Solar modules with TOPCon technology are known to offer higher efficiencies than the industry workhorse PERC; however, these modules need to fare well on the reliability front for the eventual success of a solar PV system, according to Board Member of SOLYCO Solar AG, Dr Lars Podlowski.
In his keynote address during TaiyangNews Reliable PV Module Design Conference, Podlowski reflected on the accelerated efforts by the global solar PV manufacturing industry to shift towards n-type TOPCon solar cell technology.
He said there have been murmurs about reliability problems in TOPCon modules in the field, raising concerns among developers. According to Podlowski, concerns are mainly related to glass-backsheet version not being sturdy enough to withstand water vapor ingress, thus leading to overall degradation of the modules.
TOPCon has additional passivation layers and a metallization paste of silver and aluminum, and this is what differentiates it from PERC. Podlowski believes this is perhaps the root cause of degradation in TOPCon modules.
Since SOLYCO sources its modules from China for the European solar rooftop market, it has also been sourcing TOPCon modules since 2020 and already has a 160-kW commercial-scale TOPCon installation in Europe, operational since 2017.
SOLYCO said it tested 2 samples of commercially available TOPCon dual-glass and glass-backsheet modules each, with M10-108 half-cut (HC) TOPCon cells via PI Photovoltaik-Institut Berlin AG.
Sharing the test results, Podlowski said the DH reliability testing showed that the TOPCon dual-glass is conceptually reliable and almost the same as PERC. As for glass-backsheet TOPCon modules, the DH testing showed higher degradation than dual-glass modules.
Nonetheless, Podlowski stressed that it is possible to have a very good, very stable TOPCon glass-backsheet module with TOPCon cells.
He admitted that while dual-glass TOPCon modules are at par with PERC, glass-backsheet modules show a huge variation in product quality regarding DH stability. Further investigation of individual parameters revealed that the power degradation is mainly due to the losses in fill factor (FF), which can be routed to increase in series resistance, meaning the moisture ingression corroding the aluminum-silver contacts on the front side, with no dip in Voc, indicate that the passivation stack is intact.
Having said that, Podlowski emphasized that not every glass-backsheet module failed during the various tests, implying TOPCon as a technology is still compatible with the glass-backsheet configuration; however, special care needs to be taken when selecting the BOM.
Podlowski's complete presentation is available to watch on TaiyangNews' YouTube channel, along with other presentations during the conference. These can be accessed here.