Using a butt joint test to evaluate photovoltaic edge seal adhesion

Abstract

Many photovoltaic (PV) technologies have been found to be sensitive to moisture that diffuses into a PV package. Even with the use of impermeable frontsheets and backsheets, moisture can penetrate from the edges of a module. To limit this moisture ingress pathway from occurring, manufacturers often use a low permeability polyisobutylene (PIB)‐based edge seal filled with desiccant to further restrict moisture ingress. Moisture ingress studies have shown that these materials are capable of blocking moisture for the 25‐year life of a module; but to do so, they must remain well‐adhered and free of cracks. This work investigates the potential use of a butt joint test for evaluating the long‐term durability of adhesion by looking for significant changes in the failure mode or quantitative value of a butt joint test. A round robin experiment was conducted using six different materials and two sample constructions, with and without effort to control edge pinch. Tests were evaluated looking at the strength of the bond, and the type of failure observed in a round robin test involving five laboratories. It was found that both the measured values, and the observed failure modes were repeatable and reproducible within at 95% confidence interval.

Modeling of the effectiveness of novel edge seal designs for fast, low‐Cap‐Ex manufacturing

“…Because of this, the sparsely crosslinking, or uncrosslinked, PIBs used in PV applications will typically fail cohesively at very low values making them not useful to be relied upon for mechanical strength. 31,32 To overcome this concern, the silicone perimeter layer is used to provide mechanical integrity. Here, it should be noted that the shear forces on a glass/glass construction PV module are small enough that even when an EVA is formulated without a crosslinker and no frame is used, very little creep is observed.…”

“…Consequently, PIBs tend to experience a reduction in molecular weight as they age. Because of this, the sparsely crosslinking, or uncrosslinked, PIBs used in PV applications will typically fail cohesively at very low values making them not useful to be relied upon for mechanical strength 31,32 . To overcome this concern, the silicone perimeter layer is used to provide mechanical integrity.…”

Surface Modification of Backsheets Using Coupling Agents for Roll-To-Roll Processed Thin-Film Solar Photovoltaic (PV) Module Packaging Application

“…Manufacturing flexible thin-film photovoltaic (PV) modules at high-throughput yield, on a larger scale, and for roll-to-roll manufacturing process has been considered more appealing, − which makes solar electricity economically competitive with the conventional electricity generation. , Furthermore, perovskite solar cells (PSCs), which use organic–inorganic hybrid materials, have swiftly gained interest from many researchers and engineers in the PV community due to their promising properties and high energy conversion efficiencies as high as 25.2% and much higher theoretical efficiencies. , However, one of the main weaknesses of PSCs and other thin-film technologies is that they are particularly sensitive to water vapor and oxygen, which leads to the degradation and negatively impacts the performance and lifetime of the devices. − So far, delamination has been one of the highest failure modes experienced in fielded PV modules . As such, many have addressed delamination concerns and importance of strong adhesion to secure the interfaces between the substrate and the adhesive. − Therefore, a robust packaging solution, analogous to the one used in rigid thin-film PV modules, will ultimately be part of the approach to protect these moisture-sensitive devices from their adverse environment. − Packaging materials, including adhesives/encapsulants, protective frontsheets, and backsheets, are essential for manufacturing reliable PV modules. − For flexible thin-film PV modules, the conventional rigid glass substrates are replaced with flexible barrier film frontsheets and backsheets. From this transition, a new interface is now generated, i.e., flexible substrates/adhesives.…”