Method for manufacturing solar cell and solar cell

Abstract

To provide a method for manufacturing a solar cell capable of suppressing a decrease in performance of the solar cell even when a manufacturing process is simplified and the cost of the solar cell is made cheaper.SOLUTION: A method for manufacturing a solar cell includes the steps of: forming material films of a transparent electrode layer, a metal electrode layer, and a conductive protection layer on a first semiconductor layer 25 and a second semiconductor layer 35; forming a first insulation layer 41 entirely covering the first region except a first non-insulation region 41a and a second insulation layer 42 entirely covering the second region except a second non-insulation region 42a; forming a contact electrode 51 in a first non-insulation region and a contact electrode 52 in a second non-insulation region; and forming transparent electrode layers 28 and 38, metal electrode layers 29 and 39, and conductive protection layers 27P and 37P using an etching method for using the first insulation layer, the second insulation layer, and the contact electrode as a mask. The contact electrode forming step prints and cures or dries a printing material containing particulate metal material and resin material.SELECTED DRAWING: Figure 2A

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a solar cell and a solar cell. [Background technology]

[0002] Patent documents 1 to 3 disclose techniques relating to the connection of electrodes of two polarities and wiring members in a back electrode type solar cell. The first wiring and the second wiring cross the first electrode and the second electrode, the first wiring is connected to the first electrode at a point where it intersects with the first electrode, and is insulated from the second electrode by an insulating layer at a point where it intersects with the second electrode; The second wiring is connected to the second electrode at a point where it intersects with the second electrode, and is insulated from the first electrode by an insulating layer at a point where it intersects with the first electrode; It is stated that:

[0003] In addition, Patent Document 3 describes a back electrode type solar cell as follows: A wiring for a p-electrode and a wiring for an n-electrode intersecting the p-electrode and the n-electrode are provided, -Insulating resin is formed on the back side, the p-electrode wiring is connected to the p-electrode by a conductive member in a hole in the insulating resin at a point where it intersects with the p-electrode, and is insulated from the n-electrode by the insulating resin at a point where it intersects with the n-electrode; The n-electrode wiring is connected to the n-electrode by a conductive member in a hole in the insulating resin at a point where it intersects with the n-electrode, and is insulated from the p-electrode by the insulating resin at a point where it intersects with the p-electrode. It is stated that: [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-133567 A [Patent Document 2] JP 2015-159286 A [Patent Document 3] JP 2014-127550 A Summary of the Invention [Problem to be solved by the invention]

[0005] In order to reduce the cost of such solar cells, the inventor(s) of the present application has devised the use of a relatively inexpensive metal, such as Cu (for example, a film formed by a PVD method such as sputtering, followed by wet etching) as the material for the metal electrode layer, instead of the relatively expensive known Ag paste. Note that a contact electrode made of Ag paste is used only in the portion that makes contact with the wiring member.

[0006] Furthermore, in order to simplify the manufacturing process of such solar cells, the inventors of the present application have devised a method in which the insulating layer and contact electrode (Ag paste) for ensuring insulation and contact with the wiring members also serve as a resist for wet etching of the metal electrode layer (e.g., Cu) and transparent electrode layer.

[0007] However, according to the findings of the present inventors, in such solar cells and their manufacturing methods, when the metal electrode layer and the transparent electrode layer are annealed (heated) after wet etching, the metal components of the metal electrode layer, such as Cu, diffuse into the semiconductor substrate, resulting in a decrease in the performance of the solar cell.

[0008] An object of the present invention is to provide a solar cell and a manufacturing method thereof that can suppress deterioration in solar cell performance while simplifying the manufacturing process and reducing the cost of the solar cell. [Means for solving the problem]

[0009] A method for manufacturing a solar cell according to the present invention is a method for manufacturing a back electrode type solar cell including a semiconductor substrate, a first conductive type semiconductor layer, a first transparent electrode layer, and a first metal electrode layer which are laminated in this order in a first region which is a part of one main surface side of the semiconductor substrate, and a second conductive type semiconductor layer, a second transparent electrode layer, and a second metal electrode layer which are laminated in this order in a second region which is another part of the one main surface side of the semiconductor substrate, the method including the steps of: a transparent electrode layer material film forming step of forming a series of transparent electrode layer material films on the first conductive type semiconductor layer and the second conductive type semiconductor layer on the one main surface side of the semiconductor substrate; a metal electrode layer material film forming step of forming a series of metal electrode layer material films on the transparent electrode layer material film; a conductive protection layer material film forming step of forming a series of conductive protection layer material films on the metal electrode layer material film; a first insulating layer entirely covering the conductive protection layer material film in the second region except for a second non-insulating region, and a second insulating layer entirely covering the conductive protection layer material film in the second region except for a second non-insulating region, wherein the first insulating layer and the second insulating layer are spaced apart from each other; a contact electrode forming step of forming contact electrodes in the first non-insulating region and the second non-insulating region; and a transparent electrode layer and metal electrode layer forming step of forming a patterned first transparent electrode layer, the first metal electrode layer, and a first conductive protection layer, and a patterned second transparent electrode layer, the second metal electrode layer, and a second conductive protection layer by removing exposed portions of the material film of the conductive protection layer, and the material film of the metal electrode layer and the material film of the transparent electrode layer corresponding to the exposed portions, using an etching method that uses the first insulating layer, the second insulating layer, and the contact electrode as a mask. In the contact electrode formation process, the contact electrode is formed by printing and curing or drying a printing material containing a particulate metal material and a resin material, and in the transparent electrode layer and metal electrode layer formation process, the material film of the conductive protection layer protects the metal electrode layer, the transparent electrode layer, the semiconductor layer and the semiconductor substrate from an etching solution that penetrates through the contact electrode.

[0010] The solar cell of the present invention is a back electrode type solar cell comprising a semiconductor substrate, a first conductive type semiconductor layer, a first transparent electrode layer and a first metal electrode layer which are stacked in sequence in a first region which is a part of one main surface side of the semiconductor substrate, and a second conductive type semiconductor layer, a second transparent electrode layer and a second metal electrode layer which are stacked in sequence in a second region which is the other part of the one main surface side of the semiconductor substrate, and the solar cell comprises a first conductive protective layer formed on the first metal electrode layer, a second conductive protective layer formed on the second metal electrode layer, a first insulating layer which entirely covers the first conductive protective layer except for a first non-insulating region, a second insulating layer which entirely covers the second conductive protective layer except for a second non-insulating region, and contact electrodes formed in the first non-insulating region and the second non-insulating region, the contact electrodes being formed by printing and curing a printing material containing a particulate metal material and a resin material. Effect of the Invention

[0011] According to the present invention, even if the manufacturing process is simplified and the cost of the solar cell is reduced, the deterioration of the performance of the solar cell can be suppressed. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a diagram showing the solar cell according to the embodiment as viewed from the back surface side. [Figure 2A] 2 is a cross-sectional view taken along line IIA-IIA of the solar cell of FIG. 1. [Figure 2B] 2 is a cross-sectional view of the solar cell shown in FIG. 1 taken along line IIB-IIB. [Figure 3A] 3A to 3C are diagrams illustrating a semiconductor layer forming step in the method for manufacturing a solar cell according to the present embodiment. [Figure 3B] 1A to 1C are diagrams showing electrode layer material film forming steps in the manufacturing method for a solar cell according to the present embodiment, that is, a transparent electrode layer material film forming step, a metal electrode layer material film forming step, and a conductive protective layer material film forming step. [Figure 3C] 3A to 3C are diagrams illustrating an insulating layer forming step in the method for manufacturing a solar cell according to the present embodiment. [Figure 3D]5A to 5C are diagrams illustrating a contact electrode forming step in the manufacturing method for the solar cell according to the embodiment. [Figure 3E] 2A to 2C are diagrams illustrating electrode layer forming steps in the method for manufacturing a solar cell according to the present embodiment, that is, a transparent electrode layer forming step, a metal electrode layer forming step, and a conductive protective layer forming step. [Figure 4A] 2 is a cross-sectional view of a solar cell of a comparative example, taken along line IIA-IIA in FIG. 1. [Figure 4B] 2 is a cross-sectional view of a solar cell of a comparative example, taken along line IIB-IIB in FIG. 1. [Figure 5A] 5A to 5C are diagrams illustrating a semiconductor layer forming step in a solar cell manufacturing method according to a comparative example. [Figure 5B] 1A to 1C are diagrams showing an electrode layer material film forming step, that is, a transparent electrode layer material film forming step and a metal electrode layer material film forming step, in a manufacturing method for a solar cell of a comparative example. [Figure 5C] 1A to 1C are diagrams illustrating an insulating layer forming step in a solar cell manufacturing method according to a comparative example. [Figure 5D] 11A to 11C are diagrams illustrating a contact electrode forming step in a solar cell manufacturing method according to a comparative example. [Figure 5E] 4A to 4C are diagrams illustrating electrode layer forming steps, that is, a transparent electrode layer forming step and a metal electrode layer forming step, in a solar cell manufacturing method of a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals. For convenience, hatching and reference numerals may be omitted, in which case other drawings shall be referred to.

[0014] (Solar Cell of the Present Embodiment) Fig. 1 is a view of the solar cell according to this embodiment as viewed from the back surface side. Fig. 2A is a cross-sectional view of the solar cell in Fig. 1 taken along line IIA-IIA, and Fig. 2B is a cross-sectional view of the solar cell in Fig. 1 taken along line IIB-IIB. The solar cell 1 shown in Figs. 1, 2A, and 2B is a back electrode type (also called back contact type or back junction type) heterojunction solar cell.

[0015] Solar cell 1 includes a semiconductor substrate 11 with two main surfaces, and the main surface of semiconductor substrate 11 has a first region 7 and a second region 8. In the following, the main surface of semiconductor substrate 11 that receives light is referred to as the light-receiving surface, and the main surface of semiconductor substrate 11 opposite the light-receiving surface (one main surface) is referred to as the back surface.

[0016] The first regions 7 are strip-shaped and extend in the Y direction (second direction). Similarly, the second regions 8 are strip-shaped and extend in the Y direction. The first regions 7 and the second regions 8 are alternately provided in the X direction (first direction) that intersects with the Y direction.

[0017] The solar cell 1 includes a passivation layer 13 and an optical adjustment layer 15, which are laminated in this order on the light-receiving surface side of the semiconductor substrate 11. The solar cell 1 also includes a passivation layer 23, a first conductive type semiconductor layer 25, a first electrode layer 27, and a first insulating layer 41, which are laminated in this order on a portion (first region 7) of the back surface side of the semiconductor substrate 11. The solar cell 1 also includes a passivation layer 33, a second conductive type semiconductor layer 35, a second electrode layer 37, and a second insulating layer 42, which are laminated in this order on another portion (second region 8) of the back surface side of the semiconductor substrate 11. The solar cell 1 also includes a first contact electrode 51 corresponding to the first electrode layer 27, and a second contact electrode 52 corresponding to the second electrode layer 37.

[0018] The semiconductor substrate 11 is formed of a crystalline silicon material such as single crystal silicon or polycrystalline silicon. The semiconductor substrate 11 is, for example, an n-type semiconductor substrate in which a crystalline silicon material is doped with an n-type dopant. The semiconductor substrate 11 may be, for example, a p-type semiconductor substrate in which a crystalline silicon material is doped with a p-type dopant. An example of the n-type dopant is phosphorus (P). An example of the p-type dopant is boron (B). The semiconductor substrate 11 functions as a photoelectric conversion substrate that absorbs incident light from the light-receiving surface side and generates photocarriers (electrons and holes).

[0019] By using crystalline silicon as the material for the semiconductor substrate 11, the dark current is relatively small, and a relatively high output (stable output regardless of illuminance) can be obtained even when the intensity of incident light is low.

[0020] The passivation layer 13 is formed on the light-receiving surface side of the semiconductor substrate 11. The passivation layer 23 is formed in a first region 7 on the back surface side of the semiconductor substrate 11. The passivation layer 33 is formed in a second region 8 on the back surface side of the semiconductor substrate 11. The passivation layers 13, 23, and 33 are formed of a material containing, for example, an intrinsic (i-type) amorphous silicon material as a main component. The passivation layers 13, 23, and 33 suppress recombination of carriers generated in the semiconductor substrate 11 and increase the carrier collection efficiency.

[0021] The optical adjustment layer 15 is formed on the passivation layer 13 on the light-receiving surface side of the semiconductor substrate 11. The optical adjustment layer 15 functions as an anti-reflection layer that prevents reflection of incident light, and also functions as a protective layer that protects the light-receiving surface side of the semiconductor substrate 11 and the passivation layer 13. The optical adjustment layer 15 is formed of an insulating material, for example, silicon oxide (SiO), silicon nitride (SiN), or a composite thereof such as silicon oxynitride (SiON).

[0022] The first conductive type semiconductor layer 25 is formed on the passivation layer 23, that is, in a first region 7 on the back surface side of the semiconductor substrate 11. On the other hand, the second conductive type semiconductor layer 35 is formed on the passivation layer 33, that is, in a second region 8 on the back surface side of the semiconductor substrate 11. That is, the first conductive type semiconductor layer 25 and the second conductive type semiconductor layer 35 have a strip shape and extend in the Y direction. The first conductive type semiconductor layer 25 and the second conductive type semiconductor layer 35 are alternately arranged in the X direction. A part of the second conductive type semiconductor layer 35 may overlap a part of the adjacent first conductive type semiconductor layer 25 (not shown).

[0023] The first conductive type semiconductor layer 25 is formed of, for example, an amorphous silicon material. The first conductive type semiconductor layer 25 is, for example, a p-type semiconductor layer in which an amorphous silicon material is doped with a p-type dopant (for example, the above-mentioned boron (B)).

[0024] The second conductive type semiconductor layer 35 is formed of, for example, an amorphous silicon material. The second conductive type semiconductor layer 35 is, for example, an n-type semiconductor layer in which an amorphous silicon material is doped with an n-type dopant (for example, the above-mentioned phosphorus (P)). Note that the first conductive type semiconductor layer 25 may be an n-type semiconductor layer, and the second conductive type semiconductor layer 35 may be a p-type semiconductor layer.

[0025] The first electrode layer 27 is formed on the first conductive type semiconductor layer 25, i.e., in a first region 7 on the back surface side of the semiconductor substrate 11. On the other hand, the second electrode layer 37 is formed on the second conductive type semiconductor layer 35, i.e., in a second region 8 on the back surface side of the semiconductor substrate 11. That is, the first electrode layer 27 and the second electrode layer 37 have a strip-like shape and extend in the Y direction. The first electrode layer 27 and the second electrode layer 37 are alternately provided in the X direction.

[0026] The first electrode layer 27 has a first transparent electrode layer 28, a first metal electrode layer 29, and a first conductive protection layer 27P, which are laminated in this order on the first conductive type semiconductor layer 25. On the other hand, the second electrode layer 37 has a second transparent electrode layer 38, a second metal electrode layer 39, and a second conductive protection layer 37P, which are laminated in this order on the second conductive type semiconductor layer 35.

[0027] The first transparent electrode layer 28 and the second transparent electrode layer 38 are formed of a transparent conductive material. Examples of the transparent conductive material include ITO (Indium Tin Oxide: a composite oxide of indium oxide and tin oxide), ZnO (Zinc Oxide: zinc oxide), etc.

[0028] The first metal electrode layer 29 and the second metal electrode layer 39 are formed of a metal material. The metal material used is a material that is less expensive than known conductive paste materials containing Ag powder, such as Cu or Al.

[0029] The first conductive protective layer 27P and the second conductive protective layer 37P are formed of a transparent conductive material, similar to the first transparent electrode layer 28 and the second transparent electrode layer 38 described above. The first conductive protective layer 27P functions to protect the metal electrode layer 29 from printing damage when the contact electrodes 51 and 52 are printed. The first conductive protective layer 27P also functions to protect the first metal electrode layer 29, the first transparent electrode layer 28, the semiconductor layers 25 and 23, and the semiconductor substrate 11 from the etching solution when the metal electrode layers 29 and 39 and the transparent electrode layers 28 and 38 are simultaneously etched and annealed (heated). Similarly, the second conductive protective layer 37P functions to protect the metal electrode layer 39 from printing damage when the contact electrodes 51 and 52 are printed. In addition, the second conductive protective layer 37P functions to protect the second metal electrode layer 39, the second transparent electrode layer 38, the semiconductor layers 35 and 33, and the semiconductor substrate 11 from the etching solution during simultaneous etching and annealing (heating) of the metal electrode layers 29 and 39 and the transparent electrode layers 28 and 38. The details of these functions will be described later.

[0030] In order to realize these functions, it is preferable that the first transparent electrode layer 28 and the second transparent electrode layer 38 are amorphous (non-crystalline) transparent conductive films, and the first conductive protection layer 27P and the second conductive protection layer 37P are crystalline transparent conductive films. In a crystalline transparent conductive film, when a cross section is observed, for example, by a TEM, a larger area is occupied by crystal grains in the film compared to an amorphous transparent conductive film. Therefore, the etching rate (speed) of a crystalline transparent conductive film is lower (slower) than that of an amorphous transparent conductive film.

[0031] The first insulating layer 41 is formed on the first electrode layer 27, i.e., in a first region 7 on the back surface side of the semiconductor substrate 11. The second insulating layer 42 is formed on the second electrode layer 37, i.e., in a second region 8 on the back surface side of the semiconductor substrate 11. That is, the first insulating layer 41 and the second insulating layer 42 have a band-like shape and extend in the Y direction, as shown in Fig. 1. The first insulating layer 41 and the second insulating layer 42 are provided alternately in the X direction.

[0032] The first insulating layer 41 entirely covers the first electrode layer 27 except for a first non-insulating region 41a. Similarly, the second insulating layer 42 entirely covers the second electrode layer 37 except for a second non-insulating region 42a.

[0033] The first non-insulating region 41a is not covered with the first insulating layer 41 and is formed by an opening exposing the first electrode layer 27. The first non-insulating region 41a is disposed on a first straight line X1 extending in the X direction (first direction). Similarly, the second non-insulating region 42a is not covered with the second insulating layer 42 and is formed by an opening exposing the second electrode layer 37. The second non-insulating region 42a is disposed on a second straight line X2 different from the first straight line X1 extending in the X direction (first direction). The first straight line X1 and the second straight line X2 intersect the first electrode layer 27 and the second electrode layer 37 and are arranged alternately in the Y direction (second direction).

[0034] Examples of materials for the first insulating layer 41 and the second insulating layer 42 include silicon oxide (SiO), silicon nitride (SiN), and compounds thereof such as silicon oxynitride (SiON). Thermosetting resins such as epoxy resins or resin esters that can be applied by screen printing and baked can also be used. Inorganic particles such as silica or talc may be mixed into these resins to improve printability or chemical resistance.

[0035] A first contact electrode 51 is formed in the first non-insulating region 41a of the first insulating layer 41, and a second contact electrode 52 is formed in the second non-insulating region 42a of the second insulating layer 42. That is, the first contact electrode 51 is formed on the first electrode layer 27 and arranged on a first straight line X1. On the other hand, the second contact electrode 52 is formed on the second electrode layer 37 and arranged on a second straight line X2.

[0036] The first contact electrode 51 and the second contact electrode 52 are formed by printing and curing a printing material containing particulate metal material such as Cu, Ag, Al, or the like and a resin material, or a printing material containing a solvent in addition to the metal material and the resin material. Among these, the Ag paste material is preferable as the printing material from the viewpoint of contact with the solder for connection to the wiring member.

[0037] The width in the Y direction (second direction) of the first non-insulating region 41a of the first insulating layer 41, i.e., the width in the Y direction (second direction) of the first contact electrode 51, is greater than the width of the first wiring member 91. Similarly, the width in the Y direction (second direction) of the second non-insulating region 42a, i.e., the width in the Y direction (second direction) of the second contact electrode 52, is greater than the width of the second wiring member 92. For example, the widths of the first non-insulating region 41a and the second non-insulating region 42a, i.e., the widths of the first contact electrode 51 and the second contact electrode 52, are 1 mm or more and 50 mm or less. This makes it possible to ensure alignment clearance when connecting the wiring members.

[0038] 1, 2A, and 2B, the first electrode layer 27 and the second electrode layer 37 are separated at the boundary between the first region 7 and the second region 8. That is, the first transparent electrode layer 28 and the second transparent electrode layer 38 are separated, the first metal electrode layer 29 and the second metal electrode layer 39 are separated, and the first conductive protection layer 27P and the second conductive protection layer 37P are separated. In addition, the first insulating layer 41 and the second insulating layer 42 are separated.

[0039] The area between the first transparent electrode layer 28 and the second transparent electrode layer 38, i.e., the area between the first metal electrode layer 29 and the second metal electrode layer 39, in other words, the area between the first conductive protective layer 27P and the second conductive protective layer 37P, is not covered with the first insulating layer 41 and the second insulating layer 42.

[0040] The main surface of the first conductive protection layer 27P opposite to the main surface in contact with the first metal electrode layer 29 is covered with a first insulating layer 41. Similarly, the main surface of the second conductive protection layer 37P opposite to the main surface in contact with the second metal electrode layer 39 is covered with a second insulating layer 42. On the other hand, the side surfaces of the first conductive protection layer 27P are not covered with the first insulating layer 41. Similarly, the side surfaces of the second conductive protection layer 37P are not covered with the second insulating layer 42.

[0041] In addition, the side surfaces of the first metal electrode layer 29 and the first transparent electrode layer 28 are not covered with the first insulating layer 41. Similarly, the side surfaces of the second metal electrode layer 39 and the second transparent electrode layer 38 are not covered with the second insulating layer 42.

[0042] 1, the first wiring member 91 extends in the X direction (first direction) along a first straight line X1. Similarly, the second wiring member 92 extends in the X direction (first direction) along a second straight line X2. That is, the first wiring member 91 and the second wiring member 92 intersect the first electrode layer 27 and the second electrode layer 37, and are alternately arranged in the Y direction (second direction).

[0043] The first wiring member 91 is electrically connected to the first electrode layer 27 by a first contact electrode 51 in the first non-insulating region 41a of the first insulating layer 41, and is electrically insulated from the second electrode layer 37 by the second insulating layer 42. Similarly, the second wiring member 92 is electrically connected to the second electrode layer 37 by a second contact electrode 52 in the second non-insulating region 42a of the second insulating layer 42, and is electrically insulated from the first electrode layer 27 by the first insulating layer 41.

[0044] The center-to-center distance (pitch) in the Y direction between the first wiring member 91 and the second wiring member 92 is greater than the center-to-center distance (pitch) in the X direction between the first electrode layer 27 and the second electrode layer 37. For example, the center-to-center distance (pitch) between the first wiring member 91 and the second wiring member 92 is 5 mm or more and 50 mm or less. This makes it possible to shorten the current path flowing through the electrode layers, reduce output loss caused by electrode resistance, and improve the power generation efficiency of the solar cell.

[0045] The first wiring member 91 and the second wiring member 92 may be a known tab wire or the like.

[0046] Here, in order to reduce the cost of such solar cells, the inventor(s) of the present application have devised the use of a relatively inexpensive metal, for example, Cu (for example, a film formed by a PVD method such as sputtering, followed by wet etching) instead of the relatively expensive known Ag paste as the material for the metal electrode layers 29, 39. Note that contact electrodes 51, 52 made of Ag paste are used only in the portions that make contact with the wiring members 91, 92.

[0047] Furthermore, for the purpose of simplifying the manufacturing process of such a solar cell, the inventor(s) have devised a method of using the insulating layers 41, 42 and the contact electrodes 51, 52 (Ag paste) for ensuring insulation and contact with the wiring members 91, 92 also as resists for wet etching of the metal electrode layers 29, 39 (e.g., Cu) and the transparent electrode layers 28, 38. Below, such a solar cell devised by the inventor(s) and a manufacturing method thereof will be described as a comparative example.

[0048] (Solar cell of comparative example) Fig. 4A is a cross-sectional view of a solar cell of a comparative example, taken along line IIA-IIA in Fig. 1, and Fig. 4B is a cross-sectional view of a solar cell of a comparative example, taken along line IIB-IIB in Fig. 1. Solar cell 1X of the comparative example shown in Figs. 4A and 4B differs from the solar cell 1 shown in Figs. 2A and 2B in that the first electrode layer 27X does not include the first conductive protective layer 27P and the second electrode layer 37X does not include the second conductive protective layer 37P.

[0049] (Comparative Example of Solar Cell Manufacturing Method) Hereinafter, a method for manufacturing a solar cell of a comparative example will be described with reference to Figs. 5A to 5E. Fig. 5A is a diagram showing a semiconductor layer forming step in the method for manufacturing a solar cell of a comparative example, and Fig. 5B is a diagram showing an electrode layer material film forming step, i.e., a transparent electrode layer material film forming step and a metal electrode layer material film forming step, in the method for manufacturing a solar cell of a comparative example. Fig. 5C is a diagram showing an insulating layer forming step in the method for manufacturing a solar cell of a comparative example, and Fig. 5D is a diagram showing a contact electrode forming step in the method for manufacturing a solar cell of a comparative example. Fig. 5E is a diagram showing an electrode layer forming step, i.e., a transparent electrode layer forming step and a metal electrode layer forming step, in the method for manufacturing a solar cell of a comparative example. Figs. 5A to 5E show the back side of a semiconductor substrate 11, and the front side of the semiconductor substrate 11 is omitted.

[0050] 5A, a passivation layer 23 and a first conductive type semiconductor layer 25 are formed on a part of the back surface side of the semiconductor substrate 11, specifically, on the first region 7 (semiconductor layer formation step). For example, after a passivation layer material film and a first conductive type semiconductor layer material film are formed on the entire back surface side of the semiconductor substrate 11 using a CVD method or a PVD method, the passivation layer 23 and the first conductive type semiconductor layer 25 may be patterned using an etching method that uses a resist generated using a photolithography technique or a printing technique, or a metal mask.

[0051] Next, a passivation layer 33 and a second conductive type semiconductor layer 35 are formed on another part of the back surface side of the semiconductor substrate 11, specifically, on the second region 8 (semiconductor layer formation step). For example, as described above, a passivation layer material film and a second conductive type semiconductor layer material film may be formed on the entire back surface side of the semiconductor substrate 11 using a CVD method or a PVD method, and then the passivation layer 33 and the second conductive type semiconductor layer 35 may be patterned using an etching method that uses a resist generated using a photolithography technique or a printing technique, or a metal mask.

[0052] 5B, a series of transparent electrode layer material films 28Z are formed on and across the first conductive type semiconductor layer 25 and the second conductive type semiconductor layer 35 (transparent electrode layer material film forming process). The transparent electrode layer material film 28Z is formed by, for example, a CVD method or a PVD method.

[0053] Next, a series of metal electrode layer material films 29Z (e.g., Cu) is formed on the transparent electrode layer material film 28Z, i.e., across the first conductive type semiconductor layer 25 and the second conductive type semiconductor layer 35 (metal electrode layer material film formation process). The metal electrode layer material film 29Z is formed by, for example, a PVD method such as sputtering.

[0054] 5C, a first insulating layer 41 is formed on the first conductive type semiconductor layer 25 via the transparent electrode layer material film 28Z and the metal electrode layer material film 29Z, i.e., in the first region 7, except for the first non-insulating region 41a. Also, a second insulating layer 42 is formed on the second conductive type semiconductor layer 35 via the transparent electrode layer material film 28Z and the metal electrode layer material film 29Z, i.e., in the second region 8, except for the second non-insulating region 42a (insulating layer forming step). Note that the first insulating layer 41 and the second insulating layer 42 are formed to be spaced apart from each other.

[0055] Methods for forming the first insulating layer 41 and the second insulating layer 42 include a PVD method, a CVD method, a screen printing method, an inkjet method, a gravure coating method, a dispenser method, and the like.

[0056] Next, as shown in FIG. 5D, a first contact electrode 51 is formed in the first non-insulating region 41a of the first insulating layer 41, and a second contact electrode 52 is formed in the second non-insulating region 42a of the second insulating layer 42 (contact electrode forming process). Examples of a method for forming the first contact electrode 51 and the second contact electrode 52 include printing methods such as screen printing. For example, the first contact electrode 51 and the second contact electrode 52 are formed by printing and curing or drying a printing material containing Ag particles and a resin material, or a printing material containing a solvent in addition to Ag particles and a resin material, that is, an Ag paste material. Note that drying refers to a state in which the material is not completely cured at a temperature lower than the curing temperature and for a time shorter than the curing time.

[0057] Next, as shown in FIG. 5E, the metal electrode layer material film 29Z and the transparent electrode layer material film 28Z are patterned by using a wet etching method with the first insulating layer 41 and the first contact electrode 51, and the second insulating layer 42 and the second contact electrode 52 as masks, to form the first transparent electrode layer 28 and the second transparent electrode layer 38, which are separated from each other, and the first metal electrode layer 29 and the second metal electrode layer 39, which are separated from each other (transparent electrode layer forming step and metal electrode layer forming step). As a result, the first electrode layer 27X and the second electrode layer 37X are formed. At this time, the first insulating layer 41 and the second insulating layer 42 are left without being removed. Thereafter, annealing (heating) is performed to obtain the solar cell 1X of the comparative example.

[0058] An example of an etching solution for simultaneous etching of the metal electrode layer material film 29Z and the transparent electrode layer material film 28Z is a mixed solution of an oxidizing agent such as ammonium persulfate and an acidic solution such as hydrochloric acid (HCl).

[0059] Next, both sides of the semiconductor substrate 11 are cleaned (cleaning process). In the cleaning process, for example, ozone treatment is performed, followed by hydrofluoric acid treatment (treatment with hydrofluoric acid or a mixture of hydrofluoric acid and another type of acid).

[0060] According to the knowledge of the present inventor(s), the manufacturing method of this comparative example solar cell 1X sometimes caused localized physical damage to semiconductor substrate 11 below first contact electrode 51 and second contact electrode 52. This can be considered as follows.

[0061] During screen printing of, for example, Ag paste in the contact electrode forming step, local physical damage occurs in the metal electrode layer material film 29Z made of, for example, Cu. Then, during wet etching in the transparent electrode layer forming step and the metal electrode layer forming step, the etching solution that has penetrated into the contact electrodes 51, 52 made of Ag paste penetrates into the damaged parts of the metal electrode layers 29, 39 made of Cu during annealing (heating), locally dissolves the transparent electrode layers 28, 38, and penetrates into the damaged parts of the semiconductor layers 25, 23, 35, 33. Then, the metal components of the metal electrode layers 29, 39, for example, Cu, diffuse into the semiconductor substrate 11. This may cause a decrease in the performance of the solar cell 1X.

[0062] Furthermore, during wet etching in the transparent electrode layer forming process and the metal electrode layer forming process, the etching solution that has penetrated into the contact electrodes 51, 52 made of Ag paste etches the metal electrode layers 29, 39 made of Cu during annealing (heating), generating Cu ions. During annealing, these Cu ions migrate, for example, via the surfaces of the metal electrode layers 29, 39 and diffuse into the semiconductor substrate 11. This may result in a decrease in the performance of the solar cell 1X.

[0063] In this regard, in order to improve resistance to printing damage in the contact electrode formation process and resistance to etching solutions and annealing (heating) in the transparent electrode layer formation process and the metal electrode layer formation process, the present inventor(s) devised providing a first conductive protection layer 27P on the first electrode layer 27 and a second conductive protection layer 37P on the second electrode layer 37.

[0064] (Method of manufacturing solar cell according to the present embodiment) Hereinafter, the method for manufacturing a solar cell according to the present embodiment will be described with reference to Figs. 3A to 3E. Fig. 3A is a diagram showing a semiconductor layer forming step in the method for manufacturing a solar cell according to the present embodiment, and Fig. 3B is a diagram showing an electrode layer material film forming step, i.e., a transparent electrode layer material film forming step, a metal electrode layer material film forming step, and a conductive protection layer material film forming step, in the method for manufacturing a solar cell according to the present embodiment. Fig. 3C is a diagram showing an insulating layer forming step in the method for manufacturing a solar cell according to the present embodiment, and Fig. 3D is a diagram showing a contact electrode forming step in the method for manufacturing a solar cell according to the present embodiment. Fig. 3E is a diagram showing an electrode layer forming step, i.e., a transparent electrode layer forming step, a metal electrode layer forming step, and a conductive protection layer forming step, in the method for manufacturing a solar cell according to the present embodiment. Figs. 3A to 3E show the back side of the semiconductor substrate 11, and the front side of the semiconductor substrate 11 is omitted.

[0065] 3A, a passivation layer 23 and a first conductive type semiconductor layer 25 are formed on a part of the back surface side of the semiconductor substrate 11, specifically, on the first region 7 (semiconductor layer formation step). For example, after a passivation layer material film and a first conductive type semiconductor layer material film are formed on the entire back surface side of the semiconductor substrate 11 using a CVD method or a PVD method, the passivation layer 23 and the first conductive type semiconductor layer 25 may be patterned using an etching method that uses a resist generated using a photolithography technique or a printing technique, or a metal mask.

[0066] In addition, examples of the etching solution for the p-type semiconductor layer material film include an acidic solution such as hydrofluoric acid containing ozone or a mixture of nitric acid and hydrofluoric acid, and examples of the etching solution for the n-type semiconductor layer material film include an alkaline solution such as an aqueous solution of potassium hydroxide.

[0067] Alternatively, when a passivation layer and a first conductive type semiconductor layer are laminated on the back side of the semiconductor substrate 11 using a CVD method or a PVD method, the passivation layer 23 and the first conductive type semiconductor layer 25 may be deposited and patterned simultaneously using a mask.

[0068] Next, a passivation layer 33 and a second conductive type semiconductor layer 35 are formed on another part of the back surface side of the semiconductor substrate 11, specifically, on the second region 8 (semiconductor layer formation step). For example, as described above, a passivation layer material film and a second conductive type semiconductor layer material film may be formed on the entire back surface side of the semiconductor substrate 11 using a CVD method or a PVD method, and then the passivation layer 33 and the second conductive type semiconductor layer 35 may be patterned using an etching method that uses a resist generated using a photolithography technique or a printing technique, or a metal mask.

[0069] Alternatively, when a passivation layer and a second conductive type semiconductor layer are laminated on the back surface side of the semiconductor substrate 11 using a CVD method or a PVD method, the passivation layer 33 and the second conductive type semiconductor layer 35 may be deposited and patterned simultaneously using a mask.

[0070] In this semiconductor layer forming step, a passivation layer 13 (not shown) may be formed on the entire light-receiving surface side of the semiconductor substrate 11.

[0071] 3B, a series of transparent electrode layer material films 28Z are formed on and across the first conductive type semiconductor layer 25 and the second conductive type semiconductor layer 35 (transparent electrode layer material film forming process). The transparent electrode layer material film 28Z can be formed by, for example, a CVD method or a PVD method.

[0072] Next, a series of metal electrode layer material films 29Z (e.g., Cu) is formed on the transparent electrode layer material film 28Z, i.e., across the first conductive type semiconductor layer 25 and the second conductive type semiconductor layer 35 (metal electrode layer material film formation process). The metal electrode layer material film 29Z is formed by, for example, a PVD method such as sputtering.

[0073] Next, a series of conductive protective layer material films 27PZ are formed on the metal electrode layer material film 29Z, i.e., across the first conductive type semiconductor layer 25 and the second conductive type semiconductor layer 35 (conductive protective layer material film forming process). As a method for forming the conductive protective layer material film 27PZ, for example, a CVD method or a PVD method is used, as in the case of the transparent electrode layer material film 28Z described above.

[0074] 3C, a first insulating layer 41 is formed on the first conductive type semiconductor layer 25, i.e., in the first region 7, except for the first non-insulating region 41a, via the transparent electrode layer material film 28Z, the metal electrode layer material film 29Z, and the conductive protective layer material film 27PZ. A second insulating layer 42 is formed on the second conductive type semiconductor layer 35, i.e., in the second region 8, except for the second non-insulating region 42a, via the transparent electrode layer material film 28Z and the metal electrode layer material film 29Z (insulating layer forming step). The first insulating layer 41 and the second insulating layer 42 are formed to be spaced apart from each other.

[0075] Methods for forming the first insulating layer 41 and the second insulating layer 42 include a PVD method, a CVD method, a screen printing method, an inkjet method, a gravure coating method, a dispenser method, and the like.

[0076] Next, as shown in FIG. 3D, a first contact electrode 51 is formed in the first non-insulating region 41a of the first insulating layer 41, and a second contact electrode 52 is formed in the second non-insulating region 42a of the second insulating layer 42 (contact electrode forming process). Examples of a method for forming the first contact electrode 51 and the second contact electrode 52 include printing methods such as screen printing. For example, the first contact electrode 51 and the second contact electrode 52 are formed by printing and curing or drying a printing material containing Ag particles and a resin material, or a printing material containing Ag particles and a resin material as well as a solvent, i.e., an Ag paste material. As described above, drying refers to a state in which the material is not completely cured at a temperature lower than the curing temperature and for a time shorter than the curing time.

[0077] At this time, that is, during screen printing of, for example, Ag paste, the conductive protective layer material film 27PZ protects the metal electrode layer material film 29Z made of, for example, Cu, and suppresses localized physical damage to the metal electrode layer material film 29Z.

[0078] Next, as shown in FIG. 3E, the conductive protection layer material film 27PZ is patterned using a wet etching method using the first insulating layer 41 and the first contact electrode 51, and the second insulating layer 42 and the second contact electrode 52 as masks, to form a first conductive protection layer 27P and a second conductive protection layer 37P that are separated from each other (electrode layer formation process).

[0079] An example of an etching solution for the conductive protective layer material film 27PZ is an acidic solution such as hydrochloric acid (HCl).

[0080] Next, the metal electrode layer material film 29Z and the transparent electrode layer material film 28Z are patterned by using a wet etching method with the first insulating layer 41 and the first contact electrode 51, and the second insulating layer 42 and the second contact electrode 52 as masks, to form the first transparent electrode layer 28 and the second transparent electrode layer 38, which are separated from each other, and the first metal electrode layer 29 and the second metal electrode layer 39, which are separated from each other (electrode layer forming step). As a result, the first electrode layer 27 and the second electrode layer 37 are formed. At this time, the first insulating layer 41 and the second insulating layer 42 are left without being removed.

[0081] An example of an etching solution for simultaneous etching of the metal electrode layer material film 29Z and the transparent electrode layer material film 28Z is a mixed solution of an oxidizing agent such as ammonium persulfate and an acidic solution such as hydrochloric acid (HCl).

[0082] Next, both sides of the semiconductor substrate 11 are cleaned (cleaning process). In the cleaning process, for example, ozone treatment is performed, followed by hydrofluoric acid treatment (treatment with hydrofluoric acid or a mixture of hydrofluoric acid and another type of acid).

[0083] Thereafter, an optical adjustment layer 15 (not shown) is formed on the entire light-receiving surface side of the semiconductor substrate 11. If the printing material is dried in the contact electrode formation step described above, the printing material may be cured. Then, annealing (heating) is performed to obtain the back electrode type solar cell 1 of this embodiment shown in Figures 1 and 2.

[0084] Here, during wet etching in the transparent electrode layer forming process and the metal electrode layer forming process, the etching solution penetrates into the contact electrodes 51, 52 made of Ag paste. However, as described above, local physical damage to the metal electrode layer material film 29Z is suppressed. Therefore, during annealing (heating), the etching solution that penetrated into the contact electrodes 51, 52 is suppressed from penetrating into the metal electrode layers 29, 39 made of Cu, the transparent electrode layers 28, 38, and the semiconductor layers 25, 23, 35, 33, and the metal components of the metal electrode layers 29, 39, such as Cu, are suppressed from diffusing into the semiconductor substrate 11. It is believed that this suppresses the deterioration of the performance of the solar cell 1.

[0085] Furthermore, the etching solution that has penetrated into the contact electrodes 51, 52 can be retained in the contact electrodes 51, 52 for a long time until the subsequent cleaning process. Therefore, in order to prevent the etching solution from penetrating into the layers below the contact electrodes 51, 52, it is preferable that the etching rate of the first conductive protection layer 27P and the second conductive protection layer 37P with respect to the etching solution is low. This can further prevent the etching solution from penetrating into the metal electrode layers 29, 39 and the transparent electrode layers 28, 38, and a solar cell with higher performance can be obtained.

[0086] On the other hand, from the viewpoint of improving the pattern formation accuracy of the metal electrode layers 29, 39 and the transparent electrode layers 28, 38, it is preferable that the etching rate of the transparent electrode layers 28, 38 is high. By providing the first conductive protection layer 27P and the second conductive protection layer 37P, penetration of the etching solution into the transparent electrode layers 28, 38 via the metal electrode layers 29, 39 is suppressed, so that even if the etching rate of the transparent electrode layers 28, 38 in the etching solution is increased, it is possible to manufacture high-performance solar cells with good productivity.

[0087] Regarding these points, in this embodiment, when the first transparent electrode layer 28 and the second transparent electrode layer 38 are amorphous (non-crystalline) transparent conductive films and the first conductive protection layer 27P and the second conductive protection layer 37P are crystalline transparent conductive films, the etching rate (speed) of the crystalline transparent conductive film is lower (slower) than the etching rate (speed) of the amorphous transparent conductive film. Therefore, during annealing (heating), the etching solution that has penetrated into the contact electrodes 51, 52 is prevented from penetrating into the metal electrode layers 29, 39 made of Cu, the transparent electrode layers 28, 38, and the semiconductor layers 25, 23, 35, 33, and the metal components of the metal electrode layers 29, 39, such as Cu, are prevented from diffusing into the semiconductor substrate 11. It is believed that this prevents the performance of the solar cell 1 from deteriorating.

[0088] Furthermore, the first conductive protective layer 27P and the second conductive protective layer 37P prevent an etching solution that has penetrated into the contact electrodes 51, 52 made of Ag paste during wet etching in the transparent electrode layer forming step and the metal electrode layer forming step from etching the metal electrode layers 29, 39 made of Cu during annealing (heating), generating Cu ions, which then move, for example, through the surfaces of the metal electrode layers 29, 39 during annealing and diffuse into the semiconductor substrate 11. This is believed to prevent a decrease in the performance of the solar cell 1.

[0089] As described above, according to the method for manufacturing a solar cell of this embodiment, a relatively inexpensive metal, for example, Cu (for example, a film formed by a PVD method such as sputtering, followed by wet etching) is used as the material for the metal electrode layers 29, 39 instead of the relatively expensive known Ag paste. This makes it possible to reduce the cost of the solar cell.

[0090] Furthermore, according to the manufacturing method of the solar cell of this embodiment, the insulating layers 41, 42 and the contact electrodes 51, 52 (Ag paste) for ensuring insulation and contact with the wiring members 91, 92 also serve as resists for wet etching of the metal electrode layers 29, 39 (e.g., Cu) and the transparent electrode layers 28, 38. This makes it possible to eliminate the steps of forming and removing the resists for wet etching of the metal electrode layers 29, 39 and the transparent electrode layers 28, 38, and thus simplifies the manufacturing process of the solar cell.

[0091] Furthermore, according to the manufacturing method of the solar cell of this embodiment, the conductive protective layers 27P, 37P are provided on the transparent electrode layers 28, 38 and the metal electrode layers 29, 39. As a result, the conductive protective layers 27P, 37P protect the metal electrode layers 29, 39 made of, for example, Cu during screen printing of, for example, Ag paste in the contact electrode forming step, and local physical damage to the metal electrode layers 29, 39 made of Cu is suppressed. Therefore, during wet etching in the transparent electrode layer forming step and the metal electrode layer forming step, the etching solution that has penetrated into the contact electrodes 51, 52 made of Ag paste is suppressed from penetrating into the metal electrode layers 29, 39 made of Cu, the transparent electrode layers 28, 38, and the semiconductor layers 25, 23, 35, 33 during annealing (heating), and the metal components of the metal electrode layers 29, 39, such as Cu, are suppressed from diffusing into the semiconductor substrate 11. As a result, the deterioration of the performance of the solar cell 1 can be suppressed.

[0092] In addition, when the first transparent electrode layer 28 and the second transparent electrode layer 38 are amorphous (non-crystalline) transparent conductive films and the first conductive protective layer 27P and the second conductive protective layer 37P are crystalline transparent conductive films, the etching rate (speed) of the crystalline transparent conductive film is lower (slower) than that of the amorphous transparent conductive film. Therefore, the etching solution that has penetrated into the contact electrodes 51 and 52 made of Ag paste during wet etching in the transparent electrode layer forming process and the metal electrode layer forming process is suppressed from penetrating into the metal electrode layers 29 and 39 made of Cu, the transparent electrode layers 28 and 38, and the semiconductor layers 25, 23, 35, and 33 during annealing (heating), and the metal components of the metal electrode layers 29 and 39, such as Cu, are suppressed from diffusing into the semiconductor substrate 11. This can suppress the deterioration of the performance of the solar cell 1.

[0093] Furthermore, the first conductive protective layer 27P and the second conductive protective layer 37P prevent an etching solution that has penetrated into the contact electrodes 51, 52 made of Ag paste during wet etching in the transparent electrode layer forming step and the metal electrode layer forming step from etching the metal electrode layers 29, 39 made of Cu during annealing (heating), generating Cu ions, which then move, for example, through the surfaces of the metal electrode layers 29, 39 during annealing and diffuse into the semiconductor substrate 11. This prevents a decrease in the performance of the solar cell 1.

[0094] Furthermore, in an ITO / Cu / Ag electrode structure like solar cell 1X of the comparative example, the surfaces of metal electrode layers 29, 39 made of Cu are oxidized, and the contact resistance between metal electrode layers 29, 39 and contact electrodes 51, 52 made of Ag paste increases, compared to a conventional ITO / Ag electrode structure. Therefore, in the ITO / Cu / Ag electrode structure of solar cell 1X of the comparative example, the series resistance Rs increases, compared to a conventional ITO / Ag electrode structure.

[0095] On the other hand, in the ITO / Cu / ITO / Ag electrode structure like the solar cell 1 of this embodiment, the conductive protective layers 27P, 37P suppress oxidation of the surfaces of the metal electrode layers 29, 39 made of Cu, and can suppress an increase in the contact resistance between the metal electrode layers 29, 39 and the contact electrodes 51, 52 made of Ag paste. Therefore, in the ITO / Cu / ITO / Ag electrode structure of the solar cell 1, an increase in the series resistance Rs can be suppressed compared to the ITO / Cu / Ag electrode structure of the comparative example, and the series resistance Rs can be kept at the same level as in the conventional ITO / Ag electrode structure.

[0096] Furthermore, in the ITO / Cu / ITO / Ag electrode structure such as the solar cell 1 of this embodiment, the conductive protective layers 27P, 37P suppress oxidation of the surfaces of the metal electrode layers 29, 39 made of Cu, so that, compared to the ITO / Cu / Ag electrode structure of the comparative example, high-temperature heat treatment can be performed and the series resistance Rs can be reduced due to the reduction in the volume resistivity of Cu, thereby improving the performance of the solar cell.

[0097] Furthermore, in an ITO / Cu / ITO / Ag electrode structure such as the solar cell 1 of this embodiment, the conductive protective layers 27P, 37P suppress oxidation of the surfaces of the metal electrode layers 29, 39 made of Cu, and therefore, compared to the ITO / Cu / Ag electrode structure of the comparative example, the adhesion between the metal electrode layers 29, 39 and the contact electrodes 51, 52 made of Ag paste can be improved, and as a result, the reliability of the solar cell can be increased.

[0098] As described above, according to the method for manufacturing a solar cell of the present embodiment, it is possible to suppress deterioration in the performance of the solar cell even while simplifying the manufacturing process and reducing the cost of the solar cell.

[0099] Although the embodiment of the present invention has been described above, the present invention is not limited to the above-mentioned embodiment, and various changes and modifications are possible. For example, in the above-mentioned embodiment, the solar cell 1 using a crystalline silicon material is illustrated, but the present invention is not limited to this. For example, various materials such as gallium arsenide (GaAs) may be used as the material of the solar cell.

[0100] In the above-described embodiment, a heterojunction solar cell 1 is illustrated as shown in Fig. 2. However, the present invention is not limited to this and can be applied to various solar cells such as a homojunction solar cell. EXAMPLES

[0101] The present invention will be specifically described below based on examples, but the present invention is not limited to the following examples.

[0102] Example 1 A back electrode type solar cell of this embodiment shown in Figs. 1 to 2B was fabricated as Example 1 using the solar cell manufacturing method of this embodiment shown in Figs. 3A to 3E. In Example 1, the printing area of ​​the contact electrode was enlarged to more clearly demonstrate the effect of reducing local damage during printing of the contact electrode. Specifically, in Figs. 1 to 3E, the formation of the first insulating layer 41 and the second insulating layer 42 was omitted, and the first contact electrode 51 was formed over the entire first region 7, and the second contact electrode 52 was formed over the entire second region 8. The solar cell of Example 1 and its manufacturing method have the following features. <Transparent electrode layer material film formation process> Transparent electrode layer material: amorphous ITO, formation method: CVD, film thickness: 100 nm <Metal electrode layer material film formation process> Metal electrode layer material: Cu, Forming method: PVD (sputtering), Film thickness: 250 nm <Conductive protective layer material film formation process> Conductive protection layer material: Crystalline ITO, Forming method: PVD, Film thickness: 50 nm <Insulating layer formation process> omission <Contact electrode formation process> Contact electrode material: Ag paste, Forming method: Screen printing, Drying: 180 degrees / 60 minutes, Film thickness: Approximately 30 μm <Conductive protective layer formation process (patterning)> Etching solution: 1 wt% hydrochloric acid (HCl) solution, etching time: 30 seconds <Transparent electrode layer forming process and metal electrode layer forming process (simultaneous patterning)> Etching solution: mixed solution of 5 wt% ammonium persulfate (ammonium persulfate) and 9 wt% hydrochloric acid (HCl), etching time: 60 seconds <Annealing> Contact electrode drying: 180 degrees / 1 hour

[0103] Comparative Example 1 A comparative back electrode type solar cell shown in Figs. 4A-4B was fabricated as Comparative Example 1 using the manufacturing method of the comparative solar cell shown in Figs. 5A-5E. Note that, in Comparative Example 1 as well, the printing area of ​​the contact electrode was enlarged to more clearly demonstrate the effect of reducing local damage during printing of the contact electrode. Specifically, in Figs. 4A-5E, the formation of the first insulating layer 41 and the second insulating layer 42 was omitted, and the first contact electrode 51 was formed over the entire first region 7, and the second contact electrode 52 was formed over the entire second region 8. The characteristics of the solar cell of Comparative Example 1 and its manufacturing method are as follows and shown in Table 2. <Transparent electrode layer material film formation process> Same as Example 1. <Metal electrode layer material film formation process> Same as Example 1. <Insulating layer formation process> omission <Contact electrode formation process> Same as Example 1. <Transparent electrode layer forming process and metal electrode layer forming process (simultaneous patterning)> Same as Example 1. <Annealing> Same as Example 1.

[0104] Comparative Example 2 The solar cell of Comparative Example 2 differs from Comparative Example 1 in that metal electrode layers 29, 39 are formed of Ag paste instead of Cu, and contact electrodes 51, 52 are omitted. <Transparent electrode layer material film formation process> Same as Comparative Example 1. <Metal electrode layer material film formation process> Metal electrode layer material: Ag paste, Forming method: Screen printing, Drying: 180 degrees / 60 minutes, Film thickness: Approximately 30 μm <Insulating layer formation process> omission <Contact electrode formation process> omission <Transparent electrode layer formation process (patterning)> Etching solution: 1 wt% hydrochloric acid (HCl) solution, etching time: 30 seconds <Annealing> Same as Comparative Example 1.

[0105] (Rating 1) Using a photoluminescence measuring device, light of a wavelength corresponding to the photoluminescence characteristics of the solar cell (wavelength: 915 nm, intensity 0.67 sun) was irradiated onto the light receiving surface of the solar cell, and the photoluminescence intensity from the solar cell was observed. The results are shown in Table 1. In Table 1, for each of Example 1 and Comparative Example 1, the photoluminescence intensity values ​​before annealing and after annealing are normalized based on the photoluminescence intensity value before annealing. [Table 1]

[0106] (Rating 2) Using a pulsed solar simulator with a spectral distribution of AM1.5, simulated sunlight was irradiated at 100 mW / cm at 25°C. 2 The performance characteristics (open circuit voltage Voc, short circuit current Isc, fill factor FF, conversion efficiency Eff, series resistance Rs and parallel resistance Rsh) of the solar cells of the above examples and comparative examples were measured. The measurement results are shown in Table 2. [Table 2]

[0107] According to Table 1, in the ITO / Cu / Ag electrode structure of Comparative Example 1, when heat was applied by annealing, the photoluminescence intensity of the lower part of the contact electrode made of Ag paste decreased. Also, according to Table 2, in the ITO / Cu / Ag electrode structure of Comparative Example 1, the performance characteristics of the solar cell decreased compared to the ITO / Ag electrode structure of Comparative Example 2.

[0108] As a result, in Comparative Example 1, local physical damage occurs to the metal electrode layers 29, 39 made of Cu during screen printing of Ag paste in the contact electrode formation process. Then, during wet etching in the transparent electrode layer formation process and the metal electrode layer formation process, the etching solution that has penetrated into the contact electrodes 51, 52 made of Ag paste penetrates into the damaged parts of the metal electrode layers 29, 39 made of Cu during annealing (heating), locally dissolves the transparent electrode layers 28, 38, and penetrates into the damaged parts of the semiconductor layers 25, 23, 35, 33. Then, the Cu components of the metal electrode layers 29, 39 diffuse into the semiconductor substrate 11. This is thought to cause a decrease in the performance of the solar cell.

[0109] In Comparative Example 1, during wet etching in the transparent electrode layer forming process and the metal electrode layer forming process, the etching solution that penetrates into the contact electrodes 51 and 52 made of Ag paste etches the metal electrode layers 29 and 39 made of Cu during annealing (heating), generating Cu ions. During annealing, these Cu ions migrate, for example, through the surfaces of the metal electrode layers 29 and 39 and diffuse into the semiconductor substrate 11. This is thought to result in a decrease in the performance of the solar cell.

[0110] On the other hand, according to Table 1, in the ITO / Cu / ITO / Ag electrode structure of Example 1, even when heated by annealing, the decrease in photoluminescence intensity at the bottom of the contact electrode made of Ag paste was suppressed. Also, according to Table 2, in the ITO / Cu / ITO / Ag electrode structure of Example 1, the decrease in performance characteristics of the solar cell was suppressed compared to the ITO / Cu / Ag electrode structure of Comparative Example 1, and the performance characteristics of the solar cell were comparable to those of the ITO / Ag electrode structure of Comparative Example 2.

[0111] Thus, in Example 1, the metal electrode layers 29, 39 made of Cu are protected by the conductive protective layers 27P, 37P during screen printing of Ag paste in the contact electrode forming step, and local physical damage to the metal electrode layers 29, 39 made of Cu is suppressed. Therefore, during wet etching in the transparent electrode layer forming step and the metal electrode layer forming step, the etching solution that has penetrated into the contact electrodes 51, 52 made of Ag paste is suppressed from penetrating into the metal electrode layers 29, 39 made of Cu, the transparent electrode layers 28, 38, and the semiconductor layers 25, 23, 35, 33 during annealing (heating), and the Cu components of the metal electrode layers 29, 39 are suppressed from diffusing into the semiconductor substrate 11. It is believed that this can suppress the deterioration of the performance of the solar cell.

[0112] In Example 1, the first transparent electrode layer 28 and the second transparent electrode layer 38 are amorphous (non-crystalline) transparent conductive films, the first conductive protection layer 27P and the second conductive protection layer 37P are crystalline transparent conductive films, and the etching rate (speed) of the crystalline transparent conductive film is lower (slower) than that of the amorphous transparent conductive film. Therefore, the etching solution that has penetrated into the contact electrodes 51 and 52 made of Ag paste during wet etching in the transparent electrode layer forming process and the metal electrode layer forming process is suppressed from penetrating into the metal electrode layers 29 and 39 made of Cu, the transparent electrode layers 28 and 38, and the semiconductor layers 25, 23, 35, and 33 during annealing (heating), and the metal components of the metal electrode layers 29 and 39, such as Cu, are suppressed from diffusing into the semiconductor substrate 11. It is believed that this can suppress the deterioration of the performance of the solar cell 1.

[0113] Furthermore, the first conductive protective layer 27P and the second conductive protective layer 37P prevent an etching solution that has penetrated into the contact electrodes 51, 52 made of Ag paste during wet etching in the transparent electrode layer forming step and the metal electrode layer forming step from etching the metal electrode layers 29, 39 made of Cu during annealing (heating), generating Cu ions, which then move, for example, through the surfaces of the metal electrode layers 29, 39 during annealing and diffuse into the semiconductor substrate 11. This is believed to prevent a decrease in the performance of the solar cell 1.

[0114] Furthermore, according to Table 2, the ITO / Cu / Ag electrode structure of Comparative Example 1 had a higher series resistance Rs than the ITO / Ag electrode structure of Comparative Example 2. This is thought to be because, in Comparative Example 1, the surfaces of the metal electrode layers 29, 39 made of Cu are oxidized, increasing the contact resistance between the metal electrode layers 29, 39 and the contact electrodes 51, 52 made of Ag paste.

[0115] On the other hand, according to Table 2, in the ITO / Cu / ITO / Ag electrode structure of Example 1, an increase in series resistance Rs was suppressed compared to the ITO / Cu / Ag electrode structure of Comparative Example 1, and the series resistance Rs was about the same even when compared to the ITO / Ag electrode structure of Comparative Example 2. From this, it is considered that in Example 1, the conductive protective layers 27P, 37P suppress oxidation of the surfaces of the metal electrode layers 29, 39 made of Cu, and thus it is possible to suppress an increase in the contact resistance between the metal electrode layers 29, 39 and the contact electrodes 51, 52 made of Ag paste. [Explanation of symbols]

[0116] 1,1X solar cell 7 First area 8 Second area 11 Semiconductor substrate 13,23,33 Passivation layer 15 Optical adjustment layer 25 First conductive type semiconductor layer 27,27X 1st electrode layer 27P 1st conductive protective layer 27PZ conductive protective layer material film 28 First transparent electrode layer 28Z Transparent electrode layer material film 29 First metal electrode layer 29Z Metal electrode layer material film 35 Second conductive type semiconductor layer 37,37X 2nd electrode layer 37P 2nd conductive protective layer 38 Second transparent electrode layer 39 Second metal electrode layer 41 First insulating layer 41a First non-insulated area 42 Second insulating layer 42a Second non-insulated area 51 First contact electrode 52 Second contact electrode 91 First wiring member 92 Second wiring member X1 1st straight line X2 2nd straight line

Claims

1. A method for manufacturing a back electrode type solar cell comprising: a semiconductor substrate; a first conductivity type semiconductor layer, a first transparent electrode layer, and a first metal electrode layer, which are laminated in this order in a first region, which is a part of one main surface side of the semiconductor substrate; and a second conductivity type semiconductor layer, a second transparent electrode layer, and a second metal electrode layer, which are laminated in this order in a second region, which is another part of the one main surface side of the semiconductor substrate, a transparent electrode layer material film forming step of forming a series of transparent electrode layer material films on the first conductive type semiconductor layer and the second conductive type semiconductor layer on the one main surface side of the semiconductor substrate; a metal electrode layer material film forming step of forming a series of metal electrode layer material films on the transparent electrode layer material film; a conductive protection layer material film forming step of forming a series of conductive protection layer material films on the material film of the metal electrode layer; an insulating layer forming step of forming a first insulating layer that entirely covers the material film of the conductive protection layer in the first region except for a first non-insulating region, and a second insulating layer that entirely covers the material film of the conductive protection layer in the second region except for a second non-insulating region, the first insulating layer and the second insulating layer being spaced apart from each other; a contact electrode forming step of forming contact electrodes in the first non-insulating region and the second non-insulating region; a transparent electrode layer and metal electrode layer forming step of removing exposed portions of the material film of the conductive protection layer, and the material film of the metal electrode layer and the material film of the transparent electrode layer corresponding to the exposed portions, by using an etching method using the first insulating layer, the second insulating layer and the contact electrode as a mask, thereby forming the first transparent electrode layer, the first metal electrode layer and the first conductive protection layer which are patterned, and the second transparent electrode layer, the second metal electrode layer and the second conductive protection layer which are patterned; Including, In the contact electrode forming step, a printing material including a particulate metal material and a resin material is printed and cured or dried to form the contact electrode; In the transparent electrode layer and metal electrode layer forming step, a material film of the conductive protection layer protects the metal electrode layer, the transparent electrode layer, the first conductive type semiconductor layer, the second conductive type semiconductor layer, and the semiconductor substrate from an etching solution that penetrates through the contact electrodes. How solar cells are manufactured.

2. The method for producing a solar cell according to claim 1 , wherein the material film of the metal electrode layer contains copper.

3. The method for producing a solar cell according to claim 2 , wherein the material film of the conductive protection layer is a transparent conductive film.

4. 4. The method for manufacturing a solar cell according to claim 3, wherein in the transparent electrode layer and metal electrode layer forming step, an exposed portion of the material film of the conductive protection layer is etched, and then the material film of the metal electrode layer and the material film of the transparent electrode layer are simultaneously etched.

5. the etching solution for the material film of the conductive protection layer is an acidic solution; The etching solution for simultaneous etching of the material film of the metal electrode layer and the material film of the transparent electrode layer is a mixed solution of an oxidizing agent and an acidic solution. The method for producing a solar cell according to claim 4 .

6. The method for manufacturing a solar cell according to any one of claims 1 to 5, wherein the printing material is a silver paste.

7. A back electrode type solar cell comprising: a semiconductor substrate; a first conductive type semiconductor layer, a first transparent electrode layer, and a first metal electrode layer, which are laminated in this order in a first region, which is a part of one main surface side of the semiconductor substrate; and a second conductive type semiconductor layer, a second transparent electrode layer, and a second metal electrode layer, which are laminated in this order in a second region, which is another part of the one main surface side of the semiconductor substrate; a first conductive protection layer formed on the first metal electrode layer; a second conductive protection layer formed on the second metal electrode layer; a first insulating layer entirely covering the first conductive protective layer except for a first non-insulating region; a second insulating layer entirely covering the second conductive protective layer except for a second non-insulating region; contact electrodes formed in the first non-insulating region and the second non-insulating region; A solar cell comprising:

8. The solar cell of claim 7 , wherein the first metal electrode layer and the second metal electrode layer comprise copper.

9. The solar cell according to claim 8 , wherein the first conductive protection layer and the second conductive protection layer are transparent conductive films.

10. the first transparent electrode layer and the second transparent electrode layer are amorphous transparent conductive films, The first conductive protection layer and the second conductive protection layer are crystalline transparent conductive films. The solar cell according to claim 9.

11. a region between the first metal electrode layer and the second metal electrode layer, the region between the first transparent electrode layer and the second transparent electrode layer being not covered with the first insulating layer and the second insulating layer; the first non-insulating region is not covered with the first insulating layer, exposes the first conductive protection layer, has the contact electrode on the exposed first conductive protection layer, and is disposed on a first straight line extending in a first direction along the one main surface of the semiconductor substrate; the second non-insulating region is not covered with the second insulating layer, exposes the second conductive protection layer, has the contact electrode on the exposed second conductive protection layer, and is disposed on a second straight line different from the first straight line extending in the first direction. The solar cell according to any one of claims 7 to 10.

12. the first insulating layer and the second insulating layer are strip-shaped extending in a second direction along the one main surface and intersecting the first direction, and are arranged alternately in the first direction; the first straight line and the second straight line intersect the first insulating layer and the second insulating layer and are alternately arranged in the second direction; The solar cell according to claim 11.

13. a first wiring member extending in the first direction along the first straight line and electrically connected to the contact electrode in the first non-insulating region; a second wiring member extending in the first direction along the second straight line and electrically connected to the contact electrode in the second non-insulating region; The solar cell according to claim 11 or 12, comprising:

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