Effects on Metallization of n⁺-Poly-Si Layer for N-Type Tunnel Oxide Passivated Contact Solar Cells

Thin polysilicon (poly-Si)-based passivating contacts can reduce parasitic absorption and the cost of n-TOPCon solar cells. Herein, n⁺-poly-Si layers with thicknesses of 30~100 nm were fabricated by low-pressure chemical vapor deposition (LPCVD) to create passivating contacts. We investigated the effect of n⁺-poly-Si layer thickness on the microstructure of the metallization contact formation, passivation, and electronic performance of n-TOPCon solar cells. The thickness of the poly-Si layer significantly affected the passivation of metallization-induced recombination under the metal contact (J_0,) and the contact resistivity (ρ) of the cells. However, it had a minimal impact on the short-circuit current density (J), which was primarily associated with corroded silver (Ag) at depths of the n⁺-poly-Si layer exceeding 40 nm. We introduced a thin n⁺-poly-Si layer with a thickness of 70 nm and a surface concentration of 5 × 10²⁰ atoms/cm³. This layer can meet the requirements for low J_0, and ρ values, leading to an increase in conversion efficiency of 25.65%. This optimized process of depositing a phosphorus-doped poly-Si layer can be commercially applied in photovoltaics to reduce processing times and lower costs.