Progressive Development of n-poly-Si Contacts and Stencil Refinement for High-Efficiency p-TOPCon Solar Cells

Achieving high-efficiency p-TOPCon (Tunnel Oxide Passivated Contact) solar cells requires optimizing the metallization process and n-type polysilicon (n-poly-Si) passivating rear emitter contact. This study focuses on refining stencil height during screen printing to enhance the aspect ratio of metal contacts, thereby reducing shading and series resistance (R_s). Furthermore, the impact of varying gas ratio (GR) in phosphorus-doped n-poly-Si passivating contacts is investigated to improve the built-in potential (V_bi) and open-circuit voltage (V_oc). Although high surface passivation levels can lead to dopant diffusion into crystalline silicon (c-Si) during high-temperature annealing, potentially causing internal defects and increased recombination current density, they also contribute to enhanced cell performance. By systematically analyzing snap-off distances (the gap between stencil and cell) using commercially available pastes, an optimal distance of 1.4 mm was identified. This optimization facilitated finer line patterns, uniform contacts, and reduced Rs variability. As a result, the refined process significantly improved cell performance, achieving J_sc of 39.3 mA/cm², V_oc of 684.3 mV, FF of 81.01%, and Eff of 21.78%. Dark I–V analysis further demonstrated excellent contact quality, with a high shunt resistance (R_sh) of 298,315 Ω and minimal R_s of 0.43 Ω. The key contribution of this study is the systematic optimization of stencil printing parameters and passivating contact properties, leading to enhanced efficiency and reliability of p-TOPCon solar cells.