JP6175935B2 - Solar cell connection material, solar cell module using the same, and manufacturing method thereof - Google Patents

Description

  The present invention relates to a solar cell connection material, a solar cell module using the same, and a method for manufacturing the solar cell module.

  In recent years, a solar cell that can directly convert light from the sun, which is a clean and inexhaustible energy source, into electricity has attracted attention as a new environmentally friendly energy source. Although the output per solar cell is only a few W at most, it is possible to increase the output to 100 W or more by connecting a plurality of solar cells in series. For this reason, the solar cell is generally used as a solar cell module in which a plurality of cells are connected in series. The solar cell module has a configuration in which electrodes formed on a plurality of solar cells are electrically joined to each other by a wiring member (tab wire) made of a metal conductive material.

  Conventionally, as the tab wire, one having a solder layer formed on the surface of a copper wire has been used. The solder on the surface of the copper wire and the electrode (bus bar electrode) made of silver (Ag) formed on the solar battery cell are melted at a high temperature and solder-connected to electrically connect a plurality of solar battery cells. Has achieved.

  Generally, solder containing lead (Pb) is used for solder connection because thermocompression bonding at 200 ° C. or less is possible. On the other hand, in consideration of lead (Pb) being an environmental pollutant, use of solder containing no lead (Pb) is being studied. However, when using solder that does not contain lead (Pb), a thermocompression bonding temperature of about 240 ° C. is required, and stress is generated between the solar battery cell and the tab wire. In particular, when a thin silicon wafer is used, the solar cell may be warped or cracked due to the influence of thermal stress.

  With the spread of solar cells and the need to reduce costs by reducing production costs and production volumes, silicon wafers are becoming thinner to reduce the price of silicon wafers used in solar cells. It is out. As the thinning of the silicon wafer progresses, the influence of the thermal stress as described above increases, so that it is required to connect the tab wire and the bus bar electrode at a relatively low temperature.

  Therefore, in recent years, a method of electrically connecting the tab wire and the bus bar electrode with a conductive adhesive containing resin instead of solder connection has been intensively studied (see, for example, Patent Documents 1 and 2).

JP 2008-135654 A JP 2009-302327 A

  By the way, many of the conductive adhesives used for the method replacing solder connection have a composition using an epoxy resin, an acrylic resin or the like in order to enable thermocompression bonding at a relatively low temperature. In the future, when the silicon wafer is further thinned, it is required to be thermocompression bonded under the condition of about 160 ° C. Under this condition, the reaction rate of the epoxy resin is low. Therefore, a reliability test (heat cycle test) that raises and lowers the temperature repeatedly between −40 ° C. and 100 ° C., assuming that it is used in an outdoor environment, with a conductive adhesive having a composition using a conventional epoxy resin. ) May reduce the connection reliability. Further, as a result of studies by the present inventors, it has been found that the connection reliability in the heat cycle test is greatly reduced in the joining by the thermocompression bonding using the conductive adhesive having the composition using the conventional acrylic resin.

  In solar cell modules, it is known that a phenomenon referred to as a partial high temperature phenomenon (hot spot phenomenon) is induced by defects of solar cells (for example, cracks, poor internal connection, shading contamination, etc.). The hot spot portion is said to easily exceed 150 ° C., and the solar cell module is required to have resistance to the hot spot phenomenon.

  The object of the present invention is to solve the above-described problems in the prior art, and even when the electrode and the wiring member are connected at a relatively low temperature (for example, about 160 ° C.), before and after the heat cycle test. It is an object of the present invention to provide a solar cell connection material excellent in connection reliability that can sufficiently suppress a decrease in connection reliability. Another object of the present invention is to provide a solar cell module excellent in connection reliability and a method for manufacturing the same, in which a decrease in connection reliability before and after a heat cycle test is sufficiently suppressed even when connected at a relatively low temperature. It is to be.

  The present invention is a solar cell connection material for connecting an electrode and a wiring member, and the storage elasticity of a cured product obtained by heating the solar cell connection material at 180 ° C. for 40 seconds at 20 to 150 ° C. A solar cell connection material having a rate reduction ratio of 80% or less and a tan δ peak temperature of 150 ° C. or more is provided.

  According to such a solar cell connection material, even when the electrode and the wiring member are connected at a relatively low temperature, a decrease in connection reliability before and after the heat cycle test can be sufficiently suppressed.

  The solar cell connection material contains, for example, (A) an acrylic resin including a structural unit having a (meth) acryloyl group in the side chain, (B) a thermal polymerization initiator, and (C) conductive particles. be able to.

  In the present invention, the solar cell connection material according to the present invention is interposed between an electrode formed on the main surface of the solar cell and a wiring member that electrically connects the plurality of solar cells. There is provided a method for manufacturing a solar cell module, comprising the step of pressurizing the electrode and the wiring member so that the electrode and the wiring member are electrically connected.

  According to such a solar cell module manufacturing method, since the solar cell connection material according to the present invention is used, a solar cell module excellent in connection reliability in which a decrease in connection reliability before and after the heat cycle test is sufficiently suppressed. Can be obtained. In addition, according to the method for manufacturing a solar cell module of the present invention, the electrode and the wiring member can be connected at a relatively low temperature, so the influence of thermal stress on the members constituting the solar cell module such as solar cells. Can be reduced.

  The present invention also includes a solar cell in which an electrode is formed on the main surface, a wiring member that electrically connects the plurality of solar cells, and a connection portion that is interposed between the electrode and the wiring member, A solar cell module in which the connecting portion is made of a cured product of resin, the reduction rate of the storage modulus at 20 to 150 ° C. of the cured product is 80% or less, and the peak temperature of tan δ of the cured product is 150 ° C. or more. provide.

  Such a solar cell module can be manufactured by using the solar cell connection material according to the present invention. In this solar cell module, a decrease in connection reliability before and after the heat cycle test is sufficiently suppressed, and the solar cell module has excellent connection reliability.

  According to the present invention, even when the electrode and the wiring member are connected at a relatively low temperature, a decrease in connection reliability before and after the heat cycle test can be sufficiently suppressed, and the solar cell excellent in connection reliability. A connecting material can be provided. According to the present invention, there is also provided a solar cell module excellent in connection reliability, in which a decrease in connection reliability before and after a heat cycle test is excellent even when connected at a relatively low temperature, and a method for manufacturing the same. Can do.

It is a schematic diagram which shows the principal part of one Embodiment of the solar cell module of this invention, (a) is the surface view, (b) is a bottom view, (c) is the side view. It is a schematic diagram for demonstrating one Embodiment of the solar cell module of this invention. It is a figure which shows the measurement result of the storage elastic modulus E 'in an Example. It is a figure which shows the measurement result of the loss elastic modulus E '' in an Example.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings as necessary. However, the present invention is not limited to the following embodiments. In addition, the dimension ratio of drawing is not restricted to the illustrated ratio. In the present specification, “(meth) acrylate” means “acrylate” and its corresponding “methacrylate”, and “(meth) acryloyl group” means “acryloyl group” and its corresponding “methacryloyl group”. "Means. The same applies to other terms similar to these. “EO-modified” means a compound having a (poly) oxyethylene chain, and “PO-modified” means a compound having a (poly) oxypropylene chain. “ECH modification” means epichlorohydrin modification.

  The solar cell connection material according to the present embodiment is for connecting an electrode and a wiring member, and more specifically, a tab wire for connecting a plurality of solar cells in series and / or in parallel. It is for electrically connecting (wiring member) and the electrode which comprises a photovoltaic cell.

  In the solar cell connection material according to the present embodiment, the reduction rate of the storage elastic modulus at 20 to 150 ° C. of the cured product obtained by heating at 180 ° C. for 40 seconds is 80% or less, preferably 75% or less. Yes, more preferably 70% or less. The lower limit of the reduction rate of the storage elastic modulus is not particularly limited, but is, for example, 95% or more. Moreover, the solar cell connecting material according to the present embodiment has a peak temperature of tan δ of a cured product obtained by heating at 180 ° C. for 40 seconds, 150 ° C. or higher, preferably 160 ° C. or higher, more preferably It is 170 ° C or higher. The upper limit of the tan δ peak temperature is not particularly limited, but is, for example, 250 ° C. or lower.

  The peak temperatures of the storage elastic modulus and tan δ are those in a cured product obtained under curing conditions of heating at 180 ° C. for 40 seconds, but curing proceeds sufficiently even when other curing conditions are used. If it does, the hardened | cured material which has comparable storage elastic modulus and the peak temperature of tan-delta can be obtained.

The connection material for solar cells in this embodiment contains, for example, (A) an acrylic resin including a structural unit having a (meth) acryloyl group in the side chain, (B) a thermal polymerization initiator, and (C) conductive particles. It can be a thing, but it is not limited to this. For example, by using a resin having a high glass transition temperature (for example, a polyimide resin) or by using an epoxy resin or the like to obtain a high crosslinking density, the reduction rate of the storage elastic modulus and the peak temperature of tan δ are set to be predetermined. obtain.
Hereinafter, (A) an acrylic resin having a structural unit having a (meth) acryloyl group in the side chain (hereinafter, also simply referred to as “(A) acrylic resin”), (B) a thermal polymerization initiator, and (C) conductivity. A solar cell connection material containing particles (hereinafter also simply referred to as “connection material”) will be described.

  (A) The acrylic resin may be one obtained by homopolymerizing one kind of (meth) acrylate, or may be one obtained by copolymerizing two or more kinds of (meth) acrylate. Furthermore, the (A) acrylic resin may be a copolymer of (meth) acrylate and another monomer. However, when (A) the acrylic resin is a copolymer with another monomer, it is preferable to blend the monomer so that the (meth) acrylate is 30% by mass or more.

  (A) Acrylic resin is provided with the structural unit which has (a1) (meth) acryloyl group in a side chain. (A1) The structural unit having a (meth) acryloyl group in the side chain is, for example, a functional group that reacts with a hydroxyl group or a carboxyl group with respect to an acrylic resin having a hydroxyl group or a carboxyl group in the side chain (for example, an isocyanate group or a glycidyl group). ) And the above-mentioned (meth) acryloyl group-containing compound can be introduced. The (meth) acryloyl group reacts with an acrylic resin having an isocyanate group in the side chain by reacting a compound having a functional group (for example, a hydroxyl group) that reacts with the isocyanate group and the (meth) acryloyl group. It can also be introduced by reacting an acrylic resin having a glycidyl group in the side chain with a compound having a functional group that reacts with the glycidyl group (for example, a carboxyl group) and the above (meth) acryloyl group. can do.

  Acrylic resins having a hydroxyl group in the side chain are 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, glycerol mono (meth) ) It can be obtained by polymerizing (meth) acrylate having a hydroxyl group such as acrylate. It can also be obtained by copolymerizing a monomer such as 4-hydroxyvinylbenzene with (meth) acrylate.

  The acrylic resin having a carboxyl group in the side chain is a (meth) acrylate having a carboxyl group such as (meth) acrylic acid, 2- (meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyloxyethyl hexahydrophthalic acid, etc. Is obtained by polymerizing.

  The acrylic resin having an isocyanate group in the side chain is obtained by polymerizing (meth) acrylate having an isocyanate group such as 2- (2- (meth) acryloyloxyethyloxy) ethyl isocyanate and 2- (meth) acryloyloxyethyl isocyanate. It is obtained by.

  The acrylic resin having a glycidyl group in the side chain can be obtained by polymerizing a (meth) acrylate having a glycidyl group such as glycidyl (meth) acrylate or methyl glycidyl (meth) acrylate.

  (Meth) acrylate etc. which were illustrated as a monomer which can be used in order to obtain the acrylic resin which has an isocyanate group in the said side chain as a compound provided with the functional group and the said (meth) acryloyl group which react with the said hydroxyl group are used. Can do.

  (Meth) acrylate etc. which were illustrated as a monomer which can be used in order to obtain the acrylic resin which has a glycidyl group in the said side chain as a compound provided with the functional group and the said (meth) acryloyl group which react with the said carboxyl group are used. be able to.

  (Meth) acrylate etc. which were illustrated as a monomer which can be used in order to obtain the acrylic resin which has a hydroxyl group in the said side chain as a compound provided with the functional group and said (meth) acryloyl group which react with the said isocyanate group are used. Can do.

  As the compound having a functional group that reacts with the glycidyl group and the (meth) acryloyl group, (meth) acrylate exemplified as a monomer that can be used to obtain an acrylic resin having a carboxyl group in the side chain is used. be able to.

  These monomers and compounds can be used singly or in combination of two or more.

  The acrylic resin preferably further comprises (a2) a structural unit derived from a monomer having a (meth) acryloyl group from the viewpoints of improving thermal stability and improving connection reliability. The monomer having a (meth) acryloyl group is not particularly limited as long as it is a monomer having one or more (meth) acryloyl groups (excluding those having a hydroxyl group). (Meth) acrylic acid 2- (meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyloxyethyl hexahydrophthalic acid, aliphatic (meth) acrylate, alicyclic (meth) acrylate, (alkoxyalkyl) acrylate, aromatic (meta ) Phosphoric acid acrylates such as acrylate and 2-methacryloyloxyethyl acid phosphate.

  Aliphatic (meth) acrylates include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. , Isodecyl (meth) acrylate, n-lauryl (meth) acrylate, alkyl (meth) acrylate [alkyl chain C12-C15], n-stearyl (meth) acrylate, and the like.

  As alicyclic (meth) acrylates, (meth) acrylates having a cycloalkyl group such as cyclopentanyl (meth) acrylate; cycloalkenyls such as dicyclopentenyl (meth) acrylate and dicyclopentenyloxyethyl (meth) acrylate (Meth) acrylate having a group; cyclic monomer having a bornyl group (endo-1,7,7-trimethylbicyclo [2.2.1] hept-2-yl group) (such as bornyl (meth) acrylate), isobornyl An alicyclic moiety such as a cyclic monomer (such as isobornyl (meth) acrylate) having a group (exo-1,7,7-trimethylbicyclo [2.2.1] hept-2-yl group) is a bicycloalkyl group (Meth) acrylate; (meth) acrylate in which the alicyclic portion is a tricycloalkyl group; alicyclic portion Examples include (meth) acrylates whose minutes are tricycloalkenyl groups.

The (meth) acrylate having a tricycloalkyl group, a tricyclo group, tricyclo [5.2.1.0 ^{2, 6]} One hydrogen atom decane consisting been removed tricyclo [5.2.1.0 ^{2 , 6} ] (meth) acrylate having a decanyl group. Examples of the (meth) acrylate having a tricycloalkenyl group include tricyclo [5.2.1.0 ^2,6 ] -3-decene (tricyclo [5.2.1.0 ^2,6 ] -dec-3-ene. (Meth) acrylate having a tricyclo [5.2.1.0 ^2,6 ] -3-decenyl group (also referred to as a dicyclopentenyl group) formed by removing one hydrogen atom from Here, the above-exemplified tricycloalkyl group or tricycloalkenyl group is preferably bonded to the (meth) acryloyl group via —O— or —O—R—O— (R is an alkylene group). . Specific examples include acryloyloxytricyclo [5.2.1.0 ^2,6 ] decane (manufactured by Hitachi Chemical Co., Ltd., FANCYL FA-513A), methacryloyloxytricyclo [5.2.1.0 ^2,6. ] (Meth) acryloyloxytricyclo [5.2.1.0 ^2,6 ] decane such as decane (manufactured by Hitachi Chemical Co., Ltd., FANCYL FA-513M), acryloyloxytricyclo [5.2.1.0 ^{2 , 6} ] -dec-3-ene (manufactured by Hitachi Chemical Co., Ltd., FANCYL FA-511A) and other (meth) acryloyloxytricyclo [5.2.1.0 ^2,6 ] -dec-3-ene, acryloyl oxyethyl oxy tricyclo [5.2.1.0 ^2,6] -3- decene (manufactured by Hitachi Chemical Co., Ltd., FANCRYL FA-512A) such (meth) acryloyloxy Alkyloxy tricyclo [5.2.1.0 ^2,6] - such as deca-3-ene.

  (Alkoxyalkyl) acrylates include n-butoxyethyl (meth) acrylate, butoxydiethylene glycol (meth) acrylate, methoxytriethylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, and the like.

  Examples of the aromatic (meth) acrylate include benzyl (meth) acrylate and phenoxyethyl (meth) acrylate.

  Each of these monomers can be used alone or in combination of two or more.

  The acrylic resin preferably further comprises (a3) a structural unit derived from a (meth) acrylate monomer having a hydroxyl group from the viewpoint of improving the adhesion to electrodes, wiring members and the like. As the (meth) acrylate monomer having a hydroxyl group, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, glycerol mono ( And (meth) acrylate.

  These monomers and compounds can be used singly or in combination of two or more.

  The acrylic resin preferably further comprises a structural unit derived from (a4) N-substituted maleimide from the viewpoint of further improving the thermal stability. Examples of the N-substituted maleimide include N-substituted alkylmaleimide, N-substituted cyclohexylmaleimide, and N-substituted phenylmaleimide.

  Each of these monomers can be used alone or in combination of two or more.

  (A) The acrylic resin may include structural units other than those shown in the above (a1) to (a4). Examples of the monomer giving such a structural unit include aromatic vinyl monomers such as styrene and α-methylstyrene, and vinyl cyanide monomers such as acrylonitrile and methacrylonitrile.

(A1) The proportion of the structural unit having a (meth) acryloyl group in the side chain in the (A) acrylic resin is indicated by a double bond equivalent. The double bond equivalent is defined by the following formula and is a measure of the amount of double bonds contained in a molecule. For acrylic resins having the same molecular weight, the smaller the double bond equivalent value, the greater the amount of (meth) acryloyl group introduced into the side chain.
“Double bond equivalent” = “Molecular weight of one molecule of acrylic resin” / “Number of double bonds”
(A) It is preferable that the double bond equivalent of an acrylic resin is 50-5000, and it is preferable that it is 100-4500. By setting the double bond equivalent to 50 or more, the crosslinking density can be made moderate, the connection portion can be prevented from becoming brittle after curing, and the deterioration of the adhesion to the substrate or the like can be suppressed. Moreover, sufficient heat resistance and a required elasticity modulus can be obtained by setting it as 5000 or less.

  (A1) The content of the structural unit having a (meth) acryloyl group in the side chain is preferably 1 to 50% by mass based on the total mass of the monomers constituting the (A) acrylic resin, and 3 to 40 More preferably, it is mass%. By setting the content to 1% by mass or more, a sufficient crosslinking density after curing can be obtained. By setting it to 50% by mass or less, weakening after curing can be suppressed.

  When (A2) the acrylic resin includes a structural unit derived from a monomer having (a2) (meth) acryloyl group and / or a structural unit derived from (a4) N-substituted maleimide, the total content is (A ) It is preferably 30 to 97% by mass, more preferably 40 to 95% by mass, based on the total mass of monomers constituting the acrylic resin. Sufficient heat resistance can be obtained by setting it as 30 mass% or more. By setting it as 97 mass% or less, an elasticity modulus can be made more sufficient.

  (A3) When (A) acrylic resin is provided with a structural unit derived from a (meth) acrylate monomer having a hydroxyl group, (a3) the content of the structural unit derived from the (meth) acrylate monomer having a hydroxyl group is (A) The amount is preferably 3 to 50% by mass, more preferably 5 to 40% by mass, based on the total mass of monomers constituting the acrylic resin. By setting it as 3 mass% or more, the further outstanding adhesiveness to an electrode, a wiring member, etc. can be obtained. By setting it to 50% by mass or less, the elastic modulus can be made more sufficient.

  (A) As for the weight average molecular weight of an acrylic resin, 3000-500000 are preferable from viewpoints of the characteristic of a coating film, etc., and it is more preferable that it is 5000-400000. By setting the weight average molecular weight to 3000 or more, an appropriate elastic modulus can be obtained. Moreover, the viscosity suitable for film formation is obtained. By setting it as 500,000 or less, it is possible to suppress the handling property from being lowered when the viscosity is too high to form a film. In addition, the measurement conditions of a weight average molecular weight shall be the same measurement conditions as the Example of this-application specification.

  (A) It is preferable that it is 10-80 mass% with respect to the whole connection material which concerns on this embodiment, and, as for content of an acrylic resin, it is more preferable that it is 20-60 mass%. By setting the content to 10% by mass or more, a sufficient elastic modulus can be obtained when the film is formed. Adhesiveness can be improved more by setting it as 80 mass% or less.

  (B) A thermal polymerization initiator refers to a compound that decomposes by heat to generate free radicals. (B) The thermal polymerization initiator is appropriately selected according to the intended connection temperature, connection time, pot life, etc., but from the viewpoint of high reactivity and pot life, the 10-hour half-life temperature is 40 ° C. or higher. An organic peroxide having a 1 minute half-life temperature of 180 ° C. or lower is preferred. Specific examples include diacyl peroxides, peroxydicarbonates, peroxyesters, peroxyketals, dialkyl peroxides, hydroperoxides and the like.

  Diacyl peroxides include isobutyl peroxide, 2,4-dichlorobenzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, lauroyl peroxide, stearoyl peroxide, succinic peroxide, Examples include benzoyl peroxytoluene and benzoyl peroxide.

  Peroxydicarbonates include di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, bis (4-t-butylcyclohexyl) peroxydicarbonate, di-2-ethoxymethoxyperoxydicarbonate, di- (2-Ethylhexylperoxy) dicarbonate, dimethoxybutylperoxydicarbonate, di (3-methyl-3-methoxybutylperoxy) dicarbonate and the like.

  Peroxyesters include cumylperoxyneodecanoate, 1,1,3,3-tetramethylbutylperoxyneodecanoate, 1-cyclohexyl-1-methylethylperoxyneodecanoate, t- Hexyl peroxyneodecanoate, t-butyl peroxypivalate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, 2,5-dimethyl-2,5-bis (2 -Ethylhexanoylperoxy) hexane, 1-cyclohexyl-1-methylethylperoxy-2-ethylhexanoate, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexa Noate, t-butylperoxyisobutyrate, 1,1-bis (t-butylperoxy) cyclohexa , T-hexylperoxyisopropyl monocarbonate, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate, 2,5-dimethyl-2,5-bis (m-toluene) Oil peroxy) hexane, t-butyl peroxyisopropyl monocarbonate, t-butyl peroxy-2-ethylhexyl monocarbonate, t-hexyl peroxybenzoate, t-butyl peroxyacetate and the like.

  Peroxyketals include 1,1-bis (t-hexylperoxy) -3,5,5-trimethylcyclohexane, 1,1-bis (t-hexylperoxy) cyclohexane, 1,1-bis (t -Butylperoxy) -3,5,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclododecane, 2,2-bis (t-butylperoxy) decane and the like.

  Dialkyl peroxides include α, α′-bis (t-butylperoxy) diisopropylbenzene, dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, t- Examples thereof include butyl cumyl peroxide.

  Examples of hydroperoxides include diisopropylbenzene hydroperoxide and cumene hydroperoxide.

  The above thermal polymerization initiator can be used individually by 1 type or in mixture of 2 or more types. The thermal polymerization initiator may be used by mixing a decomposition accelerator, an inhibitor and the like.

  (B) It is preferable that content of a thermal-polymerization initiator is 1-10 mass% with respect to the whole connection material which concerns on this embodiment. By setting the content to 1% by mass or more, the connection material can be sufficiently cured. By setting the content to 10% by mass or less, the pot life of the connection material can be secured for a sufficient time.

  (C) As electroconductive particle, if it is the material which shows electroconductivity, when it connects, it will not specifically limit. For example, metal particles such as Au, Ag, Ni, Cu, solder, carbon, and the like can be used. Further, non-conductive glass, ceramic, plastic, or the like may be used as a core, and the core surface may be coated with the metal, metal particles, carbon, or the like. By containing conductive particles, more stable connection reliability can be obtained.

  (C) It is preferable that content of electroconductive particle is 1-20 mass% with respect to the whole connection material which concerns on this embodiment, and it is more preferable that it is 5-20 mass%. By setting it as 1 mass% or more, the electrical connection between an electrode and a wiring member can be made more excellent. By setting the content to 20% by mass or less, the characteristics of the connection material can be further improved.

  The connection material of this embodiment may further contain (D) a polymerizable compound. (D) A polymerizable compound is a compound copolymerizable with the (meth) acryloyl group in (A) acrylic resin. Examples of the polymerizable compound (D) include monomers having at least one (meth) acryloyl group, aromatic vinyl monomers such as styrene and α-methylstyrene, and vinyl cyanide monomers such as acrylonitrile and methacrylonitrile. Is mentioned.

  As the monomer having one (meth) acryloyl group, the compounds exemplified as the monomer that can be used to obtain the above-mentioned (A) acrylic resin can be used.

  Monomers having two (meth) acryloyl groups include EO-modified bisphenol A di (meth) acrylate, ECH-modified bisphenol A di (meth) acrylate, bisphenol A di (meth) acrylate, 1,4-butanediol di (meth) ) Acrylate, 1,3-butylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, glycerol di (meth) acrylate, neopentyl glycol di (meth) acrylate, EO-modified di (meth) acrylate, ECH-modified Phthalic acid di (meth) acrylate, polyethylene glycol 400 di (meth) acrylate, polypropylene glycol 400 di (meth) acrylate, tetraethylene glycol di (meth) acrylate, ECH modified 1,6-he Sanjioruji (meth) acrylate, 2- (meth) acryloyloxyethyl acid phosphate, dimethylol tricyclodecane di (meth) acrylate.

  Examples of the (meth) acrylate having three or more (meth) acryloyl groups include tris (2-acryloyloxyethyl) isocyanurate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, and EO-modified phosphoric acid. Tri (meth) acrylate, EO-modified trimethylolpropane tri (meth) acrylate, PO-modified trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol hexa ( And (meth) acrylate and dipentaerythritol penta (meth) acrylate.

  These compounds can be used individually by 1 type or in combination of 2 or more types.

  (D) It is preferable that content of a polymeric compound is 20-80 mass% with respect to the whole connection material which concerns on this embodiment, and it is more preferable that it is 20-70 mass%. By setting it as 20 mass% or more, a crosslinking component can increase and heat resistance can be improved, and embrittlement after hardening can be prevented by setting it as 80 mass% or less.

  In addition to the above (A) to (D), the following materials may be added to the connection material according to the present embodiment in order to improve the characteristics. Such materials include urethane (meth) acrylate resin, urethane di (meth) acrylate resin, coupling agent, phenoxy resin to improve heat resistance, in order to improve adhesion with the base material to be connected, Examples thereof include a phenoxy resin having a reactive group, inorganic fine particles, a polymerization inhibitor for controlling curing reactivity, and an antioxidant for preventing oxidative degradation.

  The molecular weight of the resin such as urethane (meth) acrylate resin, urethane di (meth) acrylate resin, phenoxy resin, and phenoxy resin having a reactive group is preferably 5000 to 100,000 in terms of weight average molecular weight. As addition amount of these resin, it is preferable that it is 50 mass% or less with respect to the whole connection material which concerns on this embodiment. By setting it as 50 mass% or less, the crosslinked density of hardened | cured material can be made sufficient, and heat resistance and elasticity can be improved more.

  As the coupling agent, a compound containing one or more groups selected from the group consisting of vinyl group, (meth) acryloyl group, amino group, epoxy group and isocyanate group is effective.

  In the case of adding inorganic fine particles, the average particle diameter can be appropriately adjusted depending on the thickness when the connecting material used is a film and the distance between the electrode and the wiring member, but fine particles of 10 nm to 50 μm It is preferable that Further, the addition amount of the inorganic fine particles is preferably 10% by mass or less with respect to the entire connection material according to the present embodiment. By setting it as 10 mass% or less, the fall of the connection reliability after hardening can be suppressed further highly.

  As the polymerization inhibitor, hydroquinone, methyl ether hydroquinone or the like may be used as necessary.

  The connection material which concerns on this embodiment is for solar cells which electrically connects the tab wire (wiring member) for connecting a several photovoltaic cell in series and / or in parallel, and the electrode which comprises a photovoltaic cell. It can be used as a connection material.

  Next, the solar cell module and the manufacturing method thereof according to the present invention will be described. FIG. 1 is a schematic view showing a main part of one embodiment of the solar cell module of the present invention, wherein (a) is a front view thereof, (b) is a bottom view, and (c) is a side view thereof. It is.

  As shown in FIGS. 1A to 1C, the solar cell module 100 includes a finger electrode 7 and a bus bar electrode (surface electrode) 3 a on the front surface side of the silicon substrate 6, and an aluminum electrode (back surface electrode) 8 on the back surface side. In addition, a plurality of solar cells 20 each having the bus bar electrode 3 b formed therein are connected to each other by tab wires (wiring members) 4. The tab wire 4 has one end connected to the bus bar electrode 3a as the front electrode and the other end connected to the bus bar electrode 3b as the back electrode via the solar cell connecting material 10 according to the present invention.

  Since the solar cell module 100 is connected by the connection material for solar cells described above, a decrease in connection reliability is sufficiently suppressed, and excellent connection reliability can be obtained.

  Furthermore, one Embodiment of the manufacturing method of the solar cell module which concerns on this invention is described. In the manufacturing method of the solar cell module according to the present embodiment, the surface electrode 3, the solar cell connection material 10, and the tab wire (wiring member) 4 of the solar cell 20 are arranged in this order, and the surface electrode and the wiring member are arranged. It connects by pressurizing and manufactures a solar cell module. In addition, it is preferable to form and use the solar cell connection material 10 in a film shape.

  The pressure at the time of connection is not particularly limited as long as it does not damage the adherend, but is preferably 0.1 to 5 MPa, more preferably 0.5 to 3 MPa. . Moreover, the heating temperature at the time of connection is not particularly limited, but is preferably 100 to 200 ° C, and more preferably 120 to 180 ° C. The connection time can be 2 to 20 seconds. When the solar cell connection material according to this embodiment is used, the connection can be performed at a relatively low temperature (for example, about 160 ° C.), but the connection is also performed at a relatively high temperature (for example, about 200 ° C.). be able to.

  When connecting the surface electrode and the wiring member, the surface electrode and the wiring member can be connected by vacuum lamination used in the sealing process, in addition to the connection by thermocompression bonding. That is, when the manufacturing method of the solar cell module includes a step of sealing the solar cell and the wiring member by a vacuum laminator with a sealing material, the surface electrode and the wiring member are connected in this sealing step. can do.

  As laminating conditions in the sealing step, it is preferable to hold at 130 to 160 ° C. for 10 minutes or more, and it is more preferable to hold at 140 to 150 ° C. for 15 minutes or more. Laminating conditions are basically determined by the type of sealing material such as ethylene vinyl acetate (EVA), but after satisfying the EVA crosslinking conditions, the temperature and holding time at which the connecting material can be sufficiently cured, and It is preferable to set the temperature at which the adverse effect on the solar battery cell becomes smaller.

  FIG. 2 is a schematic view for explaining one embodiment of the solar cell module of the present invention. FIG. 2 shows a glass plate 1, a sealing material 2, a wiring member 4, and a connection for a film-like solar cell as a laminated body installed in a laminator device when a solar cell module is manufactured through the sealing process described above. The expanded view of the laminated body by which the material 10, the photovoltaic cell 20, the connection material 10 for film-like solar cells, the wiring member 4, the sealing material 2, and the back sheet 5 is arrange | positioned in this order is shown. The wiring member 4 and the film-like solar cell connection material 10 are arranged corresponding to the position of the surface electrode of the solar battery cell 20.

  Examples of the glass plate 1 include white plate tempered glass with dimples for solar cells. An example of the sealing material 2 is an EVA sheet made of EVA. Examples of the wiring member 4 include tab wires obtained by dipping or plating solder on Cu wires. Examples of the back sheet 5 include a PET-based or tedla-PET laminated material, a metal foil-PET laminated material, and the like.

  Next, the prepared solar cell connection material and the other end of the tab wire 4 are arranged in this order on the aluminum electrode of the second solar cell 20, and the solar cell 20 and the tab wire 4 are added. Connect by pressing. At this time, pressurization may be performed while heating. If necessary, post-curing may be performed by heat or light.

  Thus, the solar cell connecting material is cured, and the solar cell module according to this embodiment is obtained.

  According to the method for manufacturing a solar cell module according to the present embodiment, since the solar cell connection material is used, a solar cell module excellent in connection reliability in which a decrease in connection reliability is maintained sufficiently low is obtained. Can do. Even when the solar cell module obtained by the manufacturing method of the solar cell module is subjected to a heat cycle test, a decrease in connection reliability is sufficiently suppressed.

  In addition, in this embodiment, although the solar cell module which has a bus-bar electrode was demonstrated, the manufacturing method of the solar cell module of this invention may be applied to a bus-barless solar cell module, and the solar cell module of this invention is A bus barless solar cell module may be used.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example and a comparative example, this invention is not limited to these Examples.

[Method for measuring storage modulus]
A mixed solution in which the components shown in Table 3 were mixed according to the formulation shown in the same table was coated on a polyethylene film (PET film) and dried at 70 ° C. for 3 minutes to obtain a film-like connecting material having a thickness of 25 μm. . The film-like connecting material was immersed in oil heated to 180 ° C. for 40 seconds to obtain a completely cured film. The cured film was used as a test piece for elastic modulus measurement.
The obtained test piece was attached to a DVE apparatus (SOLIDS ANALYZER RSAII), and storage elastic modulus E ′ [Pa], loss elastic modulus E ″ [Pa], and tan δ peak temperature [° C.] were measured. The measurement results of the storage elastic modulus E ′ and the loss elastic modulus E ″ are shown in FIGS. 3 and 4, respectively.
The reduction rate of the storage elastic modulus is expressed by the following calculation formula.
Storage elastic modulus reduction rate [%] = 100− (storage elasticity at 150 ° C. [Pa] / storage elasticity at 20 ° C. [Pa]) * 100
The tan δ peak temperature in the present invention refers to the temperature at the top of the tan δ peak. When two peaks were present, the peak temperature on the low temperature side was defined as the tan δ peak temperature of the material.

[Connection reliability evaluation method]
A film-like connecting material was slit to a width of 1 mm in a 5-inch solar cell (with two bus bar electrodes), and temporarily crimped at 70 ° C. for 1 second. After that, the support film is peeled off, and the tab wire (lead-free) cut to a width of 1.5 mm is placed on the above-mentioned film-like connecting material, and is crimped under a crimping condition of 160 ° C., 2 MPa, 5 seconds. Fixed to. The sample thus obtained was used as a sample for reliability evaluation. In the reliability evaluation, a heat cycle test is performed in a temperature range where −40 ° C. is the lower limit value and 100 ° C. is the upper limit value, and the fill factor of the solar cell before and after the heat cycle test (hereinafter referred to as FF). (Abbreviated) was measured and the rate of change was compared. The heat cycle test was performed for 15 cycles, with the holding time at the lower limit temperature and the upper limit temperature being 30 minutes each and the time for raising and lowering the temperature being 5 minutes. F. F. A solar simulator WXS-200S-20CH, AM1.5G (manufactured by Wacom Denso Co., Ltd.) was used as an apparatus for evaluating the above. The results are shown in Table 2.
The evaluation results are as follows. F. The connection reliability was OK when the retention rate was 94% or more, and the connection reliability was NG when the retention rate was less than 94%.

[Synthesis Examples 1-4: Synthesis of acrylic resin]
Below, the synthesis example of an acrylic resin is shown. The synthesis was carried out under the same conditions except that the amount and type of monomers used were changed. Table 1 summarizes the materials used. Moreover, it shows in Table 2 about the quantity and kind of monomer to be used, and a resin characteristic of the acrylic resin obtained by the synthesis examples 1-4.

(Mother resin synthesis)
The monomer (A) shown in Table 1 was put into a 1 L beaker and mixed. After confirming that the monomers to be copolymerized were sufficiently compatible, a polymerization initiator (i) was added to obtain a mixed solution.
To a 1 L four-necked round bottom flask, methyl ethyl butyl ketone (MEK) was added as a solvent. A stirring blade, an N ₂ introduction tube, and a Liebig condenser were installed in a four-necked round bottom flask and heated. After confirming that MEK in the 1 L four-necked round bottom flask was 80 ° C., the above mixed solution was added dropwise over 3 hours using a feed pump. N ₂ was put into the solution, and oxygen was removed by constantly bubbling during the synthesis. The stirring rotation speed was 300 min ⁻¹ .
1 hour and 2 hours later, in order to promote the reaction of the residual monomer, a polymerization initiator solution in which the polymerization initiator (ii) was dissolved in MEK was added to a 1 L four-necked round bottom flask, and the mixture was heated to 80 ° C. Keep for 2 hours. Thereafter, in order to deactivate the remaining polymerization initiator, it was heated to 120 ° C. in a sealed container and left for 1 hour. Thus, a mother resin was obtained. In addition, regarding the synthesis example 4, the obtained mother resin was used as (A) acrylic resin.

(Synthesis of acrylic resin)
500 g of mother resin was weighed out into a 1 L four-necked round bottom flask, and a stirring blade, an N ₂ introduction tube, and a Liebig condenser were installed. The number of revolutions of the stirring blade was set to 300 min ⁻¹ , and the inside of the ¹ L four-necked round bottom flask was purged with N ₂ . The reaction temperature was set to 75 ° C. and warmed. After confirming that the temperature of the mother resin reached 75 ° C., 1 drop of dibutyltin lauryl (L-101) was added as a reaction catalyst to the mother resin solution. Thereafter, 1/2 equivalent of 2-methacryloyloxyethyl isocyanate (MOI) (U) of the OH group in the mother resin was added and left at 75 ° C. for 3 hours. It was confirmed that the isocyanate group (2270 cm ⁻¹ ) of MOI disappeared by measuring an infrared spectrum using FREEXACT-2 (manufactured by Horiba, Ltd.). At that time, the reaction was terminated and the desired acrylic resin was obtained. About the obtained acrylic resin, the weight average molecular weight was measured.

The weight average molecular weight is a value determined by measurement using gel permeation chromatography using tetrahydrofuran (THF) as a solvent, and conversion using a standard polystyrene calibration curve using the following apparatus and measurement conditions. It is. In preparing the calibration curve, 5 sample sets (PStQuick MP-H, PStQuick B [trade name, manufactured by Tosoh Corporation]) were used as standard polystyrene.
Equipment: High-speed GPC equipment HLC-8320
(Product name, manufactured by Tosoh Corporation)
Detector: Differential refractometer RI-8020 (trade name, manufactured by Tosoh Corporation)
Solvent: Tetrahydrofuran (THF)
Column: Gelpack GL-A-160-S and GL-A150-SG2000Hhr
(Product name, manufactured by Hitachi Chemical Co., Ltd.)
Measurement temperature: 40 ° C
Flow rate: 0.35 mL / min Pressure: 2.94 MPa
Sample concentration: 200 ppm
Injection volume: 20 μL

Example 1
As shown in Table 3, (A) 30 parts by mass of the acrylic resin obtained in Synthesis Example 1 as an acrylic resin, (B) 5 parts by mass of parroyl L as a thermal polymerization initiator, and (C) an average particle as conductive particles 10 parts by weight of Ni particles having a diameter of 5 μm, (D) 30 parts by weight of isocyanuric acid EO-modified acrylate (M-313), 5 parts by weight of dimethylol tricyclodecane diacrylate (DCP-A) as a polymerizable compound, and BPA type epoxy di 10 parts by mass of acrylate (V-90) and 30 parts by mass of urethane acrylate resin as other components were mixed. This mixed solution is coated on a PET film as a support film with an applicator and dried in a dryer at 70 ° C. for 3 minutes to obtain a connection material (conductive adhesive film) formed into a film having a thickness of 25 μm. It was. Connection reliability evaluation was performed about the obtained connection material. The results are shown in Table 3. Moreover, the storage elastic modulus was measured about the obtained connection material. Changes in storage elastic modulus and loss elastic modulus at this time are shown in FIGS. 3 and 4, respectively.

(Examples 2-3, Comparative Examples 1-2)
A connecting material formed into a film having a thickness of 25 μm was obtained in the same manner as in Example 1 except that the acrylic resin or phenoxy resin shown in Table 3 was used instead of the acrylic resin obtained in Synthesis Example 1. . Connection reliability evaluation was performed about the obtained connection material. The results are shown in Table 3. Moreover, the storage elastic modulus was measured about the obtained connection material. Changes in storage elastic modulus and loss elastic modulus at this time are shown in FIGS. 3 and 4, respectively.

  DESCRIPTION OF SYMBOLS 1 ... Glass plate, 2 ... Sealing material, 3a ... Bus bar electrode (surface electrode), 3b ... Bus bar electrode (surface electrode), 4 ... Tab wire (wiring member), 5 ... Back sheet, 6 ... Silicon substrate, 7 ... Finger electrode, 8 ... aluminum electrode (back electrode), 10 ... connecting material, 20 ... solar cell, 100 ... solar cell module.

Claims (3)

A solar cell connection material for connecting an electrode and a wiring member,
The cured product obtained by heating the solar cell connection material at 180 ° C. for 40 seconds has a reduction rate of storage elastic modulus at 20 to 150 ° C. of 80% or less, and the cured product has a tan δ peak temperature of 150%. der more than ℃ is,
(A) A solar cell connection material comprising an acrylic resin comprising a structural unit having a (meth) acryloyl group in the side chain, (B) a thermal polymerization initiator, and (C) conductive particles . The solar cell connection material according to claim 1 is interposed between an electrode formed on the main surface of the solar battery cell and a wiring member for electrically connecting the plurality of solar battery cells, The manufacturing method of a solar cell module provided with the process of thermocompression-bonding the said electrode and the said wiring member so that the said wiring member may be electrically connected. A solar cell in which an electrode is formed on the main surface;
A wiring member for electrically connecting a plurality of solar cells;
A connecting portion interposed between the electrode and the wiring member;
With
A cured product of a connection material for solar cells, wherein the connection part contains (A) an acrylic resin comprising a structural unit having a (meth) acryloyl group in the side chain, (B) a thermal polymerization initiator, and (C) conductive particles . The solar cell module which consists of these, The reduction rate of the storage elastic modulus in 20-150 degreeC of the said hardened | cured material is 80% or less, and the peak temperature of tan-delta of the said hardened | cured material is 150 degreeC or more.

Images