JP5985803B2 - Solar cell with back sheet - Google Patents

Description

The present invention relates to a solar cell with a back sheet in which a solar cell back sheet is installed on the back side of the solar cell .

  In general, the back surface of a solar cell such as a crystalline silicon solar cell, an organic thin film solar cell, or a dye-sensitized solar cell is covered with the back surface in order to prevent external moisture from entering the cells constituting the solar cell. A backsheet is provided for protection.

  As such a back sheet, for example, a laminate for a solar cell back surface protective material described in Patent Document 1 below is known. The following Patent Document 1 discloses a solar cell back surface protective material in which an ultra high molecular weight polyethylene layer made of ultra high molecular weight polyethylene, a barrier layer made of aluminum foil, and a weather resistant substrate made of polyester resin such as PET are laminated in this order. A laminate is disclosed.

JP 2010-109239 A

  By the way, the backsheet generally requires excellent voltage resistance.

  However, the laminated body for solar cell back surface protective materials described in Patent Document 1 described above has the following problems.

  That is, a polyester resin having a low voltage resistance is used as a weather-resistant substrate laminated on the barrier layer. Here, to increase the voltage resistance, it is conceivable to increase the thickness of the weather-resistant substrate. However, in this case, separation may occur between the barrier layer and the weather resistant substrate under a high temperature environment, and discharge may occur in the gap formed between the barrier layer and the weather resistant substrate. This discharge may reduce the photoelectric conversion characteristics of the solar cell.

  Therefore, there has been a demand for a solar cell backsheet that has excellent voltage resistance and can sufficiently suppress delamination even in a high temperature environment.

The present invention has been made in view of the above circumstances, and has a back sheet having a solar cell back sheet that can sufficiently suppress delamination even in a high temperature environment while having excellent voltage resistance. An object is to provide a solar cell .

  In the laminate for solar cell back surface protective material of Patent Document 1, the present inventor peels between the barrier layer and the weather resistant substrate when the thickness of the weather resistant substrate is increased in a high temperature environment. The cause was examined. As a result, the present inventor thought that the following may be the cause. That is, first, the back surface of the solar cell has an uneven shape by providing wiring or arranging a plurality of cells at a predetermined interval. For this reason, the barrier layer is deformed following the unevenness generated on the back surface of the solar cell, and the weather-resistant substrate is also deformed following the deformation of the barrier layer. At this time, if the thickness of the weather resistant substrate is increased, it becomes difficult to maintain the state following the shape of the barrier layer even if the weather resistant substrate. As a result, the present inventor considered that the weather-resistant substrate may be easily peeled off from the barrier layer. In addition, since the back sheet is usually installed in the solar cell in an exposed state, sunlight may be reflected and reflected on the back sheet after being incident on an object around the solar cell. In some cases, the weather resistant substrate may become hot. In this case, it is difficult for the weather resistant substrate to maintain a state following the shape of the barrier layer without increasing the thickness of the weather resistant substrate. As a result, the present inventor considered that the weather-resistant substrate may be easily peeled off from the barrier layer. Thus, as a result of further earnest studies, the present inventor has found that the above problem can be solved by laminating a cross-linked resin layer containing a cross-linked polyolefin on the metal layer, and has completed the present invention.

That is, the present invention relates to a solar cell with a back sheet, comprising: a solar cell having a light incident surface; and a solar cell back sheet that covers and protects a back surface of the solar cell opposite to the light incident surface. A solar cell backsheet includes a metal layer, a cross-linked resin layer laminated on the metal layer, and a weather-resistant layer provided so as to sandwich the cross-linked resin layer together with the metal layer, and the metal layer comprises aluminum. formed of a metal material containing the cross-linked resin layer comprises a crosslinked polyolefin, the back sheet for the solar cell, the metal layer, wherein the crosslinked resin layer and the weather-resistant layer is disposed in this order from the solar cell side The back surface of the solar cell has an uneven shape, the metal layer is deformed following the uneven shape of the back surface, and the crosslinked resin layer follows the shape of the metal layer. Has the form, the crosslinked polyolefin is a backsheet with a solar cell is cross-linked polyethylene.

According to this solar cell with a back sheet, when the back surface of the solar cell has an uneven shape, the metal layer of the back sheet deforms following the shape, and the crosslinked resin layer laminated on the metal layer also Deforms following the shape of the metal layer. At this time, the cross-linked resin layer containing the cross-linked polyolefin has high voltage resistance, and thus can be thinned while having excellent voltage resistance. For this reason, the crosslinked resin layer can maintain a state following the shape of the metal layer. In addition, the backsheet may receive light from sunlight reflection, and the crosslinked resin layer may become high temperature. Even in this case, in the solar cell with a back sheet of the present invention, since the crosslinked resin layer contains a crosslinked polyolefin and has a high melting point, the state following the shape of the metal layer can be maintained. Therefore, according to the solar cell with a back sheet of the present invention, the back sheet can sufficiently suppress delamination even in a high temperature environment while exhibiting excellent voltage resistance. Moreover, even if the light by the reflection of sunlight enters the back sheet from the weather resistant layer side, the incident intensity of the light to the crosslinked resin layer is weakened by the weather resistant layer. For this reason, compared with the case where the weather resistant layer is not provided, the cross-linked resin layer is less likely to be at a high temperature, and the shape of the cross-linked resin layer is easily maintained. As a result, peeling of the crosslinked resin layer from the metal layer is more sufficiently suppressed. In addition, the cross-linked polyolefin is less expensive than the case where the cross-linked polyolefin is other than cross-linked polyethylene, and appropriate flexibility can be maintained in the solar cell backsheet.

In the solar cell with a back sheet, it is preferable that the weather-resistant layer contains a thermoplastic resin.

  In this case, compared with the case where a weather-resistant layer does not contain a thermoplastic resin, adhesiveness with a crosslinked resin layer can be improved more.

In the solar cell with a back sheet, it is preferable that the weather resistant layer further contains carbon.

In this case, even if the incident light by the glare of sunlight from the weather-resistant layer side bar Kkushito, as compared with a case where weather resistance layer does not further contain carbon, more fully suppress the deterioration of the backsheet by ultraviolet irradiation And the occurrence of cracks in the backsheet can be more sufficiently suppressed.

The solar cell with a backsheet preferably further includes a thermoplastic resin layer provided so as to sandwich the metal layer together with the crosslinked resin layer.

  In this case, even if the back surface of the solar cell has an uneven shape by the thermoplastic resin, the back surface and the metal layer can be bonded.

In the solar cell with a back sheet, it is preferable that the crosslinked resin layer is directly bonded to the metal layer.

  In this case, compared with the case where the crosslinked resin layer and the metal layer are bonded via an adhesive, the adhesive is less likely to deteriorate even in a high temperature and high humidity environment. Can be sufficiently suppressed.

ADVANTAGE OF THE INVENTION According to this invention, the solar cell with a back sheet which has the back sheet for solar cells which can fully suppress delamination also in a high temperature environment, having excellent voltage resistance is provided.

It is a fragmentary sectional view which shows the solar cell with a back sheet which applied one Embodiment of the back sheet for solar cells which concerns on this invention. It is a fragmentary sectional view which shows the back seat | sheet of FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 and 2. FIG. 1 is a partial cross-sectional view showing a solar cell with a back sheet to which an embodiment of the solar cell back sheet according to the present invention is applied, and FIG. 2 is a partial cross-sectional view showing the back sheet of FIG.

  The solar cell with a back sheet shown in FIG. 1 is a dye-sensitized solar cell 300 with a back sheet, and includes a dye-sensitized solar cell 100 and a back sheet 200 that covers and protects the back surface 100b of the dye-sensitized solar cell 100. ing.

  As shown in FIG. 1, the dye-sensitized solar cell 100 includes a transparent common substrate 10 that functions as a light incident side substrate, and a plurality of (two in FIG. 1) solar cells 20 provided on the common substrate 10. It has. Each solar cell 20 includes a transparent conductive film 21 provided on the common substrate 10, a porous oxide semiconductor layer 22 provided on the transparent conductive film 21, and a counter electrode disposed to face the porous oxide semiconductor layer 22. 23, a sealing portion 24 that connects the counter electrode 23 and the common substrate 10, and an electrolyte 25 that fills a cell space surrounded by the common substrate 10, the counter electrode 23, and the sealing portion 24. In FIG. 1, the surface 100a on the opposite side of the solar cell 20 in the common substrate 10 is a light incident surface. Since the solar cell 20 is provided on the common substrate 10, the back surface 100 b has an uneven shape.

  On the other hand, as shown in FIG. 2, the solar cell backsheet 200 includes a metal layer 30 and a crosslinked resin layer 40 laminated on the metal layer 30. Here, the crosslinked resin layer 40 is directly bonded to the metal layer 30. The back sheet 200 further includes a thermoplastic resin layer 50 provided so as to sandwich the metal layer 30 together with the crosslinked resin layer 40, and a weather resistant layer 60 provided so as to sandwich the crosslinked resin layer 40 together with the metal layer 30. ing.

  The thermoplastic resin layer 50 is for bonding the metal layer 30 and the back surface 100 b of the dye-sensitized solar cell 100, and the metal layer 30 is water vapor that enters the solar battery cell 60 of the dye-sensitized solar cell 100. It is for cutting off. The weather-resistant layer 60 is a layer provided on the outermost side with respect to the dye-sensitized solar cell 100, and is for suppressing deterioration of the crosslinked resin layer 40 and the thermoplastic resin layer 50 due to the reflected light of sunlight. . The weathering layer 60 is directed to the side opposite to the dye-sensitized solar cell 100. The crosslinked resin layer 40 is for bonding the metal layer 30 and the weather resistant layer 60 together.

  The metal layer 30 is made of a metal material containing aluminum, and the crosslinked resin layer 40 contains a crosslinked polyolefin.

  Here, the back surface 100b of the dye-sensitized solar cell 100 has an uneven shape as described above. Therefore, in the backsheet 200, the thermoplastic resin layer 50 and the metal layer 30 are deformed following the shape of the back surface 100b of the dye-sensitized solar cell 100, and the crosslinked resin layer 40 also follows the shape of the metal layer 30. Is deformed. At this time, according to the backsheet 200, since the crosslinked resin layer 40 containing the crosslinked polyolefin has high voltage resistance, the crosslinked resin layer 40 can be thinned while having excellent voltage resistance. For this reason, the crosslinked resin layer 40 can maintain a state following the shape of the metal layer 30. In addition, the backsheet 200 may receive light due to sunlight reflection, and the crosslinked resin layer 40 may become high temperature. Even in this case, in the backsheet 200, the crosslinked resin layer 40 includes a crosslinked polyolefin and has a high melting point, so that the crosslinked resin layer 40 can maintain a state following the shape of the metal layer 30. Therefore, according to the backsheet 200, delamination can be sufficiently suppressed even in a high temperature environment while exhibiting excellent voltage resistance.

  In the back sheet 200, a weather resistant layer 60 is provided so as to sandwich the cross-linked resin layer 40 together with the metal layer 30. For this reason, even if the light by the reflection of sunlight enters the back sheet 200 from the weather resistant layer 60 side, the incident intensity of the light on the crosslinked resin layer 40 is weakened by the weather resistant layer 60. For this reason, compared with the case where the weather resistant layer 60 is not provided, the cross-linked resin layer 40 is less likely to be at a high temperature, and the shape of the cross-linked resin layer 40 is easily maintained. As a result, peeling of the crosslinked resin layer 40 from the metal layer 30 is more sufficiently suppressed.

  Furthermore, since the backsheet 200 includes the thermoplastic resin layer 50 provided so as to sandwich the metal layer 30 together with the cross-linked resin layer 40, even if the back surface 100b of the dye-sensitized solar cell 100 has an uneven shape due to the thermoplastic resin, The back surface 100b and the metal layer 30 can be adhered.

  Further, in the backsheet 200, since the crosslinked resin layer 40 is directly bonded to the metal layer 30, a high temperature and high humidity environment is compared with the case where the crosslinked resin layer 40 and the metal layer 30 are bonded via an adhesive. Even underneath, it is difficult for the adhesive to deteriorate, so that the peeling between the crosslinked resin layer 40 and the metal layer 30 can be sufficiently suppressed.

  Next, the metal layer 30, the cross-linked resin layer 40, the thermoplastic resin layer 50, and the weather resistant layer 60 that constitute the back sheet 200 will be described in detail.

(Metal layer)
The metal layer 30 should just be comprised with the metal material containing aluminum. The metal material is usually composed of aluminum alone, but may be an alloy of aluminum and another metal. Examples of other metals include copper, manganese, zinc, magnesium, lead, and bismuth. Specifically, 1000 series aluminum obtained by adding a trace amount of other metals to 98% or more pure aluminum is desirable. This is because the 1000 series aluminum is cheaper and more workable than other aluminum alloys.

  The thickness of the metal layer 30 is preferably 1 to 50 μm, more preferably 6 to 25 μm. When the thickness of the metal layer 30 is within the above range, pinholes are less likely to be formed than when the thickness is less than 1 μm, and water vapor can be blocked more effectively. Moreover, when the thickness of the metal layer 30 is within the above range, it is easier to follow the shape of the back surface 100b of the dye-sensitized solar cell 100 than when the thickness exceeds 50 μm, and the amount of material used can be reduced. Cost can be reduced. However, the pinhole is generated with a certain probability when it is thinly rolled with mineral oil used in the step of rolling the aluminum foil. Therefore, in the future, when the appearance probability of pinholes is sufficiently lowered due to technical progress in the rolling process, the lower limit of the thickness of the metal layer 30 may be less than 1 μm.

(Crosslinked resin layer)
The crosslinked resin layer 40 only needs to contain a crosslinked polyolefin. The cross-linked polyolefin is a cross-linked polyolefin. Examples of the polyolefin include polyethylene, polypropylene, and polybutylene. Among these, polyethylene is preferable. In this case, the crosslinked polyolefin is a crosslinked polyethylene. Thus, when the cross-linked polyolefin is a cross-linked polyethylene, the cost is lower than when the cross-linked polyolefin is other than the cross-linked polyethylene, and appropriate flexibility in the backsheet 200 can be maintained. The polyethylene may be linear polyethylene, low-density polyethylene (LDPE), high-density polyethylene, or a silane-modified product thereof, and low-density polyethylene is particularly preferable. In this case, the crosslinked polyolefin is a crosslinked low density polyethylene. This low density polyethylene can realize a crosslinked resin layer 40 having excellent heat distortion resistance as compared with high density polyethylene, and the shape of the crosslinked resin layer 40 can be stably maintained even in a high temperature environment.

The gel fraction of the crosslinked resin layer 40 is preferably 10% or more, more preferably 40% or more. When the gel fraction is within the above range, the cross-linked resin layer 40 has more excellent heat distortion resistance than when the gel fraction is less than 10%. However, the crosslinked resin layer 40 is one of the layers constituting the back sheet 200. For this reason, the crosslinked resin layer 40 is required to have a minimum flexibility such that no cracks are generated during the construction of the backsheet 200 or when stress is applied to the backsheet 200. When this minimum flexibility is defined using the gel fraction as an index, the gel fraction is preferably 60% or less. Here, the “gel fraction” refers to the mass fraction of the solid before and after immersing the crosslinked resin layer 40 in xylene at 120 ° C. for 20 hours, and is specifically defined by the following formula.
Gel fraction (%) = 100 × (mass of solid after immersion / mass of solid before immersion)

  The content of the crosslinked polyolefin contained in the crosslinked resin layer 40 is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, and still more preferably 100% by mass. Here, the content of the cross-linked polyolefin being less than 100% by mass means that the cross-linked polyolefin and other resins form a so-called sea-island structure. The content of the cross-linked polyolefin in the cross-linked resin layer 40 is such that when the material constituting the cross-linked resin layer 40 is 100% by mass and the cross-link density is x%, the content of the cross-linked polyolefin is x% by mass. . For example, in the crosslinked resin layer 40, when crosslinked polyethylene and uncrosslinked polyethylene are uniformly contained in a ratio of 50:50, the crosslinking density is 50% (the gel fraction is about 50%). The content of crosslinked polyethylene is 50% by mass.

  The thickness of the crosslinked resin layer 40 is preferably 20 to 300 μm. The thickness varies depending on the breakdown voltage (required breakdown voltage) required for the backsheet 200. When the required breakdown voltage is less than 100V, a thickness of about 20 to 100 μm is preferable, and the required breakdown voltage exceeds 800V. In such a case, a thickness of 150 to 300 μm is preferable. When the thickness of the crosslinked resin layer 40 is within the above range, there is an advantage that it can withstand the required breakdown voltage unlike the case where the thickness is less than 20 μm. When the thickness of the cross-linked resin layer 40 is within the above range, the cross-linked resin layer 40 can easily follow the shape of the back surface 100b of the dye-sensitized solar cell 100 as compared with the case where the thickness exceeds 300 μm. The peeling of the crosslinked resin layer 40 is more sufficiently suppressed.

(Thermoplastic resin layer)
The thermoplastic resin layer 50 only needs to contain a thermoplastic resin. Examples of such a thermoplastic resin include ionomer, ethylene-methacrylic acid copolymer, maleic anhydride-modified polyethylene, and ethylene-acrylic acid copolymer. Examples include acid-modified polyolefin-based thermoplastic resins such as coalescence.

  The thickness of the thermoplastic resin layer 50 is preferably 20 to 100 μm, more preferably 30 to 80 μm. When the thickness of the thermoplastic resin layer 50 is within the above range, stronger adhesiveness can be maintained between the metal layer 30 and the dye-sensitized solar cell 100 than when the thickness is less than 20 μm. Further, when the thickness of the thermoplastic resin layer 50 is within the above range, the thermoplastic resin layer 50 is more excellent in thermal stability than the case where it exceeds 100 μm, and the entire structure due to the deformation of the thermoplastic resin. Is sufficiently suppressed.

(Weather-resistant layer)
The weather resistant layer 60 is made of a weather resistant material. The weather-resistant material preferably contains a thermoplastic resin. In this case, compared with the case where the weather resistant layer 60 does not contain a thermoplastic resin, the adhesiveness with the crosslinked resin layer 40 can be further improved. Examples of the thermoplastic resin include polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN), and polyolefins such as polyethylene and polypropylene.

  The weather resistant layer 60 preferably further contains carbon in addition to the thermoplastic resin. In this case, compared with the case where the weather-resistant layer 60 does not contain carbon, the deterioration of the back sheet 200 due to ultraviolet rays can be sufficiently suppressed, and the occurrence of cracks in the back sheet 200 can be more sufficiently suppressed.

  Examples of the carbon include fibrous carbon nanotubes and particulate carbon black.

  The average particle diameter of carbon is not particularly limited, but is preferably 3 to 1000 nm, and more preferably 10 to 500 nm.

  The carbon content in the weather resistant layer 60 is preferably 0.5% by mass or more, and more preferably 1% by mass or more. However, the content of carbon in the weather resistant layer 60 is preferably 20% by mass or less from the viewpoint of appropriately imparting the weather resistant layer 60 with adhesiveness to the crosslinked resin layer 40.

  In addition, when the weather resistant layer 60 does not contain carbon, the content rate of the thermoplastic resin in the weather resistant layer 60 is preferably 100% by mass.

  Next, an example of a method for manufacturing the backsheet 200 will be described.

  First, a multilayer film of the crosslinked resin layer 40 and the weather resistant layer 60 is formed. The method of forming the multilayer film includes, for example, a step of forming an uncrosslinked multilayer film of the precursor of the crosslinked resin layer 40 and the weather resistant layer 60, and a crosslinking of the precursor of the crosslinked resin layer 40 in the uncrosslinked multilayer film. And a step of causing. As a method for forming the multilayer film, for example, a coextrusion method such as an inflation method or a casting method is used. Among the coextrusion methods, the cast method is preferably used. This is because the casting method can accurately control the thickness of the crosslinked resin layer 40 and the weather resistant layer 60. In the casting method, the multilayer film is formed by extruding a melt of polyolefin pellets and a melt of weather resistant material constituting the weather resistant layer 60 together from the gaps of the T-die.

  Examples of the crosslinking method of the precursor of the crosslinked resin layer 40 include a chemical crosslinking method and a physical crosslinking method. Examples of the chemical crosslinking method include a peroxide crosslinking method and a silane crosslinking method.

  The peroxide crosslinking method is a method in which polyolefin pellets are introduced into an extruder together with a peroxide (crosslinking agent), and the polyolefin is crosslinked with the peroxide while being extruded. On the other hand, the silane crosslinking method is a method in which silane-modified polyolefin is crosslinked by hot water treatment after extrusion molding of silane-modified polyolefin pellets.

  When a physical crosslinking method using radiation is used as the crosslinking method, the polyolefin constituting the precursor of the crosslinked resin layer 40 is preferably polyethylene. In this case, the crosslinked resin layer 40 can be easily manufactured as compared with the case where the polyolefin constituting the precursor of the crosslinked resin layer 40 is other than polyethylene. In addition, moderate flexibility can be maintained in the crosslinked resin layer 40. This is because when polyethylene is cross-linked by radiation, the cross-linking reaction mainly proceeds, whereas in polypropylene, for example, the molecular cutting reaction proceeds in addition to the cross-linking reaction.

  Next, the metal layer 30 is prepared. And this metal layer 30 and the said multilayer film are laminated | stacked. Examples of a method for laminating the metal layer 30 and the multilayer film include a dry laminating method.

  Finally, the thermoplastic resin layer 50 is thermocompression bonded to the metal layer 30. Thus, the back sheet 200 is obtained.

  The present invention is not limited to the above embodiment. For example, in the above embodiment, the back sheet 200 has the thermoplastic resin layer 50, but the thermoplastic resin layer 50 is not necessarily required and can be omitted.

  Moreover, in the said embodiment, although the back sheet 200 has the weather resistant layer 60, the weather resistant layer 60 is not necessarily required and can be abbreviate | omitted.

  Furthermore, in the said embodiment, although the crosslinked resin layer 40 was directly adhere | attached on the metal layer 30, the crosslinked resin layer 40 may be adhere | attached on the metal layer 30 via an adhesive agent. In this case, as the adhesive, for example, a polyester adhesive, an epoxy adhesive, a polyurethane adhesive, an acrylic adhesive, a polyurethane adhesive, a hot melt adhesive, or the like can be used.

  Furthermore, in the said embodiment, although the dye-sensitized solar cell 100 is used as an installation object of the back seat | sheet 200, an installation object should just be a solar cell, Even if it is an organic thin film solar cell or a crystalline silicon solar cell. Good.

  Hereinafter, the content of the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

Example 1
First, a crosslinked resin layer was formed. The crosslinked resin layer is made of polyethylene (LDPE) pellets and 1,1-bis (3,3-dimethylbutylperoxy) cyclohexane (trade name) which is a catalyst for starting crosslinking (hereinafter referred to as “crosslinking agent”). : Perhexa HC (manufactured by NOF Corporation) was charged into an extruder and melted to crosslink the polyethylene to form a crosslinked resin layer made of crosslinked polyethylene having a thickness of 75 μm. When the gel fraction of the crosslinked resin layer thus obtained was measured, the gel fraction was 20%.

  On the other hand, an aluminum foil having a thickness of 6 μm was prepared as a metal layer. And the laminated film was obtained by carrying out dry lamination of this aluminum foil and a crosslinked resin layer. Next, a thermoplastic resin layer made of an ionomer (trade name: High Milan, manufactured by Mitsui DuPont Polychemical Co., Ltd.) was thermocompression bonded to the laminated film for 2 minutes under the conditions of 1 MPa and 200 ° C. Thus, a back sheet was obtained.

(Example 2)
A backsheet as in Example 1 except that the cross-linking agent was changed from perhexa HC to 1,1-di (t-butylperoxy) cyclohexane (trade name: perhexa C, manufactured by NOF Corporation). Was made. When the gel fraction was measured for the crosslinked resin layer in the thus obtained back sheet, the gel fraction was 15%.

(Example 3)
A back sheet was prepared in the same manner as in Example 1 except that the thermoplastic resin layer was changed from HiMilan to an ethylene-methacrylic acid copolymer (trade name: Nucrel, manufactured by Mitsui DuPont Polychemical Co., Ltd.). When the gel fraction was measured for the crosslinked resin layer in the thus obtained back sheet, the gel fraction was 40%.

Example 4
A back sheet was produced in the same manner as in Example 3 except that the cross-linking agent was changed from perhexa HC to perhexa C. When the gel fraction was measured for the crosslinked resin layer in the thus obtained back sheet, the gel fraction was 15%.

(Example 5)
First, a multilayer film of a crosslinked resin layer and a weather resistant layer was formed. In the multilayer film, pellets made of polyethylene and perhexa HC, which is a cross-linking agent, are put into an extruder and melted, while pellets made of polybutylene terephthalate (PBT) are put into an extruder and melted. It was obtained by coextrusion through the gap of the T die. Thus, a multilayer film composed of a crosslinked resin layer composed of a crosslinked polyethylene having a thickness of 75 μm and a weather resistant layer having a thickness of 50 μm was obtained.

  On the other hand, an aluminum foil having a thickness of 25 μm was prepared as a metal layer. And the laminated film was obtained by carrying out dry lamination of this aluminum foil and a crosslinked resin layer. Next, a thermoplastic resin layer made of an ionomer was thermocompression bonded to the laminated film in the same manner as in Example 1. Thus, a back sheet was obtained. When the gel fraction was measured for the crosslinked resin layer in the thus obtained back sheet, the gel fraction was 12%.

(Example 6)
A back sheet was produced in the same manner as in Example 5 except that the cross-linking agent was changed from perhexa HC to perhexa C. When the gel fraction was measured for the crosslinked resin layer in the thus obtained back sheet, the gel fraction was 15%.

(Example 7)
A back sheet was formed in the same manner as in Example 5 except that the PBT pellets were changed to PBT 99% by mass and carbon black 1% by mass, and the thermoplastic resin layer was changed from High Milan to Nuclerel. When the gel fraction was measured for the crosslinked resin layer in the back sheet thus obtained, the gel fraction was 60%.

(Example 8)
A back sheet was produced in the same manner as in Example 7 except that the cross-linking agent was changed from perhexa HC to perhexa C. When the gel fraction was measured for the crosslinked resin layer in the thus obtained back sheet, the gel fraction was 40%.

(Comparative Example 1)
First, a resin layer made of a PET film having a thickness of 75 μm was prepared.

  On the other hand, an aluminum foil having a thickness of 50 μm was prepared as a metal layer. And this aluminum foil and the resin layer were adhere | attached with the polyurethane-type adhesive agent (brand name: Takenate, Mitsui Chemicals make).

  On the other hand, a thermoplastic resin layer made of an ethylene-vinyl acetate copolymer (EVA) having a thickness of 10 μm was prepared, and the thermoplastic resin layer and the aluminum foil were bonded with the same polyurethane adhesive as described above. Thus, a back sheet was obtained.

(Comparative Example 2)
First, a resin layer made of a PEN film having a thickness of 75 μm was prepared.

  On the other hand, an aluminum foil having a thickness of 60 μm was prepared. And this aluminum foil and the resin layer were adhere | attached with the polyurethane adhesive similar to the comparative example 1. FIG.

  On the other hand, a thermoplastic resin layer made of high-milan having a thickness of 125 μm was prepared, and this thermoplastic resin layer and an aluminum foil were bonded together with the same polyurethane adhesive as in Comparative Example 1. Thus, a back sheet was obtained.

(Comparative Example 3)
First, a resin layer made of a 75 μm thick PET film and a weather resistant layer made of 50 μm thick polyethylene naphthalate (PEN) were prepared. Then, the resin layer and the weather resistant layer were adhered with the same polyurethane adhesive as in Comparative Example 1 to obtain a multilayer film.

  On the other hand, an aluminum foil having a thickness of 50 μm was prepared as a metal layer. And this aluminum foil and the multilayer film were adhere | attached with the polyurethane adhesive similar to the comparative example 1. FIG.

  On the other hand, a thermoplastic resin layer made of nucleol having a thickness of 30 μm was prepared, and the thermoplastic resin layer and the aluminum foil were bonded with the same polyurethane adhesive as in Comparative Example 1. Thus, a back sheet was obtained.

(Comparative Example 4)
First, a resin layer made of a 75 μm thick PEN film and a weathering layer made of 50 μm thick PET were prepared. Then, the resin layer and the weather resistant layer were adhered with the same polyurethane adhesive as in Comparative Example 1 to obtain a multilayer film.

  On the other hand, an aluminum foil having a thickness of 25 μm was prepared as a metal layer. And this aluminum foil and the multilayer film were adhere | attached with the polyurethane adhesive similar to the comparative example 1. FIG.

[Characteristic evaluation]
The following characteristics (1) to (4) were evaluated for the back sheets of Examples 1 to 8 and Comparative Examples 1 to 4 obtained as described above.

(1) Presence or absence of delamination First, using the backsheets obtained in Examples 1 to 8 and Comparative Examples 1 to 4, dye-sensitized solar cells with a backsheet were produced as follows.

  First, a dye-sensitized solar cell was produced as follows. First, a 10 cm × 10 cm × 4 mm FTO substrate was prepared. Subsequently, a titanium oxide paste (manufactured by Solaronix, Ti nanoixide T / sp) was applied on the FTO substrate by a doctor blade method in a range of 5 cm × 5 cm so as to have a thickness of 10 μm, and then hot air circulation was performed. A working electrode was obtained by placing in a type oven and baking at 150 ° C. for 3 hours to form a porous oxide semiconductor layer on the FTO substrate.

  On the other hand, the same FTO substrate as the working electrode was prepared as a counter electrode substrate. Then, a platinum catalyst film having a thickness of 10 nm was formed on the counter electrode substrate by a sputtering method to obtain a counter electrode.

  Thus, a working electrode and a counter electrode were prepared.

  Next, a square annular resin sheet was prepared in which an opening of 5 cm × 5 cm × 30 μm was formed in the center of a 6 cm × 6 cm × 30 μm sheet made of high Milan as an ionomer. And this resin sheet was arrange | positioned in the cyclic | annular site | part surrounding the porous oxide semiconductor layer of a working electrode. This resin sheet was bonded to the annular portion by heating and melting at a melting temperature of 120 ° C. for 5 minutes.

  Subsequently, a square annular resin sheet was prepared in which an opening of 5 cm × 5 cm × 30 μm was formed in the center of a 6 cm × 6 cm × 30 μm sheet made of nucleol which is an ethylene-methacrylic acid copolymer.

  Then, this square annular resin sheet made of nucleol was pasted at a melting temperature of 110 ° C. immediately above the square annular resin sheet made of high Milan. Thus, the first sealing portion was formed.

  Next, the working electrode was immersed in a dehydrated ethanol solution in which 0.2 mM of N719 dye, which is a photosensitizing dye, was dissolved for 24 hours to support the photosensitizing dye on the working electrode.

  On the other hand, a square annular resin sheet having an opening of 5 cm × 5 cm × 30 μm formed in the center of a 6 cm × 6 cm × 30 μm sheet made of high Milan as an ionomer on a counter electrode platinum catalyst film was prepared. And this resin sheet was arrange | positioned in the cyclic | annular site | part on the platinum catalyst film | membrane of a counter electrode. And this resin sheet was adhere | attached on the cyclic | annular site | part by heating and melting for 5 minutes at the melting temperature of 110 degreeC.

  Subsequently, a square annular resin sheet was prepared in which an opening of 5 cm × 5 cm × 30 μm was formed in the center of a 6 cm × 6 cm × 30 μm sheet made of nucleol which is an ethylene-methacrylic acid copolymer.

  Then, this square annular resin sheet made of nucleol was pasted at a melting temperature of 110 ° C. immediately above the square annular resin sheet made of high Milan. A second sealing portion was thus formed.

  Next, the working electrode provided with the first sealing portion is arranged so that the surface of the FTO substrate on the porous oxide semiconductor layer side is horizontal, and a volatile solvent made of acetonitrile is provided inside the first sealing portion. As a main solvent, 0.05M of lithium iodide, 0.1M of lithium iodide, 0.6M of 1,2-dimethyl-3-propylimidazolium iodide (DMPII), and 0.02 of 4-tert-butylpyridine. An electrolyte containing 5M was injected to form an electrolyte layer.

  Next, the counter electrode provided with the second sealing portion was opposed to the working electrode, placed in a reduced pressure environment of about 500 hPa, and the first sealing portion and the second sealing portion were overlapped. Then, under a reduced pressure environment, the brass frame having the same size as the sealing part is heated, the brass frame is arranged on the side opposite to the second sealing part of the counter electrode, and using a press machine, While pressurizing the first sealing portion and the second sealing portion at 5 MPa, they were locally heated and melted at a temperature of 160 ° C. to form a sealing portion, thereby obtaining a laminate. Then, this laminated body was taken out under atmospheric pressure. Thus, a dye-sensitized solar cell was obtained.

  And on the back surface (counter electrode side surface) of this dye-sensitized solar cell, the back sheets of Examples 1 to 8 and Comparative Examples 1 to 4 are overlaid so as to cover the counter electrode, and thermocompression bonded at 0.2 MPa and 150 ° C. did. At this time, the heating time was set to 60 seconds to prevent thermal deterioration of the cell. Thus, a dye-sensitized solar cell with a back sheet was obtained.

The dye-sensitized solar cell with a back sheet obtained as described above was allowed to stand for 2000 hours in an environment of 85 ° C. and 85% RH. And it was investigated by cutting the whole dye-sensitized solar cell with a backsheet, and observing the cross section of the obtained backsheet 10 places with an optical microscope whether there was peeling between the layers in a backsheet. The results are shown in Table 1. In Table 1, “◯” and “x” mean the following respectively.
○ ・ ・ ・ No delamination occurred between the layers in the backsheet × ・ ・ ・ Delamination occurred between the layers in the backsheet

(2) Voltage resistance After the backsheets obtained in Examples 1 to 8 and Comparative Examples 1 to 4 were stored at 85 ° C. and 85% RH for 2000 hours and dried sufficiently for 24 hours, The electrode was sandwiched between electrode plates, a voltage was applied between these electrode plates, and the dielectric breakdown voltage was examined. The results are shown in Table 1. In Table 1, “◯” and “x” mean the following respectively.
○: Dielectric breakdown voltage is 1 kV or more in the back sheet. X: Dielectric breakdown voltage is less than 1 kV in the back sheet.

(3) Presence / absence of cracks after 180 ° bending test The backsheets obtained in Examples 1 to 8 and Comparative Examples 1 to 4 were allowed to stand in an environment of 85 ° C and 85% RH for 2000 hours, and then 180. A bending test was conducted to check for cracks. The results are shown in Table 1. In Table 1, “◯” and “x” mean the following respectively.
○: No crack occurred in the back sheet ×: Crack occurred in the back sheet

(4) Weather resistance Weather resistance is determined by examining the presence or absence of cracks by performing a 180 ° bending test on the backsheets obtained in Examples 1 to 8 and Comparative Examples 1 to 4 after UV irradiation for 2000 hours. evaluated. The results are shown in Table 1. In Table 1, “◎”, “◯”, and “x” mean the following respectively.
◎ ... No cracking occurred in the backsheet ○: Cracking occurred only in a part of the weathering layer in the backsheet X: Cracking occurred in a layer other than the weathering layer in the backsheet

  From the results shown in Table 1, in the backsheets of Examples 1 to 8, delamination was not confirmed even after standing in a high-temperature and high-humidity environment. On the other hand, in the backsheets of Comparative Examples 1 to 4, delamination was confirmed in all after standing in a high temperature and high humidity environment.

  Moreover, all the backsheets of Examples 1 to 8 had excellent voltage resistance. On the other hand, all the back sheets of Comparative Examples 1 to 4 had low voltage resistance.

  From the above, according to the back sheet of the present invention, it was confirmed that delamination can be sufficiently suppressed even in a high temperature environment while having excellent voltage resistance.

DESCRIPTION OF SYMBOLS 30 ... Metal layer 40 ... Crosslinked resin layer 50 ... Thermoplastic resin layer 60 ... Weatherproof layer 100 ... Dye-sensitized solar cell (solar cell)
200 ... back sheet

Claims (5)

In a solar cell with a back sheet, comprising: a solar cell having a light incident surface; and a solar cell back sheet that covers and protects the back surface of the solar cell opposite to the light incident surface.
The solar cell backsheet includes a metal layer, a crosslinked resin layer laminated on the metal layer, and a weathering layer provided so as to sandwich the crosslinked resin layer together with the metal layer,
The metal layer is made of a metal material containing aluminum;
The crosslinked resin layer comprises a crosslinked polyolefin;
In the solar cell backsheet, the metal layer, the crosslinked resin layer, and the weathering layer are arranged in this order from the solar cell side ,
The back surface of the solar cell has an uneven shape,
The metal layer is deformed following the uneven shape on the back surface,
The crosslinked resin layer is deformed following the shape of the metal layer,
The solar cell with a back sheet , wherein the crosslinked polyolefin is a crosslinked polyethylene . The solar cell with a back sheet according to claim 1, wherein the weather-resistant layer contains a thermoplastic resin. The solar cell with a back sheet according to claim 2 , wherein the weather resistant layer further contains carbon. The solar cell with a back sheet according to any one of claims 1 to 3 , further comprising a thermoplastic resin layer provided so as to sandwich the metal layer together with the crosslinked resin layer. The solar cell with a back sheet according to any one of claims 1 to 4 , wherein the crosslinked resin layer is directly bonded to the metal layer.

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