JP7736710B2 - Solar cell and solar module - Google Patents

Description

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

The use of solar cells is becoming more widespread as an energy source with a low environmental impact. For example, Patent Document 1 proposes a solar cell module that can be attached to the roof of an automobile. Generally, a solar cell module is manufactured using multiple solar cell strings, each of which has multiple solar cell cells arranged and connected in a row. Since the installation area is limited in automobiles and the like, solar cell modules are required to have high photoelectric conversion efficiency in order to obtain sufficient power. Therefore, it is desirable to increase the effective area in which solar cell cells can contribute to photoelectric conversion by selecting the length of the solar cell string according to the size of the installation location.

The shape and size of the space in which a solar cell module can be installed on an automobile varies depending on the automobile model. Therefore, in order to improve the effective photovoltaic conversion efficiency of the solar cell module, the length of the solar cell string needs to be optimized for each automobile model. However, the length of the solar cell string cannot usually be changed except by adjusting the number of solar cells. While the photovoltaic conversion efficiency of the solar cell module can be maximized by changing the design of the solar cell for each automobile model, such design changes significantly increase the cost of the solar cell module.

JP 2017-188584 A

An object of the present invention is to provide a solar cell in which the length of the solar cell string is adjustable, and a solar cell module in which the length of the solar cell string is long.

A solar cell according to one aspect of the present invention comprises a semiconductor substrate, first and second semiconductor layers formed on a back surface of the semiconductor substrate and having mutually different conductivity types, a first electrode pattern laminated on the first semiconductor layer, and a second electrode pattern laminated on the second semiconductor layer, wherein the first semiconductor layer has a plurality of first main semiconductor portions extending in a first direction and arranged at intervals in a second direction intersecting the first direction, a first collection semiconductor portion arranged on one side of the plurality of first main semiconductor portions in the first direction and extending in the second direction, and a first terminal semiconductor portion connected to the other side of the first collection semiconductor portion in the first direction, and the second semiconductor layer extends in the first direction and has a first electrode pattern laminated on the first semiconductor layer and a second electrode pattern laminated on the second semiconductor layer. and a second semiconductor assembly arranged on the other side of the second semiconductor assembly in the first direction, the first electrode pattern having a plurality of first finger electrodes stacked on the first main semiconductor assembly to extend in the first direction, a first bus bar electrode stacked on the first semiconductor assembly, and a first pad electrode stacked on the first terminal semiconductor assembly and connected to the first bus bar electrode; and the second electrode pattern having a plurality of second finger electrodes stacked on the second main semiconductor assembly to extend in the first direction, and a second bus bar electrode stacked on the second semiconductor assembly.

In the solar cell, the first semiconductor layer may further have a first intermediate semiconductor portion extending in a second direction to connect an end portion of the first main semiconductor portion on one side of the first direction to the first terminal semiconductor portion, and the first electrode pattern may further have a first bypass electrode stacked on the first intermediate semiconductor portion and connecting the first finger electrode to the first pad electrode.

In the solar cell, the second semiconductor layer may further have a second terminal semiconductor portion connected to one side of the second semiconductor assembly in the first direction, and the second electrode pattern may further have a second pad electrode stacked on the second terminal semiconductor portion and connected to the second busbar electrode.

In the solar cell, the second semiconductor layer may further have a second intermediate semiconductor portion extending in a second direction to connect an end portion of the second main semiconductor portion on one side of the first direction to the second terminal semiconductor portion, and the second electrode pattern may further have a second bypass electrode stacked on the second intermediate semiconductor portion and connecting the second finger electrode to the second pad electrode.

A solar cell module according to one embodiment of the present invention comprises a plurality of solar cell strings, each having a plurality of solar cells and an interconnector connecting the solar cells, wherein in the solar cell strings, the end of one side of the solar cell in the first direction is arranged overlapping the front side of the end of an adjacent solar cell on the other side of the first direction, and the interconnector connects the first pad electrode of the solar cell overlapping on the front side to the second electrode pattern of the solar cell overlapping on the back side.

According to the present invention, it is possible to provide a solar cell in which the length of the solar cell string is adjustable, and a solar cell module in which the length of the solar cell string is long.

FIG. 2 is a rear view of a solar cell according to one embodiment of the present invention. 2 is a cross-sectional view of the solar cell of FIG. 1 taken along line AA. FIG. 2 is a rear view of a solar cell string having the solar cell of FIG. 1 . FIG. 4 is a cross-sectional view of a solar cell module including the solar cell string of FIG. 3.

Hereinafter, each embodiment of the present invention will be described with reference to the accompanying drawings. The same or equivalent parts in each drawing will be designated by the same reference numerals. For simplification, illustrations and reference numerals of components may be omitted. In such cases, other drawings should be referred to. The shapes and dimensions of various components in the drawings have been adjusted for clarity.

<Solar cell>
Fig. 1 is a back view showing a solar cell 1 according to one embodiment of the present invention. Fig. 2 is a cross-sectional view of the solar cell 1. The solar cell 1 includes a semiconductor substrate 10, a first semiconductor layer 20 and a second semiconductor layer 30 which are formed on the back surface of the semiconductor substrate 10 and have different conductivity types, a first electrode pattern 40 which is laminated on the first semiconductor layer 20, and a second electrode pattern 50 which is laminated on the second semiconductor layer 30. In Fig. 1, the first electrode pattern 40 and the second electrode pattern 50 are hatched for ease of understanding.

The semiconductor substrate 10 can be formed of a crystalline silicon material such as single crystal silicon or polycrystalline silicon. It may also be formed of other semiconductor materials such as gallium arsenide (GaAs). The semiconductor substrate 10 is, for example, an n-type semiconductor substrate formed by doping a crystalline silicon material with an n-type dopant. Examples of n-type dopants include phosphorus (P). The semiconductor substrate 10 functions as a photoelectric conversion substrate that absorbs incident light from the light-receiving surface side and generates photocarriers (electrons and holes). The use of crystalline silicon as the material for the semiconductor substrate 10 results in a relatively small dark current, enabling a relatively high output (stable output regardless of illuminance) to be obtained even when the intensity of incident light is low.

The first semiconductor layer 20 and the second semiconductor layer 30 are formed in approximately complementary shapes on the back surface of the semiconductor substrate 10 and have different conductivity types. The first semiconductor layer 20 and the second semiconductor layer 30 attract and collect carriers of opposite polarities from inside the semiconductor substrate 10.

Specifically, the first semiconductor layer 20 may be formed of a p-type semiconductor, and the second semiconductor layer 30 may be formed of an n-type semiconductor. The first semiconductor layer 20 and the second semiconductor layer 30 may 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 20 has first main semiconductor portions 21 extending in a first direction and arranged at intervals in a second direction intersecting the first direction, first collection semiconductor portions 22 arranged on one side of the first semiconductor portions in the first direction, connected to some of the first main semiconductor portions 21, and extending in the second direction, first terminal semiconductor portions 23 connected to the other side of the first collection semiconductor portions 22 in the first direction, a first intermediate semiconductor portion 24 extending in the second direction to connect the end portion on one side of the first direction of the first main semiconductor portion 21 that is not directly connected to the first collection semiconductor portion 22 and the first terminal semiconductor portion 23, and first extended semiconductor portions 25 extending in the second direction from the end portion on the other side of the first direction of some of the first main semiconductor portions 21.

The second semiconductor layer 30 has a plurality of second main semiconductor portions 31 extending in a first direction and arranged alternately with the first main semiconductor portions 21 in the second direction; second collection semiconductor portions 32 arranged on the other side of the plurality of second main semiconductor portions 31 in the first direction, connected to some of the second main semiconductor portions 31, and extending in the second direction; second terminal semiconductor portions 33 connected to one side of the second collection semiconductor portions 32 in the first direction; a second intermediate semiconductor portion 34 extending in the second direction alongside the first extended semiconductor portion 25 so as to connect the end portions on the other side of the first direction of the second main semiconductor portions 31 that are not directly connected to the second collection semiconductor portion 32 with the second terminal semiconductor portion 33; and second extended semiconductor portions 35 extending in the second direction alongside the first intermediate semiconductor portion 24 from the end portions on one side of the first direction of some of the second main semiconductor portions 31.

The first electrode pattern 40 is provided to extract charges from the first semiconductor layer 20, and the second electrode pattern 50 is provided to extract charges from the second semiconductor layer 30. The first electrode pattern 40 and the second electrode pattern 50 are stacked so as to leave margins at the outer edges of the first semiconductor layer 20 and the second semiconductor layer 30 to prevent short circuits.

The first electrode pattern 40 and the second electrode pattern 50 can be formed by, for example, etching a metal layer, printing and firing a conductive paste, etc. Furthermore, the first electrode pattern 40 and the second electrode pattern 50 may be a laminate of a transparent electrode layer made of, for example, ITO (Indium Tin Oxide), zinc oxide (ZnO), or the like, which is laminated on the first semiconductor layer 20 and the second semiconductor layer 30, and a metal electrode layer mainly made of metal.

Specifically, the first electrode pattern 40 has a plurality of first finger electrodes 41 each stacked on the first main semiconductor portion 21 to extend in the first direction, a first bus bar electrode 42 stacked on the first collection semiconductor portion 22 and connected to one end of some of the first finger electrodes 41 in the first direction, a first pad electrode 43 stacked on the first terminal semiconductor portion 23 and connected to the first bus bar electrode 42, a first bypass electrode 44 stacked on the first intermediate semiconductor portion 24 and connecting the first finger electrode 41 and the first pad electrode 43, and a first extension electrode 45 stacked on the first extension semiconductor portion 25 and connected to the first finger electrode 41.

The second electrode pattern 50 includes a plurality of second finger electrodes 51 stacked on the second main semiconductor portion 31 to extend in the first direction, second bus bar electrodes 52 stacked on the second collection semiconductor portion 32 and connected to the ends of some of the second finger electrodes 51 on the other side in the first direction, a second pad electrode 53 stacked on the second terminal semiconductor portion 33 and connected to the second bus bar electrode 52, a second bypass electrode 54 stacked on the second intermediate semiconductor portion 34 and connecting the second finger electrodes 51 and the second pad electrode 53, and a second extension electrode 55 stacked on the second extension semiconductor portion 35 and connected to the second finger electrodes 51.

The first main semiconductor portion 21 and the second main semiconductor portion 31 occupy a large area in the first semiconductor layer 20 and the second semiconductor layer 30. By forming the first main semiconductor portion 21 and the second main semiconductor portion 31 in a complementary stripe pattern, the travel distance of carriers within the semiconductor substrate 10 can be reduced, thereby improving the photoelectric conversion efficiency of the solar cell 1.

By providing a first semiconductor assembly 22 and a second semiconductor assembly 32 in which the first busbar electrode 42 and the second busbar electrode 52 are stacked, electric charges can be efficiently extracted from the first main semiconductor assembly 21 and the second main semiconductor assembly 31 with a relatively simple configuration.

By providing the first terminal semiconductor portion 23 and the first pad electrode 43, when the ends of each of multiple solar cell 1 in the first direction are arranged overlapping each other, even if the overlap width between the solar cell 1 is increased so that the first bus bar electrode 42 is covered by the end of an adjacent solar cell 1, power can be output from the first pad electrode 43.

Furthermore, by providing the first pad electrode 43 and the second pad electrode 53, the width in the first direction of the first bus bar electrode 42 and the second bus bar electrode 52 can be reduced, thereby enabling efficient extraction of charge from the semiconductor substrate 10. Therefore, by providing the first pad electrode 43 and the second pad electrode 53, the areas of the first main semiconductor portion 21 and the second main semiconductor portion 31 can be increased, and the photoelectric conversion efficiency of the solar cell 1 can be improved.

By providing the first intermediate semiconductor portion 24 and the second intermediate semiconductor portion 34, and thus the first bypass electrode 44 and the second bypass electrode 54, even if the width in the first direction of the first bus bar electrode 42 and the second bus bar electrode 52 is reduced, the electrical resistance from the first main semiconductor portion 21 and the second main semiconductor portion 31 to the first pad electrode 43 and the second pad electrode 53 that output power can be reduced, thereby suppressing internal losses in the solar cell 1.

The first extended semiconductor portion 25 and the second extended semiconductor portion 35, as well as the first extended electrode 45 and the second extended electrode 55, complement the reduction in area of the first main semiconductor portion 21 and the second main semiconductor portion 31 due to the formation of the first bypass electrode 44 and the second bypass electrode 54, and suppress a decrease in the efficiency of extracting charge from the semiconductor substrate 10.

<Solar cell string>
3 is a back view of a solar cell string 100 having a plurality of solar cells 1. The solar cell string 100 has a plurality of solar cells 1 lined up in a first direction and interconnectors 2 connecting adjacent solar cells. In the solar cell string 100, an end of one side of a solar cell 1 in the first direction is arranged to overlap with the front side of an end of an adjacent solar cell 1 on the other side in the first direction. The interconnectors 2 are formed from a conductor such as a metal wire, a metal foil, a metal braided wire, or a metal twisted wire, and connect a first pad electrode 43 of the solar cell 1 overlapped on the front side to a second bus bar electrode and a second pad electrode 53 of the solar cell 1 overlapped on the back side.

In the solar cell string 100, the overlap width in the first direction of the multiple solar cell 1 can be set arbitrarily within a range in which the area required for connecting the interconnector 2 to the first pad electrode 43 of the solar cell 1 on the front side is exposed. Therefore, the overall length of the solar cell string 100 in the first direction is adjustable.

Increasing the lengths of the first pad electrode 43 and the second pad electrode 53 in the first direction in order to increase the adjustable range of the overlap width may reduce the photoelectric conversion efficiency of the solar cell 1. For this reason, multiple types of solar cell 1 with different adjustable ranges of the overlap width in the first direction may be prepared, and the solar cell to be used may be selected depending on the desired length of the solar cell string 100.

<Solar cell module>
4 is a cross-sectional view of a solar cell module M including a solar cell string 100. The solar cell module M includes a plurality of solar cell strings 100 arranged side by side in the second direction, a plate-shaped surface protective material 200 covering the front sides of the plurality of solar cell strings 100, a plate-shaped or sheet-shaped back surface protective material 300 covering the back sides of the plurality of solar cell strings 100, and a sealing material 400 filled between the surface protective material 200 and the back surface protective material 300.

The surface protection material 200 protects the solar cell string 100 by covering the surface of the solar cell string 100 via the sealing material 400. The surface protection material 200 is preferably formed from a transparent, scratch-resistant material such as glass, polycarbonate, or acrylic resin, and has excellent weather resistance. Specifically, examples of the material for the surface protection material 200 include transparent resins such as acrylic resin or polycarbonate resin, and glass. Furthermore, the surface of the surface protection material 200 may be textured or coated with an anti-reflection coating layer to suppress light reflection.

The surface protection material 200 preferably has a sufficient thickness to provide the strength to maintain the shape of the solar cell module M. Furthermore, by using the surface protection material 200 that has been formed into a desired shape in advance, a solar cell module M having the desired shape can be obtained.

The surface protective material 200 may be larger than the multiple solar cell strings 100, the back surface protective material 300, and the sealing material 400 in a plan view. Such a surface protective material 200 functions as a flange for attaching the solar cell module M to a desired device. In other words, the solar cell module M can be attached to the device by adhering the back surface of the outer edge of the surface protective material 200 to the device using an adhesive. When the surface protective material 200 is the same size as the back surface protective material 300 and the sealing material 400 in a plan view, the back surface protective material 300 can be adhered to the device.

The surface protective material 200 may have a light-shielding region 201 on its outer periphery that blocks light. The light-shielding region 201 is usually formed with a fixed width along the outer edge of the surface protective material 200. The light-shielding region prevents sunlight from reaching the adhesive that secures the solar cell module M through the surface protective material 200 and deteriorating the adhesive when the solar cell module M is attached to the device. The light-shielding region 1 also improves the aesthetic appearance by concealing the attachment portion of the solar cell module M. The light-shielding region can be formed, for example, by applying black paint. Ceramic paint is generally used as the black paint.

The solar cell string 100 is formed to have a length substantially equal to the length in the first direction of the light-transmitting region inside the light-shielding region of the surface protection material 200. This increases the effective area for receiving light by the solar cell string 100, while preventing a decrease in photoelectric conversion efficiency due to light not being incident on some of the solar cells 1 at the ends of the solar cell string 100. Note that multiple solar cell strings 100 can be connected to each other by wiring material (not shown).

The back surface protective material 300 is a layer that protects the back surface of the solar cell string 100. The material of the back surface protective material 300 is not particularly limited, but a material that prevents the intrusion of water (high water resistance) is preferable. Specifically, the back surface protective material 300 can be formed from, for example, glass, polyethylene terephthalate (PET), acrylic resin, polyethylene (PE), olefin-based resin, fluorine-containing resin, silicone-containing resin, or other resin. The back surface protective material 300 may also be a laminate of a resin layer and a metal layer, for example, aluminum foil. Furthermore, the color (light reflection characteristics) of the back surface protective material 300 when viewed from the front surface is preferably similar to the color of the front surface of the solar cell 1 in order to make gaps between the solar cell strings 100 less noticeable and improve the aesthetic appearance of the solar cell module M.

The sealing material 400 seals the solar cell string 100 in the space between the front surface protective material 200 and the back surface protective material 300, and prevents deterioration of the solar cell string 100 due to moisture or the like. The sealing material 400 is formed from a material that is transparent and has adhesion to the front surface protective material 200 and the solar cell string 100. The material forming the sealing material 400 preferably has thermoplasticity so that the gap between the front surface protective material 200 and the solar cell string 100 can be sealed by heat pressing. Specifically, the material forming the sealing material 400 may be a resin composition mainly composed of, for example, ethylene/vinyl acetate copolymer (EVA), ethylene/α-olefin copolymer, ethylene/vinyl acetate/triallyl isocyanurate (EVAT), polyvinyl butyrate (PVB), acrylic resin, urethane resin, silicone resin, or the like.

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. For example, in a solar cell according to the present invention, the second terminal semiconductor portion and second pad electrode, the first intermediate semiconductor portion and first bypass electrode, the second intermediate semiconductor portion and second bypass electrode, the first extension semiconductor portion and first extension electrode, the second extension semiconductor portion and second extension electrode, etc. may be omitted. Furthermore, in a solar cell according to the present invention, the length in the second direction of the first pad electrode and the second pad electrode may be the same as the length in the second direction of the first bus bar electrode and the second bus bar electrode.

REFERENCE SIGNS LIST 1 Solar cell 2 Interconnector 10 Semiconductor substrate 20 First semiconductor layer 21 First main semiconductor portion 22 First semiconductor assembly 23 First terminal semiconductor portion 24 First intermediate semiconductor portion 25 First extended semiconductor portion 30 Second semiconductor layer 31 Second main semiconductor portion 32 Second semiconductor assembly 33 Second terminal semiconductor portion 34 Second intermediate semiconductor portion 35 Second extended semiconductor portion 40 First electrode pattern 41 First finger electrode 42 First bus bar electrode 43 First pad electrode 44 First bypass electrode 45 First extended electrode 50 Second electrode pattern 51 Second finger electrode 52 Second bus bar electrode 53 Second pad electrode 54 Second bypass electrode 55 Second extended electrode 100 Solar cell string 200 Surface protective material 300 Back surface protective material 400 Sealant M Solar cell module

Claims (3)

a semiconductor substrate; a first semiconductor layer and a second semiconductor layer formed on a rear surface of the semiconductor substrate and having mutually different conductivity types; a first electrode pattern stacked on the first semiconductor layer; and a second electrode pattern stacked on the second semiconductor layer;
the first semiconductor layer includes: a plurality of first main semiconductor portions extending in a first direction and spaced apart in a second direction intersecting the first direction; a first collection semiconductor portion arranged along a side edge of the semiconductor substrate on one side in the first direction, connected to one side in the first direction of two or more of the first main semiconductor portions, and extending in the second direction; a first terminal semiconductor portion connected to the other side in the first direction of the first collection semiconductor portion; and a first intermediate semiconductor portion arranged on the other side in the first direction of the first collection semiconductor portion, extending in the second direction to connect an end of a single first main semiconductor portion on one side in the first direction to the first terminal semiconductor portion;
the second semiconductor layer includes a plurality of second main semiconductor portions extending in the first direction and arranged alternately with the first main semiconductor portions in the second direction, and a second collection semiconductor portion arranged along a side edge of the semiconductor substrate on the other side in the first direction, connected to the other side in the first direction of two or more of the second main semiconductor portions, and extending in the second direction;
the first electrode pattern includes: a plurality of first finger electrodes stacked on the first main semiconductor portion to extend in the first direction; a first bus bar electrode stacked on the first semiconductor assembly portion and connected to two or more of the first finger electrodes; a first pad electrode stacked on the first terminal semiconductor portion and connected to the first bus bar electrode; and a first bypass electrode stacked on the first intermediate semiconductor portion and connecting a single first finger electrode and the first pad electrode ,
The second electrode pattern has a plurality of second finger electrodes stacked on the second main semiconductor portion so as to extend in the first direction, and a second bus bar electrode stacked on the second semiconductor assembly portion and connected to two or more of the second finger electrodes . 2. The solar cell of claim 1, wherein the second semiconductor layer further includes a second terminal semiconductor portion connected to one side of the second set of semiconductor portions in the first direction, and a second intermediate semiconductor portion arranged on one side of the second set of semiconductor portions in the first direction and extending in a second direction to connect an end of the single second main semiconductor portion on the other side of the first direction to the second terminal semiconductor portion, and the second electrode pattern further includes a second pad electrode stacked on the second terminal semiconductor portion and connected to the second bus bar electrode, and a second bypass electrode stacked on the second intermediate semiconductor portion and connecting the single second finger electrode to the second pad electrode. a plurality of solar cell strings each including a plurality of solar cell units according to claim 1 or 2 and an interconnector connecting the solar cell units;
In the solar cell string, an end portion of one solar cell in the first direction is arranged overlapping the front side of an end portion of an adjacent solar cell on the other side in the first direction, and the interconnector connects the first pad electrode of the solar cell overlapping the front side to the second electrode pattern of the solar cell overlapping the back side.