Front surface crystalline silicon contacts formed via thick film silver pastes

In the coming years, the crystalline silicon solar cell industry will continue to decrease module costs through a variety of enhancements to productivity and cell efficiency. Of these, advances in processing and formulation of front and back side metallization pastes/inks have the potential to lead to significant cost reductions while at the same time maintaining or even increasing cell performance. Considering the front side silver-containing pastes, four methods have been outlined in the silicon PV technology roadmap as crucial to significant cost reduction: (1) a removal of heavy metal (Cd, Pb) containing glasses for environmental reasons; (2) a reduction in the use of, and eventual replacement of the precious metal silver as a conductive medium; (3) a reduction of finger width to reduce shading losses; and (4) reliable contact to shallow/high sheet resistivity emitters in order to reduce recombination losses [1]. As a current industrial supplier of high quality front side metallization pastes, Ferro Corporation will play a role in engineering and supplying pastes that address these four issues. Towards that end, here we review the microscopic structural and electrical mechanisms of front contact formation via metallization pastes/inks and report on initial attempts to further quantify the nature of the difficulties with reliably contacting high sheet resistivity wafers.