WO2013140622A1

WO2013140622A1 - Solar cell module

Info

Publication number: WO2013140622A1
Application number: PCT/JP2012/057593
Authority: WO
Inventors: 平　茂治; 志敦寺中
Original assignee: 三洋電機株式会社
Priority date: 2012-03-23
Filing date: 2012-03-23
Publication date: 2013-09-26

Abstract

A solar cell module (10) is provided with: a solar cell (11) that comprises, on a photoelectric conversion unit (20), a first electrode (30) and a second electrode (40), which are configured of a binder (33) and a conductive filler (34); and a first covering material (12) and a second covering material (13), which cover the solar cell (11). The second covering material (13) has a water vapor transmission rate of 0.1 g/m²/day or more in the thickness direction up to the solar cell (11). The first electrode (30) and the second electrode (40) have at least one specific peak at a wavelength of from 1,500 cm^-1 to 1,700 cm^-1 in the Raman spectra of the surfaces thereof.

Description

Solar cell module

The present invention relates to a solar cell module.

The solar cell includes an electrode on the photoelectric conversion unit in order to collect carriers generated by light reception. In general, a wiring material is attached to a part of an electrode to electrically connect a plurality of solar cells, and the solar cells are covered with a covering material such as a glass substrate to form a module (see, for example, Patent Document 1). . The covering material prevents, for example, damage to the solar cell and suppresses moisture and the like from acting on the solar cell.

JP 2011-049283 A

By the way, in a solar cell module, a material having a high water vapor permeability such as a resin film may be used as a covering material. In such a configuration, if the electrode structure is arbitrarily set, long-term reliability may be impaired. For this reason, it is required to employ an appropriate electrode structure in accordance with the moisture content in the module to suppress deterioration of the photoelectric conversion characteristics.

A solar cell module according to the present invention includes a solar cell and a covering material that covers the solar cell, and the solar cell includes a photoelectric conversion unit and an electrode configured by a binder and a conductive filler on the photoelectric conversion unit. And the coating material has a water vapor permeability to the solar cell in the thickness direction of 0.1 g / m ² / day or more, and at least part of the electrode surface has a Raman spectrum wavelength of 1500 to 1700 cm ^−1. Have at least one specific peak.

According to the present invention, a solar cell module having excellent long-term reliability can be provided.

It is sectional drawing which shows the solar cell module which is an example of embodiment of this invention. It is the top view which looked at the solar cell which is an example of embodiment of this invention from the light-receiving surface side. It is the sectional view on the AA line of FIG. FIG. 3 is a cross-sectional view taken along line BB in FIG. 2, illustrating an example of an electrode cross-sectional structure. FIG. 3 is a cross-sectional view taken along line BB in FIG. 2, illustrating another example of the electrode cross-sectional structure. In the solar cell module which is an example of embodiment of this invention, it is a figure which shows an example of the Raman spectrum of an electrode surface. In the solar cell module which is an example of embodiment of this invention, it is a figure which shows the result of a moisture resistance test. In the solar cell module which is an example of embodiment of this invention, it is a figure which shows the result of a moisture resistance test.

The solar cell module 10 which is an example of the embodiment of the present invention will be described in detail below with reference to the drawings. The drawings referred to in the embodiments are schematically described, and the dimensional ratios of the components drawn in the drawings may be different from the actual products. Specific dimensional ratios and the like should be determined in consideration of the following description.

The configuration of the solar cell module 10 will be described with reference to FIGS. FIG. 1 is a cross-sectional view showing a part of the solar cell module 10. FIG. 2 is a plan view of the solar cell 11 applied to the solar cell module 10 as seen from the light receiving surface side. FIG. 3 is a view showing a part of a cross section taken along the line AA of FIG. 2, in which the wiring member 14 is omitted.

The solar cell module 10 includes a plurality of solar cells 11, a first coating material 12 disposed on the light receiving surface side of the solar cell 11, and a second coating material 13 disposed on the back surface side of the solar cell 11. The plurality of solar cells 11 are sandwiched between the first covering material 12 and the second covering material 13. The solar cell module 10 includes a wiring member 14 that electrically connects the solar cells 11, a transition wiring member that connects the wiring members 14, a frame, and a terminal box.

The solar cell 11 includes a photoelectric conversion unit 20 that generates carriers by receiving sunlight, a first electrode 30 that is a light-receiving surface electrode formed on the light-receiving surface of the photoelectric conversion unit 20, and the photoelectric conversion unit 20. And a second electrode 40 that is a back electrode formed on the back surface. In the solar cell 11, carriers generated by the photoelectric conversion unit 20 are collected by the first electrode 30 and the second electrode 40. Here, the “light receiving surface” means a surface on which sunlight mainly enters from the outside of the solar cell 11, and the “back surface” means a surface opposite to the light receiving surface. For example, more than 50% to 100% of the sunlight incident on the solar cell 11 enters from the light receiving surface side.

The photoelectric conversion unit 20 includes a substrate 21 made of a semiconductor material such as crystalline silicon (c-Si), gallium arsenide (GaAs), or indium phosphorus (InP). As the substrate 21, an n-type single crystal silicon substrate is particularly suitable. In addition, it is preferable that the light receiving surface and the back surface of the substrate 21 have a texture structure (not shown) having an uneven height of about 1 μm to 15 μm.

On the light receiving surface of the substrate 21, an amorphous silicon layer 22 and a transparent conductive layer 23 made of a light-transmitting conductive oxide (TCO) mainly composed of indium oxide or the like are formed in this order. An amorphous silicon layer 24 and a transparent conductive layer 25 are sequentially formed on the back surface of the substrate 21. The amorphous silicon layer 22 has a layer structure in which, for example, an i-type amorphous silicon layer and a p-type amorphous silicon layer are sequentially formed. The amorphous silicon layer 24 has a layer structure in which, for example, an i-type amorphous silicon layer and an n-type amorphous silicon layer are sequentially formed.

The first electrode 30 includes a plurality of (for example, 50) fingers 31 and a plurality of (for example, two) bus bars 32. The finger 31 is a thin line electrode formed over a wide range on the light receiving surface in order to collect carriers generated by the photoelectric conversion unit 20. The bus bar 32 is an electrode that collects carriers from the fingers 31, and is electrically connected to all the fingers 31.

In the first electrode 30, two bus bars 32 are arranged in parallel with each other at a predetermined interval, and a plurality of fingers 31 are arranged so as to cross this. The plurality of fingers 31 are arranged so that a part thereof extends from each of the bus bars 32 to the edge side of the light receiving surface, and the rest connects the two bus bars 32. In the present embodiment, the second electrode 40 is also composed of a plurality of (for example, 250) fingers 41 and a plurality of (for example, two) bus bars 42, and has the same electrode arrangement as the first electrode 30.

Although various members having translucency can be used for the first covering material 12, it is preferable to use the glass substrate 12a from the viewpoint of durability and the like. Further, the first covering material 12 has a filler 12 b that closes the gap between the glass substrate 12 a and the solar cell 11 and seals the solar cell 11. As the filler 12b, for example, a light-transmitting resin can be used, and an olefin resin obtained by polymerizing at least one α-olefin, such as an ethylene-propylene copolymer or an ethylene-vinyl acetate copolymer. A resin mainly composed of coalescence (EVA) or the like is preferable. Of these, EVA crosslinked with an organic peroxide or the like is particularly preferable. The filler 12b contains, for example, 50% by weight or more (50 to 100% by weight) of crosslinked EVA with respect to the total weight.

For the second covering material 13, it is preferable to use a resin film 13a from the viewpoints of cost reduction and weight reduction. Examples of the resin film 13a include films made of olefin resins, styrene resins, polyester resins, and the like. Among these, a polyester resin film is preferable, and a polyethylene terephthalate (PET) film is particularly preferable. Since PET film is excellent in translucency, it is also suitable for applications that assume light reception from the back side. In the gap between the second covering material 13 and the solar cell 11, as in the case of the first covering material 12, a filler 13 b containing 50% by weight or more of crosslinked EVA is provided.

The resin film 13a can be provided with a gas barrier layer 13c in order to reduce the water vapor permeability described later. Examples of the gas barrier layer 13c include a layer made of a resin or a metal compound (silica or alumina) having a lower water vapor permeability than the PET film. When it is desired to reduce the water vapor transmission rate without impairing the translucency, it is preferable to provide a silica layer having a thickness of submicron order. The silica layer can be provided on one side of the PET film by vapor deposition. In this case, it is preferable to laminate the silica layer with another PET film to obtain a resin film 13a having a laminated structure.

Wiring member 14 connects solar cells 11 arranged adjacent to each other. One end side of the wiring member 14 is attached to the first electrode 30 (bus bar 32) of one solar cell 11 among the solar cells 11 arranged adjacent to each other. The other end side of the wiring member 14 is connected to the second electrode 40 (bus bar 42) of the other solar cell 11. That is, the wiring member 14 bends in the thickness direction of the solar cell module 10 between the adjacent solar cells 11 and connects the adjacent solar cells 11 in series. The wiring member 14 is attached using, for example, a non-conductive adhesive or a conductive adhesive containing a conductive filler such as silver (Ag).

In the solar cell module 10, a string of solar cells 11 obtained by connecting the wiring material 14 is made of a glass substrate 12 a, a resin film 13 a (for example, a PET film), and sheet-

like fillers

12 b and 13 b (for example, an EVA sheet). ). In the laminating apparatus, the glass substrate 12a / EVA sheet / string / EVA sheet / PET film are arranged in this order on the heater and heated to about 150 ° C. in a vacuum state. Thereafter, heating is continued while pressing the module material against the heater under atmospheric pressure to crosslink EVA. Finally, a solar cell module 10 is obtained by attaching a frame or the like.

The thickness of the first coating material 12 and the second coating material 13 and the water vapor permeability in the thickness direction in the solar cell module 10 will be described below. The water vapor permeability can be measured under the following conditions.
Apparatus: Water vapor permeability tester (Techno Eye "DELTAPERRM")
Temperature / humidity: 40 ° C / 90%

The thickness t1 of the first covering material 12 is, for example, about 0.5 to 3 mm. Most of the thickness t1 is the thickness of the glass substrate 12a. The thickness of the glass substrate 12a is preferably about 0.5 to 3 mm, and the thickness of the filler 12b is preferably about 50 to 200 μm. In the first covering material 12, the water vapor permeability in the thickness direction, that is, the water vapor permeability from the surface of the glass substrate 12a to the solar cell 11 has a value significantly smaller than 0.1 g / m ² / day.

The thickness t2 of the second covering material 13 is, for example, about 100 to 500 μm. The thickness of the resin film 13a is preferably about 50 to 300 μm, and the thickness of the filler 12b is preferably about 50 to 200 μm. The second coating material 13 has a water vapor permeability in the thickness direction of 0.1 g / m ² / day or more. For example, in the case of a PET film having a thickness of 150 μm, the water vapor permeability is about 10 g / m ² / day, and when the thickness is doubled (300 μm), the thickness is approximately ½ times (5 g / m ² / day). When it becomes 1/2 times (75 μm), it becomes almost twice (20 g / m ² / day). In addition, an EVA sheet having a thickness of about 50 to 200 μm has a water vapor permeability of about 50 g / m ² / day.

The thickness of the resin film 13a is more preferably 50 to 200 μm, and particularly preferably 75 to 150 μm. The water vapor permeability in the thickness direction of the second covering material 13 is about 0.1 to 100 g / m ² / day. When a silica layer having a thickness of the order of submicron is provided as the gas barrier layer 13c, the water vapor permeability can be easily adjusted in the range of about 0.1 to 10 g / m ² / day.

4 and 5 show a cross-sectional structure of the finger 31. FIG.
FIG. 4 is a diagram showing a part of the cross section taken along line BB in FIG. 2, and shows a cross section obtained by cutting the solar cell 11 in the thickness direction perpendicular to the

fingers

31 and 41. FIG. 5 shows a modification of the embodiment shown in FIG.

Both the finger 31 and the bus bar 32 are composed of an insulating binder 33 and a conductive filler 34. It is preferable that the conductive filler 34 is dispersed substantially uniformly in the binder 33. The conductive fillers 34 are in contact with each other to form a conductive path, for example. The electrode material may contain a small amount of an additive such as a filler dispersant. The electrode material and composition may be changed between the fingers and the bus bar, and between the first electrode 30 and the second electrode 40, but in the present embodiment, the

fingers

31, 41 and the bus bars 32, 42 (hereinafter collectively referred to as these). Are sometimes made of the same material and the same composition.

4, most of the surface of the finger 31 is covered with the binder 33, and only a part of the conductive filler 34 is exposed from the surface of the finger 31. The ratio at which the conductive filler 34 is exposed from the surface of the finger 31 can be adjusted, for example, by changing the mixing ratio of the binder 33 and the conductive filler 34.

On the other hand, in the embodiment illustrated in FIG. 5, a resin coating layer 35 that covers the surface of the finger 31 is provided. The resin coating layer 35 is made of, for example, only the same resin as the binder 33 and covers the conductive filler 34 exposed from the surface of the finger 31. The resin coating layer 35 can be formed on the finger 31 by the same method as the finger 31 or by another coating method. In addition, since it is necessary for the bus bars 32 and 42 to realize good electrical connection with the wiring member 14, the resin coating layer 35 is preferably provided only on the

fingers

31 and 41.

The collector electrode is preferably formed by a screen printing method. In the screen printing method, for example, a paste containing an electrode material is transferred onto the photoelectric conversion unit 20 by using a screen plate having an opening corresponding to the shape of the collector electrode and a squeegee. Then, the transferred paste is solidified by heating or the like to form a collecting electrode. As the paste, a heat curing type conductive paste in which a binder 33 as an electrode material and a conductive filler 34 are mixed in a solvent is suitable.

For the conductive filler 34, for example, metal particles such as silver (Ag), copper (Cu), nickel (Ni), aluminum (Al), silver-coated copper, silver-coated aluminum, carbon, or a mixture thereof is used. be able to. Examples of the conductive filler 34 include particles having a spherical shape, a spindle shape, a needle shape, a flake shape (flaky shape), and the like, and in particular, a flaky particle having an average particle size of 3 to 20 μm and an average particle size of 0. It is preferable to use spherical particles of 5 to 1 μm in combination. Here, the average particle diameter means a 50% cumulative value when the arithmetic average value of the major axis and the minor axis is measured by the microtrack type particle size distribution measuring method.

In particular, it is preferable to apply Ag particles as the conductive filler 34. The content of Ag particles is preferably 70 to 90% by weight, more preferably 75 to 87% by weight, and particularly preferably 80 to 85% by weight based on the total weight of the electrode material. In other words, the content of the binder 33 is preferably 10 to 30% by weight, more preferably 13 to 25% by weight, and particularly preferably 15 to 20% by weight with respect to the total weight of the electrode material.

For the binder 33, for example, a thermosetting resin such as an epoxy resin, a urethane resin, a urea resin, an acrylic resin, an imide resin, or a phenol resin, or a modified product or a mixture thereof can be used. . The thermosetting resin becomes a binder 33 due to the curing reaction of the components by the heat treatment. When the curing reaction of the thermosetting resin proceeds even at a low temperature, it is preferable to block the functional groups of the constituent components. For example, in the case of a urethane-based resin, the isocyanate group can be protected using a blocking agent such as imidazoles, phenols, and oximes. Such thermosetting resins may be those classified into a plurality of groups (for example, resins that can be classified into both epoxy resins and urethane resins).

As the thermosetting resin, at least one thermosetting resin (hereinafter referred to as “specific thermosetting resin”) selected from the group consisting of an epoxy resin, a urethane resin, and an acrylic resin is used as a binder. It is preferable to contain 80% by weight or more based on the total weight of 33. For example, it is preferable to use an epoxy resin as a main component (50% by weight or more) among the specific thermosetting resins. It is also preferable that the specific thermosetting resin is contained in an amount of 80 to 95.5% by weight and the silicone resin is contained in an amount of 0.5 to 20% by weight. Examples of the silicone resin include straight silicone resins such as methyl and methylphenyl, modified silicone resins modified with epoxy resins, alkyd resins, ester resins, acrylic resins, and the like.

Examples of the epoxy resins include alicyclic epoxy resins, chain epoxy resins, bisphenol A type epoxy resins, epoxy phenol novolac type resins, polyglycidyl ether type epoxy resins, polyalkylene ether type epoxy resins, epoxy acrylate resins, and fatty acid-modified resins. Examples thereof include an epoxy resin, a urethane-modified epoxy resin, and a silicone-modified epoxy resin. As the curing agent, for example, imidazoles and tertiary amines can be used. When only an epoxy resin is used as the thermosetting resin, it is preferable to use a component having an epoxy equivalent of 1000 or less (referred to as component A) and a component having an epoxy equivalent of 1500 or higher (referred to as component B). The weight mixing ratio of the A component and the B component is preferably 30 to 90% by weight for the A component (10 to 70% by weight for the B component).

Examples of the urethane resin include resins composed of diisocyanate and polyol. Examples of the diisocyanate include aromatic diisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, tolidine diisocyanate, xylylene diisocyanate, and naphthalene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, hydrogenated xylylene diisocyanate, and dicyclohexyl. Aliphatic diisocyanates such as methane diisocyanate, octamethylene diisocyanate, and trimethylhexamethylene diisocyanate can be used. As the polyol, for example, polyether polyols, polyester polyols, polycarbonate polyols and the like can be used.

Examples of the acrylic resins include (meth) acrylic acid esters and ethylenically unsaturated monomers (for example, acrylic acid) having a crosslinkable functional group (for example, carboxyl group, hydroxyl group, amino group, methylol group, epoxy group). Methacrylic acid, acrylamide, methacrylamide, N-methylolacrylamide, allyl glycidyl ether, glycidyl methacrylate) and the like. An aromatic vinyl monomer such as styrene may be copolymerized.

Further, as the solvent contained in the conductive paste, it is preferable to use a high boiling point solvent such as ethyl carbitol acetate, butyl carbitol acetate, terpineol, or the like. The solvent is volatilized and removed when the conductive paste transferred onto the photoelectric conversion unit 20 is heated. The heating temperature is approximately 200 ° C., although it varies depending on the curing conditions of the binder 33 and the like.

FIG. 6 shows an example of a Raman spectrum (solid line) on the surface of the finger 31. A two-dot chain line in FIG. 6 is a Raman spectrum of a comparison module described later. In the present embodiment, similar Raman spectra are obtained for the other collector electrodes.

As shown in FIG. 6, in the solar cell 11, the Raman spectrum of the surface of the finger 31 has a peak Z that is at least one specific peak at wavelengths of 1500 to 1700 cm ⁻¹ . In the present specification, a peak Z is defined as a scattering intensity (also called signal intensity) at the peak top that is 10% or more higher than the scattering intensity on the long wavelength side of 50 cm ⁻¹ from the wavelength of the peak top. In the Raman spectrum shown in FIG. 6, one peak Z exists at a wavelength of 1500 to 1700 cm ⁻¹ . The peak Z has a peak top wavelength of 1650 cm ⁻¹ , and the peak top scattering intensity Ip is at least 10% higher than the scattering intensity Ik on the long wavelength side (1700 cm ⁻¹ ) 50 cm ⁻¹ from the peak top wavelength. It has become.

The Raman spectrum of the finger 31 can be measured under the following conditions.
Apparatus: Microscopic laser Raman spectrometer ("InVia Reflex" manufactured by Renishaw)
Excitation light source; laser light with a wavelength of 785 nm Measurement mode: Extension mode, 20-second exposure

The peak Z is an important factor that affects the photoelectric conversion characteristics of the solar cell module 10 as will be described in detail later. The wavelength of the peak top is not particularly limited as long as it is in the range of 1500 to 1700 cm ⁻¹ . Further, the number of peaks Z is not particularly limited, and a plurality of peaks Z may exist. On the other hand, the scattering intensity Ip is preferably higher from the viewpoint of improving long-term reliability. For example, the scattering intensity Ip is preferably 15% or more higher than the scattering intensity Ik, more preferably 20% or more, and particularly preferably 30% or more. .

For example, the peak Z is more likely to appear as the proportion of the binder 33 on the electrode surface increases, and the scattering intensity Ip increases. In other words, the scattering intensity Ip increases as the proportion of the conductive filler 34 exposed from the electrode surface decreases. Such an electrode structure can be formed using, for example, a conductive paste in which the content of Ag particles is 80 to 85% by weight with respect to the total weight of the electrode material as described above.

In the solar cell 11, it is preferable that the ratio of the scattering intensity Ip and the bottom scattering intensity Ib at the Raman spectrum wavelength of 800 to 1200 cm ⁻¹ is Ib / Ip ≧ 0.7. That is, the scattering intensity Ib is preferably 70% or more of the scattering intensity Ip, more preferably 80% or more, and particularly about 100% (that is, Ib = Ip). Thereby, the long-term reliability of the solar cell module 10 can be further improved. The bottom wavelength is not particularly limited as long as it is in the range of 800 to 1200 cm ⁻¹ .

For example, the ratio of the scattering intensity Ib to the scattering intensity Ip tends to increase as the degree of cure of the binder 33 increases. That is, it is suggested that the degree of cure of the binder 33 constituting the collector electrode is higher when Ib / Ip is 1.0 than when Ib / Ip is 0.7.

In FIG. 7, the result of the moisture resistance test in the solar cell module 10 is shown. In this moisture resistance test, the test time was 2000 hours under the conditions of a constant temperature and humidity furnace with a temperature of 85 ° C. and a humidity of 85%. In the figure, the horizontal axis represents the test time, and the vertical axis represents the deterioration improvement rate. Further, in FIG. 8, solar cell modules 10 having Ib / Ip of about 0.70 (▲), about 0.75 (■), about 0.80 (●), and about 1.00 (◯), respectively. The result of the moisture resistance test in is shown. In the figure, the horizontal axis represents the test time, and the vertical axis represents the FF change rate. Details are as follows.
The deterioration improvement rate means that the Raman spectrum of the surfaces of the first electrode 30 and the second electrode 40 has a fill factor FF ₁₀ of the solar cell module 10 having a peak Z at a wavelength of 1500 to 1700 cm ⁻¹ and no peak Z. Was calculated (FF ₁₀ / FF ₅₀ ) based on the fill factor FF ₅₀ of a comparative solar cell module (hereinafter referred to as a comparison module) having the same configuration as the solar cell module ₁₀ . FIG. 6 (two-dot chain line) shows a Raman spectrum of the comparison module.
The comparison module was manufactured by reducing the weight of the binder 33 (epoxy resin) to 2/3 with respect to the solar cell module 10 having Ib / Ip of about 0.70.
The solar cell module 10 having Ib / Ip of about 0.70, about 0.75, about 0.80, and about 1.00 was produced by changing only the curing time of the binder 33. The heat treatment temperatures are all 200 ° C., and the curing treatment times are 25 minutes, 35 minutes, 45 minutes, and 90 minutes in this order.

As shown in FIG. 7, when the Raman spectra of the surfaces of the first electrode 30 and the second electrode 40 have a peak Z at a wavelength of 1500 to 1700 cm ⁻¹ , the photoelectric spectrum is smaller than that without the peak Z. Conversion characteristics are less likely to deteriorate. That is, it means that the solar cell module 10 has higher moisture resistance than the comparative module. This is because the higher the moisture content, the more easily the metal of the electrode is ionized and diffuses. However, in the electrode having the peak Z, the coverage of the conductive filler 34 by the binder 33 and the resin coating layer 35 is high, and the metal ions are photoelectric. This is presumed to be difficult to diffuse into the converter 20. In particular, the difference between the two increases as the test time increases. However, when both the first covering material 12 and the second covering material 13 have a water vapor permeability of less than 0.1 g / m ² / day, diffusion of metal ions hardly occurs in the first place, and the solar cell module 10 and the comparison module The deterioration improvement rate was a value close to 1.

As shown in FIG. 8, in the solar cell module 10, the lower the Ib / Ip, the smaller the decrease in the FF change rate and the higher the moisture resistance. In particular, it has good moisture resistance when Ib / Ip ≧ 0.8. That is, the higher the degree of cure of the binder 33, the better the moisture resistance.

The results of the moisture resistance test shown in FIGS. 7 and 8 indicate that the performance evaluation of the solar cell 11 and the solar cell module 10 including the solar cell 11 can be performed using the Raman spectrum of the collector electrode. Specifically, the Raman spectrum of the surface of the collector electrode is measured, and the moisture resistance performance of the solar cell 11 can be evaluated based on the presence or absence of the peak Z at a wavelength of 1500 to 1700 cm ⁻¹ of the obtained spectrum. For example, when the peak Z is confirmed in the Raman spectrum of the collector electrode, it can be evaluated that the solar cell can produce a module having excellent long-term reliability even in an environment with a high moisture content. On the other hand, when the peak Z cannot be confirmed, it can be evaluated that the solar cell cannot be used in an environment with a high water content.

Further, the moisture resistance performance of the solar cell 11 can be evaluated based on the ratio between the scattering intensity Ip at the peak top at the peak Z and the scattering intensity Ib at the bottom at a wavelength of Raman spectrum of 800 to 1200 cm ⁻¹ . Such a ratio can also be used to know the degree of cure of the binder 33. For example, in the Raman spectrum of the collector electrode, when Ib / Ip ≧ 0.7, preferably ≧ 0.8, the solar cell can produce a module having excellent long-term reliability even in an environment with a high water content. Can be evaluated.

As described above, according to the solar cell module 10, in the configuration using the coating material (second coating material 13) having a water vapor permeability of 0.1 g / m ² / day or more, deterioration of photoelectric conversion characteristics is suppressed. be able to. And excellent long-term reliability can be realized.

Note that only the Raman spectra of the

fingers

31 and 41 may have a peak Z. Alternatively, the scattering intensity Ip of the peak Z related to the

fingers

31 and 41 may be higher than the scattering intensity Ip of the peak Z related to the bus bars 32 and 42. Such a configuration can be realized, for example, by providing the resin coating layer 35 limited to the

fingers

31 and 41 as described above. Thereby, deterioration of a photoelectric conversion characteristic can be suppressed, maintaining the favorable electrical connection with the wiring material 14. FIG.

Further, only the Raman spectrum of the second electrode 40 may have a peak Z. Alternatively, only the Raman spectrum of the finger 41 may have the peak Z, and the scattering intensity Ip of the peak Z related to the finger 41 may be higher than the scattering intensity Ip of the peak Z related to other electrodes. The reason for adopting such a configuration is that the portion having a higher moisture content in the module is more likely to deteriorate the photoelectric conversion characteristics. That is, since the second covering material 13 close to the finger 41 has a higher water vapor permeability than the first covering material 12, it is effective to increase the scattering intensity Ip related to the finger 41.

Moreover, in the photoelectric conversion part provided with the n-side electrode and the p-side electrode only on the back surface, it is preferable that the Raman spectrum of any electrode has a peak Z. Such a photoelectric conversion unit includes, for example, an i-type amorphous silicon layer, an n-type amorphous silicon layer, and a transparent conductive layer formed in this order on the light-receiving surface side of an n-type single crystal silicon substrate. On the back side of the substrate, a p-type region composed of an i-type amorphous silicon layer and a p-type amorphous silicon layer, an i-type amorphous silicon layer, and an n-type amorphous silicon layer are formed. And an n-type region. A transparent conductive layer and an electrode are provided on the p-type region and the n-type region, respectively.

10 solar cell module, 11 solar cell, 12 first covering material, 12a glass substrate, 12b filler, 13 second covering material, 13a resin film, 13b filler, 13c gas barrier layer, 14 wiring material, 20 photoelectric conversion part, 21 substrate, 24, 24 amorphous silicon layer, 23, 25 transparent conductive layer, 30 first electrode, 31, 41 finger, 32, 42 bus bar, 33 binder, 34 conductive filler, 35 coating layer, 40 second electrode .

Claims

Solar cells,
A covering material for covering the solar cell;
With
The solar cell is
A photoelectric conversion unit;
An electrode composed of a binder and a conductive filler on the photoelectric conversion unit;
Have
The covering material has a water vapor permeability of 0.1 g / m 2 / day or more to the solar cell in the thickness direction,
At least a part of the electrode surface is a solar cell module having at least one specific peak at a wavelength of 1500 to 1700 cm −1 of a Raman spectrum.
The solar cell module according to claim 1, wherein
The ratio between the peak top signal intensity Ip at the specific peak and the bottom signal intensity Ib at the wavelength of 800 to 1200 cm −1 of the Raman spectrum is Ib / Ip ≧ 0.7.
In the solar cell module according to claim 1 or 2,
The electrode includes a finger and a bus bar,
Only the Raman spectrum of the finger has at least one specific peak at a wavelength of 1500-1700 cm −1 .
The solar cell module according to any one of claims 1 to 3,
The covering material includes a back surface side covering material that covers the back surface side of the solar cell,
The back side covering material is
A resin film having a thickness of 50 μm or more and 300 μm or less;
An ethylene vinyl acetate copolymer as a main component, and a filler provided between the resin film and the solar cell;
Have
The water vapor permeability is 0.1 g / m 2 / day or more and 100 g / m 2 / day or less.
In the solar cell module according to claim 4,
The electrode includes a back electrode provided on the back surface of the solar cell,
Only the Raman spectrum of the back electrode has at least one specific peak at a wavelength of 1500-1700 cm −1 .
In the solar cell module according to claim 4 or 5,
The resin film includes a gas barrier layer,
The water vapor permeability of the back-side coating material is 0.1 g / m 2 / day or more and 10 g / m 2 / day or less.
The solar cell module according to any one of claims 1 to 6,
The binder constituting the electrode contains at least 80% by weight of at least one thermosetting resin selected from the group consisting of epoxy resins, urethane resins, and acrylic resins.
In the solar cell module according to claim 7,
The binder contains 0.5% to 20% by weight of a silicone resin.
The solar cell module according to any one of claims 1 to 8,
The conductive filler is silver particles,
The silver particle content is 70 wt% or more and 90 wt% or less with respect to the total weight of the electrode.
The solar cell module according to any one of claims 1 to 9,
The electrode is provided with a resin coating layer covering its surface.