Nitrogen-Incorporated Silicon Dioxide Interlayer Enables Pinhole-Reduced and Robust TOPCon With a High Implied...

Area of Science:

• Materials Science
• Semiconductor Physics
• Renewable Energy

Background:

• Tunnel Oxide Passivated Contact (TOPCon) is crucial for high-efficiency crystalline silicon (c-Si) solar cells.
• Current TOPCon technology faces limitations due to the thermal fragility of the silicon dioxide (SiO_x) interface, leading to pinholes and reduced passivation performance.

Purpose of the Study:

• To develop a more robust and stable interface for TOPCon solar cells.
• To improve the passivation performance and reduce defect density in TOPCon structures.
• To enhance the overall efficiency and scalability of TOPCon solar cell technology.

Main Methods:

• In situ doping of nitrogen (N) into amorphous silicon via plasma-enhanced chemical vapor deposition (PECVD).
• Formation of a silicon oxynitride (SiO_xN_y) interlayer during annealing.
• First-principles calculations to analyze bonding strength and thermal stability.
• Finite element simulations to assess thermal expansion matching and stress distribution.

Main Results:

• The SiO_xN_y interlayer exhibits significantly enhanced bonding strength and superior thermal stability compared to SiO_x.
• SiO_xN_y demonstrates improved thermal expansion coefficient matching with c-Si and poly-Si, reducing stress concentration and pinhole density.
• Record passivation performance achieved with an implied open-circuit voltage of 760 mV and a recombination current density of 0.35 fA/cm².
• Experimental front-junction TOPCon cells showed a 0.2% efficiency improvement.

Conclusions:

• Nitrogen incorporation into the TOPCon structure creates a robust SiO_xN_y interlayer, overcoming the limitations of traditional SiO_x interfaces.
• This interface engineering strategy significantly enhances thermal stability, reduces defects, and boosts solar cell passivation performance.
• The developed method is simple, industry-compatible, and offers a scalable pathway for improving the efficiency of TOPCon and related solar cell technologies with minimal cost increase.