Silicon materials task of the Low-Cost Solar Array Project: Phase IV. Effects of impurities and processing on silicon solar cells. Twenty-first quarterly report, October-December 1980

Technical Report · Fri Jan 30 04:00:00 EST 1981

DOI:https://doi.org/10.2172/6853649· OSTI ID:6853649

Hopkins, R H; Hanes, M H; Davis, J R; Rohatgi, A; Rai-Choudhury, P; Mollenkopf, H C

The overall objective of this program is to define the effects of impurities, various thermochemical processes, and any impurity-process interactions upon the performance of terrestrial solar cells. The results of the study form a basis for silicon producers, wafer manufacturers, and cell fabricators to develop appropriate cost-benefit relationships for the use of less pure, less costly solar grade silicon. Cr is highly mobile in silicon even at temperatures as low as 600/sup 0/C. Contrasting with earlier data for Mo, Ti, and V, Cr concentrations vary from place to place in polycrystalline silicon wafers and the electrically-active Cr concentration in the polysilicon is more than an order of magnitude smaller than would be projected from single crystal impurity data. We hypothesize that Cr diffuses during ingot cooldown after groth, preferentially segregates to grain boundaries and becomes electrically deactivated. Both Al and Au introduce deep levels when grown into silicon crystals. Accelerated aging data from Ni-contaminated silicon imply that no significant impurity-induced cell performance reduction should be expected over a twenty-year device lifetime. Combined electrical bias and thermal stressing of silicon solar cells containing Nb, Fe, Cu, Ti, Cr, and Ag, respectively produces no performance loss after 100 hour exposures up to 225/sup 0/C. Ti and V, but not Mo, can be gettered from polycrystalline silicon by POCl/sub 3/ or HCl at temperatures of 1000 and 1100/sup 0/C.

• Research Organization: Westinghouse Research and Development Center, Pittsburgh, PA (USA); Hemlock Semiconductor Corp., MI (USA)
• DOE Contract Number: NAS-7-100-954331
• OSTI ID: 6853649
• Report Number(s): DOE/JPL/954331-81/13
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140501* -- Solar Energy Conversion-- Photovoltaic Conversion
AGING
ALUMINIUM
CARBON
CHROMIUM
CRYSTAL GROWTH
CRYSTAL GROWTH METHODS
CRYSTAL STRUCTURE
CRYSTALS
CZOCHRALSKI METHOD
DATA
DIRECT ENERGY CONVERTERS
EFFICIENCY
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELEMENTS
EQUIPMENT
EXPERIMENTAL DATA
GETTERING
GOLD
GRAIN BOUNDARIES
GRAPHS
IMPURITIES
INFORMATION
ION MOBILITY
MANGANESE
METALS
MICROSTRUCTURE
MOBILITY
MONOCRYSTALS
NONMETALS
NUMERICAL DATA
OXYGEN
PARTICLE MOBILITY
PERFORMANCE
PHOTOELECTRIC CELLS
PHOTOVOLTAIC CELLS
PHYSICAL PROPERTIES
POLYCRYSTALS
PROCESSING
QUANTITY RATIO
QUANTUM EFFICIENCY
SILICON SOLAR CELLS
SOLAR CELLS
SOLAR EQUIPMENT
SPECTRAL RESPONSE
STRESSES
TABLES
TEMPERATURE EFFECTS
THERMAL STRESSES
TRANSITION ELEMENTS