Multi-Scale Simulation of Mo-Ag Laminated Metal Matrix Composites with Mo-Ag Diffusion Layer and Parallel Gap Resistance Welding in Solar Cells

Abstract

To date, Mo/Ag laminated metal matrix composites (LMMCs) have been extensively applied as interconnectors for solar cell. To optimize the connection strength between Mo-Ag LMMCs and solar cells, a multi-scale simulation method (MSM) was adopted to simulate the parallel gap resistance welding (PGRW) process, including molecular dynamics (MD) simulation and finite element method (FEM). The structure of the Mo-Ag diffusion layer was observed using high-resolution transmission electron microscopy (HRTEM), revealing a thickness of approximately 5 nm and forming a wedge-shaped structure, enhancing the bonding between Mo and Ag. The properties of the Mo-Ag diffusion layer were calculated using MD, which significantly impacts the properties of the interconnectors. These parameters were input into the FEM model, and nine sets of orthogonal simulation experiments were designed. The results showed that under conditions of an applied voltage of 0.5 V, 1/2 electrode distance of 0.15 mm, and electrode pressure of 8.89 N, the interface temperature at the workpiece connection can reach 940 ℃, while the internal stress does not exceed the yield strength of the material. Additionally, according to the parameters of nine sets of orthogonal experiments, the interconnectors were welded to the solar cells, and tensile tests were conducted on the obtained joints. The results showed that under the optimal parameters obtained by simulation, the connection strength can reach a maximum value of 558 gf. Meanwhile, the results of electron backscatter diffraction (EBSD) demonstrated that the connection mechanism of PGRW mainly involves mutual diffusion and recrystallization under electrode pressure and resistance heat.

Keywords: Parallel-gap resistance welding (PGRW), multiscale simulation method, Mo-Ag diffusion layer, molecular dynamics (MD), Finite element method (FEM), Orthogonal experimental design