JP6334871B2 - Solar cell module - Google Patents

Description

  The present invention relates to a solar cell module.

  Solar cells are attracting attention because they can generate power using inexhaustible solar energy, are clean without discharging exhaust gas, and are safe without danger of releasing radioactivity. Yes. Since solar cells are often placed outdoors, they are exposed to harsh environments. The solar cell should be used for a long period of 10 years or longer, and the weather resistance, particularly the structure against moisture, affects the deterioration in outdoor use. Therefore, it is required to ensure durability against moisture. For example, a laminated film having a structure in which a metal foil made of aluminum or the like is laminated in a single layer structure or a multilayer structure has been used as a back side protective material. .

  FIG. 1 shows an example of the structure of a solar cell module. As shown in FIG. 1, a solar cell module has a plurality of solar cells, for example, EVA (ethylene-vinyl acetate copolymer) between a glass plate and a back surface side protective material in which an aluminum foil is sandwiched between plastic films. Combined) It is configured to be sealed with a sealing material made of resin. Adjacent solar cells are electrically connected in series or in parallel with a connecting member made of, for example, copper foil. However, when a material including a metal foil is used as the back surface side protective material, although it has excellent gas barrier properties, there is a problem that a short circuit occurs due to its electrical conductivity.

  In order to solve this problem, as a backside protective material, an inorganic oxide such as silicon oxide or aluminum oxide is used on a base film such as a PET (polyethylene terephthalate) film by vacuum deposition or plasma chemical vapor deposition. A material that has been coated to improve moisture resistance has been proposed (see, for example, Patent Document 1). In addition, a high moisture-resistant film is disposed on the sealing material side (cell side) as a back surface side protective material, and a waterproof film showing a water vapor transmission amount equal to or higher than the water vapor transmission amount of the high moisture resistance film is disposed on the outside air side. There has also been proposed a material for disposing an adhesive member (see Patent Document 2).

  In addition, a method of adjusting the content of the epoxy resin constituting the collector electrode of the solar cell according to the water vapor transmission amount of the protective layer (back surface side protective material) has been proposed (see Patent Document 3). Specifically, it is described that moisture from the back surface can be prevented by using an epoxy resin that is difficult to hydrolyze.

JP 2000-114565 A JP-A-2005-101404 JP 2005-276939 A

  According to the study by the present inventors, it has been clarified that the moisture that has entered from the end portion (side surface) of the module enters the solar battery cell, thereby reducing long-term reliability and deterioration. For example, when using conventional Al foil, moisture from the back side can be prevented from entering the module, but moisture from the side accumulates in the module and long-term reliability deteriorates. I understood.

  However, when the back surface side protective material as in Patent Documents 1 to 3 is used, it is considered that a certain degree of moisture suppression effect is obtained, but the influence of moisture entering from the side surface has not been studied at all. It is considered that the moisture suppression effect from is not necessarily sufficient. Moreover, when a laminated film etc. are used as a back surface side protective material like patent document 1, 2, a subject remains from the point of productivity or production cost. Moreover, when adjusting the content rate of an epoxy resin suitably like patent document 3, in order to suppress moisture, it is necessary to increase the resin concentration contained in a collector electrode, and it is thought that resistance will become high.

  It is an object of the present invention to prevent the deterioration of the performance of a solar cell module and improve the service life by using a solar cell module having a solar cell having a predetermined electrode and having a predetermined sealing structure. To do.

  As a result of intensive studies in view of the above problems, the present inventors have found that by using a predetermined electrode structure and sealing structure, it is possible to prevent the performance deterioration of the solar cell module and to improve the service life. The present invention has been reached.

  That is, the present invention relates to the following.

The solar cell module of the present invention has a solar cell, a light receiving surface side sealing material and a light receiving surface side protective material in this order on the light receiving surface side of the solar cell, and a back surface side on the back surface side of the solar cell. It has a sealing material and a back surface side protective material in this order, and the solar battery cell includes a photoelectric conversion unit, a light receiving surface electrode on the light receiving surface side of the photoelectric conversion unit, and a back electrode on the back surface side of the photoelectric conversion unit. The back electrode is formed on 40% or more of the back side surface of the photoelectric conversion part, and the water vapor permeation amounts of the light receiving side sealing material and the back side sealing material are W1 and W2, respectively. In this case, W1 <W2 is satisfied, and the back surface side protective material satisfies a water vapor transmission rate of 0.1 [g / m ² / day] to 15.0 [g / m ² / day].

  The back electrode is preferably formed on 90% or more of the back side surface of the photoelectric conversion part.

  The back electrode is preferably formed of a metal film.

The water vapor permeation amount at 40 ° C. and 90% RH of the light receiving surface side sealing material and the back surface side sealing material is W1 ≦ 3.0 [g / m ² / day], W2 ≦ 30.0 [g / m. ² / day] is preferably satisfied.

  The back surface side protective material is mainly composed of at least one material selected from polyvinylidene fluoride (PVDF), ethylene / tetrafluoroethylene copolymer (ETFE), polyethylene terephthalate (PET), and polyvinyl fluoride (PVF). It is preferable to use as a component.

  The back electrode preferably has a first conductive layer and a second conductive layer in this order from the photoelectric conversion portion side, and the second conductive layer is preferably copper.

  According to the present invention, a solar cell module having excellent solar cell characteristics and reliability is obtained by using a solar cell module having a solar cell having a predetermined electrode, and a predetermined sealing material and a back surface side protective material. Can be produced.

Example of the structure of a conventional solar cell module 1 is a schematic cross-sectional view showing a solar cell module structure according to an embodiment of the present invention. Schematic diagram of solar cell of the present invention Schematic diagram of water vapor transmission rate measurement tester Moisture permeation path of the structure of Comparative Example 1 Example moisture penetration path

Embodiments of the present invention will be further described below. As schematically shown in FIG. 2, the solar cell module 100 of the present invention includes a solar cell 101 and a light-receiving surface side protective material 200 and a light-receiving surface-side sealing material 201 on the light-receiving surface side of the solar cell 101. In this order, the back surface side sealing material 202 and the back surface side protective material 203 are provided in this order on the back surface side of the solar battery cell 101. The solar battery cell 101 includes a photoelectric conversion unit 50, a light receiving surface electrode 7 on the light receiving surface side of the photoelectric conversion unit 50, and a back electrode 8 on the back surface side of the photoelectric conversion unit. The back electrode 8 is formed on 40% or more of the back side surface of the photoelectric conversion unit 50. When the water vapor permeation amounts of the light receiving surface side sealing material 201 and the back surface side sealing material 202 are W1 and W2, respectively, W1 <W2 is satisfied. The back surface side protective material 203 has a water vapor transmission rate of 0.1 [g / m ² / day] to 15 [g / m ² / day].

  The solar cell of the present invention is modularized by an appropriate method. For example, as shown in FIG. 2, the wiring material 204 is connected to the light receiving surface electrode 7 and the back surface electrode 8, whereby a plurality of solar cells are connected in series or in parallel, and the light receiving surface side sealing material 201 and the back surface Modularization is performed by sealing with the side sealing material 202 and the light-receiving surface protection material 200 and the back surface protection material 203. That is, by arranging and pressing each material as shown in FIG. 2, the sealing material flows between the solar cells and the end portions of the modules, and modularization is performed.

In the present invention, the light receiving surface side sealing material 201 and the back surface side sealing material 202 are formed on the light receiving surface side and the back surface side of the solar battery cell 101. The light-receiving surface side sealing material 201 and the back surface side sealing material 202 satisfy W1 <W2, where the water vapor transmission amounts are W1 and W2, respectively. 40 ° C., the water vapor permeation amount of 90% RH is ^{preferably, W1 ≦ 3.0 [g / m} 2 /day],W1<W2≦30.0[g/m 2 / day]. More preferably ^{W1 ≦ 2.6 [g / m 2} /day],W1<W2≦20.0[g/m 2 / day].

  Here, as shown in FIG. 5, when Al foil or the like is used as the back surface side protective material as in the prior art, moisture from the back surface side can be prevented, but according to the study by the present inventors, from the side surface, It became clear that moisture accumulated in the module, reducing long-term reliability. On the other hand, by using the sealing material in the above range, the moisture on the light receiving surface side of the solar cell out of the moisture entering from the side surface of the solar cell module is sealed on the light receiving surface side as shown in FIG. The material 201 can prevent this. Moreover, the moisture of the back surface side of a photovoltaic cell among the moisture from a side surface can be prevented with the back surface electrode 8 of a photovoltaic cell.

Further, unlike the Al foil or the like (less than the water vapor transmission rate of 0.1 [g / m ² / day]) conventionally used as the back surface side protective material 203, the water vapor transmission rate is 0.1 [g / m ^2]. / Day] By using a material greater than or equal to the day, moisture from the side surface can be released from the back surface side protective material to the outside of the solar cell module. Therefore, long-term reliability can be improved.

  On the light receiving surface side of the solar cell, in order to take in light, the light receiving surface electrode is preferably as thin as possible, and a comb-shaped electrode is generally used. Therefore, the influence of moisture from the light receiving surface side becomes larger than that on the back surface side. In the present invention, moisture from the light receiving surface side can be further suppressed by using a light receiving surface side sealing material that has a lower water vapor transmission rate than the back surface side sealing material, that is, satisfying W1 <W2.

The light-receiving surface side sealing material 201 is made of a material having a water vapor transmission amount of 2.6 [g / m ² / day] or less, for example, a polyethylene resin composition mainly composed of an olefin elastomer mainly composed of ethylene. High-density polyethylene (HDPE), high-pressure low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), polypropylene (PP), and an ethylene / α-olefin copolymer are more preferable.

Further, as the back surface side sealing material 202, a material having a water vapor transmission rate of 20.0 [g / m ² / day] or less, for example, ethylene / vinyl acetate copolymer (EVA), ethylene / vinyl acetate / triallyl. It is more preferable to use a light-transmitting resin such as isocyanurate (EVAT), polyvinyl butyrate (PVB), silicon, urethane, acrylic, and epoxy.

  Usually, the material becomes more expensive as the water vapor transmission amount becomes lower. In the present invention, the back surface side sealing material is obtained by using the solar cell having a predetermined back surface electrode and the back surface side protective material of the solar cell module. Even when an inexpensive material is used, a solar cell module with improved long-term reliability can be produced. When the solar cell module as described above is manufactured, the following effects are exhibited. That is, moisture that has entered the module can be released from the back surface side protective material into the atmosphere.

  When producing a solar cell module having a plurality of solar cells, the light receiving surface side protective material is disposed on the light receiving surface side (light incident surface side) of each solar cell to protect the surface of the solar cell module. Is preferred. As a light receiving surface side protective material, a fluororesin film such as a glass substrate (blue plate glass substrate or white plate glass substrate), a polyvinyl fluoride film (for example, Tedlar film (registered trademark)), or a polyethylene terephthalate (PET) film is used. The organic film is exemplified, but the strength, light transmittance (including the wavelength dependency of light transmittance such as light on the short wavelength side and long wavelength side), and the price in comparison with other industrially obtained materials A white glass substrate is preferable from the viewpoint of further preventing moisture from the surface. As described above, since the comb-shaped light receiving surface side electrode is generally used on the light receiving surface side of the solar battery cell, the influence of moisture is increased on the light receiving surface side. From this point, a white glass substrate is more preferable.

  When producing a solar cell module having a plurality of solar cells, the back side protective material is preferably disposed on the back side of each solar cell to protect the back side of the solar cell module. In the present invention, by using an organic film such as a polyethylene terephthalate (PET) film (not including a metal foil made of aluminum or the like), the moisture entering the module and the moisture are released together with protecting the back surface. Can do.

Here, when a metal layer such as an Al foil is used as the back surface side protective material as in the prior art, the moisture permeation from the back side is usually because the water vapor transmission amount is less than 0.1 [g / m ² / day]. Although the infiltration of the minute could be prevented, the moisture from the side of the module could not be released, and the long-term reliability tended to deteriorate.

However, as in the present invention, as the back surface side protective material, a material satisfying a water vapor transmission rate of 0.1 [g / m ² / day] to 15 [g / m ² / day], for example, polyethylene terephthalate ( The moisture staying in the solar cell module can be released by using an organic film such as PET (not including a metal foil made of aluminum or the like), and the moisture that can enter from the back side is As described later, since it can be prevented by the back electrode of the solar battery cell, improvement in long-term reliability can be expected.

  As the back side protection material, a fluorine resin film such as a polyvinyl fluoride film (for example, Tedlar film (registered trademark)) or an organic film such as a polyethylene terephthalate (PET) film is laminated in a single layer structure or a multilayer structure. Structure. Among these, it is more preferable to use a single layer of PET from the viewpoint of further reducing the manufacturing cost.

  The solar battery cell 101 in the present invention includes a photoelectric conversion unit 50, a light receiving surface electrode 7 on the light receiving surface side of the photoelectric conversion unit 50, and a back electrode 8 on the back surface side of the photoelectric conversion unit 50. The back surface electrode 8 of the solar battery cell 101 in the present invention is formed so as to cover 40% or more of the back surface side surface of the photoelectric conversion unit 50. By setting it as the said range, it can prevent that the moisture from the back surface side or side surface of a solar cell permeates into the photovoltaic cell 101. FIG.

That is, in the present invention, a material having a relatively high water vapor transmission rate of 0.1 [g / m ² / day] to 15.0 [g / m ² / day] as the back surface side protective material of the solar cell module. And the back side sealing material satisfying W1 <W2 (the water vapor transmission amount is higher than the light receiving side sealing material) is used. For this reason, although moisture easily enters from the back side compared to the light receiving surface side, the use of the back electrode 8 can prevent moisture that can enter from the back side.

  As the back electrode 8, from the viewpoint of preventing moisture, 90% or more of the surface of the back surface of the photoelectric conversion unit 50 is preferably covered, and more than 95% is covered. It is particularly preferable that 100%, that is, the entire surface is covered. In addition, the area covered with the back electrode on the back surface of the photoelectric conversion unit is obtained by, for example, obtaining the line width in a certain range of the back electrode surface with an optical microscope and multiplying it with the finger length and the number. I can do it.

  The solar battery cell 101 is not particularly limited, and is a crystalline silicon solar battery, a solar battery using a semiconductor substrate other than silicon such as GaAs, a pin junction or a pn junction of an amorphous silicon thin film or a crystalline silicon thin film. Various types of organic thin film solar cells such as silicon-based thin film solar cells having a transparent electrode layer formed thereon, compound semiconductor solar cells such as CIS and CIGS, dye-sensitized solar cells and organic thin films (conductive polymers) Applicable to solar cells. Among these, a solar cell having an amorphous semiconductor layer is preferable, and a heterojunction solar cell is more preferably used. For example, a heterojunction solar cell generally has an amorphous silicon thin film layer, and the amorphous silicon thin film layer is easily damaged by moisture. However, by using the solar cell module of the present invention, moisture can be further prevented from entering the solar cell.

  Below, the photovoltaic cell and solar cell module which concern on one Embodiment of this invention are demonstrated in detail. In the following embodiment, a case where a heterojunction solar cell is used as the solar cell will be described, but the present invention is not limited to the following embodiment.

[Solar cells]
As a solar cell, for example, a crystal system in which a diffusion potential is formed by having a silicon thin film having a band gap different from that of single crystal silicon on the surface of a single crystal silicon substrate of one conductivity type as shown in FIG. It is preferable to use a solar cell (heterojunction crystalline silicon solar cell). The solar battery cell has a conductive silicon-based thin film and a light incident side transparent electrode layer in this order on one surface (light incident side surface) of the one conductivity type single crystal silicon substrate as a photoelectric conversion unit. It is preferable to have a conductive silicon-based thin film and a back-side transparent electrode layer in this order on the other surface (a surface different from the light incident side) of the one-conductive single crystal silicon substrate. A light receiving surface electrode is formed on the light incident side transparent electrode layer on the surface of the photoelectric conversion unit. A back electrode having a larger area covering the photoelectric conversion portion than the light receiving surface electrode is formed on the back side transparent electrode layer.

  An intrinsic silicon-based thin film is preferably provided between the one-conductivity-type single crystal silicon substrate and the conductive silicon-based thin film. First, the one conductivity type single crystal silicon substrate 1 will be described. In general, a single crystal silicon substrate contains an impurity that supplies electric charge to silicon in order to provide conductivity. Single crystal silicon substrates include an n-type in which atoms (for example, phosphorus) for introducing electrons into silicon atoms and a p-type in which atoms (for example, boron) for introducing holes into silicon atoms are contained. That is, “one conductivity type” in the present invention means either n-type or p-type.

  In heterojunction solar cells, electron / hole pairs are efficiently separated and recovered by providing a strong electric field with the heterojunction on the incident side where the most incident light is absorbed as the reverse junction. Can do. Therefore, the heterojunction on the light incident side is preferably a reverse junction. On the other hand, when holes and electrons are compared, electrons having smaller effective mass and scattering cross section generally have higher mobility. From the above viewpoint, the single crystal silicon substrate 1 used for the heterojunction solar cell is preferably an n-type single crystal silicon substrate. The single crystal silicon substrate 1 preferably has a texture structure on the surface from the viewpoint of light confinement.

A silicon-based thin film is formed on the surface of the one conductivity type single crystal silicon substrate 1 on which the texture is formed. As a method for forming a silicon-based thin film, a plasma CVD method is preferable. As conditions for forming a silicon-based thin film by plasma CVD, a substrate temperature of 100 to 300 ° C., a pressure of 20 to 2600 Pa, and a high frequency power density of 0.004 to 0.8 W / cm ² are preferably used. As a raw material gas used for forming a silicon-based thin film, a silicon-containing gas such as SiH 4 or Si 2 H 6 or a mixed gas of silicon-based gas and H 2 is preferably used.

  The conductive silicon thin film 3 is a one-conductivity type or reverse conductivity type silicon thin film. For example, when n-type is used as the one-conductivity-type single crystal silicon substrate 1, the one-conductivity-type silicon-based thin film and the reverse-conductivity-type silicon-based thin film are n-type and p-type, respectively. As a dopant gas for forming a p-type or n-type silicon-based thin film, B2H6 or PH3 is preferably used. Moreover, since the addition amount of impurities such as P and B may be very small, it is preferable to use a mixed gas diluted in advance with SiH4 or H2. When forming a conductive silicon thin film, the energy gap of the silicon thin film may be changed by adding a gas containing a different element such as CH4, CO2, NH3, GeH4 and alloying the silicon thin film. it can.

  Examples of silicon-based thin films include amorphous silicon thin films, microcrystalline silicon (thin films containing amorphous silicon and crystalline silicon), and the like. Among these, it is preferable to use an amorphous silicon thin film. For example, as a preferable configuration of the photoelectric conversion unit 50 when an n-type single crystal silicon substrate is used as the one-conductivity-type single crystal silicon substrate 1, the transparent electrode layer 6a / p-type amorphous silicon thin film 3a / i type is used. Examples include a laminated structure in the order of amorphous silicon thin film 2a / n type single crystal silicon substrate 1 / i type amorphous silicon thin film 2b / n type amorphous silicon thin film 3b / transparent electrode layer 6b. In this case, for the reason described above, it is preferable that the p-layer side be the light incident surface.

  In addition, as described above, when an amorphous semiconductor layer such as an amorphous silicon thin film is used as a solar battery cell, the amorphous semiconductor layer is vulnerable to moisture, and thus it is a problem in terms of long-term reliability. There are many. However, by using the solar cell module having the structure of the present invention, it is possible to further suppress the intrusion of moisture into the solar cell.

  The intrinsic silicon thin films 2a and 2b are preferably i-type hydrogenated amorphous silicon composed of silicon and hydrogen. When i-type hydrogenated amorphous silicon is deposited on a single crystal silicon substrate by CVD, surface passivation can be effectively performed while suppressing impurity diffusion into the single crystal silicon substrate. Further, by changing the amount of hydrogen in the film, it is possible to give an effective profile to the carrier recovery in the energy gap.

  The p-type silicon thin film is preferably a p-type hydrogenated amorphous silicon layer, a p-type amorphous silicon carbide layer, or a p-type amorphous silicon oxide layer. A p-type hydrogenated amorphous silicon layer is preferable from the viewpoint of suppressing impurity diffusion and reducing the series resistance. On the other hand, the p-type amorphous silicon carbide layer and the p-type amorphous silicon oxide layer are wide gap low-refractive index layers, which are preferable in terms of reducing optical loss.

  The photoelectric conversion unit 50 of the heterojunction solar cell 101 preferably includes the transparent electrode layers 6a and 6b on the conductive silicon thin films 3a and 3b. The transparent electrode layer is formed by a transparent electrode layer forming step. The transparent electrode layers 6a and 6b are mainly composed of a conductive oxide. As the conductive oxide, for example, zinc oxide, indium oxide, or tin oxide can be used alone or in combination. From the viewpoints of conductivity, optical characteristics, and long-term reliability, an indium oxide containing indium oxide is preferable, and an indium tin oxide (ITO) as a main component is more preferably used. Here, “main component” means that the content is more than 50% by weight, preferably 70% by weight or more, and more preferably 90% by weight or more. The transparent electrode layer may be a single layer or a laminated structure composed of a plurality of layers.

  A doping agent can be added to the transparent electrode layer. For example, when zinc oxide is used as the transparent electrode layer, examples of the doping agent include aluminum, gallium, boron, silicon, and carbon. When indium oxide is used as the transparent electrode layer, examples of the doping agent include zinc, tin, titanium, tungsten, molybdenum, and silicon. When tin oxide is used as the transparent electrode layer, examples of the doping agent include fluorine.

  The doping agent can be added to one or both of the light incident side transparent electrode layer 6a and the back surface side transparent electrode layer 6b. In particular, it is preferable to add a doping agent to the light incident side transparent electrode layer 6a. By adding a doping agent to the light incident side transparent electrode layer 6a, the resistance of the transparent electrode layer itself can be reduced and resistance loss between the transparent electrode layer 6a and the light receiving surface electrode 7 can be suppressed. .

  The film thickness of the light incident side transparent electrode layer 6a is preferably 10 nm or more and 140 nm or less from the viewpoints of transparency, conductivity, and light reflection reduction. The role of the transparent electrode layer 6a is to transport carriers to the light-receiving surface electrode 7, as long as it has conductivity necessary for that purpose, and the film thickness is preferably 10 nm or more. By setting the film thickness to 140 nm or less, absorption loss in the transparent electrode layer 6a is small, and a decrease in photoelectric conversion efficiency accompanying a decrease in transmittance can be suppressed. Moreover, if the film thickness of the transparent electrode layer 6a is within the above range, an increase in carrier concentration in the transparent electrode layer can also be prevented, so that a decrease in photoelectric conversion efficiency due to a decrease in transmittance in the infrared region is also suppressed.

  The method for forming the transparent electrode layer is not particularly limited, but a physical vapor deposition method such as a sputtering method, a chemical vapor deposition (MOCVD) method using a reaction between an organometallic compound and oxygen or water is preferable. In any film forming method, energy by heat or plasma discharge can be used.

  The substrate temperature at the time of producing the transparent electrode layer is appropriately set. For example, when an amorphous silicon thin film is used as the silicon thin film, the temperature is preferably 200 ° C. or lower. By setting the substrate temperature to 200 ° C. or lower, desorption of hydrogen from the amorphous silicon layer and accompanying dangling bonds to silicon atoms can be suppressed, and as a result, conversion efficiency can be improved.

  The light receiving surface electrode 7 is formed on the transparent electrode layer 6a. The electrode material for the light-receiving surface electrode 7 is not particularly limited, and gold, silver, copper, aluminum, or the like can be used. From the viewpoint of electrical conductivity, silver or copper is preferably used. The light-receiving surface electrode 7 can be produced by a known technique such as an ink jet method, a screen printing method, a wire bonding method, a spray method, a vacuum deposition method, a sputtering method, etc., but from the viewpoint of productivity, a screen printing method using a silver paste, A plating method using copper is preferred. Since the light receiving surface electrode is formed on the light receiving surface side, it is preferable to form the light receiving surface electrode in a comb shape from the viewpoint of further suppressing the light blocking loss.

  A back electrode 8 is formed on the back transparent electrode layer 6b. As the back electrode 8, a metal film, a conductive paste, or the like can be used, but a metal film is preferably used from the viewpoint of reducing resistance. The back electrode may be a single layer or a plurality of layers, but a plurality of layers is preferable from the viewpoint of cost and long-term reliability.

  When using what has multiple layers as a back electrode, what has a 1st conductive layer and a 2nd conductive layer in order from the said back side transparent electrode layer 6b side can be used, for example. At this time, as the first conductive layer, it is desirable to use a material having high reflectivity from the near infrared to the infrared region and high conductivity and chemical stability. Examples of such a material include silver, gold, and aluminum. Among these, it is particularly preferable to use silver. Moreover, as a 2nd conductive layer, it is preferable to use aluminum and copper from a viewpoint of cost suppression, and it is more preferable to have copper as a main component from a viewpoint of electrical conductivity.

  For example, when a second conductive layer containing copper as a main component is used as the back electrode, the conductive protection is further provided on the second conductive layer in order to suppress oxidation of the second conductive layer and diffusion to the sealing material. It is preferable to form a layer. Of these, silver is preferable as the conductive protective layer from the viewpoint of suppressing modification, and it is more preferable to use titanium, tin, chromium, or the like from the viewpoint of being less oxidized and being manufactured at a lower cost.

  The thickness of the back electrode in the present invention is preferably 200 to 1200 nm from the viewpoint of reducing resistance. For example, when a back electrode having a second conductive layer on the first conductive layer is used, the film thickness may be appropriately set depending on the material of each layer. For example, as the first conductive layer / second conductive layer, When Ag / Cu is used, the first conductive layer = 8 to 100 nm, the second conductive layer = 200 to 1000 nm, and the like can be used. Moreover, when it further has an electroconductive protective layer, a 10-100 nm thing etc. can be used, for example.

  For example, when a back electrode having a plurality of layers is used (for example, when the back electrode includes a first conductive layer and a second conductive layer), the first conductive layer is formed in the region where the second conductive layer is formed. If it is, there may be a part which does not have a 1st conductive layer, for example, a grid form may be sufficient.

  According to the present invention, not only the entry of moisture into the solar cell module from the outside is prevented, but also the opening is performed, so that the performance deterioration of the solar cell module can be prevented and the service life can be improved.

[Solar cell module]
Regarding modularization, a solar cell module usually includes a wiring material for connecting solar cells or solar cells and an external circuit. In this case, a wiring material is connected to the light receiving surface electrode or the back surface electrode of the solar battery cell. The wiring members may be connected in series or in parallel.

  The connection between the wiring material and the solar cell generally includes a method of bonding with a resin adhesive containing conductive fine particles, a method of soldering, etc., but a metal was used as the light receiving surface electrode and the back surface electrode. In this case, from the viewpoint of further suppressing the ease of bonding with the metal and thermal damage, it is preferable that the bonding is performed with a resin adhesive containing conductive fine particles.

  A solar battery string and a wiring material are connected to each other via a resin adhesive to produce a solar battery string. Next, a light receiving surface side sealing material, a solar battery string, a back surface side seal are formed on the light receiving surface side protective material. A solar cell module can be produced by sequentially laminating a stopper and a back surface side protective material to form a laminate. Next, it is preferable to cure the encapsulant by heating the laminate body under predetermined conditions. And it is preferable to produce a solar cell module by attaching an Al frame or the like.

  Although a solar cell module can be produced as described above, it is not limited to the above.

Example 1
The heterojunction solar cell module of Example 1 was manufactured as follows.

  As a single conductivity type single crystal silicon substrate, an n-type single crystal silicon wafer having an incident plane of (100) and a thickness of 200 μm was used, and this silicon wafer was immersed in a 2 wt% HF aqueous solution for 3 minutes. After the silicon oxide film was removed, rinsing with ultrapure water was performed twice. This silicon substrate was immersed in a 5/15 wt% KOH / isopropyl alcohol aqueous solution maintained at 70 ° C. for 15 minutes, and the surface of the wafer was etched to form a texture. Thereafter, rinsing with ultrapure water was performed twice. When the surface of the wafer was observed with an atomic force microscope (manufactured by AFM Pacific Nanotechnology), etching was most advanced on the surface of the wafer, and a pyramidal texture with the (111) plane exposed was formed.

The etched wafer was introduced into a CVD apparatus, and an i-type amorphous silicon film having a thickness of 5 nm was formed on the light incident side as an intrinsic silicon-based thin film 2a. The film formation conditions for the i-type amorphous silicon were: substrate temperature: 170 ° C., pressure: 100 Pa, SiH 4 / H 2 flow rate ratio: 3/10, and input power density: 0.011 W / cm ² . In addition, the film thickness of the thin film in a present Example measures the film thickness of the thin film formed on the glass substrate on the same conditions by the spectroscopic ellipsometry (brand name M2000, JA Woollam Co., Ltd. product). It is a value calculated from the film forming speed obtained by this.

On the i-type amorphous silicon layer 2a, a p-type amorphous silicon film having a thickness of 7 nm was formed as the reverse conductive silicon-based thin film 3a. The film forming conditions for the p-type amorphous silicon layer 3a were a substrate temperature of 170 ° C., a pressure of 60 Pa, a SiH 4 / B 2 H 6 flow rate ratio of 1/3, and an input power density of 0.01 W / cm ² . The B2H6 gas flow rate mentioned above is a flow rate of a diluted gas diluted with H2 to a B2H6 concentration of 5000 ppm.

Next, an i-type amorphous silicon layer having a thickness of 6 nm was formed as an intrinsic silicon-based thin film 2b on the back side of the wafer. The film formation conditions for the i-type amorphous silicon layer 2b were the same as those for the i-type amorphous silicon layer 2a. On the i-type amorphous silicon layer 2b, an n-type amorphous silicon layer having a thickness of 4 nm was formed as the one-conductivity-type silicon-based thin film 3b. The film forming conditions for the n-type amorphous silicon layer 3b were: substrate temperature: 170 ° C., pressure: 60 Pa, SiH 4 / PH 3 flow rate ratio: 1/2, input power density: 0.01 W / cm ² . The PH3 gas flow rate mentioned above is the flow rate of the diluted gas diluted with H2 to a PH3 concentration of 5000 ppm.

On this, as transparent electrode layers 6a and 6b, indium tin oxide (ITO, refractive index: 1.9) was formed to a thickness of 100 nm. Using indium oxide as a target, a transparent electrode layer was formed by applying a power density of 0.5 W / cm ² in an argon atmosphere at a substrate temperature of room temperature and a pressure of 0.2 Pa. The photoelectric conversion part of the heterojunction solar cell was produced as described above.

  On the light incident side transparent electrode layer 6a, the light-receiving surface electrode 7 was formed of Ag paste using a screen printing method. On the back surface side transparent electrode layer 6b, the back surface electrode 9 was formed by the sputtering method as follows. 100 nm of silver was formed as the first electrode layer, 250 nm of copper was formed as the second electrode layer, and 10 nm of titanium was formed as the conductive protective layer.

  In addition, the thickness of the back surface electrode in this invention was measured by observing the cross section of a heterojunction solar cell using SEM (Field emission type scanning electron microscope S4800, Hitachi High-Technologies company make). Under the present circumstances, the back surface electrode was formed in the whole surface of the back surface side of the said photoelectric conversion part. In addition, the back surface electrode was calculated | required by magnifying 20 times with an optical microscope (Olympus BX51), and observing the back surface side surface of a photoelectric conversion part.

  Then, it moved to the laser processing apparatus and the groove | channel was formed over the perimeter of the outer peripheral part of the light-incidence side of a crystalline silicon substrate with the laser beam. The position of the groove was 0.5 mm from the edge of the crystalline silicon substrate. As the laser light, the third harmonic (wavelength 355 nm) of a YAG laser was used, and the depth of the groove was set to about one third of the thickness of the crystalline silicon substrate. Then, it bent and fractured along the groove | channel, and it was set as the insulation process process by removing the crystalline silicon substrate outer peripheral part. Thereafter, annealing was performed at 190 degrees for 1 hour.

A crystalline silicon solar cell was produced as described above. Using a solar simulator having a spectral distribution of AM1.5, the solar cell characteristics were measured by irradiating simulated sunlight with an energy density of 100 mW / cm ² at 25 ° C.

  A wiring material was placed on each of the light-receiving surface electrode and the back surface electrode via a conductive adhesive, and a pressure of 2 MPa was applied at a temperature of 180 ° C. for 15 seconds to connect them to produce a solar cell string. As the conductive adhesive, a resin on a film containing 10% by mass of Ni having an average particle diameter of about 10 μmφ in a resin mainly composed of an epoxy resin was selected.

As described above, a solar cell module was produced using the solar cell string to which the wiring material was connected. White plate glass as the light-receiving surface side protective material, LDPE as the light-receiving surface side sealing material, EVA as the back surface side sealing material, and a single layer film of PET (Poly Ethylene Terephthalate) having a thickness of 30 μm as the back surface side protective material Used, laminated in the order of white plate glass, LDPE, solar cell string, EVA, PET, and integrated by applying pressure while heating. Thermocompression bonding at atmospheric pressure was performed for 5 minutes, and subsequently maintained at 150 ° C. for 60 minutes to crosslink the EVA resin. The water vapor transmission rate of PET used as the back side protective layer was 1.8 g / m ² / day (40 ° C., 90%).

In addition, the water vapor permeation amount of LDPE and EVA was measured based on JIS K 7129 (Test method for water vapor permeation of plastic film and sheet (instrument measurement method)). The water vapor transmission amount was measured using a measuring apparatus as shown in FIG. A sample was set in the measuring device, and water was placed below the sample. The atmosphere below the sample was set to temperature: 40 ° C. and humidity: 100%, and the atmosphere above the sample was set to temperature: 40 ° C. and humidity: 10% (initial humidity at the start of measurement). By maintaining this state, water vapor was allowed to pass through the sample. The humidity change rate on the upper side of the sample was measured with a humidity sensor. Then, the water vapor transmission rate of the sample was measured by comparing the measured humidity change rate with the humidity change rate in the case of using a standard test piece with a known water vapor transmission rate in advance. Thus, the water vapor transmission rate of LDPE by Example 1 measured in this way is 2.0 g / m < ² > / day (40 degreeC, 90%), and the water vapor transmission rate of EVA is 15.0 g / m < ² > / day (40 ° C, 90%).

(Example 2)
A solar cell module was produced in the same manner as in Example 1 except that white EVA containing titanium oxide was used as the back side sealing material. The water vapor transmission rate of white EVA was 12.0 g / m ² / day (40 ° C., 90%).

Example 3
A solar cell module was produced in the same manner as in Example 1 except that LLDPE having a water vapor transmission rate of 2.5 g / m ² / day (40 ° C., 90%) was used as the surface side sealing material. .

Example 4
A solar cell module was fabricated in the same manner as in Example 1 except that 300 nm of silver was formed on the entire surface as the back electrode.

(Example 5)
A solar cell module was fabricated in the same manner as in Example 1 except that Ag paste was used as the back electrode and the back electrode was formed so as to cover 50% of the back surface side surface of the photoelectric conversion portion.

(Comparative Example 1)
A solar cell in the same manner as in Example 1 except that a sheet (trilayer structure of PET 20 μm / AL 30 μm / PET 50 μm) containing EVA as the light-receiving surface side sealing material and Al foil as the back surface side protective material was used. A module was produced. The water vapor transmission rate of the Al foil was less than 0.1 g / m ² / day (40 ° C., 90%).

(Comparative Example 2)
A solar cell module was produced in the same manner as in Example 1 except that EVA was used as the light-receiving surface side sealing material.

(Comparative Example 3)
A solar cell module was fabricated in the same manner as in Example 1 except that the same paste as that of the light receiving surface electrode was used as the back electrode, and the back electrode was formed in the same pattern as the light receiving surface electrode. The light receiving surface electrode and the back surface electrode were formed so as to cover 8% of the respective surfaces of the light receiving surface side and the back surface side of the photoelectric conversion unit.

(Comparative Example 4)
A solar cell module was produced in the same manner as in Example 1 except that Ag paste was used as the back electrode and the back electrode was formed so as to cover 25% of the back surface side surface of the photoelectric conversion portion.

(Comparative Example 5)
The same as in Example 1 except that EVA is used as the light-receiving surface side sealing material, the back electrode is the same Ag paste as the light-receiving surface electrode, and the back electrode is formed in the same pattern as the light-receiving surface electrode. Thus, a solar cell module was produced. The light receiving surface electrode and the back surface electrode were formed so as to cover 8% of the respective surfaces of the light receiving surface side and the back surface side of the photoelectric conversion unit.

(Comparative Example 6)
A sheet (three-layer structure of PET 20 μm / AL 30 μm / PET 50 μm) containing EVA as the light-receiving surface side sealing material and Al foil as the back surface side protective material is used, Ag paste is used as the back surface electrode, and the back surface side surface of the photoelectric conversion unit A solar cell module was fabricated in the same manner as in Example 1 except that the back electrode was formed so as to cover 8%.

(Comparative Example 7)
A solar cell module was produced in the same manner as in Example 5 except that a sheet containing Al foil (a three-layer structure of PET 20 μm / AL 30 μm / PET 50 μm) was used as the back surface side protective material.

(Comparative Example 8)
A solar cell module was produced in the same manner as in Example 3 except that a sheet containing Al foil (a three-layer structure of PET 20 μm / AL 30 μm / PET 50 μm) was used as the back surface side protective material.

(Moisture resistance test)
Next, a moisture resistance test was performed on the solar cell modules according to Examples, Comparative Examples, and Reference Examples. The moisture resistance test was performed in accordance with the contents described in IEC61215. After measuring the initial output of the solar cell module, the solar cell module was held in a thermostatic chamber at a temperature of 85 ° C. and a humidity of 85% or more for 1000 hours. After the test, the output of the solar cell module was measured again, and the ratio (%) of the output after holding for 1000 hours with respect to the initial output of the solar cell module (hereinafter referred to as the retention rate in the moisture resistance test) was obtained. Based on the obtained initial output ratio, the moisture resistance of the solar cell module was evaluated. In IEC61215, the retention rate after the moisture resistance test is defined as 95.0% or more as an acceptance criterion. In the present invention, in order to evaluate the moisture resistance under a stricter condition for a longer period, it was held for up to 2000 hours, the retention rate of the solar cell module was determined, and 96.0% or more was regarded as acceptable.

  A summary of the above results is shown in Table 1.

  When Comparative Example 3, Comparative Example 4, Example 5, and Example 1 were compared, the retention rate increased as the area of the back electrode layer covering the back side surface of the photoelectric conversion portion increased. This is considered to be because moisture that has entered from the end (side surface) or the back side of the solar cell module can be prevented from entering the solar cell by the back electrode layer of the solar cell. In particular, in Example 5 and Example 1, the retention rate after 2000 hours, which is a more severe condition, also increased.

  Comparing Comparative Example 5 and Comparative Example 3 and Comparative Example 2 and Example 1 respectively, compared to Comparative Examples 5 and 2 using EVA as the light-receiving surface side sealing material, a comparison using LDPE having a low water vapor transmission rate In Example 3 and Example 1, the retention rate was improved. This is thought to be because moisture that has entered from the end of the module can be prevented from entering the solar cell from the light receiving surface side. Generally, in order to increase the light incident area, the solar battery cell needs to be patterned on the light receiving surface side. Therefore, as in the present invention, by using a material having a low water vapor transmission amount as the light-receiving surface side sealing material, it is possible to prevent moisture from entering the cell from the light-receiving surface side.

Further, Comparative Examples 5 and 6, Comparative Examples 2 and 1, Comparative Example 7 and Example 5, and Comparative Example 8 and Example 3 are respectively compared. For Comparative Examples 5 and 2 using backside PET (water vapor transmission rate 1.8 g / m ² / day (40 ° C., 90%)), backside Al foil (water vapor transmission rate less than 0.1 g / m ² / day ( In Comparative Examples 6 and 1 using 40 ° C. and 90%)), the retention rate was high. On the other hand, in Comparative Example 7 and Example 5, and Comparative Example 8 and Example 3, compared to Comparative Examples 7 and 8 using Al foil as the back surface side protective material, the implementation using PET having a lower water vapor transmission rate. In Examples 5 and 3, the retention after 2000 hours was higher than 96.0%.

  In Comparative Examples 5 and 2 and Examples 3 and 5 using PET as the back surface side protective material on the back surface side, in Comparative Examples 2 and 3 and 5 in which the back electrode layer was formed to 50% or more, the back surface It is thought that moisture that entered from the back side could be prevented by the electrode layer. On the other hand, in Comparative Example 5 in which 8% is covered as the back electrode layer, since moisture entering from the back side enters the cell, a comparison using an Al foil that can further prevent moisture from entering from the back side. It is considered that Example 6 has higher characteristics. In the comparative example, EVA is used as the light-receiving surface side sealing material, and moisture that has entered from the end of the module enters the cell from the light-receiving surface side, which is considered to have a large influence.

  On the other hand, in Comparative Example 7 and Example 5, and Comparative Example 8 and Example 3, out of the moisture from the module end, the light receiving surface side is prevented by LDPE having a low water vapor transmission amount, and moisture from the back side Is prevented by the back electrode layer of the solar battery cell, it is considered that the influence on the back surface side from the module end is relatively large. Specifically, in Comparative Examples 7 and 8 using Al foil, moisture from the side surface was not released from the back side but accumulated in the module, whereas in Examples 5 and 3 using PET, It is thought that moisture from the side was released to the outside.

  Further, when Examples 1 and 3 were compared, the retention rate of Example 1 in which the water vapor transmission amount of the light-receiving surface side sealing material was high was higher than that of Example 3. Similarly, when Examples 1 and 2 were compared with each other, the retention rate of Example 2 in which the water vapor transmission amount of the back surface side sealing material was high was higher than that of Example 1. Further, when Examples 4 and 1 were compared, the retention rates after 1000 hours and 2000 hours were almost the same.

  Therefore, it is considered that by appropriately changing the material of the sealing material, further long-term moisture resistance can be expected, performance deterioration of the solar cell module can be prevented, and the service life can be improved.

  As described above, by using the solar cell module of the present invention, it is possible to release moisture while preventing moisture from the outside. Therefore, it is possible to suppress a decrease in retention rate under harsher conditions than usual, and thus high long-term reliability. It is thought that a solar cell module can be produced.

1. 1. One conductivity type single crystal silicon substrate 2. Intrinsic silicon-based thin film 5. Conductive silicon thin film 6. Transparent electrode layer Light receiving surface electrode 8. Back electrode 100. Solar cell module 101. Solar cell 50. Photoelectric conversion unit 200. Light-receiving surface side protective material 201. Light-receiving surface side sealing material 202. Back side sealing material 203. Back side protective material 204. Wiring material

Claims (6)

A solar cell, a light receiving-side sealing member and the light-receiving-surface-side protection member disposed in this order on the light-receiving surface side of the solar cell, back-surface-side sealing member provided in order on the back surface side of the solar cells and and the back side protection member, a solar cell module having,
The solar cell includes a photoelectric conversion unit including an amorphous silicon thin film, a light receiving surface electrode provided on a light receiving surface side of the photoelectric conversion unit, and a back metal electrode provided on a back surface side of the photoelectric conversion unit. With
The back metal electrode is formed on 40% or more of the back side surface of the photoelectric conversion part,
The water vapor transmission amount W1 at 40 ° C. and 90% RH of the light receiving surface side sealing material and the water vapor transmission amount W2 at 40 ° C. and 90% RH of the back surface sealing material satisfy W1 <W2.
The solar cell module in which the water vapor transmission amount at 40 ° C. and 90% RH of the back surface side protective material satisfies 0.1 [g / m ² / day] to 15.0 [g / m ² / day]. The solar cell module according to claim 1, wherein the back surface metal electrode is formed on 90% or more of the back surface side surface of the photoelectric conversion unit. ^{W 1 ≦ 3.0 [g / m} 2 / day], and W2 ≦ 30.0 satisfy ^{[g / m 2 / day]} , the solar cell module according to claim 1 or 2. The backside protection material, polyfluorinated vinylidene down, ethylene tetrafluoroethylene copolymer, composed mainly of polyethylene terephthalate, and polyvinylidene fluoride Le whether we selected Ru one or more materials, claims 1-3 solar cell module according to any one of. The back metal electrode from the photoelectric conversion portion side includes a first conductive layer and the second conductive layer in this order, the second conductive layer is copper, according to any one of claims 1-4 Solar cell module. The photoelectric conversion portion includes a light receiving surface side of the conductive type crystalline silicon substrate conductivity type amorphous silicon thin film and the light-incident-side transparent electrode layer in this order, the conductive crystal silicon substrate on the back surface conductive type non The solar cell module of any one of Claims 1-5 which has a crystalline silicon thin film and a back surface side transparent electrode layer in this order.