French researchers have investigated heterojunction photo voltaic module reliability in damp warmth environments and located that sodium ions are the principle supply of degradation.
A bunch of researchers from the French analysis heart Institut Photovoltaïque d’Ile-de-France (IPVF) and EDF R&D, a unit of the French vitality large EDF, carried out a sequence of checks to test the reliability of heterojunction (HJT) photo voltaic panels in a damp warmth surroundings and recognized sodium ions as the principle reason for degradation.
“Our examine exhibits that sodium ions induce a deterioration of cell passivation, particularly within the entrance half,” the lead writer of the analysis, Lucie Peirot-Berson, mentioned. pv journal. “We additionally be certain that the use Sodium-free glass considerably reduces module degradation.”
To examine “Failure modes of silicon heterojunction photovoltaic modules in damp warmth surroundings: Sodium and moisture results,” revealed in Solar Energy Materials and Solar CellsThe researchers defined that they investigated six HJT module cowl configurations, every of which relies on 160 μm-thick M2 n-type wafers and half-cut cells linked by pairs of ribbons and pads of electrically conductive adhesive (ECA).
All modules are wrapped in thermoplastic polyolefin, which scientists say has a excessive water absorption coefficient. “This materials was chosen to enhance the migration of moisture and ions and to raised emphasize the mechanisms of decay,” they emphasize.
The six module cowl architectures are: soda-lime glass-glass; low sodium glass; sodium-free glass; frontsheet-backsheet; glass-backsheet; and frontsheet-glass. Opaque aluminized backsheets and clear movies are used as frontsheets or backsheets within the proposed configurations.
In whole, 17 bifacial modules and one monofacial panel have been produced in a 3S laminator at 160 C. They have been then transferred to an ESPEC DH85 chamber with normal growing older parameters of 85 C and 85% relative humidity (RH). A Spire 5600 SPL flasher was used to measure module degradation and photoluminescence (PL) and electroluminescence (EL) pictures have been used to research the IV curves.
“For EL, carriers are created by injecting present into the module. In this case, a darkish space can correspond to various kinds of degradation. It will be from resistive losses that restrict the gi- injected present or it turns into depassivated areas that favor non-radiative recombinations as a substitute of radiative ones,” defined the lecturers. “For PL, the carriers are generated by publicity to mild because of the photovoltaic impact. In this case, a darkish zone solely corresponds to a low passivity high quality.
The checks present that the modules with the soda-lime glass-glass configuration undergo the very best open-circuit voltage and short-circuit present losses, because of the depassivation of the cell by the motion of sodium ions originating in glass leaching.
The evaluation additionally exhibits that the motion of sOdium ions in inducing cell passivation degradation are stronger within the anterior half, whereas the mThe oisture has been discovered to induce degradation of the clear conducting oxide (TCO) and contacts and lead to a lack of fill issue.
“The examine exhibits a larger sensitivity to sodium-induced degradation of the cell entrance facet in comparison with the again facet, with vital front-top recombination seen within the entrance facet,” Peirot-Person mentioned. “This distinction will be defined by the character of the amorphous silicon layer and the morphology of the TCO layers as already proven within the earlier literature.”
Looking forward, it’s mentioned that their findings ought to be verified by testing different HJT module architectures.
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