A research group from France claims to have found a way to reduce the indium consumption in solar modules in heterojunction by 85 % while retaining good performance and sustainability levels. The scientists tested different cell designs and the use of different cover layers to protect the cell against moisture breakdown.
A group of researchers led by the French National Solar Energy Institute (Ines) – a division of the French alternative energies and Atomic Energy Commission (CEA) – has investigated the reliability of heterojunction (HJT) solar panels under the heat fluid (HD) and has determined that and has determined that The use of thin indium tinoxide (ITO layers) in combination with cover layer made from silicon nitride (sinX) Help good reliability levels.
“We used for our tests Different cell structures, with different ITO thicknesses and different cover layers, “said the corresponding author of the research, Lucie Pirot-Berson, said PV -Magazine. “The study was conducted on the module scale, not only on the cell scale, and Showed that reducing the ITO thickness accelerates the breakdown mechanisms that are induced by sodium and moisture. “
“The results showed that reducing indium consumption, which is needed for the HJT technology, can therefore be difficult,” she started to say. ‘Fortunately, some cover layers are made of sinX or silicon oxynitride (sioyNZ)) Provide protection against degradation induced by sodium and can be used in combination with ITO. “
The DH test is an accelerated test that test the reliability of modules under extreme humidity and heat. In its standard shape, the PV is placed in a controlled room with a temperature of 85 ° C and humidity of 85% for at least 1,000 hours.
The academics used cells based on N-type 160 μm thick M2 waffles for their experiment. They tested three different ITO layers with thicknesses of 15 Nm, 30 Nm and 100 Nm and different SIOX and sinX Dielectric cover layers that were added on top of the thin ITO layers. The TCO layers were dropped off via plasma-improved chemical vapor deposits (PECVD) equipment supplied by the Meyer Burger of Switzerland.
“After TCO deposition, screen prints were performed using a pattern with 6 bus bars,” the research group explained. “Slaglagen were then added by PECVD technology in certain configurations: SinX (100 Nm) or SIOX (100 Nm). The optimum thickness of the cover layers was calculated using the CROWM simulation software. After production, the cells were cut in two with an IR laser. Depending on the configuration, two or three strings of two half cells per batch were connected to electrically conductive glue (ECA). “
The cells were then encapsulated by thermoplastic polyolefine (TPO) in modules with both glass glass and glass backsheet configurations. The modules were laminated via a 3S laminator at 160 ° C with a lamination time of 18 m.
Under DH conditions, the glass glass modules turned out to be particularly susceptible to moisture breakdown to their edges, while for glass backsheet panels the main fluid turned out to be in the back. Moreover, the scientists discovered that in glass glass panels sodium ions are gradually released along the glass, on both sides, while in glass-backsheet modules are only released at the front.
“In general, the penetration of moisture is larger in glass backsheet modules than in modules with double glass due to penetration through the rear layer,” they emphasized. “This greater penetration of moisture results in more glass losing and degradation of moisture, as well as more degradation in glass-backsheet modules induced by sodium.”
In the meantime, the front covering layers proved to provide protection against breakdown by sodium and “drastically” reduces the short -circuit losses. “However, these cover layers can be broken down by the laser cutting process to the half -cell edges, which requires further optimization,” the group added. “Finally, these cover layers do not reduce the FF losses of the modules and even increase them. This still has to be investigated. “
Their findings are available in the study “Study and mitigation of moisture-induced demolition in SHJ modules by changing the cell structure“Published in Solar energy materials and solar cells. The research group also consisted of scientists from EDF R&D and EDF Renouvelables, both units of the French energy company EDF. “Finally, we offer a way to reduce Indium by 85% while maintaining the versions and sustainability of heterojunction modules,” they concluded.
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