Dye-sensitized Solar Cells

Description

With contributions by: Michael Bertoz, Juan Bisquert, Filippo De Angelis, Hans Desilvestro, Francisco Fabregat-Santiago, Simona Fantacci, Anders Hagfeldt, Seigo Ito, Ke-jian Jiang, K. Kalyanasundaram, Prashant V. Kamat, Ladislav Kavan, Jacques-E. Moser, Md. K. Nazeeruddin, Laurence Peter, Henry J. Snaith, Gavin Tulloch, Sylvia Tulloch, Satoshi Uchida, Shozo Yanagida and Jun-ho Yum Cover Half Title Title Page Copyright Page Table of Contents PREFACE 1: PHOTOCHEMICAL AND PHOTOELECTROCHEMICAL APPROACHES TO ENERGY CONVERSION 1.1 The sun as an abundant energy resource 1.2 Photochemical conversion and storage of solar energy (artificial photosynthesis) 1.3 Photographic sensitization 1.4 Photoelectrochemical conversion of solar energy 1.4.1 Photogalvanic cells 1.4.2 Generations of photovoltaic solar cells 1.4.3 Photoelectrochemical solar cells with liquid junctions 1.4.4 Photoredox reactions of colloidal semiconductors and particulates 1.5 Dye sensitization of semiconductors 1.5.1 Dye sensitization of bulk semiconductor electrodes 1.5.2 Dye-sensitized solar cells – an overview 1.5.3 Sequence of electron-transfer steps of a DSC 1.5.4 Key efficiency parameters of a DSC 1.5.5 Key components of the DSC 1.5.6 Quasi-solid state DSCs with spiro-OMeTAD 1.5.7 Improvement in efficiency through the nanostructuring of materials 1.5.8 Dye solar cells based on nanorods/nanotubes and nanowires 1.5.9 Sensitization using quantum dots 1.5.10 semiconductor-sensitized ETA solar cells 1.5.11 DSCs based on p-type semiconductor 1.6 Conclusions 1.7 References 2: TITANIA IN DIVERSE FORMS AS SUBSTRATES 2.1 Titania: fundamentals 2.2 Electrochemistry of titania: depletion regime 2.2.1 Photoelectrochemistry under band-gap excitation 2.2.2 In-situ FTIR spectroelectrochemistry in the depletion regime 2.2.3 Photoelectrochemistry under sub-band-gap excitation 2.3 Electrochemistry of titania: accumulation regime 2.3.1 Capacitive processes 2.3.2 Li-insertion electrochemistry 2.3.3 Spectroelectrochemistry of titania in the accumulation regime 2.4 Titania photoanode for dye sensitized solar cells 2.4.1 Non-organized titania made by decomposition of Ti(IV) alkoxides 2.4.2 Electrochemical deposition of titania 2.4.3 Aerosol pyrolysis 2.4.4 Organized nanocrystalline titania 2.4.5 Single-crystal anatase electrode 2.4.6 Other methods of producing titania electrodes for DSC 2.4.7 Multimodal structures 2.5 Conclusion 2.6 Acknowledgements 2.7 References 3: MOLECULAR ENGINEERING OF SENSITIZERS FOR CONVERSION OF SOLAR ENERGY INTO ELECTRICITY 3.1 Introduction 3.2 Ruthenium sensitizers 3.2.1 Effect of protons carried by the sensitizers on the performance 3.2.2 Effect of cations in the ruthenium sensitizers on the performance 3.2.3 Device stability 3.2.4 Effect of alkyl chains in the sensitizer on the performance 3.2.5 Effect of the p-conjugation bridge between carboxylic acid groups and the ruthenium chromophore 3.2.6 High Molar Extinction Coefficient Sensitizers 3.2.7 Tuning spectral response by thiocyanato ligands 3.2.8 Non-thiocyanato ruthenium complexes 3.3 Organic sensitizers 3.3.1 High efficiency organic sensitizers 3.3.2 Near-IR absorbing sensitizers 3.4 References 4: OPTIMIZATION OF REDOX MEDIATORS AND ELECTROLYTES 4.1 Introduction 4.2 Charge transfer processes in DSCs 4.3 Electrolyte Components and their roles in the DSCs 4.3.1 Organic solvents 4.3.2 Cations 4.3.3 Additives 4.3.4 Electron mediators 4.4 Ionic liquid, quasi-solid and solid electrolytes 4.4.1 Ionic liquid electrolyte 4.4.2 Active iodide molten salts 4.4.3 Nonactive iodide molten salts 4.4.4 Additives in ILEs 4.4.5 Quasi-solid electrolyte 4.5 Remarks and prospects 4.6 References 5: PHOTOSENSITIZATION OF SnO2 AND OTHER OXIDES 5.1 Dependence of the Sensitization Efficiency on the Energy Difference 5.2 Coupled semiconductor Systems 5.3 SnO2-C60-Ru(bpy)23+ System 5.4 Probing the Interaction of an Excited State Sensitizer with the Redox Couple 5.5 Sensitization of Nanotube Arrays 5.6 Charge Separation of Organic Clusters at an SnO2 Electrode Surface 5.7 Concluding Remarks 5.8 Acknowledgements 5.9 References 6: SOLID-STATE DYE-SENSITIZED SOLAR CELLS Inc.RPORATING MOLECULAR HOLE-TRANSPORTERS 6.1 Introduction 6.2 Spiro-OMeTAD-based solid-state dye-sensitized solar cell 6.3 The influence of additives upon the solar cell performance 6.4 Charge generation: Electron Transfer 6.5 Reductive quenching 6.6 Charge generation: Hole-transfer 6.7 Charge transport in molecular hole-transporters 6.8 Hole mobility in spiro-OMeTAD 6.9 Influence of charge density on the hole-mobility in molecular semiconductors 6.10 The influence of chemical p-doping upon Conductivity and hole-mobility 6.11 The influence of ionic salts on conductivity and hole-mobility 6.12 Current collection 6.13 TiO2 pore filling with molecular hole-transporters 6.14 Charge recombination: The influence of additives 6.15 Charge recombination: Ion solvation and immobilization 6.16 Charge recombination: Controlling the spatial separation of electrons and holes at the heterojunction 6.17 Enhancing light capture in solid-state DSCs 6.18 Alternative structures for mesoporous and nanostructured electrodes in solid-state DSCs 6.19 Outlook for hole-transporter based solid-state DSCs 6.20 References 7: PACKAGING, SCALE-UP AND COMMERCIALIZATION OF DYE SOLAR CELLS 7.1 Introduction 7.2 From cells to panels 7.2.1 Definitions 7.2.2 Designs 7.2.3 Materials 7.2.4 Module performance - experiment vs. modeling 7.3 Long-term stability - the key to industrial success 7.3.1 Single cells 7.3.2 Modules 7.3.3 Panels 7.4 Scaling up to commercial production levels 7.4.1 Material costs and availability 7.4.2 Manufacturing 7.5 Commercial applications 7.6 Conclusions 7.7 Acknowledgements 7.8 References 8: HOW TO MAKE HIGH-EFFICIENCY DYE-SENSITIZED SOLAR CELLS 8.1 Introduction 8.2 Experimental considerations 8.2.1 Preparation of screen-printing pastes 8.2.2 Synthesis of Ru-dye 8.2.3 Porous-TiO2 electrodes 8.2.4 Counter-Pt electrodes 8.2.5 DSC assembling 8.2.6 Measurements 8.3 Results and discussion 8.3.1 TiCl4 treatments 8.3.2 Effect of the light-scattering TiO2 layer 8.3.3 Thickness of the nanocrystalline TiO2 layer 8.3.4 Anti-reflecting film 8.3.5 Reproducibility of DSC photovoltaics 8.4 Conclusion 8.5 Acknowledgements 8.6 References 9: SCALE-UP AND PRODUCT-DEVELOPMENT STUDIES OF DYE-SENSITIZED SOLAR CELLS IN ASIA AND EUROPE 9.1 Introduction 9.2 Scaling up of laboratory cells to modules and panels 9.3 DSC development studies in various european laboratories 9.3.1 Energy Research Centre of the Netherlands (ECN) 9.3.2 Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE) 9.3.3 G24 Innovation 9.3.4 3GSolar, Israel 9.4 DSC development studies in various laboratories of Japan 9.4.1 Aisin Seiki Co. Ltd. and Toyota Central R&D Laboratories 9.4.2 Fujikura Ltd. (Japan) 9.4.3 Peccell Technologies, Inc. (Japan) 9.4.4 Sharp Co. Ltd. (Japan) 9.4.5 Sony Corporation Ltd. (Japan) 9.4.6 Shimane Institute for Industrial Technology (Japan) 9.4.7 TDK Co., Ltd. (Japan) 9.4.8 Eneos Co. Ltd. (Japan) 9.4.9 NGK Spark Plug Co., Ltd. (Japan) 9.4.10 Panasonic Denko Co. Ltd. (Japan) 9.4.11 Taiyo Yuden Co., Ltd. (Japan) 9.4.12 Dai Nippon Printing Company 9.4.13 Mitsubhishi Paper Mills and Sekisui Jushi Corporation 9.4.14 J-Power Co. Ltd. (Japan) 9.5 DSC Development Work in Korea and Taiwan 9.5.1 Korean Institute of Science and Technology (KIST) 9.5.2 Electronics and Telecommunications Research Institute (ETRI), Korea 9.5.3 Samsung SDI, Korea 9.5.4 Industrial Technology Research Institute of Taiwan (ITRI) 9.5.5 J Touch Taiwan 9.6 DSC development work in Australia and China 9.6.1 Dyesol, Australia 9.6.2 Institute of Plasma Physics, Chinese Academy of Sciences 9.7 Conclusion 9.8 Acknowledgement 9.9 References 10: CHARACTERIZATION AND MODELING OF DYE-SENSITIZED SOLAR CELLS: A TOOLBOX APPROACH 10.1 Introduction 10.2 Theoretical background 10.2.1 Interfacial electron transfer processes in the DSC 10.2.2 Electron trapping in the DSC 10.2.3 Electron transport in the DSC 10.3 The toolbox 10.3.1 Determination of injection efficiency and electron diffusion length under steady-state conditions 10.3.2 Electrochemical and spectrolectrochemical techniques to study the energetics of the oxide/dye/electrolyte interface 10.3.3 Electrochemical measurements with thin layer cells 10.3.4 Small-amplitude time-resolved methods 10.3.5 Methods based on frequency response analysis 10.3.6 Photovoltage decay 10.3.7 Determination of density of trapped electrons in DSCs 10.3.8 Measuring the internal electron quasi Fermi level in the DSC 10.3.9 Determining the electron diffusion length using IMVS and IMPS 10.3.10 Photoinduced absorption spectroscoy (PIA) 10.3.11 Conclusions 10.4 Acknowledgments 10.5 Appendix 1 Analytical IMPS solutions 10.6 Appendix 2 Numerical solutions of the continuity equation [10.115] 10.7 References 11: DYNAMICS OF INTERFACIAL AND SURFACE ELECTRON TRANSFER PROCESSES 11.1 Introduction 11.2 Energetics of charge transfer reactions 11.2.1 Mesoscopic metal oxide semiconductors 11.2.2 Dye sensitizer 11.3 Kinetics of interfacial electron transfer 11.3.1 Charge injection dynamics 11.3.2 Charge recombination 11.4 Electron transfer dynamics involving the redox mediator 11.4.1 Kinetics of interception of dye cations by a redox mediator 11.4.2 Conduction band electron – oxidized mediator recombination 11.4.3 Rlectron transport in nanocrystalline TiO2 films 11.5 References 12: IMPEDANCE SPECTROSCOPY: A GENERAL INTRODUCTION AND APPLICATION TO DYE-SENSITIZED SOLAR CELLS 12.1 Introduction 12.2 A basic solar cell model 12.2.1 The ideal diode model 12.2.2 Physical origin of the diode equation for a solar cell 12.3 Introduction to IS methods 12.3.1 Steady state and small perturbation quantities 12.3.2 The frequency domain 12.3.3 Simple equivalent circuits 12.4 Basic physical model and parameters of IS in solar cells 12.4.1 Simplest impedance model of a solar cell 12.4.2 Measurements of electron lifetimes 12.5 Basic physical models and parameters of IS in dye-sensitized solar cells 12.5.1 Electronic processes in a DSC 12.5.2 The capacitance of electron accumulation in a DSC 12.5.3 Recombination resistance 12.5.4 The transport resistance 12.6 Transmission line models 12.6.1 General structure of transmission lines 12.6.2 General diffusion transmission lines 12.6.3 Diffusion-recombination transmission line 12.6.4 Parameters of the diffusion-recombination model 12.6.5 Effect of boundaries on the transmission line 12.7 Applications 12.7.1 Liquid electrolyte cells 12.7.2 Experimental IS parameters of DSCs 12.7.3 Nanotubes 12.7.4 Effects of the impedance parameters on the j-V curves 12.8 Acknowledgments 12.9 Appendix: properties of measured DSCs 12.10 References 13: THEORETICAL AND MODEL SYSTEM CALCULATIONS 13.1 Introduction 13.2 Theoretical and computational methods 13.2.1 Density Functional Theory (DFT) 13.2.2 Basis sets 13.2.3 The Car-Parrinello method 13.2.4 Solvation effects 13.2.5 Excited states 13.2.6 Nonadiabatic method 13.3 Dye sensitizers 13.3.1 Ruthenium(II)-polypyridyl sensitizers 13.3.2 Calculations on N3 13.3.3 Calculations on other Ru(II)-dye sensitizers 13.3.4 Trans-complexes 13.3.5 Organic sensitizers 13.3.6 Squaraine dyes 13.4 Studies of the TiO2 substrate 13.4.1 TiO2 models 13.5 Dye sensitizers on TiO2 13.5.1 Organic dyes on TiO2: adsorption and electron dynamics 13.5.2 Inorganic dyes on TiO2: adsorption and excited states 13.6 Conclusions and perspective 13.7 References INDEX