Investigating the degradation behaviours of n+-doped Poly-Si passivation layers: An outlook on long-term stability and accelerated recovery

Assessing the Stability of P+ and N+ Polysilicon Passivating Contacts with Various Capping Layers on P-Type Wafers

“…Interestingly, although the starting iV OC values were higher in n + poly than in p + poly samples, the improvements after firing were at par, with even less variability among the p-poly samples. These observations are in stark contradiction to our previous work [8], where we showed that firing at similar T F ranges as used in this work was detrimental to n-poly passivation on n-type c-Si. Kang et al also reported that firing at 700 • C led to a deterioration of surface passivation for both p-and n-poly on n-Si, with greater stability observed in p-poly samples [19].…”

“…Compared to n-type Si, passivating contact structures samples based on p-type Si show remarkable stability during LS. In previous work, we showed that the relative changes in J 0 at the point of maximum degradation during LS for n-type Si with n-poly contacts, compared to J 0 after firing, varied from 166% to 550% [8]. The reader is referred to this work for deeper understanding.…”

“…In LeTID, hydrogen released from a bulk hydrogen reservoir triggers a recombination-active complex [41]. In a separate work on n-type Si wafers, the degradation and complete recovery occurred after ~270 h [8]. The degradation and recovery observed in this study, and an onset of a tertiary degradation after over 365 days, raises serious concerns about the long-term stability of passivating contact structures on p-Si wafers and shows similarities with H-related degradation and recovery earlier referenced.…”

“…In that study, it was also observed that the rate of surface degradation was influenced by the temperature during light soaking (LS) and that the silicon nitride layer after firing was required for recovery of surface passivation [7]. Chen et al showed that in n-type Si, a higher LS temperature accelerated the degradation and recovery kinetics and reduced the extent of degradation and suggested that a complete degradation and recovery cycle was sufficient to mitigate the responsible defect [8].…”

Design considerations for the bottom cell in perovskite/silicon tandems: a terawatt scalability perspective

“…The n + doped TOPCon rear contact serves as an excellent passivating contact, with reported J 0s o 3 fA cm À2 and corresponding resistivities o3 mO cm 2 . 54,66,67 The surface passivation is controlled by the combination of chemical passivation of defects at the c-Si/SiO x interface, as well as field effect passivation provided by the heavily doped poly silicon layer.…”