UV degradation analysis of TOPCon cells

In the field of photovoltaics (PVs), tunnel oxide passivating contacts (TOPCon) cells have emerged as one of the mainstream cell structures adopted by PV module manufacturers, primarily due to their high photovoltaic conversion efficiency and excellent low-light performance. Ensuring the long-term reliability of TOPCon cells and modules is crucial, and the ultraviolet-light (UV) test serves as an essential method for assessing this reliability. By comparing the electrical performance parameters of TOPCon cells produced by a first-tier solar cell manufacturer before and after the UV test, it was observed that the electrical performance of both the front and rear sides degraded post-test. Notably, the rear side of the cell exhibited greater sensitivity to UV irradiation, with more pronounced degradation. When similar tests were conducted on cells with different passivation processes, UV degradation was still evident but varied in severity. This suggests that mass-produced TOPCon cells currently face issues with UV degradation, which can be mitigated by optimizing the thickness or refractive index distribution of the passivation layer. The UV resistance of the front side can be enhanced by adjusting the number of atomic layer deposition aluminum oxide cycles to modify the layer thickness and the structural composition of silicon nitride (SiNx). Similarly, the UV resistance of the rear side can be improved by optimizing the number, thickness, and refractive index of SiNx layers. These adjustments are essential for maintaining high double-sided power output in TOPCon cells.