Thin Film Solar Cells Fabrication, Characterization and Applications

Transcription

1 Thin Film Solar Cells Fabrication, Characterization and Applications Edited by Jef Poortmans and Vladimir Arkhipov IMEC, Leuven, Belgium John Wiley & Sons, Ltd

2 Contents Series Preface Preface xiii xv 1 Epitaxial Thin Film CrystaUine Silicon Solar Cells on Low Cost Silicon Carriers 1 Jef Poortmans 1.1 Introduction Deposition Technologies Thermally Assisted Chemical Vapor Deposition Liquid Phase Epitaxy - Electrodeposition Close Space Vapor Transport Technique Ion Assisted Deposition Low Energy Plasma Enhanced Chemical Vapor Deposition/Electron Cyclotron Resonance Chemical Vapor Deposition Silicon Based Epitaxial Layer Structures for Increased Absorbance Epitaxial Growth on Textured Substrates Silicon-Germanium Alloys Germanium-Silicon Structures Epitaxial Layers on a Buried Backside Reflector Epitaxial Solar Cell Results and Analysis Laboratory Type Epitaxial Solar Cells Industrial Epitaxial Solar Cells Special Epitaxial Solar Cell Structures High Throughput Silicon Deposition Chemical Vapor Deposition Reactor Upscaling Liquid Phase Epitaxy Reactor Upscaling Conclusions 32 References 32 2 CrystaUine Silicon Thin Film Solar Cells on Foreign Substrates by High Temperature Deposition and Recrystallization 39 Stefan Reber, Thomas Kieliba, Sandra Bau 2.1 Motivation and Introduction to Solar Cell Concept Substrate and Intermediate Layer 42 Thin Film Solar Cells Edited by J. Poortmans and V. Arkhipov 2006 John Wiley & Sons, Ltd

3 Vlll CONTENTS Substrate Intermediate Layer Zone Melting Recrystallization Introduction Zone Melting Recrystallization Film Growth Features of Silicon Layers Recrystallized by Zone Melting Recrystallization Development of Lamp Heated Zone Melting Recrystallization Processors Zone Melting Recrystallization on Ceramic Substrates Silicon Deposition Requirements of Silicon Deposition for Photovoltaics Some Basics on Thermal Silicon Atmospheric Pressure Chemical Vapor Deposition from Chlorosilanes R&D Trends in Silicon Atmospheric Pressure Chemical Vapor Deposition for Photovoltaics Silicon Chemical Vapor Deposition on Ceramic Substrates Solar Cells on Foreign Substrates Options for Solar Cell Fabrication Solar Cells on Model Substrates Solar Cells on Low Cost Substrates Summary and Outlook 85 Acknowledgments 87 References 87 3 Thin Film Polycrystalline Silicon Solar Cells 97 Guy Beaucarne, Abdellilah Slaoui 3.1 Introduction Definition Why Polycrystalline Thin Film Silicon Solar Cells? Potential of Polysilicon Solar Cells Light Confinement Diffusion Length Modeling Substrates for Polysilicon Cells Film Formation Initial Step for Grain Size Enhancement Techniques for Active Layer Formation Defect Density and Activity Solar Cell and Module Processing Device Structure Junction Formation Defect Passivation Isolation and Interconnection Polysilicon Solar Cell Technologies Solid Phase Crystallization Heterojunction with Intrinsic Thin Layer Solar Cells Surface Texture and Enhanced Absorption with Back Reflector Solar Cells 121

4 CONTENTS ix Crystalline Silicon on Glass Technology Other Research Efforts Around the World Conclusion 123 References Advances in Microcrystalline Silicon Solar Cell Technologies 133 Evelyne Vallat-Sauvain, Arvind Shah and Julien Bailat 4.1 Introduction Microcrystalline Silicon: Material Fabrication and Characterization Microcrystalline Silicon Deposition Techniques Undoped Microcrystalline Layers Doped Layers Microcrystalline Silicon Solar Cells Light Management Issues Single Junction Microcrystalline Silicon Solar Cells Tandem Amorphous/Microcrystalline Silicon Solar Cells: The Micromorph Concept Conclusions 163 References Advanced Amorphous Silicon Solar Cell Technologies 173 Miro Zeman 5.1 Introduction Overview of Amorphous Silicon Solar Cell Technology Development and Current Issues s s s After Current Technology Issues Hydrogenated Amorphous Silicon, Atomic Structure Density of States Models for the Density of States and Recombination-Generation Statistics Optical Properties Electrical Properties Determination of Density of States Metastability Hydrogenated Amorphous Silicon from Hydrogen Diluted Silane Doping of Hydrogenated Amorphous Silicon Alloying of Hydrogenated Amorphous Silicon Deposition of Hydrogenated Amorphous Silicon Radio Frequency Plasma Enhanced Chemical Vapor Deposition Direct Plasma Enhanced Chemical Vapor Deposition Techniques Remote Plasma Enhanced Chemical Vapor Deposition Techniques Hotwire Chemical Vapor Deposition 203

5 X CONTENTS 5.5 Amorphous Silicon Solar Cells Hydrogenated Amorphous Silicon Solar Cell Structure Hydrogenated Amorphous Silicon Solar Cell Configurations Design Approaches for Highly Efficient Solar Cells Light Trapping and Transparent Conductive Oxides Degradation of Hydrogenated Amorphous Silicon Solar Cells Multijunction Hydrogenated Amorphous Silicon Solar Cells Performance and Fabrication of Hydrogenated Amorphous Silicon Based Modules Energy Yield Fabrication of Hydrogenated Amorphous Silicon Based Modules Plasma enhanced Chemical Vapor Deposition Systems Applications Outlook 229 Acknowledgments, 230 References Chalcopyrite Based Solar Cells 237 Reiner Klenk, Martha Ch. Lux-Steiner 6.1 Introduction Potential of Chalcopyrite Photovoltaic Modules Technology for the Preparation of Chalcopyrite Solar Cells and Modules Absorber Contacts Characterization and Modeling CellConcept Carrier Density and Transport Loss Mechanisms Scaling Up and Production Cost Estimations Module Performance Sustainability Developing Future Chalcopyrite Technology Lightweight and Flexible Substrates Cadmium Free Cells Indium Free Absorbers Novel Back Contacts Bifacial Cells and Superstrate Cells Nonvacuum Processing Wide Gap and Tandem Cells 265 References Cadmium Telluride Thin Film Solar Cells: Characterization, Fabrication and Modeling 277 Marc Burgelman 7.1 Introduction 277

6 CONTENTS xi 7.2 Materials and Cell Concepts for Cadmium Telluride Based Solar Cells Optical Properties of Cadmium Telluride Electrica! Properties of Cadmium Telluride The Buffer Material: Cadmium Sulfide Window Materials for Cadmium Telluride Based Solar Cells Research Areas and Trends in Cadmium Telluride Solar Cells The Activation Treatment of Cadmium Telluride The Back Contact Structure Environmental Issues Other Research Areas and Trends Fabrication of Cadmium Telluride Cells and Modules Deposition Methods for Cadmium Telluride Based Solar Cells Design of Series Integrated Cadmium Telluride Modules Production of Cadmium Telluride Solar Modules Advanced Characterization and Modeling of Cadmium Telluride Solar Cells Characterization and Modeling: Introduction Characterization Methods for Cadmium Telluride Materials and Cells Modeling of Thin Film Cadmium Telluride Solar Cells Conclusions 314 Acknow ledgments 314 References Charge Carrier Photogeneration in Doped and Blended Organic Semiconductors 325 Vladimir I. Arkhipov, Heinz Bässler 8.1 Introduction Exciton Dissociation in Neat and Homogeneously Doped Random Organic Semiconductors Intrinsic Photogeneration in Conjugated Polymers Sensitized Photogeneration of Charge Carriers in Homogenously Doped Conjugated Polymers Photogeneration of Charge Carriers at a Donor-Acceptor Interface Models of Exciton Dissociation in Homogeneously Doped Conjugated Polymers and in Polymer Based Donor/Acceptor Blends The Onsager-Braun Model Exciton Dissociation in Conjugated Polymers Homogeneously Doped with Electron Scavengers Exciton Dissociation at a Polymer Donor/Acceptor Interface Conclusions 357 References Nanocrystalline Injection Solar Cells 363 Michael Grätzel 9.1 Introduction Band Diagram and Operational Principle of the Dye Sensitized Solar Cell 364

7 Xll CONTENTS 9.3 The Importance of the Nanostructure Light Harvesting by a Sensitizer Monolayer Adsorbed on a Mesoscopic Semiconductor Film Enhanced Red and Near Infrared Response by Light Containment Light Induced Charge Separation and Conversion of Photons to Electric Current Charge Carrier Collection Quantum Dot Sensitizers Photovoltaic Performance of the Dye Sensitized Solar Cell Photocurrent Action Spectra Overall Conversion Efficiency Under Global AM 1.5 Standard Reporting Conditions Increasing the Open Circuit Photovoltage Development of New Sensitizers and Redox Systems Solid State Dye Sensitized Solar Cells Dye Sensitized Solar Cell Stability Criteria for Long Term Stability of the Dye Kinetic Measurements Recent Experimental Results on Dye Sensitized Solar Cell Stability First Large Scale Field Tests and Commercial Developments Future Prospects 384 Acknowledgments 384 References Charge Transport and Recombination in Donor-Acceptor Bulk Heterojunction Solar Cells 387 A. J. Mozer, N. S. Sariciftci 10.1 Introduction Development of Bulk Heterojunction Solar Cells Bulk Heterojunction Solar Cells Operational Principles Nanomorphology-Property Relations Improving the Photon Harvesting Charge Carrier Mobility and Recombination Measurement Techniques Charge Transport in Conjugated Polymers Charge Transport and Recombination in Bulk Heterojunction Solar Cells Summary 421 Acknowledgments 421 References The Terawatt Challenge for Thin Film Photovoltaics 427 Ken Zweibel 11.1 Prologue 'The Only Big Number Out There TW (Quote, Nate Lewis, 2004) 428

8 CONTENTS xiii 11.3 Low Cost and the Idea of Thin Films 11.4 A Bottom Up Analysis of Thin Film Module Costs Approach Results 11.5 Other Aspects of the 'Terawatt Challenge' 11.6 Risks and Perspective Acknowledgments Appendix 11.1 Appendix 11.2 References Index 463