A Custom High-Throughput Optical Mapping Instrument for Accelerated Stress Testing of PV Module Materials

Khan, Imran; Morse, Joshua; White, Robert R.; Miller, David C.

doi:10.1109/jphotov.2021.3122925

Cited by 5 publications

(14 citation statements)

References 16 publications

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“…R 2 was typically greater for YI, a more acute indicator of change in optical performance relative to its precision of measurement. 37,56 No curvature was observed for the data points relative to the fit in the inset of Figure 5, and an R 2 of 1.0 can be observed in 28 the difference is not statistically significant, and the specimen temperature is believed to be more accurately determined in this study, based on improvements in the coupons and the prevention of radiative heating of the thermocouple using a mask. The E a of τ rsw was slightly greater than that of YI in both studies, even though they are derived from the same measured spectra.…”

Section: Arrhenius Analysis and Activation Energymentioning

confidence: 63%

“…7 For sizes ≥7.5 cm, there is a darker band at the periphery of the discolored central region. 71 At 5 cm, the highest YI is observed. As seen in Figure 12, however, a size of at least 7.5 cm is needed to achieve maximum discoloration, suggesting that some mass transport of oxygen is still able to occur at the center of the discolored region of the 5-cm specimens, resulting in modest photobleaching.…”

Section: Evolution Of the Optical Performance Of Evas And Posmentioning

confidence: 92%

“…61 The λ cUV of the 7.5-, 10-, and 12.5-cm EVA-A specimens decreased in the decreased linearly with H, by only 8 nm at the end of the experiment. 61,71 Different excitation and emission fluorescence spectra were observed at the center of the discolored region of the final weathered 7.5-cm EVA-A and EVA-2 specimens relative to the 5-cm specimens of the same materials. 61 The results of the coupon size experiments confirm that a minimum size-5 cm for EVA-A in Figure 12 and 7.5 cm for EVA-2 in Morse et al 61 -is needed to enable a discolored region in the encapsulant coupons that is not limited by sample size and representative of the anaerobic region in front of cells in typical fielded modules.…”

Section: Evolution Of the Optical Performance Of Evas And Posmentioning

confidence: 99%

“…Changes in the performance of the remaining materials are more subtle, relative to the practical threshold of the measurement of 0.06% that was previously determined for this spectrophotometer. 37,56 The threshold of 5%, which is the pass/fail limit for Δτ h,rsw presently specified in IEC 62788-1-7, 12 is shown in Figure 2 (dashed line). As expected, EVA-A and 9PS exceed this limit in the ChT 85 C experiment.…”

Section: Specimen Characterizationmentioning

confidence: 99%

“…Crystalline content can reduce optical performance, whereas EVA can offer better front side transmittance. 37 The terminology "polyolefinic polymers" is generally more appropriate than "polyolefins" because the PV industry often uses at least some non-polyolefin-based monomers in small quantities (including small amounts of vinyl acetate). Polyvinyl butyral (PVB) has found use in buildingadapted and building-integrated PV, particularly in countries that require impact-resistant glass in architectural applications.…”

Section: Introductionmentioning

confidence: 99%

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Degradation in photovoltaic encapsulant transmittance: Results of the second PVQAT TG5 artificial weathering study

Morse

Thuis

Holsapple

et al. 2022

Progress in Photovoltaics

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The optical degradation of encapsulants from ultraviolet (UV) radiation has historically resulted in a significant loss in performance throughout the life of a photovoltaic (PV) module. International Electrotechnical Commission (IEC) test methods have recently been developed to screen for PV encapsulants prone to loss in optical performance. The present study was performed to benchmark polymeric packaging materials relative to IEC 62788‐1‐4 (covering the measurement of optical transmittance) and IEC 62788‐1‐7 (on the durability of transmittance), provide feedback toward improvement of the methods, and develop insight regarding optical degradation. Contemporary materials were examined, including poly(ethylene‐co‐vinyl acetate) (EVA), thermoplastic polyolefin (TPO), polyolefin elastomer (POE), and polyvinyl butyral (PVB) encapsulants; a poly(ethene‐co‐tetrafluoroethene)/poly(ethylene terephthalate) (ETFE/PET) transparent backsheet; and a polystyrene (PS) working reference material. The use of silica‐, specialty‐, and rolled‐glass was also compared in laminated coupons. Specimen size was separately examined from 2.5 to 12.5 cm. Weathering was performed with a xenon source, using IEC TS 62788‐7‐2 methods A2, A3, A4, and A5 (chamber temperature of 55°C, 65°C, 75°C, or 85°C), respectively. Characterizations were made using a UV–visible–near‐infrared (UV–VIS–NIR) spectrophotometer (transmittance and reflectance, with and without an integrating sphere), a UV–VIS fluorescence spectrophotometer, a camera, and an optical microscope. Performance was analyzed, including solar weighted transmittance, yellowness index, UV cut‐off wavelength, and haze (scattering). Separate Arrhenius analyses were performed to assess retention of transmittance and changes in yellowness index. The activation energy for both characteristics was found to range from 15–80 kJ·mol−1, with an average of 48 kJ·mol−1, similar to the average of 45 kJ·mol−1 identified in the previous international PV Quality Assurance Task Force (PVQAT) Task Group 5 (TG5) study of more traditional encapsulants. The separate degradation modes of discoloration and scattering were distinguished in the encapsulants using a comprehensive spectral characterization. Based on these results, the IEC 62788‐1‐7 pass/fail criteria of 5% change in transmittance was confirmed to identify a known bad encapsulant.

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Section: Arrhenius Analysis and Activation Energymentioning

confidence: 63%

Section: Evolution Of the Optical Performance Of Evas And Posmentioning

confidence: 92%

Section: Evolution Of the Optical Performance Of Evas And Posmentioning

confidence: 99%

Section: Specimen Characterizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Degradation in photovoltaic encapsulant transmittance: Results of the second PVQAT TG5 artificial weathering study

Morse

Thuis

Holsapple

et al. 2022

Progress in Photovoltaics

Self Cite

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Quantifying optical loss of high‐voltage degradation modes in photovoltaic modules using spectral analysis

Miller

Hurst

Sinha

et al. 2023

Progress in Photovoltaics

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The direct current bias for photovoltaic (PV) modules interconnected in series‐strings may include both high voltage negative (“HV−”) and positive (“HV+”) polarity with respect to the electrical ground. Multiple degradation modes, resulting in quantifiable optical loss, were found to occur during HV−/HV+ sequential stress, including corrosion of the external glass surface, encapsulant delamination (at its interfaces with the glass and the PV cell), internal haze formation (resulting from a chemical interaction between the glass and the encapsulant), corrosion and migration of the gridlines, and corrosion of the silicon nitride (SixNy) antireflective coating on the cell. The effects of these separate modes were examined using monolithic (e.g., glass or PV cell) and laminated‐coupon (glass/encapsulant/glass or glass/encapsulant/cell/encapsulant/backsheet) specimens. Characterizations during and after unbiased accelerated testing at 85°C/85% relative humidity included spectrophotometry, optical microscopy, electron microscopy, and ellipsometry. For some module components (i.e., the glass and the SixNy coating), the optical performance was determined through iterative analysis of empirical measurements. Concentrating on just their spectral effect, a novel model was then developed to estimate the transfer of light to the PV cell and the return of light from the PV module with simultaneous degradation mechanisms, which was compared with a mini‐module previously subjected to HV−/HV+ stress. The model suggests that one third of the current loss observed for the mini‐module can be attributed to the optical degradation of the packaging materials. The dominant degradation modes include encapsulant delamination and corrosion of the SixNy coating. Recommendations are given so that the optical model may be improved relative to accelerated testing and validated relative to field aging.

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PV encapsulant formulations and stress test conditions influence dominant degradation mechanisms

Uličná

Sinha

Miller

et al. 2023

Solar Energy Materials and Solar Cells

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A Custom High-Throughput Optical Mapping Instrument for Accelerated Stress Testing of PV Module Materials

Cited by 5 publications

References 16 publications

Degradation in photovoltaic encapsulant transmittance: Results of the second PVQAT TG5 artificial weathering study

Degradation in photovoltaic encapsulant transmittance: Results of the second PVQAT TG5 artificial weathering study

Quantifying optical loss of high‐voltage degradation modes in photovoltaic modules using spectral analysis

PV encapsulant formulations and stress test conditions influence dominant degradation mechanisms

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