Light Induced Degradation and Regeneration of High Efficiency Cz PERC Cells with Varying Base Resistivity

In this work we investigate the light induced degradation (LID) of industrial high efficiency PERC cells which are fabricated from p-type Cz silicon with a base resistivity ranging from 0.8 Ω cm to 3.4 Ω cm. The change of all electrical cell parameters after illumination is investigated. The total efficiency decrease after illumination is mainly driven by the FF decrease. This is due to an increased bulk recombination contribution after degradation compared to the front and rear surface recombination and also to the injection dependent excess carrier lifetime. Additionally, the so called regeneration procedure which transforms the boron-oxygen defects responsible for LID into a less active state is employed in order to reduce the degradation. The possibility of regeneration can be a very important factor when choosing the base resistivity with the highest efficiency potential for PERC cells.