Lamination-interface-dependent deacetylation of ethylene vinyl acetate encapsulant in crystalline Si photovoltaic modules evaluated by positron annihilation lifetime spectroscopy

Hagihara, Hideaki; Sato, Hiroaki; Hara, Yukiko; Jonai, Sachiko; Masuda, Atsushi

doi:10.7567/jjap.57.082301

Cited by 5 publications

(6 citation statements)

References 35 publications

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“…During the DH test, water penetrated the module and generated corrosion around the ribbons. This phenomenon is generally due to the hydrolysis of EVA which creates acetic acid in the module, as reported in the studies of Bauermann et al [9], Owen-Bellini et al [11], Masuda et al [7] and Hagihara et al [3].…”

Section: Visual Inspection and Observationsmentioning

confidence: 78%

“…Within this generation, the a-Si PV cells represented a minor part of the market share with 0.05% in 2019. However, this solar cell technology, remaining widely used for specific small-scale applications, holds some real advantages: better resistance to hightemperature environments, good performance with artificial light conditions (as a consequence of its high absorption coefficient and spectral range) and improved durability in the case of prolonged exposure to sunlight [2,3], the reason why we decided to focus this study on the long-term performance of amorphous PV cells.…”

Section: Introductionmentioning

confidence: 99%

“…Hagihara et al [3] explored the chemical mechanisms of PV degradation under accelerated DH test followed by UV test and under outdoor exposure in Japan for about 20 years. The formation of acetic acid (deacetylation reaction) by the hydrolysis of the EVA was accelerated during the DH test, especially after 3000 h. Deacetylation could also be induced by the photodegradation of the EVA under UV illumination.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of the degradation of amorphous silicon mini-modules under a severe sequential UV/DH test

Vincent,

Posa,

Khouzam

et al. 2023

EPJ Photovolt.

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This study presents the results of severe accelerated tests carried out on four encapsulated amorphous silicon (a-Si) mini-modules. All the a-Si mini-modules were exposed to a 85 °C and 85% relative humidity damp heat (DH) prolonged treatment for 5000 h representing five times the duration specified by the IEC 61215 standard for qualification tests. For two of the four mini-modules, the DH test was preceded by a severe UV preconditioning, by applying 30 times the dose of 15 kWh/m2 at a temperature of 50 °C as prescribed by the IEC 61215 standard, in order to enhance the degradation during the following DH test and to reduce the overall testing time. I–V curves were plotted with a time step of 100 h under standard test conditions (STC) using a class A solar simulator and a source meter in order to monitor the degradation throughout both the tests. A visual inspection with photographic capturing was also performed at each stage to detect the apparent defects. Corrosion observed after 2000 h owing to the ingress of humidity is explained here by two possible infiltration paths in the layers of the mini-modules. Delamination occurred after 5000 h for the PV mini-modules which underwent the extended DH test. After 5000 h of damp heat testing, the degradation of the maximal power (Pmax) was found to be slightly accelerated for the a-Si mini-modules that were previously exposed to a severe UV preconditioning, with a value reaching 80% of its initial value, whereas, for the others only subjected to the prolonged DH test, the maximal power remained above 80% of its initial value. In all cases, the mini-modules seemed highly reliable with no failure after 5000 h of accelerated testing, and, based on an equivalent time of 20 years for 1000 h of accelerated test, they would exhibit a limited degradation rate of 0.2%/year in outdoor field conditions.

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Section: Visual Inspection and Observationsmentioning

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Analysis of the degradation of amorphous silicon mini-modules under a severe sequential UV/DH test

Vincent,

Posa,

Khouzam

et al. 2023

EPJ Photovolt.

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“…Ethylene vinyl acetate (EVA) is used as encapsulant in crystalline Si photovoltaic modules. EVA deacetylation negatively influences the performance of the latter and to clarify the degradation mechanism, a PALS investigation was undertaken [ 105 ]. Using an energy-tunable slow positron pulse beam, it was possible to assess that deacetylation (involving a reduction in size of the free volume holes) mainly occurs at the interface between EVA and the other components.…”

Section: Discussion Of Some Pals Results In Polymeric Systemsmentioning

confidence: 99%

Probing the Free Volume in Polymers by Means of Positron Annihilation Lifetime Spectroscopy

Consolati

Nichetti²,

Quasso

2023

Polymers

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Positron annihilation lifetime spectroscopy (PALS) is a valuable technique to investigate defects in solids, such as vacancy clusters and grain boundaries in metals and alloys, as well as lattice imperfections in semiconductors. Positron spectroscopy is able to reveal the size, structure and concentration of vacancies with a sensitivity of 10−7. In the field of porous and amorphous systems, PALS can probe cavities in the range from a few tenths up to several tens of nm. In the case of polymers, PALS is one of the few techniques able to give information on the holes forming the free volume. This quantity, which cannot be measured with macroscopic techniques, is correlated to important mechanical, thermal, and transport properties of polymers. It can be deduced theoretically by applying suitable equations of state derived by cell models, and PALS supplies a quantitative measure of the free volume by probing the corresponding sub-nanometric holes. The system used is positronium (Ps), an unstable atom formed by a positron and an electron, whose lifetime can be related to the typical size of the holes. When analyzed in terms of continuous lifetimes, the positron annihilation spectrum allows one to gain insight into the distribution of the free volume holes, an almost unique feature of this technique. The present paper is an overview of PALS, addressed in particular to readers not familiar with this technique, with emphasis on the experimental aspects. After a general introduction on free volume, positronium, and the experimental apparatus needed to acquire the corresponding lifetime, some of the recent results obtained by various groups will be shown, highlighting the connections between the free volume as probed by PALS and structural properties of the investigated materials.

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“…The positron source was sandwiched between two pieces of water‐absorbed samples during the PALS measurements. The PALS was conducted with a digital oscilloscope system at room temperature 13,14 . To measure the saturated water absorption state of the samples, PALS was performed by covering the samples and the positron source with a polyethylene bag containing water.…”

Section: Methodsmentioning

confidence: 99%

Amorphous polyamide m‐xylylenediamine‐adipic acid‐isophthalic acid copolymer (MXD6I): Evaluation of oxygen barrier property and free volume in high humidity condition

Yamanaka

Muraya

Oda

et al. 2022

Polymers for Advanced Techs

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To get insights into the excellent gas-barrier properties of amorphous polyamide m-xylylenediamine-adipic acid-isophthalic acid copolymer (MXD6I), free-volume hole size and thermophysical properties of MXD6I were evaluated. The results from positron annihilation lifetime spectroscopy (PALS) showed that the free-volume hole size of MXD6I-which was estimated from the ortho-positronium (o-Ps) lifetime and o-Ps intensity-remained almost unchanged even with a high water-absorption rate. This indicates that no significant structural changes occurred in MXD6I. In contrast, the free-volume hole size of the semicrystalline polyamide MXD6 significantly increased due to water absorption. The glass transition temperature (T g ) of MXD6I decreased due to water absorption, but it remained higher than the ambient temperature. The molecular motion of MXD6I is likely to be limited even under high humidity conditions; therefore, nanoscale structural changes such as crystallization are unlikely. We found that the stable gas-barrier properties of MXD6I can be attributed to its amorphous nature and a high T g even in a water-saturated state.amorphous polyamides, gas barrier polymers, gas barrier property, PALS measurement | INTRODUCTIONPlastics are widely used in food packaging because they are lighter than metal and glass containers, and have excellent processability. 1,2 In particular, gas barrier polymers-such as poly(m-xylene adipamide) (MXD6)-are often used to reduce food loss and maintain a high quality of food and beverages. 3-5 MXD6 shows high mechanical properties, optimal thermophysical properties for co-extrusion or coinjection processes, and excellent gas barrier properties. [5][6][7] The oxygen transmission rate (OTR) of MXD6 at 23 C and 60% relative humidity (RH) is less than one-tenth that of polyamide 6 (PA6) (MXD6: 4 cc•mil/(m 2 •atm•d), PA6: 50 cc•mil/(m 2 •atm•d)) 5 ; this makes MXD6 a widely used material for high barrier packages. However, the oxygen barrier property of MXD6 decreases under high humidity 5,7 ; OTR of MXD6 at 23 C/90% RH increases to 13 cc•mil/ (m 2 •atm•d), which is approximately three times higher than that under the 23 C/60% RH condition. 5 Deterioration of the oxygen barrier property under high humidity conditions significantly reduces preservability during shipping and in high-humidity regions such as Southeast Asia. We developed a high-performance amorphous polyamide (PA), m-xylylenediamine-adipic acid-isophthalic acid copolymer (MXD6I). It is an isophthalic acid copolymerized MXD6. MXD6I shows excellent gas barrier properties similar to those of MXD6, and its gas barrier properties do not change in a high-humidity environment. The reason MXD6I-an amorphous PA with the m-xylylenediamine (MXDA)

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Lamination-interface-dependent deacetylation of ethylene vinyl acetate encapsulant in crystalline Si photovoltaic modules evaluated by positron annihilation lifetime spectroscopy

Cited by 5 publications

References 35 publications

Analysis of the degradation of amorphous silicon mini-modules under a severe sequential UV/DH test

Analysis of the degradation of amorphous silicon mini-modules under a severe sequential UV/DH test

Probing the Free Volume in Polymers by Means of Positron Annihilation Lifetime Spectroscopy

Amorphous polyamide m‐xylylenediamine‐adipic acid‐isophthalic acid copolymer (MXD6I): Evaluation of oxygen barrier property and free volume in high humidity condition

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