Cast Polycrystalline Silicon Photovoltaic Module Manufacturing Technology Improvements: Final Subcontract Report, 8 December 1993 - 30 April 1998

This report summarizes work performed by Solarex, A Business Unit of Amoco/Enron Solar, under this subcontract. Among the accomplishments during the program are the following: a) Converting all of the production casting stations to increase ingot size, operating them at equivalent yields and cell efficiencies, and thus doubling the casting capacity at a 20% lower cost than the cost of newequipment; b) Developing a wire-saw process and transferring the process to production; as a result, more than 80% of wafering is now done using wire saws, at higher yields and lower costs than achieved on the internal diameter saws; c) Developing an aluminum paste back-surface field (BSF) process to increase cell efficiency by 5%; researchers also designed, procured, and transferred tomanufacturing a fully automated printing system to produce the BSF cells;; d) Fabricating 15.2-cm by 15.2-cm polycrystalline silicon solar cells and building modules using these cells; e) Modifying the module assembly area to increase capacity by a factor of three; f) Implementing a single-layer Tedlar backsheet that reduced backsheet cost by $0.50/ft2; g) Selecting, testing, and qualifying alow-cost (< $1.00 per module) electrical termination system; h) Qualifying the structure and adhesive system for mounting frameless modules and using the system to build several large arrays.