Bilayered Phosphorus-Doped Polysilicon Passivating Contact Structures for TOPCon Solar Cell Applications

The use of single-layer polysilicon (poly-Si) in tunnel oxide passivated contact (TOPCon) structures has demonstrated excellent passivation and contact performance. However, commercial TOPCon solar cell fabrication requires screen-printing and cofiring techniques for electrode preparation. The single-layer structure is less efficient at preventing metal atoms in the electrode paste from penetrating the silicon bulk. Furthermore, the uniformity of doping concentration and crystallinity within this structure poses challenges as it fails to optimally meet the intricate requirements for achieving superior performance in terms of passivation, contact, and mitigating parasitic absorption. In this study, the deposition process of the amorphous silicon (a-Si) precursor layer using an in-line magnetron sputtering system incorporated an additional plasma oxidation step, resulting in a bilayer poly-Si structure with the newly introduced SiO_x acting as a partition. Detailed investigations were conducted into the passivation quality, contact resistivity, crystallinity, and the distribution of critical atoms in the bilayer structure. Subsequently, the bilayer configuration was utilized in the manufacturing process of TOPCon solar cells. These efforts resulted in a notable enhancement in open-circuit voltage (V_oc) and short-circuit current (I_sc), leading to a 0.06% efficiency improvement, based on the average performance of ~200 cells per group.