Predicting the reliability of polyisobutylene seal for photovoltaic application

Panchagade

Reese

et al. 2014

Photovoltaic devices are often sensitive to moisture and must be packaged in such a way as to limit moisture ingress for 25 years or more. Typically, this is accomplished through the use of impermeable front and backsheets (e.g., glass sheets or metal foils). However, this will still allow moisture ingress between the sheets from the edges. Attempts to hermetically seal with a glass frit or similarly welded bonds at the edge have had problems with costs and mechanical strength. Because of this, low diffusivity polyisobutylene materials filled with desiccant are typically used. Although it is well known that these materials will substantially delay moisture ingress, correlating that to outdoor exposure has been difficult. Here, we use moisture ingress measurements at different temperatures and relative humidities to find fit parameters for a moisture ingress model for an edge-seal material. Then, using meteorological data, a finite element model is used to predict the moisture ingress profiles for hypothetical modules deployed in different climates and mounting conditions, assuming no change in properties of the edge-seal as a function of aging.

Section: Discussionmentioning

confidence: 99%

“…Thin film photovoltaic (PV) technologies are often packaged using moisture impermeable front‐sheets and back‐sheets because of greater sensitivity to moisture relative to crystalline Si modules . However, these types of packages are not considered hermetic as moisture may still diffuse in from the sides .…”

Section: Introductionmentioning

confidence: 99%

Modeling moisture ingress through polyisobutylene‐based edge‐seals

Panchagade

Reese

et al. 2014

“…Many types of photovoltaic (PV) technologies are sensitive to moisture [1][2][3][4][5][6][7][8][9]. The use of an impermeable frontsheet and backsheet (e.g., a glass/glass laminate package) significantly reduces moisture ingress, but moisture may still diffuse in from the sides [10].…”

Section: Introductionmentioning

confidence: 99%

Evaluation of moisture ingress from the perimeter of photovoltaic modules

Dameron

Reese

2013

Many thin film photovoltaic (PV) technologies can be sensitive to corrosion induced by the presence of water vapor in the packaging materials. Typically impermeable front and backsheets are used in conjunction with an edge‐seal around the perimeter to prevent water vapor ingress. These edge‐seal materials are often made of a polyisobutylene resin filled with desiccant, which dramatically increases the time for moisture to reach sensitive module components. While edge‐seals can prevent moisture ingress, even the lowest diffusivity transparent encapsulant materials are insufficient for the lifetime of a module. To evaluate the performance of edge‐seal and encapsulant materials in a manner that simulates their function in a PV module, an optical method was devised where ingress is detected by reaction of a Ca film with water. Using this method, we have exposed test samples to heat and humidity allowing quantitative comparison of different edge‐seal and encapsulant materials. Next, we use measurements of polymer diffusivity and solubility to evaluate the ability to model this moisture ingress. Here, we find good agreement between these two methods highlighting the much greater ability of polyisobutylene materials to keep moisture out as compared with typical encapsulant materials used in the PV industry. Copyright © 2013 John Wiley & Sons, Ltd.

“…Both Si and thin film photovoltaic technologies are sensitive to the presence of water, and certain failure modes will be accelerated once significant moisture has entered the package . Typically, the perceived risk is higher for thin film technologies, where important film layers are on the order of 1‐μm thick, as opposed to crystalline Si technologies using a much thicker active layer and contacts . However, moisture‐induced corrosion has been observed in Si modules in the field and other failure modes that are accelerated or caused by the application of high voltages or leakage currents could be greatly accelerated by the presence of moisture…”

Section: Introductionmentioning

confidence: 99%

“…[1][2][3] Typically, the perceived risk is higher for thin film technologies, where important film layers are on the order of 1-μm thick, as opposed to crystalline Si technologies using a much thicker active layer and contacts. [1][2][3][4][5][6][7][8][9] However, moisture-induced corrosion has been observed in Si modules in the field and other failure modes that are accelerated or caused by the application of high voltages or leakage currents could be greatly accelerated by the presence of moisture. 10 To keep moisture out for the 25 + year expected lifetime of a module, impermeable front and backsheets are used in conjunction with a polyisobutylene (PIB)-based edge seal material.…”

Section: Introductionmentioning

confidence: 99%

Moisture ingress prediction in polyisobutylene‐based edge seal with molecular sieve desiccant

Nobles

Postak³

et al. 2017

Often photovoltaic modules are constructed with materials that are sensitive to water. This is most often the case with thin film technologies, including perovskite cells, where the active layers are a few microns thick and can be sensitive to moisture, liquid water or both. When moisture or liquid water can ingress, a small amount of water can lead to corrosion and depending on the resulting reactions, a larger local detrimental effect is possible. To prevent moisture from contacting photovoltaic components, impermeable frontsheets and backsheets are used with a polyisobutylene (PIB)‐based edge seal material around the perimeter. Here, we evaluate the ability of a PIB‐based edge seal using a molecular sieve desiccant to keep moisture out for the expected module lifetime. Moisture ingress is evaluated using test coupons where the edge seal is placed between 2 pieces of glass, one of which has a metallic calcium film on it, and monitoring the moisture ingress distance as a function of time. We expose samples to different temperature and humidity conditions to create permeation models useful for extrapolation to field use. This extrapolation indicates that this PIB material is capable of keeping moisture out of a module for the desired lifetime.