Dual-Oxide Barrier Enhances TOPCon Solar Cell Efficiency
New oxidation process improves solar cell performance by shifting phosphorus peaks for better conductivity.
1New Diffusion Barrier Strategy
Researchers at Nanchang Hangkong University developed a dual silicon oxide diffusion barrier strategy to enhance TOPCon solar cell efficiency. By combining post-plasma oxidation with tunnel oxide optimization, the team successfully controlled the depth distribution of electrically active phosphorus. This method addresses critical trade-offs between contact resistance and parasitic optical absorption in cells.
2Optimizing Phosphorus Depth Distribution
Conventional industrial processes often struggle with phosphorus accumulation at the polysilicon surface, which increases unwanted optical absorption. The team's post-plasma oxidation technique shifts the activated phosphorus peak from 20 nm to 50 nm deep. This precise depth adjustment aligns closely with silver paste burn-off depths during the screen-printing and co-firing stages.
3Mechanism of Dopant Deactivation
The process utilizes inward-diffusing oxygen to induce depth-selective dopant deactivation through the formation of electrically inactive phosphorus-oxygen complexes. Rather than physically moving phosphorus atoms, this chemical approach maintains high dopant activation levels. Extending the post-plasma oxidation duration to 100 seconds proved optimal for balancing passivation quality and electrical performance in tests.
4Industrial Scale Validation Results
Testing involved 966 mass-produced TOPCon cells measuring 210 by 182.3 mm. The optimized oxidation process resulted in an absolute efficiency gain of 0.07 percentage points, raising average conversion from 27.15% to 27.22%. This improvement was primarily driven by a higher fill factor and increased short-circuit current across the tested batch.
5Reduced Contact Resistivity Achieved
The researchers observed a significant decrease in contact resistivity, dropping from 1.54 mΩ cm² to 1.00 mΩ cm². While the exact contribution of the phosphorus peak shift remains complex to isolate, the reduction in parasitic absorption clearly improved the long-wavelength response. Minor degradation in open-circuit voltage was noted but offset by gains.
6Compatibility With Existing Lines
This modification is designed for implementation on existing plasma-enhanced chemical vapor deposition production lines. By adjusting oxidation durations and densifying the bottom tunnel oxide, manufacturers can adopt this method without major hardware overhauls. The study highlights a practical route for improving commercial solar cell performance using standard industrial fabrication equipment.
7Material Characterization and Analysis
The team utilized advanced techniques including secondary ion mass spectrometry and electrochemical capacitance-voltage profiling to map elemental distributions. X-ray diffraction and Raman spectroscopy confirmed that the polysilicon crystallinity remained largely unchanged despite the oxidation treatment. These insights provide a comprehensive understanding of how the dual-oxide barrier influences the cell's microstructure.
8Future Implications for Photovoltaics
Published in the journal Solar Energy, this study demonstrates that simple process modifications can yield measurable efficiency improvements in mass-produced photovoltaics. Future research will likely focus on isolating the individual contributions of structural changes versus optical effects. This work represents a step forward in refining high-efficiency TOPCon solar cell manufacturing technology.
Original article: pv magazine — Dual-Oxide Barrier Enhances TOPCon Solar Cell Efficiency