Optimizing the Mechanical Adhesion Properties of Plated Contacts of i-TOPCon Solar Cells

In this study, we have investigated and optimized the laser-induced modification of the silicon surface to improve the mechanical adhesion of Ni/Cu/Ag-plated contacts on the rear side of i-TOPCon Si solar cells. We discuss different approaches to create the laser contact openings (LCO) for the fingers by varying the laser parameters and the geometry of the contact structure, targeting at an enhanced micro surface roughness at the Si/Ni interface. We evaluate the mechanical adhesion via tape tests and the effect on electrical degradation due to increased recombination via photoluminescence measurements. We demonstrate that a well-defined laser parameter set allows for improved adhesion while maintaining no significant loss in implied open-circuit voltage.