JP7576461B2 - Method for manufacturing solar cell and solar cell - Google Patents

Description

The present invention relates to a method for manufacturing a back contact type solar cell, and to a back contact type solar cell.

Patent documents 1 to 3 disclose techniques relating to connections between electrodes of two polarities and wiring members in a back electrode type solar cell.
- having first wiring and second wiring intersecting 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:

In addition, Patent Document 3 describes a back electrode type solar cell,
-having p-electrode wiring and n-electrode wiring intersecting the p-electrode and the n-electrode,
・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:

JP 2018-133567 A JP 2015-159286 A JP 2014-127550 A

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, such as Cu (for example, a film formed using a PVD method such as sputtering or a plating method, followed by wet etching) as the material for the metal electrode layer, instead of the relatively expensive known Ag paste. Note that contact electrodes made of Ag paste are used only in the parts that make contact with the wiring members.

The inventor(s) of the present application have also devised a method for simplifying the manufacturing process of such solar cells by using the insulating layer and contact electrode (Ag paste) for ensuring insulation and contact with the wiring members as a resist for wet etching of the metal electrode layer (e.g., Cu) and transparent electrode layer.

However, according to the knowledge of the present inventor(s), such solar cells and their manufacturing methods can result in a decrease in the performance of the solar cells. This is considered to be due to the following reasons.

During wet etching of the metal electrode layer and the transparent electrode layer, the etching solution penetrates into the contact electrodes made of Ag paste. When the electrodes are subsequently annealed or heated in the operating environment, the etching solution that penetrates into the contact electrodes dissolves the metal electrode layer and the transparent electrode layer made of Cu. Then, due to some factor, Cu diffuses into the semiconductor substrate through the semiconductor layer (for example, through local defects, etc.). This can cause damage to the semiconductor substrate, reducing the performance of the solar cell (reliability).

The present invention aims to provide a solar cell and a method for manufacturing a solar cell that can suppress the deterioration of the solar cell's performance while reducing the cost of the solar cell.

The method for manufacturing a solar cell according to the present invention is a method for manufacturing 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 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 stacked in sequence in a second region which is another part of the one main surface side of the semiconductor substrate, the method comprising the steps 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, the metal electrode layer material film including copper, on the transparent electrode layer material film; an insulating layer forming step of forming a first insulating layer that entirely covers the metal electrode layer material film in the first region except for a first non-insulating region, and a second insulating layer that entirely covers the metal electrode layer material film 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; and an insulating layer forming step of forming a first insulating layer and a second insulating layer between the first insulating layer and the second insulating layer by using an etching method using the first insulating layer and the second insulating layer as a mask. and a metal electrode layer forming step of forming the first metal electrode layer patterned in the first region by removing exposed portions of the metal electrode layer material film in the first non-insulating region and the second non-insulating region, forming the second metal electrode layer patterned in the second region, and leaving the first insulating layer and the second insulating layer without removing them; a contact electrode forming step of forming a first contact electrode on the transparent electrode layer material film in the first non-insulating region so as to contact a side surface of the first metal electrode layer and a side surface of the first insulating layer, and forming a second contact electrode on the transparent electrode layer material film in the second non-insulating region so as to contact a side surface of the second metal electrode layer and a side surface of the second insulating layer; and a transparent electrode layer forming step of forming the first transparent electrode layer patterned in the first region by removing exposed portions of the transparent electrode layer material film using an etching method using the first insulating layer and the first contact electrode, and the second insulating layer and the second contact electrode as masks, forming the first transparent electrode layer patterned in the first region, forming the second transparent electrode layer patterned in the second region, and leaving the first insulating layer and the second insulating layer without removing them.

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 stacked in that 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 stacked in that order in a second region which is the other part of the one main surface side of the semiconductor substrate, and further comprising a first insulating layer formed in the first region so as to entirely cover the first metal electrode layer except for a first non-insulating region, a second insulating layer formed in the second region so as to entirely cover the second metal electrode layer except for a second non-insulating region, a first contact electrode formed in the first non-insulating region, and a second contact electrode formed in the second non-insulating region. The first metal electrode layer and the second metal electrode layer contain copper, the first transparent electrode layer is formed in the first non-insulating region, and the first metal electrode layer is not formed, the second transparent electrode layer is formed in the second non-insulating region, and the second metal electrode layer is not formed, the first contact electrode is in contact with the main surface of the first transparent electrode layer, the side surface of the first metal electrode layer, and the side surface of the first insulating layer, and the second contact electrode is in contact with the main surface of the second transparent electrode layer, the side surface of the second metal electrode layer, and the side surface of the second insulating layer.

Another solar cell manufacturing method 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 stacked in sequence in a first region that 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 stacked in sequence in a second region that is another part of the one main surface side of the semiconductor substrate, the method including 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, the metal electrode layer material film including copper, a first insulating layer that entirely covers the metal electrode layer material film in the first region, and a second insulating layer that entirely covers the metal electrode layer material film in the second region, the first insulating layer and the second insulating layer being spaced apart from each other. The method includes an insulating layer forming step of forming an insulating layer, a metal electrode layer forming step of forming the first metal electrode layer patterned in the first region by removing exposed portions of the metal electrode layer material film using an etching method with the first insulating layer and the second insulating layer as masks, forming the second metal electrode layer patterned in the second region, and removing the first insulating layer and the second insulating layer, a contact electrode layer forming step of forming a first contact electrode layer on the first metal electrode layer and a second contact electrode layer on the second metal electrode layer, and a transparent electrode layer forming step of forming the first transparent electrode layer patterned in the first region by removing exposed portions of the transparent electrode layer material film using an etching method with the first contact electrode layer and the first metal electrode layer, and the second contact electrode layer and the second metal electrode layer as masks, and forming the second transparent electrode layer patterned in the second region.

Another solar cell according to the present invention is 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 stacked in that order in a first region that 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 stacked in that order in a second region that is another part of the one main surface side of the semiconductor substrate, and includes a first contact electrode layer stacked on the first metal electrode layer, and a second contact electrode layer stacked on the second metal electrode layer. The first metal electrode layer and the second metal electrode layer contain copper.

According to the present invention, it is possible to suppress the deterioration of the performance of solar cells even while reducing the cost of solar cells.

1 is a diagram showing a solar cell according to a first embodiment as viewed from the back surface side. 2 is a cross-sectional view of the solar cell taken along line IIA-IIA in FIG. 1 . 2 is a cross-sectional view of the solar cell taken along line IIB-IIB in FIG. 1 . 3A to 3C are diagrams illustrating a semiconductor layer forming step in the method for manufacturing the solar cell according to the first embodiment. 3A to 3C are diagrams illustrating 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 the method for manufacturing the solar cell according to the first embodiment. 3A to 3C are diagrams illustrating an insulating layer forming step in the method for manufacturing the solar cell according to the first embodiment. 4A to 4C are diagrams illustrating a metal electrode layer forming step (electrode layer forming step) in the method for manufacturing the solar cell according to the first embodiment. 5A to 5C are diagrams illustrating a contact electrode forming step in the method for manufacturing the solar cell according to the first embodiment. 4A to 4C are diagrams illustrating a transparent electrode layer forming step (electrode layer forming step) in the method for manufacturing the solar cell according to the first embodiment. 2 is a cross-sectional view of a solar cell according to Comparative Example 1, taken along line IIA-IIA in FIG. 1 . 2 is a cross-sectional view of a solar cell according to Comparative Example 1, taken along line IIB-IIB in FIG. 1 . 1 is a diagram showing a transparent electrode layer material film forming step, a metal electrode layer material film forming step, and an insulating layer forming step in a manufacturing method for a solar cell according to Comparative Example 1. FIG. 11A to 11C are diagrams illustrating a contact electrode forming step in the solar cell manufacturing method according to Comparative Example 1. 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 manufacturing method for a solar cell according to Comparative Example 1. FIG. 11 is a view of a solar cell according to a second embodiment, viewed from the back surface side. 7 is a cross-sectional view of the solar cell shown in FIG. 6 taken along line VII-VII. 11A to 11C are diagrams illustrating a semiconductor layer forming step in a method for manufacturing a solar cell according to a second embodiment. 11A to 11C 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 according to a second embodiment. 11A to 11C are diagrams illustrating an insulating layer forming step in a method for manufacturing a solar cell according to a second embodiment. 13A to 13C are diagrams illustrating a metal electrode layer forming step (electrode layer forming step) in the method for manufacturing a solar cell according to a second embodiment. 13A to 13C are diagrams illustrating an insulating layer removal and formation step in the manufacturing method for a solar cell according to a second embodiment. 13A to 13C are diagrams illustrating a contact electrode layer forming step in the method for manufacturing a solar cell according to a second embodiment. 13A to 13C are diagrams illustrating a transparent electrode layer forming step (electrode layer forming step) in the method for manufacturing a solar cell according to a second embodiment. 7 is a cross-sectional view of a solar cell according to Comparative Example 2, taken along line VII-VII in FIG. 6 . 13 is a diagram showing a transparent electrode layer material film forming step, a metal electrode layer material film forming step, and a contact electrode layer forming step in a manufacturing method for a solar cell according to Comparative Example 2. FIG. 11 is a diagram showing an electrode layer forming step, that is, a transparent electrode layer forming step and a metal electrode layer forming step, in a manufacturing method for a solar cell according to Comparative Example 2. FIG.

Below, an example of an embodiment of the present invention will be described with reference to the attached drawings. Note that the same reference numerals will be used to refer to the same or equivalent parts in each drawing. For convenience, hatching and component reference numerals may be omitted, in which case other drawings should be referenced.

(Solar Cell of First Embodiment)
Fig. 1 is a view of the solar cell according to the first 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 a back contact type or back junction type) heterojunction solar cell.

The solar cell 1 comprises a semiconductor substrate 11 having two principal surfaces, and the principal surface of the semiconductor substrate 11 has a first region 7 and a second region 8. In the following, the principal surface of the semiconductor substrate 11 that receives light is referred to as the light-receiving surface, and the principal surface (one principal surface) of the semiconductor substrate 11 opposite the light-receiving surface is referred to as the back surface.

The first region 7 has a band-like shape and extends in the Y direction (second direction). Similarly, the second region 8 has a band-like shape and extends in the Y direction. The first region 7 and the second region 8 are alternately arranged in the X direction (first direction) that intersects with the Y direction.

2A and 2B, the solar cell 1 includes a passivation layer 13 and an optical adjustment layer 15, which are stacked in 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 stacked in 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 stacked in 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.

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 an n-type dopant is phosphorus (P). An example of a 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).

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

The 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 side of the semiconductor substrate 11. The passivation layer 33 is formed in a second region 8 on the back side of the semiconductor substrate 11. The passivation layers 13, 23, and 33 are formed of a material whose main component is, for example, an intrinsic (i-type) amorphous silicon material. The passivation layers 13, 23, and 33 suppress recombination of carriers generated in the semiconductor substrate 11 and increase the carrier recovery efficiency.

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 such as silicon oxide (SiO), silicon nitride (SiN), or a composite thereof such as silicon oxynitride (SiON).

The first conductive type semiconductor layer 25 is formed on the passivation layer 23, i.e., in the first region 7 on the back side of the semiconductor substrate 11. On the other hand, the second conductive type semiconductor layer 35 is formed on the passivation layer 33, i.e., in the second region 8 on the back 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 band-like 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).

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)).

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.

The first electrode layer 27 is formed on the first conductive type semiconductor layer 25, i.e., in the first region 7 on the back 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 the second region 8 on the back side of the semiconductor substrate 11. That is, the first electrode layer 27 and the second electrode layer 37 are strip-shaped and extend in the Y direction. The first electrode layer 27 and the second electrode layer 37 are alternately provided in the X direction.

The first electrode layer 27 has a first transparent electrode layer 28 and a first metal electrode layer 29 stacked in 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 and a second metal electrode layer 39 stacked in order on the second conductive type semiconductor layer 35.

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

The first metal electrode layer 29 and the second metal electrode layer 39 contain Cu as a metal material, which is less expensive than known conductive paste materials containing Ag powder. For example, the first metal electrode layer 29 and the second metal electrode layer 39 are formed using a PVD method such as sputtering, or a plating method.

The first insulating layer 41 is formed on the first metal electrode layer 29, i.e., in the first region 7 on the back side of the semiconductor substrate 11. The second insulating layer 42 is formed on the second metal electrode layer 39, i.e., in the second region 8 on the back side of the semiconductor substrate 11. That is, the first insulating layer 41 and the second insulating layer 42 are strip-shaped and extend in the Y direction, as shown in FIG. 1. The first insulating layer 41 and the second insulating layer 42 are alternately provided in the X direction.

The first insulating layer 41 entirely covers the first metal electrode layer 29, except for the first non-insulating region 41a. Similarly, the second insulating layer 42 entirely covers the second metal electrode layer 39, except for the second non-insulating region 42a.

The first non-insulating region 41a does not have the first insulating layer 41 or the first metal electrode layer 29 formed therein. In other words, the first non-insulating region 41a is composed of an opening that exposes the surface of the first transparent electrode layer 28 and the side of the first metal electrode layer 29. The first non-insulating region 41a is disposed on a first straight line X1 that extends in the X direction (first direction).

Similarly, the second non-insulating region 42a does not have the second insulating layer 42 and the second metal electrode layer 39 formed therein. That is, the second non-insulating region 42a is composed of an opening that exposes the surface of the second transparent electrode layer 38 and the side surface of the second metal electrode layer 39. The second non-insulating region 42a is disposed on a second straight line X2 that is different from the first straight line X1 that extends 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).

Materials for the first insulating layer 41 and the second insulating layer 42 include, for example, silicon oxide (SiO), silicon nitride (SiN), or a composite 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.

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 disposed on the first straight line X1, and the second contact electrode 52 is disposed on the second straight line X2.

The first contact electrode 51 is in contact with the surface of the first transparent electrode layer 28, the side of the first metal electrode layer 29, and the side of the first insulating layer 41. On the other hand, the second contact electrode 52 is in contact with the surface of the second transparent electrode layer 38, the side of the second metal electrode layer 39, and the side of the second insulating layer 42.

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, etc., a resin material, and a solvent. Among these, Ag paste material is preferred as the printing material from the viewpoint of contact with the solder for connection to the wiring member.

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 ensures alignment clearance when connecting the wiring members.

As shown in Figures 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, and the first metal electrode layer 29 and the second metal electrode layer 39 are separated. In addition, the first insulating layer 41 and the second insulating layer 42 are separated.

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, is not covered by the first insulating layer 41 and the second insulating layer 42.

In the first metal electrode layer 29, the main surface opposite the main surface in contact with the first transparent electrode layer 28 is covered with a first insulating layer 41. Similarly, in the second metal electrode layer 39, the main surface opposite the main surface in contact with the second transparent electrode layer 38 is covered with a second insulating layer 42.

On the other hand, 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.

As shown in FIG. 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 with the first electrode layer 27 and the second electrode layer 37, and are arranged alternately in the Y direction (second direction).

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.

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 layer, reduce output loss due to electrode resistance, and improve the power generation efficiency of the solar cell.

The first wiring member 91 and the second wiring member 92 may be a known tab wire, etc.

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, such as Cu (for example, a film formed using a PVD method such as sputtering or a plating method, followed by wet etching) as the material for the metal electrode layers 29, 39, instead of the relatively expensive known Ag paste. 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.

The inventor(s) of the present application have also devised a method for simplifying the manufacturing process of such solar cells by 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 as resists for wet etching of the metal electrode layers 29, 39 (e.g., Cu) and the transparent electrode layers 28, 38. Below, the solar cell devised by the inventor(s) of the present application and its manufacturing method are described as Comparative Example 1.

(Solar Cell of Comparative Example 1)
4A is a cross-sectional view of a solar cell according to comparative example 1, which is a cross-sectional view corresponding to line IIA-IIA in FIG. 1, and FIG. 4B is a cross-sectional view of a solar cell according to comparative example 1, which is a cross-sectional view corresponding to line IIB-IIB in FIG. 1. The solar cell 1X of Comparative Example 1 shown in Figures 4A and 4B differs from the solar cell 1 shown in Figures 2A and 2B mainly in that a first electrode layer 27X, i.e., a first transparent electrode layer 28X and a first metal electrode layer 29X, are also formed in the first non-insulating region 41a of the first insulating layer 41X, and a first contact electrode 51X is formed on the first metal electrode layer 29X of the first electrode layer 27X in the first non-insulating region 41a, and that a second electrode layer 37X, i.e., a second transparent electrode layer 38X and a second metal electrode layer 39X, are also formed in the second non-insulating region 42a of the second insulating layer 42X, and a second contact electrode 52X is formed on the second metal electrode layer 39X of the second electrode layer 37X in the second non-insulating region 42a.

(Method of manufacturing solar cell of Comparative Example 1)
5A to 5C, a description will be given below mainly of the manufacturing process of the electrode layers 27X, 37X in the manufacturing method of the solar cell of Comparative Example 1. In the manufacturing process of the electrode layers 27X, 37X in Comparative Example 1, the insulating layers 41X, 42X are formed, and then the contact electrodes 51X, 52X are formed, and then the electrode layers 27X, 37X, i.e., the metal electrode layers 29X, 39X and the transparent electrode layers 28X, 38X, are simultaneously patterned using the insulating layers 41X, 42X and the contact electrodes 51X, 52X as masks.

Figure 5A shows the transparent electrode layer material film forming process, the metal electrode layer material film forming process, and the insulating layer forming process in the solar cell manufacturing method of Comparative Example 1, and Figure 5B shows the contact electrode forming process in the solar cell manufacturing method of Comparative Example 1. Also, Figure 5C shows the electrode layer forming process, i.e., the transparent electrode layer forming process and the metal electrode layer forming process, in the solar cell manufacturing method of Comparative Example 1. Figures 5A to 5C show the back side of the semiconductor substrate 11, and the front side of the semiconductor substrate 11 is omitted.

First, as shown in FIG. 5A, 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 using, for example, a CVD method or a PVD method (transparent electrode layer material film formation process). Next, a series of metal electrode layer material films 29Z are 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, using, for example, a PVD method such as sputtering or a plating method (metal electrode layer material film formation process).

Next, a first insulating layer 41X 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 and the metal electrode layer material film 29Z. A second insulating layer 42X 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 formation process). The first insulating layer 41X and the second insulating layer 42X are formed to be spaced apart from each other.

For example, the first insulating layer 41X and the second insulating layer 42X are formed by printing and baking (curing) a printing material containing a resin material and a solvent using a pattern printing method such as press printing, such as screen printing or gravure printing, or ejection printing, such as inkjet printing.

Next, as shown in FIG. 5B, a first contact electrode 51X is formed in the first non-insulating region 41a of the first insulating layer 41X, and a second contact electrode 52X is formed in the second non-insulating region 42a of the second insulating layer 42X (contact electrode formation process). For example, the first contact electrode 51X and the second contact electrode 52X are formed by printing and baking (hardening) a printing material containing Ag particles, a resin material, and a solvent, i.e., an Ag paste material, using a pattern printing method such as press printing, such as screen printing or gravure printing, or ejection printing, such as inkjet printing.

Next, as shown in FIG. 5C, the metal electrode layer material film 29Z and the transparent electrode layer material film 28Z are simultaneously patterned using an etching method that uses the first insulating layer 41X and the first contact electrode 51X, and the second insulating layer 42X and the second contact electrode 52X as masks, to form the first transparent electrode layer 28X and the second transparent electrode layer 38X, which are separated from each other, and the first metal electrode layer 29X and the second metal electrode layer 39X, which are separated from each other (electrode layer formation process). As a result, the first electrode layer 27X and the second electrode layer 37X are formed. At this time, the first insulating layer 41X and the second insulating layer 42X are left without being removed.

The etching solution for simultaneous etching of the metal electrode layer material film 29Z and the transparent electrode layer material film 28Z can be a mixed solution of an oxidizing agent such as ammonium persulfate (ammonium persulfate) and hydrochloric acid (HCl).

According to the knowledge of the present inventor(s), the manufacturing method of solar cell 1X in Comparative Example 1 may result in a decrease in the performance of solar cell 1X. This is considered as follows.

First, during wet etching of the metal electrode layer material film 29Z and the transparent electrode layer material film 28Z, the etching solution penetrates into the contact electrodes 51X, 52X made of Ag paste. When subsequently annealed or heated in the usage environment, the etching solution that penetrated into the contact electrodes 51X, 52X dissolves the metal electrode layers 29X, 39X and the transparent electrode layers 28X, 38X made of Cu. Then, due to some factor, Cu diffuses into the semiconductor substrate 11 via the semiconductor layers 25, 23, 35, 33 (for example, via local defects, etc.). This may cause damage to the semiconductor substrate 11, resulting in a decrease in the performance of the solar cell 1X (reliability).

Secondly, a mixed solution of an oxidizing agent and hydrochloric acid is used as an etching solution for the metal electrode layer material film 29Z and the transparent electrode layer material film 28Z. In this etching solution, chlorine is generated from the hydrochloric acid by a reduction reaction of the oxidizing agent. This chlorine then transforms the contact electrodes 51X, 52X made of Ag paste into silver chloride. This may reduce the contact of the contact electrodes 51X, 52X with the wiring member, resulting in a reduction in the performance of the solar cell 1X (contact).

In this regard, the inventor(s) of the present application devised a method in which a metal electrode layer made of Cu is etched using a mixed solution of an oxidizing agent and hydrochloric acid, and then a contact electrode made of Ag is formed, and then the transparent electrode layer is etched using only hydrochloric acid.

(Method of manufacturing the solar cell according to the first embodiment)
Hereinafter, the method for manufacturing a solar cell according to the first embodiment will be described with reference to Figures 3A to 3F. Figure 3A is a diagram showing a semiconductor layer forming step in the method for manufacturing a solar cell according to the first embodiment, and Figure 3B is a diagram showing a transparent electrode layer material film forming step and a metal electrode layer material film forming step (electrode layer material film forming step) in the method for manufacturing a solar cell according to the first embodiment. Also, Figure 3C is a diagram showing an insulating layer forming step in the method for manufacturing a solar cell according to the first embodiment, and Figure 3D is a diagram showing a metal electrode layer forming step (electrode layer forming step) in the method for manufacturing a solar cell according to the first embodiment. Also, Figure 3E is a diagram showing a contact electrode forming step in the method for manufacturing a solar cell according to the first embodiment, and Figure 3F is a diagram showing a transparent electrode layer forming step (electrode layer forming step) in the method for manufacturing a solar cell according to the first embodiment. In Figures 3A to 3F, the back side of the semiconductor substrate 11 is shown, and the front side of the semiconductor substrate 11 is omitted.

3A, a passivation layer 23 and a first conductive type semiconductor layer 25 are formed on a portion of the back surface of the semiconductor substrate 11, specifically in the first region 7 (semiconductor layer formation process). For example, after a passivation layer material film and a first conductive type semiconductor layer material film are formed on the entire back surface 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 or a metal mask generated using a photolithography technique or a printing technique.

The etching solution for the p-type semiconductor layer material film can be, for example, an acidic solution such as hydrofluoric acid containing ozone or a mixture of nitric acid and hydrofluoric acid, and the etching solution for the n-type semiconductor layer material film can be, for example, an alkaline solution such as an aqueous solution of potassium hydroxide.

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, a mask may be used to simultaneously form and pattern the passivation layer 23 and the first conductive type semiconductor layer 25.

Next, a passivation layer 33 and a second conductive type semiconductor layer 35 are formed on another part of the back side of the semiconductor substrate 11, specifically in the second region 8 (semiconductor layer formation process). 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 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 or a metal mask generated using a photolithography technique or a printing technique.

Alternatively, when a passivation layer and a second conductive type semiconductor layer are laminated on the back side of the semiconductor substrate 11 using a CVD method or a PVD method, a mask may be used to simultaneously form and pattern the passivation layer 33 and the second conductive type semiconductor layer 35.

In addition, in this semiconductor layer formation process, a passivation layer 13 may be formed on the entire light-receiving surface side of the semiconductor substrate 11 (not shown).

Next, as shown in FIG. 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, CVD or PVD.

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 can be formed, for example, by a PVD method such as sputtering, or by a plating method.

Next, as shown in FIG. 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 and the metal electrode layer material film 29Z. 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 formation process). Note that the first insulating layer 41 and the second insulating layer 42 are formed to be spaced apart from each other.

Methods for forming the first insulating layer 41 and the second insulating layer 42 include the PVD method, CVD method, screen printing method, inkjet method, gravure coating method, and dispenser method. Among these, the first insulating layer 41 and the second insulating layer 42 may be formed by printing and baking (curing) a printing material containing a resin material and a solvent using a pattern printing method such as press printing, such as screen printing or gravure printing, or ejection printing, such as inkjet printing.

Next, as shown in FIG. 3D, an etching method using the first insulating layer 41 and the second insulating layer 42 as a mask is used to remove exposed portions of the metal electrode layer material film 29Z between the first insulating layer 41 and the second insulating layer 42 and in the first non-insulating region 41a and the second non-insulating region 42a, thereby forming a patterned first metal electrode layer 29 in the first region 7 and a patterned second metal electrode layer 39 in the second region 8 (metal electrode layer formation process: electrode layer formation process).

The etching solution for etching the metal electrode layer material film 29Z can be a mixed solution of an oxidizing agent such as ammonium persulfate (ammonium persulfate) and hydrochloric acid (HCl). At this time, since no contact electrode made of Ag is formed, the etching solution is not contained in the contact electrode. In addition, the contact electrode is not denatured.

Next, as shown in FIG. 3E, 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 formation process). As a result, the first contact electrode 51 contacts the surface of the first transparent electrode layer 28, the side of the first metal electrode layer 29, and the side of the first insulating layer 41. In addition, the second contact electrode 52 contacts the surface of the second transparent electrode layer 38, the side of the second metal electrode layer 39, and the side of the second insulating layer.

Methods for forming the first contact electrode 51 and the second contact electrode 52 include press printing such as screen printing or gravure printing, or pattern printing such as ejection printing such as inkjet printing. In the pattern printing method, the first contact electrode 51 and the second contact electrode 52 are formed by printing and baking (hardening) a printing material containing Ag particles, a resin material, and a solvent, i.e., an Ag paste material.

Next, as shown in FIG. 3F, an etching method is used 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 remove the exposed portions of the transparent electrode layer material film 28Z between the first insulating layer 41 and the second insulating layer 42, thereby forming a patterned first transparent electrode layer 28 in the first region 7, and a patterned second transparent electrode layer 38 in the second region 8 (electrode layer forming process: transparent electrode layer forming process). 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 unremoved.

Hydrochloric acid (HCl) is an example of an etching solution for the transparent electrode layer material film 28Z. In this case, since a mixed solution of an oxidizing agent and hydrochloric acid is not used, the metal electrode layers 29 and 39 made of Cu are not dissolved, and Cu does not diffuse into the semiconductor substrate 11 through the semiconductor layers 25, 23, 35, and 33 (for example, through local defects) due to some factor. Therefore, the semiconductor substrate 11 is not damaged. In addition, the contact electrodes 51 and 52 are not denatured.

Then, an optical adjustment layer 15 (not shown) is formed on the entire light-receiving surface side of the semiconductor substrate 11. Through the above steps, the back electrode type solar cell 1 of this embodiment shown in Figures 1, 2A, and 2B is obtained.

As described above, according to the manufacturing method of the solar cell of this embodiment, a relatively inexpensive metal, such as Cu (e.g., a film formed using a PVD method such as sputtering or a plating method, 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 1.

In addition, according to the solar cell manufacturing method 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 resists for wet etching of the metal electrode layers 29, 39 and the transparent electrode layers 28, 38, simplifying the solar cell manufacturing process.

Furthermore, according to the solar cell manufacturing method of this embodiment, it is necessary to use a mixed solution of an oxidizing agent and hydrochloric acid. After etching the metal electrode layers 29, 39 made of Cu, the contact electrodes 51, 52 made of Ag are formed, and then the transparent electrode layers 28, 38 are etched using only hydrochloric acid. This makes it possible to suppress the deterioration of the performance of the solar cell 1, as will be described in detail below.

First, the contact electrodes 51, 52 made of Ag paste do not come into contact with the mixed solution of oxidizer and hydrochloric acid used for wet etching of the metal electrode layers 29, 39. As a result, unlike the above-mentioned Comparative Example 1, there is no diffusion of Cu into the semiconductor substrate 11 due to the etching solution penetrating into the contact electrodes 51, 52 made of Ag paste. This prevents damage to the semiconductor substrate 11 caused by Cu, and suppresses the resulting deterioration in the performance of the solar cell 1 (reliability).

Secondly, the contact electrodes 51, 52 made of Ag do not come into contact with the mixed solution of the oxidizing agent and hydrochloric acid, and are not denatured. As a result, there is no deterioration in the contact of the contact electrodes 51, 52 with the wiring member due to the denaturation of the contact electrodes 51, 52 made of Ag, and the deterioration in the performance of the solar cell 1 due to this can be suppressed (contact).

In this way, the solar cell manufacturing method of this embodiment can suppress deterioration in solar cell performance while simplifying the manufacturing process and reducing the cost of the solar cell.

(Solar Cell of Second Embodiment)
In the first embodiment, a configuration in which a wiring member is disposed on the rear surface of a solar cell is described. In the second embodiment, a configuration in which a wiring member is not disposed on the rear surface of a solar cell, that is, a configuration in which an insulating layer does not need to be disposed on the rear surface of a solar cell is described.

Figure 6 is a view of the solar cell according to the second embodiment as seen from the back side, and Figure 7 is a cross-sectional view of the solar cell in Figure 6 taken along line VII-VII. Solar cell 1A shown in Figures 6 and 7 is also a back electrode type (also called back contact type or back junction type) heterojunction solar cell.

The solar cell 1A has a semiconductor substrate 11 with two main surfaces, and has a first region 7 and a second region 8 on the main surfaces (light-receiving surface and back surface) of the semiconductor substrate 11.

The first region 7 has a so-called comb shape and has multiple finger portions 7f that correspond to the teeth of the comb, and busbar portions 7b that correspond to the supports of the teeth of the comb. The busbar portions 7b extend in a first direction (X direction) along one side of the semiconductor substrate 11, and the finger portions 7f extend from the busbar portions 7b in a second direction (Y direction) that intersects with the first direction.

Similarly, the second region 8 has a so-called comb shape and has multiple finger portions 8f corresponding to the teeth of the comb and busbar portions 8b corresponding to the supports of the teeth of the comb. The busbar portions 8b extend in a first direction (X direction) along one side portion of the semiconductor substrate 11 that faces the other side portion, and the finger portions 8f extend in a second direction (Y direction) from the busbar portions 8b.

Finger portion 7f and finger portion 8f are strip-shaped extending in the second direction (Y direction) and are arranged alternately in the first direction (X direction).

As shown in FIG. 7, the solar cell 1A includes a passivation layer 13 and an optical adjustment layer 15, which are stacked in order on the light receiving surface side of the semiconductor substrate 11. The solar cell 1A also includes a passivation layer 23, a first conductive type semiconductor layer 25, and a first electrode layer 27A, which are stacked in order on a portion (first region 7) of the back surface side of the semiconductor substrate 11. The solar cell 1A also includes a passivation layer 33, a second conductive type semiconductor layer 35, and a second electrode layer 37A, which are stacked in order on another portion (second region 8) of the back surface side of the semiconductor substrate 11. The solar cell 1A also includes a first contact electrode layer 51A corresponding to the first electrode layer 27A, and a second contact electrode layer 52A corresponding to the second electrode layer 37A.

The first conductive type semiconductor layer 25 and the second conductive type semiconductor layer 35 are shaped like a comb, and have a number of finger portions corresponding to the teeth of the comb, and a busbar portion corresponding to the support portion of the teeth of the comb. The busbar portion extends in a first direction (X direction) along one side of the semiconductor substrate 11, and the finger portions extend from the busbar portion in a second direction (Y direction) that intersects with the first direction.

The first electrode layer 27A is formed on the first conductive type semiconductor layer 25, i.e., in the first region 7 on the back side of the semiconductor substrate 11. On the other hand, the second electrode layer 37A is formed on the second conductive type semiconductor layer 35, i.e., in the second region 8 on the back side of the semiconductor substrate 11. That is, the first electrode layer 27A and the second electrode layer 37A have a so-called comb shape and have a plurality of finger portions corresponding to the comb teeth and a busbar portion corresponding to the support portion of the comb teeth. The busbar portion extends in a first direction (X direction) along one side of the semiconductor substrate 11, and the finger portion extends from the busbar portion in a second direction (Y direction) intersecting the first direction.

The first electrode layer 27A has a first transparent electrode layer 28A and a first metal electrode layer 29A stacked in order on the first conductive type semiconductor layer 25. On the other hand, the second electrode layer 37A has a second transparent electrode layer 38A and a second metal electrode layer 39A stacked in order on the second conductive type semiconductor layer 35.

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

The first metal electrode layer 29A and the second metal electrode layer 39A contain Cu as a metal material, which is less expensive than known conductive paste materials containing Ag powder. For example, the first metal electrode layer 29A and the second metal electrode layer 39A are formed using a PVD method such as sputtering, or a plating method.

The first contact electrode layer 51A is formed on the first metal electrode layer 29A, i.e., in the first region 7 on the back side of the semiconductor substrate 11. The second contact electrode layer 52A is formed on the second metal electrode layer 39A, i.e., in the second region 8 on the back side of the semiconductor substrate 11. That is, as shown in FIG. 6, the first contact electrode layer 51A and the second contact electrode layer 52A have a so-called comb shape and have a plurality of finger portions corresponding to the comb teeth and a busbar portion corresponding to the support portion of the comb teeth. The busbar portion extends in a first direction (X direction) along one side of the semiconductor substrate 11, and the finger portion extends from the busbar portion in a second direction (Y direction) intersecting the first direction.

The first contact electrode layer 51A and the second contact electrode layer 52A are formed by printing and curing a printing material containing particulate metal material such as Cu, Ag, Al, etc., a resin material, and a solvent. Among these, Ag paste material is preferred as the printing material from the viewpoint of contact with the solder for connection to the wiring member.

As shown in FIG. 6, the first wiring member 91 is electrically connected to the busbar portion of the first electrode layer 27A via the first contact electrode layer 51A. Meanwhile, the second wiring member 92 is electrically connected to the busbar portion of the second electrode layer 37A via the second contact electrode layer 52A.

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, such as Cu (for example, a film formed using a PVD method such as sputtering or a plating method, followed by wet etching) as the material for the metal electrode layers 29A, 39A, instead of the relatively expensive known Ag paste. In addition, taking into consideration the contact with the wiring members 91, 92, contact electrode layers 51A, 52A made of Ag paste are used on the metal electrode layers 29A, 39A.

The inventor(s) of the present application also devised a method for simplifying the manufacturing process of such solar cells by using the contact electrode layers 51A, 52A (Ag paste) for ensuring contact with the wiring members 91, 92 as a resist for wet etching of the metal electrode layers 29A, 39A (e.g., Cu) and the transparent electrode layers 28A, 38A. The solar cell and its manufacturing method devised by the inventor(s) of the present application are described below as Comparative Example 2.

(Solar Cell of Comparative Example 2)
Fig. 9 is a cross-sectional view of a solar cell according to Comparative Example 2, which is a cross-sectional view corresponding to line VII-VII in Fig. 6. Solar cell 1Y of Comparative Example 2 shown in Fig. 9 differs from solar cell 1A shown in Fig. 7 mainly in that the width of first electrode layer 27Y, i.e., the width of first metal electrode layer 29Y and first transparent electrode layer 28Y, is the same as or narrower than the width of first contact electrode layer 51Y, and in that the width of second electrode layer 37Y, i.e., the width of second metal electrode layer 39Y and second transparent electrode layer 38Y, is the same as or narrower than the width of second contact electrode layer 52Y.

(Method of manufacturing solar cell of Comparative Example 2)
10A to 10B, a description will be given mainly of the manufacturing process of the electrode layers 27Y, 37Y in the manufacturing method of the solar cell of Comparative Example 2. In the manufacturing process of the electrode layers 27Y, 37Y of Comparative Example 2, the contact electrode layers 51Y, 52Y are formed, and then the electrode layers 27Y, 37Y, i.e., the metal electrode layers 29Y, 39Y and the transparent electrode layers 28Y, 38Y, are simultaneously patterned using the contact electrode layers 51Y, 52Y as masks.

Figure 10A shows the transparent electrode layer material film formation process, the metal electrode layer material film formation process, and the contact electrode layer formation process in the solar cell manufacturing method of Comparative Example 2, and Figure 10B shows the electrode layer formation process, i.e., the transparent electrode layer formation process and the metal electrode layer formation process, in the solar cell manufacturing method of Comparative Example 2. Figures 10A and 10B show the back side of the semiconductor substrate 11, and the front side of the semiconductor substrate 11 is omitted.

10A, 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, for example, using a CVD method or a PVD method (transparent electrode layer material film formation process). Next, a series of metal electrode layer material films 29Z are 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, for example, using a PVD method such as sputtering or a plating method (metal electrode layer material film formation process).

Next, a first contact electrode layer 51Y is formed on the first conductive type semiconductor layer 25, i.e., in the first region 7, via the transparent electrode layer material film 28Z and the metal electrode layer material film 29Z. A second contact electrode layer 52Y is formed on the second conductive type semiconductor layer 35, i.e., in the second region 8, via the transparent electrode layer material film 28Z and the metal electrode layer material film 29Z (contact electrode layer formation process). The first contact electrode layer 51Y and the second contact electrode layer 52Y are formed to be spaced apart from each other.

For example, the first contact electrode layer 51Y and the second contact electrode layer 52Y are formed by printing and baking (hardening) a printing material containing Ag particles, a resin material, and a solvent, i.e., an Ag paste material, using a pattern printing method such as press printing, such as screen printing or gravure printing, or ejection printing, such as inkjet printing.

Next, as shown in FIG. 10B, the metal electrode layer material film 29Z and the transparent electrode layer material film 28Z are simultaneously patterned using an etching method with the first contact electrode layer 51Y and the second contact electrode layer 52Y as masks to form the first transparent electrode layer 28Y and the second transparent electrode layer 38Y, which are separated from each other, and the first metal electrode layer 29Y and the second metal electrode layer 39Y, which are separated from each other (transparent electrode layer forming process, metal electrode layer forming process). As a result, the first electrode layer 27Y and the second electrode layer 37Y are formed.

The etching solution for simultaneous etching of the metal electrode layer material film 29Z and the transparent electrode layer material film 28Z can be a mixed solution of an oxidizing agent such as ammonium persulfate (ammonium persulfate) and hydrochloric acid (HCl).

According to the knowledge of the present inventor(s), even the manufacturing method of solar cell 1Y in Comparative Example 2 may result in a decrease in the performance of solar cell 1X. This is considered as follows.

First, as in Comparative Example 1, during wet etching of the metal electrode layer material film 29Z and the transparent electrode layer material film 28Z, the etching solution penetrates into the contact electrode layers 51Y, 52Y made of Ag paste. When subsequently annealed or heated in the usage environment, the etching solution that penetrated into the contact electrode layers 51Y, 52Y dissolves the metal electrode layers 29Y, 39Y and the transparent electrode layers 28Y, 38Y made of Cu. Then, due to some factor, Cu diffuses into the semiconductor substrate 11 via the semiconductor layers 25, 23, 35, 33 (for example, via local defects, etc.). This may cause damage to the semiconductor substrate 11, resulting in a decrease in the performance of the solar cell 1Y (reliability).

Secondly, as in Comparative Example 1, a mixed solution of an oxidizing agent and hydrochloric acid is used as the etching solution for the metal electrode layer material film 29Z and the transparent electrode layer material film 28Z. In this etching solution, chlorine is generated from the hydrochloric acid by the reduction reaction of the oxidizing agent. This chlorine then modifies the contact electrode layers 51Y, 52Y made of Ag paste into silver chloride. This may reduce the contact of the contact electrode layers 51Y, 52Y with the wiring member, resulting in a decrease in the performance of the solar cell 1Y (contact).

In this regard, the inventor(s) of the present application devised a method of etching a metal electrode layer made of Cu, which requires the use of a mixed solution of an oxidizing agent and hydrochloric acid, followed by forming a contact electrode layer made of Ag, and then etching the transparent electrode layer using only hydrochloric acid.

(Method of manufacturing solar cell according to second embodiment)
Hereinafter, the method for manufacturing a solar cell according to the second embodiment will be described with reference to Figures 8A to 8G. Figure 8A is a diagram showing a semiconductor layer forming step in the method for manufacturing a solar cell according to the second embodiment, and Figure 8B is a diagram showing a transparent electrode layer material film forming step and a metal electrode layer material film forming step (electrode layer material film forming step) in the method for manufacturing a solar cell according to the second embodiment. Also, Figure 8C is a diagram showing an insulating layer forming step in the method for manufacturing a solar cell according to the second embodiment, Figure 8D is a diagram showing a metal electrode layer forming step (electrode layer forming step) in the method for manufacturing a solar cell according to the second embodiment, and Figure 8E is a diagram showing an insulating layer removing step in the method for manufacturing a solar cell according to the second embodiment. Also, Figure 8F is a diagram showing a contact electrode layer forming step in the method for manufacturing a solar cell according to the second embodiment, and Figure 8G is a diagram showing a transparent electrode layer forming step (electrode layer forming step) in the method for manufacturing a solar cell according to the second embodiment. In Figures 8A to 8G, the back side of the semiconductor substrate 11 is shown, and the front side of the semiconductor substrate 11 is omitted.

First, as shown in FIG. 8A, in the same manner as described above, a passivation layer 23 and a first conductive type semiconductor layer 25 are formed on a portion of the back surface of the semiconductor substrate 11, specifically in the first region 7 (semiconductor layer formation process). Next, in the same manner as described above, a passivation layer 33 and a second conductive type semiconductor layer 35 are formed on another portion of the back surface of the semiconductor substrate 11, specifically in the second region 8 (semiconductor layer formation process). Note that in this semiconductor layer formation process, a passivation layer 13 may be formed on the entire light receiving surface side of the semiconductor substrate 11 (not shown).

Next, as shown in FIG. 8B, a series of transparent electrode layer material films 28Z are formed across the first conductive type semiconductor layer 25 and the second conductive type semiconductor layer 35 in the same manner as described above (transparent electrode layer material film formation process). The transparent electrode layer material film 28Z can be formed by, for example, CVD or PVD.

Next, in the same manner as described above, a series of metal electrode layer material films 29Z (e.g., Cu) are 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 can be formed, for example, by a PVD method such as sputtering, or by a plating method.

Next, as shown in FIG. 8C, in the same manner as described above, a first insulating layer 41A is formed on the first conductive type semiconductor layer 25, i.e., in the first region 7, via the transparent electrode layer material film 28Z and the metal electrode layer material film 29Z. A second insulating layer 42A is formed on the second conductive type semiconductor layer 35, i.e., in the second region 8, via the transparent electrode layer material film 28Z and the metal electrode layer material film 29Z (insulating layer formation process). Note that the first insulating layer 41A and the second insulating layer 42A are formed so as to be spaced apart from each other.

Methods for forming the first insulating layer 41A and the second insulating layer 42A include the PVD method, CVD method, screen printing method, inkjet method, gravure coating method, and dispenser method. Among these, it is preferable to form the first insulating layer 41A and the second insulating layer 42A by printing and baking (curing) a printing material containing a resin material and a solvent using a pattern printing method such as press printing such as screen printing or gravure printing, or ejection printing such as inkjet printing.

Next, as shown in FIG. 8D, an etching method using the first insulating layer 41A and the second insulating layer 42A as a mask is used to remove the exposed portion of the metal electrode layer material film 29Z between the first insulating layer 41A and the second insulating layer 42A, thereby forming a patterned first metal electrode layer 29A in the first region 7 and a patterned second metal electrode layer 39A in the second region 8 (metal electrode layer formation process: electrode layer formation process).

The etching solution for etching the metal electrode layer material film 29Z can be a mixed solution of an oxidizing agent such as ammonium persulfate (ammonium persulfate) and hydrochloric acid (HCl). At this time, since a contact electrode layer made of Ag is not formed, the etching solution is not contained in the contact electrode layer. In addition, the contact electrode layer is not denatured.

Next, as shown in FIG. 8E, the first insulating layer 41A and the second insulating layer 42A are removed. Examples of the removal solution include an organic solvent such as acetone or an alkaline solution such as a sodium hydroxide solution.

Next, as shown in FIG. 8F, a first contact electrode layer 51A is formed on the first insulating layer 41A, and a second contact electrode layer 52A is formed on the second insulating layer 42A (contact electrode layer formation process).

Methods for forming the first contact electrode layer 51A and the second contact electrode layer 52A include press printing such as screen printing or gravure printing, or pattern printing such as ejection printing such as inkjet printing. In the pattern printing method, the first contact electrode layer 51A and the second contact electrode layer 52A are formed by printing and baking (curing) a printing material containing Ag particles, a resin material, and a solvent, i.e., an Ag paste material.

Next, as shown in FIG. 8G, an etching method is used with the first contact electrode layer 51A and the first metal electrode layer 29A, and the second contact electrode layer 52A and the second metal electrode layer 39A as masks to remove exposed portions of the transparent electrode layer material film 28Z between the first metal electrode layer 29A and the second metal electrode layer 39A, thereby forming a patterned first transparent electrode layer 28A in the first region 7 and a patterned second transparent electrode layer 38A in the second region 8 (transparent electrode layer formation process: electrode layer formation process). As a result, the first electrode layer 27A and the second electrode layer 37A are formed.

Hydrochloric acid (HCl) is an example of an etching solution for the transparent electrode layer material film 28Z. In this case, since a mixed solution of an oxidizing agent and hydrochloric acid is not used, the metal electrode layers 29A and 39A made of Cu are not dissolved, and Cu does not diffuse into the semiconductor substrate 11 through the semiconductor layers 25, 23, 35, and 33 (for example, through local defects) due to some factor. Therefore, the semiconductor substrate 11 is not damaged. In addition, the contact electrode layers 51A and 52A are not denatured.

Then, an optical adjustment layer 15 (not shown) is formed on the entire light-receiving surface side of the semiconductor substrate 11. Through the above steps, the back electrode type solar cell 1A of this embodiment shown in Figures 6 and 7 is obtained.

As explained above, in the method for manufacturing the solar cell of this embodiment, a relatively inexpensive metal, such as Cu (e.g., a film formed using a PVD method such as sputtering or a plating method, followed by wet etching) is used as the material for the metal electrode layers 29A and 39A instead of the relatively expensive known Ag paste. This makes it possible to reduce the cost of the solar cell 1A.

Furthermore, the manufacturing method of the solar cell of this embodiment also requires the use of a mixed solution of an oxidizing agent and hydrochloric acid. After etching the metal electrode layers 29A, 39A made of Cu, the contact electrode layers 51A, 52A made of Ag are formed, and then the transparent electrode layers 28A, 38A are etched using only hydrochloric acid. This makes it possible to suppress the deterioration of the performance of the solar cell 1A, as described in detail below.

First, the contact electrode layers 51A, 52A made of Ag paste do not come into contact with the mixed solution of oxidizing agent and hydrochloric acid used for wet etching of the metal electrode layers 29A, 39A. As a result, as in Comparative Example 2 described above, there is no diffusion of Cu into the semiconductor substrate 11 due to the etching solution penetrating into the contact electrode layers 51A, 52A made of Ag paste. This prevents damage to the semiconductor substrate 11 caused by Cu, and suppresses the resulting deterioration in the performance of the solar cell 1A (reliability).

Secondly, the contact electrode layers 51A, 52A made of Ag do not come into contact with the mixed solution of the oxidizing agent and hydrochloric acid and are not denatured. As a result, there is no deterioration in the contact of the contact electrode layers 51A, 52A with the wiring member caused by the denaturation of the contact electrode layers 51A, 52A made of Ag, and the deterioration in the performance of the solar cell 1A caused by this can be suppressed (contact).

In this way, the solar cell manufacturing method of this embodiment can suppress the deterioration of solar cell performance while reducing the cost of solar cells.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications and variations are possible. For example, the above-described embodiments illustrate a method for manufacturing solar cells 1, 1A using crystalline silicon-based materials. However, the present invention is not limited to this, and can be applied to a method for manufacturing solar cells using various materials such as gallium arsenide (GaAs).

In addition, in the above-described embodiment, a method for manufacturing the heterojunction solar cells 1, 1A is illustrated. However, the present invention is not limited to this, and can be applied to a method for manufacturing various solar cells, such as a homojunction solar cell.

REFERENCE SIGNS LIST 1, 1A, 1X, 1Y Solar cell 7 First region 8 Second region 11 Semiconductor substrate 13, 23, 33 Passivation layer 15 Optical adjustment layer 25 First conductive type semiconductor layer 27, 27A, 27X, 27Y First electrode layer 28, 28A, 28X, 28Y First transparent electrode layer 28Z Transparent electrode layer material film 29, 29A, 29X, 29Y First metal electrode layer 29Z Metal electrode layer material film 35 Second conductive type semiconductor layer 37, 37A, 37X, 37Y Second electrode layer 38, 38A, 38X, 38Y Second transparent electrode layer 39, 39, 39X, 39Y Second metal electrode layer 41, 41A, 41X First insulating layer 41a First non-insulating region 42, 42A, 42X Second insulating layer 42a Second non-insulating region 51, 51A, 51X, 51Y First contact electrode 51A, 51Y First contact electrode layer 52, 52A, 52X, 52Y Second contact electrode 52A, 52Y Second contact electrode layer 91, 91A First wiring member 92, 92A Second wiring member X1 First straight line X2 Second straight line

Claims (10)

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, the metal electrode layer material film including copper, on the transparent electrode layer material film;
an insulating layer forming step of forming a first insulating layer that entirely covers the metal electrode layer material film in the first region except for a first non-insulating region, and a second insulating layer that entirely covers the metal electrode layer material film 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 metal electrode layer forming process, in which exposed portions of the metal electrode layer material film between the first insulating layer and the second insulating layer and in the first non-insulating region and the second non-insulating region are removed using an etching method using the first insulating layer and the second insulating layer as a mask, thereby forming the first metal electrode layer patterned in the first region, forming the second metal electrode layer patterned in the second region, and leaving the first insulating layer and the second insulating layer unremoved;
a contact electrode forming step of forming a first contact electrode on the transparent electrode layer material film in the first non-insulating region so as to contact a side surface of the first metal electrode layer and a side surface of the first insulating layer, and forming a second contact electrode on the transparent electrode layer material film in the second non-insulating region so as to contact a side surface of the second metal electrode layer and a side surface of the second insulating layer;
a transparent electrode layer forming process for forming the first transparent electrode layer patterned in the first region by removing exposed portions of the transparent electrode layer material film using an etching method with the first insulating layer and the first contact electrode, and the second insulating layer and the second contact electrode as masks, and for forming the second transparent electrode layer patterned in the second region, and for leaving the first insulating layer and the second insulating layer unremoved;
A method for manufacturing a solar cell, comprising: The method for manufacturing a solar cell according to claim 1, wherein in the contact electrode formation process, the first contact electrode and the second contact electrode are formed by printing and curing a printing material containing a particulate metal material, a resin material, and a solvent. The method for manufacturing a solar cell according to claim 2, wherein the printing material is a silver paste containing particulate silver material. In the metal electrode layer forming step, a mixed solution of an oxidizing agent and hydrochloric acid is used as an etching solution,
In the transparent electrode layer forming step, hydrochloric acid is used as an etching solution.
The method for producing a solar cell according to any one of claims 1 to 3. 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 insulating layer formed in the first region so as to entirely cover the first metal electrode layer except for a first non-insulating region;
a second insulating layer formed in the second region so as to entirely cover the second metal electrode layer except for a second non-insulating region;
a first contact electrode formed in the first non-insulating region;
a second contact electrode formed in the second non-insulating region;
Equipped with
the first metal electrode layer and the second metal electrode layer include copper;
The first non-insulating region has the first transparent electrode layer formed therein and the first metal electrode layer not formed therein;
the second transparent electrode layer is formed in the second non-insulating region, and the second metal electrode layer is not formed in the second non-insulating region;
the first contact electrode is in contact with a main surface of the first transparent electrode layer, a side surface of the first metal electrode layer, and a side surface of the first insulating layer;
the second contact electrode is in contact with a main surface of the second transparent electrode layer, a side surface of the second metal electrode layer, and a side surface of the second insulating layer;
Solar cell. The solar cell of claim 5, wherein the first contact electrode and the second contact electrode contain particulate silver. 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, the metal electrode layer material film including copper, on the transparent electrode layer material film;
an insulating layer forming step of forming a first insulating layer that entirely covers the metal electrode layer material film in the first region and a second insulating layer that entirely covers the metal electrode layer material film in the second region, the first insulating layer and the second insulating layer being spaced apart from each other;
a metal electrode layer forming step of forming the first metal electrode layer patterned in the first region by removing exposed portions of the metal electrode layer material film using an etching method with the first insulating layer and the second insulating layer as a mask, forming the second metal electrode layer patterned in the second region, and removing the first insulating layer and the second insulating layer;
a contact electrode layer forming step of forming a first contact electrode layer on the first metal electrode layer and forming a second contact electrode layer on the second metal electrode layer;
a transparent electrode layer forming step of removing exposed portions of the transparent electrode layer material film by an etching method using the first contact electrode layer, the first metal electrode layer, and the second contact electrode layer, and the second metal electrode layer as a mask, thereby forming the first transparent electrode layer patterned in the first region, and forming the second transparent electrode layer patterned in the second region;
A method for manufacturing a solar cell, comprising: The method for manufacturing a solar cell according to claim 7, wherein in the contact electrode layer formation process, the first contact electrode layer and the second contact electrode layer are formed by printing and curing a printing material containing a particulate metal material, a resin material, and a solvent. The method for manufacturing a solar cell according to claim 8, wherein the printing material is a silver paste containing particulate silver material. In the metal electrode layer forming step, a mixed solution of an oxidizing agent and hydrochloric acid is used as an etching solution,
In the transparent electrode layer forming step, hydrochloric acid is used as an etching solution.
The method for producing a solar cell according to any one of claims 7 to 9.

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