Thermal Stability Improvement of Passivation Properties in Tunnel Oxide Passivated Contacts Toward High-Efficiency Silicon Solar Cells

Charge carrier selective contacts have been proposed as a promising strategy to enhance the performance of crystalline silicon solar cells. In this study, we investigate the post-annealing effect on passivation properties of phosphorus-doped polysilicon for tunneling oxide passivated contacts (TOPCon). The TOCon structures were prepared symmetrically on P-type wafers. The thermal oxidation process was employed to create a silicon oxide layer serving as a tunneling barrier. Subsequently, intrinsic poly-Si was deposited through the low-pressure chemical vapor deposition method, followed by ex-situ phosphorous doping using POCl₃. We found a significant decrease in passivation properties at lower temperatures (< 800°C) and a recovery at higher temperatures (≥ 800°C). Electrical properties and doping profiles show that active phosphorus ion profiles undergo distinctive active dopant modulation at the two different temperature regimes. Our results suggest that post-thermal treatment in the cell manufacturing process need to be managed to develop thermally stable highly efficient crystalline silicon solar cells.