Conductive paste assisted interconnection for environmentally benign lead-free ribbons in c-Si PV modules

Crystalline Si (c-Si) photovoltaic (PV) modules with lead-free (LF) ribbons have drawn much attention for harvesting solar light using an environmentally friendly method. However, the high temperature required for processing the LF solder coated ribbons hinders their widespread use because of the increased thermomechanical stress. Hence, in this work, we proposed a versatile interconnection method employing low-temperature processable Sn57.6Bi0.4Ag-incorporated conductive paste (CP). By introducing CP to the PV module, the cells and LF ribbons can be assembled below 150 °C regardless of the solder coating of ribbon, diminishing the thermomechanical stress. Additionally, the introduction of CP makes it possible to connect c-Si PV cells using a pure copper strip without the solder. Analysis of the adhesion strength shows that the CP-assisted interconnection guarantees a strong mechanical bond (>2 N/mm) between the cell and the ribbon without increasing ohmic losses. In addition, the interconnection withstands thermomechanical stress and long-term exposure to humidity and high temperature. Therefore, CP assisted interconnection, as suggested in this work, should facilitate easier and smoother transition to LF ribbons in the PV industry.