Poly-Si Removal for TOPCon Solar Cells: A Comprehensive Comparison of Different Approaches and their Cost-Effectiveness

This work gives a deeper insight in wet chemical removal of phosphorous-doped poly-silicon via both the batch cluster route with utilization of an organic additive as well as the route with inline removal and batch post-cleaning for manufacturing TOPCon solar cells. The first part of this work focuses on the features of the batch cluster additive for poly-Si removal regarding glass protection and etch rate increase. In the second part an analysis concerning batch cluster vs. inline poly-Si removal process will be given followed by an optimization of the post-clean process for the batch cluster route. A detailed study is done in the case of ex-situ n-doped layers with single slot LPCVD configuration where there is a complete parasitic deposition on the front side. A sufficient poly-Si removal is a key factor in order to get a low Jrev,2 which prevents damage to the modules by excessive heat generation (e.g. hot-spots). Finally a cost-ofownership for different scenarios of the two poly-Si removal routes will be presented.