Influence of Multicrystalline Silicon Ingot Properties on the Fill Factor of PERC Solar Cells

The influence of multicrystalline silicon ingot properties on the final performance of mass produced PERC solar cells is an area of great interest in PV manufacturing. An ability to better understand this relationship can result in more rapid and targeted development of the ingot-growing process conditions. Likewise, a better understanding of the impact of input wafer material can lead to improved understanding and outcomes for the device manufacturing sequence. The present study uses a set of ingot level metrology data that is paired with final device performance data. This data set has been previously studied for relationships related to open circuit voltage and short circuit current. The present study completes the association with device efficiency by focusing on the relationships to the final fill factor of the device. The analysis shows that the wafer resistivity has a strong influence on the series resistance of the final device. The presence of defects within the device has a surprising influence on this relationship (which might be explained by systematic errors in the in-line measurements of the series resistance). A new method is developed for parameterizing the enhanced recombination in the device, and relationships to the ingot level lifetime data and the as-cut wafer defect level are demonstrated. The study concludes with a discussion on the implications of the results and the opportunity for further study.