Market-Driven EFG Modules: Annual Subcontract Report, 14 December 1995 - 13 December 1996

This report summarizes the accomplishments during the reporting period. The 'Task 1: Wafers' accomplishments include improvements in graphite purity in edge-defined film-fed growth (EFG) crystal-growth furnaces, improving wafer quality; optimization of EFG crystal growth rate; increased die run-length due to reductions in the use of carbon monoxide during EFG crystal growth; completion ofengineering and design work for EFG growth-furnace enclosures; feasibility demonstrated for the reduction of EFG wafer thickness from 300 m to 275 m; design and testing of a system to reduce costs of silicon feedstock sorting prior to EFG crystal growth; and testing of new carbon dioxide and copper vapor lasers for improved cutting of EFG wafers from octagon tubes. The 'Task 2: Cells'accomplishments include improvements in cell diffusion conditions resulting in increased cell efficiency; the completion of process design for a new approach to remove phosphorus glass from diffused wafers, reducing chemical consumption and hazardous waste by 95%; testing and evaluation of the use of textured coatings to improve cell efficiency; improvements in EFG cell efficiency byoptimization of metallization firing conditions; initiation of work on an optimized cell grid design; production of test samples of cells designed for interconnection on the rear side only; and demonstration of average efficiencies over 14.0% in more than 5000 EFG cells during one 2-week period. The 'Task 3: Modules' accomplishments include testing of new encapsulants promising reducedlamination time and improved yield; initial design work completed on new module frames that are both less expensive and faster to attach to modules; completion of initial testing and design work for lower-cost module diode housing; and concept developed for improved collection of light from area between cells in modules.