WO2013077866A1

WO2013077866A1 - Integrated films for use in solar modules

Info

Publication number: WO2013077866A1
Application number: PCT/US2011/061918
Authority: WO
Inventors: Jeffrey G. Linert; Andreas M. GRAICHEN; Rahul M. Rasal; Belma Erdogan-Haug; Howard S. Creel; Bruce H. Bengtson; Ainsley W. GRANT
Original assignee: 3M Innovative Properties Company
Priority date: 2011-11-22
Filing date: 2011-11-22
Publication date: 2013-05-30

Abstract

This disclosure generally relates to films capable of use in electronic device modules and to electronic device modules including such films. The disclosure also generally relates to materials for use in such films.

Description

INTEGRATED FILMS FOR USE IN SOLAR MODULES

Field of the Disclosure

This disclosure generally relates to films capable of use in a photovoltaic solar module and to photovoltaic solar modules including such films. The disclosure also generally relates to materials for use in such films.

Background

Three basic constructions of photovoltaic solar modules are commercially available. The first construction of solar module 10 is shown in Fig. 1 and includes a photovoltaic cell 20 embedded in encapsulant 30. Two protective layers (e.g., panels of glass or other suitable material) 40, 50 are positioned adjacent to the frontside and backside of the encapsulant. The encapsulant protects the fragile solar cells and adheres them to the frontside and backside protective layers. Typically, this solar module construction includes encapsulant on both sides of the solar cell. This can be accomplished, for example, by including a frontside layer of encapsulant (positioned to face the sun) and a backside layer of encapsulant (positioned furthest from the sun). Frontside encapsulant layers are preferably highly transmissive while backside encapsulant layers need not have the same level of transmissivity. Typical encapsulant layers include ethylene vinyl acetate (EVA) polymers. This construction of this type of photovoltaic solar modules is generally described in, for example, U.S. Patent Publication No. 2008/0078445.

The second construction of solar module 60 is shown in Fig. 2 and includes a photovoltaic cell 70 positioned between a single encapsulant layer 80 and a backing material 90. Solar module 60 also includes a protective layer 100 adjacent to encapsulant layer 80. As shown in Fig. 2, this solar module design includes a frontside encapsulant and no backside encapsulant. This construction of this type of photovoltaic solar module is generally described in, for example, U.S. Patent Publication No. 2008/0078445.

The third construction of solar module 110 is shown in Fig. 3 and includes a photovoltaic cell 120 positioned between a single encapsulant layer 130 and a protective layer 150. Solar module 1 10 also includes a backing layer 140 adjacent to encapsulant layer 130. As shown in Fig. 3, this solar module design includes a backside encapsulant and no frontside encapsulant. This type of construction of a photovoltaic solar module is generally described in, for example, U.S. Patent No. 5,248,349.

Backing layer 40, 90, 140 materials can include, for example, glass. Alternatively, backing layers 40, 90, 140 can be protective backsheets. Typically, protective backsheets for use in solar modules are multilayer films that electrically insulate the solar module and protect the solar module from the environment (e.g., moisture and dirt). Such protective backsheets typically include at least one layer including a fluoropolymer and multiple other layers including polymers (e.g., polyethene terephthalate (PET) polymers, polyethene naphthalate (PEN) polymers, polyesters, and polyamides). Summary

The inventors of the present disclosure recognized that while the crosslinked EVA encapsulant films often have high strength, they can suffer from a relatively high water vapor transmission rate, yellowing, and possible corrosion due to release of acetic acid.

Solar panel operating temperatures have been measured as high as 1 10° C. The inventors of the present disclosure recognized that encapsulant films including thermoplastic adhesives can soften at this elevated temperature, causing creep in the panel and possibly resulting in shorting of the photovoltaic cell. These encapsulant films may also be susceptible to UV-induced breakdown, necessitating inclusion of large amounts of UV absorber, which limits the amount of incident light that can be used to power the solar cell.

The inventors of the present disclosure also recognized that the use of thermoset adhesives in encapsulant layers can suffer from slower extrusion processing speeds, causing increased

manufacturing cost.

The inventors of the present disclosure also recognized that the commonly used protective backsheet ingredients are expensive and that, in many cases, tie layers or other additional ingredients have to be provided to achieve sufficient cohesion between the individual layers in the protective backsheet. Additionally, the backsheet materials described above may not sufficiently adhere to the commonly used encapsulants, which may decrease performance and/or durability. Also, the backsheet materials described above cannot be combined in a single process step to form a multilayer backsheet. Instead, the layers must be separately and subsequently bonded together, which increases manufacturing cost and may result in unstable interlayer bonding, which can negatively affect long term stability of the multilayer protective backsheet.

Consequently, the inventors of the present disclosure recognized a need for encapsulant films and materials that minimize the incidence of creep, shrinkage, light transmission, yellowing, corrosion, and delamination while maintaining or improving film processability and manufacturing cost. The inventors of the present disclosure have discovered encapsulant films, materials for use in such films, and solar modules including such films and materials that provide at least one of improved performance, cost, and processability.

Further, the inventors of the present disclosure recognized a need for multilayer, integrated backsheets having lower manufacturing costs without negatively affecting durability and

performance. Also, the inventors of the present disclosure recognized a need for backsheets that have good adhesion both between the individual layers within the multilayer backsheet and between the backsheet and the encapsulant layer(s). The inventors of the present disclosure have discovered integrated backsheet films, materials for use in such films, and solar modules including such films and materials that provide at least one of improved performance, cost, adhesion, and processability. Further, the inventors of the present disclosure recognized a need for a single multilayer integrated film that can be used in a solar module as both a protective backsheet and a backside encapsulant.

One exemplary embodiment of the present disclosure is a multilayer, integrated

film capable of use in a solar module including:

(1) an insulating layer including one or more cross-linked polyethene homopolymers or copolymers selected from a group consisting essentially of (a) polyethylene copolymers comprising more than 99% by mole of repeating units derived from ethene and (b) polyethylene copolymers comprising at least 50% by mole of repeating units derived from ethene and one or more alkene comonomers;

(2) a back layer including one or more cross-linked polyethene homopolymers or copolymers selected from a group consisting essentially of (a) polyethylene copolymers comprising more than 99% by mole of repeating units derived from ethene and (b) polyethylene copolymers comprising at least 50% by mole of repeating units derived from ethene and one or more alkene comonomers; and (3) an encapsulant layer including a polyolefin, a silane, one or more cross-linking agents, and a plasticizer.

One exemplary embodiment of the present disclosure is a solar module including one or more solar cells; and a multilayer integrated film as described herein.

One exemplary embodiment of the present disclosure is a method of making a multilayer integrated film, comprising: coextruding one or more of the insulating layer, the back layer, and the encapsulant layer to form a multilayer film as described herein; and cross-linking the coextrusion.

In some exemplary embodiments, the multilayer integrated films further include a top layer positioned adjacent to the insulating layer and opposite the back layer, wherein the top layer contains cross-linked polyethene homopolymers or copolymers, and wherein the cross-linked polyethene homopolymers or copolymers are selected from a group consisting essentially of (a) polyethene copolymers comprising more than 99% by mole of repeating units derived from ethene and (b) polyethene copolymers comprising at least 50% by mole of repeating units derived from ethene and further including one or more alkene comonomers.

In some exemplary embodiments, at least one of the insulating layer and the back layer include at least 60% by mole of repeating units derived from ethene and one or more alkene comonomers. In some exemplary embodiments, at least one of the insulating layer and the back layer include at least 80% by mole of repeating units derived from ethene and one or more alkene comonomers. In some exemplary embodiments, at least one of the insulating layer and the back layer include at least 95% by mole of repeating units derived from ethane. In some exemplary

embodiments, the insulating layer and the back layer each contain a polyethene selected from LLDPE, LDPE, MDPE, HDPE, or a combination thereof as a major component. In some exemplary embodiments, the multilayer film further includes one or more additional layers including a polyethene selected from LLDPE, LDPE, MDPE, HDPE, or a combination thereof as a major component. In some exemplary embodiments, the insulating layer contains no pigments. In some exemplary embodiments, the back layer contains carbon particles. In some exemplary embodiments, at least two of the layers of the multilayer film are coextruded. In some exemplary embodiments, at least one of the insulating layer, the back layer, the encapsulant layer, and the tie layer includes at least one of flame retardants and anti-dripping agents. In some exemplary embodiments, the insulating layer and the back layer are bonded together.

In some exemplary embodiments, the multilayer film has a dielectric breakdown voltage of at least 20 kV. In some exemplary embodiments, the multilayer film has a thickness of between about 0.25 mm and about 1.0 mm. In some exemplary embodiments, the multilayer film has at least one of (a) a reduction of dielectric breakdown voltage of less than 1% and (b) a reduction in elongation at break and tensile strength of less than 20% after being exposed to steam at a temperature of 121° C and a pressure of 1 bar for 100 hours.

In some exemplary embodiments, the plasticizer in the encapsulant layer is non-polar. In some exemplary embodiments, the plasticizer in the encapsulant layer is selected from a group consisting essentially of ethylene/a-olefin copolymers and C4-C10 polyolefin homopolymers. In some exemplary embodiments, the plasticizer in the encapsulant layer has a Tg<-50°C. In some exemplary embodiments, the plasticizer in the encapsulant layer has a Tg<-70°C. In some exemplary embodiments, the plasticizer in the encapsulant layer is liquid at 20°C. In some exemplary embodiments, the polyolefin in the encapsulant layer is an ethylene/a-olefin copolymer. In some exemplary embodiments, the a-olefin moiety of the ethylene/a-olefin copolymer includes four or more carbons. In some exemplary embodiments, the ethylene/a-olefin copolymer is a low crystalline ethylene/a-olefin copolymer. In some exemplary embodiments, the low crystalline ethylene/a-olefin copolymer has a DSC peak melting point of less than or equal to 50°C. In some exemplary embodiments, the low crystalline ethylene/a-olefin copolymer is a butene a-olefin. In some exemplary embodiments, the encapsulant layer includes greater than 70% by weight of low crystalline ethylene/a-olefin copolymer. In some exemplary embodiments, the silane in the encapsulant layer is an unsaturated alkoxysilane. In some exemplary embodiments, the unsaturated alkoxysilane is an acrylic alkoxysilane. In some exemplary embodiments, the one or more cross-linking agents in the encapsulant layer are one of a thermal curative and a photo-curative. In some exemplary embodiments, the thermal curative is a peroxide. In some exemplary embodiments, the encapsulant layer further includes a coagent. In some exemplary embodiments, the encapsulant layer further includes an additional resin. In some exemplary embodiments, the additional resin is an additional low crystalline ethylene/a-olefin copolymer. In some exemplary embodiments, the additional resin is one of an ethylene/butene copolymer and an ethylene/octene copolymer. In some exemplary embodiments, the encapsulant layer includes multiple layers.

Brief Description of the Drawings

The present disclosure may be more completely understood in consideration of the following detailed description of various embodiments of the disclosure in connection with the accompanying drawings, in which:

Fig. 1 is a cross-sectional schematic view of one type of prior art photovoltaic solar module. Fig. 2 is a cross-sectional schematic view of one type of prior art photovoltaic solar module. Fig. 3 is a cross-sectional schematic view of one type of prior art photovoltaic solar module. Fig. 4 is a cross-sectional schematic view of one embodiment of an integrated multilayer film.

The figures are not necessarily to scale. It will be understood that the use of a number to refer to a component in a given figure is not intended to limit the component in another figure labeled with the same number.

Detailed Description

In the following detailed description, reference may be made to the accompanying set of drawings that form a part hereof and in which are shown by way of illustration several specific embodiments. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present disclosure. The following detailed description, therefore, is not to be taken in a limiting sense.

The present disclosure generally relates to films capable of use in solar modules. The films of the present disclosure can be used in any type of photovoltaic solar module, including, for example, any of the specific solar module constructions described in the background. In one exemplary embodiment, a multilayer integrated film capable of use in a photovoltaic solar module includes:

(2) a back layer including one or more cross-linked polyethene homopolymers or copolymers selected from a group consisting essentially of (a) polyethylene copolymers comprising more than 99% by mole of repeating units derived from ethene and (b) polyethylene copolymers comprising at least 50% by mole of repeating units derived from ethene and one or more alkene comonomers; and

(3) an encapsulant layer including a polyolefin, a silane, one or more cross-linking agents, and a plasticizer. Each of these components of the multilayer integrated film will be discussed in greater detail below.

The integrated films described herein have a multilayerstructure. As shown in Fig. 4, when viewed from top (referred to herein as the side of the integrated film that is adjacent to (e.g., bonded to) the solar module) one exemplary integrated film 200 includes the following layers: an encapsulant layer 210, a top layer 220, an insulating layer 230, and a back layer 240. As stated above, top layer 220 need not be included in all embodiments. There may or there may not be other layers between some or all of these layers. In some embodiments, the insulating, back, and encapsulant layers are bonded directly to each other. In some embodiments, an adhesion promoting layers is between layers one or more of the insulating, back, and encapsulant layers.

In some embodiments, the combination of the layers has a thickness effective to provide the electrical breakdown voltage of at least 10 kV or at least 20 kV and / or some or all of the mechanical properties as described herein. In some embodiments, the integrated film has a thickness of between about 0.25 mm and about 1.0 mm. In some embodiments, the integrated film has a thickness of between about 0.35 mm and about 10 mm. In some embodiments, the integrated film has a thickness of between about 0.5mm and about 0.8 mm.

The insulating and back layers contain polyethene (PE) and/or polypropene (PP) polymers as their major component. As used herein, the term "major component" denotes that this component is present at the highest amount as expressed by percentage by weight based on the weight of the layer. In some embodiments, the PE and/or PP polymers are present in an amount of greater than 50% by weight. In some embodiments, the PE and/or PP polymers are present in an amount of greater than 75% by weight. In some embodiments, the PE and/or PP polymers are present in an amount of greater than 90% by weight. The weight percentages are based on the weight of the in which they are contained.

Polyethene polymers (PE's) include homo- and copolymers of ethene, i.e., polymers comprising repeating units derived from ethene. In some embodiments, the PE polymers contain more than 50% by mole; in other embodiments, more than 60% by mole; in other embodiments, more than 80% by mole, and in other embodiments, more than 95% by mole; in other embodiments, more than 99% by mole; and in other embodiments, 100% by mole of units derived from ethene. Some exemplary suitable comonomers include alkenes, in particular a-olefms (such as, but not limited to, propene, 1-butene, 1-hexene, 1-octene and combinations thereof). As used herein, the term "alkenes" refers to hydrocarbons with one carbon-carbon double bond and hydrocarbons with two carbon- carbon double bonds. The a -olefins may be branched or cyclic or linear. Further examples include 4-methyl- 1 -pentene, 1-decene, 1-dodecene, 1-tetracene, 1 -hexadecene, 1-octadecene. Suitable a- olefins include in general hydrocarbons of the general formula (C_nH_2n) with a terminal carbon-carbon double bond of up to 20 carbon atoms.

Examples of suitable PE polymers include, but are not limited to, UHMWPE (ultra high molecular weight polyethene; a polyethylene polymer with a molecular weight greater than 1 x 10⁶ g/mole - usually between 3.1 and 5.67 million g/moles - and a density of between about 0.930 to aboutO.935 g/cm³), HDPE (high density polyethene is a polyethylene polymer having a density of greater or equal to 0.941 g/cm³), MDPE (medium density polyethene is a polyethylene polymer having a density range of 0.926-0.940 g/cm³), LDPE (low density polyethene is a polyethene polymer having a density range of 0.910-0.940 g/cm³), LLDPE (linear low density polyethene is a polyethylene polymer having a density range of 0.915-0.925 g/cm³), and VLDPE (very low density polyethene is a polyethene polymer having a density range of 0.880-0.915 g/cm³). It has been found that not only polymers of the same architecture (e.g., only branched or only linear polymers) may be used but also polymers of different structures. For example, linear and non-linear polymers may be used in the integrated films described herein, and one layer may be prepared by a linear material (e.g., HDPE) and another layer may be prepared by a non- linear material (e.g., LDPE).

Polypropene polymers (PP's) include homo- and copolymers of propene, i.e., polymers comprising repeating units derived from propene. In some embodiments, the PP polymers contain more than 50% by mole; in other embodiments, more than 60% by mole; in other embodiments, more than 80% by mole, and in other embodiments, more than 95% by mole; in other embodiments, more than 99% by mole; and in other embodiments, 100% by mole of units derived from propene. Suitable comonomers include alkenes, in particular α-olefms such as but not limited to ethene, 1 -butene, 1 - hexene, 1 -octene and combinations thereof. The a-olefins may be branched or cyclic or linear.

Further examples include 4-methyl- 1 -pentene, 1 -decene, 1 -dodecene, 1 -tetracene, 1 -hexadecene, 1 - octadecene, and combinations thereof.

In some embodiments, the PE and PP polymers have a melting point of at least 100° C. The PE and PP polymers may be linear or branched. The PE and PP polymers may also be graft polymers, blockpolymers, core-shell polymers, or combinations thereof. Blends may be used.

Polyethenes and polypropenes are relatively inexpensive raw materials. Therefore, it is an advantage of the integrated films described herein that they can be prepared at low raw material costs while having the desired mechanical properties (e.g., elongation at break and/or tensile strength, electrical insulation, and/or long-term stability under moisture and heat).

Another advantage of the present integrated films is that several of the layers can be prepared in principle from the same or at least the same chemical type of polymeric material (i.e., polyethene or polypropene polymers). Consequently, at least some of the layers can be prepared from materials having the same or similar chemical composition and thus may have similar viscosity or density. As used herein in this context, the term "similar" refers to a deviation of less than 10%. This can increase the compatibility of the layers with each other such that tie-layers, primer, or adhesive layers may not be required to provide sufficient bonding of the individual layers. This may permit co-extrusion of the layers, which may obviate the use of adhesives and which may reduce manufacturing cost and film thickness. Some embodiments of the present disclosure are an integrated film free of one or more of the following polymers or polymer layers: fluoropolymers, polyester, polyamides, polyterepthalates, polyacetates, like polyvinylacetates, ethylvinylacetates, polycarbonates, and polyacrylates.

Some embodiments of the integrated films of the present disclosure are free of tie-layers. As used herein, the term "tie-layers" refers to polymeric layers between two dissimilar polymers that bind the dissimilar polymer layers. As used herein, the term "dissimilar polymer layers" refers to layers of two different chemical classes (e.g., polymers having the majority or repeating units derived from a different monomer, e.g., a polyamide versus a polyester). Typically, dissimilar polymers poorly bind to each other, so a tie layer is required. Examples of tie-layer polymers include polymers modified to contain functional groups like hydroxyl, epoxy, or amine, carboxylic acid groups, or anhydride groups.

The PE or PP polymers in the insulating and back layers are preferably in cross-linked form in the assembled integrated film but may be used in non-cross-linked form in the preparation of the integrated film. These layers may be prepared by non-cross-linked polymers but may be cross-linked afterwards either individually or combined. The cross-linking may be carried out chemically or physically. In chemical cross-linking, the composition contains a cross-linker as described below. The cross-linker may be activated thermally, by chemical reaction or by irradiation, typically UV irradiation. In physical cross-linking the cross-linking is achieved by irradiating the polymers with a- irradiation, β-irradiation, or e-beam irradiation. A cross-linking agent is not required and may not be present. Preferably, the cross-linking is carried out by bulk irradiation of all layers. The layers may be cross-linked by the same or different cross-linking methods or cross-linkers and may be subjected by the same cross-linking process together or separately. A combination of physical and chemical cross-linking may also be used.

The individual layers of the back layer will now be described in greater detail. Insulating Layer

As used herein, the term "insulating layer" refers to the layer that provides the majority of the electrical insulation. While other layers may provide such electrical insulation, the insulating layer provides a greater numerical proportion of the electrical insulation than any other individual layer. In some embodiments, the insulating layer is surface treated to create a pattern or structure or roughened surface. In some embodiments, the insulating layer has sufficient thickness to provide a dielectric breakdown voltage of the backsheet of at least 10 kV or at least 20 kV. The optimum thickness depends on the chemical composition of the layer, but some exemplary insulating layers have a thickness of at least 150 mm, at least 210 μηι, at least 310 μηι, or at least 350 μηι. In some embodiments, the upper thickness limit of the insulating layer is about 1 ,000 μηι.

In some embodiments, the insulating layer includes one or more of the PE polymers and PP polymers described herein. In some embodiments, the insulating layer includes up to about 10 wt %, up to about 5 wt %, or up to about 1 wt % of antioxidants based on the total weight of the layer. In some embodiments, the insulating layer includes up to about 10 wt %, up to about 5 wt %, or up to about 1 wt % of UV- stabilizers based on the total weight of the layer. In some embodiments, the insulating layer includes up to 1% wt or up to 10% wt of anti-dripping agents based on the weight of the layer. In some embodiments, the insulating layer includes up to 35% or up to 30% or up to 20% or up to 10% by weight of flame retardant based on the weight of the layer and has a dielectric break down voltage of at least 20 kV. The inclusion of flame retardants or anti-dripping agents may results in a film having good anti-burning behaviour while maintaining the desired mechanical, electrical, heat, and moisture properties described herein.

In some embodiments, the insulating layer does not include carbon particles (which may reduce the insulating properties of the layer) or inorganic pigments. As used herein, the term "free of refers to 0 to less than 1% wt based on the weight of the layer.

The multilayer integrated film of the present disclosure may include a single insulating layer or multiple insulating layers. The insulating layer(s) may include one or more sublayers.

Back Layer

The main purpose of the back layer is to protect the insulating layer from mechanical degradation and from the environment. Typically, the back layer has a thickness between about 50 and about 100 μηι. This layer may contain the same or a different polyolefins than the insulating layer. In some embodiments, the back layer includes one or more of carbon particles and/or pigments (e.g., white pigments). In some embodiments, the back layer is black in colour due the presence of substantial amounts of carbon particles. However, the layer can be of a different colour if pigments or paints are used. The carbon particles may be modified, for example surface treated, coated or may contain functionalised groups (e.g., by chemical reaction with chemical modifiers or by adsorption of chemicals). Carbon particles include graphite, fullerenes, nanotubes, soot, carbon blacks (e.g., carbon black, acetylene black, ketjen black). Typically, the back layer may contain from about 1% to about 6% or up to about 10% weight based on the weight of the layer of carbon particles. The loading with carbon particles may be increased but in that case the layer may become electron conductive. In this case the layer can be earthed when it is incorporated into a solar module.

In some embodiments, the back layer includes one or more of antioxidants, UV-absorbers, cross-linkers, flame retardants, and/or anti dripping agents. The amount of these ingredients may be individually or combined be from about 1% wt to 10% wt. It has been found that the back layer and/or integrated film is resistant enough to only show little yellowing upon extensive heat, dampness, or UV treatment.

The back layer may be in direct contact with the insulating layer or may be separated from the insulating layer by one or more intermediate layers. In some embodiments, the back layer forms a continuous interface with the insulating layer such that no tie layer, primer, or adhesive is between the two layers.

The back layer may include a cross-linked PE or PP polymer, preferably a cross-linked PE polymer. In some embodiments, the PE polymer is a high density PE. In some embodiments, the PE polymer is a low density PE.

In some embodiments, the back layer includes up to 35% or up to 30% or up to 20% or up to

10% by weight of flame retardant based on the weight of the layer and has a dielectric break down voltage of at least 20 kV. The inclusion of flame retardants or anti-dripping agents may results in a film having good anti-burning behaviour while maintaining the desired mechanical, electrical, heat, and moisture properties described herein.

Encapsulant Layer

Polyolefin

In some embodiments, the polyolefin is one or more of EVA, high density polyethylene, ionomers, polystyrene, and poly vinyl butarate.

In some embodiments, the polyolefin is an ethylene/a-olefin copolymer. As used herein, the term "ethylene/a-olefin copolymer" refers to polymers comprising a class of hydrocarbons manufactured by the catalytic oligomerization (i.e., polymerization to low-molecular- weight products) of ethylene and linear a-olefin monomers. The ethylene/a-olefin copolymers may be made, for example, with a single site catalyst such as a metallocene catalyst or multi-site catalysts such as Ziegler-Natta and Phillips catalysts. The linear a-olefin monomers typically are 1-butene or 1-octene but may range from C3 to C20 linear, branched or cyclic a-olefin. The a-olefin may be branched but only if the branch is at least alpha to the double bond, such as 3 -methyl- 1-pentene. Examples of C3- C20 a-olefins include propylene, 1 -butene, 4-methyl- 1 -butene, 1 -hexene, 1 -octene, 1 -dodecene, 1 - tetradecene, 1 -hexadecene and 1 -octadecene. The α-olefins can also contain a cyclic structure such as cyclohexane or cyclopentane, resulting in an a-olefin such as 3-cyclohexyl-l propene (allyl cyclohexane) and vinyl cyclohexane. Although not α-olefins in the classical sense of the term, for purposes of this disclosure certain cyclic olefins, such as norbornene and related olefins, are a-olefins and can be used. Similarly, styrene and its related olefins (for example, a-methyl styrene) are a- olefins for the purposes of this disclosure. Acrylic and methacrylic acid and their respective ionomers, and acrylates and methacrylates, however are not α-olefins for the purposes of this disclosure. Illustrative ethylene/a-olefin copolymers include ethylene/1 -butene, ethylene/ 1 -octene, ethylene/1 -butene/ 1 -octene, ethylene/styrene. The polymers can be block or random. Exemplary commercially available low crystalline ethylene/a-olefin copolymers include resins sold under the tradenames "ENGAGE" ethylene/ 1 -butene and ethylene/ 1 -octene copolymers and "FLEXOMER" ethylene/ 1 -hexene copolymer, available from Dow Chemical Co., and homogeneously branched, substantially linear ethylene/ α-olefin copolymers such as "TAFMER", available from Mitsui Petrochemicals Company Limited, and "EXACT", available from ExxonMobil Corp. As used herein, the term "copolymer" refers to polymers made from at least 2 monomers.

In some of these embodiments, the α-olefin moiety of the ethylene/a-olefin copolymer includes four or more carbons. In some embodiments, the ethylene/a-olefin copolymer is a low crystalline ethylene/a-olefin copolymer. As used herein, the term "low crystalline" means crystallinity (according to method disclosed in ASTM F2625-07) of less than 50% by weight. In some embodiments, the low crystalline ethylene/a-olefin copolymer is a butene a-olefin. In some embodiments, the a-olefin of the low crystalline ethylene/a-olefin copolymer has 4 or more carbons.

In some embodiments, the low crystalline ethylene/a-olefin copolymer has a DSC peak melting point of less than or equal to 50°C. As used herein, the term "DSC peak melting point" means a melting point determined by DSC (107min) under nitrogen purge as the peak with the largest area under the DSC curve.

In some embodiments, the film is greater than 35% by weight low crystalline ethylene/a- olefin copolymer. In some embodiments, the film is greater than 50% by weight low crystalline ethylene/a-olefin copolymer. In some embodiments, the film is greater than 70% by weight low crystalline ethylene/a-olefin copolymer.

In some embodiments, the film includes additional polyolefin resins. Exemplary additional resins include, for example, low crystalline ethylene/a-olefin copolymer, HDPE, and polystyrene. In embodiments where the additional resin is a low crystalline ethylene/a-olefin copolymer, the two copolymers could, for example, have respective DSC peak melting points of, for example, less than 50° C and greater than 50° C. In alternative exemplary embodiments, one low crystalline ethylene/a- olefin copolymer could have a DSC peak melting point of less than 50° C while the other low crystalline ethylene/a-olefin copolymer could have a DSC peak melting point of greater than 55° C, or greater than 60° C, or greater than 65° C, or greater than 70° C, or greater than 75° C. In another exemplary embodiment, one low crystalline ethylene/a-olefin copolymer has a DSC peak melting point of greater than 50° C while the other low crystalline ethylene/a-olefin copolymer has a DSC peak melting point of less than 45° C, or less than 40° C, or less than 35° C. In an alternative exemplary embodiment, one of the two low crystalline ethylene/a-olefin copolymers is

ethylene/butene copolymer and the other is an ethylene/octene copolymer.

Silane

Exemplary silanes for use in the encapsulant portions of the present disclosure include, for example, silanes that include an ethylenically unsaturated hydrocarbyl group (such as, for example, vinyl, allyl, isopropenyl, butenyl, cyclohexenyl or y-(meth)acryloxy allyl group) and a hydro lysable group (such as, for example, methoxy, ethoxy, formyloxy, acetoxy, propionyloxy, alkyl, arylamino, hydrocarbonyloxy or hydrocarbylamino groups). In some exemplary embodiments, the silane is an unsaturated alkoxysilane. In some exemplary embodiments, the unsaturated alkoxysilane is an acrylic silane. Some examples include vinyl trimethoxysilane, vinyl triethoxysilane, and 3- (meth)acryloxypropyl trimethoxysilane. Commercially available examples include "SILQUEST A 174 and SILQUEST A171".

The amount of silane is typically at least about 0.05%, for example 0.1%, for example 0.5%, for example 1.0%, for example 2.0%, for example 10.0%, or for example 10.0%.

Cross-Linking Agents

The encapsulants of the present disclosure may include one or more cross-linking agents. Exemplary cross-linking agents include, for example, thermal and photo cross-linking agents. Some exemplary thermal cross-linking agents include, for example, peroxides. Some exemplary peroxides include, for example, diacyl peroxides (such as, for example, dilauryl peroxide and didecanoyl peroxide), alkyl peresters (such as, for example, tert-butyl peroxy-2-ethylhexanoate), perketals (such as, for example, l, l-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane or l,l-di(tert- butylperoxy)cyclohexane), dialkyl peroxides (such as, for example, tert-butyl cumyl peroxide, di(tert- butyl) peroxide and dicumyl peroxide), C-radical donors (such as, for example, 3,4-dimethyl-3,4- diphenylhexane and 2,3-dimethyl-2,3-diphenylbutane), and azo compounds (such as, for example, 2,2'-azodi (2-acetoxypropane)). Additional exemplary azo compounds include those described in U.S. Patent Nos. 3,862, 107 and 4, 129,531, incorporated herein by reference. Some exemplary

commercially available peroxides include, for example, "LUPEROX TBEC", "LUPEROX 231", and "LUPEROX P. Mixtures of two or more cross-linking agents may be used.

The amount of cross-linking agent varies, but the minimum amount is the amount sufficient to afford the desired range of crosslinking. In some embodiments, the encapsulant layer includes at least about 0.05%. In some embodiments, the encapsulant layer includes at least about 0.5%. In some embodiments, the encapsulant layer includes at least about 1.0%. In some embodiments, the encapsulant layer includes at least about 2.0%. In some embodiments, the encapsulant layer includes at least about 5.0%.

Plasticizerfs

Preferred plasticizers for use in the films described herein are those that are non -fugitive and/or crosslink the polymers in the film. Plasticizers used in the films described herein may improve extrusion processing speed and reduce film shrinkage while increasing storage modulus (creep resistance) at temperatures between about 100° C and 200° C. The some embodiments, the plasticizers are not substantially tacky at normal handling or storage temperatures. In some exemplary embodiments, the plasticizer(s) used in the films are liquids at 20°C. In some exemplary embodiments, the plasticizer(s) do not act as a tackifier.

In some exemplary embodiments, the plasticizer(s) are non-polar. As used herein, the term "nonpolar plasticizer" means a nonpolar additive that increases the plasticity, fluidity, or flowability of a low crystalline ethylene/a-olefin polymer and has a MW of less than 10,000 as determined by ASTM D6474. As used herein, nonpolar plasticizers do not include, for example, common polar polyvinylchloride (PVC) plasticizers such as phthalic acid diesters (e.g., diethylphthlate,

dibutylphthlate, dioctylphthlate) or other polar ester plasticizers such as trimellitates, adipates, sebacates, maleates, citrates or benzoates. Examples of non-polar plasticizers include, for example, ethylene/a-olefin copolymers and C4-C10 polyolefin homopolymers. In some exemplary embodiments, the nonpolar plasticizer may be selected from the group consisting of ethylene/a-olefin copolymers and C4-C10 polyolefin homopolymers.

Exemplary commercially available nonpolar plasticizers include those under the tradename "SPECTRASYN" commercially available from ExxonMobil Chemical, Baton Rouge, LA,

"KAYDOL" white mineral oil commercially available from Sonneborn Refined Products B.V., Amsterdam, the Netherlands, "INDOPOL" polybutenes commercially available from Ineos

Oligomers, League City, TX, and "TRILENE" ethylene propylene (EP) or EPDM copolymers commercially available from Lion Copolymer, Baton Rouge, LA. The nonpolar plasticizer may have a Tg of less than -50°C, for example less than -55°C, for example less than -65°C, for example less than -70°C, or even for example less than -75°C. The plasticizer may have a DSC peak melting point of less than 80°C, for example less than 60°C, for example less than 40°C or even for example less than 20°C. In one embodiment the plasticizer is a liquid at 20°C.

In some exemplary embodiments, conventional plasticizer s such as are commonly used for polyvinyl chloride) are substantially absent. As used in this paragraph, the term "substantially absent," means that these compounds are not added deliberately to the compositions and - if present - comprise less than 0.5wt % of the total film composition.

In particular, plastic izers such as phthalates, adipates, trimellitate esters, polyesters, and other functionalized plasticizers as disclosed in, for example, US 3,318,835; US 4,409,345; WO 02/31044 Al; and PLASTICS ADDITIVES 499-504 (Geoffrey Pritchard, ed., Chapman & Hall 1998) are substantially absent.

The amount of plasticizer is typically at least about 0.5%. In some embodiments, the amount of plasticizer is at least about 1.0%. In some embodiments, the amount of plasticizer is at least about 2.0%. In some embodiments, the amount of plasticizer is at least about 5.0%. In some embodiments, the amount of plasticizer is at least about 10.0%. In some embodiments, the amount of plasticizer is at least about 20.0%. Additives

In some exemplary embodiments, the films of the present disclosure include a coagent. Exemplary coagents include, for example, free radical crosslinking coagents (promoters or co- initiators). Examples of such coagents include multifunctional vinyl monomers and polymers, triallyl isocyanuarate, trimethylolpropane tnmethylacrylate, divinyl benzene, acrylates and methacrylates of polyols, allyl alcohol derivatives, and low molecular weight polybutadiene. Sulfur crosslinking promoters include benzothiazyl disulfide, 2-mercaptobenothiazole and tetramethylthiuram tetrasulfide.

In some exemplary embodiments, the film further includes one or more UV absorbers. UV absorbers absorb light and can thereby protect polymeric materials and/or solar cells. Some exemplary UV absorbers include, for example, triazines, benzotriazoles, hydroxybenzophenones, hydroxyphenyltriazines, esters of benzoic acids, and mixtures of two or more thereof. In some exemplary embodiments, the films of the present disclosure include 0.01% UV absorber. In some exemplary embodiments, the films of the present disclosure include 0.1% UV absorber. In some exemplary embodiments, the films of the present disclosure include 0.5% UV absorber. In some exemplary embodiments, the films of the present disclosure include 1% UV absorber. Films including UV absorbers have "UV cutoffs." As used herein, the term "UV cutoff refers to the wavelength transmission of a film and means that the film will block substantially all UV light below the specified wavelength threshold. In some embodiments, the films of the present disclosure have a "UV cutoff of 310, 350, and 380 nm, respectively. Such films can, for example, include less than 0.5% of "TINUVIN 622" HALS, "CHIMASSORB 81" UV absorber, or "TINUVIN 460" UV absorber, respectively.

In some exemplary embodiments, the film includes one or more hindered amine light stabilizer ("HALS"). HALS are light stabilizers rather than absorbers and scavenges radicals by production of nitroxyl radicals. In some embodiments, inclusion of a HALS instead of a UV absorber may permit entry of more light energy into a solar cell. Some exemplary HALS include, for example, cyclic amines, secondary, tertiary, acetylated, N-hydrocarbyloxy substituted, hydroxy substituted N- hydrocarbyloxy substituted, or other substituted cyclic amines which are further characterized by a degree of steric hindrance, generally as a result of substitution of an aliphatic group or groups on the carbon atoms adjacent to the amine function.

In some exemplary embodiments, the films of the present disclosure include 0.01% HALS.

In some exemplary embodiments, the films of the present disclosure include 0.1% HALS. In some exemplary embodiments, the films of the present disclosure include 0.5% HALS. In some exemplary embodiments, the films of the present disclosure include 1% HALS.

Other additives include, for example, pigments such as carbon black and titanium dioxide; inorganic fillers such as talc, fumed silica, precipitated silica, barium sulfate and calcium carbonate; crosslinkers; anti-oxidants; scorch inhibitors; flame retardants; and catalysts for crosslinking such as organo tin compounds, for example di-n-butyl tin dilaurate. Other suitable catalysts include, for example titanium compounds and metal alkoxides, for example aluminum isopropoxide and zirconium isopropoxide.

In some embodiments, the encapsulant films include multiple layers. In one exemplary implementation, an encapsulant film of the present disclosure includes three or more layers. In one exemplary implementation of this, the cross-linking agent(s), silane, and/or polyolefin are in different layers. For example, the cross-linking agent(s) could be substantially or entirely in a center layer and the polyolefin and silane could be in the outer layers.

The encapsulant films and materials of the present disclosure perform at least some of the following advantages over currently available encapsulant films: minimization of the incidence of creep, shrinkage, yellowing, corrosion, and delamination while maintaining or improving light transmission, film processability, and manufacturing cost. Optional Layers

Some embodiments of the integrated film include one or more top layers positioned between the encapsulant layer and the insulating layer. A top layer may, for example, introduce a colour or a coloured pattern representing information or decoration into the solar module. Such colour or pattern can be introduced by printing it onto the top layer or by using a top layer containing pigments or a combination of pigments. In some embodiments, the top layer contains white pigments and/or reflective particles. The presence of a top layer may increase the efficiency of the solar module by reflecting light and may also or alternatively protect the insulating layer from degradation by preventing or hindering light and/or UV irradiation to be incident on the insulating layer. In some embodiments, the top layer is the same or a similar composition as the insulating or back layers. In some embodiments, the top layer includes one or more of UV-stabilisers, antioxidants, cross-linking agents, flame retardants, and anti-dripping agents. In some embodiments, the top layer has a thickness between about 10 μηι and about 150 μηι. In some embodiments, the top layer has a thickness between about 50 μηι and about 100 μηι. In some embodiments, the top layer includes one or more of a cross-linked PE polymer, a non-cross-linked PE polymer, a cross-linked PP polymer, and a non-cross-linked PP polymer. In some embodiments, the top layer is free of ionomers or acid copolymers.

In some embodiments, the multilayer integrated film includes one or more metal layers (e.g. , a metal foil may be incorporated, for example between the insulating and back layers). In some embodiments, a metal foil is positioned on the backside of the back layer (i.e., facing away from the insulating layer). In such embodiments, the metal foil can be covered by one or more additional layers (e.g., a polyolefinic layer containing polyolefins to protect the metal film from deterioration by weather and environment). The thickness of this optional metal layer may be in the range of 5 - 100 μηι based on the type of material used.

Some embodiments include one or more external protection layers. The external protection layer(s) are adjacent to the backside of the integrated film such that it is exposed to the environment from the non- light-receiving side of the solar module. Where present, this layer can include, for example, polyolefins, polyurethanes, polyarylates, silicones, fluoropolymers, and combinations thereof; additives that increase the film's UV stability, thermal stability, and/or resistance to oxidation or corrosion; flame retardants; anti-scratch materials; or easy-to-clean materials. It may also be a coloured layer to provide the outside of the integrated film with a color other than black.

Some embodiments include one or more scrim or net layers that may increase dimensional stability and handling properties. Scrim or net type layers may also improve the anti dripping performance during burning. Scrim or net layers may be, for example, net-shaped or non- woven layers of a polymeric or plastic material or organic or inorganic fibers. The Multilayer Integrated Film

A particular advantage of at least some embodiments of the multilayer integrated films described herein is that they provide long term electrical and mechanical protection against heat and moisture exposure. It has been found that the mechanical and electrical properties of the multilayer integrated films provided herein do not degrade or only degrade to a comparatively low degree after exposure to extreme heat and moisture conditions.

Some embodiments of the multilayer integrated films described herein have a dielectric breakdown voltage of at least 10 kV or at least 20 kV.

Some embodiments of the multilayer integrated films described herein have a total thickness between about 0.22 mm and about 0.80 mm. In some embodiments, the total thickness of the integrated film is between about 0.35 mm and about 0.70 mm. In some embodiments, the total thickness of the integrated film is between about 0.40 mm and about 0.65 mm. It is an advantage of the present disclosure that integrated films with such a small thickness provide at least some of the advantageous properties described herein.

The multilayer integrated films described herein provide mechanical protection of the solar module. Some embodiments of the multilayer integrated films have an elongation at break of at least 50% and a tensile strength of at least 20 MPa.

In some embodiments, at least a portion of the multilayer integrated films described herein is surface treated. Surface treatment may be carried out to improve the compatibility or adhesion to another surface or to provide a functional or decorative pattern or structure. Exemplary surface treatments include, for example, a plasma treatment (e.g., a Corona treatment that may be carried out under air or nitrogen atmosphere).

Some embodiments of the multilayer integrated films described herein have smooth surfaces on one or both external sides. Some embodiments of the multilayer integrated films described herein have rough surfaces on one or both external sides. Rough surfaces may facilitate deaeration during the lamination process when the integrated film is included in a solar cell module. Rough surfaces can be created by mechanical embossing or by melt fracture during extrusion of the sheets followed by quenching so that surface roughness is retained during handling.

Methods of Making the Multilayer integrated Films

The films of the present disclosure can be manufactured using known techniques in the art of film forming, including coating and curing on a release liner and extrusion coating. In some embodiments, the films are extruded. In some exemplary embodiments, the films of the present disclosure are delivered in film form. In some exemplary embodiments, the films of the present disclosure include a standard matte finish. In some exemplary embodiments, the films of the present disclosure are provided on a release liner.

The films of the present disclosure may be used in a solar module. The solar module may be of any type known in the art. In some embodiments, the films or compositions described herein can be used as an adhesive for a solar module. In such uses, the films or compositions may be referred to as an "assembly adhesive," since they are used to assemble and hold together at least two elements of the solar module.

Some exemplary embodiments of this disclosure are further illustrated by the following examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this disclosure. In these examples, all percentages, proportions and ratios are by weight unless otherwise indicated.

EXAMPLES

Example 1

An EVA-based encapsulant sold as "ENCAPSULANT 9000" was placed adjacent to the bottom layer of a backsheet. The backsheet was an extruded three-layer construction having the following thicknesses: 4mil/10mil/4mil. Each layer included 5% Polybatch UV1952 from A.

Schulman Inc, Akron, OH. The layers were each ebeamed with 40 megarads. The top layer included HDPE (sold by Hostalen GD 9550 from Lyondell Basell Industries, Houston TX) containing 10% Polyblack 4686 (sold by A. Schulman Inc, Akron, OH). The middle layer included Lupolen 3020k (sold by Lyondell Basel Industries, Houston TX) containing 10% Polyblack 4686 (sold by A.

Schulman Inc, Akron, OH). The bottom layer was Hostalen GD 9550 containing 20% Polybatch LL8000 (sold by A. Schulman Inc, Akron, OH).

Example 2

An EVA-based encapsulant sold as "ENCAPSULANT 9000" with a polyethylene scrim (McMaster Carr cat # 9314T23) was placed adjacent to the bottom layer of the backsheet used in Example 1.

Example 3

A polyolefin-based encapsulant was made by extruding the following mixture: "EXACT 9361" from Exxon Mobil Chemical, Baton Rouge(75 parts), "EXACT 8230" also from ExxonMobil (25 parts), "Luperox TBEC" from Arkema Inc, King of Prussia, PA (1 part), "TAICROS" from EVONIC Industries AG, Essen, Germany (0.8part), "SILQUEST A174" from Momentive

Performance Materials, Columbus, OH (0.8 part), "CHIMASSORB 81" from CIBA Specialty Chemicals Inc, Basel, Switzerland (0.3part). The encapsulant film also had a scrim between the backsheet and the encapsulant. The encapsulant film was placed adjacent to the bottom layer of the backsheet used in Example 1. The adhesion of the backsheet (back layer or back portion) to the encapsulant and glass was tested by laminating two layers of 18 mil encapsulant and between a 6 inch square piece of float glass and a 6 inch piece of the backsheet. An ultraviolet light was used to identify the tin side of the glass. The non tin side of the glass was cleaned with isopropanol. The construction was laminated in a typical solar module laminator (Spire Laminator 350) at 155° C using a cycle described in the table below.

The samples were allowed to equilibrate in a 21 ° C and 50Rh room for at least 24 hours and then cut into half inch wide strips. A 90 degree peel test was then performed, according to ASTM D6862-04, at a pulling rate of 6 inch per minute using an "MTS INSIGHT," lOkN extended length model, commercially available from MTS Systems Corporation, Eden Prairie, MN. Replicates were performed and an average adhesion value was calculated. The results are provided in Table I below.

Table I. Adhesion Test Results

In all cases, the encapsulant peeled cleanly off the glass showing excellent adhesion of the encapsulant to the backsheet.

As used herein, the terms "a", "an", and "the" are used interchangeably and mean one or more; "and/or" is used to indicate one or both stated cases may occur, for example A and/or B includes, (A and B) and (A or B). As used herein, the terms "comprises," "comprising," "includes," "including," "containing," "characterized by," "has," "having" or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus and including equivalents.

All references mentioned herein are incorporated by reference. Unless otherwise indicated, all numbers expressing feature sizes, amounts, and physical properties used in the present disclosure and claims are to be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein. Further, any numerical range recited herein is intended to include and to specifically disclose the end points specified and also all integers and fractions within that range. For example, a range of from 1% to 50% is intended to be an abbreviation and to expressly disclose the values 1% and 50% and also the values between 1% and 50%, such as, for example, 2%, 40%, 10%, 30%, 1.5 %, 3.9 % and so forth.

Various embodiments and implementation of the present disclosure are disclosed. The disclosed embodiments are presented for purposes of illustration and not limitation. The implementations described above and other implementations are within the scope of the following claims. One skilled in the art will appreciate that the present disclosure can be practiced with embodiments and implementations other than those disclosed. Those having skill in the art will appreciate that many changes may be made to the details of the above-described embodiments and implementations without departing from the underlying principles thereof. It should be understood that this disclosure is not intended to be unduly limited by the illustrative embodiments and examples set forth herein and that such examples and embodiments are presented by way of example only with the scope of the disclosure intended to be limited only by the claims set forth herein as follows.

Further, various modifications and alterations of the present disclosure will become apparent to those skilled in the art without departing from the spirit and scope of the present disclosure. The scope of the present disclosure should, therefore, be determined only by the following claims.

Claims

What is claimed is:

1. A multilayer film capable of use in a solar module, comprising

an insulating layer including one or more cross-linked polyethene homopolymers or copolymers selected from a group consisting essentially of (a) polyethylene copolymers comprising more than 99% by mole of repeating units derived from ethene and (b) polyethylene copolymers comprising at least 50% by mole of repeating units derived from ethene and one or more alkene comonomers;

a back layer including one or more cross-linked polyethene homopolymers or copolymers selected from a group consisting essentially of (a) polyethylene copolymers comprising more than 99% by mole of repeating units derived from ethene and (b) polyethylene copolymers comprising at least 50% by mole of repeating units derived from ethene and one or more alkene comonomers; and an encapsulant layer including a polyolefin, a silane, one or more cross-linking

agents, and a plasticizer.

2. The multilayer film of claim 1, further comprising:

a top layer positioned adjacent to the insulating layer and opposite the back layer, wherein the top layer contains cross-linked polyethene homopolymers or copolymers, and wherein the cross- linked polyethene homopolymers or copolymers are selected from a group consisting essentially of (a) polyethene copolymers comprising more than 99% by mole of repeating units derived from ethene and (b) polyethene copolymers comprising at least 50% by mole of repeating units derived from ethene and further including one or more alkene comonomers.

3. The multilayer film of any of the preceding claims, wherein at least one of the insulating layer and the back layer include at least 60% by mole of repeating units derived from ethene and one or more alkene comonomers.

4. The multilayer film of any of the preceding claims, wherein at least one of the insulating layer and the back layer include at least 80% by mole of repeating units derived from ethene and one or more alkene comonomers.

5. The multilayer film of any of the preceding claims, wherein at least one of the insulating layer and the back layer include at least 95% by mole of repeating units derived from ethane.

6. The multilayer film of any of the preceding claims, wherein the insulating layer and the back layer each contain a polyethene selected from LLDPE, LDPE, MDPE, HDPE, and a combination thereof as a major component.

7. The multilayer film of any of the preceding claims, further including one or more additional layers including a polyethene selected from LLDPE, LDPE, MDPE, HDPE, and a combination thereof as a major component.

8. The multilayer film of any of the preceding claims having a dielectric breakdown voltage of at least 20 kV.

9. The multilayer film of any of the preceding claims having a thickness of between about 0.25 mm and about 1.0 mm.

10. The multilayer film of any of the preceding claims wherein the insulating layer contains no pigments.

1 1. The multilayer film of any of the preceding claims wherein the back layer contains carbon particles.

12. The multilayer film of any of the preceding claims having at least one of (a) a reduction of dielectric breakdown voltage of less than 1% and (b) a reduction in elongation at break and tensile strength of less than 20% after being exposed to steam at a temperature of 121° C and a pressure of 1 bar for 100 hours.

13. The multilayer film of any of the preceding claims, wherein at least two of the layers are coextruded.

14. The multilayer film of any of the preceding claims, wherein at least one of the insulating layer, the back layer, the encapsulant layer, and the tie layer include at least one of flame retardants and anti-dripping agents.

15. The multilayer film of any of the preceding claims, wherein the insulating layer and the back layer are bonded together.

16. The multilayer film of any of the preceding claims, wherein the plasticizer in the encapsulant layer is non-polar.

17. The multilayer film of any of the preceding claims, wherein the plasticizer in the encapsulant layer is selected from a group consisting essentially of ethylene/a-olefin copolymers and C4-C10 polyolefin homopolymers.

18. The multilayer film of any of the preceding claims, wherein the plasticizer in the encapsulant layer has a Tg<-50°C.

19. The multilayer film of any of the preceding claims, wherein the plasticizer in the encapsulant layer has a Tg<-70°C.

20. The multilayer film of any of the preceding claims, wherein the plasticizer in the encapsulant layer is liquid at 20°C.

21. The multilayer film of any of the preceding claims, wherein the polyolefin in the encapsulant layer is an ethylene/a-olefin copolymer.

22. The multilayer film of claim 21, wherein the a-olefin moiety of the ethylene/a-olefin copolymer includes four or more carbons.

23. The multilayer film of claim 21, wherein the ethylene/a-olefin copolymer is a low crystalline ethylene/a-olefin copolymer.

24. The multilayer film of claim 23, wherein the low crystalline ethylene/a-olefin copolymer has a DSC peak melting point of less than or equal to 50°C.

25. The multilayer film of claim 23, wherein the low crystalline ethylene/a-olefin copolymer is a butene a-olefin.

26. The multilayer film of any of the preceding claims, wherein the encapsulant layer includes greater than 70% by weight of low crystalline ethylene/a-olefin copolymer.

27. The multilayer film of any of the preceding claims, wherein the silane in the encapsulant layer is an unsaturated alkoxysilane.

28. The multilayer film of claim 27, wherein the unsaturated alkoxysilane is an acrylic alkoxysilane.

29. The multilayer film of any of the preceding claims, wherein the one or more cross- linking agents in the encapsulant layer are one of a thermal curative and a photo-curative.

30. The multilayer film of claim 29, wherein the thermal curative is a peroxide.

31. The multilayer film of any of the preceding claims, wherein the encapsulant layer further includes a coagent.

32. The multilayer film of any of the preceding claims, wherein the encapsulant layer further includes an additional resin.

33. The multilayer film of claim 32, wherein the additional resin is an additional low crystalline ethylene/a-olefin copolymer.

34. The multilayer film of claim 32, wherein the additional resin is one of an ethylene/butene copolymer and an ethylene/octene copolymer.

35 The multilayer film of any of the preceding claims, wherein the encapsulant layer includes multiple layers.

36. The multilayer film of any of the preceding claims in a solar cell module.

37. A solar module, comprising:

one or more solar cells; and

the multilayer film of any of the preceding claims.

38. A method of making a multilayer film, comprising:

coextruding one or more of the insulating layer, the back layer, and the encapsulant layer to form the multilayer film of any of the preceding claims; and

cross-linking the coextrusion.

39. A method of making a solar module, comprising:

vacuum laminating the multilayer film of any of the preceding claims to a solar module.

40. A method of making a multilayer film, comprising:

assembling the insulating layer, the back layer, and the encapsulant layers to form the multilayer film of any of the preceding claims using at least one of laminating or adhesion;

cross-linking the multilayer film.