RECENT TRENDS IN PHOTOVOLTAICS TECHNOLOGY: CRYSTALLINE WAFERS VERSUS FLEXIBLE THIN FILMS Saleem H. Zaidi, Gratings, Inc., Nov. 6, 2008 OUTLINE � Motivation � Silicon PV Technology Growth and Trends � Conventional Manufacturing (a) Automated Manufacturing (b) Thin Film Manufacturing � Cottage Industry Approach (a) Application to 110 W Panel Manufacturing � Silicon Solar Research Directions (a) Water-free Manufacturing (b) Crystalline Thin-Films Grating structures for novel applications
ACKNOWLEDGEMENTS � Sam McCormack, Richard Marquardt, Matt Channon, Robert Ellis, Karen DeZetter, Laure Koltunski, David Modisette, Rich Winder, Rajiv Prinja, Abdul Latif, Gary Begay, Bernard Stuart, Dr. J. Tringe, and Prof. K. Sopian � Prof. S. Brueck, Dr. James Lyke, James Gee, Dr. D. Ruby, John Wohlgemuth, and Steve Rockholm � NSF, DoD, Sandia National Labs, UKM, and AFRL � BP Solar, Adventsolar, LMCO Grating structures for novel applications
INTRODUCTION TO GRATINGS � Turn-key solar cell and module manufacturing systems � Multi-vapor etching systems � Pulsed laser annealing systems � Solar cells and Modules � Nanostructures Grating structures for novel applications
INTRODUCTION TO GRATINGS Laser-etched Si nanostructure Au nanospheres Thru Features 6-inch diameter Solar Cell 110 W Panel Grating structures for novel applications
GLOBAL ELECTRICITY GENERATION Green Land Russia USA China Africa Australia � United States 3816 billion KWh Annually � Pakistan 66 billion KWh Annually � Tanzania 1 billion KWh Annually Grating structures for novel applications
ELECTRICITY GENERATION VS GDP � Higher energy usage leads to higher income � Most of the world at much lower income � Quality-of-life linked to energy usage Grating structures for novel applications
ELECTRICITY GENERATION IN ASIA � India and China will generate most electricity � Coal usage will lead to environment degradation � Climate is globally linked Grating structures for novel applications
PARADIGM SHIFT IN ELECTRICITY GENERATION FUNDAMENTAL ASSUMPTIONS � Access to electricity is fundamental human right and responsibility � Energy generation must be at the point of use � Transition from macro grids (hundreds of miles) to nano grids (~ mile) � Power plants from ~ 100s MW capacity to ~ 1 MW capacity � Renewable PV technology to by-pass carbon-based fuels Grating structures for novel applications
COTTAGE INDUSTRY APPROACH TO PHOTOVOLTAICS FUNDAMENTAL ASSUMPTIONS � A solar cell is just a large area diode � Manufacturing model based on IC model is not needed � Energy conversion costs ($/W) is the key parameter � PV technology is adaptable to a society’s technological level � Investment in PV technology infrastructure (education, economy) � PV technology creates jobs Grating structures for novel applications
Grating structures for novel applications ~ 2-5 kW BIPV PV RESIDENTIAL APPLICATIONS
PV INDUSTRIAL APPLICATIONS Agriculture ~ 0.1-1 kW Power Plant Industrial ~ 1 M W ~ 0.1-1 M W Grating structures for novel applications
PV INDUSTRY OVERVIEW PV Power in MW PV Power in MW Cumulative PV Power From 1990-2005 PV Power From 2001-2005 � Sustained Growth over Last 15 Years � Grid-integrated PV is dominant � Off-grid is economically profitable today! Grating structures for novel applications
PV GENERATION SECTORS IN USA 2005 installations ~ 100 MW � Grid-connected ~ 90 % of the Total � Significant residential and commercial sectors � Off-grid growth is ~ 10 % of total Grating structures for novel applications
IMPACT OF SUBSIDIES ON PV GENERATION Residential Programs in Japan � PV Growth is dependent on subsidies � Costs in Grid-connected regions still too high � Off-grid regions, PV is the most economical Grating structures for novel applications
PV GENERATION BY TECHNOLOGY SECTORS � Multicrystalline Si is Dominant � Monocrystalline Si share has increased � Thin-film technologies have reduced Grating structures for novel applications
PROJECTED PV GROWTH IN NEXT FEW YEARS 3.25 GW Generation 4 GW Generation � Germany and Japan will lead growth � China will compete strongly � ROW and US may lag behind Grating structures for novel applications
PV INDUSTRY OUTLOOK --- Wall Street Analysis Grid-Parity ~ 2015 � � Huge financial growth in 2003 to 2008 with competing technologies � Period of consolidation 2009 through 2012 � Financial activity will rebound, partly from merger and acquisition Grating structures for novel applications
PRINCIPAL PV TECHNOLOGY SECTORS � Raw material to purified Si � Mono/poly silicon wafers from feedstock � Wafer processing into solar cells � Solar cell packaging into modules � Module arrays for system integration Grating structures for novel applications
PV TECHNOLOGY SECTOR: SILICON PURIFICATION Raw SiO 2 produced by Mining Purified Silicon Feedstock � Si is the 2 nd most abundant element on earth; � Si is ~ 25.7 % of Earth’s mass � Si is capable of supplying all our Energy Grating structures for novel applications
MAJOR PRODUCERS OF PURIFIED SILICON SUMMARY 2005 Hemlock 7,700 Wacker Polysilicon 5,600 REC 5,550 Tokuyama 5,200 MEMC 3,800 Mitsubishi Materials 1,600 Mitsubishi Polysilicon 1,260 Sumitomo Titanium 700 Other 220 TOTAL 31,630 � Very expensive to produce purified Si � Dominated by few companies � Production of feedstock in tonnes annually Grating structures for novel applications
PV TECHNOLOGY SECTOR: MONOCRYSTALLINE AND POLYCRYSTALLINE SILICON MANUFACTURING � Critical Technology Cast Growth � Wafer Poly-Si manufacturing: key to success � Mono-Si superior to and more expensive than Poly-Si CZ-Growth � Gratings focus on Mono-Si mono-Si Grating structures for novel applications
BRIEF INTRO TO SILICON SOLAR CELL Solar Spectrum on Earth Basic Cell Configuration � Converts sunlight into electricity � Silicon Wafer is processed into solar cell � Current Extraction uses Screen Printing and Electroplating � Optical Absorption in thinner wafers using 3D Structures � Cell Efficiencies ~ 10-20 % range Grating structures for novel applications
PRINCIPAL SOLAR CELL MANUFACTURING STEPS Damage Removal NOTES: � Technology Trend: Thinner Wafers and Dry Processing � Need for Low-Thermal Budget Processes � Replacement of Screen-Printing by Electroplating � High throughput using Automated Equipment Grating structures for novel applications
LARGE VOLUME, HIGH COST MANUFACTURING APPROACH USING TURNKEY SYSTEMS Automated Acid Etch System � Following IC manufacturing model � High throughput to meet profitability Grating structures for novel applications
LARGE VOLUME, HIGH COST MANUFACTURING APPROACH USING TURNKEY SYSTEMS Automated Diffusion System � Several approaches are used � POCl 3 produces best results Grating structures for novel applications
LARGE VOLUME, HIGH COST MANUFACTURING APPROACH USING TURNKEY SYSTEMS Automated Edge Isolation System Automated Nitride System � Several process approaches � Proprietary and commercial systems � PECVD nitride is often the most expensive machine Grating structures for novel applications
LARGE VOLUME, HIGH COST MANUFACTURING APPROACH USING TURNKEY SYSTEMS Contact Firing System Screen Printing System � Low-cost screen printing options available � Contact firing system is unique to screen printing Grating structures for novel applications
LARGE VOLUME, HIGH COST MANUFACTURING APPROACH USING TURNKEY SYSTEMS Automated Solar Cell Tester � High Throughput � Robotics for Cell Transfer and Sorting Grating structures for novel applications
SOLAR CELL MANUFACTURING CHALLENGES � High wafer cost relative to conventional fuels � Wafer supplies for smaller companies � High wafer costs � High startup costs in extensive automation � Harmful Chemicals � Extensive water usage � Lack of Innovation due to cost considerations Grating structures for novel applications
THIN-FILM CIGS MANUFACTURING PROCESS � Large area vacuum equipment � High power lasers Grating structures for novel applications
TYPICAL CIGS PRODUCTION LINE � Startup costs ~ US $ 30 million � Annual production ~ 10 MW/year Grating structures for novel applications
RETURN ON INVESTMENT PROJECTIONS � High profitability � High initial investment Grating structures for novel applications
LOW COST MANUFACTURING PROCESS � Modular approach � Step-wise process characterization � Efficiency ~ 15-18 % range Grating structures for novel applications
SURFACE TEXTURING FOR PERFORMANCE ENHANCEMENT RIE Texture Wet-Chemical Texture Spectral Reflectance Cell Eff. Open Short Fill Description (%) Circuit Circuit Factor Voltage Current (V) (A) Planar 14.5 0.611 1.269 0.786 RIE 16.48 0.617 1.434 0.781 chemical 16.96 0.619 1.452 0.792 Grating structures for novel applications
LOW VOLUME, LOW COST MANUFACTURING APPROACH PRINCIPAL PROCESSES and EQUIPMENT Gratings Edge Isolation System � LabVIEW Interface � Coin stack Wafer Arrangement � Etching Gas from Sidewalls � 6”-diameter wafer capability Grating structures for novel applications
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