Application of SunsPL for fast laser chemical process development

Selective emitters will soon become a standard feature of industrial silicon solar cells. RENA offers a laser chemical process (LCP) to locally ablate the antireflection coating and form a highly doped emitter at the opened area. The front side metallization is then applied by light induced plating (LIP) of nickel and silver. However, it is still a challenge to optimize this process sequence for precursors coming from different production lines. For this purpose we use photoluminescence imaging (PL) as a valuable tool to reduce the impact of the quality spreading of the precursors on the evaluation of our experiments. With PL it is possible to calculate an implied open circuit voltage or dark saturation current as well as a pseudo fill factor before metallization. Instead of comparing different groups of an experiment only by their final cell parameters, we compare the quality parameters obtained with PL after each process step. Like this we can exactly quantify the impact of each production step on the final solar cell performance. In this paper we will demonstrate how using PL improves the significance of our experiments and allows fast process optimization with a small amount of wafers. In general this procedure for process control can also be applied for other process steps.