂ film with various printing parameters.
Figure 11.10 (a) Spin-coating and (b) inkjet deposition of CH₃NH₃PbI_3-xCl_x perovskite on inkjet-printed TiO₂ film.
Figure 12.1 Relationship between binary, ternary, and quaternary semiconductors to produce Cu₂ZnSnS₄, starting from a II–VI parent compound. (Reprinted with permission from [11])

Chapter 12

Figure 12.2 Kesterite (left) and stannite (right) structure; Large yellow spheres: S and Se; Small spheres: blue, Cu; yellow, Zn; red, Sn. (Reprinted with permission from [13])
Figure 12.3 (left) Pseudoternary phase diagram showing a very small central area where CZTS forms (reprinted with permission from [18]). (right) The calculated chemical-potential stability diagram of Cu₂ZnSnS₄ in a 2D Cu-rich plane (stable 3D region in inset) (reprinted with permission from [22]).
Figure 12.4 The calculated band alignment between CdS, Cu₂ZnSnS₄, Cu₂ZnSnSe₄ and CuInSe₂. CdS is a commonly used n-type window layer in thin-film solar cells. (Reprinted with permission from [34])
Figure 12.5 (left) Typical device architecture of kesterite CZTSSe solar cell device. (right) TEM cross-sectional image of a typical CZTS solar cell device. (Reprinted with permission from [42])
Figure 12.6 Main processing steps in direct solution coating for kesterite fabrication, including both particulate-based and molecular-based processes.
Figure 12.7 Schematic illustration for fabrication of CZTS device from CZTS NCs ink blade coating and post-sulfurization. (Reprinted with permission from [118])
Figure 12.8 Schematic illustration for fabrication of CZTS device from solution (with 2-methoxyethanol as solvent and chalcogen-containing) coating and post-sulfurization. (Reprinted with permission from [115])

Chapter 13

Figure 13.1 Classification of perovskite solar cells based on their structures.
Figure 13.2 (a) Typical cross-sectional SEM image of a planar FTO/TiO₂/CH₃NH₃PbI₃/spiro-OMeTAD/MoO_x/metal (Ag or Al) solar cell. Comparison of J-V characteristics (b) and IPCE (c) of perovskite CH₃NH₃PbI₃ solar cells using different top-contact structures as indicated. (Reprinted from [18]; Copyright © 2014 API)
Figure 13.3 Band alignment of a typical NiO_x-based perovskite solar cell.
Figure 13.4 (a) The schematic of the NiO-based mesoscopic perovskite solar cell. (b) The current-voltage characteristics of photovoltaic devices made of mesoscopic NiO nc/perovskite/PCBM heterojunction solar cell and planar NiO/perovskite/PC61BM heterojunction solar cells (Reprinted from [24]; Copyright © 2014 NPG)
Figure 13.5 (a) Cross-sectional and (b) top-view SEM image of NiO films deposited by PLD at an oxygen pressure of 200 mTorr. (c) False color cross-sectional SEM image for the inverted planar perovskite solar cell based on nanostructured NiO hole transport film. (d) J-V curve and (e) EQE spectrum for the optimized perovskite cell based on nanostructured NiO hole transport film [30]. (Copyright 2015 Wiley-VCH Verlag GmbH & Co. KgaA)
Figure 13.6 (a) I-V curves of pristine NiO_x and Cu:NiO_x measured by c-AFM. (b) Photoluminescence spectra (excitation at 600 nm) of perovskite (MAPbI₃) films on top of pristine NiO_x (squares), Cu:NiO_x (diamonds), and PEDOT:PSS (dotted line). J-V curves (c) and EQE spectra (d) of perovskite solar cells based on PEDOT:PSS (circles), NiO_x (squares), and Cu:NiO_x (diamonds) hole-transporting layers [34]. (Copyright 2014 Wiley-VCH Verlag GmbH & Co. KgaA)
Figure 13.7 (a) TEM image of the NiOx nanoparticles. (b) Top-view and (c) cross-sectional SEM images of the NiO_x film on ITO substrate. (d) False color cross-sectional SEM image of the NiO_x-based perovskite solar cell. (e) J-V curves for NiO_x-based perovskite solar cells on ITO-glass and ITO-PEN substrates [33]. The inset presents a digital photograph of a flexible inverted planar perovskite solar cell in a PEN substrate. (Copyright © 2016 American Chemical Society)
Figure 13.8 SEM images for an ITO substrate (a) and a CuO_x film on ITO substrate (b). Cross-sectional SEM image (c) and J-V curve (d) for the fabricated CuO_x-based perovskite solar cell [51]. (Copyright © 2016 The Royal Society of Chemistry)
Figure 13.9 (a) Device architecture and (b) corresponding energy band diagram relative to vacuum level of the perovskite solar cell. (c) J-V curves of devices with different HTMs. (d) the ambient device stability of the optimized devices with CuSCN or PEDOT:PSS [65]. (Copyright © 2015 Wiley-VCH Verlag GmbH & Co. KgaA)
Figure 13.10 (a) Device structure of the fabricated device with the a:CuAlO₂ buffer layer. (b) UPS spectra revealing the secondary cut-off regions for PEDOT:PSS (40 nm) and 5, 10, 15 and 20 nm a:CuAlO₂ films. (c) Energy level diagram of the device components along with various thicknesses of a:CuAlO₂. (d) J-V characteristics of the devices with different configurations of a:CuAlO₂/PEDOT:PSS and pristine PEDOT:PSS hole conductors [67]. (Copyright © 2016 The Royal Society of Chemistry)
Figure 13.11 (a) Schematic of device architecture. (b) Cross-sectional SEM image of the device. (c) Energy level diagram of the corresponding materials used in our devices employing different PbS QDs [70]. (Copyright © 2015 The Royal Society of Chemistry)
Figure 13.12 (a) Flowchart of fabrication process for the present PSCs with the PEDOT:PSS-GO:NH₃ layer. (b) UPS spectra of three films. The numbers indicate the second-electron cutoffs of these films. (c) The energy level diagram of the devices using the PEDOT:PSS-GO:NH₃ layer [73]. (Copyright © 2016 American Chemical Society)
Figure 13.13 (a) Schematic and J-V curve characterization of a screen-printed perovskite solar cell with NiO hole transport film [43] (Copyright © 2015 American Chemical Society). (b) Schematic of a fully printed perovskite solar cell with Al₂O₃ separator layer and NiO hole transport film. (c) J-V curves characterization of printed perovskite solar cells with and without NiO layer [42]. (Copyright © 2015 Elsevier)
Figure 13.14 (a) Fabrication process flow for the instant inkjet printing of the CH₃NH₃PbI₃ planar perovskite solar cells. For comparison, a different strategy was used to convert PbI₂ into CH₃NH₃PbI₃ using a separate step 3 and step 4 [79] (Copyright © 2014 Wiley-VCH Verlag GmbH & Co. KgaA). (b) Schematic illustration of a fully printable perovskite solar cell. (c) Blade-coating equipment with as-prepared 10 cm × 10 cm perovksite film [81]. (Copyright © 2015 Wiley-VCH Verlag GmbH & Co. KgaA)

Chapter 14

Figure 14.1 Chemical structure of PEDOT:PSS.
Figure 14.2 Schematic of the transfer process of CVD-prepared graphene onto transparent substrates. (Reproduced with permission from [46])
Figure 14.3 Drawing of the fluidic deposition method exploiting PDMS stamps. Air is extracted through the left syringe, generating a lower pressure that speeds up the capillary flow of the deposited electroless silvering solution. (Reproduced with permission from [86])
Figure 14.4 Schematic illustration of the direct imprinting of thermally reduced Ag NPs via deformation-driven ink injection using the PDMS mold with a “reservoir” design. (Reproduced with permission from [90])
Figure 14.5 Schematic of the fabrication process for Cu electroplated nanowire meshes for transparent conducting electrodes. (a) A layer of electrospun polymer nanofibers is deposited onto a copper frame. (b) The nanofibers are made conductive by noble metal seeding. (c) The second layer of electrospun polymer nanofibers is deposited above the platinum-seeded nanofibers. (d) Only the metal-seeded nanofibers are electroplated by copper. (The second layer of electrospun nanofibers is not electroplated because they are nonconductive without metal seeding.) (e) The electroplated and non-electroplated nanofibers are transferred to a transparent substrate. (f) The nonelectroplated nanofibers are removed by dissolution. (Reprinted with permission from [115])
Figure 14.6 (a) Structure of the ITO-free OPV is glass/WO₃ (40 nm)/Ag (15nm)/WO₃ (20 nm)/P3HT:PCBM/LiF/Al. (b) The structure is ITO/WO₃ (20 nm)/P3HT: PCBM/LiF/Al. (Reproduced with permission from [134])

Chapter 15

Figure 15.1 (a) Schematic illustration of three kinds of PCs (adapted from [11]; Published by The Royal Society of Chemistry). (b) A Hibiscus trionum petal showing iridescence overlying red pigment and its 1D grating structure (adapted from [15]). (c) Dorsal views of the Japanese jewel beetle, Chrysochroa fulgidissima, at various viewing angles and its 1D periodicity in the form of multilayers (adapted with permission from [16]; Copyright © 2005 Wiley-VCH). (d) A photograph of antifogging mosquito eyes and 2D grating structure covering an ommatidial surface (adapted with permission from [18]; Copyright © 2007 Wiley-VCH). (e) A dorsal view of the beetle, Pachyrhynchus argus, and its opal analogue structure (adapted with permission from [19]; Copyright © 2003 Nature Publishing Group). (f) Inverse opal analogous nanostructures generating the iridescence of several species of exotic butterflies such as the Parides sesostris (adapted with permission from [14]; Copyright © 2012 The Royal Society of Chemistry).
Figure 15.2 (a-d) Schematic illustration of spin coating and the 1D PCs prepared by it. (e,f) Schematic illustration of dip coating and the 1D PC prepared by it. (g-i) Schematic illustration of self-assembly at the gas/liquid interface and the 2D PCs prepared by it. (j–l) Schematic illustration of rubbing and the 2D PCs prepared by it. (m-q) Schematic illustration for IO fabrication and different Ios. (Figures (a,b) from [29, 34], Copyright © 2009 Wiley-VCH; Figure (c) from [36], Published by the PCCP Owner Societies; and Figure (d) from [38], Copyright © 2015 American Chemical Society. Figure (e) from [40], Copyright © 2015 Wiley-VCH; and Figure (f) from [41], Copyright © 2007 Wiley-VCH. Figures (g–i) from [51], Copyright © 2012 Wiley-VCH. Figures (j–l) from [54], Copyright © 2014 Wiley-VCH. Figure (n) from [61], Copyright © 2003 American Chemical Society; Figure (o) from [62], Copyright © 2014 Elsevier B.V.; Figure (p) from [6], Copyright © 2010 American Chemical Society; Figure (q) from [67], Copyright © 2011 Nature Publishing Group. All figures adapted with permission.)
Figure 15.3 Schematic illustration of the relative positions of the PCs and the active layer of a solar cell: (a) PCs placed on the shadow side of the active layer, (b) the active layer itself structured as PCs, and (c) PCs placed at the front side of the active layer.
Figure 15.4 Different PC reflectors: (a) Selectively transparent silicon thin film solar cell with 1D Bragg reflectors (adapted from [69]). (b) Transparent, near-infrared organic photovoltaic solar cells with 1D Bragg reflectors. (c) A DSC with porous Bragg reflectors. (d) A DSC with TiO₂ NT PCs and the simulation for its optical properties. (e) A DSC with a 3D TiO₂ IO structure on the top of nc-TiO₂ film. (f) A DSC based on gel electrolytes with a 3D IO structure. (Figure (b) from [70], Copyright © 2011 American Institute of Physics. Figure (c) from [71], Copyright © 2012 The Royal Society of Chemistry. Figure (d) from [1], Copyright © 2015 The Royal Society of Chemistry. Figure (e) from [6], Copyright © 2010 American Chemical Society. Figure (f) from [62]; Copyright © 2014 Elsevier B.V. All figures adapted with permission)
Figure 15.5 (a) The P3HT/PCBM PC structure and its enhanced absorption. (b) The P3HT:PCBM/ZnO PC structure and its enhanced absorption. (c) TDPTD:PCBM/ZnO PC structure fabricated by the PRINT method. (d) Silicon PC structure and its enhanced absorption. (e) A perovskite film with a concentric ring photonic structure and its appearance. (f) Photon management in two-dimensional disorder media. (Figure (a) from [78], Copyright © 2008 American Institute of Physics. Figure (b) from [79], Copyright © 2009 American Institute of Physics. Figure (c) from [82], Copyright © 2009 American Chemical Society. Figure (d) from [87], Copyright © 2010 Elsevier B.V. Figure (e) from [88], Copyright © 2015 The Royal Society of Chemistry. Figure (f) from [91], Copyright © 2012 Nature Publishing Group. All figures adapted with permission)
Figure 15.6 (a) Schematic of the designed PC-organic solar cell and simulated optical properties of the active layer in the PC-organic solar cell compared to that in the conventional organic solar cell (Adapted with permission from [93]; Copyright © 2012 American Institute of Physics). (b) Scheme of a PC-based perovskite solar cell, SEM image of a cross section of a PC-based perovskite solar cell, and colors displayed by devices integrating different PCs (Adapted with permission from [94]; Copyright © 2015 American Chemical Society).
Figure 15.7 (a) Schematic illustration of the photovoltaic system with a PC concentrator. (b) Typical photographs of the PC concentrators with different colors. (c) The absorbance spectrum of the N719 dye (black) and the reflectance spectra of the PC concentrators. (d) The I-V characteristics of the DSCs with different concentrators. (Adapted with permission from [95]; Copyright © 2008 The Royal Society of Chemistry)

List of Tables

Chapter 2

Table 2.1 Classification of semiconductor fabrication techniques (reprinted from [15]).
Table 2.2 Summary of devices partially developed using solution-based methods.
Table 2.3 Thin film basic characterization techniques.

Chapter 6

Table 6.1 Processing time of in-situ annealing and post-annealing treatment at one fabrication cycle [35].

Chapter 7

Table 7.2 Photovoltaic performances of laminated and evaporated top metal electrode P3HT:PCBM BHJ-PSCs.

Chapter 8

Table 8.1 Free carrier density, carrier mobility and local conductivity of the PEDOT chains in the PEDOT:PSS thin films. (Adapted with permission from [25])
Table 8.2 Photovoltaic performance of the mixed-organic-cation perovskite-based solar cells under 1 sun illumination (AM 1.5G, 100mW/cm²). (Adapted with permission from [15])
Table 8.3 Properties of the solvent additives and the modified PEDOT:PSS thin films (Adapted with permission from [28]).

Chapter 10

Table 10.1 Overview of scalable printing and coating methods employed in PeSC research as of Sep 15, 2016. All cells were characterized under 100 mW cm^-² at AM 1.5G. Abbreviations and chemical formulas are expanded in the footnote.*

Chapter 12

Table 12.1 Comparison of the different electrodeposition strategies.

Chapter 13

Table 13.1 Summary of the performances of the reported NiO_x-based organic-inorganic hybrid perovskite solar cells. The word “non” means the parameter was not presented in the paper.

Chapter 14

Table 14.1 Summary of optoelectronic properties of PEDOT:PSS transparent electrode and its application in solar cells.
Table 14.2 Photovoltaic performance of solar cells with graphene or rGO as transparent electrode.
Table 14.3 Photovoltaic performance of solar cells with CNT as transparent electrode.
Table 14.4 Photovoltaic performance of OPVs with metal grids as the transparent electrode.
Table 14.5 Comparison of life circle analysis and cost analysis between ITO and Ag nanowire. Note that these values do not contain the embodied energy or cost of the PET substrate with the exception of the cost of ITO film, which contains the cost of PET [94].
Table 14.6 Photovoltaic performance of solar cells with metal nanowire networks as the transparent electrode.
Table 14.7 Photovoltaic performance of OPVs with ultrathin metal film as the transparent electrode.
Table 14.8 Photovoltaic performance of solar cells with dielectric/metal/dielectric MTFs as the transparent electrode.
Table 14.9 Photovoltaic performance of OPVs with graphene-based MTFs as the transparent electrode.
Table 14.10 Average OPV module performance of 10 different kinds of commercial inks. (Reproduced with permission from [170])
Table 14.11 Photovoltaic performance of P3HT:PCBM-based OPVs with printed silver electrode.

Scrivener Publishing
100 Cummings Center, Suite 541J
Beverly, MA 01915-6106

Advances in Solar Cell Materials and Storage

Series Editors: Nurdan Demirci Sankir and Mehmet Sankir

Scope: Because the use of solar energy as a primary source of energy will exponentially increase for the foreseeable future, this new series on Advances in Solar Cell Materials and Storage will focus on new and novel solar cell materials and their application for storage. The scope of this series deals with the solution-based manufacturing methods, nanomaterials, organic solar cells, flexible solar cells, batteries and supercapacitors for solar energy storage, and solar cells for space.

Submission to the series: Please submit book proposals to Nurdan Sankir at
dnurdan@yahoo.com

Publishers at Scrivener
Martin Scrivener (martin@scrivenerpublishing.com)
Phillip Carmical (pcarmical@scrivenerpublishing.com)

Printable Solar Cells

Edited by

Nurdan Demirci Sankir

Mehmet Sankir