Benefits of different process routes for industrial direct front side plating

In this work, we highlight the benefits of alternative plating routes compared to the standard plating route primarily discussed in literature and currently introduced in pilot production [1, 2]. The common plating route starts with the laser ablation of the front side grid after rear side Al-printing and firing. Then, an HF dip removes the native oxide for the subsequent light induced nickel-, copper plating (LIP) with a silver capping as a finishing. Afterwards, an annealing step improves the adhesion of the plated grid and its contact resistance. Here, we want to show the advantage of three alternative process routes. In the first alternative route, the laser opening of the front side grid is performed before the firing step. During firing, the laser damage is partly cured and can lead to an increase in open circuit voltage (Voc) of 7 mV on state of the art industrial PERC solar cells. For the second process route, the removal of the native oxide is eliminated. To ac hieve this, special laser and plating conditions are needed. Finally, for the third alternative process route, the annealing of the plated stack can be combined with a stabilization process suppressing the light induced degradation (LID). The presented alternative routes give new degrees of freedom for process optimizations regarding precursor-induced features such as high laser damage on shallow emitters, parasitic plating (PP) for passivation layers with high pinhole density or LID.