Electricity from photovoltaic solar cells: Flat-Plate Solar Array Project final report. Volume V: Process development

The Flat-Plate Solar Array (FSA) Project, funded by the U.S. Government and managed by the Jet Propulsion Laboratory, was formed in 1975 to develop the module/array technology needed to attain widespread terrestrial use of photovoltaics by 1985. To accomplish this, the FSA Project established and managed an Industry, University, and Federal Government Team to perform the needed research and development. The goal of the Process Development Area, as part of the FSA Project, was to develop and demonstrate solar cell fabrication and module assembly process technologies required to meet the cost, lifetime, production capacity, and performance goals of the FSA Project. Early in the Assessment Phase, it became apparent that available processes were incapable of meeting the cost goals of the Project. Also, neither the 20-year (later increased to 30-year) reliability goal nor the effects of processing on reliability had ever been assessed. This document is a summary of the FSA-sponsored research and development efforts expended by Government, Industry, and Universities in developing processes capable of meeting the Project's goals during volume production conditions. The cost goals allocated for processing were demonstrated by small volume quantities that were extrapolated by cost analyses to large-volume production. Program redirection precluded planned large-volume demonstrations and, in the final phase of the Project, efforts were directed toward research-oriented processing to produce high-efficiency cells. High-efficiency crystalline silicon solar cells are continuing to evolve in research laboratories. When efficiency increases resulting from these new cell designs level off, there is a need to develop high-volume, low-cost processes that will retain these efficiency improvements and capture the economic benefits. To provide proper focus and coverage of the Process Development effort, four separate technology sections are discussed in this document: surface preparation, junction formation, metallization, and module assembly