l'Actualité du Solaire

A degradation alert was launched in 2016 with PERC technology. It proved to be particularly sensitive to light-induced degradation (LID) and light-induced degradation and high temperature (LeTID). Having knowledge of these degradations,

manufacturers have mitigated them so that PERC cells do not experience excessive LID and LeTID rates.

In mid-2023, researchers began to warn that TOPCon panels could be more sensitive to certain degradation mechanisms. Damp heat tests were carried out. It was found that the front metallisation of negatively doped 'N-type' TOPCon cells appeared to be more susceptible to degradation.It was found that the front metallisation of negatively doped TOPCon 'N-type' cells appeared to be more susceptible to acid or moisture induced degradation than their positively doped 'P-type' counterparts.

Secondly, it was noted that N-type TOPCon cells may be more sensitive to ultraviolet-induced degradation (UVID). These technological problems associated with new products are not unique to the solar industry.

It should be remembered that not all the steps involved in qualifying and optimising production parameters have been completed.

The photovoltaic industry continues to face enormous pressure on prices and costs, so manufacturers still have to think about how they nomenclature their panels. Sometimes they have to choose high-quality products, and sometimes they use ingredients that are of lesser quality but have no effect on the product.

The researchers' warnings focus on three areas:

1. TOPCon panels are more sensitive to water vapour than PERC panels. Some manufacturers attribute this greater sensitivity to corrosion of the finely porous "glass frit" in the panels. TÜV Rheinland Shanghai, however, does not believe this: "Water vapour penetration is prevented by the encapsulation and, to a much lesser extent, by the cellular technology".
2. Are TOPCon panels more susceptible to UV degradation? Yes, they are. The degradation is attributed to [problems with] surface passivation, which deteriorates after exposure to UV light. To compensate for this, manufacturers need to pay particular attention to the right choice of encapsulant. "The front glass and the encapsulant act as UV filters for the solar cells. The UV filtering capacity of the encapsulant diminishes over time as the panel is exposed to UV rays on a permanent basis. A thicker, more UV-resistant encapsulant must be chosen.
3. PI Berlin claims that TOPCon panels are more sensitive to potential-induced degradation polarisation (PID-p). This is a phenomenon known to experts. Roof-mounted installations, where the rear side does not receive sufficient UV irradiation, make the panels concerned more susceptible to severe power losses due to PID-p.

https://www.pv-magazine.com/2023/09/16/weekend-read-getting-to-the-bottom-of-topcon-degradation/

PV Magazine of 16 September 2023