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Keywords:

  • electrical properties;
  • grain boundaries;
  • nickel precipitates;
  • silicon

The effect of various forms of Ni contaminants on the electrical properties of a silicon grain-boundary (GB) formed by direct bonding technology has been investigated in this paper. It is found that compared to that of the clean GB, the density of interface states and their majority carrier capture cross-section for the as-contaminated GB is significantly increased, due to the interaction of Ni impurities with the interface defects. However, after Ni impurities precipitating at the GB by a post-annealing, the degrading effect of the Ni contamination on the GB electrical characteristics is reduced again. These results show the detrimental effect of a metal-contaminated GB on the electrical properties of multicrystalline silicon solar cells can be minimized by engineering the metal precipitate density and size distribution.