Performance of silicon solar cells fabricated from multiple Czochralski ingots grown by using a single crucible
Results on the performance of solar cells fabricated on wafers from multiple silicon ingots of large diameter, grown by using a single crucible and a sequential melt replenishment Czochralski (CZO) technique are presented. Samples were analyzed for resistivity, dislocation density and impurity content. Solar cells were fabricated from the seed, center and tang end of each ingot to evaluate the growth reproducibility and material quality. The cell efficiency within a given wafer varies by no more than plus or minus 5% of the average value. A small but consistent decrease in the cell efficiency is observed from the first to the fourth ingot grown from a single crucible. This decrease may be related to an increase in impurity content or dislocation density or a combination of both. The efficiency of the cells fabricated from the tang end of the fourth ingot is about 10% lower than that of the control cell. An impurity effects model is employed to correlate this decrease in efficiency with the impurity build-up in the residual melt.