Innovative Approaches to Low-Cost Module Manufacturing of String Ribbon Si PV Modules; Final Subcontract Report, March 2002 - January 2005

As a result of this work, Evergreen Solar, Inc., is now poised to take String Ribbon technology to new heights. In the ribbon growth area, Project Gemini-the growth of dual ribbons from a single crucible-has reached or exceeded all the manufacturing goals set for it. This project grew from an R&D concept to a production pilot phase and finally to a full production phase, all within the span ofthis subcontract. A major aspect of the overall effort was the introduction of controls and instrumentation as in-line diagnostic tools. In the ribbon production area, the result has been a 12% increase in yields, a 10% increase in machine uptime, and the flattest ribbon ever grown at Evergreen. In the cell area, advances in process development and robotic handling of Gemini wafers havecontributed, along with the advances in crystal growth, to a yield improvement of 6%. Particularly noteworthy in the cell area was the refinement of the no-etch process whereby the as-grown ribbon surface could be controlled sufficiently to allow this process to succeed as well as it has. This process obviates any need for wet chemistry or etching between ribbon growth and diffusion.