The Application of Novel Platinum-Reinforced Tin-Silver-Copper Solder to Bifacial Photovoltaic Module for Improvement of Yield and Reliability

Abstract

The characteristics of solder joints between the busbars of solar cells and copper ribbons can affect the performance of a photovoltaic (PV) module significantly. The resistivity of the joints and the intermetallic compound structures within the joints are the two main characteristics that impose a substantial impact on the yield and the reliability of the PV module. In this paper, we aim to present and analyze a novel platinum-reinforced tin-silver-copper (Sn-3.8Ag-0.7Cu-0.2Pt) as the lead-free solder material to connect copper ribbons to the metallization of bifacial solar cells. The performance of the PV module using platinum-reinforced solder is investigated by constructing two bifacial PV modules using the popular lead-free Sn-3.8Ag-0.7Cu solder and Sn-3.8Ag-0.7Cu-0.2Pt solder, respectively. Micrographs of the joints are obtained to show that the platinum-reinforced solder joint has fewer voids and a more evenly distributed and thinner intermetallic layer than that of a conventional SnAgCu solder joint. As a result, the physical attachment between the busbars and the ribbon using SnAgCuPt solder is stronger than that using SnAgCu solder. The power outputs of both PV modules are measured together with two commercial PV modules under the sun using an IV plotter. The results show that the total energy yield of the bifacial PV module with the new solder is about 6–10% higher than that with the conventional SnAgCu solder. The energy yield of the bifacial PV module using SnAgCuPt solder is 35.8% and 0.2% higher than that of the commercially available monofacial polycrystalline and monocrystalline PV modules, respectively.