JP2020057694A - Solar cell - Google Patents

Abstract

To provide a solar cell capable of improving the connectibility between a bus bar electrode and a wiring member, and reducing the used amount of conductive paste while maintaining high output characteristics.SOLUTION: A solar cell 10 includes: a silicon substrate 20; a semiconductor layer 80n formed over the silicon substrate 20; and multiple collector electrodes formed on the semiconductor layer 80n. The multiple collector electrodes have multiple finger electrodes 41, and a bus bar electrode 42 that is formed being connected to the multiple finger electrodes 41. The bus bar electrode 42 has an irregular portion 44 in which multiple recesses 45 and convexes 46 thicker than the recess 45 are forme alternatively in a first direction. The width w2 of the convexes 46 is larger than the width w1 of the recess 45 in a cross-section perpendicular to the silicon substrate 20 including the first direction.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a solar cell.

  2. Description of the Related Art Conventionally, solar cells have been developed as photoelectric conversion devices that convert light energy into electric energy. BACKGROUND ART Solar cells are expected as a new energy source because they can directly convert inexhaustible sunlight into electricity, and have a smaller environmental load and are cleaner than power generation using fossil fuels.

  The solar battery cell includes a current collecting electrode on a semiconductor substrate for collecting light received by the semiconductor substrate. The current collecting electrode includes a bus bar electrode to which a wiring member for electrically connecting the solar cells is connected. Patent Literature 1 discloses a solar cell in which a slit is formed in a bus bar electrode to improve the adhesive strength between the bus bar electrode and the semiconductor substrate.

JP 2007-150356 A

  The bus bar electrode of the solar cell described in Patent Literature 1 is provided with a slit, so that an increase in resistance cannot be suppressed.

  Therefore, the present invention provides a solar cell that can reduce the amount of conductive paste used while maintaining high output characteristics, and that can improve the connectivity between a bus bar electrode and a wiring member. With the goal.

  In order to achieve the above object, a solar cell according to one embodiment of the present invention includes a semiconductor substrate, a semiconductor layer provided over the semiconductor substrate, and a plurality of current collecting electrodes provided over the semiconductor layer. The plurality of current collecting electrodes includes a plurality of finger electrodes and a bus bar electrode provided to be connected to the plurality of finger electrodes, and the bus bar electrode is thicker than the recess and the recess. The projection has a plurality of projections and depressions alternately provided in a first direction, and a width of the projection is wider than a width of the depression in a cross section perpendicular to the semiconductor substrate and including the first direction. .

  According to the present invention, it is possible to provide a solar battery cell that can reduce the amount of conductive paste used while maintaining high output characteristics and can improve the connectivity between a bus bar electrode and a wiring member. Can be.

It is a top view by the side of the light-receiving surface of the solar cell which concerns on embodiment. It is a top view on the back side of a solar cell concerning an embodiment. FIG. 2B is a cross-sectional view of the solar cell according to the embodiment, taken along line II-II in FIG. 1A. It is a top view which expands and shows the broken line area of FIG. 1A. FIG. 4 is a cross-sectional view of the solar cell according to the embodiment, taken along line IVA-IVA in FIG. 3. FIG. 4 is a cross-sectional view corresponding to the line IVA-IVA of FIG. 3 and illustrating a state where a wiring member is arranged in the solar cell according to the embodiment. It is a top view showing other 1st examples of a bus bar electrode of a solar cell concerning an embodiment. It is a top view which shows the other 2nd example of the bus bar electrode of the solar cell which concerns on embodiment. It is a top view showing other 3rd examples of a bus bar electrode of a solar cell concerning an embodiment. It is a top view showing other 4th examples of the bus bar electrode of the solar cell concerning an embodiment. It is a top view showing other 5th examples of the bus bar electrode of the solar cell concerning an embodiment. It is a top view showing other 6th examples of the bus bar electrode of the solar cell concerning an embodiment. It is a top view which shows the other 7th example of the bus-bar electrode of the solar cell which concerns on embodiment. It is a top view showing other 8th examples of a bus bar electrode of a solar cell concerning an embodiment. It is a top view showing other ninth examples of the bus bar electrode of the solar cell concerning an embodiment. It is a top view showing other 10th examples of the bus bar electrode of the solar cell concerning an embodiment. It is a flowchart which shows the manufacturing method of the solar cell which concerns on embodiment. It is a figure showing an example of a screen version used in a manufacturing method of a solar cell concerning an embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Each of the embodiments described below shows a specific example of the present invention. Therefore, numerical values, shapes, materials, constituent elements, arrangement of constituent elements, connection forms, steps (steps), and order of steps (steps) shown in the following embodiments are merely examples, and the present invention is not limited thereto. It is not intended to be limiting. Therefore, among the components in the following embodiments, components that are not described in the independent claims that represent the highest concept of the present invention are described as arbitrary components.

  Each drawing is a schematic diagram, and is not necessarily strictly illustrated. In each of the drawings, substantially the same components are denoted by the same reference numerals, and duplicate description may be omitted or simplified in some cases.

  Further, in the present specification, a term indicating a relationship between elements such as parallel, and a term indicating a shape of an element such as a rectangle, and a numerical value, and a numerical range are not expressions expressing only a strict meaning. Is a meaning that includes a substantially equivalent range, for example, a difference of about several percent.

  In each figure, the Z-axis direction is, for example, a direction perpendicular to the light receiving surface of the solar cell. The X-axis direction and the Y-axis direction are orthogonal to each other, and both directions are orthogonal to the Z-axis direction. For example, in the following embodiments, “plan view” means viewing from the Z-axis direction.

(Embodiment)
Hereinafter, the solar cell according to the present embodiment will be described with reference to FIGS. 1A to 16.

[1. Configuration of solar cell]
First, the configuration of the solar cell according to the present embodiment will be described with reference to FIGS. 1A to 14.

  FIG. 1A is a plan view on the light receiving surface 11 side of solar cell 10 according to the present embodiment. FIG. 1B is a plan view of the back surface 12 side of solar cell 10 according to the present embodiment. FIG. 2 is a cross-sectional view of solar cell 10 according to the present embodiment, taken along line II-II in FIG. 1A.

  As shown in FIG. 1A and FIG. 1B, the planar shape of the solar cell 10 is a rectangular shape. For example, the photovoltaic cell 10 has a 125 mm square shape with the corners missing. The shape of the solar cell 10 is not limited to a rectangular shape.

  As shown in FIG. 2, the solar cell 10 has a semiconductor pn junction as its basic structure. As an example, the solar cell 10 is sequentially formed on a silicon substrate 20 and one main surface side (the Z-axis plus side) of the silicon substrate 20. Further, the n-side electrode 30n and the n-side current collecting electrode 40n, and the p-side electrode 30p and the p-side current collecting electrode 50p sequentially formed on the other main surface side (Z axis minus side) of the silicon substrate 20 are combined. Prepare. In the present embodiment, one main surface of the silicon substrate 20 is a surface on the main light receiving surface side of the solar cell 10 and is also referred to as a light receiving surface 11 hereinafter. The main light receiving surface is a surface on which more than 50% of the light incident on the solar cell 10 is incident when a solar cell module is constructed using the solar cell 10. Further, in the present embodiment, the other main surface of silicon substrate 20 is a surface facing away from one main surface of silicon substrate 20, and is also referred to as back surface 12 hereinafter. The back surface 12 is a surface opposite to the light receiving surface 11. The silicon substrate 20 is an example of a semiconductor substrate.

  The silicon substrate 20 is a crystalline silicon substrate, and is, for example, an n-type single crystal silicon substrate. Note that the silicon substrate 20 is not limited to a single-crystal silicon substrate (n-type single-crystal silicon substrate or p-type single-crystal silicon substrate), and may include a crystalline silicon substrate such as a polycrystalline silicon substrate. Good. In the following description, an example in which the silicon substrate 20 is an n-type single crystal silicon substrate will be described. Further, for example, the planar shape of the silicon substrate 20 is rectangular, and the thickness is 150 μm or less.

  On at least one of the light receiving surface 11 side and the back surface 12 side of the silicon substrate 20, an uneven shape (not shown) called a texture structure in which a plurality of pyramids are arranged two-dimensionally may be formed. Accordingly, the solar cell 10 can effectively increase the optical path length of light in the silicon substrate 20. Therefore, it is possible to increase the absorption of light that contributes to power generation without increasing the thickness of the silicon substrate 20. it can. The solar cell 10 can, for example, effectively contribute light of a wavelength having a small absorption coefficient in the silicon substrate 20 to power generation.

  An n-type semiconductor layer (see n-type semiconductor layer 80n in FIGS. 3 and 4A) and a p-type semiconductor layer (not shown) are formed on silicon substrate 20. For example, the n-type semiconductor layer 80n is disposed on the light receiving surface 11 side of the silicon substrate 20, and the p-type semiconductor layer is disposed on the back surface 12 side of the silicon substrate 20.

  The n-type semiconductor layer 80n has, for example, an i-type amorphous silicon layer 81i (intrinsic amorphous silicon layer) and an n-type amorphous silicon layer 81n. The i-type amorphous silicon layer 81i and the n-type amorphous silicon layer 81n are stacked in this order on the surface on the light receiving surface 11 side of the silicon substrate 20. Here, the term “stacking” means that the layers are stacked in the positive Z-axis direction.

The i-type amorphous silicon layer 81i is a passivation layer disposed between the silicon substrate 20 and the n-type amorphous silicon layer 81n. The i-type amorphous silicon layer 81i can be composed of amorphous silicon having a dopant content of less than 1 × 10 ¹⁹ cm ⁻³ . The n-type amorphous silicon layer 81n is a semiconductor layer having the same conductivity type as the silicon substrate 20. The n-type amorphous silicon layer 81n can be made of, for example, amorphous silicon having a content of an n-type dopant such as phosphorus (P) or arsenic (As) of 5 × 10 ¹⁹ cm ⁻³ or more. Note that the n-type semiconductor layer 80n only needs to have, for example, at least the n-type amorphous silicon layer 81n. The n-type semiconductor layer 80n is an example of a semiconductor layer.

  The p-type semiconductor layer has, for example, an i-type amorphous silicon layer (intrinsic amorphous silicon layer) and a p-type amorphous silicon layer. The i-type amorphous silicon layer and the p-type amorphous silicon layer are stacked in this order on the surface on the back surface 12 side of the silicon substrate 20. Here, the term “lamination” means that the layers are laminated in the negative Z-axis direction.

The i-type amorphous silicon layer is a passivation layer disposed between the silicon substrate 20 and the p-type amorphous silicon layer. The p-type amorphous silicon layer is a semiconductor layer having a conductivity type different from that of the silicon substrate 20. The p-type amorphous silicon layer can be made of, for example, amorphous silicon having a content of a p-type dopant such as boron (B) of 5 × 10 ¹⁹ cm ⁻³ or more. Note that the p-type semiconductor layer may have, for example, at least a p-type amorphous silicon layer.

The n-side electrode 30n and the p-side electrode 30p are, for example, transparent conductive films (TCO films) made of a transparent conductive material. The transparent conductive film has at least one of metal oxides such as indium oxide (In ₂ O ₃ ), zinc oxide (ZnO), tin oxide (SnO ₂ ), and titanium oxide (TiO ₂ ) having a polycrystalline structure. It is preferable to include a seed. These metal oxides include dopants such as tin (Sn), zinc (Zn), tungsten (W), antimony (Sb), titanium (Ti), aluminum (Al), cerium (Ce), and gallium (Ga). May be doped, and for example, ITO in which In ₂ O ₃ is doped with Sn is particularly preferable. The concentration of the dopant can be 0 to 20% by mass.

  The n-side current collecting electrode 40n is provided on the n-type semiconductor layer 80n, and is an electrode for collecting light-receiving charges (electrons) generated in the light-receiving region of the silicon substrate 20. The n-side current collecting electrode 40n includes, for example, a plurality of finger electrodes 41 linearly formed in a direction orthogonal to the extending direction of the wiring member (see the wiring member 70 shown in FIG. 1A), and these finger electrodes 41. And a plurality of bus bar electrodes 42 provided to be connected to the bus bar electrode 41. The plurality of finger electrodes 41 are formed, for example, in parallel with each other. The plurality of busbar electrodes 42 are formed linearly, for example, in a direction perpendicular to the finger electrodes 41 (for example, in a direction in which the wiring member 70 extends). Each of the plurality of bus bar electrodes 42 is, for example, connected to the wiring member 70 one-to-one. Note that the direction in which the finger electrodes 41 extend (the direction parallel to the Y axis) is an example of the second direction. Further, being provided on the n-type semiconductor layer 80n may mean that the n-side current collecting electrode 40n may be provided on the n-side electrode 30n or may be provided directly on the n-type semiconductor layer 80n. .

  The p-side current collecting electrode 50p is provided on the p-type semiconductor layer and is an electrode for collecting light-receiving charges (holes) generated in the light-receiving region of the silicon substrate 20. The p-side current collecting electrode 50p includes, for example, a plurality of finger electrodes 51 linearly formed in a direction orthogonal to the extending direction of the wiring member (see the wiring member 71 in FIG. 1B), and the finger electrodes 51. And a plurality of bus bar electrodes 52 provided so as to be connected to each other. The plurality of finger electrodes 51 are formed, for example, in parallel with each other. The plurality of busbar electrodes 52 are formed linearly, for example, along a direction perpendicular to the finger electrodes 51 (for example, a direction in which the wiring member 71 extends). Each of the plurality of busbar electrodes 52 is, for example, connected to the wiring member 71 one-to-one. Note that, “provided on the p-type semiconductor layer” means that the p-side current collecting electrode 50p may be provided on the p-side electrode 30p or may be provided directly on the p-type semiconductor layer.

  The finger electrode 41 and the finger electrode 51 are parallel in a plan view. Further, the bus bar electrode 42 and the bus bar electrode 52 are parallel in a plan view.

  The number of finger electrodes 41 and 51 and the number of bus bar electrodes 42 and 52 are not particularly limited. It is sufficient that two or more finger electrodes 41 and 51 are provided. In addition, at least one busbar electrode 42 and 52 may be provided. For example, the number of the bus bar electrodes 42 and 52 may be the same as the number of the wiring members 70 and 71, respectively. In the present embodiment, the number is three. The wiring members 70 and 71 are tab wires for electrically connecting two adjacent solar cells 10 when forming a solar cell module. Further, the case where the n-side current collecting electrode 40n and the p-side current collecting electrode 50p have the same shape is illustrated, but is not limited thereto.

  The n-side current collecting electrode 40n and the p-side current collecting electrode 50p are made of a low-resistance conductive material such as silver (Ag). For example, the n-side current collecting electrode 40n and the p-side current collecting electrode 50p are formed by screen-printing a resin-type conductive paste (silver paste or the like) in which a conductive filler such as silver particles is dispersed in a binder resin in a predetermined pattern. Can be formed. Note that the resin-type conductive paste is an example of a conductive material.

  The wiring members 70 and 71 are long conductive wires, and are, for example, ribbon-shaped metal foils. The wiring members 70 and 71 can be produced, for example, by cutting a metal foil such as a copper foil or a silver foil whose entire surface is covered with solder, silver, or the like into strips having a predetermined length. The wiring members 70 and 71 are joined to the bus bar electrode 42 by a conductive adhesive such as solder or a resin adhesive. A conductive adhesive such as solder or a resin adhesive is an example of a joining member. In the present embodiment, an example in which the joining member is a solder will be described.

  As described above, solar cell 10 according to the present embodiment is, for example, a heterojunction solar cell. This reduces defects at the interface between the silicon substrate 20 and the n-type semiconductor layer 80n and at the interface (heterojunction interface) between the silicon substrate 20 and the p-type semiconductor layer. Therefore, the photoelectric conversion efficiency of the solar cell 10 can be improved.

  Note that the passivation layer is not limited to the i-type amorphous silicon layer, and may be a silicon oxide layer, a silicon nitride layer, or the like, or may not be provided.

  Here, the configuration of the bus bar electrode according to the present embodiment will be described with reference to FIGS. In the following, the bus bar electrode 42 formed on the light receiving surface 11 side will be described, but the same applies to the bus bar electrode 52. The shape of the bus bar electrode 42 in FIGS. 3 to 14 shows the shape after the conductive paste is printed and cured. FIG. 3 is an enlarged plan view showing a broken line area A in FIG. 1A.

  As shown in FIG. 3, the bus bar electrode 42 has a bus bar portion 43 and an uneven portion 44. The bus bar portion 43 is formed to extend in a direction in which the bus bar electrode 42 extends. The bus bar portion 43 is electrically connected to each of the ends of the concave portion 45 and the convex portion 46 which are alternately arranged. FIG. 3 shows an example in which a pair of bus bar portions 43 are formed so as to sandwich the uneven portion 44. That is, the bus bar electrode 42 has the bus bar portion 43 electrically connected to each of the one end and the other end of the plurality of concave portions 45 and the plurality of convex portions 46. In the example of FIG. 3, the direction in which the bus bar portion 43 extends is a direction parallel to a first direction described later (for example, the X-axis direction). The number of the bus bar portions 43 is not particularly limited, and may be one, or three or more.

  The plurality of concave and convex portions 44 are provided with a plurality of concave portions 45 and convex portions 46 thicker than the concave portions 45 alternately in the direction in which the bus bar electrodes 42 extend. In the example of FIG. 3, a plurality of uneven portions 44 are provided alternately along the direction in which the bus bar portions 43 extend. The direction in which the concave portions 45 and the convex portions 46 are alternately arranged (the X-axis direction in the example of FIG. 3) is an example of the first direction. Further, the concave portion 45 and the convex portion 46 are, for example, rectangular in plan view. Each of the concave portion 45 and the convex portion 46 extends, for example, in a direction (an example of a third direction) parallel to a direction in which the finger electrode 41 extends (an example of a second direction and a Y-axis direction). Is formed.

  The shape of the concave portion 45 and the convex portion 46 in plan view is not limited to a rectangular shape. For example, the plan-view shapes of the concave portion 45 and the convex portion 46 may be elliptical, polygonal, or other shapes.

  Further, as shown in FIG. 3, a plurality of concave portions 45 and convex portions 46 are provided between adjacent finger electrodes 41. FIG. 3 shows an example in which approximately five concave portions 45 and convex portions 46 are provided between adjacent finger electrodes 41, but the present invention is not limited to this. For example, each of the concave portions 45 and the convex portions 46 may be provided with, for example, ten or more between the adjacent finger electrodes 41. That is, ten or more concave portions 45 may be provided between the adjacent finger electrodes 41. As described above, the width w1 of the concave portion 45 is smaller than the pitch (for example, 1 to 3 mm) at which the finger electrodes 41 are provided. In other words, the bus bar electrode 42 is provided with a plurality of recesses 45 having a width w1 smaller than the pitch of the finger electrodes 41. Thus, the surface area of the bus bar electrode 42 in the uneven portion 44 can be increased as compared with the case where the thickness of the bus bar electrode 42 is uniform.

  Note that a plurality of recesses 45 may be provided between each of the adjacent finger electrodes 41 among the plurality of finger electrodes 41. Further, the concave portions 45 may be formed, for example, in a number larger than the number of the finger electrodes 41.

  The bleeding portion 49 shown in FIG. 3 indicates a portion where the bleeding toward the outside of the finger electrode 41 and the busbar electrode 42 occurs when the finger electrode 41 and the busbar electrode 42 are formed by screen printing.

  Here, the concave portion 45 and the convex portion 46 will be described with reference to FIGS. 4A and 4B. FIG. 4A is a cross-sectional view of solar cell 10 according to the present embodiment, taken along line IVA-IVA in FIG. 3. FIG. 4B is a cross-sectional view corresponding to line IVA-IVA of FIG. 3 and illustrating a state where wiring member 70 is arranged in solar cell 10 according to the present embodiment.

  As shown in FIG. 4A, the concave portion 45 is defined as a region of the uneven portion 44 corresponding to a thickness t2 corresponding to 10% of the thickness t1 indicated by the difference between the top and the valley of the uneven portion 44. That is, the concave portion 45 is a region of the uneven portion 44 from the surface of the n-side electrode 30n to the lowest point in the valley of the uneven portion 44 to the height of the thickness t2. The convex portion 46 is a region of the concave-convex portion 44 having a height equal to or greater than the thickness t2 from the lowest point in the valley of the concave-convex portion 44.

  The width w2 of the convex portion 46 thus defined is wider than the width w1 of the concave portion 45 in a cross section perpendicular to the silicon substrate 20 and including the first direction. For example, the width w2 of the projection 46 may be 300 μm or less, 200 μm or less, or 100 μm or less. The width w1 of the concave portion 45 may be smaller than the width w2, for example, 100 μm or less. As shown in FIG. 3, in such a concave portion 45 and a convex portion 46, the area of the concave portion 45 in a plan view is smaller. The thickness of the top of the projection 46 (the thickness of the n-side electrode 30n and the top) is, for example, 10 μm. Further, the thickness of the bus bar portion 43 and the thickness of the top portion are, for example, the same thickness.

  As shown in FIG. 4B, the bus bar electrode 42 has the uneven portion 44, so that the surface area of the bus bar electrode 42 is larger than that of the related art. That is, it is possible to increase the area of the joint surface between the solder 60 for joining the wiring member 70 and the bus bar electrode 42 and the bus bar electrode 42. Further, in the related art, the central portion of the bus bar electrode may be dented due to the saddle phenomenon during printing, and the contact point between the wiring member 70 and the bus bar electrode may be reduced. On the other hand, since the uneven portion 44 is formed at the center of the bus bar electrode 42, the wiring member 70 can contact the plurality of convex portions 46 in the uneven portion 44. That is, the area where the wiring member 70 and the bus bar electrode 42 are in direct contact can be increased.

  Thus, the connectivity between the wiring member 70 and the bus bar electrode 42 can be improved. Specifically, the adhesive strength between the wiring member 70 and the bus bar electrode 42 and the conductivity can be improved.

  Further, the n-side electrode 30n and the solder 60 are not joined. That is, it is preferable that the n-side electrode 30n and the solder 60 do not directly contact each other. Therefore, for example, when the n-side electrode 30n is exposed in the concave portion 45, the exposed area, that is, the area in which the n-side electrode 30n and the solder 60 are in direct contact with each other, is preferably small. As shown in FIG. 4A, in the concave portion 45, the width w2 of the convex portion 46 is wider than the width w1 of the concave portion 45, so that the exposed area is reduced even when the n-side electrode 30 n is exposed in the concave portion 45. Therefore, a decrease in the adhesive strength between the bus bar electrode 42 and the wiring member 70 can be suppressed.

  As shown in FIG. 4A, in the present embodiment, n-side electrode 30n is covered with conductive paste forming bus bar electrode 42 in concave portion 45, that is, is not exposed in plan view. Thereby, it is possible to suppress a decrease in the adhesive strength due to the direct contact of the solder 60 with the n-side electrode 30n. Note that at least a part of the n-side electrode 30n may be exposed in the recess 45. That is, at least a part of the solder 60 may be in contact with the n-side electrode 30n in the recess 45 in a state where the wiring member 70 is connected.

  When the bus bar electrode 42 is provided directly on the n-type semiconductor layer 80n, the n-type semiconductor layer 80n is covered with the conductive paste forming the bus bar electrode 42 in the concave portion 45, that is, in plan view. Not exposed. Thereby, it is possible to suppress a decrease in adhesive strength due to the direct contact of the solder 60 with the n-type semiconductor layer 80n. Note that at least a part of the n-type semiconductor layer 80n may be exposed in the recess 45. That is, at least a part of the solder 60 may be in contact with the n-type semiconductor layer 80n in the concave portion 45 in a state where the wiring member 70 is connected.

  Further, that the n-type semiconductor layer 80n is covered with the conductive paste forming the bus bar electrode 42 in the concave portion 45 means that the conductive paste is provided on the n-type semiconductor layer 80n. For example, that the n-type semiconductor layer 80n is covered with the conductive paste forming the bus bar electrode 42 means that the n-type semiconductor layer 80n is covered with the conductive paste via the n-side electrode 30n (for example, 4A) and that the n-type semiconductor layer 80n is directly covered with the conductive paste.

  The bus bar electrode in the conventional solar cell does not have the uneven portion 44 and has, for example, a uniform thickness. In this case, when the bus bar electrode is formed by screen printing, the conductive paste is printed on all the regions constituting the bus bar electrode at the time of printing.

  On the other hand, the bus bar electrode 42 according to the present embodiment can be formed by screen printing using a screen plate having no opening (see the bus bar hole 112 shown in FIG. 16) at a position corresponding to the recess 45. It is. Specifically, the concave portion 45 is formed by printing bleeding of the conductive paste applied to a position corresponding to the convex portion 46. That is, in the present embodiment, the conductive paste is not printed on all the regions constituting the bus bar electrodes. As a result, the amount of the conductive paste used can be reduced as compared with the related art. Note that printing bleeding refers to a phenomenon in which the conductive paste leaks and spreads to the surroundings after the conductive paste is applied onto the silicon substrate 20 and before it is cured.

  Further, as shown in FIG. 4A, the cross-sectional shape of the uneven portion 44 is, for example, a trapezoid. Thereby, as shown in FIG. 4B, the top of the convex portion 46 and the wiring member 70 are in direct surface contact, for example.

  The shape of the bus bar electrode 42 is not limited to the above. Other shapes and the like of the bus bar electrode 42 will be described with reference to FIGS.

  FIG. 5 is a plan view showing another first example of the bus bar electrode of solar cell 10 according to the present embodiment. As shown in FIG. 5, the bus bar electrode 42a has a bus bar portion 43 and an uneven portion 44a. The bus bar electrode 42a according to another first example is different from the bus bar electrode 42 shown in FIG. 3 in the direction in which the concave portions 45a and the convex portions 46a forming the concave and convex portions 44a are arranged.

  A plurality of the concave and convex portions 44a are provided alternately in a direction in which the concave portions 45a and the convex portions 46a having a thickness larger than the concave portions 45a intersect with the direction in which the bus bar electrodes 42a extend (X-axis direction). Specifically, a plurality of concave portions 45a and convex portions 46a are provided alternately in a direction orthogonal to the direction in which the bus bar electrodes 42a extend. The direction in which the concave portions 45a and the convex portions 46a are alternately arranged (the Y-axis direction in the example of FIG. 5) is an example of the first direction. Further, the concave portion 45a and the convex portion 46a are, for example, rectangular in plan view. The concave portion 45a and the convex portion 46a are formed, for example, to extend in a direction (an example of a third direction, an X-axis direction) orthogonal to a direction in which the finger electrode 41 extends (an example of the second direction). Have been. The width w2 of the convex portion 46a is wider than the width w1 of the concave portion 45a in a cross section perpendicular to the silicon substrate 20 and including a direction in which the concave portions 45a and the convex portions 46a are alternately arranged (Y-axis direction).

  FIG. 6 is a plan view showing another second example of the bus bar electrode of solar cell 10 according to the present embodiment. As shown in FIG. 6, the bus bar electrode 42b has a bus bar portion 43 and an uneven portion 44b. The bus bar electrode 42b according to the other second example is different from the bus bar electrode 42 shown in FIG. 3 in the direction in which the concave portion 45b and the convex portion 46b forming the concave / convex portion 44b extend.

  The concave-convex portions 44b are provided with a plurality of concave portions 45b and convex portions 46b thicker than the concave portions 45b alternately in the direction (X-axis direction) in which the bus bar electrodes 42b extend. The direction in which the concave portions 45b and the convex portions 46b are alternately arranged (the X-axis direction in the example of FIG. 6) is an example of the first direction. Further, the concave portion 45b and the convex portion 46b are, for example, rectangular in plan view. The concave portion 45b and the convex portion 46b are formed to extend in a direction (an example of a third direction) intersecting with a direction in which the finger electrode 41 extends (an example of the second direction), for example. Here, the intersecting directions are directions excluding a direction parallel to and orthogonal to the direction in which the finger electrodes 41 extend. That is, to intersect means that the direction in which the finger electrode 41 extends and the direction in which the concave portion 45b and the convex portion 46b extend intersect at an angle other than a right angle. The width w2 of the convex portion 46b is wider than the width w1 of the concave portion 45b in a cross section perpendicular to the silicon substrate 20 and including a direction in which the concave portions 45b and the convex portions 46b are alternately arranged (X-axis direction).

  FIG. 7 is a plan view showing another third example of the bus bar electrode of solar cell 10 according to the present embodiment. As shown in FIG. 7, the bus bar electrode 42c has a bus bar portion 43c and an uneven portion 44c. The bus bar electrode 42c according to the other third example is different from the bus bar electrode 42 shown in FIG. 3 in the position where the bus bar portion 43c is provided.

  The plurality of bus bar portions 43c are formed in the direction in which the bus bar electrodes 42c extend. The bus bar portion 43c electrically connects each of the adjacent convex portions 46c. The bus bar portion 43c is formed, for example, so as to separate the concave portion 45c extending in the Y-axis direction at the center. This can increase the contact area between the wiring member and the bus bar electrode 42 as compared with the case where the bus bar portion 43c is not formed, thereby improving the connectivity between the wiring member 70 and the bus bar electrode 42. it can. Further, since the protrusions 46c are electrically connected to each other by the bus bar 43, the current collection efficiency can be improved. Note that the number of the bus bar portions 43c is not limited to one. For example, the bus bar portion 43 shown in FIG. 3 may be further provided on the bus bar electrode 42c shown in FIG.

  The plurality of concave and convex portions 44c are provided alternately in the direction (X-axis direction) in which the bus bar electrodes 42c extend (the X-axis direction). The direction in which the concave portions 45c and the convex portions 46c are alternately arranged (the X-axis direction in the example of FIG. 7) is an example of the first direction. Further, the concave portion 45c and the convex portion 46c are, for example, rectangular in plan view. The concave portion 45c and the convex portion 46c are formed to extend in a direction (an example of a third direction) parallel to a direction in which the finger electrode 41 extends (an example of the second direction). The width w2 of the convex portion 46c is wider than the width w1 of the concave portion 45c in a cross section perpendicular to the silicon substrate 20 and including a direction in which the concave portions 45c and the convex portions 46c are alternately arranged (X-axis direction).

  Note that the bus bar electrode is not limited to having the bus bar portion. For example, as shown in FIG. 8, the bus bar electrode 42d may have only the uneven portion 44c among the bus bar portion 43c and the uneven portion 44c shown in FIG. FIG. 8 is a plan view showing another fourth example of the bus bar electrode of solar cell 10 according to the present embodiment. The bus bar electrode 42d according to another fourth example is different from the bus bar electrode 42c shown in FIG. 7 in that the bus bar electrode 42d does not have the bus bar portion 43c.

  The uneven portion 44c does not contribute much to current collection, but has a larger surface area than when the uneven portion 44c is flat, so that the connectivity between the wiring member 70 and the bus bar electrode 42d can be improved.

  FIG. 9 is a plan view showing another fifth example of the bus bar electrode of solar cell 10 according to the present embodiment. FIG. 9 is a plan view showing the bus bar electrode 42e corresponding to the broken line area B shown in FIG. As shown in FIG. 9, the bus bar electrode 42e has an uneven portion 44e. The bus bar electrode 42e according to the other fifth example is different from the bus bar electrode 42d shown in FIG. 8 in that the recess 45e has an exposed portion 47e in which the n-side electrode 30n is exposed.

  The exposed portion 47e from which the n-side electrode 30n is exposed in plan view is formed only in the concave portion 45e of the concave portion 45e and the convex portion 46e. That is, in plan view, the area of the exposed portion 47e is smaller than the area where the conductive paste is formed. Even when the exposed portion 47e is formed as described above, the width w2 of the convex portion 46e is equal to the width of the concave portion 45e in a section perpendicular to the silicon substrate 20 and including the first direction (the X-axis direction in FIG. 9). Therefore, the connectivity between the wiring member 70 and the bus bar electrode 42e can be improved by a portion other than the exposed portion 47e of the convex portion 46e and the concave portion 45e.

  FIGS. 3 and 5 to 9 show examples in which the concavo-convex portion is formed from one end to the other end of the bus bar electrode. However, the present invention is not limited to this. The uneven portion may be formed on at least a part of the bus bar electrode. This example will be described with reference to FIGS.

  FIG. 10 is a plan view showing another sixth example of the bus bar electrode of solar cell 10 according to the present embodiment. As illustrated in FIG. 10, the bus bar electrode 42f has a joint 47f (an example of a connection part) that joins with the wiring member 70 and an unjoined part 48f that is not joined with the wiring member 70. And the uneven part 44f is formed only in the joint part 47f of the joint part 47f and the unjoined part 48f. In the joining portion 47f, in order to increase the surface area of the bus bar electrode 42f, an uneven portion 44f is formed from the viewpoint of improving the adhesion to the wiring member 70. On the other hand, in the unbonded portion 48f, the bus bar portion 43f is formed from the viewpoint of further reducing the amount of the conductive paste used. That is, the uneven portion 44f is not formed in the unjoined portion 48f.

  With such a configuration, it is possible to further reduce the amount of the conductive paste used in the unjoined portion 48f while improving the connectivity with the wiring member 70 in the joined portion 47f. Further, there is also an effect of preventing cell cracking during a temperature cycle test.

  The bus bar portion 43f is formed in the unjoined portion 48f. The bus bar portion 43f is provided so as to electrically connect the adjacent bus bar portions 43f, so that the power collection efficiency is improved as compared with a case where the bus bar portion 43f is not formed.

  Note that FIG. 10 illustrates an example in which the uneven portion 44 formed on the bonding portion 47f has a shape corresponding to the uneven portion 44 illustrated in FIG. 3, but the shape of the uneven portion 44f is not limited thereto. For example, the uneven portion shown in any of FIGS.

  FIG. 11 is a plan view showing another seventh example of the bus bar electrode of solar cell 10 according to the present embodiment. As shown in FIG. 11, the bus bar electrode 42g has an uneven portion 44g at an intersection 47g where the finger electrode 41 and the bus bar electrode 42g intersect. In the intersection 47g, an uneven portion 44g is formed in order to increase the surface area of the bus bar electrode 42g from the viewpoint of improving the adhesion to the wiring member 70. The bus bar portion 44g is directly connected to the finger electrode 41, for example. On the other hand, between adjacent finger electrodes 41, a bus bar portion 43g is formed from the viewpoint of further reducing the amount of conductive paste used. That is, the uneven portion 44g is not formed between the adjacent finger electrodes 41.

  By improving the connectivity between the wiring member 70 and the bus bar electrode 42g at the intersection 47g, for example, the received charges (for example, electrons) collected by the finger electrode 41 can efficiently flow through the wiring member 70. . In addition, since the uneven portion 44g is formed for each intersection 47g, the adhesive strength at the intersection 47g between each of the plurality of finger electrodes 41 and the bus bar electrode 42g can be made uniform. The bus bar portion 43g is provided so as to electrically connect the adjacent uneven portions 44g. Note that the bus bar portion 43g may not be provided.

  In addition, the uneven | corrugated part 44g is not limited to being formed in all the intersection parts 47g. For example, as shown in FIG. 12, the uneven portion 44g may not be formed in all the intersections 47g. FIG. 12 is a plan view showing another eighth example of the bus bar electrode of solar cell 10 according to the present embodiment. The uneven portion 44g of the bus bar electrode 42h according to the other eighth example may be provided on at least one of the plurality of intersections 47g. The uneven portion 44g may be provided, for example, every other one of the plurality of intersections 47g. The bus bar portion 43h is provided so as to electrically connect the adjacent uneven portions 44g, and intersects with at least one finger electrode 41 between the adjacent uneven portions 44g. Thus, the amount of the conductive paste used can be further reduced.

  FIGS. 11 and 12 show an example in which the uneven portion 44g formed in the intersection 47g has a shape corresponding to the uneven portion 44 shown in FIG. 3, but the shape of the uneven portion 44g is not limited to this. However, for example, the uneven portion shown in any of FIGS. 5 to 9 may be used.

  Further, as shown in FIG. 3, when the bus bar electrode 42 has the bus bar portion 43 and the uneven portion 44, the relationship between the thickness of the bus bar portion 43 and the uneven portion 44 will be described with reference to FIGS. 13 and 14. I do.

  FIG. 13 is a plan view showing another ninth example of the bus bar electrode 42 of the solar cell 10 according to the present embodiment. Specifically, FIG. 13 illustrates an example in which the width w3 of the bus bar electrode 42 is wider than the width w4 of the wiring member 70.

  As shown in FIG. 13, when the width w3 of the bus bar electrode 42 is wider than the width w4 of the wiring member 70, the thickness t4 of the uneven portion 44 may be formed larger than the thickness t3 of the bus bar portion 43, or may be larger than the thickness t3. It may be formed thin or may be equal to the thickness t3. That is, when the width w3 of the bus bar electrode 42 is wider than the width w4 of the wiring member 70, the relationship between the thickness t3 and the thickness t4 is not particularly limited. Note that the thickness t4 of the uneven portion 44 specifically means the thickness of the convex portion 46. In addition, the bleed portion 49 is not included in the width w3 of the bus bar electrode 42.

  FIG. 14 is a plan view showing another tenth example of the bus bar electrode 42 of the solar cell according to the present embodiment. Specifically, FIG. 14 shows an example in which the width w3 of the bus bar electrode 42 is smaller than the width w4 of the wiring member 70.

  As shown in FIG. 14, when the width w4 of the wiring member 70 is wider than the width w3 of the bus bar electrode 42, the thickness t4 of the uneven portion 44 is formed to be equal to or greater than the thickness t3 of the bus bar portion 43. When the thickness t3 of the bus bar portion 43 is larger than the thickness t4 of the uneven portion 44, there is a possibility that the wiring member 70 does not directly contact the convex portion 46 in the uneven portion 44. Therefore, from the viewpoint of improving the electrical conductivity between the uneven portion 44 and the wiring member 70, the thickness t3 of the bus bar portion 43 is preferably smaller than the thickness t4 of the convex portion 46. Thereby, the connectivity between the uneven portion 44 and the wiring member 70 can be further improved.

  Note that the thickness t3 may be a statistical value of the thickness of the bus bar portion 43. The thickness t3 may be a maximum value, a minimum value, an average value, or a median value of the thickness in the bus bar portion 43. Further, the thickness t4 may be a statistical value of the thickness of the protrusion 46. The thickness t4 may be a maximum value, a minimum value, an average value, or a median value of the thickness of the plurality of protrusions 46.

[2. Method for manufacturing solar cell]
Next, a method for manufacturing solar cell 10 according to the present embodiment will be described with reference to FIGS. FIG. 15 is a flowchart illustrating a method for manufacturing solar cell 10 according to the present embodiment.

  As shown in FIG. 15, first, a silicon substrate 20 is prepared (S10). Then, a transparent electrode layer is formed on the silicon substrate 20 (S20). The transparent electrode layer includes an n-side electrode 30n and a p-side electrode 30p. Then, a current collecting electrode is formed on the transparent electrode layer using a screen plate (S30). The current collecting electrode includes a finger electrode and a bus bar electrode. For example, the finger electrode 41 and the bus bar electrode 42 are formed integrally, and the finger electrode 51 and the bus bar electrode 52 are formed integrally.

  FIG. 16 is a diagram illustrating an example of a screen plate 100 used in the method for manufacturing solar cell 10 according to the present embodiment. The case where the screen plate 100 is a screen plate for forming the bus bar electrode 42 shown in FIG. 3 will be described. When the bus bar electrodes shown in FIGS. 5 to 12 are formed, a pattern corresponding to the shape of the bus bar electrodes is formed on the screen plate 100.

  As shown in FIG. 16, the screen plate 100 includes a pattern hole 110 and an emulsion 120. The screen plate 100 is formed by meshing a frame. An emulsion (photosensitive emulsion) 120 is applied to the mesh, and the emulsion 120 is hardened by exposure. At this time, a portion of the emulsion 120 that has not been cured by masking is washed away and becomes the pattern hole 110. The pattern hole 110 is formed in accordance with the shape of the current collecting electrode to be printed on the solar cell, and the mesh is exposed in the pattern hole 110.

  The pattern hole 110 has a finger hole 111 for forming the finger electrode 41 and a busbar hole 112 for forming the busbar electrode 42. The busbar hole 112 includes the emulsion 121. In other words, the busbar hole 112 is formed in a ladder shape.

  In step S30, the conductive paste is supplied to the screen plate 100, and the pattern hole 110 is filled with the conductive paste by, for example, spreading with a squeegee or the like. After being applied to the solar cell, the conductive paste adheres to the solar cell by, for example, firing.

  When a conductive paste is printed on the silicon substrate 20 using such a screen plate 100, the conductive paste is not applied to a region corresponding to the emulsion 121. That is, at the moment when the conductive paste is printed, the transparent electrode film (for example, the n-side electrode 30n) is exposed in the region corresponding to the emulsion 121. The bleeding (printing bleeding) of the conductive paste occurs after the conductive paste is printed and before it is cured by firing. Specifically, the conductive paste printed by the bus bar holes 112 flows into a region corresponding to the emulsion 121 and where the transparent electrode film is exposed (also referred to as an unprinted region). Thus, a layer of the conductive paste is also formed by the emulsion 121 in the uncoated region. By curing the conductive paste in this state, the above-described bus bar electrode 42 is formed.

  The emulsion 121 may be, for example, large enough to form a conductive paste layer on all of the uncoated areas due to printing bleed. The width w5 of the emulsion 121 may be appropriately determined according to the bleed width of the conductive paste printing bleed. For example, when the print bleed width is 50 μm, the width w5 of the emulsion 121 may be set to 100 μm or less. By setting the width w5 of the emulsion 121 finely to 100 μm or less, the formed concave portion 45 can be filled with the conductive paste.

  As described above, the uncoated area can be completely filled by printing bleeding. That is, the solar cell 10 having no exposed portion where the n-side electrode 30n is exposed can be manufactured as the bus bar electrode 42 in a plan view. Also, by making the width w5 of the emulsion 121 larger than twice the bleeding width, it is possible to form the exposed portion 47e as shown in FIG.

  As described above, solar cell 10 according to the present embodiment intentionally forms a portion (part corresponding to emulsion 121) where conductive paste is not applied in busbar electrode 42 when busbar electrode 42 is formed. Form. Then, when the conductive paste flows into the portion due to the bleeding of the conductive paste printed around the portion, at least a part of the transparent electrode film in the portion is covered with the conductive paste.

[3. Effects etc.]
As described above, solar cell 10 according to the present embodiment is provided on silicon substrate 20, n-type semiconductor layer 80n (an example of a semiconductor layer) provided on silicon substrate 20, and n-type semiconductor layer 80n. A plurality of current collecting electrodes (for example, an n-side current collecting electrode 40n). The plurality of current collecting electrodes include a plurality of mutually parallel finger electrodes 41 and a bus bar electrode 42 provided to be connected to the plurality of finger electrodes 41. The bus bar electrode 42 has an uneven portion 44 in which a plurality of concave portions 45 and convex portions 46 thicker than the concave portions 45 are provided alternately in a first direction (for example, the X-axis direction). The width w2 is wider than the width w1 of the concave portion 45 in a cross section perpendicular to the silicon substrate 20 and including the first direction.

  Thus, by forming the recess 45 in the bus bar electrode 42, the amount of the conductive paste used can be reduced as compared with the case where the bus bar electrode 42 is formed to have a uniform thickness. For example, when the bus bar electrode 42 is formed by printing, the amount of the conductive paste applied to the region corresponding to the concave portion 45 is made smaller than the amount of the conductive paste applied to the region corresponding to the convex portion 46 so that the concave portion 45 is formed. As a result, the amount of conductive paste used can be reduced. Further, by forming the uneven portion 44 in which the width w2 of the convex portion 46 is larger than the width w1 of the concave portion 45, the connecting member (for example, solder 60) for connecting the wiring member 70 and the busbar electrode 42 and the busbar electrode 42 are formed. The contact area can be increased as compared with the case where the thickness of the bus bar electrode 42 is uniform. That is, the connection strength between the bus bar electrode 42 and the wiring member 70 can be improved. Further, by forming the uneven portion 44 in which the width w2 of the convex portion 46 is larger than the width w1 of the concave portion 45, it is possible to suppress an increase in the resistance value of the bus bar electrode 42, which causes a decrease in output characteristics of the solar cell 10 I can do this. Therefore, solar cell 10 according to the present embodiment can reduce the amount of conductive paste used while maintaining high output characteristics, and improves the connectivity between bus bar electrode 42 and wiring member 70. be able to.

  Further, each of the concave portion 45 and the convex portion 46 is provided between the finger electrodes 41 adjacent to each other among the plurality of finger electrodes 41.

  Thereby, the concave portions 45 are provided at a finer pitch than the finger electrodes 41. When the concave portion 45 is formed by bleeding of the conductive paste applied by screen printing, the concave portion 45 can be filled with the conductive paste. In other words, the fine pitch of the concave portions 45 prevents direct contact between the n-side electrode 30n and the bonding member (for example, the solder 60) that connects the wiring member 70 and the bus bar electrode 42 in the concave portions 45. it can. Accordingly, a decrease in the adhesive strength between the bus bar electrode 42 and the wiring member 70 due to the direct contact between the n-side electrode 30n and the joining member can be suppressed, and the connectivity is further improved.

  Further, the plurality of finger electrodes 41 are formed to extend in the second direction (for example, the X-axis direction) in plan view of the silicon substrate 20, and the concave portion 45 b and the convex portion 46 b are formed in the silicon substrate 20. May be formed to extend in a third direction intersecting with the second direction in a plan view. In addition, the concave portion 45a and the convex portion 46a may be formed to extend in a third direction (for example, the X-axis direction) orthogonal to the second direction in a plan view of the silicon substrate 20. In addition, the concave portions 45 and the convex portions 46 may be formed to extend in a third direction (for example, the Y-axis direction) parallel to the second direction in plan view of the silicon substrate 20.

  Accordingly, the bus bar electrode having the concave and convex portions having the concave portion and the convex portion extending in the third direction can reduce the amount of the conductive paste used and connect the bus bar electrode to the wiring member 70. Performance can be improved.

  The bus bar electrode 42 is provided to extend in the first direction, and is electrically connected to each of one end and the other end of the plurality of concave portions 45 and the plurality of convex portions 46 extending in the third direction. It has a pair of busbar portions 43 to be connected.

  Thereby, the contact area between the wiring member 70 and the bus bar electrode 42 can be further increased as compared with the case where the bus bar portion 43 is not formed, so that the connectivity between the wiring member 70 and the bus bar electrode 42 is further improved. be able to.

  The uneven portion 44g may be provided at an intersection 47g where the bus bar electrode 42g and the plurality of finger electrodes 41 intersect.

  Thus, the amount of the conductive paste used can be reduced as compared with the case where the uneven portion 44g is formed over the bus bar electrode 42g.

  Further, the bus bar electrode 42f is connected to a wiring member 70 for electrically connecting the solar cells 10 to each other, and the concave and convex portions 44f are provided at a joint 47f where the wiring member 70 and the bus bar electrode 42f are connected. You may.

  Thereby, the connectivity between the wiring member 70 and the bus bar electrode 42f can be effectively improved. Further, the amount of the conductive paste used can be reduced as compared with the case where the uneven portions 44f are formed over the bus bar electrodes 42f.

  In the recess 45, the n-type semiconductor layer 80n is covered with a conductive material forming the bus bar electrode 42.

  Accordingly, it is possible to suppress a decrease in bonding strength caused by the solder 60 that bonds the bus bar electrode 42 and the wiring member 70 coming into direct contact with the n-side electrode 30n.

(Other embodiments)
As described above, the solar battery cell according to the present invention has been described based on the embodiments, but the present invention is not limited to the above embodiments.

  For example, in the above-described embodiment, the example in which the n-type semiconductor layer is formed on the surface on the main light receiving surface side of the solar cell is described, but the present invention is not limited to this. A p-type semiconductor layer may be formed on the surface on the main light receiving surface side of the solar cell.

  Further, in the above-described embodiment, an example in which two adjacent solar cells are electrically connected to each other by a wiring member has been described, but the present invention is not limited to this. For example, the bus bar electrode on the light receiving surface side of one solar cell may be directly connected to the bus bar electrode on the back side of the other solar cell. Even in such a case, according to the solar cell according to the above-described embodiment, it is possible to reduce the amount of conductive paste used while maintaining high output characteristics, and to reduce the amount of two adjacent solar cells. Connectivity can be improved.

  Further, in the above embodiment, the example in which the current collecting electrode includes both the finger electrode and the bus bar electrode has been described, but the present invention is not limited to this. The collecting electrode only needs to include at least the bus bar electrode.

  Further, in the above embodiment, the portion up to the thickness t2 in the uneven portion is formed as the concave portion, but the present invention is not limited to this. The concave portion may be, for example, a portion where the conductive paste is not disposed after curing. In this case, the protrusion may be defined as a portion where the conductive paste is arranged after curing. Even in this case, the width of the convex portion is wider than the width of the concave portion in a cross section perpendicular to the silicon substrate and including the first direction. Thereby, the same effect as in the above-described embodiment can be obtained.

  Further, the present invention may be realized as a solar cell module including a plurality of solar cells and a wiring member that electrically connects adjacent solar cells. In this case, at least one of the plurality of solar cells included in the solar cell module is the solar cell described in the above embodiment.

  In addition, the order of each step in the method for manufacturing a solar cell described in the above embodiment is an example, and the present invention is not limited to this. The order of each step may be interchanged, or a part of each step may not be performed.

  Further, each step in the method for manufacturing a solar cell described in the above embodiment may be performed in one step, or may be performed in separate steps. Note that the term “implemented in one step” includes an intention that each step is executed using one apparatus, each step is executed continuously, or each step is executed in the same place. It is. Separate steps mean that each step is performed using a different device, that each step is performed at a different time (eg, on a different day), or that each step is performed at a different location. It is intended to include.

  In addition, the present invention is realized by arbitrarily combining the components and functions in each embodiment and the like without departing from the spirit of the present invention and in the form obtained by applying various modifications that can be conceived by those skilled in the art to each embodiment. Embodiments are also included in the present invention.

10 solar cell 20 silicon substrate (semiconductor substrate)
40n n side current collecting electrode (current collecting electrode)
41 finger electrodes 42, 42a to 42h bus bar electrodes 43, 43c, 43f, 43g bus bar portions 44, 44a to 44c, 44e to 44f uneven portions 45, 45a to 45c, 45e to 45f concave portions 46, 46a to 46c, 46e to 46f convex Part 47f joining part (connection part)
47g Intersection 70, 71 Wiring member 80n N-type semiconductor layer (semiconductor layer)
w1, w2, w3, w4 width t3, t4 thickness

Claims (9)

A semiconductor substrate;
A semiconductor layer provided on the semiconductor substrate,
Comprising a plurality of current collecting electrodes provided on the semiconductor layer,
The plurality of current collecting electrodes has a plurality of finger electrodes and a bus bar electrode provided to be connected to the plurality of finger electrodes,
The busbar electrode has a concave and convex portion in which a plurality of concave portions and convex portions having a thickness greater than the concave portion are alternately provided in the first direction,
A solar cell having a width of the convex portion larger than a width of the concave portion in a cross section perpendicular to the semiconductor substrate and including the first direction. The solar cell according to claim 1, wherein a plurality of the recesses and the plurality of the protrusions are provided between adjacent ones of the plurality of finger electrodes. The plurality of finger electrodes are formed to extend in a second direction in a plan view of the semiconductor substrate,
The solar cell according to claim 1, wherein the concave portion and the convex portion are formed to extend in a third direction that intersects the second direction in a plan view of the semiconductor substrate. The plurality of finger electrodes are formed to extend in a second direction in a plan view of the semiconductor substrate,
The solar cell according to claim 1, wherein the concave portion and the convex portion are formed to extend in a third direction orthogonal to the second direction in a plan view of the semiconductor substrate. The plurality of finger electrodes are formed to extend in a second direction in a plan view of the semiconductor substrate,
The solar cell according to claim 1, wherein the concave portion and the convex portion are formed to extend in a third direction parallel to the second direction in a plan view of the semiconductor substrate. The bus bar electrode is provided to extend in the first direction, and is electrically connected to one end and the other end of each of the plurality of recesses and the plurality of protrusions extending in the third direction. The solar cell according to any one of claims 3 to 5, further comprising a pair of busbar portions to be connected. The solar cell according to any one of claims 1 to 6, wherein the uneven portion is provided at an intersection where the bus bar electrode and the plurality of finger electrodes intersect. The bus bar electrode is connected to a wiring member for electrically connecting the solar cells,
The solar cell according to any one of claims 1 to 6, wherein the uneven portion is provided at a connection portion where the wiring member and the bus bar electrode are connected. The solar cell according to any one of claims 1 to 8, wherein, in the recess, the semiconductor layer is covered with a conductive material forming the bus bar electrode.

Images