4. 1 PV Module Design, Manufacture, Performance and Reliability
Back Contact, Solar Cell Interconnection, Qualification and Testing
Summary / Abstract:
The metallization scheme of the back-junction back-contact “ZEBRA” cell, which is a configuration based on several metallization and insulation paste layouts, having all busbars located at rear side , require only process adaptation at already existing automated mass production interconnection equipment, as well as comprehensive qualification. By means of that, also based on previous research , two interconnection technologies were considered for investigation: soldering and gluing with electrically conductive adhesive for PV (ECA), whereby one is epoxy- and the other one acrylic-based, both with silver particle fillers. For these contacting media available industrial equipment was used, a teamtechnik TT2100 stringer for soldering process, with a new interdigitated back contact cell (IBC) process and a teamtechnik TT1600ECA stringer for gluing process, also with process adaptation for IBC cell type. Both these new processes implied trials and several characterization techniques for identification of capability and for optimization. For testing long-term reliability of the joints, a setup for investigation of interconnection susceptibility to ageing factors (UV, temperature cycling and damp heat) was defined for unprotected samples (strings) and for samples protected by encapsulation (laminated). A suitable testing tool for our approach was the peel force measurement, which is a direct measure for the quality of the joint. Main target was to identify the optimal characterization and features specific for an industrial ready process for the IBC “ZEBRA” cells.