UNSW new research: The "invisible killer" of TOPCon solar cells

A new study led by the University of New South Wales (UNSW) suggests that a deeper understanding of the type of ultraviolet (UV)

radiation used to test solar cells could accelerate their long-term performance evaluation and improve their efficiency. The study focuses on TOPCon solar cells, which have become mainstream in the industry over the past two years, but whose durability has been a major concern.

Despite the widespread adoption of TOPCon technology, its durability under stressful conditions remains a key concern. In addition to the challenges posed by humid and high-temperature conditions, ultraviolet-induced degradation (UVID) has emerged as a new factor limiting the practical lifespan of TOPCon solar cells.

The researchers note that the increasing use of UV-transparent encapsulants in photovoltaic panels, while improving module efficiency, also increases solar cell exposure to UV radiation during operation, making UVID a growing concern.

Kiwa PVEL, a photovoltaic module quality inspection company, also found in its latest "Module Scorecard" report that TOPCon and other high-efficiency solar technologies are more susceptible to UVID than traditional technologies. This new research has two key findings: first, different parts of the UV spectrum affect TOPCon cells differently; second, new manufacturing methods designed to increase module power and efficiency may actually increase the risk of UV-induced degradation (UVID), which can impact the cells' long-term performance.

The research paper focused on UVB radiation, which has significantly higher photon energy than UVA, the more common UV radiation used in photovoltaic testing and closer to visible light.

The researchers note that UVB radiation has typically not been considered a major concern because most commercial encapsulants effectively block UVB radiation, leading to the assumption that UVB degradation does not pose a significant risk to installed modules.

However, as the industry continues to pursue higher module power, companies are exploring encapsulants with higher UV transmittance, making the impact of UVB radiation more important.

The study confirms that exposure to UVB radiation leads to increased surface recombination on the front side of TOPCon solar cells, ultimately reducing cell efficiency and accelerating degradation. The tests also reveal the complex relationship between hydrogen and UVID in TOPCon solar cells: UV radiation releases hydrogen within the solar cell, potentially leading to surface recombination and performance degradation. The research data shows that while both UVA and UVB photons affect the front of the cell, the higher-energy UVB photons break more Si-H bonds, leading to more pronounced degradation.

The paper notes that future TOPCon researchers need to focus on the effects of UV light, particularly UVB, on cells to ensure the technology's stable lifespan, thereby maximizing solar efficiency and the economic viability of power plants. The study also emphasizes that utilizing UVB light can enable faster and more efficient assessment of the long-term performance of solar cells.