Silicon web process development. Final report

Technical Report · Thu Oct 01 04:00:00 EDT 1981

DOI:https://doi.org/10.2172/5356735· OSTI ID:5356735

Duncan, C. S.; Seidensticker, R. G.; McHugh, J. P.; Skutch, M. E.; Driggers, J. M.; Hopkins, R. H.

During the past three and a half years of steady technical progress, the web process has evolved from one with potential advantages to a method very close to technology readiness for commercial development of low cost solar cells. Web output rates were raised more than ten fold to 27 cm/sup 2//min, and cell efficiencies were increased to 15.5% from abut 13%. Melt replenished growth, which was merely a concept in 1977, has now been demonstrated under operator control for a full one-day growth cycle, and for periods of one eight-hour shift with complete closed-loop control. The melt level was maintained constant to +-0.1 mm, a degree of control better than the estimated requirements for automated continuous growth of web. The web produced under continuous operation produced solar cells with excellent efficiency. Besides these systems-related developments, it has been shown that silicon web can routinely be grown with thicknesses below 150 ..mu..m to conserve silicon, and that the resultant ribbons have dislocation densities less than 10/sup 4/ cm/sup -2/. Silicon web has been grown from experimental low-cost silicon, as well as from purposely contaminated feedstock, and yet has produced efficient solar cells. Hence compatibility of the process with cheaper, less pure solar grade silicon seems likely. Collectively these achievements imply that the web process has an excellent chance to better the DOE/JPL 1986 goal for sheet plus polysilicon cost of 22.4 cents per peak watt (1980$). Projected web cost is in fact 17.3 cents per peak watt assuming area throughput rates of 25 cm/sup 2//min, 15% AMl cell efficiency, a three-day melt replenished growth cycle, system automation, and silicon at $14 per kg. Aside from a three-day growth cycle and the silicon cost, these objectives individually have been met.

• Research Organization: Westinghouse Research and Development Center, Pittsburgh, PA (USA)
• DOE Contract Number: NAS-7-100-954654
• OSTI ID: 5356735
• Report Number(s): DOE/JPL/954654-80/13; ON: DE82006083
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140501* -- Solar Energy Conversion-- Photovoltaic Conversion
AUTOMATION
COST
CRUCIBLES
CRYSTAL GROWTH
CRYSTAL GROWTH METHODS
DENDRITIC WEB GROWTH METHOD
DESIGN
DIAGRAMS
DIRECT ENERGY CONVERTERS
ECONOMICS
EFFICIENCY
ELEMENTS
EQUIPMENT
FURNACES
IMPURITIES
PERFORMANCE TESTING
PHOTOELECTRIC CELLS
PHOTOVOLTAIC CELLS
PRODUCTION
SEGREGATION
SEMIMETALS
SILICON
SILICON SOLAR CELLS
SOLAR CELLS
SOLAR EQUIPMENT
SPECIFICATIONS
TECHNOLOGY ASSESSMENT
TESTING