Rapid Thermal Annealing of p-Type Polysilicon Passivated Contacts Silicon Solar Cells

The carrier selective contacts Si solar cells based on tunnel oxide passivated contact (TOPCon) have provided an efficiency of over 25%, and the large-scale production is planned. One of the crucial steps in TOPCon solar cells fabrication is furnace annealing at around 875 °C. We have investigated the rapid thermal annealing (RTA) for TOPCon solar cells. We discovered that the RTA carried out in air showed much fewer hydrogen-induced blisters than in the N
₂
atmosphere. Second, the optical radiation and heat generated in RTA had a significant effect on the degradation of
iV
_oc
. The RTA with a SiN
_x
:H layer on top of polysilicon generated
iV
_oc
of 706 mV. The mechanism of degradation under air versus nitrogen atmosphere and the effect of high-intensity light during the annealing process were inferred through various characterizations, such as surface morphology, surface passivation, crystallinity determination, chemical compositional changes, electrical sheet resistances, and oxidation state of ultrathin SiO
_x
. The TOPCon after air RTA performed better than in nitrogen, optimally at 825 °C. Forming gas annealing further improved the
iV
_oc
. Crystallization and sheet resistance were dependent on the annealing temperature and time.