Manufacturing Induced Bending Stresses: Glass-Glass vs. Glass-Backsheet

Slauch, Ian M.; Vishwakarma, Saurabh; Tracy, Jared; Gambogi, William J.; Meier, Rico; Rahman, Farhan; Hartley, James Yuan; Bertoni, Mariana I.

doi:10.1109/pvsc43889.2021.9518938

Cited by 6 publications

(11 citation statements)

References 21 publications

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“…These results are remarkably consistent with Xray topography and modeling showing higher maximum principal cell stress in glass-glass modules, with highest bending stress concentration in glass-glass modules near the end of ribbon on both ends of the cell. 9 Our results are also consistent with studies examining interconnect failure that shows higher mechanical loads on the solder interconnects leading to double the accumulated plastic strain in glass-glass modules compared with modules with polymeric substrates. 10 Analyzing our observations in the framework of these prior publications, it appears that the stress imparted by the thermal coefficient of expansion mismatch between cells and the copper ribbons led to the fracture of embrittled grid fingers near the ribbon-cell connections.…”

Section: Grid Finger Breakssupporting

confidence: 91%

“…Modules with polymeric backsheets also have encapsulant shrinking as temperature is reduced where the backsheet elastically deforms to accommodate the contraction moreso than glass substrates. 9 A previous study stress testing modules by damp heat also showed grid finger interrupts near the copper interconnect ribbon to a significantly greater extent in glass-glass modules compared with modules with polymeric backsheet. 11 Additionally, it has been suggested that the highest bending stresses in glass-glass modules exist when there is pinching at the module edges.…”

Section: Grid Finger Breaksmentioning

confidence: 85%

“…11 Additionally, it has been suggested that the highest bending stresses in glass-glass modules exist when there is pinching at the module edges. 9 Previously, Cording has shown that stresses may be higher at the edge of modules with glass-glass modules that can lead to glass breakage and delamination, especially when a support frame during lamination that prevents pinching at the edge is not used. 12 We used a support frame at the periphery of the laminate during the fabrication of the modules tested here to minimize such pinching; this resulted in a 0.05 to 0.06 mm thinning measured comparing the cell center to beyond the cell edge at the perimeter of the module, sampling 1 cm from the module edge.…”

Section: Grid Finger Breaksmentioning

confidence: 99%

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Evaluation of bifacial module technologies with combined‐accelerated stress testing

Hacke

Kumar

Terwilliger

et al. 2022

Progress in Photovoltaics

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In view of the increasing interest and market share of bifacial cells and modules, suitable substrates such as glass and transparent backsheets along with ethylene vinyl acetate (EVA) and polyolefin elastomer (POE) encapsulants were examined in combined‐accelerated stress testing (C‐AST) to evaluate and compare degradation modes. Testing with both monofacial and bifacial cells, we found that glass–glass modules with monofacial cells led to greater grid finger breakage than those with polymeric backsheets. This is attributed to previous X‐ray topography and modeling work showing higher stress in cells and interconnections in glass–glass modules than glass backsheet modules. Consistent with the objectives of C‐AST, which stresses modules at levels corresponding to the limits seen in the natural environment, we observed the UV‐fluorescence signatures of modules tested in C‐AST (considering the degradation associated with developing chromophores, moisture penetration, and photobleaching effects) to be like those in fielded modules, more so than other chamber stress testing implemented for comparison. We found light‐induced degradation (LID) in module types with regenerated (inactive) cells with C‐AST, suggesting the possibility of LID destabilization in some field conditions. We could also distinguish potential‐induced degradation (PID) on the back of the bifacial passivated emitter and rear cells (PERC) in C‐AST. Confirming with ex situ tests, we found polarization‐type PID most prevalent in glass‐glass modules with EVA as would be anticipated considering the greater leakage current through such module encapsulation. Unlike PID tests performed in the dark, which can lead to false positive PID test results, field‐representative illumination is experienced by the modules on the front and back sides while −1200 V system voltage is applied in C‐AST, supporting the conclusion that this module type with glass‐glass construction would be susceptible to PID in the field.

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Section: Grid Finger Breakssupporting

confidence: 91%

Section: Grid Finger Breaksmentioning

confidence: 85%

Section: Grid Finger Breaksmentioning

confidence: 99%

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Evaluation of bifacial module technologies with combined‐accelerated stress testing

Hacke

Kumar

Terwilliger

et al. 2022

Progress in Photovoltaics

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“…The debond energies after aging were higher than the delamination threshold of 200 J/m 2 found by Bosco et al, 33 which was developed for fielded G/B modules. In the case of G/G modules, the stresses acting upon the interfaces are expected to be somewhat higher, 8 , 34 requiring a greater interfacial debond energy to prevent delamination. Ultimately, these results represent only DH and DH/voltage conditions, so sequential accelerated test sequences involving mechanical stressors and thermal cycling are recommended to further characterize the risk of delamination in fielded G/G modules.…”

Section: Resultsmentioning

confidence: 99%

Chemical and mechanical interfacial degradation in bifacial glass/glass and glass/transparent backsheet photovoltaic modules

Spinella

Uličná

Sinha

et al. 2022

Progress in Photovoltaics

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Glass/glass (G/G) photovoltaic modules are quickly rising in popularity, but the durability of modern G/G packaging has not yet been established. In this work, we examine the interfacial degradation modes in G/G and glass/transparent backsheet modules under damp heat (DH) with and without system bias voltage, comparing emerging polyolefin elastomer (POE) and industry-standard poly(ethylene-co-vinyl acetate) (EVA) encapsulants. We investigate the transport of ionic species at cell/ encapsulant interfaces, demonstrating that POE limits both sodium and silver ion migration compared with EVA. Changes to the chemical structures of the encapsulants at the cell/encapsulant interfaces demonstrate that both POE and EVA are more susceptible to degradation in modules with a transparent backsheet than in the G/G configuration. Adhesion testing reveals that POE and EVA have comparable critical debond energies after the DH exposures regardless of system bias polarity. The results of this study indicate that the interfacial degradation mechanisms of G/G appear to be similar to those of conventional glass/backsheet modules. For emerging materials, our results demonstrate that POE offers advantages over EVA but that transparent backsheets may accelerate encapsulant degradation due to increased moisture ingress when compared with the G/G structure.

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“…The GT/POE module also displayed minor grid finger detachment or breakage in cells below the junction box. The failures in metal fingers might lead to increase in the series resistance (RS), and hotspots if the degradation becomes severe [6].…”

Section: ) Tc Extended (Tc600)mentioning

confidence: 99%

Extended Accelerated Stress Testing (EAST) of Glass/Glass, Glass/Backsheet and Glass/Transparent Backsheet PV Modules: Influence of EVA and POE Encapsulants

Kumar

Pavgi

Hacke

et al. 2022

2022 IEEE 49th Photovoltaics Specialists Conference (PVSC)

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Manufacturing Induced Bending Stresses: Glass-Glass vs. Glass-Backsheet

Cited by 6 publications

References 21 publications

Evaluation of bifacial module technologies with combined‐accelerated stress testing

Evaluation of bifacial module technologies with combined‐accelerated stress testing

Chemical and mechanical interfacial degradation in bifacial glass/glass and glass/transparent backsheet photovoltaic modules

Extended Accelerated Stress Testing (EAST) of Glass/Glass, Glass/Backsheet and Glass/Transparent Backsheet PV Modules: Influence of EVA and POE Encapsulants

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