Impact of the homogeneous junction breakdown in IBC solar cells on the passivation quality of Al 2 O 3 and SiO 2 : degradation and regeneration behavior

Within the last years, many different approaches for the simplified fabrication of interdigitated back-contact (IBC) solar cells have been developed. Most of those concepts result in emitter and back-surface field (BSF) regions that are in direct contact to each other which leads to a controlled breakdown under reverse bias at the pn junction. In this work, the influence of the reverse breakdown on the passivation quality of AlO and SiO at the pn junction is investigated, not only shedding light on the degradation but also on the regeneration behavior of the cells. It was found that cells with AlO passivation on the back side degrade during reverse breakdown whereas sister cells with SiO passivation were rather unaffected. Consequently, the degradation seems to be related to the passivation layer. However, it is shown that the passivation can be regenerated even under normal operation condition. A possible explanation is the discharging of interface traps, which are getting recharged already at room temperature.