JP2020155684A - Manufacturing method of solar cell string, solar cell module, and solar cell - Google Patents

Abstract

To suppress a connecting member from reaching the side surface of a solar cell even when the connecting member protrudes from between a light receiving surface side current collecting electrode and a back surface side current collecting electrode.SOLUTION: When viewed in a plan view with respect to a light receiving surface, a part of a light receiving surface side current collecting electrode 25a of one solar cell 2 from among a plurality of solar cells 2 and a part of a back side current collecting electrode of the other solar cell 2 adjacent to the one solar cell are connected via a connecting member 3 in a state of being overlapped with each other, and the connecting member 3 has fluidity when arranged between the light receiving surface side current collecting electrode 25a and the back side current collecting electrode, and a cushioning portion 4 having a lower wettability with respect to the connecting member 3 than the light receiving surface or the back surface is formed at least in the vicinity of the light receiving surface side current collecting electrode 25a on the light receiving surface, or in the vicinity of the back surface side current collecting electrode on the back surface.SELECTED DRAWING: Figure 4

Description

The present invention relates to a solar cell string for forming a solar cell module, a solar cell module in which a plurality of solar cell strings are assembled, and a method for manufacturing a solar cell that constitutes the solar cell string.

Conventionally, a plurality of solar cells having a substantially rectangular shape in a plan view are sequentially arranged in a direction substantially parallel to the short side so that the long sides of each solar cell overlap, for example, by roofing a roof plate. There is a solar cell string formed by a shingling connection. This is described, for example, in Patent Document 1 (see FIGS. 1, 2A, etc.).

It is also known that the solar cell has irregularities on the light receiving surface or the back surface due to the texture structure (see, for example, FIG. 3 in Patent Document 2).

A light receiving surface side current collecting electrode is provided on the light receiving surface of each solar cell, and a back surface side current collecting electrode is provided on the back surface. By the single ring connection, a part of the light receiving surface side current collecting electrode of one solar cell and a part of the back surface side current collecting electrode of another adjacent solar cell are overlapped with each other among the plurality of solar cells. It is connected via a connecting member. The connecting member is a paste-like member having conductivity and having fluidity at the time of being arranged between the light receiving surface side current collecting electrode and the back surface side current collecting electrode.

Special Table 2017-517145 Japanese Unexamined Patent Publication No. 2016-187027

Here, the connecting member is usually located sandwiched between the light receiving surface side current collecting electrode and the back surface side current collecting electrode. However, since the connecting member has fluidity, it may protrude from the light receiving surface side current collecting electrode and the back surface side current collecting electrode. In such a case, the protruding connecting member flows to the light receiving surface or the back surface, and is highly wettable to the connecting member (in other words, easily wet or liquid-friendly), and travels through unevenness due to the texture structure. It can reach the sides of the solar cell. This is inconvenient because an unintended short circuit between the front and back sides occurs, which causes a decrease in the output of the solar cell and the solar cell string which is an aggregate of a plurality of solar cells.

Therefore, according to the present invention, even if the connecting member protrudes between the light receiving surface side current collecting electrode and the back surface side current collecting electrode, it can be suppressed from reaching the side surface of the solar cell, the solar cell string, the solar cell module, and the sun. An object of the present invention is to provide a method for manufacturing a battery cell.

The present invention is a solar cell string including a plurality of solar cell cells and a conductive connecting member, and each of the plurality of solar cell cells has a light receiving surface side current collecting electrode provided on the light receiving surface and a back surface thereof. When viewed in plan with respect to the light receiving surface, a part of the light receiving surface side current collecting electrode of one of the plurality of solar cells is provided with the back surface side current collecting electrode. And a part of the back surface side current collecting electrode of the other solar cell adjacent to the one solar cell are connected via the connecting member in a state of being overlapped with each other, and the connecting member is connected to the light receiving light. It has fluidity when it is arranged between the front surface side current collecting electrode and the back surface side current collecting electrode, and is at least in the vicinity of the light receiving surface side current collecting electrode on the light receiving surface or on the back surface. A solar cell string in which a buffer portion having a lower wettability with respect to the connecting member than the light receiving surface or the back surface is formed in the vicinity of the back surface side current collecting electrode.

Further, the present invention is a solar cell module including a plurality of solar cell cells and a conductive connecting member, and each of the plurality of solar cell cells includes a light receiving surface side current collecting electrode provided on the light receiving surface. One of the light receiving surface side current collecting electrodes of one solar cell among the plurality of solar cells, which is provided with a back surface side current collecting electrode provided on the back surface and is viewed in a plan view with respect to the light receiving surface. The unit and a part of the back surface side current collecting electrode of the other solar cell adjacent to the one solar cell are connected via the connecting member in a state of being overlapped with each other, and the connecting member is connected to the connecting member. It has fluidity when it is arranged between the light receiving surface side current collecting electrode and the back surface side current collecting electrode, and is at least in the vicinity of the light receiving surface side current collecting electrode on the light receiving surface or the back surface. A solar cell module in which a buffer portion having a lower wettability with respect to the connecting member than the light receiving surface or the back surface is formed in the vicinity of the back surface side current collecting electrode.

According to these configurations, since the buffer portion having low wettability is formed with respect to the connecting member, even if the connecting member protrudes from between the light receiving surface side current collecting electrode and the back surface side current collecting electrode, the connection member is connected. The member does not get wet and spreads, and can stay on the cushioning part.

Further, each of the plurality of solar cell cells may have at least the unevenness due to the texture structure on the light receiving surface or the back surface, and the buffer portion may have an uneven region smaller than the unevenness due to the texture structure.

According to this configuration, since the cushioning portion has a region of unevenness smaller than the unevenness due to the texture structure, the wettability to the connecting member can be lowered because the unevenness is relatively small in the region.

Further, the buffer portion may include a coating layer that covers the unevenness due to the texture structure.

According to this configuration, since the coating layer covers the unevenness due to the texture structure, it is not necessary to perform processing such as polishing on the texture structure itself, so that a cushioning portion having low wettability can be easily formed on the connecting member. ..

Further, the present invention is a solar cell having at least irregularities on the light receiving surface or the back surface due to a texture structure, and also having a light receiving surface side current collecting electrode provided on the light receiving surface and a back surface side current collecting electrode provided on the back surface. In the cell manufacturing method, when the light receiving surface side current collecting electrode and the back surface side current collecting electrode are formed, the conductive electrode raw material paste which is the raw material of each electrode is applied to the planned formation position, and the coating is applied. After that, at least a part of the liquid resin contained in the electrode raw material paste seeps out and hardens in the vicinity of the coating position of the electrode raw material paste on the light receiving surface and the back surface, so that the unevenness due to the texture structure is obtained. Is also a method for manufacturing a solar cell, in which a small uneven region is formed.

According to this, the electrode raw material paste used when forming the light receiving surface side current collecting electrode and the back surface side current collecting electrode can form each electrode and a region of unevenness smaller than the unevenness due to the texture structure.

Further, the electrode raw material paste can be a mixture of the conductive particles and the liquid resin.

According to this, it is possible to obtain an electrode raw material paste in which the liquid resin exudes with coating by the mixture of the conductive particles and the liquid resin.

According to the present invention, even if the connecting member protrudes from between the light receiving surface side current collecting electrode and the back surface side current collecting electrode, the connecting member does not spread wet and can be kept on the buffer portion. Therefore, it is possible to prevent the connecting member from reaching the side surface of the solar cell.

It is sectional drawing which shows typically the layer structure of the solar cell which concerns on one Embodiment of this invention. It is sectional drawing which shows typically the connection part between adjacent solar cell cells in the solar cell string which concerns on one Embodiment of this invention. It is an enlarged sectional view schematically showing the light receiving surface side current collecting electrode and the buffer part in the solar cell which concerns on the said embodiment. It is an enlarged cross-sectional view which shows the light receiving surface side current collecting electrode and the cushioning part in the solar cell which concerns on the said embodiment, and schematically shows the state which the connecting member protrudes.

The present invention will be described below with reference to one embodiment. As shown in FIG. 2, for example, the solar cell string 1 of the present embodiment is formed by connecting a plurality of solar cell cells 2 ... 2. Each solar cell 2 has a substantially rectangular shape in a plan view and is a double-sided electrode type. The plurality of solar cell cells 2 ... 2 are electrically connected by a single ring connection along the cell connection direction J (direction substantially parallel to the extending direction of the short side of the rectangle). The plurality of solar cells 2 ... 2 are connected as shown in FIG. 2 (in FIG. 2, the connecting portion of the two solar cells 2 and 2 adjacent to each other in the cell connection direction J in the solar cell string 1). Is extracted and shown). The solar cell string 1 is a unit of a set of a plurality of solar cell cells 2 ... 2 connected by a sing ring. Further, although not shown, a plurality of (plural units) solar cell strings 1 are electrically connected in series and then sealed, and a take-out electric wiring is connected to form a solar cell module.

The layer structure of each solar cell 2 is schematically shown in FIG. The solar cell 2 includes a semiconductor substrate 21 which is a monoconductive single crystal silicon substrate. The semiconductor substrate 21 of this embodiment is an n-type single crystal silicon substrate.

From the semiconductor substrate 21 to the light receiving surface 2a side (upper side in the drawing), an intrinsic silicon layer 22a (specifically, an i-type silicon layer), a monoconductive silicon layer 23a (for example, an n-type silicon layer), and a transparent conductive layer 24a on the light receiving surface side. (TCO layer) and the light receiving surface side current collecting electrode 25a are laminated in this order. On the other hand, from the semiconductor substrate 21, on the back surface 2b side (lower side in the drawing) opposite to the light receiving surface 2a side, the intrinsic silicon layer 22b (specifically, the i-type silicon layer) and the reverse conductive type silicon layer 23b (for example, p-type). (Silicon layer), the back surface side transparent conductive layer 24b (TCO layer), and the back surface side current collecting electrode 25b are laminated in this order. Each solar cell has irregularities on the light receiving surface 2a and the back surface 2b due to the texture structure. This unevenness is a substantially quadrangular pyramid-shaped unevenness (the cross-sectional shape is shown in FIG. 1).

The current collecting electrodes 25a and 25b are composed of bus bar electrodes 25a1,25b1 along long sides that are substantially rectangular in plan view and bottom view, and a large number of finger electrodes (not shown) orthogonal to the bus bar electrodes 25a1,25b1. ing.

As shown in FIG. 2, the light receiving surface side current collecting electrode 25a in one solar cell 2 adjacent to each other in the cell connection direction J in the solar cell string 1 and the back surface side current collecting electrode 25b in the other solar cell 2. However, they are electrically connected with the connecting member 3 interposed therebetween. The connecting member 3 has fluidity at the time when it is arranged between the light receiving surface side current collecting electrode 25a and the back surface side current collecting electrode 25b. After that, when the solar cell string 1 is heated, the connecting member 3 is hardened and loses its fluidity. The connecting member 3 is provided so as to be in contact with the current collecting electrodes 25a and 25b of the adjacent solar cells 2 and 2. The connecting member 3 also has a function of adhering adjacent solar cell cells 2 and 2 to form one solar cell string 1.

The connecting member 3 has conductivity by containing conductive particles, and is in the form of a paste and has fluidity. As the conductive particles, for example, silver, copper, aluminum, nickel, tin, bismuth, zinc, gallium, carbon and a mixture thereof can be used, and silver is particularly preferably used from the viewpoint of conductivity. Further, as the resin, an epoxy resin, a phenol resin, and an acrylic resin are preferably used. The content of the conductive particles is preferably 70 wt% or more, particularly preferably 80 wt% or more from the viewpoint of improving the conductivity. On the other hand, from the viewpoint of ensuring the fluidity of the connecting member 3, 99 wt% or less, particularly 90 wt% or less is preferable.

As described above, the solar cell string 1 of the present embodiment includes a plurality of solar cell cells 2 ... 2 and a conductive connecting member 3. Each solar cell 2 includes a light receiving surface side current collecting electrode 25a provided on the light receiving surface 2a and a back surface side current collecting electrode 25b provided on the back surface 2b. Then, when viewed in a plan view with respect to the light receiving surface 2a, a part of the light receiving surface side current collecting electrode 25a of one solar cell 2 among the plurality of solar cells 2 ... 2 (specifically, FIG. 2). The bus bar electrode 25a1) on the light receiving surface 2a side of the left solar cell 2 shown in the above, and a part of the back surface side current collecting electrode 25b of another solar cell 2 adjacent to one solar cell 2 (specifically). Is connected via a connecting member 3 in a state in which the bus bar electrode 25b1) on the back surface 2b side of the right solar cell 2 shown in FIG. 2 is vertically overlapped.

In the vicinity of the light receiving surface side current collecting electrode 25a on the light receiving surface 2a and in the vicinity of the back surface side current collecting electrode 25b on the back surface 2b, the wettability with respect to the connecting member 3 is lower than that of the light receiving surface 2a or the back surface 2b ( In other words, the buffer portion 4 (which is difficult to get wet or is sparse) is formed. The wettability is evaluated by the contact angle and the like. As shown in FIG. 3, the buffer portion 4 includes a coating layer 41 that covers the unevenness due to the texture structure. The coating layer 41 partially fills the unevenness (unevenness with a height of several μm) due to the texture structure, and the height difference is reduced. As described above, the buffer portion 4 has a region of unevenness smaller than the unevenness due to the texture structure.

In the present embodiment, since the coating layer 41 of the cushioning portion 4 covers the unevenness due to the texture structure, the texture structure itself does not need to be subjected to processing such as polishing in order to reduce the unevenness. The cushioning portion 4 having low wettability can be easily formed. Then, even if the connecting member 3 protrudes from between the light receiving surface side current collecting electrode 25a and the back surface side current collecting electrode 25b due to the formation of the buffer portion 4 having low wettability with respect to the connecting member 3, the connection member 3 is connected. The member 3 does not get wet and spreads, and can be kept on the buffer portion 4. Therefore, it is possible to prevent the connecting member 3 from reaching the side surface 26 of the solar cell 2.

In the present embodiment, the "neighborhood" refers to both sides of each bus bar electrode 25a1,25b1 in the width direction. However, for the purpose of preventing an unintended short circuit between the front and back surfaces, at least the cushioning portion 4 should be formed on the side surface 26 of the solar cell 2 (the side surface 26 on the side closer to each bus bar electrode 25a1, 25b1). Just do it.

Next, a method of manufacturing the solar cell 2 in the present embodiment will be described. When forming the light receiving surface side current collecting electrode 25a and the back surface side current collecting electrode 25b, the conductive electrode raw material paste which is the raw material of each electrode is applied to the planned formation position. The coating can be performed by a printing method such as screen printing. At this time, the electrode raw material paste is applied from above to the upper surface of the solar cell work-in-process in which the electrodes have not been applied. After coating, at least a part of the liquid resin contained in the electrode raw material paste seeps out and hardens in the vicinity of the coating position of the electrode raw material paste on the light receiving surface 2a and the back surface 2b. As a result, a region of unevenness smaller than the unevenness due to the texture structure is formed. The region thus formed corresponds to the coating layer 41 in the buffer 4. Due to the unevenness region smaller than the unevenness due to the texture structure, the wettability to the connecting member 3 can be lowered because the unevenness is relatively small in the region. The light receiving surface side current collecting electrode 25a, the back surface side current collecting electrode 25b, and the exuded liquid resin are solidified by volatilizing the solvent by heating the work-in-process of the solar cell after application.

As the electrode raw material paste, a mixture of conductive particles and a liquid resin is used. The proportion of the electrode raw material paste is relatively large in conductive particles and small in liquid resin. As the conductive particles, for example, silver fine particles are used (but not limited to this, copper, aluminum, nickel, tin, bismuth, zinc, gallium, carbon and mixtures thereof can also be used). Further, as the liquid resin, for example, a polymer such as an epoxy resin is used (however, the present invention is not limited to this, and a phenolic resin, an acrylic resin, or the like can also be used). The electrode raw material paste of this embodiment is called "silver paste" and is generally distributed. When the electrode raw material paste configured in this way is applied to the planned formation position of each electrode, the liquid resin in the electrode raw material paste seeps out from the planned formation position, while the conductive particles do not greatly protrude from the planned formation position. , Aggregates and fixes at that position. As shown in FIG. 3, the exuded liquid resin spreads in the vicinity of the current collecting electrodes 25a and 25b so as to cover the unevenness due to the texture structure. By solidifying the spread resin, a coating layer 41, which is a solidified resin layer, is formed.

The ratio of the liquid resin to the electrode raw material paste is preferably 30% or less, particularly preferably 20% or less in terms of weight ratio. Further, 1% or more, particularly 3% or more is preferable. With such a weight ratio, when the electrode raw material paste is applied to the planned formation position, the liquid resin can be exuded from that position in a desired range.

As described above, in the method of the present embodiment, the electrode raw material paste used when forming the light receiving surface side current collecting electrode 25a and the back surface side current collecting electrode 25b is used to form each electrode and the unevenness smaller than the unevenness due to the texture structure. It is rational because it does not require a separate process because it can form a region of.

Although the present invention has been described by taking up one embodiment, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.

For example, the solar cell 2 may have at least irregularities on the light receiving surface 2a or the back surface 2b due to the texture structure. Further, the buffer portion 4 may be provided at least in the vicinity of the light receiving surface side current collecting electrode 25a on the light receiving surface 2a or in the vicinity of the back surface side current collecting electrode 25b on the back surface 2b.

Further, the buffer portion 4 can be formed by a method different from that of the above embodiment. For example, even if the buffer portion 4 is formed by polishing the light receiving surface 2a or the back surface 2b of the solar cell 2, laser processing, attaching a film, depositing fine particles, or separately applying a resin not derived from the electrode raw material paste. Good.

1 Solar cell string 2 Solar cell 2a Light receiving surface 2b Back surface 21 Semiconductor substrate 22a Intrinsic silicon layer (light receiving surface side)
22b Intrinsic silicon layer (back side)
23a Single conductive type silicon layer 23b Reverse conductive type silicon layer 24a Light receiving surface side transparent conductive layer 24b Back side transparent conductive layer 25a Light receiving surface side current collecting electrode 25a1 Light receiving surface side bus bar electrode 25b Back side current collecting electrode 25b1 Back side bus bar Electrode 26 Side surface 3 Connecting member 4 Buffer 41 Coating layer J cell connection direction

Claims (6)

A solar cell string comprising a plurality of solar cells and a conductive connecting member.
Each of the plurality of solar cell cells includes a light receiving surface side current collecting electrode provided on the light receiving surface and a back surface side current collecting electrode provided on the back surface.
When viewed in a plan view with respect to the light receiving surface, a part of the light receiving surface side current collecting electrode of one solar cell and another solar cell adjacent to the one solar cell among the plurality of solar cells. A part of the back side current collecting electrode of the solar cell is overlapped and connected via the connecting member.
The connecting member has fluidity at the time when it is arranged between the light receiving surface side current collecting electrode and the back surface side current collecting electrode.
At least in the vicinity of the light receiving surface side current collecting electrode on the light receiving surface or in the vicinity of the back surface side current collecting electrode on the back surface, the light receiving surface or the back surface is more wettable with respect to the connection member. A solar cell string with a low buffer formed. Each of the plurality of solar cells has irregularities due to a texture structure at least on the light receiving surface or the back surface.
The solar cell string according to claim 1, wherein the cushioning portion has a region of unevenness smaller than the unevenness due to the texture structure. The solar cell string according to claim 2, wherein the buffer portion includes a coating layer that covers unevenness due to the texture structure. A solar cell module including a plurality of solar cell cells and a conductive connecting member.
Each of the plurality of solar cell cells includes a light receiving surface side current collecting electrode provided on the light receiving surface and a back surface side current collecting electrode provided on the back surface.
When viewed in a plan view with respect to the light receiving surface, a part of the light receiving surface side current collecting electrode of one solar cell and another solar cell adjacent to the one solar cell among the plurality of solar cells. A part of the back side current collecting electrode of the solar cell is overlapped and connected via the connecting member.
The connecting member has fluidity at the time when it is arranged between the light receiving surface side current collecting electrode and the back surface side current collecting electrode.
At least in the vicinity of the light receiving surface side current collecting electrode on the light receiving surface or in the vicinity of the back surface side current collecting electrode on the back surface, the light receiving surface or the back surface is more wettable with respect to the connection member. A solar cell module in which a low shock absorber is formed. A method for manufacturing a solar cell in which at least the light receiving surface or the back surface has irregularities due to a texture structure, and the light receiving surface side current collecting electrode provided on the light receiving surface and the back surface side current collecting electrode provided on the back surface are provided. There,
When forming the light receiving surface side current collecting electrode and the back surface side current collecting electrode, a conductive electrode raw material paste which is a raw material of each of the electrodes is applied to a planned formation position.
After coating, at least a part of the liquid resin contained in the electrode raw material paste exudes and hardens in the vicinity of the coating position of the electrode raw material paste on the light receiving surface and the back surface, thereby resulting in the texture structure. A method for manufacturing a solar cell in which an uneven region smaller than an uneven region is formed. The method for producing a solar cell according to claim 5, wherein the electrode raw material paste is a mixture of conductive particles and the liquid resin.

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