Module Process Optimization and Device Efficiency Improvement for Stable, Low-Cost, Large-Area, Cadmium Telluride-Based Photovoltaic Module Production: Final Subcontract Report, 1 July 1990 - 30 April 1994

This report describes work performed under a three-phase subcontract. The objectives of the program include (1) achievement of active-area efficiencies of greater than 14% on small cells; (2) achievement of aperture-area efficiencies of greater than 13% on 0.09-m2 (1 ft2) modules; (3) achievement of aperture-area efficiencies of greater than 1 2.5% on 0.37-m2 (4 ft2) modules; and (4) achievementof greater than 20-year module life (based on life testing extrapolations) with no greater than 10% efficiency degradation. The results obtained and described herein include the following: (1) efficiencies of 12.7% were achieved on small-area devices; (2) 0.09-m2 (1 ft2) modules achieved greater than 8% aperture-area efficiency, but work for further efficiency improvement was redirected towardthe 0.37-m2 (4 ft2) modules; (3) 0.37-m2 (4 ft2) modules achieved 26.5-W output, which calculates to 8.0% aperture-area efficiency; (4) consistent prototype production was focused on and substantially achieved within Phase 2; (5) life testing at the National Renewable Energy Laboratory showed no inherent stability problems with the CdTe technology, and the accuracy of module measurement wassatisfactorily resolved; and (6) a 'cradle-to-cradle' recycling program was begun based upon the philosophy that the establishment of such mechanisms will be required to ensure maximum recapture and recycling of all manufacturing waste materials and/or modules returned from the field.