Lead free metallisation paste for crystalline silicon solar cells: from model to results

This work reports successful development of thick film lead free metallisation paste for contacting crystalline silicon solar cells. Models have been set-up to understand and describe the process of contact formation and current transport of front side metallisation pastes to silicon. New experimental test procedures have been developed to assess the models and minimize the number of experimental tests. The goal is to find in an intelligent way a replacement for the lead in the glass frit. Using the outcome of this new contact model silver pastes with lead free glass frits have been formulated and tested using the new approaches. Cells were produced of Cz mono crystalline silicon material, with a 45 Ohm/square emitter and SiN_x antireflection coating. Using the best lead free silver front side pastes an efficiency of 16.6% was reached. This is equal to results from leaded reference pastes, and the best result published so far.