Rotary Screen Printed Metallization of Heterojunction Solar Cells: Toward High-Throughput Production with Very Low Silver Laydown

Within this work, first bifacial silicon heterojunction solar cells with rotary screen printed front and rear side metallization are demonstrated. The high-throughput metallization process is carried out on a newly developed innovative rotary printing demonstrator machine with high technology readiness level. A very short process cycle time of only 0.65 s per cell and a reduction of total silver laydown per cell by 60-70% compared to the flatbed screen printing reference process underlines the potential of this approach with respect to productivity and sustainability. Using a newly developed screen simulation approach, the performance of the utilized rotary screens for fine line metallization is analyzed and compared to flatbed screens. The printing results are profoundly analysed with respect to finger geometry and electrical performance (lateral finger resistance). With respect to the I-V-results of the fabricated heterojunction solar cells, the best group of fully rotary screen printed cells obtained a mean conversion efficiency of Eta = 21.7 % which is close to the flatbed screen printed reference group with Eta = 22.1 %. Using a hybrid approach with a rotary screen printed grid on the rear side and flatbed screen printed grid on the front side, a mean conversion efficiency of Eta = 22.0 % is obtained with a reduced silver laydown of approx. 50 %.