Synchrotron-based microanalysis of iron distribution after thermal processing and predictive modeling of resulting solar cell efficiency

Synchrotron-based X-ray fluorescence microscopy is applied to study the evolution of iron silicide precipitates during phosphorus diffusion gettering and low-temperature annealing. Heavily Fe-contaminated ingot border material contains FeSi2 precipitates after rapid in-line P-diffusion firing, suggesting kinetically limited gettering in these regions. An impurity-to-efficiency (I2E) gettering model is developed to explain the results. The model demonstrates the efficacy of high- and medium-temperature processing on reducing the interstitial iron population over a range of process parameters available to industry.