JP7530221B2 - Solar cell strings and solar cell modules - Google Patents

Description

The present invention relates to a solar cell string and a solar cell module.

Solar cell modules having multiple solar cells are often formed using solar cell strings in which multiple solar cells are arranged in a row and adjacent solar cells are connected by interconnectors. The solar cells are configured to extract power via electrode patterns formed on their surfaces.

In a back-electrode solar cell in which a pair of electrode patterns with opposite polarities are provided on the back surface, it is necessary to lay each of the pair of electrode patterns over the entire surface of the cell in order to collect current from the entire cell, and to arrange the pair of electrode patterns so that they do not come into contact with each other in order to prevent short circuits. To meet these conditions, an electrode pattern is provided that has numerous thin linear electrodes (finger electrodes) with different polarities that are arranged alternately, and a slightly wider electrode (busbar electrode) that connects these linear electrodes for current collection.

To improve the efficiency of the solar cell string, it is desirable to reduce the electrical resistance of the electrode pattern as seen from the interconnector, that is, the electrical resistance between the electrode pad (which may be part of the busbar electrode) connected to the interconnector and the end portion. Therefore, it is desirable for the electrode pad to have a pad portion in an area away from the adjacent solar cell in order to reduce the distance between the pad portion and the end portion.

Busbar electrodes are usually made of metal and have a different thermal expansion coefficient from the main body of the solar cell, which is made of a silicon substrate or the like. For this reason, there is a risk that thermal stress will act between the busbar electrodes and the main body of the solar cell due to temperature changes. Patent Document 1 proposes making the width of the center of the busbar smaller than the width of the ends in order to mitigate warping of the solar cell due to thermal stress between the substrate and the busbar electrodes.

JP2013-045951A

In the solar cell described in Patent Document 1, a bus bar is arranged to run across the solar cell, and a connection member (interconnector) is connected along the entire length of the bus bar. Generally, the interconnector is also made of metal, so there is a risk that the interconnector will separate due to thermal stress caused by the difference in thermal expansion coefficient between the bus bar and the solar cell. Therefore, the object of the present invention is to provide a solar cell string and a solar cell module with highly reliable interconnect connection.

A solar cell string according to one aspect of the present invention comprises a plurality of solar cells arranged in a row in a first direction and an interconnector connecting two adjacent solar cells, the solar cells having a first electrode pattern and a second electrode pattern with different polarities on their rear surfaces, the first electrode pattern having a plurality of first fixing pad portions to which the interconnector is fixed and a plurality of contact pad portions with which the interconnector is in slidable contact, and the second electrode pattern having a plurality of second fixing pad portions to which the interconnector is fixed.

In the solar cell string, the contact pad portion may be disposed at one end of the solar cell in the first direction.

In the solar cell string, the interconnector may have a contact wiring portion extending in a second direction intersecting the first direction so as to contact the plurality of contact pad portions, a plurality of first fixed wiring portions extending from the contact wiring portion to one side in the first direction and each fixed to the first fixed pad portion, and a plurality of second fixed wiring portions extending from the contact wiring portion to the other side in the first direction and each fixed to the second fixed pad portion.

In the solar cell string, the solar cells may be arranged so that their ends in the first direction overlap each other, and the contact pad portion may be disposed on the end of the solar cell that is disposed on the rear side of the adjacent solar cell.

The solar cell string may further include a plurality of insulating sheets that are laminated on the rear side of each of the solar cells and interposed between the solar cells and the interconnector, and the insulating sheets may have a plurality of first fixing openings that respectively expose the first fixing pad portions, a plurality of contact openings that respectively expose the contact pad portions, and a plurality of second fixing openings that respectively expose the second fixing pad portions.

In the solar cell string, the contact opening may be larger than the first fixing opening and the second fixing opening.

A solar cell module according to one aspect of the present invention includes the solar cell string.

The present invention provides a solar cell string and a solar cell module with highly reliable interconnect connections.

FIG. 2 is a schematic rear view of a solar cell string according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of the solar cell string of FIG. 1 . 2 is a schematic rear view of a solar cell of the solar cell string of FIG. 1 . FIG. 2 is a schematic rear view of the interconnector of the solar cell string of FIG. 1 . FIG. 2 is a schematic rear view of an insulating sheet of the solar cell string of FIG. 1 . 2 is a schematic cross-sectional view of a solar cell module including the solar cell string of FIG. 1.

Embodiments of the present invention will be described below with reference to the attached drawings. Note that the same reference numerals will be used to refer to the same or equivalent parts in each drawing. For simplification, illustrations and reference numerals of components may be omitted, in which case other drawings should be referenced. For convenience, the shapes and dimensions of various components in the drawings have been adjusted for ease of viewing.

<Solar cell string>
Fig. 1 is a schematic rear view showing a solar cell string 1 according to an embodiment of the present invention. Fig. 2 is a schematic cross-sectional view of the solar cell string 1.

The solar cell string 1 according to one embodiment of the present invention comprises a plurality of solar cells 10 arranged in a row in a first direction, an interconnector 20 that connects two adjacent solar cells 10, and a plurality of insulating sheets 30 that are laminated on the back side (opposite the light receiving surface) of each solar cell 10 and interposed between the solar cell 10 and the interconnector 20. The solar cell string 10 is arranged so that the ends in the first direction are overlapped with each other in a fixed direction. In other words, the solar cell string 1 has a so-called shingling structure.

The solar cell 10 is a so-called heterojunction back-contact type solar cell. As shown in detail in FIG. 3, the solar cell 10 has a semiconductor substrate 11, a first semiconductor layer 12 and a second semiconductor layer 13 formed on the back surface of the semiconductor substrate 11 so as not to substantially overlap, a first electrode pattern 14 laminated on the back surface of the first semiconductor layer 12, and a second electrode pattern 15 laminated on the back surface of the second semiconductor layer 13.

The semiconductor substrate 11 functions as a photoelectric conversion substrate that absorbs incident light from the light receiving surface side and generates photocarriers (electrons and holes). The semiconductor substrate 11 is formed of a crystalline silicon material such as single crystal silicon or polycrystalline silicon. The semiconductor substrate 11 is, for example, an n-type semiconductor substrate in which a crystalline silicon material is doped with an n-type dopant. An example of an n-type dopant is phosphorus (P). By using crystalline silicon as the material for the semiconductor substrate 11, the dark current is relatively small, and a relatively high output (stable output regardless of illuminance) can be obtained even when the intensity of the incident light is low.

The first semiconductor layer 12 and the second semiconductor layer 13 attract carriers generated in the semiconductor substrate 11 and collect electric charges. It is preferable that the first semiconductor layer 12 and the second semiconductor layer 13 are arranged so that together they cover substantially the entire surface of the semiconductor substrate 11.

The first semiconductor layer 12 and the second semiconductor layer 13 have different conductivity types. For example, the first semiconductor layer 12 is formed of a p-type semiconductor, and the second semiconductor layer 13 is formed of an n-type semiconductor. The first semiconductor layer 12 and the second semiconductor layer 13 can be formed of, for example, an amorphous silicon material containing a dopant that imparts the desired conductivity type. An example of a p-type dopant is boron (B), and an example of an n-type dopant is phosphorus (P) as described above.

The first semiconductor layer 12 has a plurality of first end semiconductor parts 121 each formed in a strip shape extending in a second direction intersecting the first direction and arranged in a matrix in the first and second directions, a plurality of first intermediate semiconductor parts 122 extending in the first direction so as to connect each of the plurality of first end semiconductor parts 121 arranged in the first direction, and a base end semiconductor part 123 formed along one side edge of the semiconductor substrate 11 in the first direction and connecting the plurality of first intermediate semiconductor parts 122.

The second semiconductor layer 13 has a plurality of second end semiconductor parts 131 arranged in a matrix shape that is alternately positioned with the first end semiconductor parts 121 in the first direction, each of which is formed in a strip shape extending in a second direction intersecting the first direction, and a plurality of second intermediate semiconductor parts 132 extending in the first direction so as to connect each of the plurality of second end semiconductor parts 131 arranged in the first direction. The plurality of second intermediate semiconductor parts 132 are not connected to each other.

The first electrode pattern 14 and the second electrode pattern 15 extract electric charge from the first semiconductor layer 12 and the second semiconductor layer 13, respectively, and output power from the solar cell 10 to the outside via the interconnector 20 described below. In other words, the solar cell 10 has a first electrode pattern 14 and a second electrode pattern 15, which have different polarities from each other, on the back surface. The first electrode pattern 14 and the second electrode pattern 15 are stacked so as to leave a margin on the outer edge of the first semiconductor layer 12 and the second semiconductor layer 13, respectively, at least in the area that is not disposed on the back side of other solar cells 10, in order to insulate them from each other.

The first electrode pattern 14 and the second electrode pattern 15 can be formed by patterning a metal layer of, for example, copper, nickel, or the like, by etching. The first electrode pattern 14 and the second electrode pattern 15 can also be formed by printing and firing a conductive material such as silver paste, or by plating using a thin conductive layer laminated in a desired pattern as the adherend.

The first electrode pattern 14 has a plurality of first terminal current collectors 141 each stacked on the first terminal semiconductor portion 121, a plurality of first intermediate current collectors 142 each stacked on the first intermediate semiconductor portion 122, and a base end current collector 143 stacked on the base end semiconductor portion 123. The first intermediate current collector 142 is provided with a first fixing pad portion 144 to which the interconnector 20 is fixed, and the base end current collector 143 is provided with a contact pad portion 145 with which the interconnector 20 is in slidable contact. That is, the first electrode pattern 14 has a plurality of contact pad portions 145 arranged at an end portion on one side of the first direction of the solar cell 10, more specifically, at an end portion on the side arranged on the back side of the adjacent solar cell 10, and a plurality of first fixing pad portions 144 arranged on the other side of the first direction from the contact pad portion 145. The first fixed pad portion 144 and the contact pad portion 145 may be formed to protrude from the first intermediate current collector portion 142 and the base end current collector portion 143, or may be a partial area of the first intermediate current collector portion 142 and the base end current collector portion 143.

The second electrode pattern 15 has a plurality of second terminal current collectors 151 that are respectively stacked on the second terminal semiconductor portion 131, and a plurality of second intermediate current collectors 152 that are respectively stacked on the second intermediate semiconductor portion 132. The second intermediate current collectors 152 are provided with second fixing pad portions 153 to which the interconnector 20 is fixed. In other words, the second electrode pattern 15 has a plurality of second fixing pad portions 153 that are arranged on the other side of the contact pad portion 145 of the first electrode pattern 14 in the first direction. The second fixing pad portions 153 may be formed to protrude from the second intermediate current collectors 152, or may be a partial area of the second intermediate current collectors 152.

The interconnector 20 connects the first electrode pattern 14 of the solar cell 10 to the second electrode pattern 15 of the adjacent solar cell 10. The interconnector 20 may be formed from a metal foil such as copper.

As shown in detail in FIG. 4, the interconnector 20 has a contact wiring portion 21 extending in the second direction to contact a plurality of contact pad portions 145, a plurality of first fixed wiring portions 22 extending from the contact wiring portion 21 to one side in the first direction and each fixed to a first fixed pad portion 144, and a plurality of second fixed wiring portions 23 extending from the contact wiring portion 21 to the other side in the first direction and alternately with the first fixed wiring portions 22 in the second direction and each fixed to a second fixed pad portion 153.

The contact wiring portion 21 is overlapped on the back side of the contact pad portions 145 and is in slidable contact with them. The first fixed wiring portion 22 is fixedly connected to the overlapping first fixed pad portions 144 by a connection material 40 such as solder or a conductive adhesive. The second fixed wiring portion 23 is fixedly connected to the overlapping second fixed pad portions 153 by a connection material 40. The widths of the first fixed wiring portion 22 and the second fixed wiring portion 23 in the second direction may be larger on the contact wiring portion 21 side as shown in the figure, to the extent that they do not overlap each other. This improves the rigidity of the first fixed wiring portion 22 and the second fixed wiring portion 23, making it easier to handle the interconnector 20 when manufacturing the solar cell string 1.

The insulating sheet 30 is interposed between the solar cell 10 and the interconnector 20, and prevents the interconnector 20 from contacting any part of the first electrode pattern 14 other than the first fixed pad portion 144 and the contact pad portion 145, and any part of the second electrode pattern 15 other than the second fixed pad portion 153, causing a short circuit.

As shown in detail in FIG. 5, the insulating sheet 30 has a plurality of first fixing openings 31 that expose the first fixing pad portions 144, a plurality of contact openings 32 that expose the contact pad portions 145, and a plurality of second fixing openings 33 that expose the second fixing pad portions. The insulating sheet 30 further has a sealant opening 34 that opens an area that does not overlap with the interconnector 20.

In FIG. 2, the thickness of each component is shown large for ease of understanding, so that the interconnector 20 appears to be in contact with the contact pad portion 145 by bulging extremely toward the solar cell 10. However, in reality, the thickness of the insulating sheet 30 is sufficiently small that the interconnector 20 easily contacts the contact pad portion 145 when the solar cell module is formed as described below, simply by being pressed by the sealing material 4. In addition, to further facilitate deformation of the interconnector 20, it is preferable that the contact opening 32 is larger than the first fixing opening 31 and the second fixing opening 33.

<Solar cell module>
Fig. 6 is a schematic cross-sectional view of a solar cell module M according to one embodiment of the present invention. The solar cell module M in Fig. 6 includes a plurality of solar cell strings 1, a front surface protective material 2 covering the front surface sides of the plurality of solar cell strings 1, a back surface protective material 3 covering the back surface sides of the solar cell strings 1, and a sealing material 4 filled in a space around the solar cell strings 1 between the front surface protective material 2 and the back surface protective material 3.

In the solar cell module M, multiple solar cell strings 1 are arranged in parallel in the second direction.

The surface protective material 2 protects the solar cell string 1, i.e., the surface of the solar cell 10, by covering it via the sealing material 4. The surface protective material 2 can be formed from a plate-like or sheet-like material, and preferably has excellent light transmittance and weather resistance. Specifically, examples of the material for the surface protective material 2 include transparent resins such as acrylic resins or polycarbonate resins, and glass. In addition, the surface of the surface protective material 2 may be processed to have an uneven shape or coated with an anti-reflective coating layer in order to suppress light reflection.

The back surface protective material 3 protects the solar cell 10 by covering the back surface of the solar cell string 1 via the sealing material 4. Like the front surface protective material 2, the back surface protective material 3 can be formed from a plate-like or sheet-like material, and preferably has excellent water impermeability. Specifically, the back surface protective material 3 is preferably made of a resin film such as polyethylene terephthalate (PET), polyethylene (PE), olefin resin, fluorine-containing resin, silicone resin, or a laminate of such a resin film and a metal foil such as aluminum foil.

The sealing material 4 seals and protects the solar cell string 1, i.e., the solar cell 10, and in particular prevents moisture from coming into contact with the solar cell 10. The sealing material 4 adheres closely to the solar cell 10 at the sealing material opening 34 of the insulating sheet 30, reinforcing the connection strength between the solar cell 10 by the interconnector 20.

The sealing material 4 bonds the solar cell string 1 to the front surface protective material 2 and the back surface protective material 3, and also protects the solar cell 10 by eliminating gaps around the solar cell string 1. For this reason, the sealing material 4 is preferably a thermoplastic resin having translucency, such as ethylene/vinyl acetate copolymer (EVA), ethylene/α-olefin copolymer, ethylene/vinyl acetate/triallyl isocyanurate (EVAT), polyvinyl butyrate (PVB), acrylic resin, urethane resin, or silicone resin.

The solar cell module M can be manufactured by stacking the surface protective material 2, a first sheet made of thermoplastic resin that forms the front side of the sealing material 4, the solar cell string 1, a second sheet made of thermoplastic resin that forms the back side of the sealing material 4, and the back protective material 3 in that order, and then heat pressing the stack to melt and integrate the first sheet and the second sheet to form the sealing material 4.

In the solar cell string 1, the interconnector 20 is in sliding contact with the contact pad portion 145 of the solar cell 10, so that the electrical connection between the solar cell 10 and the interconnector 20 can be maintained while absorbing the difference between the amount of thermal expansion of the solar cell 10, which is dominated by the thermal expansion of the semiconductor substrate 11, and the amount of thermal expansion of the interconnector 20. Therefore, the solar cell string 1 and the solar cell module M using the solar cell string 1 have a highly reliable connection of the interconnector 20.

In the solar cell string 1, the contact pad portion 145 is disposed on one side of the solar cell 10 in the first direction, so that the length of the portion of the interconnector 20 fixed to one solar cell 10 is sufficiently smaller than the length of the solar cell 10 in the first direction. This makes it possible to efficiently alleviate thermal stress caused by the difference in thermal expansion coefficient between the solar cell 10 and the interconnector 20, so that the interconnector 20 is less likely to peel off from the solar cell 10.

In the solar cell string 1, the interconnector 20 is formed in a tree shape with the first fixed wiring portion 22 and the second fixed wiring portion 23 branching out from the contact wiring portion 21, so that the contact wiring portion 21 has a certain area around the portion that contacts the contact pad portion 145. This prevents the sealant 4 from accidentally entering between the contact pad portion 145 and the contact wiring portion 21 when forming the solar cell module M, thereby further improving the reliability of the connection of the interconnector 20.

In addition, in the interconnector 20, the first fixed wiring part 22 and the second fixed wiring part 23 extend from the contact wiring part 21 in opposite directions in the first direction and alternately in the second direction, so that the thermal displacement of each solar cell 10 can be absorbed by the contact wiring part 21, and the relative positions of the solar cells 10 can be maintained to prevent the solar cells 10 from moving within the solar cell module M.

The contact pad portion 145 is disposed at the end of the solar cell 10 that is disposed on the back side of the adjacent solar cell 10, that is, in the portion where the thickness of the solar cell string 1 is relatively large, so that the pressure contact force of the interconnector 20 against the contact pad portion 145 is large, and the contact between the contact pad portion 145 and the interconnector 20 is reliable. In addition, by providing the contact pad portion 145 in a portion that does not contribute to photoelectric conversion by being disposed on the back side of other solar cell 10, the contact pad portion 145 of the first electrode pattern 14, and therefore the base end current collecting portion 143 and the contact wiring portion 21 of the interconnector 20, can be enlarged without reducing the photoelectric conversion efficiency, and the contact between the contact pad portion 145 and the interconnector 20 can be reliable.

The solar cell string 1 has an insulating sheet 30 interposed between the solar cell 10 and the interconnector 20, so that, while having a relatively simple configuration, it can reliably prevent short circuits caused by the interconnector 20 coming into contact with unintended parts of the first electrode pattern 14 and the second electrode pattern 15.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications and variations are possible.

The solar cell string according to the present invention may omit the insulating sheet by providing the solar cell with a structure such as a solder resist that prevents the interconnector from contacting unintended portions of the first electrode pattern and the second electrode pattern.

In the solar cell string described above, the number and arrangement of the first fixed pad portion, the contact pad portion, and the second fixed pad portion can be changed as desired. For example, the first fixed pad portion and the second fixed pad portion may be arranged side by side in the first direction. Also, the first fixed pad portion may be provided near a side edge on one side of the semiconductor substrate in the first direction, and the contact pad portion may be provided on the other side of the first fixed pad portion in the first direction.

In the solar cell string according to the present invention, the shapes of the first semiconductor layer, the second semiconductor layer, the first electrode pattern, and the second electrode pattern are not limited to those in the above-described embodiment. For example, the second electrode pattern may also have a second base end current collecting portion that connects multiple second intermediate current collecting portions, similar to the first electrode pattern.

In the solar cell string according to the present invention, the thickness of the first electrode pattern and the second electrode pattern may be locally increased in at least some areas of the first fixed pad portion, the contact pad portion, and the second fixed pad portion to facilitate connection of the interconnector.

In addition, in the solar cell string according to the present invention, two adjacent solar cells may be connected by multiple interconnectors.

LIST OF SYMBOLS 1 Solar cell string 2 Surface protective material 3 Back surface protective material 4 Sealing material 10 Solar cell 11 Semiconductor substrate 12 First semiconductor layer 121 First terminal semiconductor portion 122 First intermediate semiconductor portion 123 Base semiconductor portion 13 Second semiconductor layer 131 Second terminal semiconductor portion 132 Second intermediate semiconductor portion 14 First electrode pattern 141 First terminal current collector 142 First intermediate current collector 143 Base terminal current collector 144 First fixed pad portion 145 Contact pad portion 15 Second electrode pattern 151 Second terminal current collector 152 Second intermediate current collector 153 Second fixed pad portion 20 Interconnector 21 Contact wiring portion 22 First fixed wiring portion 23 Second fixed wiring portion 30 Insulating sheet 31 First fixed opening 32 Contact opening 33 Second fixed opening 34 Sealing material opening 40 Connection material M Solar cell module

Claims (7)

A plurality of solar cells arranged in a row in a first direction;
A plurality of interconnectors that connect two adjacent solar cells;
Equipped with
The solar cell has a first electrode pattern and a second electrode pattern having different polarities on a back surface,
the first electrode pattern has a plurality of first fixing pad portions to which the interconnectors connected to the solar cell adjacent on one side in the first direction are fixed, and a plurality of contact pad portions with which the interconnectors connected to the solar cell adjacent on the one side in the first direction are in slidable contact,
The second electrode pattern has a plurality of second fixing pad portions to which the interconnectors that connect to the solar cell adjacent to the solar cell on the other side in the first direction are fixed. The solar cell string according to claim 1, wherein the contact pad portion is disposed at one end of the solar cell in the first direction. The interconnector comprises:
a contact wiring portion extending in a second direction intersecting the first direction so as to contact the plurality of contact pad portions of the solar cell on the other side in the first direction out of the two adjacent solar cells ;
a plurality of first fixed wiring portions extending from the contact wiring portion to the other side in the first direction and fixed to the first fixed pad portions of the solar cell on the other side in the first direction ;
a plurality of second fixed wiring portions extending from the contact wiring portion to one side in the first direction and fixed to the second fixed pad portions of the solar cells on the one side in the first direction ;
The solar cell string of claim 2 , The solar cells are arranged such that ends in the first direction overlap each other,
The solar cell string according to claim 2 , wherein the contact pad portion is disposed at an end of the solar cell on a side disposed on a rear side of the adjacent solar cell. The solar cell further includes a plurality of insulating sheets that are laminated on the rear surface side of the solar cell and interposed between the solar cell and the interconnector,
5. The solar cell string of claim 1, wherein the insulating sheet has a plurality of first fixing openings that each expose the first fixing pad portion, a plurality of contact openings that each expose the contact pad portion, and a plurality of second fixing openings that each expose the second fixing pad portion. The solar cell string of claim 5, wherein the contact opening is larger than the first fixing opening and the second fixing opening. A solar cell module comprising a solar cell string according to any one of claims 1 to 6.

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