The Project "Rock-Star": The Evolution of Rotary Printing for Solar Cell Metallization

Within this work, we provide a comprehensive overview about research activities and current status with respect to rotary printed metallization for silicon solar cells. We will present the major results of the research project "Rock-Star" and previous activities which focused on the metallization of Si solar cells using flexographic printing and rotary screen printing. We demonstrate that the rear side metallization of passivated emitter and rear cells (PERC) can be realized with rotary screen printing on the same quality level as state-of-the-art flatbed screen printing. Furthermore, it is shown that both rotary screen printing and flexographic printing are able to realize the fine line front side metallization. Fine line front side contacts down to approx. 40 mu m for rotary screen printing and around 30 mu m for flexographic printing are demonstrated. However, further optimization is required to reduce finger width, increase finger height and thus decrease the mean lateral finger resistance. A major result of project "Rock-Star" is the development of an innovative demonstrator platform to enable rotary printed solar cell metallization with high printing speed and low cycle time per wafer. Newly developed transport, alignment and printing concept enables a cycle time of down to 0.45 s/wafer. The concept and features of the demonstrator machine are presented within this paper.