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, metal} ) and the contact resistivity ( ρ _c ) of the cells. However, it had a minimal impact on the short-circuit current density ( J _sc ), 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 × 10 ²⁰ atoms/cm ³ . This layer can meet the requirements for low J _{0, metal} and ρ _c 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.