WO2025061800A1

WO2025061800A1 - Photovoltaic back contact module comprising a perforated rear insulator

Info

Publication number: WO2025061800A1
Application number: PCT/EP2024/076163
Authority: WO
Inventors: Frank Duijnhoven Van; Guido Josephina Wilhelmus MEIJERS; Christopher THELLEN; Kristof Proost
Original assignee: Endurance Solar Solutions Inc
Current assignee: Endurance Solar Solutions Inc
Priority date: 2023-09-18
Filing date: 2024-09-18
Publication date: 2025-03-27
Anticipated expiration: 2026-03-18

Abstract

The present invention relates to a photovoltaic back contact module comprising a co-extruded perforated rear insulator comprising two outer polymer layers and at least one inner polymer layer whereby the inner polymer layer has a melting point T 1 above a 160 °C while both outer polymer layer(s) have a melting point T2 below 155 °C whereby both outer layers comprise at least a polymer comprising functional groups chosen from acrylates, maleic anhydride, epoxy, silane and/or methacrylate. The invention also relates to the co-extruded perforated rear insulator as such.

Description

PHOTOVOLTAIC BACK CONTACT MODULE COMPRISING A PERFORATED REAR INSULATOR

The present invention relates to a photovoltaic back contact module comprising a perforated rear insulator. The invention also relates to the perforated rear insulator.

Photovoltaic modules are an important source of renewable energy. They comprise photovoltaic cells that release electrons when exposed to sunlight, thereby generating electricity. Photovoltaic cells, which are usually semiconductor materials, may be fragile and are typically encapsulated in polymeric materials that protect them from physical shocks and scratches. The encapsulated photovoltaic cells are generally further protected on each side by a protective layer that is both electrically insulating and resistant to weathering, abrasion or other physical insults, for the lifetime of the photovoltaic module.

As a sustainable energy resource, the use of photovoltaic modules is rapidly expanding. A preferred way of manufacturing a photovoltaic module involves forming a pre-lamination assembly preferably comprising at least 5 structural layers. The pre-lamination assemblies are constructed in the following order starting from the front or top layer (that is the layer first contacted by light) and continuing to the layer furthest removed from the front or top layer: (1) front layer may be a glass plate or polymer glass plate, (2) a front encapsulant layer (3) solar cells (4) a back encapsulant layer and (5) a backsheet.

Typical encapsulants possess a combination of characteristics such as high impact resistance, high penetration resistance, good ultraviolet (UV) light resistance, good long term thermal stability, adequate adhesion strength to glass and/or other rigid polymeric sheets, high moisture resistance, and good long term weatherability.

Examples of encapsulants are ionomers, ethylene vinyl acetate (EVA), poly(vinyl acetal), polyvinylbutyral (PVB), thermoplastic polyurethane (TPU), polyvinylchloride (PVC), metallocene-catalyzed linear low density polyethylenes, polyolefin block elastomers, poly(ethylene-co-alkyl acrylates), silicone elastomers or epoxy resins. Ethylene-vinyl acetate copolymer (EVA) is the most commonly used encapsulant material. EVA sheets or layers are usually inserted between the solar cells and the top surface (called front encapsulant layer) and between the solar cells and the rear surface (called a back encapsulant layer). Generally, a solar cell pre-lamination assembly incorporates at least two encapsulant layers sandwiched around the solar cells, being the front and back encapsulant. In addition, the optical properties of the front encapsulant layer may be such that light can be effectively transmitted to the solar cell.

Encapsulants such as the front and back encapsulant layers used in solar modules are typically designed to be continuous layers without holes or gaps. The primary purpose of the encapsulant is to protect the solar cells from environmental factors, such as moisture, dust, and physical damage.

In the present invention a photovoltaic back contact module is provided with a front and/or back encapsulant comprising a perforated rear insulator instead of a classic back encapsulant.

A back-contact module has solar cells incorporated which have the electrical contacts at the back of the solar cell. The contacts of the solar cells can be connected to a patterned conductive metal foil via a conductive solder paste or low temperature solder. The solar cells are separated via the perforated rear insulator. To be able to place the conductive paste or the low temperature solder for electrically connecting the back contact cells, holes are needed in this rear insulator or back encapsulant.

In the present invention it has been found that the classic front encapsulants such as ethylene vinyl acetate ("EVA") cannot be used as a perforated rear insulator, because of the flow behavior of EVA during lamination of the module will result in closing the holes of this EVA rear insulator, Consequently, the electrical connection between the cell and the patterned conductive metal foil will be lost leading to lower power output of the back contact module.

Laminated perforated rear insulators are available in the market which prevent closing of the holes during lamination. However, the laminated perforated rear insulators have a (very) low adhesion to both the cells and the patterned conductive metal foil. The adhesion further decreases during lifetime of the back contact module due to moisture and oxygen ingress leading to delamination of the laminated perforated rear insulator in the field. Delamination results in loss of electrical insulation, possibly shunts and lower power output over time.

The object of the present invention is to solve both above mentioned problems, i.e. providing a perforated rear insulator with both low flow during pre lamination and high adhesion to the back contact cells and patterned conductive metal foil. An object of the present invention is to provide a photovoltaic back contact module comprising a perforated rear insulator which remains stable during lamination of the PV module.

A further object of the present invention is to provide a photovoltaic back contact module comprising a perforated rear insulator from which the holes do not close during lamination of the module.

It is still a further object of the present invention to provide a photovoltaic back contact module comprising a perforated rear insulator that improves the electrical insulation properties of the solar module.

The object of the present invention has been achieved in providing a photovoltaic back-contact module comprising a co-extruded perforated rear insulator comprising two outer polymer layers and at least one inner polymer layer whereby the inner polymer layer has a melting point T 1 above 160 °C while both outer polymer layer(s) have a melting point T2 below 155 °C whereby both outer layers comprise at least a polymer comprising functional groups chosen from acrylate, maleic anhydride, epoxy, silane and/or methacrylate groups.

Surprisingly it has been found that the photovoltaic back contact module comprising for example EVA as front encapsulant layer and a co-extruded rear insulator comprising perforations remains stable during lamination of the module, which means that the flow of the co-extruded perforated rear insulator prevent closing of the holes during lamination and the high adhesion the co-extruded perforated rear insulator in the module prevents delamination during application in the field due to ageing.

The photovoltaic back contact module of the present invention typically comprises (1) front layer such as a glass plate or polymer glass plate, (2) a front encapsulant layer (3) solar cells (4) the co-extruded perforated rear insulator and (5) a conductive backsheet.

The front layer is typically a glass plate or especially for flexible modules a layer of fluorinated polymers like ETFE (ethylene tetrafluorethylene) or PVDF (polyvinylidene fluoride).

The front encapsulant layer is designed to encapsulate and protect the fragile solar cells. The "front side" corresponds to a side of the photovoltaic cell irradiated with light, i.e. the light-receiving side, whereas the co-extruded perforated rear insulator corresponds to the reverse side of the light- receiving side of the photovoltaic cells. Suitable polymer materials used as encapsulants typically possess a combination of characteristics such as high impact resistance, high penetration resistance, good ultraviolet (UV) light resistance, good long term thermal stability, adequate adhesion strength to glass and/or other rigid polymeric sheets, high moisture resistance, and good long-term weather ability. Currently, ethylene/vinyl acetate (EVA) copolymers are the most widely used encapsulants.

The co-extruded perforated rear insulator comprises two outer polymer layers which have a melting point T2 below 155 °C whereby both outer layers comprise at least a polymer comprising functional groups chosen from acrylate, maleic anhydride, epoxy, silane and/or methacrylate groups. Preferably the melting point of the outer layers varies between 125-155 °C. In any case the melting point of the outer layers should be chosen such that the rear insulator remains stable during lamination of the PV module.

The outer layers comprise at least a polymer comprising functional groups chosen from acrylate, maleic anhydride, epoxy, silane and/or methacrylate groups. Preferably the outer layers comprise a functionalised terpolymer and/or a functionalised polyolefin elastomer (POE). Examples of functionalised terpolymers are Lotader4613, Bynel 21 E810. Preferably the functionalised terpolymer is chosen from a silane functionalized polyolefin elastomer or a maleic-anhydride-alkyl-(meth)-acrylate functionalised terpolymer such as maleic-anhydride ethyl acrylate-, maleic-anhydride ethyl methacrylate-, maleic-anhydride butyl acrylate-, maleic-anhydride butyl methacrylate- terpolymers. Examples of functionalised polyolefin elastomers are low density polyethylene (LDPE), linear low density polyethylene (LLDPE), high density polyethylene (HDPE), very low density polyethylene (VLDPE) or POE's comprising functional groups chosen from acrylate, maleic anhydride, epoxy, silane and/or methacrylate groups. Polyolefin elastomers (POE's) are a range of copolymers based on metallocene catalysis utilizing butene or octene comonomers. Key characteristics of POE's are their low hardness, low density and high impact I toughness. Preferably a maleic anhydride functionalized polyolefin elastomer and/or silane functionalized polyolefin elastomer is used in the outer layers. More preferably both outer layers comprise a maleic anhydride functionalized polyolefin elastomer. Still more preferably both outer layers are identical.

The outer layers preferably have a thickness in the range of 25-80 pm. More preferably the outer layers have a thickness which is in the range of 25 to 75 pm. Most preferably the outer layers have the same thickness. The co-extruded perforated rear insulator used in the back contact module of the present invention comprises an inner layer or core layer having a melting point above 160 °C. Preferably the melting point of the inner layer varies between 160- 170 °C. The inner layer preferably comprises a polyolefin or a polyester chosen from polypropylene, polyethylene terephthalate (PET) or polybutylene terephthalate (PBT). The inner or core layer preferably has a thickness in the range of 40-95pm. More preferably the inner layer has a thickness in the range of 50-65 pm.

The perforated rear insulator comprises perforations such as openings which openings are preferably spaced holes. These perforations can be created through various methods, such as mechanical punching, laser cutting, or other precision manufacturing processes. The size, shape, and distribution of the perforations can be customized to meet specific requirements. Preferably the perforations are holes having a diameter between 0.5-5 mm. More preferably the holes have a diameter between 1.5-3 mm.

The co-extruded perforated rear insulator of the present invention may further comprise a tie layer between the outer and the core layer at both sides of the core layer. The tie layer preferably comprises at least a polymer with a melting point below 110°C. More preferably the tie layer comprises propylene-ethylene copolymers. Most preferably the tie layer comprises a mixture of at least two polymers whereby one of the polymers has a melting point below 110°C.The tie layers preferably comprise a mixture of a polyolefin and polyolefin elastomer (POE). Examples of the polyolefins are low density polyethylene (LDPE), linear low density polyethylene (LLDPE), high density polyethylene (HPDE). Examples of the polyolefin elastomer are copolymers of ethylene with butene, hexene, octene or decene. Commercial POE's are for example Engage®, Versify® or Sequel®.

The amount of polyolefin and polyolefin elastomer in the tie layer may vary between 10-90 wt% of the polyolefin and between 90-10 wt% of the polyolefin elastomer based on the total weight of the tie layer. As used herein, wt.% refers to percentage by weight of the specified polymer based on the weight of the layer in which the polymer is present. The tie layer preferably has a thickness in the range of 1- 40 pm, preferably a thickness in the range 10-15 pm.

The co-extruded perforated rear insulator used in the back contact module of the present invention preferably has a total thickness in the range of 95- 350pm. Preferably a total thickness in the range of 150-280 pm, more preferably a total thickness in the range of 180-210 pm. The perforated rear insulator is co-extruded rather than laminated.

Co-extrusion is often used to achieve the main advantage of laminated materials; the ability to impart different properties to the surface as compared to the core. Unlike laminated materials, co- extruded materials have the added benefit that delamination cannot occur. Coextrusion is the process of forming an extrudate composed of more than one thermoplastic melt stream. Separate extruders are required for each distinct material in the coextrusion. The process has two variations, depending on the point at which the separate melt streams are brought together. In feed block coextrusion, the streams are merged into a single laminar melt flow in a feedblock, which is positioned immediately upstream of the extrusion die. The alternative, die coextrusion, uses a complex die construction in which separate melt path manifolds are arranged to merge at a point close to the die exit.

The photovoltaic back contact module of the present invention may comprise EWT (emitter-wrap-through) or MWT (metal-wrap-through) or IBC (interdigitated back-contact) or heterojunction solar cells which are typically combined with a conductive backsheet for contacting the electrical contacts on the rear surface of the solar cells.

The conductive backsheet comprises at least a polymer layer and a metal layer. For connection of a junction box at the back of the module, the backsheet at the rear side of the module should be locally opened and tabs from the junction box soldered to the conductive layer. The metal used in the metal layer includes but is not limited to copper, tin, silver or nickel, or mixtures of two or more thereof or alloys of two or more thereof. Preferably the metal layer is a copper layer. The metal layer typically comprises a pattern. Such pattern can be obtained through known patterning technologies such as mechanical milling, chemical etching, laser ablation and die cutting. Laser ablation, mechanical milling or die cutting are preferably used.

The backsheet as mentioned herein above means a backsheet that is composed of at least one polymeric layer. In the case that one polymeric layer is present, the back-sheet is called a monolayer backsheet. In the case that more polymeric layers are present, the backsheet is called a multilayer backsheet. The conductive backsheet used in the present invention preferably comprises at least 2 and up to 8 polymeric layers.

The polymeric layer(s) as mentioned herein comprise thermoplastic or thermosetting polymers. A thermoplastic polymer is a polymer that becomes pliable or moldable above a specific temperature and solidifies upon cooling. Thermoplastics differ from thermosetting polymers in that thermosetting polymers form irreversible chemical bonds during a curing process. Thermosets do not melt, but decompose and do not reform upon cooling. Thermoplastic polymer layers are preferred. The thermoplastic polymers used in the conductive back-sheet are selected from the group consisting of polyolefines, polyamides, polyesters, fluorinated polymers, or combinations thereof.

Preferably the conductive backsheet is a multilayer back-sheet. The backsheet for example comprises a functional layer, a structural layer or core layer and a weatherable layer.

The functional layer may comprise a polyethylene alloy and a semicrystalline polymer with a melting point above 140°C. Examples of semi-crystalline polymers are semi-crystalline polyolefins such as for example polyethylene, polypropylene homo-and copolymers and/or polybutylene, with polypropylene homo-or copolymers being the most preferred. Examples of semi-crystalline polypropylenes useful in the present invention are 3270 9119 from ATOFINA™, BP™ Accpro 9346, BASELLADSTIF™ HA722J, and SUNOCO™ PPF-050-HC. The polyethylene (PE) alloy in the functional layer preferably comprises "polar" polyethylene, for example ethylene copolymerized with polar co-monomers chosen from vinyl acetate, acrylic and methacrylic ester such as methylacrylate, ethylacrylate, butylacrylate or ethylhexylacrylate. Preferably, ethylene is co-polymerised with methylacrylate.

The structural layer may comprise a polyolefin. Examples of polyolefins are ethylene or propylene homo-and copolymers such as polyethylene or polypropylene. The polypropylene may in principle be of any customary commercial polypropylene type, such as an isotactic or syndiotactic homo-or copolymer. The copolymer can be a random-or block-copolymer. The polyolefins can be prepared by any known process, as for example by the Ziegler-Natta method or by means of metallocene catalysis. It is possible to combine the polyolefins with an impactmodifying component, for example a rubber such as EPM rubber or EPDM rubber or SEBS. Optionally the polyolefins are functionalized with functional groups such as maleic anhydride grafted polyethylene or maleic anhydrate grafted polypropylene.

Also flexible polypropylene (FPP) being mechanical or reactor blends of polypropylene (homo or copolymer) with EPR rubber (ethylene propylene rubber) are possible. Examples of such reactor blends are Hifax CA 10 A, Hifax CA 12, Hifax CA7441A, supplied by LyondellBasell, or thermoplastic vulcanisates blends like Santoprene. Such thermoplastic vulcanisates are based on blend of polypropylene with EPDM rubber which are partly crosslinked. Examples of mechanical blends are blends of polypropylene with elastomers such as Versify 2300.01 or 2400.01 (supplied by Dow) Another type of mechanical blend is polypropylene with LLDPE (linear low densitiy polyethylene) or VLDPE (very low density polyethylene) plastomers (like Queo 0201 or Queo 8201 supplied by Borealis Plastomers), or copolymers of Ethylene with a polar co-monomer such as vinyl acetate or alkyl acrylates.

The weather-resistant layer may comprise for example a polyamide or a polyolefin. The polyamide is preferably chosen from PA46, PA6, PA66, PA MXD6, PA610, PA612, PA10, PA810, PA106, PA1010, PA1011 , PA1012, PA1210, PA1212, PA814, PA1014, PA618, PA512, PA613, PA813, PA914, PA1015, PA11 or PA12. The weather-resistant layer may further comprise titanium dioxide or barium sulfate, a UV stabilizer and a heat stabilizer. The polyolefin may be ethylene or propylene homo-and copolymers such as polyethylene or polypropylene such as described for the structural layer.

The backsheet may further comprise adhesive layers between the functional layer and the structural layer and between the structural layer and the weatherable layer. The adhesive layer may comprise polyurethane, acrylate based polymers or polyolefines. Examples of polyolefines are maleic anhydride grafted polyolefine such as maleic anhydride grafted polyethylene or polypropylene, an ethylene-acrylic acid copolymer or an ethylene-acrylic ester-maleic anhydride terpolymer. Preferably, the adhesive layer comprises maleic anhydride grafted polyolefine such as a maleic anhydride grafted polyethylene or a maleic anhydrate grafted polypropylene.

The polymeric layers in the conductive back-sheet may comprise additives known the art. Preferably the polymer layers comprise at least one additive selected from UV stabilizers, UV absorbers, anti-oxidants, thermal stabilizers and/or hydrolysis stabilizers. When such additives stabilizers are used, a polymeric layer may comprise from 0.05-10 wt.% more preferably from 1- 5 wt.%, based on the total weight of the polymer.

White pigments such as talc, mica, TiO2, ZnO or ZnS may be added to the to one or more polymeric layers of the conductive back-sheet to increase backscattering of sunlight leading to increased efficiency of the PV module. Black pigments such as carbon black or iron oxide may be added for esthetic reasons but also for UV adsorption. The present invention will now be described in detail with reference to the following non-limiting examples which are by way of illustration only.

FIGURES

Figure 1 : Schematics of the built-up of a back contact module: 1)glass; 2) front encapsulant; 3) solar cell; 4)low-temperature solder; 5)rear perforated insulator; 6)conductive backsheet

Figure 2: Shows the construction of the RPI

MATERIALS

• Queo 8210 is an ethylene based octene-1 plastomer,

• LOTADER® 4613 by SK Functional Polymer is random terpolymer of ethylene, acrylic ester and maleic anhydride

• LOTADER® AX8900 is a random ethylene-methyl acrylate-glycidyl methacrylate terpolyme

• Yparex 0H247 is a maleic-anhydride-(MAH)-functionalised LDPE

• Vistamaxx 6202 is a random copolymer of isotactic propylene with ethylene

• Polypropylene K8003 is an impact-resistant polypropylene resin with ethylene as the copolymer monomer produced by INEOS’ INNOVENE gas phase process, which has ultra-high impact strength.

EXAMPLES

COMPARATIVE EXPERIMENT 1

Three samples of a formulated ethylene vinyl acetate (EVA) sheet (F406S from Hangzhou First Applied Material Co.) were prepared by punching 4 mm diameter holes to assess their suitability as a perforated rear insulator. Each sheet was laminated between two pieces of 3 mm float glass using an SM Innotech Profilam laminator. The lamination process was conducted under the following conditions for samples S1 , S2, and S3: Lamination conditions are given in Table 1.

Sample 1 underwent a full lamination cycle, and upon completion, no holes were visible, indicating that the full material collapsed. Table 1

Sample 2 was laminated for only 240 seconds, and post-lamination inspection revealed the presence of visible holes. A temperature measurement during the lamination process showed that the maximum temperature did not exceed the melting point of the perforated EVA sheet (73°C).

Sample 3 was subjected to a slightly extended lamination time of 270 seconds, during which the temperature reached approximately 80°C. After lamination, all holes had collapsed, suggesting rapid material collapse. This early collapse in the lamination cycle prevents adequate flow and in some cases curing of the conductive contact material, rendering the commercially available perforated EVA sheet unsuitable for use as a rear insulator in back contact cells.

COMPARATIVE EXPERIMENT 2

Three alternative perforated rear insulators were tested for their stability of the holes and their adhesion properties.

Following commercially available rear perforated insulators (RPI's) were evaluated: Sample 4: RPI available from the company Polar Photovoltaics Ltd (Pule New Energy (Bangbu) Co. Ltd.

Sample 5: RPI available from the company Shadong BKC Materials Tech.

Sample 6: RPI available from the company Sun Pacific Power Corp.

The RPI's are multi layer constructions which have a PET (polyethylene terephthalate) core layer and a polyolefin-based (LDPE or EVA) outer layer on both sides of the core layer.

All samples of 4, 5 and 6 where laminated using the same protocol as described in Example 1 with the same lamination conditions of Sample 1 as used in Example 1. From all samples, perforated sheets were laminated between glasses for visual inspection whereby the RPI's were laminated against a copper substrate of the conductive backsheet for peel test evaluation.

The peel strength to the copper layer of the conductive backsheet was determined by performing a 180° peel tests on glass - RPI - conductive backsheet samples with a peel speed of 60 mm/min.

Samples were aged in damp heat conditions and thermal cycling according to the I EC 61215 norm. The residence time in damp heat conditions was 1000 hours and 200 thermal cycles were done.

After the ageing test the peel strength was determined according to the above mentioned test conditions. Below table 2 summarizes the data of the visual inspection and the peel test results after lamination and after ageing. During visual inspection it was verified if the perforated holes did change shape after lamination.

Table 2

In this example it is clear that on one hand the collapse like experienced in example 1 was not taking place and the perforations remained visible. On the other hand, the peel strength of all samples was low. A peel strength value of less than 10 N/cm is regarded as being very low in the industry.

EXAMPLE 1

Multilayers RPI’s were produced using a 3 extruder co-extrusion set-up.

Figure 2 shows how the RPI was constructed. The multilayers were constructed in a symmetrical way as both outer layers were the same, which is also true for the tie layers. The following layer compositions were combined and evaluated:

• Outer layer 1 comprising 25 w% Yparex 0H287 from The Compound Company and 75 w% Queo 8210 from Borealis AG

• Outer layer 2 comprising 25 w% Lotader 4613 from SK Functional Polymer and 75 w% Queo 8210 from Borealis AG

• Outer layer 3 comprising 25 w% Lotader AX8900 from SK Functional Polymer and 75 w% Queo 8210 from Borealis AG

• Tie layer 1 comprising 90 wt% MZA-PP (Mitsui QF551), 10 wt% POE DOW Elite 9107)

• Tie layer 2 comprising Vistamaxx 6202 from Exxon Mobil Corporation.

• Tie layer 3 comprising 50 w% Polypropylene K8003 from Shanghai SECCO Petrochemical Co., Ltd. and 50% POE

• Core layer: comprising Polypropylene K8003 from Shanghai SECCO Petrochemical Co., Ltd.

Table 3 below summarizes the various samples S7-S11 produced, with the approximate layer thickness of each specific layer in micrometers. Perforations were made in all the multilayer samples, which were then laminated following the procedure described in Examples 1 and 2. Both visual samples with punched holes and peel test samples were prepared. After lamination, a visual inspection of the laminates with punched holes was conducted, and peel adhesion strength was determined using the procedure outlined in Example 2. The following results were obtained:

Table 3

The combinations mentioned above resulted in multilayer RPI that, after lamination, maintained the integrity of the punched perforations while demonstrating satisfactory adhesion to both the copper layer and the backsheet. Apparently the composition and thickness of the outer layer and tie layer are determinative for the final adhesion that can be achieved. The results indicate that the combinations listed above are suitable for use as rear perforated insulators in back contact module construction.

Claims

1. Photovoltaic back contact module comprising a co-extruded perforated rear insulator comprising two outer polymer layers and at least one inner polymer layer whereby the inner or core polymer layer has a melting point T 1 above 160 °C while both outer polymer layer(s) have a melting point T2 below 155 °C whereby both outer layers comprise at least a polymer comprising functional groups chosen from acrylate, maleic anhydride, epoxy, silane and/or methacrylate groups.

2. Photovoltaic module according to claim 2 wherein the perforated rear insulator comprises holes.

3. Photovoltaic module according to any one of the claims 1-2 whereby the rear insulator further comprises a tie layer between the outer and the inner or core layer at both sides of the inner layer.

4. Photovoltaic module according to any one of the claims 1-3 wherein the outer polymer layers comprise a functionalized terpolymer and/or a functionalized polyolefin elastomer.

5. Photovoltaic module according to claim 5 wherein the outer polymer layers comprise a maleic-anhydride-(meth)-acrylate functionalized terpolymer and/or a silane functionalized polyolefin elastomer.

6. Photovoltaic module according to any one of the claims 1-5 whereby the outer layers have a thickness in the range of 25-80pm.

7. Photovoltaic module according to any one of the claims 1-6 whereby the inner or core layer comprises one of the polymers chosen from polypropylene, polyethylene terephalate (PET) or polybutylene therephtalate (PBT).

8. Photovoltaic module according to any one of the claims 1-7 whereby the inner layer has a thickness in the range of 40-95pm.

9. Photovoltaic module according to any one of the claims 3-8 whereby the tie layer has a thickness in the range of 1-40pm.

10. Photovoltaic module according to claim 9 whereby the tie layers comprise a polyolefin selected from the group consisting of low density polyethylene, linear low density polyethylene, high density polyethylene and/or a polyolefin elastomer selected from the group consisting of ethylene copolymers with butene, hexene, octene or decene.

11. Photovoltaic module according to any one of the claims 1-10 whereby the module further comprises front glass or polymer glass, an encapsulant layer, a solar cell circuit and a conductive backsheet whereby the rear perforated insulator is positioned between the solar cell circuit and the conductive backsheet.

12. Co-extruded perforated rear insulator comprising two outer polymer layers and at least one inner polymer layer whereby the inner polymer layer has a melting point T1 above a 160 °C while both outer polymer layer(s) have a melting point T2 below 155 °C whereby both outer layers comprise at least a polymer comprising functional groups chosen from acrylates, maleic anhydride, epoxy, silane and/or methacrylate.

13. Co-extruded perforated rear insulator according to claim 12 wherein the outer polymer layers comprise a maleic-anhydride-(meth)-acrylate functionalized terpolymer and/or a silane functionalized polyolefin elastomer.

14. Co-extruded perforated rear insulator according to any one of the claims 12-13 whereby the inner layer comprises one of the polymers chosen from polypropylene, polyethylene terephalate (PET) or polybutylene therephtalate (PBT).

15. Co-extruded perforated rear insulator according to any one of the claims 12-14 further comprising a tie layer comprising a polyolefin selected from the group consisting of low density polyethylene, linear low density polyethylene, high density polyethylene and/or a polyolefin elastomer selected from the group consisting of ethylene copolymers with butene, hexene or octene.