JP5897283B2 - Solar cell with back sheet - Google Patents

Description

  The present invention relates to a solar cell with a back sheet comprising a solar cell and a back sheet 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.

  For this reason, the solar cell with a back sheet | seat provided with the back sheet | seat which has sufficient withstand voltage property and can fully suppress delamination also in a high temperature environment was calculated | required.

  The present invention has been made in view of the above circumstances, and has a back sheet solar equipped with a back sheet capable of sufficiently suppressing delamination even in a high temperature environment while having excellent voltage resistance. An object is to provide a battery.

  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 cells. 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 research, the present inventor has found that the above problem can be solved by laminating a resin layer containing a polyolefin having a predetermined gel fraction on the metal layer, thereby completing the present invention. It came to.

That is, the present invention is a solar cell with a backsheet comprising a solar cell and a backsheet that covers and protects the back surface of the solar cell, wherein the solar cell is a transparent substrate and the back against the transparent substrate. A plurality of solar cells provided on the sheet side and forming the back surface together with the transparent substrate, and the back sheet is laminated on the metal layer and the metal layer on the opposite side of the solar cell. A resin layer, the resin layer is directly bonded to the metal layer, the metal layer is made of a metal material containing aluminum, and the resin layer is made of only polyethylene having a gel fraction of 40 to 60%. 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 resin layer is deformed following the shape of the metal layer. The back It is a solar cell with a sheet.

According to this solar cell with a back sheet , the back surface of the solar cell has an uneven shape, and in the back sheet, the metal layer is deformed following the uneven shape on the back surface of the solar cell, The resin layer laminated on the opposite side is also deformed following the shape of the metal layer. At this time, since the resin layer made only of polyethylene having a gel fraction of 40 to 60% has high voltage resistance, it can be thinned while having excellent voltage resistance. For this reason, the resin layer can maintain the state following the shape of the metal layer. In addition, the backsheet may receive light from sunlight reflection, and the resin layer may become high temperature. Even in this case, in the solar cell with a back sheet of the present invention, the resin layer is made of only polyethylene having a gel fraction of 40 to 60% and has a high melting point, so that the state following the shape of the metal layer is maintained. be able to. Therefore, according to the solar cell with a back sheet of the present invention, delamination in the back sheet can be sufficiently suppressed even in a high temperature environment while exhibiting excellent voltage resistance.

In the solar cell with the backsheet, when the solar cell has a plurality of solar cells that form the back surface together with the transparent substrate, there will be more irregularities, but even in that case, according to the present invention, While exhibiting excellent voltage resistance, delamination in the backsheet can be sufficiently suppressed even in a high temperature environment. In addition, since the resin layer is directly bonded to the metal layer, the adhesive deteriorates even in a high-temperature and high-humidity environment compared to when the resin layer and the metal layer are bonded via an adhesive. Therefore, peeling between the resin layer and the metal layer can be sufficiently suppressed. Further, since the polyolefin contained in the resin layer of the backsheet is polyethylene, it is less expensive than the case where the polyolefin is other than polyethylene, and appropriate flexibility can be maintained in the backsheet.

  In the solar cell with a back sheet, it is preferable that the back sheet further includes a weather resistant layer provided so as to sandwich the resin layer together with the metal layer.

  In this case, even if light due to the reflection of sunlight enters the back sheet from the weather resistant layer side, the incident intensity of the light on the 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 resin layer is less likely to reach a high temperature, and the shape of the resin layer is easily maintained. As a result, peeling of the resin layer from the metal layer is more sufficiently suppressed.

  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 resin layer can be improved more.

  The weather resistant layer preferably further contains carbon.

  In this case, when the back sheet of the present invention is installed on the back surface of the solar cell with the metal layer facing the solar cell side, light from sunlight reflection enters the back sheet from the weather resistant layer side. However, compared with the case where a weather-resistant layer does not contain carbon further, deterioration of the back sheet by ultraviolet irradiation can be suppressed more fully, and generation | occurrence | production of the crack in a back sheet can be suppressed more fully.

  In the solar cell with a back sheet, it is preferable that the back sheet further includes a thermoplastic resin layer provided so as to sandwich the metal layer together with the 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.

  ADVANTAGE OF THE INVENTION According to this invention, the solar cell with a back sheet | seat provided with the back sheet | seat which has sufficient withstand voltage property and can fully suppress delamination also in a high temperature environment is provided.

It is a fragmentary sectional view showing one embodiment of a solar cell with a back sheet concerning the present 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 an embodiment of a solar cell with a back sheet according to the present invention, 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) provided on the back sheet 200 side. ) The solar battery cell 20 is provided. The solar battery cell 20 forms the back surface 100 b of the dye-sensitized solar battery 100 together with the common substrate 10. 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. The back surface 100 b has a concavo-convex shape by the solar cells 20 provided on the common substrate 10.

  On the other hand, as shown in FIG. 2, the back sheet 200 includes a metal layer 30 and a resin layer 40 laminated on the opposite side of the dye-sensitized solar cell 100 with respect to the metal layer 30. Here, the resin layer 40 is directly bonded to the metal layer 30. The backsheet 200 further includes a thermoplastic resin layer 50 provided so as to sandwich the metal layer 30 together with the resin layer 40, and a weather resistant layer 60 provided so as to sandwich the resin layer 40 together with the metal layer 30. .

  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 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 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 resin layer 40 contains a polyolefin having a gel fraction of 40% or more.

  Here, the back surface 100b of the dye-sensitized solar cell 100 has a concavo-convex shape by the plurality of solar cells 20 provided on the common substrate 10 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 resin layer 40 is also deformed following the shape of the metal layer 30. doing. At this time, in the backsheet 200, since the resin layer 40 containing polyolefin having a gel fraction of 40% or more has high voltage resistance, the resin layer 40 can be thinned while having excellent voltage resistance. It becomes. For this reason, the 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 resin layer 40 may become high temperature. Even in this case, in the backsheet 200, since the resin layer 40 includes a polyolefin having a gel fraction of 40% or more and has a high melting point, the resin layer 40 follows the shape of the metal layer 30. Can be maintained. Therefore, according to the dye-sensitized solar cell 300 with the back sheet, the back sheet 200 can sufficiently suppress delamination even in a high temperature environment while exhibiting excellent voltage resistance. As a result, the occurrence of a discharge in the gap generated between the metal layer 30 and the resin layer 40 is sufficiently suppressed, and the deterioration of the photoelectric conversion characteristics of the dye-sensitized solar cell 300 with the backsheet due to the discharge is sufficiently suppressed. can do.

  Further, in the backsheet 200, a weather resistant layer 60 is provided so as to sandwich the resin layer 40 together with the metal layer 30. For this reason, even if light from sunlight reflection enters the back sheet 200 from the weather resistant layer 60 side, the incident intensity of the light on the 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 resin layer 40 becomes difficult to become high temperature, and it becomes easy to hold | maintain the shape of the resin layer 40. As a result, peeling of the resin layer 40 from the metal layer 30 is more sufficiently suppressed.

  Further, since the backsheet 200 includes the thermoplastic resin layer 50 provided so as to sandwich the metal layer 30 together with the resin layer 40, even if the back surface 100b of the dye-sensitized solar cell 100 is uneven by the thermoplastic resin, The back surface 100b and the metal layer 30 can be adhered.

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

  Next, the metal layer 30, the resin layer 40, the thermoplastic resin layer 50, and the weather resistant layer 60 constituting 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.

(Resin layer)
The resin layer 40 should just contain the polyolefin which has a gel fraction of 40% or more. When the gel fraction of the polyolefin is less than 40%, the melting point of the polyolefin is lowered, so that when the light from sunlight is incident on the back sheet 200, the resin layer 40 follows the uneven shape of the metal layer 30. The formed shape cannot be maintained, and the resin layer 40 is peeled off from the metal layer 30.

However, the resin layer 40 is one of the layers constituting the back sheet 200. For this reason, the resin layer 40 is required to have a flexibility that does not cause cracks or the like during construction of the backsheet 200 or when stress is applied to the backsheet 200. If this minimum flexibility is defined using the gel fraction as an index, the gel fraction of the resin layer 40 is preferably 60% or less. Here, the “gel fraction” refers to the mass fraction of the solid before and after immersing the 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)

  Examples of the polyolefin having a gel fraction of 40% or more include a crosslinked polyolefin or an ultrahigh molecular weight polyolefin.

  The cross-linked polyolefin is a cross-linked polyolefin.

  Ultra high molecular weight polyolefin refers to polyolefin having a molecular weight of 500,000 or more.

  Examples of the polyolefin include polyethylene, polypropylene, and polybutylene. Among these, polyethylene is preferable. In this case, compared to the case where the polyolefin is other than polyethylene, the cost is low, and appropriate flexibility in the backsheet 200 can be maintained. The polyethylene may be any of linear polyethylene, low density polyethylene (LDPE), and high density polyethylene, but low density polyethylene is particularly preferable. This low density polyethylene can realize the resin layer 40 having excellent heat distortion resistance as compared with the high density polyethylene, and can stably maintain the shape of the resin layer 40 even in a high temperature environment.

  When the polyolefin having a gel fraction of 40% or more is an ultrahigh molecular weight polyolefin, the molecular weight is preferably 500,000 or more, more preferably 1,000,000 or more. However, the molecular weight of the polyolefin is preferably 5 million or less because the flexibility is appropriately secured.

  The content of the polyolefin having a gel fraction of 40% or more contained in the resin layer 40 is preferably 60% by mass or more, more preferably 80% by mass or more, and further preferably 100% by mass.

  The thickness of the 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 μm 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 resin layer 40 is within the above range, there is an advantage that the resin layer 40 can withstand the required breakdown voltage unlike when it is less than 20 μm. When the thickness of the resin layer 40 is within the above range, the resin layer 40 can more easily follow the shape of the back surface 100b of the dye-sensitized solar cell 100 than when the thickness exceeds 300 μm. The peeling of the 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, the adhesiveness with the resin layer 40 can be further improved as compared with the case where the weather resistant layer 60 does not contain a thermoplastic resin. Examples of the thermoplastic resin include polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene nadilate (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 carbon content 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 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 the manufacturing method of the dye-sensitized solar cell 300 with a back sheet will be described.

  First, a multilayer film of the resin layer 40 and the weather resistant layer 60 is formed. 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 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.

  At this time, in order to increase the gel fraction of the polyolefin contained in the resin layer 4 to 40% or more, for example, high-energy electron beams or gamma rays may be irradiated.

  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.

  On the other hand, a dye-sensitized solar cell 100 is prepared.

  Then, the back sheet 200 is installed on the dye-sensitized solar cell 100 so as to cover and protect the back surface 100b of the dye-sensitized solar cell 100 by, for example, thermocompression bonding. At this time, the thermoplastic resin layer 50 of the back sheet 200 is directed to the dye-sensitized solar cell 100 side, and the weather-resistant layer 60 is directed to the side opposite to the dye-sensitized solar cell 100. Thereby, the back sheet 200 will deform | transform following the uneven | corrugated shape of the back surface 100b of the dye-sensitized solar cell 100. FIG. Thus, the production of the dye-sensitized solar cell 300 with the backsheet is completed.

  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, although the resin layer 40 is directly bonded to the metal layer 30 in the above embodiment, the resin layer 40 may be bonded to the metal layer 30 via an adhesive. 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 a solar cell, an organic thin film solar cell and a crystalline silicon solar cell can also be used as a solar cell.

  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 resin layer was formed. The resin layer is made by introducing pellets made of polyethylene (LDPE) into an extruder and melted to form a resin layer made of ultrahigh molecular weight polyethylene having a thickness of 75 μm, and an electron beam is applied so that the dose in the atmosphere becomes 240 kGy. Crosslinking was performed by irradiation. When the gel fraction was measured for the resin layer thus obtained, the gel fraction was 60%. Further, when the ultrahigh molecular weight polyethylene was measured by a high temperature GPC (gel permeation chromatography) method, the molecular weight was 800,000.

  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 the 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.

  On the other hand, a dye-sensitized solar cell was produced as follows. First, a 10 cm × 10 cm × 4 mm FTO substrate was prepared. Subsequently, after applying a titanium oxide paste (Solaronix, Ti nanoixide T / sp) on the FTO substrate by a doctor blade method so that the thickness becomes 10 μm, it is put in a hot air circulation type oven. Firing was performed at 150 ° C. for 3 hours to form a porous oxide semiconductor layer on the FTO substrate to obtain a working electrode of 5 cm × 5 cm.

  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.

(Example 2)
The resin layer was formed by irradiating an electron beam so that the dose in the atmosphere was 180 kGy, and the same as in Example 1 except that the gel fraction of the resin layer in the backsheet was changed from 60% to 40%. Thus, a dye-sensitized solar cell with a back sheet was produced. At this time, when the molecular weight of the ultrahigh molecular weight polyethylene in the resin layer of the back sheet was measured in the same manner as in Example 1, the molecular weight was 500,000.

(Example 3)
Except that the thermoplastic resin layer was changed from High Milan to an ethylene-methacrylic acid copolymer (trade name: Nucrel, manufactured by Mitsui DuPont Polychemical Co., Ltd.), dye sensitization with a backsheet was performed in the same manner as in Example 1. A solar cell was produced. At this time, when the molecular weight of the ultrahigh molecular weight polyethylene in the resin layer of the back sheet was measured in the same manner as in Example 1, the molecular weight was 1,600,000.

Example 4
The resin layer was formed by irradiating the electron beam so that the dose in the atmosphere was 180 kGy, and the same as in Example 3 except that the gel fraction of the resin layer in the backsheet was changed from 60% to 40%. Thus, a dye-sensitized solar cell with a back sheet was produced. At this time, when the molecular weight of the ultrahigh molecular weight polyethylene in the resin layer of the back sheet was measured in the same manner as in Example 1, the molecular weight was 1,200,000.

(Example 5)
First, a multilayer film of a 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 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. At this time, when the molecular weight of the ultrahigh molecular weight polyethylene in the resin layer of the back sheet was measured in the same manner as in Example 1, the molecular weight was 2.4 million.

  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 the 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 resin layer in the thus obtained back sheet, the gel fraction was 60%.

  And the back sheet | seat obtained in this way was thermocompression-bonded on the back surface of the dye-sensitized solar cell obtained by carrying out similarly to Example 1, and the dye-sensitized solar cell with a back sheet was produced.

(Example 6)
The resin layer was formed by irradiating the electron beam so that the dose in the atmosphere was 180 kGy, and the same as in Example 5 except that the gel fraction of the resin layer in the backsheet was changed from 60% to 40%. Thus, a dye-sensitized solar cell with a back sheet was produced. At this time, when the molecular weight of the ultrahigh molecular weight polyethylene in the resin layer of the back sheet was measured in the same manner as in Example 1, the molecular weight was 1,800,000.

(Example 7)
The pellets made of polybutylene terephthalate (PBT) were changed to pellets made of 99% by weight of PBT and 1% by weight of carbon black, and the thermoplastic resin layer was changed from High Milan to Nuclerel. A dye-sensitized solar cell with a sheet was produced. At this time, when the molecular weight of the ultrahigh molecular weight polyethylene in the resin layer of the back sheet was measured in the same manner as in Example 1, the molecular weight was 800,000.

(Example 8)
The resin layer was formed by irradiating the electron beam so that the dose in the atmosphere was 180 kGy, and the same as in Example 7 except that the gel fraction of the resin layer in the backsheet was changed from 60% to 40%. Thus, a dye-sensitized solar cell with a back sheet was produced. At this time, when the molecular weight of the ultrahigh molecular weight polyethylene in the resin layer of the back sheet was measured in the same manner as in Example 1, the molecular weight was 500,000.

(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.

  And the back sheet | seat obtained in this way was thermocompression-bonded on the back surface of the dye-sensitized solar cell obtained by carrying out similarly to Example 1, and the dye-sensitized solar cell with a back sheet was produced.

(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.

  And the back sheet | seat obtained in this way was thermocompression-bonded on the back surface of the dye-sensitized solar cell obtained by carrying out similarly to Example 1, and the dye-sensitized solar cell with a back sheet was produced.

(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.

  And the back sheet | seat obtained in this way was thermocompression-bonded on the back surface of the dye-sensitized solar cell obtained by carrying out similarly to Example 1, and the dye-sensitized solar cell with a back sheet was produced.

(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. Thus, a back sheet was obtained.

  And the obtained back sheet | seat was thermocompression-bonded on the back surface of the dye-sensitized solar cell obtained by carrying out similarly to Example 1, and the dye-sensitized solar cell with a back sheet was produced.

[Characteristic evaluation]
For the dye-sensitized solar cells with backsheets of Examples 1 to 8 and Comparative Examples 1 to 4 obtained as described above, the following characteristics (1) to (4) were evaluated.

(1) Presence / absence of delamination First, the dye-sensitized solar cells with 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 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 The back sheet of the dye-sensitized solar cell with back sheet obtained in Examples 1 to 8 and Comparative Examples 1 to 4 is sandwiched between a pair of electrode plates, and a voltage is applied between these electrode plates. Then, the breakdown voltage was examined. The results are shown in Table 1. In Table 1, “◯” and “x” mean the following respectively.
○: Dielectric breakdown voltage of the back sheet is 1 kV or more x: Dielectric breakdown voltage of the back sheet is less than 1 kV

(3) Presence / absence of cracks after 180 ° bending test About the dye-sensitized solar cells with backsheets obtained in Examples 1 to 8 and Comparative Examples 1 to 4, the sample was still for 2000 hours in an environment of 85 ° C and 85% RH. After being placed, a 180 ° bending test was performed to check for cracks in the backsheet. 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 was determined by subjecting the back sheets of the dye-sensitized solar cells with back sheets obtained in Examples 1 to 8 and Comparative Examples 1 to 4 to UV irradiation for 2000 hours, and then performing a 180 ° bending test. And evaluated by examining the presence or absence of cracks. 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 dye-sensitized solar cells with backsheets of Examples 1 to 8, delamination was not confirmed in all backsheets even after standing in a high-temperature and high-humidity environment. On the other hand, in the dye-sensitized solar cells with backsheets of Comparative Examples 1 to 4, delamination was confirmed in all the backsheets after standing in a high temperature and high humidity environment.

  Moreover, all the back sheets of the dye-sensitized solar cells with back sheets of Examples 1 to 8 had excellent voltage resistance. On the other hand, the backsheets of the dye-sensitized solar cells with backsheets of Comparative Examples 1 to 4 all had low voltage resistance.

  From the above, according to the dye-sensitized solar cell with a back sheet of the present invention, the back sheet has an excellent voltage endurance and can sufficiently suppress delamination even in a high temperature environment. It was confirmed that a dye-sensitized solar cell with a back sheet was obtained.

10 ... Common substrate (transparent substrate)
DESCRIPTION OF SYMBOLS 20 ... Solar cell 30 ... Metal layer 40 ... Resin layer 50 ... Thermoplastic resin layer 60 ... Weatherproof layer 100 ... Dye-sensitized solar cell (solar cell)
100b ... Back surface 200 ... Back sheet 300 ... Dye-sensitized solar cell with back sheet (solar cell with back sheet)

Claims (5)

A solar cell with a backsheet comprising a solar cell and a backsheet that covers and protects the back surface of the solar cell,
The solar cell is
A transparent substrate;
A plurality of solar cells provided on the backsheet side with respect to the transparent substrate and forming the back surface together with the transparent substrate;
The backsheet is
A metal layer,
A resin layer laminated on the opposite side of the solar cell with respect to the metal layer,
The resin layer is directly bonded to the metal layer;
The metal layer is made of a metal material containing aluminum;
The resin layer is Ri Do because only polyethylene with 40% to 60% of the gel fraction,
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 solar cell with a back sheet , wherein the resin layer is deformed following the shape of the metal layer . The solar cell with a back sheet according to claim 1, wherein the back sheet further includes a weather-resistant layer provided so as to sandwich the resin layer together with the metal layer. The solar cell with a back sheet according to claim 2 , wherein the weather-resistant layer contains a thermoplastic resin. The solar cell with a back sheet according to claim 3 , wherein the weather-resistant layer further contains carbon. The solar cell with a back sheet according to any one of claims 1 to 4 , further comprising a thermoplastic resin layer provided so that the back sheet sandwiches the metal layer together with the resin layer.

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