U.S. PVMC Report: 3 rd Annual c-si PVMC Workshop U.S. PVMC Report 3 rd Annual c-si PVMC Workshop San Francisco, CA

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1 U.S. PVMC Report: 3 rd Annual c-si PVMC Workshop U.S. PVMC Report 3 rd Annual c-si PVMC Workshop San Francisco, CA H.P. Seigneur, J. Walters, A.C. Rudack, W.V. Schoenfeld, P. Brooker July 8 th, 2014

2 U.S. PVMC Report: 3 rd Annual c-si PVMC Workshop Summary Summary On July 8 th, 2014 the c-si programs at the U.S. Photovoltaic Manufacturing Consortium (U.S. PVMC) held our 3 rd Annual c-si Workshop in San Francisco, CA during the Intersolar NA conference. The general purpose of this workshop was to increase our current collective understanding of anticipated critical needs/challenges of diamond wire sawing for the photovoltaic industry. The scope of the workshop included diamond wire sawing of silicon, diamond wire saws, diamond wire manufacturing, in-line metrology for inspection of diamond wire, diamond wire failure mode analyses, wafer as-cut properties, diamond wire sawing cost reduction, and other diamond wire related topics. This 3 rd annual c-si PVMC Workshop was very successful. Participants from both industrial and academic backgrounds, came together to share and discuss a variety topics related to the feedstock and wafer supply chain. The participants represented diamond wire manufacturer, coolant manufacturer, diamond wire saw manufacturer, metrology manufacturer, solar cell manufacturer, and academic research centers.), Many stimulating thoughts were conveyed and thought provoking questions discussed in relation to diamond wire sawing for PV. As one of the key products of this workshop was an extensive list of near- and long-term challenges for the mutual benefit of the participants and the c-si PVMC programs. The PVMC will use this valuable input when moving forward in the conception of new collaborative projects within the c-si Programs. Panel Discussion B. Sopori W. Schoenfeld A. Gupta Breakfast

3 U.S. PVMC Report: 3 rd Annual c-si PVMC Workshop Participants First Name Last Name Affiliation Brent Ames Applied Materials Tony Barnfield Thermocoax Inc Bhushan Sopori NREL Marcie Black Bandgap Engineering Albert Bluemle Marker Systems Mark Bommeli Meyer Burger AG Frederic Bouisset Thermocoax Inc Anthony Broomer Process Research Wei Che Saint-Gobain Abrasives Cynthia Christensen Cornwell Group Chris Eberspacher Independent Carrie Feeney process research.com Patrick Frei GTI Technologies Pierre Girodet Thermocoax SAS Atul Gupta Suniva Jeff Harte Silfine Juris Kalejs American Capital Energy David Krick CH2Mhill Alman Law DAETEC, LLC Teresa Linenfelser Marker Sysyems Dermin Lyuu Grace Zhenyong Co., LTD. Shreyes Melkote Georgia Institute of Technology Abraham Michelen HVCC Daniel Montag Nines PV Bang Nguyen MEMC Sergei Ostapenko Ultrasonic Technologies Maslina Othman First Solar Karen Pauls Independent Stephen Preece Process Research Thomas Puthanangady Saint-Gobain - Performance Plastics Andy Rudack PVMC Winston Schoenfeld US PVMC Hubert Seigneur PVMC Joe Walters PVMC Frederic Dross Hanwha Solar Jim Landowski JL Consulting Karen Pauls Independent

4 U.S. PVMC Report: 3 rd Annual c-si PVMC Workshop Summary Workshop Agenda 1 3 nd Annual c-si PVMC Workshop: Diamond Wire Sawing for PV 7:30a 8:30a Registration/Breakfast 8:30a 8:35a Welcome Dr Hubert Seigneur, c-si U.S.PVMC 8:35a 8:40a Opening Remarks Dr Winston Schoenfeld, c-si U.S.PVMC 8:40a 9:00a 2014 International Technology Roadmap for PV (ITRPV) Stephan Raithel, SEMI 9:00a 9:20a Recent Advances in Understanding of Diamond Wire Sawing of Silicon Dr Shreyes Melkote, Georgia Institute of Technology 9:20a 9:40a Novel non-destructive inspection metrology for diamond wire Dr Sergei Ostapenko, Ultrasonic Technologies 9:40a 10:00a Characterizing surface damage introduced by diamond wire sawing Dr Bhushan Sopori, NREL 10:00a 10:20a Diamond wire failure modes and wear mechanisms Dr Paul Brooker, Florida Solar Energy Center 10:20a 10:40a Coffee Break/Networking 10:40a 11:00a Diamond wire wafering can enable the adoption of high efficiency cells Dr Antoine Manens, Applied Materials 11:00a 11:20a Impact of incoming wafer surface on solar cell manufacturing Dr Atul Gupta, Suniva 11:20a 11:40a Small Batch Silicon Wafering Dr Steve Preece, Process Research Products 11:40a 12:00p Current Status and Challenges for Fixed Diamond Sawing Thomas.K. Puthanangady, Saint-Gobain 12:00p 12:30p Panel Discussion 12:30p 1:30p Lunch/Networking 1To download the rd Annual c-si PVMC Workshop materials, refer to the following link:

5 U.S. PVMC Report: 3 rd Annual c-si PVMC Workshop Summary of Challenges Speakers and attendees shared their perspective on current and future challenges for the diamond wire sawing in PV manufacturing and provided input on potential barriers for its widespread adoption. Both technical and market-related topics were debated by the workshop participants. This section summarizes both near-term and long-term challenges. Near-Term Challenges (1-3 Years) 1-3 Years Challenges Conversion from slurry slicing to DW. Stimulating new equipoment investment vs. equipment upgrades. Large coolant tanks/pumps of slurry saws not suitable for diamond wire saws Enabling diamond wire sawing for multi, sawing process tuning, brick prep, Texturization process is a barrier Improved fundamental understanding of diamond wire sawing process (E.g. Process tribology: abrasive-material interaction, Role of crystallographic properties on cutting characteristics, surface/subsurface damage) In-line metrology for diamond wire monitoring Lower the striation amplitude to < 5 mm Improve uniformity for thinner wafers Better texture uniformity Diamond adhesion and fracture Reducing wire failure during cutting Cost of saws and wires A robust 80um diamond wire for mono-si slicing CapEx for DW dedicated tools Continue to drive down the wire consumption Availability of cost effective n-type wafers Optimize saw control for higher throughput, minimum wire damager, tight tension control, lower TTV Consistent incoming wafer surface morphology to the PV cell manufacturer Standardized surface cleaning post sawing Development of more effective, cheaper, non-hazardous, non-corrosive coolants Developing high speed wire saws Long-Term Challenges (4+ Years) 4+ Years Challenges Accelerating the adoption of advanced architecture using thin wafer format Increasing market share of mono Wire and process optimization (Abrasive/wire properties, Process dynamics, Residual stress, Predictive models) Higher throughput Better cutting uniformity within the wafer and wafer to wafer Longer lasting thinner wires Thinner wires/cores for reduced kerf Alternate fixed abrasives (i.e. beyond diamond) Process optimization to maintain high yield and low defectivity (e.g. microcracks) Cell design optimization for thin wafer Hardware improvement to reduce breakage in the cell fabrication line Breakthrough module technology Kerf losses down to 60um Adoption of thin wafers by cell/module makers No wire breakage Precise tension control Balance Kerf loss vs productivity vs CoC Better steel to allow high tension Optimized diamond size and density to allow higher cutting speed Enable wafer thickness down to 140um Enabling < 3um Silicon loss (damage removal +Texturing), smaller diamond particles? Increase coolant lifetime, reduce environmental impact, ensure functionality at lower concentrations Patterned Diamond Wire for better cut quality, higher throughput Next generation diamond for super long wire life

6 U.S. PVMC Report: 3 rd Annual c-si PVMC Workshop Summary Summary and Conclusions The 3 rd Annual c-si Workshop held on July 8 th, 2014 was deemed a success by the attendees. The many different points of view shared during the conference confirmed the need for addressing the challenges in a comprehensive and collaborative manner. It was clear from the resulting list of short and long term challenges the interdependency of the challenges is best suited for resolution through a requires a collaborative methodology. The c-si PVMC programs is committed to continue providing an open environment that enables direct cooperative interaction of its member companies for the development of c-si technologies to new frontiers, diamond wire sawing technologies included.