JP6325925B2 - Solar cell module and method for manufacturing solar cell module - Google Patents

Description

  The present invention relates to a solar cell module and a method for manufacturing a solar cell module.

In recent years, development of clean energy has been demanded due to the problem of depletion of energy resources and global environmental problems such as an increase in CO _{2 in} the atmosphere. Among semiconductor devices, solar power generation using solar cells is particularly important. It has been developed and put into practical use as a new energy source and is on the path of development.

  Conventionally, for example, a solar cell has a pn junction formed by diffusing an impurity having a conductivity type opposite to that of a silicon substrate into a light receiving surface of a single crystal or polycrystalline silicon substrate. Double-sided electrode type solar cells manufactured by forming electrodes on the back surface opposite to the light receiving surface are mainly used. In a double-sided electrode type solar cell, it is also common to increase the output by the back surface field effect by diffusing impurities of the same conductivity type as the silicon substrate at a high concentration on the back surface of the silicon substrate. .

  Moreover, as shown in Patent Document 1, a back electrode type solar cell in which an electrode is not formed on the light receiving surface of a silicon substrate and an electrode is formed only on the back surface of the silicon substrate is compatible with the back electrode type solar cell on the film. Solar cell modules installed on a wiring sheet (wiring board) on which wiring to be formed are commercialized.

  FIG. 8 shows a schematic cross-sectional view of a conventional back electrode type solar cell module. In this solar cell module 50, a plurality of p + layers 52 and n + layers 53 are alternately formed along the back surface on the back surface of a semiconductor substrate 51 such as a silicon substrate. A solar cell wafer 56 in which a dotted p electrode 54 is formed on the n + layer 52 and a p wiring 62 and an n wiring 63 are formed on the insulating substrate 61. Wiring board 65 that is provided. Then, the wiring substrate 65 is installed on the back surface of the solar cell wafer 56, the p wiring 62 is connected to the p electrode 54 through the solder 69, and the plurality of dotted p electrodes 54 are electrically connected. In addition, an n wiring 63 is connected to the n electrode 55 via a solder 69, and a plurality of dot-like n electrodes 55 are electrically connected.

JP 2005-340362 A

  The back electrode of the solar battery cell is a silver electrode having a thickness of several microns and has a relatively low resistance. The back electrode and the wiring sheet are bonded and electrically connected by a bonding material such as solder or conductive resin. At this time, the metal material contained in the bonding material is alloyed with the silver of the back electrode, and the contact resistance with the silicon substrate is increased, so that the power generation characteristics of the solar battery cell are reduced and the output of the solar battery module is reduced. There was a problem.

The solar cell module of the present invention includes a solar cell having a plurality of linear electrodes on the surface opposite to the light receiving surface, and a solar cell having a wiring sheet on which the solar cells are mounted and electrically connected to the electrodes. A module, wherein the wiring provided on the wiring sheet has a comb-tooth portion corresponding to the linear electrode, and the linear electrode and the comb-tooth portion include a plurality of dots along the linear electrode. are electrically connected by arranged bonding material, and the linear electrode and the comb portion in a portion where bonding material is not disposed is shall not contact directly.

Further, in the solar cell module of the present invention, the electrodes of the solar cell are a plurality of straight lines parallel to each other, and an insulating resin is disposed between the substrate back surface between adjacent electrodes and the wiring sheet facing the substrate back surface. It will be.

In the solar cell module of the present invention, the proportion of the bonding material covering the linear electrode is 6.6 to 40% .

  In the solar cell module of the present invention, the bonding material includes a solder material.

In the method for manufacturing a solar cell module of the present invention, a step of preparing a solar cell having a linear electrode on the surface opposite to the light receiving surface, and a plurality of bonding materials are arranged in a dotted manner along the linear electrode. The solar cell module is formed by placing the linear electrode of the solar battery cell on the comb-teeth portion corresponding to the linear electrode included in the wiring on the wiring sheet on the process, and the solar cell module is formed and the bonding material is The method includes a step of bringing the linear electrode and the comb tooth portion into direct contact with each other at a portion that is not arranged .

  By this invention, the increase in the contact resistance of a back surface electrode can be suppressed, and the output fall of a photovoltaic cell and a photovoltaic module can be made small.

It is a top view which shows the photovoltaic cell used for manufacture of the solar cell module of this invention. It is a top view which shows the wiring sheet used for the solar cell module of this invention. It is a top view which shows the state which has arrange | positioned joining material to the photovoltaic cell of this invention. It is a cross-sectional schematic diagram which shows the solar cell module of this invention. It is a top view which shows the positional relationship of the wiring sheet and joining material which are used for the solar cell module of a comparative example. It is a cross-sectional schematic diagram which shows the solar cell module of a comparative example. It is a graph which shows the output of a solar cell module. It is a cross-sectional schematic diagram which shows the solar cell module of a prior art example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

(Embodiment 1)
FIG. 1 is a plan view of a solar battery cell used for manufacturing the solar battery module of the present invention, and is a plan view seen from the back surface on the opposite side of the light receiving surface. A linear n-electrode 12 for collecting electrons and a linear p-electrode 13 for collecting holes are collected on the back surface opposite to the light receiving surface of the solar cell substrate 11 formed using a silicon single crystal semiconductor substrate as a base material. They are lined up alternately. The n electrode 12 and the p electrode 13 have a width of 130 μm and a thickness of about 3 μm. The distance between the n electrode 12 and the p electrode 13 is 0.75 mm. The n electrode 12 and the p electrode 13 which are back electrodes of the solar battery cell 10 are formed by printing a silver paste on the back surface of the solar battery substrate 11 and then baking it at 400 ° C. or higher. The solar cell substrate 11 has a substantially square shape with a side of about 150 mm.

  FIG. 2 is a plan view showing a wiring sheet used in the solar battery module of the present invention, and shows a wiring pattern of a portion on which one solar battery cell is placed. In the wiring sheet 20, comb-like copper wirings 22 and copper wirings 23 are formed on a sheet 21 formed of a film such as PET (polyethylene terephthalate) or PEN (polyethylene naphthalate). Since the thickness of the copper wirings 22 and 23 is 35 mm and the thickness is large, the resistance is lower than that of the n electrode 12 and the p electrode 13 on the solar battery cell.

  The copper wiring 22 electrically connected to the n-electrode 12 of the solar battery cell 10 includes a comb-tooth portion 22a that contacts the pattern of the linear n-electrode 12 and a base portion 22b that connects the comb-tooth portions. Is connected to the wiring pattern corresponding to the adjacent solar battery cell. Moreover, the copper wiring 23 electrically connected to the p-electrode 13 of the solar battery cell 10 includes a comb-tooth portion 23a that contacts the linear p-electrode 13 pattern, and a base portion 23b that connects the comb-tooth portions. The base 23b is connected to a wiring pattern corresponding to the adjacent solar battery cell.

  FIG. 3 is a plan view showing a state in which a bonding material is arranged in the solar battery cell of the present invention. On the back surface of the solar cell substrate 11, a solder resin bonding material 25 a is arranged in a dotted line along the shape of the linear electrode on the plurality of parallel n-electrodes 12. In addition, on the back surface of the solar cell substrate 11, a solder resin bonding material 25 b is arranged in a dotted line along the shape of the linear electrode on the plurality of parallel p-shaped electrodes 13. An insulating resin 24 is disposed between the n electrode 12 and the p electrode 13 on the back surface of the substrate. As the insulating resin 24, an epoxy resin can be used. The insulating resin 24 is installed between the n-electrode 12 and the p-electrode 13 so that the bonding material does not flow during bonding and short-circuits with the adjacent electrode. The insulating resin 24 and the bonding material 25 of the bonding material can be printed and arranged on the back surface of the solar battery cell using screen printing or the like.

When the solar battery cell 10 is placed on the wiring sheet 20, a plurality of bonding materials 25 a arranged in a dotted pattern on the n electrode 12 are comb-tooth portions 22 a at intervals of about 3 mm on the comb-tooth portions 22 a of the wiring sheet 20. It will be located along the longitudinal direction. Further, a plurality of bonding materials 25b arranged in a dot shape on the p-electrode 12 are positioned along the longitudinal direction of the comb teeth 22b at intervals of about 3 mm on the comb teeth 22b of the wiring sheet 20. . In this example, the bonding material and the bonding resin were printed on the solar battery cells and placed on the wiring sheet. However, after the bonding material and the bonding resin were printed on the wiring sheet, the solar battery cells were placed. May be.
After the insulating resin 24 and the bonding material 25 are disposed on the solar battery cell 10 or the wiring sheet 20, the solar battery cell 10 is placed on the wiring sheet 20, and is thermocompression bonded with a back sheet, a sealing resin, and a cover glass with a laminator. A solar cell module is formed.

  The bonding material 25 disposed on the copper wirings 22 and 23 is made of solder resin. Solder resin is a material in which particles of solder material such as tin or bismuth are dispersed in an insulating resin. The insulating resin is softened by heating and the particles of the solder material are aggregated. Has the property of curing. By performing heat treatment with a laminator at a relatively low temperature of 150 ° C. to 160 ° C., the bonding material 25a joins the n electrode 12 and the comb tooth portion 22a and electrically connects them. Further, the bonding material 25b bonds the p-electrode 13 and the comb tooth portion 23a and electrically connects them. In the part where the metal particles in the solder resin are melted, an alloy is formed with silver on the back electrode. When the back electrode is alloyed, the contact resistance between the silicon substrate and the back electrode increases. However, since the solder resin is arranged in a dot shape and the back electrode that does not contact the solder resin is not alloyed, the contact resistance between the silicon substrate and the back electrode is compared to the portion where the solder resin is in contact. Low. Therefore, the power generation efficiency is higher than that in which the solder resin is arranged in a line. Moreover, since the amount of solder resin used in the solar cell module can be reduced, the material can be effectively used.

(Embodiment 2)
FIG. 4 is a schematic cross-sectional view showing the solar cell module of the present invention. 4A is a schematic cross-sectional view in the longitudinal direction of the comb-tooth portion, and FIG. 4B is a schematic cross-sectional view in a direction substantially perpendicular to the comb-tooth portion. 4A, the solar cell module 1 is obtained by laminating an EVA sheet 32, a wiring sheet 20, a solar cell 10, an EVA sheet 33, and a cover glass 34 in this order on a back sheet 31, and thermocompression-bonding with a laminator. It is. Between the n electrode 12 and the copper wiring 22a, a plurality of bonding materials 25a are arranged in a dot shape, and the n electrode 12 and the copper wiring 22a are bonded and electrically connected via the bonding material 25a. doing. The insulating resin 24 may flow into the gap in the laminating process to fill the gap between the solar battery cell 10 and the wiring sheet 20, but it is not necessary to fill the gap in particular, and a space may remain.

  In the portion where the solder resin bonding material 25a and the n electrode 12 are in contact, tin contained in the solder resin and silver forming the n electrode 12 are alloyed, and the contact resistance is increased. However, the portion of the n-electrode 12 where the bonding material 25a is not disposed is not alloyed and remains low resistance. Therefore, the contact resistance of the entire solar battery cell is lower than that of bonding with a bonding material disposed on all of the n electrodes. In the above description, the connection to the n-electrode has been described, but the same applies to the connection between the p-electrode and the copper wiring.

  In FIG. 4B, the n-electrode 12 and the p-electrode 13 are joined and electrically connected via the joining materials 25a and 25b, which are conductive materials arranged in the form of dots on the copper wirings 22a and 22b. Yes. An insulating resin 24 made of an epoxy resin is disposed between the adjacent n electrode 12 and p electrode 13 to maintain insulation.

(Comparative example)
FIG. 5 is a schematic plan view showing the relationship between the wiring sheet and the bonding material in the solar cell module of the comparative example. In the wiring sheet 20 ′ in which comb-like copper wirings 22 ′ and 23 ′ are formed on the sheet 21 ′, the bonding material 25 ′ made of solder resin is made of copper so as to correspond to the n electrode and the p electrode of the solar battery cell. It is located on the wirings 22 ′ and 23 ′. That is, the bonding material 25a ′ is arranged linearly along the comb tooth portion 22a, and the bonding material 25b ′ is arranged linearly along the comb tooth portion 23a ′.

  FIG. 6 is a schematic cross-sectional view showing a solar cell module of a comparative example, in which a solar cell module 1 ′ is configured using a bonding material 25 ′ arranged linearly on a wiring sheet 20 ′. The solar cell module 1 ′ is obtained by sequentially stacking an EVA sheet 32 ′, a wiring sheet 20 ′, a solar cell 10 ′, an EVA sheet 33 ′, and a cover glass 34 ′ on the back sheet 31 ′, and performing thermocompression treatment with a laminator. It is. The linear bonding material 25a 'covers the entire n-electrode 12' and electrically connects the n-electrode 12 'and the comb-teeth portion 22a' of the copper wiring. Although not shown, the linear bonding material 25b ′ covers the entire p electrode 13 ′, and the p electrode 13 ′ and the comb tooth portion 23a ′ of the copper wiring are similarly formed in a linear shape. Are electrically connected. As described above, when the solder resin is used so as to cover the entire back surface electrode, the adhesion between the back surface electrode of each solar battery cell and the wiring sheet is improved, and the electrical contact area is increased. However, over the entire back electrode, an alloy of silver, which is a component of the back electrode, and a metal such as tin contained in the bonding material is formed, and the contact resistance between the back electrode and the silicon substrate increases, so that the solar cell The power generation efficiency of the solar cell module decreases.

  On the other hand, in the present invention, the bonding material is arranged in a dot shape, the amount of the bonding material is reduced, and the portion where the bonding material and the silver electrode are in contact is reduced. Therefore, the part where the contact resistance between the back electrode and the silicon substrate increases due to the alloying of the bonding material and the silver electrode is only the part where the solder resin is arranged, so compared with the solar cell where the bonding material is arranged in a straight line. Thus, the increase in contact resistance between the silicon substrate and the back electrode is small. Therefore, it is possible to reduce a decrease in power generation efficiency of the solar cell module due to the bonding material.

  Table 1 is a diagram showing the relationship between the filling rate of the solar cell bonding material and the output loss. The characteristics were measured by using one solar cell placed on a wiring sheet to form a small module. As in the comparative example, the filling rate is a solar cell module in which the bonding material is arranged in a straight line and the entire surface of the back electrode is covered as 100%. The ratio which covers a back electrode of a shape is shown. Therefore, the filling rate of 50% indicates a state in which 50% of the back electrode is covered with the dotted bonding material. The output indicates a relative value when the output of the comparative example is 100%. When the interval at which the dot-shaped bonding material is arranged becomes small, the number of connection points increases and the filling rate increases.

  According to Table 1, when the filling rate is about 1%, the output is 80% as compared with the comparative example, but when the filling rate exceeds 3%, the output loss sharply decreases and the output is 98% or more. Can be obtained. Further, when the filling rate is 6.6% to 40%, the output is larger than that of the comparative example, and the power generation efficiency is improved. Even if the filling rate exceeds 40%, the filling rate of the bonding material does not fall below the comparative example. This is because the contact state between the copper wiring of the wiring sheet and the n-electrode and p-electrode of the solar battery cell is good between the dots of the bonding material, and the solder resin is arranged over the entire n-electrode and p-electrode of the solar battery cell. It is thought that the contact resistance was lower than that. The number of connection points is the number of connection points per linear p-electrode and n-electrode.

  When the filling rate is lowered to reduce the amount of the bonding material and the number of portions to be bonded to the wiring sheet, the contact resistance between the silicon substrate and the n-electrode and the p-electrode as the back electrode decreases. On the other hand, since the back electrode is thin, the resistance is greater than that of the wiring sheet. Therefore, if the distance between the portions to be joined to the wiring sheet is increased, the distance that the charge moves on the back electrode increases, and the resistance loss increases. When the filling rate is about 1%, the influence of the resistance loss of the back electrode is large. However, if the filling rate exceeds 3%, the distance between the portions to be joined to the wiring sheet is shortened, the distance that the charge moves on the back electrode is reduced, and the resistance loss in the cell back electrode is reduced. The conductive output is improved. Moreover, since the amount of the bonding material used is the same as the filling rate, it is reduced to 3% compared to the conventional case.

  Further, it was confirmed that at least when the filling rate of the bonding material is 6.6% or more, an output higher than that of the comparative example can be obtained while reducing the amount of the bonding material used. The interval between the connection points when the filling rate is 6.6% is 4.5 mm. Furthermore, as the filling rate increases, the interval between connection points decreases.

  FIG. 7 is a diagram showing the output of the solar cell module. In the comparative example, the bonding material is arranged linearly (hereinafter referred to as “Line type”), and the bonding material is dotted as in the first and second embodiments. Is a diagram showing the module output of what is arranged in (hereinafter referred to as “Dot type”), where the average output of the Line type is 100 and the output is shown as a relative value. The first group shows the distribution of the outputs of 18 line type output modules. The second group shows the output distribution of 10 Dot type modules, and the third group shows the output distribution of 12 Line type output modules. The filling rate of the bonding material of the Dot type output module is 20%. As a result, it has been found that the output of the Dot type is about 0.7% higher than that of the Line type on average. Table 2 shows a comparison of the characteristics of the Dot type and Line type solar cell modules.

  In Table 2, the average values of the characteristics of the Line type and Dot type solar cell modules are shown. The value is a relative value when the average value of each characteristic of the Line type is 100%. The Pt (maximum output), Isc (short-circuit current), Voc (open-circuit voltage), and FF (curve factor) of the solar cell are compared. The Dot type is Pm (maximum output), Isc (short-circuit current), FF (curve). The factor) value is improved, and it can be seen that the power generation characteristics are improved.

(Embodiment 3)
A silver paste can also be used as a bonding material. This silver paste is not a silver paste that is baked at a high temperature to create a back electrode of a solar battery cell, but a back electrode and a copper wiring are joined by heating at a relatively low temperature of about 150 ° C. to 160 ° C. by a laminator. And is made of a mixture of metal mainly composed of resin and silver particles.

  When silver paste is used as such a bonding material, an increase in contact resistance due to alloying does not occur. However, the amount of bonding material used can be reduced by arranging them in a dotted line. When the silver paste is arranged in a dot shape, as in the case of the solder resin, if the filling rate is 3% or more, the power generation efficiency is the same as that in which the silver paste is arranged in a line along the back electrode.

  Furthermore, since the usage-amount of the joining material used for the electrical connection of the back electrode of an n electrode photovoltaic cell and the copper wiring of a wiring sheet can be reduced, it contributes to the effective utilization of material.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 ... Solar cell module 10 ... Solar cell 12 ... n electrode 13 ... p electrode 20 ... wiring sheet 21 ... sheet 22 ... copper wiring 22a ... comb tooth part 22b ... base part 23 ... copper wiring 23a ... comb tooth part 23b ... base part 24 ... Insulating resin 25 ... Bonding material 25a ... Bonding material 25b ... Bonding material 31 ... Back sheet 32 ... EVA sheet 33 ... EVA sheet 34 ... Cover glass

Claims (5)

A solar battery module having a solar battery cell having a plurality of linear electrodes on the surface opposite to the light receiving surface, and a wiring sheet for placing the solar battery cell and electrically connecting to the electrode,
The wiring provided on the wiring sheet has comb teeth corresponding to the linear electrodes,
The linear electrode and the comb-tooth portion are electrically connected by a bonding material arranged in a dotted manner along the linear electrode, and the linear electrode is a portion where the bonding material is not arranged. solar cell module and the electrode and the comb-tooth portions that are in direct contact. The solar cell according to claim 1, wherein the electrodes of the solar battery cells have a plurality of straight lines parallel to each other, and an insulating resin is disposed between a substrate back surface between adjacent electrodes and the wiring sheet facing the substrate back surface. Battery module. The solar cell module according to claim 1 or 2, wherein a ratio of the bonding material covering the linear electrode is 6.6 to 40% .   The solar cell module according to claim 1, wherein the bonding material includes a solder material. Preparing a solar cell having a linear electrode on the surface opposite to the light receiving surface;
A step of arranging a plurality of bonding material in dots along said line-shaped electrodes,
The solar cell module is formed by placing the linear electrode of the solar battery cell on a comb tooth portion corresponding to the linear electrode included in the wiring on the wiring sheet, and thermocompression-bonding, and the bonding material The manufacturing method of the solar cell module including the process of making the said linear electrode and the said comb-tooth part contact directly in the part in which is not arrange | positioned .

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