Effect of Lowering Curing Temperature of Electrically Conductive Adhesives on Ribbon Connected Solar Cells

Electrically conductive adhesives (ECAs) can be used for the interconnection of temperature-sensitive solar cells like perovskite-silicon tandem (PVST) due to their low processing temperatures. This study investigates the impact of lowering the ECA curing temperatures ≤ 140 °C on the volume resistivity, the cell interconnection quality, and the long-term stability under thermal cycles. With ECA interconnection, additional silver in the module is introduced. This work estimates the total silver consumption in PVST modules and explores possible routes for its reduction. Replacement of Ag interconnector coating with Sn is investigated in terms of long-term stability under damp heat and joint resistance. Variation of tested ECAs included products with 17, 60, 70 and > 70 wt% silver, to realize a detailed study of the silver content effect on volume resistivity, joint resistance, module performance and interconnection reliability. Silver consumption in PVST module was estimated to be 168 mg per M6 cell, corresponding to ~24 mg Ag/W. Joint resistance with tin was observed to be higher than with silver, corresponding to -0.2 %rel. PMPP loss attributed to series resistance in a PVST module. No increase in joint resistance with ECA interconnected tin coated ribbons after 3000 h in damp heat was observed. Volume resistivity as well as module performance after lamination was found to profit from higher ECA silver content. ECA processing temperature was found to influence the performance of the interconnection differently for each ECA. However, longer curing time resulted in higher fill factor and better long-term stability for all tested products.