Mathematical modeling of laser micro-welding for photovoltaic devices

Backside electrical contacts on photovoltaic (PV) devices can be generated using laser spot micro-welding. Moreover, diffractive optical elements can be incorporated into laser systems to simultaneously process multiple spot welds to increase manufacturing throughput. The implications of concurrently processing multiple spot welds have not been studied and correlated to laser processing parameters. Here, a mathematical model is used to study the heat transfer characteristics associated with selecting the optimal pitch distance required to simultaneously process spot welds while reducing the thermal interaction between them. Appropriate pitch distances for welds are identified for a range of laser processing parameters. Furthermore, the impact of varying spacing distance and processing parameters on degradation of the passivation layers due to thermal cycling is evaluated.