Systematic characterization of multi-crystalline silicon String Ribbon wafer

The String Ribbon technology provides multi-crystalline silicon wafers for low cost and high efficiency solar cells (16% efficiency on untextured cells). This paper deals with the systematic characterization of standard String Ribbon wafer material produced by the Sovello AG. The investigations of the grain structure, the dislocation density (EPD), the minority carrier lifetime tau and the interstitial iron content Fe, show a clear correlation between lifetime, EPD, and interstitial iron concentration. High lifetime areas consist mainly of Sigma 3 twinned grains with low EPD and low interstitial iron content in the range of 4 x 10(11) atoms/cm(3). The dislocation and interstitial iron distribution is non-uniform over the ribbon width.