Industrial inline PVD metallization for silicon solar cells with laser fired contacts leading to 21.8% efficiency

In this contribution we present the latest results of our experiments in regard to an industrially feasible inline physical vapor deposition (PVD) metallization method for the rear side of passivated solar cells. In an earlier publication, the quality of such processed layers and the feasibility of the tool was already shown and compared with a commonly used laboratory process based on electron beam evaporation. Since then a difference in the Voc potential in the range of ~ 4 mV between both processes was observed on highly efficient cell devices. Ongoing experiments were then carried out to study the cause of this loss. First, it can be shown that the front side of the devices is not harmed in any way by the inline process. On the rear side, investigations regarding the impact of the lower aluminium purity and the higher process temperature in the case of the inline process were carried out. Finally, it is shown that an altered annealing process, which is likely to be necessary due to the different process temperature will exceed the voltage potential of the laboratory e-gun process, leading to very high efficiencies of 21.8 %.