Industrialization of Ribbon Interconnection for Silicon Heterojunction Solar Cells with Electrically Conductive Adhesives
The use of electrically conductive adhesives (ECAs) and ribbons is a cost-efficient solution for the interconnection of silicon heterojunction (SHJ) solar cells already implemented in fully automated stringing equipment. A better understanding of the materials, the interconnection process and the reliability of the modules is still required. In this paper we present results of this interconnection approach focusing on material level, string production and performance analysis in outdoor operation. Firstly, the curing of ECAs is investigated. Furthermore, the volume and contact resistivity initially and after aging is characterized. ECAs in combination with Ag-coated and bare Cu ribbons are processed on an industrial glue stringer TT1600ECA from teamtechnik GmbH to manufacture SHJ solar cell strings. The uniformity of the cured bond line thickness is analyzed with optical microscopy. The bond line thickness is 32 to 38 µm on the sunny side. The peel force is characterized and the strings are further encapsulated in modules to test reliability and outdoor performance. The peel force ranges from 0.5 N mm−1 to 1.0 N mm−1 for certain ECAs. Adequate material combinations for PV modules showed degradation lower than 5% even in extended thermal cycle and damp heat testing. The outdoor test of SHJ modules over one year showed a 2% to 3.5% higher specific energy yield compared to a PERC reference module due to the absence of p-type related light induced degradation and a lower temperature coefficient of SHJ cells. With this work we contribute to the industrialization of ECA technology for SHJ cells by addressing relevant aspects of mass production.