Crystalline Silicon Solar Cells: Carbon to Silicon ― A Paradigm Shift in Electricity Generation, Volume 1

Description

This book focuses on crystalline silicon solar cell science and technology. It is written from the perspective of an experimentalist with extensive hands-on experience in modeling, fabrication, and characterization. A practical approach to solar cell fabrication is presented in terms of its three components: materials, electrical, and optical. The materials section describes wafer processing methods including saw damage removal, texturing, diffusion, and surface passivation. The electrical section focuses on formation of ohmic contacts on n and p-doped surfaces. The optical section illustrates light interaction with textured silicon surfaces in terms of geometrical, diffractive and physical optics, transmission, and surface photovoltage (SPV) spectroscopy. A final chapter analyzes performance of solar cells, fabricated with a wide range of process parameters. A brief economic analysis on the merits of crystalline silicon-based photovoltaic technology as a cottage industry is also included. Preface Acknowledgements About the Book Contents About the Author Chapter 1: Sustainable Electricity Generation 1.1 Energy and Economics 1.2 Electricity Generation and Distribution 1.3 Crystalline Silicon PV Technology 1.3.1 Crystalline Silicon Supply Chain 1.3.2 Economic Benefits of Investment in Silicon 1.4 Introduction to Solar Cells 1.5 Review of Crystalline Si Solar Cells 1.5.1 Efficiency Review 1.5.2 Manufacturing Cost 1.5.3 Wafer Thickness 1.6 Crystalline Si Solar Cell Simulations 1.7 Low Temperature Processing 1.7.1 Low Temperature ITO/c-Si Contacts 1.7.2 Laser Processing References Chapter 2: Solar Cell Processing 2.1 Saw Damage Removal 2.2 Alkaline Texturing 2.3 Acidic Texturing 2.3.1 Etch Rate Dependence on Concentration and Temperature 2.3.2 Texturing Process in HNA System Influence of H2O2 on Texturing Influence of Acetic Acid on Texturing Laser Damage Removal Etching Along Grain Boundaries 2.4 Plasma Reactive Ion Texturing 2.4.1 Metal-Assisted Random Reactive Ion Texturing of Silicon 2.4.2 Texture Evolution and Damage Removal 2.5 POCl3 Diffusion 2.6 Plasma Implantation 2.6.1 Plasma Implantation System 2.6.2 Profiles of Plasma-Implanted Boron 2.6.3 Profiles of Plasma-Implanted Phosphorous 2.7 Phosphoric Acid Diffusion 2.8 Passivation and AR Film Deposition 2.8.1 In Situ SiO2 2.8.2 Ex Situ SiO2 2.8.3 Ex Situ SiO2 on H3PO4-Doped Surface 2.8.4 PECVD SiN on POCl3-Doped Surface 2.8.5 ITO on POCl3-Doped Surface 2.9 Screen Printing 2.9.1 Screen Printer Modification References Chapter 3: Optical Interactions 3.1 Geometrical Optics 3.2 Diffractive Optics 3.3 Optical Response of Subwavelength Periodic Structures 3.4 Polarization and Anti-reflection Response of Subwavelength Periodic Structures 3.4.1 Hemispherical Reflectance 3.5 Software Simulations Using GSOLVERTM 3.5.1 Diffractive Optics for Enhanced IR Absorption 3.5.2 Physical Optics for Enhanced IR Absorption 3.5.3 Physical Optics for Enhanced IR Absorption in Thin Films Optical Absorption as a Function of Depth Optical Absorption as a Function of Period Optical Absorption as a Function of Profile Summary of Optical Absorption Calculations 3.6 Measured Optical Absorption in Thin Films 3.7 Reflection and Absorption in Randomly Textured Surfaces 3.8 Fourier Analysis of Randomly Textured Surfaces 3.9 Reflection and Absorption in 50-100-μm-Thick Films 3.10 Optical Transmission 3.11 Lifetime and Surface Recombination Velocity Characterization 3.11.1 Photoconductive Decay Method 3.11.2 Surface Photovoltage Method 3.11.3 Bandgap Photo- and Electroluminescence Methods 3.11.4 Sub-band Photoluminescence 3.12 Diffusion Length Measurements with Surface Photovoltage 3.12.1 Experimental Apparatus 3.12.2 Surface Photovoltage Measurements on Silicon Wafers References Chapter 4: Metallization in Solar Cell 4.1 Resistance Measurements in Si Wafers 4.2 Resistivity Measurements of Metal/Si Interface 4.2.1 Resistivity Measurements in Vertical Configuration 4.2.2 Resistivity Measurements in Lateral Configuration 4.3 Geometric Configurations 4.4 Thermal Annealing Configurations 4.4.1 Conveyor Belt IR RTA Furnace 4.4.2 Parallel-Plate Furnace 4.4.3 Quartz Tube Furnace 4.4.4 Radial Furnace 4.4.5 Summary of Annealing Configurations 4.5 Experimental Results 4.5.1 TLM Pattern Calibration 4.5.2 Variation with Texture 4.5.3 Variation with Area 4.5.4 Variation with Distance 4.5.5 Variation with Largest Areas and Distances 4.6 Aluminum Contact Variation with Annealing Configurations 4.6.1 Al/Si Contact in Radial Furnace 4.6.2 Al/Si Contact in Quartz Tube Furnace 4.6.3 Al Contact in RTA Furnace 4.6.4 Al Contact in Parallel-Plate Furnace 4.6.5 Summary of Al/Si Contact Formation 4.7 Silver Contact Variation with Annealing Configurations 4.7.1 Ag/Si Contact in Radial Furnace 4.7.2 Ag/Si Contact in Quartz Tube Furnace 4.7.3 Ag/Si Contact in Conveyor Belt Furnace 4.7.4 Ag/Si Contact in Parallel-Plate Furnace 4.7.5 Summary of Ag/Si Contact Formation 4.8 Morphological Analysis of Al/Si Interface 4.8.1 Microstructural Analysis of RTA-Annealed Interface 4.8.2 Microstructural Analysis of Quartz Furnace-Annealed Interface 4.8.3 Compositional Analysis of Annealed Interface 4.8.4 Contact Formation Mechanisms 4.8.5 Resistivity Variation 4.8.6 Summary of Al/Si Interface 4.9 Morphological Analysis of Ag/Si Interface 4.9.1 Microstructural Analysis of RTA-Annealed Interface 4.9.2 Microstructural Analysis of Quartz Furnace-Annealed Interface 4.9.3 Compositional Analysis of Annealed Interface 4.9.4 Phenomenological Model 4.9.5 Silver Silicide Alloyed Contact 4.9.6 Silicon Diffusion into Silver Paste 4.9.7 Micro- and Nano-Ag/Si Crystallite Growth 4.9.8 Resistivity Variation with Glass Composition 4.10 Al/Si Contact Resistance in Vertical Configuration 4.11 Al/Si Interface After Al Removal 4.12 Ag/Si Contact Resistance in Vertical Configuration 4.13 Ag/Si Interface After Ag Removal 4.14 Final Considerations References Chapter 5: Dark Current-Voltage Characterization 5.1 PC1D Current-Voltage Simulations 5.1.1 Ohmic Contacts 5.1.2 Rectifying Contacts 5.2 Measurement Methodology 5.2.1 Current-Voltage Measurements on Ohmic Contacts 5.2.2 Current-Voltage Measurements on Rectifying Contacts 5.2.3 Current-Voltage Response Variation with Annealing Configurations Conveyor Belt IR RTA Parallel-Plate RTA Quartz Tube Furnace Anneal Round Tube Furnace Anneal 5.3 Summary References Chapter 6: Solar Cell Characterization 6.1 Periodically Textured Solar Cell Characterization 6.2 Randomly Textured Solar Cell Characterization 6.2.1 Silicon Cathode Texture 6.2.2 Aluminum-Assisted Texture 6.2.3 Conditioned Texture on Graphite Cathode 6.2.4 Summary of Internal Quantum Efficiency Measurements 6.3 Light-Current-Voltage Measurement Method 6.4 In Situ Oxide Passivated Solar Cell 6.5 RIE-Textured Solar Cell on 100-μm-Thick n-Si Substrate 6.6 In Situ Oxide Passivated Solar Cell on n-Si Substrate 6.7 Thermal Oxide Passivated Solar Cell 6.8 Thermal Oxide Passivated Solar Cell with H3PO4 Diffusion 6.9 Solar Cell with Indium Tin Oxide Film 6.10 Ion-Implanted Solar Cells 6.10.1 Emitter Formation on RIE-Textured Surfaces 6.10.2 Plasma Ion Implantation 6.11 Summary of Results 6.11.1 Smart Solar Cell Process 6.11.2 Dry Solar Cell Process 6.11.3 Thin Solar Cell Process References Index