In the production of mc Si solar cells, the contamination by O, C and N from the SiO2 crucible and coating during solidification is insufficiently understood: the reported diffusion coefficients in Si and SiO2 disagree and the system is heterogeneous as it consist of different phases over a wide temperature range.

I try to determine the process parameters by local impurity measurements down to ppb level in ingot and crucible, model the system based on the findings and assess possibilities to reduce impurity levels through variations in the system.

To do that I produce several ingots with coating and crucible of varying purity. The chemical analysis is performed with GDMS, FTIR and other techniques. The electrical properties of Si are determined by lifetime and dislocation density measurements. Modelling is based on COMSOL Multiphysics.

By that, I aim to develop cost efficient improvements to the solidification process that lead to profitable mc Si solar cells with increased efficiency.