From pv journal 10/24
Results from PV check laboratories in 2024 elevate issues about ultraviolet-induced deterioration (UVID) in some n-type TOPCon and HJT panels. The “PV Module Index Report” from the Renewable Energy Test Center (RETC) famous 40% of the examined modules confirmed at the very least a 5% loss in efficiency after UV testing.
The Kiwa PVEL lab, additionally in California, carried out UV testing at 120 kWh/m² publicity – designed to copy six months to 2 years within the subject, relying on location – and reported as much as 16.6% efficiency loss in some n-type TOPCon modules. The lab’s vice chairman of gross sales and advertising and marketing, Tristan Erion-Lorico, stated the 16.6% energy loss, primarily based on typical efficiency ensures that assure a most of 1% energy loss after a 12 months, and 0.4% thereafter, anticipated for a module that has been deployed for 40 years.
The check applications additionally discovered many modules to be stronger than UVID. Of these examined by RETC, 40% noticed lower than 2% energy loss, and almost half of the modules included in Kiwa PVEL’s PV Module Reliability Scorecard noticed lower than 3% energy loss. But these outcomes undoubtedly warrant a more in-depth have a look at the injury brought on by ultraviolet mild in PV modules, the mechanisms that trigger it, and the way it can greatest be averted.
UV testing
UV testing has lengthy been commonplace, and lack of efficiency resulting from browning of the encapsulant or tape used to carry the cells in place is a standard sight in older generations of PV modules. This downside is well solved by encapsulant suppliers.
With some modules experiencing UV-related issues after that, the testing focus shifted to what have been extra severe climate points, reminiscent of mild elements and potential degradation points. . The photo voltaic module requirements of the International Electrotechnical Commission (IEC) specify solely 15 kWh/m² of UV publicity, to eradicate the poorest performers.
UVID is again, nevertheless, with newer units made utilizing thinly deposited layers of a number of supplies that seem to make TOPCon and HJT modules simple to take away.
“The suggestions we have gotten from the analysis group means that for these extra delicate cell buildings, UV is a extra essential issue,” says Erion-Lorico. “It has been reintroduced to prolonged reliability assessments, together with PQP in Kiwa PVEL.”
Conducting accelerated assessments to precisely predict how UV mild will have an effect on PV modules over 30 years within the subject presents a big problem. Current assessments will be accelerated by an element of almost 5 – which means a full 12 months in a UV check chamber would characterize 5 years put in within the subject, in keeping with Erion’s estimates. – Lorico. “It’s tough to hurry up UV testing greater than we have achieved and nonetheless have outcomes which might be consultant of subject situations, not simply frying the module,” he defined.
Added complexity additionally comes from the very totally different ranges of UV publicity modules expertise, relying on the place they’re put in. Data from the Middle East Solar Industry Association reveals {that a} module put in in Dubai receives 5.4 instances the UV publicity of 1 put in in Berlin, for instance.
RETC Chief Executive Cherif Kedir stated, on a September pv journal webinar, that UV degradation is a cumulative impact and even when testing reveals {that a} module is prone to UV degradation, long-term commentary is required to point out progress over time.
“We try to do long-term UV exposures to see if [a PV module] continues to degrade 12 months after 12 months,” Kedir stated, including that one other discovering is whether or not even low ranges of UV degradation can set off different vulnerabilities or degradation mechanisms. “These are all points that the business would not learn about and there is lots of analysis occurring.”
Mechanism and mitigation
Archana Sinha, now a senior engineer at Kiwa PVEL, has been researching the results of UV on photo voltaic cells for a few years. “There are many mechanisms of degradation,” he stated pv journal. “Some are usually stronger than others and a few could also be partially reversible.”
The work of Sinha and different researchers revealed three essential mechanisms of degradation pushed by ultraviolet mild, that are associated to the intricacies of cell construction and module encapsulation. Sinha defined that susceptibility to UVID is expounded to the fabric and thickness of the assorted layers inside a photo voltaic cell. Thin layers and a few supplies reminiscent of silicon nitride, with a refractive index decrease than 2.29, present extra UV transparency.
This means they let in additional mild, and extra UV. Once inside a cell, short-wavelength UV photons have sufficient power to interrupt the chemical bond between silicon and hydrogen, damaging cell passivation and decreasing the effectivity of a tool. The high quality of a cell itself additionally performs a task. “If it has extra defect states current within the base layer, then it’s going to speed up the degradation,” Sinha stated.
When it involves decreasing the results of those mechanisms, there are three potential routes. The first two strategies are about stopping UV photons from reaching the cell, both via low UV transmission module glass or utilizing encapsulant supplies tailored to dam UV or “downshift” UV photons into the seen mild. A 3rd choice is to engineer the vulnerability out of the cell itself.
Chinese encapsulant provider Cybrid Technologies has developed a UV-mitigating encapsulant for HJT modules, a light-weight conversion movie (LCF) that it launched to the market in 2023 and known as Raybo. The movie creates a layer between the glass and module that absorbs UV photons and emits much less dangerous blue mild within the seen spectrum.
Module maker Huasun makes use of LCF in its newest HJT modules and notes the extra price concerned – which Cybrid estimates is round $0.50/m2 increased than a regular encapsulant – is basically offset by elevated conversion effectivity supplied. “At this time, we didn’t see the discount mechanisms on the mobile stage to have a big impact,” stated Christian Comes, director of European enterprise improvement at Huasun. “We proceed to analyze however LCF reveals lengthy life and wonderful discount of the results of UV on the cell. Therefore, for now, our essential technique is to make sure the reliability and sturdiness of UV injury .”
A Cybrid consultant stated the corporate can also be engaged on an LCF answer for TOPCon cells. The consultant stated it wanted a barely totally different encapsulant recipe as a result of TOPCon cells are extra delicate to corrosion, and famous that TOPCon prospects are usually extra price delicate.
Cell stage options
TOPCon producers appear to have extra alternative to handle the difficulty on the cell stage, and that’s additionally the tactic favored by module testing consultants. “I really feel extra snug with cells that do not present sensitivity,” stated Kedir of RETC. “Fixing issues on the root trigger is at all times higher and it is at all times cheaper, as a result of a movie provides to the associated fee.”
During the identical pv journal webinar, Trinasolar Product Manager Ling Zhuang famous that the corporate’s Vertex TOPCon modules noticed a efficiency lack of 1.44% on the entrance facet and 1.06% on the again facet after present process RETC’s UV testing protocol that exposes the module to UV mild of 220 kWh/m². In a further check licensed by the China General Certification Center, the modules have been uncovered to UV at 300 kWh/m² and noticed 1.64% electrical degradation on the entrance facet, and 1.26% on the again facet. Zhuang famous that after the UV check cycle, the module additionally handed the insulation and moist leakage assessments.
Zhuang places that sturdy efficiency all the way down to cautious course of design, management, and monitoring throughout cell manufacturing. He defined that Trina’s passivation construction ensures low self-absorption, holding UV photons away from the place they will do injury. It additionally makes use of cautious measurements to regulate the thickness of the passivation layer. Zhuang defined that whereas some producers calculate utilizing the typical movie thickness per cell, Trina makes the calculation primarily based on the thickness measured at a number of chosen factors in every cell, which ensures in higher equality. He added, cautious monitoring of cell processes is essential to identify potential manufacturing points earlier than they have an effect on a number of units. “We apply clever info administration … to observe all the course of and establish potential challenges,” Zhuang stated.
Industry consultants agree that though UVID will be managed within the manufacturing course of, not all photo voltaic producers take such a cautious strategy. “We have seen totally different check outcomes and it’s not in any respect the case that TOPCon is unreliable,” stated Erion-Lorico of Kiwa-PVEL. “But producers and their prospects want to concentrate on the chance right here.”
Road to restoration
The researchers noticed that when positioned beneath sure situations, photo voltaic cells can get better a few of the output misplaced by UVID. Further work on this may assist create an answer for modules which have already left the manufacturing unit.
“If we will develop restoration methods that assist mitigate issues, we’ll present that suggestions to upstream and downstream companions,” Sinha stated.
A 2024 examine by the German analysis institute Fraunhofer ISE reported some restoration from UVID after humidity freeze testing. Kiwa PVEL obtained a grant from the US Department of Energy’s DuraMAT Consortium for a two-year examine of UVID, together with studying extra about potential restoration mechanisms.
“I believe we will see some restoration mechanisms that you need to use within the subject however there are others the place the cell is broken and you may’t change what’s broken,” stated Erion-Lorico.
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