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Impurities in polycrystalline silicon solar cells

Conference · · Conf. Rec. IEEE Photovoltaic Spec. Conf.; (United States)
OSTI ID:5490016
The effects of grain boundaries and impurities on silicon solar cell performance have been studied in single-crystal and polycrystalline ingots by intentionally incorporating 2 x 10/sup 12/ cm/sup -3/ molybdenum, 10/sup 14/ cm/sup -3/ titanium, and about 10/sup 15/ cm/sup -3/ chromium during Czochralski growth. Mo, Ti, and Cr degrade solar cell performance by inducing deep levels in silicon. Electrically active grain boundaries also reduce cell performance by inducing carrier recombination in the bulk as well as in the depletion region of the solar cell. At low impurity concentrations, polycrystalline cell performance is controlled by grain-boundary recombination, while at high concentrations, it is dominated by the impurity, resulting in equal efficiencies for single-crystal and polycrystalline cells. Impurity-grain-boundary interactions are species dependent and result in a decrease in impurity-induced deep-level concentration: Cr exhibits the largest interaction, Ti a weak interaction, and Mo no measureable effect.
Research Organization:
Westinghouse R and D Center, Pittsburgh, PA
OSTI ID:
5490016
Report Number(s):
CONF-820906-
Conference Information:
Journal Name: Conf. Rec. IEEE Photovoltaic Spec. Conf.; (United States)
Country of Publication:
United States
Language:
English