Observation of metal precipitates at prebreakdown sites in multicrystalline silicon solar cells

The local prebreakdown behavior of a damage etched multicrystalline silicon solar cell produced from virgin grade feedstock was characterized. At the position of micrometer-scaled prebreakdown sites, which correlate with recombination active defects found along grain boundaries, micro-x-ray fluorescence mappings revealed the presence of Fe precipitate colonies. These measurements represent direct evidence that transition metal clusters lead to decreased breakdown voltage and cause soft diode breakdown. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3272682]