2D modeling of the iron concentration from crystallization to final firing of mc silicon solar cells

The behavior of iron in multicrystalline silicon during solar cell processing is analyzed by spatially resolved measurements and a 2-dimensional physical modeling. Previously used models for internal gettering in multicrystalline silicon, phosphorus diffusion gettering and aluminum gettering were improved and combined. The simulations for different iron contamination levels are in good consistency with the spatially resolved measurements of the Fei concentrations. The simulations can be used for optimization of the solar cell processes regarding to the iron distribution. The effect of a 550°C gettering step after phosphorus diffusion on the Fei concentration of the solar cell is simulated. For wafers intentionally contaminated with iron the Fei concentrations increase during contact firing above 860°C in the simulations and the experiments.