JP2007329240A - Solar cell module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solar cell module that is surely prevented in breakdown of a solar cell in the sealing process. <P>SOLUTION: In the solar cell module, a transparent protecting member in the front surface side has fine uneven portions at least at its front surface in the solar cell side, and a weighted thickness T<SB>C</SB>of a sealing film for solar cell satisfies the formula (1): T<SB>C</SB>=T<SB>A</SB>+T<SB>B</SB>+a. In the formula (1), T<SB>C</SB>indicates a weighted thickness of the sealing film for solar cell (unit: mm); T<SB>A</SB>, a thickness of a bus bar electrode (unit: mm); T<SB>B</SB>, a depth of recess of fine uneven portions (unit: mm), and a is an integer equal to 0.2 or larger. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a solar cell module, and more particularly, to a solar cell module that can effectively prevent damage to solar cells in a sealing process during solar cell module fabrication.

  In recent years, solar cells that directly convert sunlight into electrical energy have been widely used and further developed in terms of effective use of resources and prevention of environmental pollution.

  In the solar cell module, since the electrical output of the solar cells per sheet is small, the electrical output is improved by connecting a plurality of solar cells in series or in parallel.

  For example, as shown in FIG. 1, the solar cell module has a plurality of solar cells 14 that are electrically connected to each other by connection tabs 18 made of a conductive material such as copper foil, and the surface side transparent protection made of a glass substrate or the like. It is set as the structure sealed through the surface side sealing film 13a and the back surface side sealing film 13b of an ethylene-vinyl acetate copolymer (EVA) film between the member 11 and the back surface side protection member (back cover) 12. ing.

  In addition, the solar battery cell 14 used in such a solar battery module generally has a configuration in which the front surface side electrode 16 and the rear surface side electrode 17 are formed on the front surface side and the back surface side of the semiconductor substrate 15. In the semiconductor substrate 15, an N-type region 15a and a P-type region 15b are formed, and a semiconductor junction (PN junction) 15c is formed at an interface portion between the N-type region 15a and the P-type region 15b.

  The front surface side electrode 16 and the back surface side electrode 17 provided on both surfaces of the solar battery cell 14 have a bus bar electrode 19a and finger electrodes 19b, as shown in FIG. A large number of finger electrodes 19b are formed in parallel to one side of the solar battery cell in order to collect photogenerated carriers. Also, several bus bar electrodes 19a are formed so as to intersect perpendicularly with the finger electrodes 19b in order to collect the collected carriers.

  A transparent substrate such as a glass substrate is used for the surface-side transparent protective member 11 used in the conventional solar cell module in order to make sunlight enter the battery as efficiently as possible and concentrate it on the solar cell 14. ing. Furthermore, in order to improve the adhesiveness with the solar cell sealing film 13a and to reduce the reflectance of sunlight and to provide an antiglare effect, the surface of the surface side transparent protective member 11 and / or the light receiving side. A plurality of fine concavo-convex portions are provided on the surface side surface by embossing or the like.

  In such a solar cell, the surface side transparent protective member, the surface side sealing film, the solar cell, the back surface side sealing film, and the back surface side protective member are laminated in this order, heated and pressurized, and EVA is crosslinked and cured. Then, it is manufactured by bonding and integrating and sealing.

  Thus, in producing the solar cell module, the EVA film is pressed against the solar cell during the heating and pressurization in the sealing step, so that the solar cell is broken by this pressing force. In addition, there is also a problem that the yield of the product is reduced by entraining air due to poor deaeration at the time of sealing, or when the EVA film flows when heated and pressurized, and the resin protrudes from the end face of the laminate. there were.

  In order to solve the above problems, Patent Documents 1 and 2 disclose a solar cell module using an EVA film provided with a recess having a predetermined shape by embossing as a solar cell sealing film. Has been. By providing a recess in the EVA film, the film can be cushioned and the deaeration can be improved. As a result, high quality solar cells can be manufactured with high yield.

  Patent Document 3 discloses that, in a solar cell module, an EVA film formed with an opening for accommodating solar cells is used as a solar cell sealing film. Furthermore, Patent Document 4 discloses that a solar cell sealing film having a compression rate at 65 ° C. of 10% or more is used. According to these sealing films for solar cells, it becomes possible to reduce the cracking of the solar cells by reducing the stress on the solar cells in the heating and pressurization in the sealing step.

Special table 3473605 gazette JP 2005-79332 A Japanese Patent Laid-Open No. 2004-63673 JP 2003-51605 A

  Although a wide range of research and development has been conducted on solar cell modules, in order to promote the spread, attempts have been made to reduce the thickness of solar cells, particularly from the viewpoint of cost reduction. That is, in order to obtain a solar cell having high crystal quality, an expensive high-purity material is used for manufacturing a semiconductor substrate of the solar cell. Therefore, in order to reduce the manufacturing cost of the solar cell module, it is necessary to reduce the amount of expensive high-purity material used by thinning the semiconductor substrate in the solar cell.

  However, in the conventional solar cell module, when the thickness of the semiconductor substrate is further reduced, the semiconductor substrate is very fragile, so that cracks and cracks are likely to occur, and the damage rate of the solar cells rapidly increases. In the solar cell modules of Patent Documents 1 to 4, the solar cell is prevented from being damaged, but the production of the EVA sealing film becomes complicated, and the solar cell is damaged depending on conditions such as when the cell is thin. There is a fear.

  Then, an object of this invention is to provide the solar cell module with which the damage of the photovoltaic cell in the sealing process was prevented reliably.

  As a result of various studies on the damage of the solar battery cells in the sealing step of the solar battery module, the present inventors have found that the generation of cracks and cracks in the semiconductor substrate that causes damage to the solar battery cells It has been found that it tends to occur around the bus bar electrodes formed on both sides. Therefore, in order to more reliably prevent damage to the solar battery cells, it is effective to prevent the occurrence of cracks and cracks that may occur in the vicinity of the bus bar electrodes on the semiconductor substrate.

Therefore, the present invention comprises a semiconductor substrate and bus bar electrodes provided on the front surface side and the back surface side via a solar cell sealing film between the front surface side transparent protection member and the back surface side protection member. A solar cell module formed by sealing a plurality of solar cells,
The surface-side transparent protective member has a fine uneven portion on at least the solar cell side surface,
Basis weight thickness T _C of the sealing film wherein the solar cell, the following equation (1):

[In Formula (1), T _C represents the basis weight thickness (unit: mm) of the solar cell sealing film, T _A represents the thickness (unit: mm) of the bus bar electrode, and T _B represents the above It represents the depth (unit: mm) of the concave portion of the fine uneven portion, and a is an integer of 0.2 or more. The above problem is solved by a solar cell module characterized by satisfying the above.

  Preferred embodiments of the solar cell of the present invention are listed below.

(1) a in the formula (1) is 0.3 or more, particularly 0.4 or more. Thereby, damage to the semiconductor substrate can be sufficiently prevented.
(2) a in the formula (1) is 1 or less.
(3) The thickness of the semiconductor substrate is 0.01 to 0.5 mm. Thus, even if the thickness of the semiconductor substrate is thin, it is possible to prevent damage to the solar battery cell.
(4) The thickness T _{A of the} bus bar electrode is 0.02 to 0.6 mm. Thereby, it is possible to prevent damage to the semiconductor substrate while collecting photogenerated carriers.
(5) The fine uneven part in the said surface side transparent protection member is provided by embossing.
(6) the depth T _B of the recess of the minute uneven portion, is of 0.02 to 0.5 mm.
(7) The said surface side transparent protection member is a glass substrate.
(8) The back surface side protection member is made of a plastic film.
(9) Since the solar cell sealing film is excellent in water resistance and transparency, it is a film obtained by depositing a composition containing an ethylene-vinyl acetate copolymer.

  According to the present invention, by determining the basis weight of the solar cell sealing film as described above, the semiconductor substrate can be highly prevented from being damaged during the manufacturing process by a simple method. Thereby, even if the thickness of the semiconductor substrate is thin, the semiconductor substrate is not damaged, and a highly reliable solar cell module can be provided.

  First, the structure of the solar cell module of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing an example of a cross-sectional structure of a solar cell module of the present invention. 2 and 3 are diagrams showing examples of the shape of the electrode of the solar battery cell, respectively. In the present invention, the light receiving surface side with respect to the solar battery cell is referred to as “front surface side”, and the surface opposite to the light receiving surface of the solar battery cell is referred to as “back surface side”.

  The structure of the solar cell module of the present invention is the same as that of a conventionally known solar cell module, and is not particularly limited. For example, as shown in FIG. 1 described above, a plurality of solar cells 14 are electrically connected to each other by connection tabs 18, and the surface side sealing is performed between the surface side transparent protection member 11 and the back surface side transparent protection member 12. The structure sealed through the stop film 13a and the back surface side sealing film 13b is used.

  Moreover, in the solar cell joule of this invention, as shown in FIG. 1, the unevenness | corrugation is formed in the solar cell side surface at least of the surface side transparent protection member. Thereby, the improvement of the adhesiveness of a surface side transparent protection member and a surface side sealing film, provision of an anti-glare effect, etc. are possible.

  The solar battery cell 14 of the present invention is basically formed of a semiconductor substrate 15, a front surface side electrode 16 and a back surface side electrode 17 disposed on the front surface side and the back surface side, respectively. As shown in FIG. 2, the front surface side electrode 16 and the back surface side electrode 17 have a bus bar electrode 19a and a finger electrode 19b for taking out an electrical output.

In the solar cell module of the present invention, the basis thickness of the solar cell sealing film is T _C (unit: mm), the thickness of the bus bar electrode is T _A (unit: mm), and the solar cell side When the depth of the concave portion of the fine uneven portion on the surface is T _B (unit: mm), the basis thickness T _C of the solar cell sealing film satisfies the following formula (1).

  In the formula (1), a is an integer of 0.2 or more, preferably an integer of 0.3 or more, more preferably an integer of 0.4 or more.

  As described above, in the present invention, it has been found that the occurrence of cracks or cracks in the semiconductor substrate that causes damage to the solar cells is likely to occur around the bus bar electrodes formed on both sides of the semiconductor substrate. This is because the pressure applied to the solar cells by heat and pressure is not uniform in the sealing process at the time of manufacturing the semiconductor module, and the pressure tends to concentrate around the part where the bus bar electrode etc. are formed. It is considered that the surface-side transparent protective member having a relatively high hardness is enhanced by the fine irregularities formed on the surface of the solar battery cell, causing damage to the semiconductor substrate. Therefore, by determining the thickness of the solar cell sealing film so as to satisfy the above formula (1), the solar cell sealing is performed according to the thickness of the bus bar electrode and the depth of the concave portion of the surface side transparent protective member. A high cushioning property of the film can be ensured, and it is possible to prevent damage to the solar battery cell due to the occurrence of cracks or cracks in the semiconductor substrate.

  In the formula (1), a is preferably 1 or less. Thereby, damage to the solar battery cell is highly prevented, and a thin solar battery module can be obtained.

In the formula (1), the solar cell sealing film having a basis weight thickness T _C (unit: mm) is a calculated value as follows. That is, the weight W ₁ (unit: g / 100 cm ² ) of the solar cell sealing film cut to a size of 10 cm × 10 cm and the main components such as the copolymer used for forming the solar cell sealing film Using the specific gravity D ₁ (unit: g / cm ³ ) of the component material, the value is calculated by the following formula (A).

For example, when a solar cell sealing film formed using EVA is used, the specific gravity D ₁ is the specific gravity of EVA, that is, 0.95 g / cm ³ .

In the above formula (1), the thickness T _A (unit: mm) of the bus bar electrode is obtained by photographing the cross section of the solar battery cell using a scanning electron microscope and measuring the thickness of the bus bar electrode. It is done.

In the formula (1), the depth of the concave portion of the solar cell side surface of the surface-side transparent protective member T _B (unit: mm) is a calculated value as follows. First, the basis weight T _B1 (unit: mm) of the surface-side transparent protective part was set in the same manner as described above, and the weight W ₂ (unit: g / kg) of the surface-side transparent protective part cut to a size of 10 cm × 10 cm. and 100 cm ^2), a specific gravity D ₂ (units of the main component material used to form the transparent front side protection unit: g / cm ³⁾ and is used to calculated by the following formula (B).

When a glass substrate made of silicon oxide or the like is used as the surface side transparent protective part material, the specific gravity D ₂ is the specific gravity of glass, that is, 2.5 g / cm ³ .

Next, the apparent thickness T _B2 (unit: mm) of the surface side transparent protective member is measured using a measuring device such as a dial gauge 2046SB manufactured by Mitutoyo Corporation. The “apparent thickness of the front surface side transparent protective member” means the thickness of the convex and concave portions of the front surface side transparent protective member.

Then, as in the following formula (C), a value obtained by subtracting the basis weight thickness T _B1 of the surface-side transparent protective part from the apparent thickness T _B2 of the surface-side transparent protective member, the solar cell side of the transparent front side protection member The depth of the concave portion on the surface is T _B (unit: mm).

  Hereinafter, the configuration of the solar cell module of the present invention will be described with reference to a preferred embodiment.

(Semiconductor substrate)
As the semiconductor substrate used in the solar battery cell of the present invention, a conventionally known substrate such as a semiconductor substrate on which a PN junction is formed can be used without particular limitation. As the semiconductor substrate, an optical semiconductor element composed of single crystal, polycrystal, or amorphous is used. Specifically, amorphous silicon a-Si, hydrogenated amorphous silicon a-Si: H, hydrogenated amorphous silicon carbide a-SiC: H, amorphous silicon nitride, etc. Amorphous or microcrystalline amorphous silicon semiconductors composed of alloys with other elements such as carbon, germanium, tin, etc. are pin type, nip type, ni type, pn type, MIS type, heterojunction type, homojunction A semiconductor layer configured as a mold, a Schottky barrier type, or a combination of these is used. In addition, the optical semiconductor layer may be CdS-based, GaAs-based, InP-based, or the like.

  The following method is mentioned as an example of the manufacturing method of a semiconductor substrate. Using a solution containing N-type impurities such as phosphorus atoms on the surface of a P-type semiconductor silicon substrate made of single crystal silicon, polycrystalline silicon, single crystal gallium arsenide, etc., an impurity diffusion layer is formed on the surface layer of the silicon substrate. An N-type diffusion layer is formed to form a semiconductor junction. In this way, an N-type region and a P-type region are formed in the semiconductor substrate, and a semiconductor junction (PN junction) is formed at the interface portion between the N-type region and the P-type region.

  Such a semiconductor substrate is arranged in the solar cell module such that the N-type region is on the front side and the P-type region is on the back side. An antireflection film made of a silicon nitride film may be formed on the surface side of the semiconductor substrate. Such an antireflection film is formed by, for example, a plasma CVD method or the like.

  The thickness of the semiconductor substrate is generally about 0.3 to 0.5 mm. However, from the viewpoint of cost reduction and thickness reduction, the thickness of the semiconductor substrate is preferably 0.01 to 0.5 mm, particularly 0.01 to 0.3 mm. In the solar cell module of the present invention, even if the thickness of the semiconductor substrate is thin, the solar cell can be highly prevented from being damaged.

Note that the thickness T _A (unit: mm) of the semiconductor substrate is obtained by photographing the cross section of the solar battery cell using a scanning electron microscope or the like and measuring the thickness of the semiconductor substrate.

  The size of the semiconductor substrate is not particularly limited as long as it is about 100 to 155 mm square.

(Front side electrode, Back side electrode)
In the semiconductor substrate, a front-side electrode is formed on the surface of the N-type region, and a back-side electrode is formed on the surface of the P-type region. As shown in FIG. 2, the front surface side electrode 16 and the back surface side electrode 17 have a bus bar electrode 19a and a finger electrode 19b for taking out an electrical output. However, the form of the back surface side electrode is not limited to that shown in FIG. 2, and may be a form composed of the back surface side bus bar electrode 20a and the back surface side current collecting electrode 20b as shown in FIG.

  The electrodes such as the bus bar electrode, the finger electrode, and the back side current collecting electrode are preferably formed using a highly conductive material such as silver or aluminum. As the means for forming each of these electrodes, for example, means such as vapor deposition of an electrode material by electron beam heating in high vacuum, screen printing of a paste containing the electrode material, or plating of the electrode material can be used. Thereafter, in order to obtain good ohmic contact between the semiconductor substrate and each electrode, it is preferable to perform a heat treatment at 400 ° C. to 500 ° C.

  Several bus bar electrodes are formed in parallel with one side of the semiconductor substrate so as to intersect the finger electrodes perpendicularly. The width of the bus bar electrode may be about 2 mm, and the width of the finger electrode may be about 0.2 mm.

  The thickness of the bus bar electrode is not particularly limited, but is preferably 0.02 to 0.6 mm, more preferably 0.04 to 0.6 mm. If the thickness of the bus bar electrode is less than 0.02 mm, the photogenerated carriers may not be sufficiently collected.

  The thickness of the finger electrode is not particularly limited, but is preferably 0.01 to 0.1 mm, more preferably 0.02 to 0.07 mm. If the thickness of the finger electrode is less than 0.01 mm, there is a possibility that photogenerated carriers cannot be collected sufficiently.

In the present invention, when the thickness of the bus bar electrode is different between the front surface side and the back surface side of the semiconductor substrate, the solar cell sealing is performed according to the formula (1) using the thickness of the bus bar electrode on the front surface side transparent protective member side. It is preferable to determine the basis weight thickness T _C of the film. Thereby, generation | occurrence | production of the crack in a semiconductor substrate can be suppressed more reliably.

  In general, the surface of the front surface side electrode and the back surface side electrode may be covered with solder in order to protect the electrode portion and make it easy to attach the connection tab. As a solder coating method, for example, a method of baking after applying a paste made of silver powder, glass frit, binder, solvent, etc. by screen printing or the like is used.

(Connection tab)
As the connection tab, one made of a rectangular copper foil or the like is used. The thickness of the connection tab may be about 0.15 to 1.0 mm. The entire surface of the connection tab is preferably provided with a solder coat of about 20 to 70 μm. Further, the width of the connection tab may be approximately the same as that of the bus bar electrode.

  The connection tab is electrically connected and wired between the solar cells by thermally welding the entire length or a plurality of locations of the back side bus bar electrode and the front side bus bar electrode with hot air or the like.

(Front side transparent protective member)
In the solar cell module of the present invention, fine uneven portions are formed on at least the solar cell side surface of the surface side transparent protective member in order to scatter light and lower the reflectance. By providing such fine uneven portions, an antiglare effect can be imparted to the solar cell module. In addition, by forming fine irregularities on the surface of the surface side transparent protective member on the solar cell side, contaminants from the external environment are prevented from adhering, and the appearance of the solar cell module and the photoelectric conversion efficiency are reduced. Can be suppressed. However, the formation of the fine concavo-convex portion is not limited only to the solar cell side surface of the surface side transparent protective member, and may be further formed on the light receiving surface side of the surface side transparent protective member.

  In order to form fine irregularities on the surface of the surface side transparent protective member, a conventionally known method may be used. For example, the surface of the glass substrate used for the surface side transparent protective member is directly provided with irregularities using a physical method or chemical method, and the glass substrate used for the surface side transparent protective member is provided with an irregular surface. A method of forming a diffuse reflection layer is used.

  Although it does not restrict | limit especially in order to form a fine uneven | corrugated | grooved part directly on the surface of a glass substrate, It can produce using methods, such as embossing, press work, and laser patterning. In addition, it can also be produced with reference to Japanese Patent Laid-Open No. 2001-358346.

  Moreover, the formation of the irregular reflection layer having an uneven surface on a glass substrate is made by, for example, applying a composition containing an organic binder and inorganic particles on a glass substrate, or applying a composition applied on another substrate to glass. This is done by depositing on a substrate.

  As the organic binder, an acrylic resin, a fluorine resin, a mixed resin thereof, or a resin mainly containing these resins or a mixed resin is used. As the inorganic particles, those made of silica such as glass beads are used.

  In addition, in this invention, when the thing in which the irregular reflection layer provided with the uneven surface on the glass substrate was used, the irregular reflection layer shall be contained in the surface side transparent protective member other than a glass substrate. Moreover, in such a case, after calculating | requiring the thickness of each of a glass substrate and a diffused reflection layer according to the method mentioned above, let the sum total of these thickness be the thickness of a surface side transparent protection member.

  In addition, in order to form a fine uneven part on the surface of the surface side transparent protective member, it is possible to easily form a fine uneven part having a desired shape, and therefore, the surface side transparent protective member is embossed. Is preferably formed.

  The basis thickness of the surface-side transparent protective member used in the solar cell module of the present invention is preferably 1 to 5 mm, more preferably 2 to 4 mm. If the weight per unit area is less than 1 mm, the wind pressure may cause breakage and damage.

The depth T _B of the minute uneven portion of the concave portion of the solar battery cell side surface of the surface-side transparent protective member, to preferably, of 0.02 to 0.5 mm, more preferably a 0.04~0.5mm Is good. The depth T _B is, there is a possibility that sufficient effect can not be obtained due to the provision of the minute uneven portion is less than 0.02 mm.

  The surface-side transparent protective member uses a glass substrate such as a slightly higher grade borosilicate glass such as Pyrex (registered trademark) or low alkali glass in addition to soda lime glass such as silicate glass, blue plate glass and white plate glass. Is good. When such a glass substrate is used, silicon oxide, sodium oxide, calcium oxide, or the like is a main component material used for forming the surface-side transparent protective part. Further, the glass substrate may generally be chemically or thermally strengthened.

(Back side protection member)
As the back surface side protection member, it is preferable to use a plastic film such as PET from the viewpoint of light weight and thinness and flexibility. Considering heat resistance, the back side protective member is preferably a fluorinated polyethylene film.

(Seal film for solar cell)
In this invention, if the sealing film used for the surface side and a back surface side is a well-known thing, it will not restrict | limit in particular. For example, a film obtained by depositing a composition containing an ethylene-polar monomer copolymer is preferably used.

  Examples of the ethylene-polar monomer copolymer include ethylene-acrylic acid copolymer, ethylene-unsaturated carboxylic acid copolymer such as ethylene-methacrylic acid copolymer, and carboxyl of the ethylene-unsaturated carboxylic acid copolymer. Ionomer partially or completely neutralized with the above metal, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-isobutyl acrylate copolymer Of ethylene-unsaturated carboxylic acid ester copolymer such as ethylene-n-butyl acrylate copolymer, ethylene-isobutyl acrylate-methacrylic acid copolymer, ethylene-n-butyl acrylate-methacrylic acid copolymer Ethylene-unsaturated carboxylic acid ester-unsaturated carboxylic acid copolymer and its Ionomer in which part or all of the carboxyl groups have been neutralized with the metal, ethylene - vinyl ester copolymer, and the like - ethylene such as vinyl acetate copolymer.

  Among these, the ethylene-polar monomer copolymer is most preferably an ethylene-vinyl acetate copolymer (EVA). Thereby, the sealing film for solar cells which is excellent in transparency and water resistance can be formed.

  In the sealing film used on the front side and the back side, the content of vinyl acetate in the ethylene-vinyl acetate copolymer is 5 to 50 parts by mass, particularly 100 parts by mass of the ethylene-vinyl acetate copolymer, It is preferable to set it as 10-40 mass parts. If the vinyl acetate content is less than 5 parts by mass, the transparency of the resin film obtained when crosslinked and cured at high temperatures may not be sufficient, and if it exceeds 50 parts by mass, acetic acid or the like may be easily generated. There is.

  In addition to the ethylene-polar monomer copolymer, polyvinyl acetal resins such as polyvinyl formal, polyvinyl butyral (PVB resin), and modified PVB, and a vinyl chloride resin may be used in combination as the sealing film. Although good, it is preferred to use only ethylene-polar monomer copolymers, especially ethylene-vinyl acetate copolymers.

  The sealing film for solar cells is obtained by forming a composition containing an ethylene-polar monomer copolymer, preferably an ethylene-vinyl acetate copolymer, according to a known method. In addition to the ethylene-vinyl acetate copolymer, the composition contains a crosslinking agent and various other additives as necessary.

  As the crosslinking agent used in the composition, an organic peroxide or a photopolymerization initiator is preferably used. Among them, it is preferable to use an organic peroxide because a sealing film having improved temperature dependency of adhesive strength, transparency, moisture resistance, and penetration resistance can be obtained.

  Any organic peroxide may be used as long as it decomposes at a temperature of 100 ° C. or higher and generates radicals. The organic peroxide is generally selected in consideration of the film formation temperature, the adjustment conditions of the composition, the curing temperature, the heat resistance of the adherend, and the storage stability. In particular, those having a decomposition temperature of 70 hours or more with a half-life of 10 hours are preferred.

  Examples of the organic peroxide include, from the viewpoint of resin processing temperature and storage stability, for example, benzoyl peroxide curing agent, tert-hexyl peroxypivalate, tert-butyl peroxypivalate, 3, 5, 5- Trimethylhexanoyl peroxide, di-n-octanoyl peroxide, lauroyl peroxide, stearoyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, succinic acid peroxide, 2,5-dimethyl-2,5-di (2-ethylhexanoylperoxy) hexane, 1-cyclohexyl-1-methylethylperoxy-2-ethylhexanoate, tert-hexylperoxy-2-ethylhexa Noate, 4-methylbenzoyl peroxide tert-butylperoxy-2-ethylhexanoate, m-toluoyl + benzoyl peroxide, benzoyl peroxide, 1,1-bis (tert-butylperoxy) -2-methylcyclohexanate, 1,1-bis (Tert-hexylperoxy) -3,3,5-trimethylcyclohexanate, 1,1-bis (tert-hexylperoxy) cyclohexanate, 1,1-bis (tert-butylperoxy) -3 , 3,5-trimethylcyclohexanate, 1,1-bis (tert-butylperoxy) cyclohexanate, 2,2-bis (4,4-di-tert-butylperoxycyclohexyl) propane, 1,1 -Bis (tert-butylperoxy) cyclododecane, tert-hexylperoxy Propyl monocarbonate, tert-butylperoxymaleic acid, tert-butylperoxy-3,3,5-trimethylhexanoate, tert-butylperoxylaurate, 2,5-dimethyl-2,5-di ( Methylbenzoylperoxy) hexane, tert-butylperoxyisopropyl monocarbonate, tert-butylperoxy-2-ethylhexyl monocarbonate, tert-hexylperoxybenzoate, 2,5-di-methyl-2,5-di (benzoyl) Peroxy) hexane, and the like.

  As the benzoyl peroxide-based curing agent, any one can be used as long as it decomposes at a temperature of 70 ° C. or higher to generate a radical, but preferably has a decomposition temperature of 50 ° C. or higher with a half-life of 10 hours. The temperature can be appropriately selected in consideration of the preparation conditions, the film formation temperature, the curing (bonding) temperature, the heat resistance of the adherend, and the storage stability. Usable benzoyl peroxide curing agents include, for example, benzoyl peroxide, 2,5-dimethylhexyl-2,5-bisperoxybenzoate, p-chlorobenzoyl peroxide, m-toluoyl peroxide, 2, Examples include 4-dichlorobenzoyl peroxide and t-butyl peroxybenzoate. The benzoyl peroxide curing agent may be used alone or in combination of two or more.

  In the composition, the content of the organic peroxide is preferably 0.1 to 2 parts by mass, more preferably 0.2 to 1.5 parts by mass with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer. Part. If the content of the organic peroxide is small, the transparency of the resulting sealing film may be lowered, and if it is increased, the compatibility with the copolymer may be deteriorated.

  As the photopolymerization initiator, any known photopolymerization initiator can be used, but a photopolymerization initiator having good storage stability after blending is desirable. Examples of such a photopolymerization initiator include 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, and 2-methyl-1- (4- (methylthio) phenyl). Acetophenones such as 2-morpholinopropane-1, benzoins such as benzyldimethylketal, benzophenones such as benzophenone, 4-phenylbenzophenone and hydroxybenzophenone, thioxanthones such as isopropylthioxanthone and 2-4-diethylthioxanthone, As other special ones, methylphenylglyoxylate can be used. Particularly preferably, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- (4- (methylthio) phenyl) -2-morpholinopropane-1, Examples include benzophenone. These photopolymerization initiators may contain one or two or more kinds of known and commonly used photopolymerization accelerators such as benzoic acid-based or tertiary amine-based compounds such as 4-dimethylaminobenzoic acid as required. Can be mixed and used. Moreover, it can be used individually by 1 type of only a photoinitiator, or 2 or more types of mixture.

  In the composition, the content of the photopolymerization initiator is preferably 0.5 to 5.0 parts by mass with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer.

  The composition is used for improving or adjusting various physical properties of the film (optical properties such as mechanical strength, adhesiveness, transparency, heat resistance, light resistance, crosslinking speed, etc.), particularly for improving mechanical strength. If necessary, various additives such as a crosslinking aid, an acid acceptor, a plasticizer, and an adhesion improver may be further included.

  The crosslinking aid can be added to the composition in order to improve the gel fraction of EVA and improve durability. As a crosslinking aid (compound having a radical polymerizable group as a functional group) used for this purpose, as well-known trifunctional crosslinking aids such as triallyl cyanurate and triallyl isocyanurate, ) Monofunctional or bifunctional crosslinking aids of acrylic esters (eg, NK esters, etc.) can also be mentioned. Of these, triallyl cyanurate and triallyl isocyanurate are preferable, and triallyl isocyanurate is particularly preferable. These crosslinking aids are generally used in an amount of 10 parts by mass or less, preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer.

  As the acid acceptor, a metal oxide, a metal hydroxide, a metal carbonate or a composite metal hydroxide is used, and can be appropriately selected according to the amount of acetic acid generated and the application. Specific examples of the acid acceptor include magnesium oxide, calcium oxide, magnesium hydroxide, calcium hydroxide, barium hydroxide, magnesium carbonate, barium carbonate, calcium carbonate, calcium borate, zinc stearate, calcium phthalate, Periodic table Group 2 metal oxides such as calcium phosphate, zinc oxide, calcium silicate, magnesium silicate, magnesium borate, magnesium metaborate, calcium metaborate, barium metaborate, hydroxide, carbonate, carvone Acid salts, silicates, borates, phosphites, metaborate, etc .; tin oxide, basic tin carbonate, tin stearate, basic tin phosphite, basic tin sulfite, trilead tetraoxide, silicon oxide, stearin Group 14 metal oxides such as silicon acid, basic carbonate, basic carboxylate, base Phosphites, and basic sulfite salt; zinc oxide, aluminum oxide, aluminum hydroxide, iron hydroxide; composite metal hydroxide such as hydrotalcite; aluminum hydroxide gel compound; and the like. These may be used individually by 1 type, and may mix and use 2 or more types.

  In the composition, the content of the acid acceptor is preferably 0.01 to 0.15 parts by mass with respect to 100 parts by mass of the ethylene vinyl acetate copolymer.

  The plasticizer is not particularly limited, but polybasic acid esters and polyhydric alcohol esters are generally used. Examples thereof include dioctyl phthalate, dihexyl adipate, triethylene glycol-di-2-ethylbutyrate, butyl sebacate, tetraethylene glycol diheptanoate, and triethylene glycol dipelargonate. One type of plasticizer may be used, or two or more types may be used in combination. The content of the plasticizer is preferably in the range of 5 parts by mass or less with respect to 100 parts by mass of EVA.

  As the adhesion improver, a silane coupling agent can be used. Examples of the silane coupling agent include γ-chloropropylmethoxysilane, vinylethoxysilane, vinyltris (β-methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, γ-glycidoxypropyltri Methoxysilane, γ-glycidoxypropyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, vinyltrichlorosilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N- Mention may be made of β- (aminoethyl) -γ-aminopropyltrimethoxysilane. These silane coupling agents may be used alone or in combination of two or more. Moreover, it is preferable that content of the said adhesive improvement agent is 5 mass parts or less with respect to 100 mass parts of EVA.

  Further, the composition may contain an ultraviolet absorber, a light stabilizer and an anti-aging agent.

  The ultraviolet absorber is not particularly limited, but 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-n-dodecyloxybenzophenone, 2,4-dihydroxybenzophenone, 2,2′-dihydroxy-4- Preferred examples include benzophenone-based ultraviolet absorbers such as methoxybenzophenone and 2-hydroxy-4-n-octoxybenzophenone. In addition, it is preferable that the compounding quantity of the said benzophenone series ultraviolet absorber is 0.01-5 mass parts with respect to 100 mass parts of ethylene-vinyl acetate copolymers.

  As the light stabilizer, a light stabilizer called a hindered amine type is preferably used. For example, LA-52, LA-57, LA-62, LA-63LA-63p, LA-67, LA-68 (all Asahi Denchu Co., Ltd.), Tinuvin 744, Tinuvin 770, Tinuvin 765, Tinuvin 144, Tinuvin 622LD, CHIMASSORB 944LD (all manufactured by Ciba-Geigy), UV-3034 (manufactured by BF Goodrich), and the like. it can. In addition, the said light stabilizer may be used individually or may be used in combination of 2 or more types, and the compounding quantity is 0.01-5 mass parts with respect to 100 mass parts of ethylene-vinyl acetate copolymers. It is preferable that

  Examples of the antioxidant include hindered phenol antioxidants such as N, N′-hexane-1,6-diylbis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionamide]. , Phosphorus heat stabilizers, lactone heat stabilizers, vitamin E heat stabilizers, sulfur heat stabilizers, and the like.

  The above-mentioned composition can produce the sealing film for solar cells of this invention according to a conventional method, for example, forming into a film by heat-rolling using extrusion molding or calendar molding. Heating is generally in the range of 50-90 ° C.

  The surface of the solar cell sealing film may be provided with cushioning properties by providing fine irregularities using a conventionally known method such as embossing. However, in the method of the present invention, the occurrence of cracks in the semiconductor substrate can be highly suppressed without going through other processing steps such as embossing.

The solar cell module of this invention is obtained by sealing the cell for solar cells through the sealing film for solar cells between the surface side transparent protection member and the back surface side protection member. In order to sufficiently seal the solar cell, as shown in FIG. 1, the front surface side transparent protective member 1, the front surface side sealing film 3A, the solar cell cell 4, the back surface side sealing film 3B, and the back surface side protective member. 2 may be laminated, and the laminated body may be heat-pressed with a vacuum laminator in accordance with a conventional method. The temperature during the thermocompression bonding is preferably 135 to 180 ° C, more preferably 140 to 180 ° C, and particularly preferably 155 to 180 ° C. The deaeration time may be about 0.1 to 5 minutes. The pressing pressure is preferably about 0.1 to 1.5 kg / cm ² and the pressing time is preferably about 5 to 15 minutes.

  By heating and pressurizing, the ethylene-vinyl acetate copolymer contained in the front surface side sealing film and the rear surface side sealing film is cross-linked so that the surface side transparent film is passed through the front surface side sealing film and the rear surface side sealing film. The protective member, the back surface side transparent member, and the solar cell can be integrated to seal the solar cell.

  In addition, the solar cell of this invention determines the thickness of the sealing film for solar cells so that the said Formula (1) may be satisfy | filled as above-mentioned. Accordingly, the front-side transparent protective member, the back-side protective member, the solar cell sealing film, the solar cell, and the like have been described above with a preferred embodiment, but are the same as those of conventionally known solar cell modules. There is no particular limitation as long as it has the following configuration.

  Hereinafter, the present invention will be described with reference to examples. The present invention is not limited by the following examples.

Example 1
1. Production of solar battery cell A silicon power generation element (size: 125 mm × 125 mm, thickness: 0.18 mm) as a semiconductor substrate is coated with silver powder, an organic vehicle, and a glass frit on each of 100 parts by weight of silver. The silver paste added to 20 parts by weight and 3 parts by weight to form a paste was applied by screen printing and dried, and then baked at 750 ° C. for 15 minutes. As a result, as shown in FIG. 2, bus bar electrodes (thickness 0.40 mm, width 2 mm) and finger electrodes (thickness 0.05 mm, width 0.1 mm) are produced on the front and back sides of the silicon power generation element. did.

  Using Sn-3Ag-0.5Cu Pb-free solder, solder resist is printed on the end of the bus bar electrode as a coating and dried, and then solder is applied to the entire surface of the bus bar electrode and finger electrode by the dipping method. It coat | covered and the photovoltaic cell was produced.

2. Next, 100 parts by weight of EVA (vinyl acetate content is 28 parts by weight with respect to 100 parts by weight of EVA), 2 parts by weight of a crosslinking agent, 2 parts by weight of a crosslinking aid, and additive 0 0.5 parts by mass was supplied to a roll mill and kneaded at 80 ° C. to prepare a composition. The obtained composition was calendered at 100 ° C., allowed to cool, and then a sealing film (size 300 mm × 300 mm, basis weight 1.0 mm) was obtained. In addition, the following were used as a crosslinking agent, a crosslinking assistant, and an additive.

Crosslinking agent: 1,1-bis (t-butylperoxy) trimethylcyclohexane Crosslinking assistant: triallyl isocyanurate Additive: γ-methacryloxypropyltrimethoxysilane

3. Production of surface-side transparent protective member Glass plate (T _B 0.05 mm) in which fine irregularities are formed on the solar cell side surface by embossing a glass plate (size 300 mm × 300 mm, thickness 3 mm) Got.

4). Fabrication of solar cell module A connection tab made of copper foil having a width of 3 mm and a thickness of 300 μm provided with a solder layer (thickness of 50 μm) is attached by hot air thermal welding over the entire length of each bus bar electrode on the front side and the back side. As shown in FIG. 1, the above-mentioned solar cells were connected and wired.

  After that, as shown in FIG. 1, the solar cell connected and wired between the front surface side transparent protective member and the back side protective material made of a fluorinated polyethylene film (size 300 mm × 300 mm). After laminating so as to enter, a solar cell module was manufactured by sealing.

For the sealing, the laminate produced as described above was put into a vacuum laminator having a hot plate temperature of 130 ° C., degassed for 5 minutes, and then pressed at a pressure of 1 kgf / cm ² for 5 minutes. This was done by crosslinking EVA.

  100 solar cells were produced as described above, but no damage such as generation of cracks in the semiconductor substrate was observed. The results are summarized in Table 1.

(Example 2, Comparative Examples 1 and 2)
Except having made the thickness of a bus-bar electrode, the depth of the recessed part in the glass substrate of a surface side transparent protective member, and the fabric weight of the sealing film for solar cells as shown in Table 1, it carried out similarly to Example 1, and having carried out. A solar cell module was fabricated and examined for damage to the semiconductor substrate. The results are summarized in Table 1.

  In the above examples, the thickness of each member was measured according to the following method.

(Measuring method)
1. Solar cell sealing film thickness T _C
The weight W ₁ of the solar cell sealing film cut to a size of 10 cm × 10 cm was measured using a precision balance with an accuracy of 1/100 g, and the specific gravity D ₁ of W ₁ and EVA (0.95 g / cm ³ ) Was used to calculate the basis weight thickness T _C (mm) of the solar cell sealing film from the above formula (A).

2. The thickness T _A of the bus bar electrode and the thickness of the semiconductor substrate The thickness of the bus bar electrode was measured using a surface measuring device (Surfcom 300B manufactured by Tokyo Seimitsu Co., Ltd.). Moreover, the thickness of the semiconductor substrate was measured using a surface measuring device (manufactured by Mitutoyo Corporation, dial gauge 2046SB).

3. The depth T _B of the recess of the minute uneven portion of the solar cell side surface of the surface-side transparent protective member
First, the weight W ₂ of the surface-side transparent protective member cut to a size of 10 cm × 10 cm was measured using a precision balance with an accuracy of 1/100 g, and W ₂ and the specific gravity D _{2 of the} glass plate (2.5 g / cm ³ ) was used to calculate the basis weight thickness T _B1 (mm) of the surface side transparent protective member from the above formula (B).

Then, the apparent surface side transparent protective member thickness T _B2 (unit: mm) and surface measuring apparatus (manufactured by Mitutoyo dial gauge 2046SB) was used for the measurement. Then, using the basis thickness T _B1 of the surface-side transparent protective part and the apparent thickness T _B2 of the surface-side transparent protective member, according to the above formula (C), the surface of the surface-side transparent protective member on the solar cell side surface The depth T _B (unit: mm) of the recess was determined.

  From Table 1, it can be seen that according to the present invention, even if a semiconductor substrate having a small thickness is used in the solar battery cell, damage due to cracks, cracks, etc. of the semiconductor substrate in the sealing process can be prevented to a high degree. In addition, a high effect of preventing damage to the semiconductor substrate can be obtained without performing a separate process such as embossing the solar cell sealing film.

It is a figure which shows the structure of the cross section of a solar cell module. It is a figure which shows an example of the shape of the electrode of a photovoltaic cell. It is a figure which shows an example of the shape of the electrode of a photovoltaic cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Front side transparent protective member, 12 ... Back side transparent protective member, 13a ... Front side sealing film, 13b ... Back side sealing film, 14 ... Solar cell, 15 ... Semiconductor substrate, 16 ... Front side electrode, 17 ... back side electrode, 18 ... connection tab, 19a ... bus bar electrode, 19b ... finger electrode, 20a ... back side bus bar electrode, 20b ... back side current collecting electrode.

Claims (11)

Between the front surface side transparent protective member and the back surface side protective member, a plurality of solar cells comprising a semiconductor substrate and bus bar electrodes provided on the front surface side and the back surface side through a solar cell sealing film A solar cell module formed by sealing,
The surface-side transparent protective member has a fine uneven portion on at least the solar cell side surface,
Basis weight thickness T _C of the sealing film wherein the solar cell, the following equation (1):

[In Formula (1), T _C represents the basis weight thickness (unit: mm) of the solar cell sealing film, T _A represents the thickness (unit: mm) of the bus bar electrode, and T _B represents the above It represents the depth (unit: mm) of the concave portion of the fine uneven portion, and a is an integer of 0.2 or more. ] A solar cell module characterized by satisfying   The solar cell module according to claim 1, wherein a in the formula (1) is 0.3 or more.   The solar cell module according to claim 1, wherein a in the formula (1) is 1 or less.   The thickness of the said semiconductor substrate is 0.01-0.5 mm, The solar cell module of any one of Claims 1-3 characterized by the above-mentioned. The thickness T _A of the bus bar electrode, the solar cell module according to claim 1, characterized in that the 0.02～0.6Mm.   The solar cell module according to any one of claims 1 to 5, wherein the fine uneven portion is provided by embossing the surface-side transparent protective member. The solar cell module according to any one of claims 1 to 6, wherein the depth T _B of the recess of the minute uneven portion, is of 0.02 to 0.5 mm.   The solar cell module according to claim 1, wherein the surface-side transparent protective member is made of a glass substrate.   The solar cell module according to any one of claims 1 to 8, wherein the back surface side protection member is made of a plastic film.   The solar cell module according to any one of claims 1 to 9, wherein the solar cell sealing film is a film obtained by forming a composition containing an ethylene-vinyl acetate copolymer. The solar cell module according to claim 10, wherein a content of vinyl acetate in the ethylene-vinyl acetate copolymer is 5 to 50 parts by mass with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer.

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