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2004
Conference Paper
Titel
Metal content of multicrystalline silicon for solar cells and its impact on minority carrier diffusion length
Abstract
The metal content of three types of silicon material for cost-efficient solar cells, Astropower silicon-film sheet material, Baysix cast material, and EFG ribbon-grown multicrystalline silicon was determined using instrumental neutron activation analysis. Iron, nickel, and chromium were found in concentrations between 10(12) and 1.8x10(15) cm(-3), depending on the material. The concentration of cobalt, molybdenum, and copper was between 10(12) and 5x10(13) cm(-3). Since the minority carrier diffusion length in all three mc-Si materials was much higher than one would expect if all metals were dissolved in an interstitial or substitutional state, we concluded that the metals most likely formed clusters or precipitates with a lower recombination activity than the interstitial/substitutional metals. No significant difference was observed between the metal content of the high and low lifetime areas of each material.
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