CORRELATIONS BETWEEN FINGER GEOMETRY AND DISPENSING PASTE RHEOLOGY

摘要

An optimum adjustment of printing medium and machine parameters is essential to establishdispensing as an alternative front side metallization process for silicon solar cells. In previous studies [1-3], pasterheology was found to have a major impact on resulting finger geometry and process stability. In order to find a goodbalance between printability and resulting contact geometry, different dispensing pastes were evaluated anddispensed on Cz–Si 156x156 mm2 precursor material equipped with standard aluminium printed back surfaces andpre-printed front side busbars. In order to determine the optimum co-firing temperature, three completely screenprintedcell groups were processed in parallel serving as reference cells. Cell results were investigated concerningfinger geometry and electrical parameters. With increasing paste elasticity, the finger width could be reduced down to43 μm. Furthermore, contact width indicating possible paste spreading on the wafer surface as well as finger neckingturned out to be a crucial geometrical parameter of dispensed contact fingers. Once more, the enormous potential ofdispensing as a front side metallization technique could be demonstrated.