LAYER ELEMENT SUITABLE AS INTEGRATED BACKSHEET ELEMENT OF A PHOTOVOLTAIC MODULE

Abstract

The invention relates to a layer element comprising three layers A, B and C in the configuration A-B-C wherein layers A and B and layers B and C are in adhering contact with each other, an article, preferably a photovoltaic module, comprising said layer element, a process for preparing said layer element, a process for preparing a photovoltaic module comprising said layer element and the use of said layer element as integrated backsheet element of a photovoltaic module.

Claims

1. A layer element, which comprises at least three layers A, B, and C in the configuration A-B-C, wherein layer A comprises a polyethylene composition (PE-A) comprising a copolymer of ethylene, which is selected from a copolymer of ethylene, which bears silane group(s) containing units (PE-A-a); or a copolymer of ethylene with polar comonomer units selected from one or more of (C.sub.1-C.sub.6)-alkyl acrylate or (C.sub.1-C.sub.6)-alkyl (C.sub.1-C.sub.6)-alkylacrylate comonomer units, which additionally bears silane group(s) containing units (PE-A-b), wherein, the copolymer of ethylene (PE-A-a) is different from the copolymer of ethylene (PE-A-b); layer B comprises a polyethylene composition (PE-B) comprising a copolymer of ethylene, which is selected from a copolymer of ethylene and comonomer units selected from one or more of alpha-olefins having from 3 to 12 carbon atoms (PE-B-a), which has a density of from 850 kg/m.sup.3 to 905 kg/m.sup.3; or a copolymer of ethylene and comonomer units selected from one or more of alpha-olefins having from 3 to 12 carbon atoms, which additionally bears silane group(s) containing units (PE-B-b), having a density of from 850 kg/m.sup.3 to 905 kg/m.sup.3; or a copolymer of ethylene and comonomer unit(s) selected from one or more of alpha-olefins having from 3 to 12 carbon atoms, which additionally bears functional group containing units originating from at least one unsaturated carboxylic acid and/or its anhydrides, metal salts, esters, amides or imides and mixtures thereof (PE-B-c), and has a density of from 850 kg/m.sup.3 to 905 kg/m.sup.3; and layer C comprises a polypropylene composition (PP-C) comprising a polymer of propylene (PP-C-a), wherein layers A and B and layers B and C are in adhering contact with each other.

2. The layer element according to claim 1, wherein the polar comonomer units in the copolymer of ethylene (PE-A-b) are selected from (C.sub.1-C.sub.6)-alkyl acrylate comonomer units.

3. The layer element according to claim 1, wherein the silane group(s) containing units of copolymer of ethylene (PE-A-a) or of copolymer of ethylene (PE-A-b) are hydrolysable unsaturated silane compound(s) represented by the formula (I):
R.sup.1SiR.sub.q.sup.2Y.sub.3-q  (I) wherein R.sup.1 is an ethylenically unsaturated hydrocarbyl, hydrocarbyloxy or (meth)acryloxy hydrocarbyl group, each R.sup.2 is independently an aliphatic saturated hydrocarbyl group, Y which may be the same or different, is a hydrolysable organic group and q is 0, 1 or 2.

4. The layer element according to claim 1, wherein the copolymer of ethylene (PE-A-a) and the copolymer of ethylene (PE-A-b) has one or more of the following properties: density of from 920 to 960 kg/m.sup.3; melt flow rate MFR.sub.2 of from less than 20 g/10 min; melting temperature Tm of from 70 to 120° C.; and/or shear thinning index SHI.sub.0.05/300 of from 30.0 to 100.0.

5. The layer element according to claim 1, wherein the copolymer of ethylene (PE-B-a) is a copolymer of ethylene and 1-butene, a copolymer of ethylene and 1-hexene or a copolymer of ethylene and 1-octene; the copolymer of ethylene (PE-B-b) is a copolymer of ethylene and 1-butene, a copolymer of ethylene and 1-hexene or a copolymer of ethylene and 1-octene onto which silane group(s) containing units are grafted; and the copolymer of ethylene (PE-B-c) is a copolymer of ethylene and 1-butene, a copolymer of ethylene and 1-hexene or a copolymer of ethylene and 1-octene onto which functional groups containing units originating from maleic anhydride, acrylic acid, methacrylic acid, crotonic acid, fumaric acid, fumaric acid anhydride, maleic acid, citraconic acid and mixtures thereof are grafted.

6. The layer element according to claim 1, wherein the silane group(s) containing unit(s) of copolymer of ethylene (PE-B-b) is/are hydrolysable unsaturated silane compound(s) represented by the formula (I):
R.sup.1SiR.sub.q.sup.2Y.sub.3-q  (I) wherein R.sup.1 is an ethylenically unsaturated hydrocarbyl, hydrocarbyloxy or (meth)acryloxy hydrocarbyl group, each R.sup.2 is independently an aliphatic saturated hydrocarbyl group, Y which may be the same or different, is a hydrolysable organic group and q is 0, 1 or 2.

7. The layer element according to claim 1, wherein the copolymer of ethylene (PE-B-a), (PE-B-b) or (PE-B-c) has a melt flow rate MFR.sub.2 of less than 20 g/min.

8. The layer element according to claim 1, wherein the polypropylene composition (PP-C) comprises a heterophasic copolymer of propylene, which comprises, a polypropylene matrix component and an elastomeric propylene copolymer component which is dispersed in said polypropylene matrix.

9. The layer element according to claim 8, wherein the heterophasic copolymer of propylene has one or more of the following properties: Melting temperature Tm of at least 145° C.; Vicat softening temperature Vicat A of at least 90° C.; Melt flow rate MFR.sub.2 of 1.0 to 20.0 g/10 min; Xylene cold soluble (XCS) fraction in amount of from 5 to 40 wt %; Comonomer content of 2.0.0 to 20.0 wt %; Flexural modulus of at least 600 MPa; and/or Density of 900 to 910 kg/m.sup.3.

10. The layer element according to claim 1, wherein the thickness ratio of the layers A:B:C in a three-layer element ranges from 45:10:45 to 33.3:33.3:33.3 or the thickness ratio of the layers X A:B:C:Y in a five-layer element ranges from 20:25:10:25:20 to 20:20:20:20:20.

11. The layer element according to claim 1, wherein the layer element has a total thickness of from 325 μm to 2000 μm.

12. An article comprising the layer element according to claim 1, preferably being a photovoltaic module comprising a photovoltaic element and the layer element, wherein the photovoltaic element is in adhering contact with layer A of the layer element, more preferably being a photovoltaic module, which comprises, in the given order, a protective front layer element, a front encapsulation layer element, a photovoltaic element and an integrated backsheet element, wherein the integrated backsheet element comprises, preferably consists of the layer element (LE).

13. A process for producing the layer element according to claim 1 comprising the steps of: adhering the layers A, B and C of the layer element together by extrusion or lamination in the configuration A-B-C; and recovering the formed layer element.

14. A process for producing an article, being a photovoltaic (PV) module according to claim 12 comprising the steps of: assembling the photovoltaic element, the layer element and optional further layer elements to a photovoltaic (PV) module assembly; laminating the layer elements of the photovoltaic (PV) module assembly in elevated temperature to adhere the elements together; and recovering the obtained photovoltaic (PV) module.

15. (canceled)

Description

[0368] FIG. 1 is a schematic picture of a typical PV module of the invention comprising a protective front layer element (1), a front encapsulation layer element (2), a photovoltaic element (3) and the layer element of the invention (combination of (4)+(5)+(6)), showing layers A, B and C, wherein layer A functions as a rear encapsulation layer element (4) and layer C as a protective back layer element (6) with layer B functioning as adhesive layer (5).

PROCESS FOR PREPARING A PHOTOVOLTAIC MODULE

[0369] The invention further provides a process for producing an assembly of the invention wherein the process comprises the steps of: [0370] assembling the layer element of the invention and further layer element(s) to an assembly; [0371] laminating the elements of the assembly in elevated temperature to adhere the elements together; and [0372] recovering the obtained assembly.

[0373] The layer elements can be provided separately to the assembling step. Or, alternatively, part of the layer elements or part of the layers of two layer elements can be adhered together, i.e. integrated, already before providing to the assembling step.

[0374] The preferred process for producing the assembly is a process for producing a photovoltaic (PV) module by [0375] assembling the photovoltaic element, the layer element of the invention and optional further layer elements to a photovoltaic (PV) module assembly; [0376] laminating the layer elements of the photovoltaic (PV) module assembly in elevated temperature to adhere the elements together; and [0377] recovering the obtained photovoltaic (PV) module.

[0378] The conventional conditions and conventional equipment are well known and described in the art of the photovoltaic module and can be chosen by a skilled person.

[0379] As said part of the layer elements can be in integrated form, i.e. two or more of said PV elements can be integrated together, e.g. by lamination, before subjecting to the lamination process of the invention.

[0380] Preferable embodiment of the process for forming the preferable photovoltaic (PV) module of the invention, is a lamination process comprising, [0381] an assembling step to arrange a photovoltaic element and the layer element of the invention to form of a multilayer assembly, wherein layer A of the layer element is arranged in contact with the photovoltaic element, preferably an assembling step to arrange, in a given order, a front protective layer element, a front encapsulating layer element, a photovoltaic element and the layer element of the invention to form of a multilayer assembly, wherein layer A of the layer element is arranged in contact with a photovoltaic element; [0382] a heating step to heat up the formed PV module assembly optionally, and preferably, in a chamber at evacuating conditions; [0383] a pressing step to build and keep pressure on the PV module assembly at the heated conditions for the lamination of the assembly to occur; and [0384] a recovering step to cool and remove the obtained PV module comprising the layer element.

[0385] The lamination process is carried out in laminator equipment, which can be e.g. any conventional laminator which is suitable for the multilaminate to be laminated, e.g. laminators conventionally used in the PV module production. The choice of the laminator is within the skills of a skilled person. Typically, the laminator comprises a chamber wherein the heating, optional, and preferable, evacuation, pressing and recovering (including cooling) steps take place.

[0386] Use

[0387] The use of the layer element according to the invention as defined above or below as an integrated backsheet element of a photovoltaic module comprising a photovoltaic element and said layer element, wherein the photovoltaic element is in adhering contact with layer A of the layer element.

[0388] Thereby, the layer element and the photovoltaic module preferably includes as the properties and definitions of the layer element and the photovoltaic module as described above or below.

[0389] Determination Methods

[0390] Melt Flow Rate: The melt flow rate (MFR) is determined according to ISO 1133 and is indicated in g/10 min. The MFR is an indication of the flowability, and hence the processability, of the polymer. The higher the melt flow rate, the lower the viscosity of the polymer. The MFR.sub.2 of polypropylene is measured at a temperature 230° C. and a load of 2.16 kg. The MFR.sub.2 of polyethylene is measured at a temperature 190° C. and a load of 2.16 kg.

[0391] Density: ISO 1183, measured on compression moulded plaques.

[0392] Comonomer Contents: [0393] The content (wt % and mol %) of polar comonomer present in the copolymer of ethylene (PE-A-b) and the content (wt % and mol %) of silane group(s) containing units present in the copolymers of ethylene (PE-A-a), (PE-A-b) and (PE-B-b) was determined as described in WO 2018/141672 for the content (wt % and mol %) of polar comonomer present in the polymer (a) and the content (wt % and mol %) of silane group(s) containing units (preferably comonomer) present in the polymer (a). [0394] The alpha-olefin comonomer content present in copolymer of ethylene (PE-B-a), (PE-B-b) and (PE-B-c) was determined as described in WO 2019/134904 for the comonomer content quantification of poly(ethylene-co-1-octene) copolymers. [0395] The comonomer content present in propylene polymer (PP-C-a) was determined as described in WO 2017/071847 for the comonomer content measurement.

[0396] Rheological Properties:

[0397] Dynamic Shear Measurements (Frequency Sweep Measurements)

[0398] The rheological properties are measured as described in WO 2018/141672.

[0399] Melting temperature (T.sub.m) and heat of fusion (H.sub.f) were measured as described in WO 2018/141672.

[0400] Xylene cold soluble (XCS) was measured as described in WO 2018/141672.

[0401] Vicat softening temperature was measured according to ASTM D 1525 method A (50° C./h, ION).

[0402] Tensile Modulus: Tensile stress at yield and Tensile strain at break were measured as described in WO 2018/141672.

[0403] Flexural modulus was measured as described in WO 2017/071847.

[0404] Interlayer Adhesion of Co-Extruded Films and Laminates:

[0405] To test the adhesive bond of co-extruded films, double laminates were produced. Two co-extruded films, encapsulant sides facing inside and a Teflon stripe in-between to enable starting point for peeling, were laminated together. The vacuum lamination occurred at 150° C. using a lamination program of 5 minutes evacuation time, followed by 15 minutes pressing time with an upper chamber pressure of 800 mbar.

[0406] Interlayer Adhesion of Co-Extruded/Laminated Sheets:

[0407] The adhesive bond forces of co-extruded/double-laminated sheets were tested on a universal testing machine (Zwick Z010) based on modified methods of ISO 11339. 5 specimens (length: approx. 200 mm/width: 25 mm) were prepared (cut) from each sample in machine direction.

[0408] A teflon stripe was removed, and the separated layers were mounted between two pneumatic clamps and the force required to pull the layers apart and displacement was measured.

[0409] If peeling & yielding occurred parallel, the elongating layer was cut apart, to enable pure peeling between weakest interlayer.

[0410] Average peeling force (unit: N) and type/point of failure were recorded.

[0411] In some cases no peeling occurred, but the co-extruded film only yielded.

[0412] The peeling results were divided into categories: “low” corresponding average peeling forces<ION, “high” for results 30N, and “very high” for results>60N.

[0413] Test Parameters:

[0414] Clamping distance: 10 mm

[0415] Pre-load: 10 N

[0416] Speed pre-load: 50 mm/min

[0417] Pre- & Postmeasurement travel: 20 mm

[0418] Measurement travel (incl. Pre- & Postmeasurement travel): 100 mm

[0419] Test speed: 50 mm/min

[0420] Power Output Measurement

[0421] Current-voltage (IV) characteristics of the 1-cell modules were obtained using a HALM cetisPV-Celltest3 flash tester. Prior to the measurements, the system was calibrated using a reference cell with known IV response. The 1-cell modules were flashed using a 30 ms light pulse from a xenon source. All results from the IV-measurements were automatically converted to standard test conditions (STC) at 25° C. by the software PV Control, available from HALM. Every sample setup was flashed three times on both sides of the bifacial module and given IV parameters are calculated average values of these three individual measurements. All modules were flash tested with a black mask when flashed from the front side. No mask was used when flashed from the rear side. The black mask was made out of standard black coloured paper and had a square-shaped opening of 160*160 mm. During flash test, the black mask was positioned in such way that the solar cell in the solar module was totally exposed to the flash pulse, and that there was 2 mm gap between the solar cell edges and the black mask. The black mask was fixated to the modules by using tape. All IV-characterization were done in accordance with the IEC 60904 series.

[0422] The retained Pmax is determined according to IEC 60904. Pmax is the power that the PV module generates from a flash pulse of 1000 W/m2 at standard test conditions (STC). From the IV-curve generated at the flash test, Pmax is obtained from the equation below where Isc is the short-circuit current, Voc is the open-circuit voltage and FF is the fill factor.

P.sub.max=V.sub.oc*I.sub.sc*FF

[0423] EL imaging

[0424] To the solar mini-module placed in a dark room a current is fed and the emitted light is detected using NIKON D5200 camera with the selected f-number f/5, exposure time 20 sec and ISO speed 3200.

[0425] Damp Heat Test (DH)

[0426] The damp heat (DH) test was performed for the PV minimodules of the invention. The DH test was performed in climate chamber at 85° C. temperature and relative humidity of 85% according to IEC 61215 for 2000 h. Afterwards optical inspection, EL imaging and power output tests were performed to rate the PV minimodules.

[0427] Thermal Cycling Test (TCT) for PV Minimodules

[0428] The PV minimodules were put into Thermal Cycling test. The samples are put into climate chamber between temperatures of −40° C. to 85° C., according to IEC 61215. 50 cycles a week are done following the guidelines given in the standard. In total the mimimodules were treated with 250 cycles in the climate chamber. Afterwards optical inspection, EL imaging and power output tests were performed to rate the PV minimodules.

[0429] Thermal Cycling Test (TCT)

[0430] An additional test program was performed for a backsheet layer alone to evaluate the durability of the composition. 250 μm mono films were produced. Small holes were pressed with cutting tools in MD, TD and in 450 direction to give a starting point for the crack propagation. Afterwards laminates with glass, EVA encapsulant and a monolayer backsheet film of the inventive compositions were produced to evaluate the performance. The samples are put into a climate chamber at temperatures between −40° C. to 85° C., according to IEC 61215. 50 cycles a week are done following the guidelines given in the standard. In total the laminates were treated with 200 cycles in the climate chamber. Afterwards visual inspection was performed to evaluate possible crack propagation.

[0431] Experimental Part

[0432] Preparation of the Polyethylene Compositions (PE-A) for Layer A

[0433] The copolymer of ethylene (PE-A-b) was produced in a commercial high pressure tubular reactor at a pressure 2500-3000 bar and max temperature 250-300° C. using conventional peroxide initiatior. Ethylene monomer, methyl acrylate (MA) polar comonomer and vinyl trimethoxy silane (VTMS) comonomer (silane group(s) containing comonomer) were added to the reactor system in a conventional manner. CTA was used to regulate MFR as well known for a skilled person. After having the information of the property balance desired for the inventive final polymer (a), the skilled person can control the process to obtain the copolymer of ethylene (PE-A-b).

[0434] The amount of the vinyl trimethoxy silane units, VTMS, (=silane group(s) containing units), the amount of MA and MFR.sub.2 are given in the table 1.

[0435] The properties in below tables were measured from the polymer (a) as obtained from the reactor or from a layer sample as indicated below.

TABLE-US-00001 TABLE 1 Properties of copolymer of ethylene (PE-A-b) obtained from the reactor copolymer of ethyene Test polymer (PE-A-b) MFR.sub.2, 16, g/10 min   3.5 Methyl acrylate (MA) content, mol % (wt %) 8.8 (22.5) Melt Temperature, ° C. 91 VTMS content, mol % (wt %) 0.3 (1.4)  Density, kg/m.sup.3 948  SHI (0.05/300), 150° C. 70

[0436] In above table 1 MA denotes the content of methyl acrylate comonomer units present in the polymer and, respectively, VTMS content denotes the content of vinyl trimethoxy silane comonomer units present in the polymer.

[0437] The copolymer of ethylene (PE-A-b) was compounded to produce the polyethylene composition (PE-A) for layer A.

[0438] Polyethylene composition 1 (PE-A-1) consists of the polyethylene composition (PE-A-b) described above.

[0439] Polyethylene composition 1 (PE-A-2) consists of 90 wt % of the polyethylene composition (PE-A-b) described above and 10 wt % of a TiO.sub.2 masterbatch, which includes 65 wt % of TiO.sub.2.

[0440] Preparation of the Polyethylene Compositions (PE-B) for Layer B

[0441] Polyethylene composition 1 (PE-B-1) consists of Queo7007LA, which is an ethylene-based plastomer with 1-octene comonomer units having a melt flow rate MFR.sub.2 (190° C., 2.16 kg) of 6.5 g/10 min and a density of 870 kg/m.sup.3 (including stabilizers), commercially available from Borealis AG.

[0442] Polyethylene composition 2 (PE-B-2) consists of Queo7007LA, which is grafted with 1 wt % vinyl trimethoxy silane units (VTMS). The grafting is performed as described in the example section of WO 2019/201934.

[0443] Polyethylene composition 3 (PE-B-3) consists of Queo7001LA, which is an ethylene-based plastomer with 1-octene comonomer units having a melt flow rate MFR.sub.2 (190° C., 2.16 kg) of 1.0 g/10 min and a density of 870 kg/m.sup.3 (including stabilizers), commercially available from Borealis AG.

[0444] Preparation of the Polypropylene Compositions (PE-C) for Layer C

[0445] For polypropylene composition (PP-C-1) the composition as described in example IE6 of WO 2017/071847 has been used.

[0446] The polypropylene composition thus includes [0447] 40.7 wt % heterophasic propylene copolymer B, [0448] 27.2 wt % heterophasic propylene copolymer A,
(both prepared as described in the example section of WO 2017/071847) [0449] 23 wt % talc, [0450] 8 wt % Queo 8230, supplier Borealis, is an ethylene based octene plastomer, produced in a solution polymerisation process using a metallocene catalyst, MFR.sub.2 (190° C.) of 30 g/10 min and density of 882 kg/m.sup.3, and [0451] 1.1 wt % additives as described in the example section of WO 2017/071847.

[0452] For polypropylene composition (PP-C-2), in addition to the additives added for polypropylene composition (PP-C-1) the following pigments were added during the melt homogenisation step: [0453] 7 wt % of a TiO.sub.2 masterbatch, which includes 70 wt % of TiO.sub.2.

[0454] The polypropylene composition (PP-C-1) has the following properties as listed in Table 3. The tensile properties tensile modulus, tensile strength and tensile strain at break were measured using a 200 μm monolayer cast film in MD direction.

TABLE-US-00002 TABLE 3 Properties of the polypropylene composition (PP-C-1) PP-C-1 MFR [g/10 min] 5.5 XCS [wt %] 23 Tensile modulus, MD [MPa] 1408 Tensile strength [MPa] 26 Tensile strain at break [%] 956

[0455] Since polypropylene composition (PP-C-2) only differs from (PP-C-1) in the presence of a TiO.sub.2 masterbatch the same properties as for (PP-C-1) are to be expected.

[0456] Preparation of the Layer Elements

[0457] Layer A was produced from the polyethylene compositions (PE-A-1) and (PE-A-2).

[0458] Layer B was produced from the polyethylene compositions (PE-B-1), (PE-B-2) and (PE-B-3). Layer C was produced from the polypropylene compositions (PP-C-1) and (PP-C-2).

[0459] 3-layer calendar films for the inventive layer elements of examples IE1-IE5 and one 2-layer cast film for the comparative layer element of comparative example CE1 were prepared on a Dr. Collin cast film line consisting of 3 automatically controlled extruders, a chill roll unit, a take-off unit with a cutting station and three winders to wrap the film and edge strips.

[0460] Each layer was extruded with an individual extruder: Two outer layers (layer A and layer C) were extruded with extruders equipped with 25 mm screw with LD of 30.

[0461] The core layer (layer B) was extruded with extruder equipped with 30 mm screw with LD of 30. The thickness of each layer A and B was 225 μm and for each layer C was 250 μm resulting in a film thickness of the inventive examples IE1-IE5 of 700 μm and a film thickness of the comparative example CE1 of 475 μm.

[0462] The layer A were extruded onto the embossed side of the calendar-unit and the layers C were extruded onto the smooth side of the calendar-unit with the layers B, were present, sandwiched by layers A and C. The die is fixed at an angle of 900 to the extruders and extrude onto the chill roll. The melt will be extruded between a roll gap of two steel rolls, which is pre-adjusted by a feeler gauge to a gap of ˜600 micron before starting up the line. One roll is textured with a pyramid embossing structure (layer A side) and the other one is polished standard chill roll (Layer C side). The rolls are pressed against each other with a hydraulic pressure of 75 bar to transfer the structure to the film. The chill roll is cooled to 25° C. The melt temperature was 140-190° C. for polyethylene compositions (PE-A) and (PE-B) and 210-215° C. for the polypropylene compositions PP-C. Each extruder was run at a throughput of 5˜20 kg/h. The die width is 300 mm.

[0463] The following layer elements were coextruded as listed in Table 4:

TABLE-US-00003 TABLE 4 Coextruded layer elements Layer A Layer B Layer C CE1 PE-A-1 — PP-C-1 IE1 PE-A-1 PE-B-1 PP-C-1 IE2 PE-A-1 PE-B-2 PP-C-1 IE3 PE-A-1 PE-B-3 PP-C-1 IE4 PE-A-2 PE-B-1 PP-C-1 IE5 PE-A-2 PE-B-1 PP-C-2

[0464] Preparation of Laminates

[0465] A double laminate of each example layer element LE were produced: LE/LE, with layers A facing each other and Teflon stripe at one end of the laminate, to give the starting point for the following peeling test. A type of T-peeling tests were performed on 25 mm wide stripes, with 10 N pre-load and 50 mm/min test speed. Results are reported in Table 5 below. Average peeling force, F.sub.AVG were reported in following way: “Low” values being <ION compares to peeling by hand (weak), and “High” corresponding values>30N, and “very high” corresponding values>60N are considered as strong adhesion. If no result was given, no peeling was observed.

TABLE-US-00004 TABLE 5 T-peeling test results on IBS double laminates before and after 1000 h DH. F.sub.AVG Peeling behaviour Laminate F.sub.AVG Peeling behavior (after 1000 h DH) (after 1000 h DH) CE1 Low between layers A and C Low between layers A and C IE1 — yielding of laminate Very high mixed through all layers IE2 Very high between layers B and C High mixed through all layers IE3 Very high between layers B and C Very high between layers A and B IE4 — yielding of laminate Very high between layers A and B IE5 High between layers B and C High mixed through all layers

[0466] Preparation of PV Minimodules

[0467] For the PV modules comprising the layer elements as described above as integrated backsheet elements 300 mm×200 mm laminates consisting of

[0468] Glass/Encapsulant/Cell with connectors/layer element as described above were prepared using a PEnergy L036LAB vacuum laminator.

[0469] Glass layer, structured solar glass, low iron glass, supplied by InterFloat, length: 300 mm and width: 200 mm, total thickness of 3.2 mm.

[0470] The front protective glass element was cleaned with isopropanol before putting the first encapsulation layer element film on the solar glass. The front encapsulation layer element was cut in the same dimension as the solar glass element. After the front encapsulation layer element was put on the front protective glass element, then the soldered solar cell was put on the front encapsulation layer element. Further the layer element of the invention was put on the obtained PV cell element. The obtained PV module assembly was then subjected to a lamination process as described below.

TABLE-US-00005 TABLE 6 Lamination settings for photovoltaic modules Pressure Pressure holding Total Pressure, build-up substep of time of Temperature, mbar Heating Evacuation of pressing pressing steps (i) ° C. (step (iv) (i), s (ii), s step (iii), s step (iv), s to (iv), s 150 800 0 300 10 900 1210

[0471] As front encapsulants the following compositions were used:

[0472] EVA: (Hangzhou EVA F406P): ethyl vinylacetate with 28% vinylacetate and MFR.sub.2=ca. 35 g/10 min

[0473] PE-A-b: (0.45 mm thick): ethylene terpolymer with methylacrlyate comonomer units and vinyltrimethoxysilane comonomer units, i.e. 22.5 wt % MA, 1.4% VTMS and MFR.sub.2=2.5-3.5 g/10 min, including UV-stabilising hindered amine compound (CAS number 65447-77-0).

[0474] The same type of structured solar glass having a thickness of 3.2 mm (Ducat) was used for all cells.

[0475] The cell used was a P-type mono crystalline silica cell with three buss-bars and having a dimension of 156×156×0.2 mm and with a cell efficiency of 17.80%. The cell was supplied by ITS with a part number of ITS2-02-60MS3B200C-1780B. The composition of the soldering wire was Sn:Pb:Ag (62:36:2).

[0476] The vacuum lamination occurred at 150° C. using a lamination program of 5 minutes evacuation time, followed by 15 minutes pressing time with an upper chamber pressure of 800 mbar.

[0477] The power output (front flash only) for the produced PV modules was tested before and after ageing tests (2000 h DH as well as 2000 h DH+250 cycles TCT) and reported in Table 6. The related power loss after each ageing test is reported in brackets next to power output. The results for visual inspection and EL imaging after ageing test for these minimodules are reported in Table 7.

TABLE-US-00006 TABLE 7 Power output and power losses on modules before and after DH and TCT ageing tests. Mini Module Pmax, Watt components Pmax, Watt Pmax, Watt 2000 h DH + extra Encapsulant - LE 0 h DH 2000 h DH 250 cycles TCT PE-A-b - CE1 4.10 4.04 (1.46)* 3.92 (4.39)* PE-A-b - IE1 4.06 4.06 (0.00)* 3.79 (6.65)* PE-A-b - IE2 4.05 4.04 (0.25)* 3.88 (4.20)* PE-A-b - IE3 4.08 4.07 (0.25)* 3.96 (2.94)* PE-A-b - IE4 4.12 4.11 (0.24)* 3.97 (3.64)* PE-A-b - IE5 4.13 4.13 (0.00)* 3.98 (3.63)* EVA - CE1 4.08 4.06 (0.49)* 3.88 (4.90)* EVA - IE1 4.07  4.08 (−0.25)* 3.76 (7.62)* EVA - IE2 4.10 4.10 (0.00)* 3.89 (5.12)* EVA - IE3 4.09 4.08 (0.24)* 3.72 (9.05)* EVA - IE4 4.14 4.12 (0.48)* 3.97 (4.11)* EVA - IE5 4.17 4.15 (0.48)* 3.82 (8.39)* *power loss in % compared to original value.

TABLE-US-00007 TABLE 8 Visual inspection (also with EL images) on modules after ageing Mini Module Changes on modules after ageing for components 2000 hrs DH and 250 cycles** in TCT Encapsulant - IBS Delamination Defects PE-A-b - CE1 minor no PE-A-b - IE1 minor, on edges of Very minor the module PE-A-b - IE2 no no PE-A-b - IE3 no no PE-A-b - IE4 no no PE-A-b - IE5 no no EVA - CE1 no minor EVA - IE1 no Several defects EVA - IE2 no minor EVA - IE3 no Several defects EVA - IE4 yes, outside the cell several defects, even area if less visible in EL EVA - IE5 yes, under the cell Several defects and outside the cell

[0478] Backsheet Durability Test Program

[0479] An additional test program was performed for a backsheet layer alone to evaluate the durability of the composition at a critical TCT test. Compounds with different compositions were compared against PP-C-1, which has already earlier been rated good at TCT test. 250 μm mono backsheet films of each composition were produced on Dr Collin line setup similar to above using only one extruder and no surface embossing (melt temperatures 210-215° C., chill roll temperature 25° C.). Small holes were pressed with cutting tools in MD, TD and in 450 direction to give a starting point for the crack propagation. Afterwards laminates with glass, EVA encapsulant (same as above) and a monolayer backsheet film of the inventive compositions below were produced to evaluate the performance in TCT test. The same lamination conditions were used as described above. Visual inspection was made after 200 cycles TCT test. Reference PP-C-1 sample was rated good (++) showing cracks in most critical corners, but crack propagation less than 2 mm long, samples with even less cracks were rated very good (+++), samples with slightly more cracks, were rated ok (+)

[0480] In below table 9, the different test compositions are presented (in wt %) and the result evaluation after 200 cycles thermal cycling test.

TABLE-US-00008 TABLE 9 PP-C layer compositions (wt %) and TCT test performance. PP-C-1 PP-C-3 PP-C-4 PP-C-5 Heterophasic copolymer A 27.2 28.5   63.6 32.5 Heterophasic copolymer B 40.7 42 — 45 Talc 23 10 10 10 Queo 8230 8 9 — 7 Queo 6800 — — 16 — Additives 1.1 1.1   1.1 1.1 TiO.sub.2 masterbatch 10 10 7 TCT test performance (200 cycles) ++ + +++ +++

[0481] Heterophasic copolymer A, as described above on page 52

[0482] Heterophasic copolymer B, as described above on page 52 both prepared as described in the example section of WO 2017/071847

[0483] Queo 8230 is a copolymer of ethylene and 1-octene (MFR.sub.2 190° C. determined according to ISO 1133=30.0 g/10 min, density determined according to ISO 1183-1/A=883 kg/m.sup.3) commercially available from Borealis (AT).

[0484] Queo 6800LA is a copolymer of ethylene and 1-octene (MFR.sub.2 190° C. determined according to ISO 1133=0.5 g/10 min, density determined according to ISO 1183-1/A=868 kg/m.sup.3) commercially available from Borealis (AT).