Dutch scientists reported the next danger of degradation of n-type TOPCon cells with EVA encapsulant because of potential moisture degradation. Entrance-side metallization makes n-type cells weaker than p-type cells, in keeping with damp warmth checks.
Researchers on the Netherlands Group for Utilized Scientific Analysis (TNO) carried out a sequence of damp warmth checks to analyze the impact, when it comes to moisture degradation, of various encapsulation supplies on the efficiency lack of bifacial PV modules.
“The aim of this analysis is to seek out a proof for the degradation phenomena noticed in small samples of the bifacial module within the laboratory after the excessive damp warmth check,” the lead writer of the analysis, Paul Sommeling, talking. pv journal.
To review “Results of corrosion on bifacial crystalline silicon PV modules; interplay between metallization and encapsulation,” printed in Photo voltaic Vitality Supplies and Photo voltaic Cellsthe scientists made a comparability between three encapsulant supplies utilized in PV module manufacturing: ethylene vinyl acetate (EVA), polyolefin elastomers (POE) and thermoplastic polyolefins (TPO).
The analysis group says that it has noticed in earlier research that POE and TPO, not like EVA, don’t launch any acidic substances, which signifies that they might be higher than EVA in relation to acid-induced corrosion. Nevertheless, there may be nonetheless no confirmed proof that these supplies can lead to elevated stability of the sector module, because it takes a very long time earlier than vital subject degradation is noticed. .
Via damp warmth testing with a period of as much as 2,500 h, the teachers in contrast the efficiency of three supplies in glass-encapsulant-cell-encapsulant-glass-based laminates with out using edge sealant.
“Commercially out there n- or p-type bifacial cells (TOPCON and PERC respectively) have been used to make these laminates, which have been subsequently examined in a local weather chamber underneath humid warmth circumstances (85 C / 85% relative humidity),” they defined. “Present voltage (IV) and electroluminescence (EL) measurements have been made at 500 hour intervals to comply with the change in laminate traits over time.”
They used a method generally known as “coring” to carry out autopsy evaluation on all samples examined. For this, they used scanning electron microscopy (SEM) and Vitality-dispersive X-ray spectroscopy (EDX) to investigate the consequences of photo voltaic cell floor checks. All encapsulants are examined in keeping with IEC 61215 PV customary and past, with an extended check time.
Based on the analysis workforce, the check confirmed that hydrophobic and chemically inert TPO encapsulants present the best stage of safety in opposition to moisture-induced degradation in comparison with EVA and POE. It additionally reveals that the front-side metallization of the n-type TOPCon cells examined is extra inclined to acid- or moisture-induced degradation than their p-type counterparts.
“This front-side metallization of TOPCon cells deteriorates sooner than the again aspect metallization and in addition sooner than the metallization of PERC cells in EVA-based laminates,” the scientists emphasised. “We attribute the variations within the completely different compositions to the cell metallization used.”
They concluded that the principle reason behind the delamination of the metallic grid might be the degradation of the lead glass, which they mentioned is a part of the cell metallization grid and incorporates lead oxide (PbO).
“These outcomes are partly shocking,” Sommeling mentioned. “Corrosion results on PV are recognized and reported within the literature learning the consequences after subject publicity and after accelerated laboratory testing.”
He additionally defined that essentially the most severe corrosion issues are to a big extent associated to the discharge of acetic acid from EVA, essentially the most broadly used encapsulating materials in PV panels. Acid causes corrosion of cell metallization and/or tabbing materials or solder joints. At present, EVA is being changed by alternate options that don’t launch any acidic compounds and this helps to forestall many issues associated to corrosion.
“The unusual or ‘new’ features described in our paper keep in mind the very exceptional variations noticed between several types of metallization and completely different photo voltaic cells in relation to corrosion conduct, which might be correlated with completely different cell metallization compositions,” added Sommeling. “Additionally with out acids current, corrosion can nonetheless happen solely by means of the affect of moisture and in addition it varies broadly between the several types of metallization used.”
“It may be concluded that the precise mixture of n-type TOPCon photo voltaic cells studied in our paper together with EVA might be the next danger, in comparison with different mixtures of cell varieties and encapsulants,” Sommeling confirmed. “The usage of EVA together with comparatively excessive corrosion inclined metallization ought to and might be prevented. Then again, if the extra corrosion-resistant metallization sort recognized can be utilized in TOPCon photo voltaic cells, it should additionally assist to construct extra corrosion-resistant n-type PV panels.
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