Method for manufacturing solar cell and solar cell

Abstract

The present invention provides a solar cell capable of suppressing degradation in performance and reliability of the solar cell even when simplifying the manufacturing process. The solar cell (1) is a back electrode type in which a first semiconductor layer (25) and a first metal electrode layer (29) are formed in a first region, and a second semiconductor layer and a second metal electrode layer are formed in a second region. The solar cell (1) comprises a resin film (41), which is arranged at an end portion on the boundary side between the first region and the second region in the first metal electrode layer (29) (and the second metal electrode layer). The first metal electrode layer (29) (and the second metal electrode layer) comprises a base layer (29l) and a plating layer (29u). The base layer (29l) has a concavo-convex structure corresponding to the concavo-convex structure of the semiconductor substrate (11). The mountain portion of the concavo-convex structure in the base layer (29l) contacts the plating layer (29u). The resin film (41) is sandwiched between the valley portion of the concavo-convex structure at the end portion of the base layer (29l) and the plating layer (29u).

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a back electrode type (back contact type) solar cell and a back electrode type solar cell. Background Art

[0002] There are two types of solar cells using semiconductor substrates: a two-sided electrode type solar cell in which electrodes are formed on both the light-receiving side and the back side, and a back electrode type solar cell in which electrodes are formed only on the back side. In a two-sided electrode type solar cell, since electrodes are formed on the light-receiving side, sunlight is blocked by the electrodes. On the other hand, in a back electrode type solar cell, since no electrodes are formed on the light-receiving side, the sunlight reception rate is higher than that of a two-sided electrode type solar cell. Patent Document 1 discloses a back electrode type solar cell.

[0003] The solar cell described in Patent Document 1 includes a semiconductor substrate, a first-conductivity-type semiconductor layer and a first electrode layer stacked in sequence on the back side of the semiconductor substrate, and a second-conductivity-type semiconductor layer and a second electrode layer stacked in sequence on another portion of the back side of the semiconductor substrate. The first and second electrode layers are separated from each other to prevent short circuits.

[0004] Patent Document 1: Japanese Patent Application Laid-Open No. 2013-131586

[0005] Generally, in order to improve the light trapping effect and / or light recovery efficiency in a semiconductor substrate, a semiconductor substrate has a pyramid-shaped fine concavo-convex structure called a texture structure on the light-receiving surface side and / or the back side.

[0006] In addition, typically, the first electrode layer and the second electrode layer each include a metal electrode layer.

[0007] The inventors of this application proposed using a plating method to form a metal electrode layer with the goal of simplifying the aforementioned solar cell manufacturing process. However, according to the inventors' understanding, in this solar cell manufacturing method, due to the uneven structure on the back side of the semiconductor substrate, during the growth of the metal electrode layer, particularly in the valleys of the uneven structure, the metal electrode layer growing in an oblique direction may squeeze each other, thereby causing cracks in the metal electrode layer.

[0008] If cracks form in the metal electrode layer, for example, the etching solution used to pattern the metal electrode layer can seep into the cracks, damaging the semiconductor layer. This can lead to decreased performance and reliability of the solar cell. Summary of the Invention

[0009] An object of the present invention is to provide a method for manufacturing a solar cell and a solar cell, which can suppress degradation in performance and reliability of the solar cell while simplifying the manufacturing process.

[0010] The manufacturing method of the solar cell of the present invention is a manufacturing method of a back electrode type solar cell, which comprises: a semiconductor substrate having a concave-convex structure on one main surface side, a first conductive type semiconductor layer and a first metal electrode layer sequentially stacked on a first region which is a part of the above-mentioned one main surface side of the semiconductor substrate, and a second conductive type semiconductor layer and a second metal electrode layer sequentially stacked on a second region which is another part of the above-mentioned one main surface side of the semiconductor substrate. The manufacturing method of the solar cell is characterized in that the above-mentioned solar cell comprises a resin film, and the above-mentioned resin film is arranged on the end portion on the boundary side of at least the first region and the second region of each of the above-mentioned first metal electrode layer and the above-mentioned second metal electrode layer, and the above-mentioned first metal electrode layer and the above-mentioned second metal electrode layer respectively have a base layer and a plating layer. The manufacturing method of the solar cell comprises: forming a base layer material film A process, in which a series of material films of the above-mentioned base layer are formed on the above-mentioned first conductive type semiconductor layer and the above-mentioned second conductive type semiconductor layer on the above-mentioned one main surface side of the above-mentioned semiconductor substrate in a manner spanning the above-mentioned first region and the above-mentioned second region; a resist forming process, in which a resist is formed on the material film of the above-mentioned base layer at the boundary between the above-mentioned first region and the above-mentioned second region; a plating layer forming process, in which a plating method using the above-mentioned resist as a mask is used to form the patterned plating layer on the material film of the above-mentioned base layer in each of the above-mentioned first region and the above-mentioned second region; a resist removing process, in which the above-mentioned resist is removed; and a base layer forming process, in which an etching method using the above-mentioned plating layer as a mask is used to etch the material film of the above-mentioned base layer, thereby forming the patterned base layer in the above-mentioned first region and the above-mentioned second region, respectively. In the above-mentioned base layer material film forming process, a material film of the above-mentioned base layer having a concave-convex structure corresponding to the above-mentioned concave-convex structure of the above-mentioned semiconductor substrate is formed. In the above-mentioned resist forming process, a pattern printing method is used to print a printing material containing a resin material and a solvent and solidify it to form the patterned resist. As a result, the above-mentioned resin film formed by the seeping of the above-mentioned resin material is arranged in the valley portion of the above-mentioned concave-convex structure in the above-mentioned at least end portion of the above-mentioned base layer. In the above-mentioned plating layer forming process, the above-mentioned plating layer is formed on the above-mentioned resin film at the valley portion of the above-mentioned concave-convex structure in the above-mentioned at least end portion of the above-mentioned base layer and on the mountain portion of the above-mentioned concave-convex structure in the above-mentioned base layer.

[0011] The solar cell of the present invention is a back electrode type solar cell, which comprises: a semiconductor substrate having a concave-convex structure on one main surface side, a first conductive semiconductor layer and a first metal electrode layer sequentially stacked on a first region which is a part of the above-mentioned one main surface side of the semiconductor substrate, and a second conductive semiconductor layer and a second metal electrode layer sequentially stacked on a second region which is another part of the above-mentioned one main surface side of the semiconductor substrate. The solar cell is characterized in that it comprises a resin film, the resin film is arranged at the end portion on the boundary side of at least the first region and the second region of each of the above-mentioned first metal electrode layer and the above-mentioned second metal electrode layer, the above-mentioned first metal electrode layer and the above-mentioned second metal electrode layer respectively have a base layer and a plating layer, the above-mentioned base layer has a concave-convex structure corresponding to the above-mentioned concave-convex structure of the above-mentioned semiconductor substrate, the mountain portion of the above-mentioned concave-convex structure in the above-mentioned base layer is in contact with the above-mentioned plating layer, and the above-mentioned resin film is sandwiched between the valley portion of the above-mentioned concave-convex structure in the above-mentioned at least end portion of the above-mentioned base layer and the above-mentioned plating layer.

[0012] Another solar cell of the present invention is a back electrode type solar cell, which comprises: a semiconductor substrate having a concave-convex structure on one main surface side, a first conductive semiconductor layer and a first metal electrode layer sequentially stacked on a first region which is a part of the above-mentioned one main surface side of the above-mentioned semiconductor substrate, and a second conductive semiconductor layer and a second metal electrode layer sequentially stacked on a second region which is another part of the above-mentioned one main surface side of the above-mentioned semiconductor substrate. The solar cell is characterized in that the above-mentioned first metal electrode layer and the above-mentioned second metal electrode layer respectively have a base layer and a plating layer, the above-mentioned base layer has a concave-convex structure corresponding to the above-mentioned concave-convex structure of the above-mentioned semiconductor substrate, the mountain part of the above-mentioned concave-convex structure in the above-mentioned base layer is in contact with the above-mentioned plating layer, and in the end part on the boundary side of at least the above-mentioned first region and the above-mentioned second region of each of the above-mentioned first metal electrode layer and the above-mentioned second metal electrode layer, there is a space under the above-mentioned plating layer at the valley part of the above-mentioned concave-convex structure.

[0013] According to the present invention, even if the manufacturing process of a solar cell is simplified, it is possible to suppress degradation in performance and reliability of the solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a diagram of the solar cell according to this embodiment as viewed from the back side.

[0015] Figure 2 yes Figure 1 A cross-sectional view taken along line II-II of the solar cell shown.

[0016] Figure 3 yes Figure 2An enlarged cross-sectional view of portion III of the solar cell is shown.

[0017] Figure 4A It is a diagram showing a semiconductor layer forming step in the method for manufacturing a solar cell according to this embodiment.

[0018] Figure 4B It is a diagram showing a transparent electrode layer material film forming step and a base layer material film forming step of a metal electrode layer in the method for manufacturing a solar cell according to the present embodiment.

[0019] Figure 4C It is a diagram showing a resist forming step in the method for manufacturing a solar cell according to this embodiment.

[0020] Figure 4D It is a diagram showing a process of forming a plating layer of a metal electrode layer in the method for manufacturing a solar cell according to the present embodiment.

[0021] Figure 4E It is a diagram showing a resist removal step in the method for manufacturing a solar cell according to this embodiment.

[0022] Figure 4F These are diagrams showing a transparent electrode layer forming step and a base layer forming step of a metal electrode layer in the method for manufacturing a solar cell according to the present embodiment.

[0023] Figure 5 yes Figure 4C and Figure 4D An enlarged cross-sectional view of a portion V in the resist forming step and the plating layer forming step of the metal electrode layer in the method for manufacturing a solar cell shown.

[0024] Figure 6 The diagrams are for explaining problems in the process of forming a plating layer of a metal electrode layer in a method of manufacturing a solar cell using a conventional plating method (subtractive method).

[0025] Figure 7A yes Figure 3 The partially enlarged cross-sectional view of the solar cell of this embodiment is shown, and is equivalent to Figure 2 An enlarged cross-sectional view of portion III is shown.

[0026] Figure 7B This is a partially enlarged cross-sectional view of a solar cell according to a modified example of the present embodiment, and is equivalent to Figure 2 An enlarged cross-sectional view of portion III is shown.

[0027] Figure 7C This is a partially enlarged cross-sectional view of a solar cell according to a modified example of the present embodiment, and is equivalent to Figure 2An enlarged cross-sectional view of portion III is shown.

[0028] Figure 7D This is a partially enlarged cross-sectional view of a solar cell according to a modified example of the present embodiment, and is equivalent to Figure 2 An enlarged cross-sectional view of portion III is shown. DETAILED DESCRIPTION

[0029] Hereinafter, an example of an embodiment of the present invention will be described with reference to the accompanying drawings. In the drawings, identical or corresponding parts are denoted by the same reference numerals. For convenience, hatching or component reference numerals may be omitted. In such cases, reference may be made to other drawings.

[0030] (Solar Cell)

[0031] Figure 1 This is a diagram showing the solar cell of this embodiment as viewed from the back side. Figure 2 yes Figure 1 The II-II line cross-sectional view of the solar cell shown. Figure 3 yes Figure 2 An enlarged cross-sectional view of portion III of the solar cell is shown. Figures 1 to 3 The solar cell 1 shown is a back electrode type (also referred to as a back contact type or a back junction type) and a heterojunction type solar cell.

[0032] The solar cell 1 includes a semiconductor substrate 11 having two main surfaces, and the main surfaces of the semiconductor substrate 11 include a first region 7 and a second region 8. Hereinafter, the main surface of the semiconductor substrate 11 on the side receiving light is referred to as the light-receiving surface, and the main surface (one main surface) opposite to the light-receiving surface is referred to as the back surface.

[0033] The first region 7 is formed in a so-called comb-like shape and includes a plurality of fingers 7f corresponding to the teeth of the comb, and a busbar portion 7b corresponding to the supporting portion of the teeth of the comb. The busbar portion 7b extends in a first direction (X direction) along one side of the semiconductor substrate 11, and the fingers 7f extend from the busbar portion 7b in a second direction (Y direction) intersecting the first direction.

[0034] Similarly, the second region 8 has a so-called comb-like shape and includes a plurality of fingers 8f corresponding to the teeth of the comb and a busbar portion 8b corresponding to the supporting portion of the teeth of the comb. The busbar portion 8b extends in the first direction (X direction) along the other side of the semiconductor substrate 11 that is opposite to the other side, and the fingers 8f extend from the busbar portion 8b in the second direction (Y direction).

[0035] The fingers 7f and 8f are formed in stripes extending in the second direction (Y direction) and are alternately arranged in the first direction (X direction). In addition, the first region 7 and the second region 8 may be formed in stripes.

[0036] like Figure 2 As shown, the solar cell 1 includes a passivation layer 13 and an optical adjustment layer 15 stacked in this order on the light-receiving surface side of the semiconductor substrate 11. Furthermore, the solar cell 1 includes a passivation layer 23, a first-conductivity-type semiconductor layer 25, and a first electrode layer 27 stacked in this order on a portion (first region 7) of the back side of the semiconductor substrate 11. Furthermore, the solar cell 1 includes a passivation layer 33, a second-conductivity-type semiconductor layer 35, and a second electrode layer 37 stacked in this order on another portion (second region 8) of the back side of the semiconductor substrate 11.

[0037] 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 an n-type dopant is doped in the crystalline silicon material. In addition, the semiconductor substrate 11 may also be, for example, a p-type semiconductor substrate in which a p-type dopant is doped in the crystalline silicon material. As an n-type dopant, phosphorus (P) can be cited, for example. As a p-type dopant, boron (B) can be cited, for example. The semiconductor substrate 11 functions as a photoelectric conversion substrate that absorbs incident light from the light-receiving side and generates photocarriers (electrons and holes).

[0038] By using crystalline silicon as the material of the semiconductor substrate 11 , a relatively high output (stable output regardless of illumination) can be obtained even when dark current is relatively small and the intensity of incident light is low.

[0039] The semiconductor substrate 11 has a pyramid-shaped fine concavo-convex structure called a texture structure on the back side, thereby improving the efficiency of recovering light that passes through the semiconductor substrate 11 without being absorbed.

[0040] The semiconductor substrate 11 may also have a pyramid-shaped fine concavo-convex structure called a texture structure on the light-receiving surface side. This reduces reflection of incident light on the light-receiving surface, thereby improving the light trapping effect in the semiconductor substrate 11.

[0041] Passivation layer 13 is formed on the light-receiving surface of semiconductor substrate 11. Passivation layer 23 is formed in first region 7 on the back side of semiconductor substrate 11. Passivation layer 33 is formed in second region 8 on the back side of semiconductor substrate 11. Passivation layers 13, 23, and 33 are formed, for example, from a material primarily composed of intrinsic (i-type) amorphous silicon. Passivation layers 13, 23, and 33 inhibit the recombination of carriers generated in semiconductor substrate 11, thereby improving carrier recovery efficiency.

[0042] The optical adjustment layer 15 is formed on the passivation layer 13 on the light-receiving surface of the semiconductor substrate 11. The optical adjustment layer 15 functions as an antireflection layer that prevents reflection of incident light and as a protective layer that protects the light-receiving surface 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 silicon oxynitride (SiON), or a composite thereof.

[0043] The first-conductivity-type semiconductor layer 25 is formed on the passivation layer 23, that is, in the first region 7 on the back side of the semiconductor substrate 11. Meanwhile, the second-conductivity-type semiconductor layer 35 is formed on the passivation layer 33, that is, in the second region 8 on the back side of the semiconductor substrate 11. Specifically, the first-conductivity-type semiconductor layer 25 and the second-conductivity-type semiconductor layer 35 form a strip-like shape extending in the Y direction. The first-conductivity-type semiconductor layer 25 and the second-conductivity-type semiconductor layer 35 are arranged alternately in the X direction. A portion of the second-conductivity-type semiconductor layer 35 may overlap a portion of an adjacent first-conductivity-type semiconductor layer 25 (not shown).

[0044] The first conductive type semiconductor layer 25 is formed of, for example, an amorphous silicon material and is a p-type semiconductor layer obtained by doping an amorphous silicon material with a p-type dopant (for example, boron (B) as described above).

[0045] The second conductive type semiconductor layer 35 is formed of, for example, an amorphous silicon material. For example, the second conductive type semiconductor layer 35 is an n-type semiconductor layer obtained by doping the amorphous silicon material with an n-type dopant (for example, phosphorus (P) as described above). Alternatively, 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.

[0046] The first electrode layer 27 is formed on the first-conductivity-type semiconductor layer 25, that is, in the first region 7 on the back side of the semiconductor substrate 11. Meanwhile, the second electrode layer 37 is formed on the second-conductivity-type semiconductor layer 35, that is, in the second region 8 on the back side of the semiconductor substrate 11. Specifically, the first and second electrode layers 27 and 37 form strip-like shapes and extend in the Y direction. The first and second electrode layers 27 and 37 are alternately arranged in the X direction.

[0047] The first electrode layer 27 includes a first transparent electrode layer 28 and a first metal electrode layer 29 sequentially stacked on the first conductive semiconductor layer 25. Meanwhile, the second electrode layer 37 includes a second transparent electrode layer 38 and a second metal electrode layer 39 sequentially stacked on the second conductive semiconductor layer 35. The first metal electrode layer 29 has a two-layer structure consisting of a base layer 291 and a plating layer 29u, while the second metal electrode layer 39 has a two-layer structure consisting of a base layer 391 and a plating layer 39u.

[0048] 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) and ZnO (Zinc Oxide: zinc oxide).

[0049] Base layer 291 in first metal electrode layer 29 and base layer 391 in second metal electrode layer 39 are made of a metal material such as silver, copper, or aluminum, formed using a PVD method such as sputtering deposition. On the other hand, plating layer 29u in first metal electrode layer 29 and plating layer 39u in second metal electrode layer 39 are made of a metal material such as silver, copper, or nickel, formed using a plating method.

[0050] The first electrode layer 27 and the second electrode layer 37 form strips extending along the second direction (Y direction) and are arranged alternately in the first direction (X direction). That is, the first transparent electrode layer 28 and the second transparent electrode layer 38 form strips extending along the second direction (Y direction) and are arranged alternately in the first direction (X direction). Furthermore, the first metal electrode layer 29 and the second metal electrode layer 39 form strips extending along the second direction (Y direction) and are arranged alternately in the first direction (X direction). The first transparent electrode layer 28 and the second transparent electrode layer 38 are separated from each other, and the first metal electrode layer 29 and the second metal electrode layer 39 are also separated from each other.

[0051] like Figure 3 As shown, the resin film 41 is unevenly distributed at least at the end portion on the boundary side between the first region 7 and the second region 8 between the base layer 291 and the plating layer 29u in the first metal electrode layer 29 .

[0052] Specifically, the base layer 291 is relatively thin and has a concavo-convex structure that corresponds to the concavo-convex structure (texture) of the semiconductor substrate 11. A resin film 41 is interposed between the valleys of the concavo-convex structure at least at the end of the base layer 291 and the plating layer 29u. The resin film 41 can be formed in a sea-like shape (i.e., continuous) or in an island-like shape (i.e., discontinuous) of an island-like structure. The valleys of the concavo-convex structure at least at the end of the base layer 291 are preferably flattened by the resin film 41.

[0053] Meanwhile, at least the peaks of the concavo-convex structure at the end of the base layer 291 are in contact with the plating layer 29u. Also, the valleys and peaks of the concavo-convex structure of the base layer 291 excluding the end are in contact with the plating layer 29u.

[0054] Likewise, the resin film 41 is unevenly distributed at least at the end portion on the boundary side between the first region 7 and the second region 8 between the base layer 39 l and the plating layer 39 u in the second metal electrode layer 39 .

[0055] Specifically, the base layer 391 is relatively thin and has a concavo-convex structure that corresponds to the concavo-convex structure (texture) of the semiconductor substrate 11. A resin film 41 is interposed between the valleys of the concavo-convex structure at least at the end of the base layer 391 and the plating layer 39u. The resin film 41 can be formed in a sea-like shape (i.e., continuous) or in an island-like shape (i.e., discontinuous) of an island-like structure. The valleys of the concavo-convex structure at least at the end of the base layer 391 are preferably flattened by the resin film 41.

[0056] Meanwhile, at least the peaks of the concavo-convex structure at the end of the base layer 391 are in contact with the plating layer 39u. Also, the valleys and peaks of the concavo-convex structure of the base layer 391 excluding the end are in contact with the plating layer 39u.

[0057] (Method for manufacturing solar cell)

[0058] Next, refer to Figures 4A to 4F , a method for manufacturing the solar cell of this embodiment is described. Figure 4A 1 is a diagram showing a semiconductor layer forming step in a method for manufacturing a solar cell according to this embodiment. Figure 4B : is a diagram showing the transparent electrode layer material film forming step and the base layer material film forming step of the metal electrode layer in the manufacturing method of the solar cell of this embodiment. Figure 4C 1 is a diagram showing a resist forming step in the method for manufacturing a solar cell according to this embodiment. Figure 4D : is a diagram showing a process of forming a plating layer of a metal electrode layer in the method for manufacturing a solar cell according to this embodiment. Figure 4E 1 is a diagram showing a resist removal step in the method for manufacturing a solar cell according to this embodiment. Figure 4F : is a diagram showing the transparent electrode layer forming step and the base layer forming step of the metal electrode layer in the method for manufacturing a solar cell according to this embodiment. Figures 4A to 4F , the back surface side of the semiconductor substrate 11 is shown, and the front surface side of the semiconductor substrate 11 is omitted.

[0059] First, if Figure 4A As shown, a passivation layer 23 and a first conductive type semiconductor layer 25 are formed on a portion of the back side of the semiconductor substrate 11, specifically in the first region 7 (semiconductor layer forming step). For example, a passivation layer material film and a first 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 23 and the first conductive type semiconductor layer 25 may be patterned using an etching method using a resist or a metal mask produced using a photolithography technique or a printing technique.

[0060] In addition, as an etching solution for the p-type semiconductor layer material film, for example, an acidic solution such as hydrofluoric acid containing ozone, or a mixture of nitric acid and hydrofluoric acid can be cited, and as an etching solution for the n-type semiconductor layer material film, for example, an alkaline solution such as an aqueous potassium hydroxide solution can be cited.

[0061] Alternatively, when stacking the passivation layer and the first conductivity type semiconductor layer on the back side of the semiconductor substrate 11 using CVD or PVD, the passivation layer 23 and the first conductivity type semiconductor layer 25 may be formed and patterned simultaneously using a mask.

[0062] Next, a passivation layer 33 and a second conductive type semiconductor layer 35 are formed on another portion of the back side of the semiconductor substrate 11, specifically in the second region 8 (semiconductor layer formation step). For example, similarly to the 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 CVD or PVD, and then the passivation layer 33 and the second conductive type semiconductor layer 35 may be patterned using an etching method using a resist or a metal mask produced using photolithography or printing technology.

[0063] Alternatively, when the passivation layer and the second conductivity type semiconductor layer are stacked on the back side of the semiconductor substrate 11 using CVD or PVD, the passivation layer 33 and the second conductivity type semiconductor layer 35 may be formed and patterned simultaneously using a mask.

[0064] In addition, in this semiconductor layer forming step, a passivation layer 13 (not shown) may be formed on the entire surface of the light-receiving surface side of the semiconductor substrate 11 .

[0065] Next, if Figure 4B As shown, a series of transparent electrode layer material films 28Z are formed on the first conductive type semiconductor layer 25 and the second conductive type semiconductor layer 35 so as to span the first region 7 and the second region 8 (transparent electrode layer material film forming step). The transparent electrode layer material film 28Z is formed using, for example, a CVD method or a PVD method.

[0066] Next, a series of base material films 291Z are formed on the transparent electrode layer material film 28Z, that is, on the first conductive type semiconductor layer 25 and the second conductive type semiconductor layer 35, so as to span the first region 7 and the second region 8 (base material film forming step). The base material film 291Z can be formed using a PVD method such as sputtering deposition, for example.

[0067] Then, if Figure 4CAs shown, a resist 40 is formed on the base layer material film 291Z at the boundary between the first region 7 and the second region 8 (resist forming step). Examples of methods for forming the resist 40 include pattern printing methods such as screen printing or extrusion printing such as gravure printing, or discharge printing such as inkjet printing.

[0068] In the pattern printing method, a printing material containing a resin material and a solvent is printed and sintered (cured) to form a patterned resist 40. Figure 5 As shown, a resin film 41 formed by the seeping of the resin material in the printed material is formed in the valley portion of the concavo-convex structure (texture structure) of the base layer material film 291Z.

[0069] The resin film 41 may be Figure 5 The valleys of all the concavo-convex structures formed between the resists 40, that is, formed in the first region 7 and the second region 8, may also be formed as shown in FIG. Figure 3 The valley portion of the concavo-convex structure is formed at the end portion on the boundary side between the first region 7 and the second region 8 between the resist 40 .

[0070] Next, if Figure 4D As shown, a plating method using a resist 40 as a mask is used to form a patterned plating layer 29u on the base material film 29lZ in the first region 7, and a patterned plating layer 39u is formed on the base material film 29lZ in the second region 8 (plating metal electrode layer forming step). Specifically, as shown in FIG. Figure 5 As shown, the plating layer 29u is formed on the resin film 41 at least in the valleys of the concavo-convex structure in the end portion of the base material film 291Z and on the peaks of the concavo-convex structure in the base material film 291Z.

[0071] Then, if Figure 4E As shown, the resist 40 is removed (resist removal step). As the resist removal solution, an alkaline aqueous solution such as a sodium hydroxide aqueous solution is used.

[0072] Next, if Figure 4FAs shown, the base layer material film 291Z and the transparent electrode layer material film 28Z are etched using an etching method using the plating layer 29u and the plating layer 39u as masks, thereby forming a patterned first transparent electrode layer 28 and a base layer 291 in the first region 7, and forming a patterned second transparent electrode layer 38 and a base layer 391 in the second region 8 (transparent electrode layer formation step and base layer formation step). Thus, the first metal electrode layer 29 composed of the base layer 291 and the plating layer 29u, and the second metal electrode layer 39 composed of the base layer 391 and the plating layer 39u are formed. Furthermore, the first electrode layer 27 composed of the first transparent electrode layer 28 and the first metal electrode layer 29, and the second electrode layer 37 composed of the second transparent electrode layer 38 and the second metal electrode layer 39 are formed.

[0073] As an etching solution for simultaneously etching the base layer material film 29lZ and the transparent electrode layer material film 28Z, for example, when the transparent electrode layer material film 28Z is ITO and the base layer material film 29lZ is copper, a mixed solution of an oxidizing agent such as ammonium persulfate (ammonium peroxydisulfate) and an acidic solution such as hydrochloric acid (HCl) can be cited.

[0074] Here, the method of forming a plating layer on a relatively thin base layer is also called a subtractive method. In such a subtractive method, instead of the above-mentioned resist forming step, plating layer forming step and resist removing step ( Figure 4C to Figure 4E ), after forming a series of plating layers, the plating layers are patterned using a resist. Since the base layer is relatively thin, the base layer has a concave-convex structure corresponding to the concave-convex structure (texture structure) of the semiconductor substrate. Therefore, Figure 6 As shown, when the plating layer 29u grows on the base material film 29lZ, the plating layers growing obliquely, particularly in the valleys of the concavo-convex structure, squeeze each other (see arrows), and cracks may occur in the plating layer.

[0075] If cracks form in the plating layer, for example, the etching solution used to pattern the metal electrode layer and the transparent electrode layer can seep into the cracks, dissolving the base layer material film and the transparent electrode layer material film, causing damage to the semiconductor layer. In particular, the crystal grains in thin base layer films are small and relatively easy to dissolve in acidic solutions such as sulfuric acid. This can lead to reduced performance and reliability of the solar cell.

[0076] In this regard, in this embodiment, if Figure 5As shown, in the resist forming process, a resin film 41 that is exuded from the resist 40 is arranged in the valley of the concavo-convex structure of the base layer material film 29lZ. In addition, the valley of the concavo-convex structure of the base layer material film 29lZ is preferably flattened (smoothed) by the resin film 41. Thus, when the plating layer 29u grows on the base layer material film 29lZ, the plating layers that grow in an oblique direction, especially in the valley of the concavo-convex structure, are suppressed from squeezing each other, thereby suppressing the generation of cracks in the plating layer. Thus, damage to the semiconductor layer caused by, for example, the etching solution used for patterning the metal electrode layer and the transparent electrode layer immersing in the cracks of the plating layer can be suppressed. Therefore, the decline in the performance of the solar cell can be suppressed. In addition, the decline in the reliability of the solar cell can be suppressed.

[0077] After that, an optical adjustment layer 15 (not shown) is formed on the entire surface of the light-receiving surface of the semiconductor substrate 11. Figure 1 and Figure 2 A back electrode type solar cell 1 according to the present embodiment is shown.

[0078] As described above, according to the method for manufacturing a solar cell of this embodiment, the metal electrode layers 29 and 39 are formed using the plating method. This simplifies the manufacturing process of the solar cell and reduces the cost.

[0079] In addition, according to the manufacturing method of the solar cell of the present embodiment, in the plating method, a resist 40 obtained by printing a printed material containing a resin material and a solvent using a pattern printing method and sintering (curing) is used to directly (film forming and patterning are performed simultaneously) form the plating layer 29u. As a result, a resin film 41 that oozes out from the printed material is arranged in the valley portion of the concave-convex structure of the base layer material film 29lZ. In addition, the valley portion of the concave-convex structure of the base layer material film 29lZ is preferably flattened (smoothed) by the resin film 41. As a result, the generation of cracks in the plating layer can be suppressed, thereby suppressing the damage to the semiconductor layer caused by the cracks in the plating layer. Therefore, the performance degradation of the solar cell can be suppressed. In addition, the degradation of the reliability of the solar cell can be suppressed.

[0080] Furthermore, according to the solar cell manufacturing method of this embodiment, a relatively inexpensive metal such as Cu can be used as the material for the metal electrode layers 29 and 39 instead of the relatively expensive, conventional Ag paste (for example, by forming a film using a PVD method such as sputtering deposition and then performing wet etching). This allows for a lower cost solar cell.

[0081] Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and various changes and modifications can be made. For example, in the above embodiments, Figure 3As shown in FIG, a solar cell is shown in which the resin film 41 is unevenly distributed in the valleys of the concavo-convex structure between the base layer 29l and the plating layer 29u in the first metal electrode layer 29, and between the base layer 39l and the plating layer 39u in the second metal electrode layer 39. However, the present invention is not limited to this, and various types of solar cells can be considered depending on the degree of etching in the manufacturing process of the solar cell. Here, for comparison with the comparative example of the solar cell described below, Figure 3 The partially enlarged cross-sectional view of the solar cell of this embodiment is shown, Figure 2 The enlarged cross-sectional view of the portion III shown is reproduced in Figure 7A In. Figure 7A In Figure 3 The first conductive type semiconductor layer 25 and the passivation layer 23 are shown together. Figures 7B to 7D This is a partial enlarged cross-sectional view of a solar cell according to a modified example of the present embodiment, which is equivalent to Figure 2 An enlarged cross-sectional view of portion III is shown.

[0082] like Figure 7B As shown, in solar cell 1, resin film 41 unevenly distributed in the valleys of the concavo-convex structure between base layer 291 and plating layer 29u in first metal electrode layer 29 and between base layer 391 and plating layer 39u in second metal electrode layer 39 may be removed by etching. For example, resin film 41 is removed by etching in the resist removal step described above.

[0083] Thus, in solar cell 1, a space may be present below plating layer 29u in the valley of the concavo-convex structure at least in the end portion of first metal electrode layer 29 on the boundary side between first region 7 and second region 8. More specifically, base layer 29l may be present below plating layer 29u in the valley of the concavo-convex structure at least in the end portion of first metal electrode layer 29, and a space may be provided between base layer 29l and plating layer 29u in the valley of the concavo-convex structure instead of resin film 41.

[0084] Similarly, in solar cell 1, a space may be present below plating layer 39u in the valley of the concavo-convex structure at least in the end portion of second metal electrode layer 39 on the boundary side between first region 7 and second region 8. More specifically, base layer 39l may be present below plating layer 39u in the valley of the concavo-convex structure at least in the end portion of second metal electrode layer 39, and a space may be provided between base layer 39l and plating layer 39u in the valley of the concavo-convex structure instead of resin film 41.

[0085] Or, as Figure 7CAs shown, in the solar cell 1, the base layers 291 and 391 may be further removed by etching, and the transparent electrode layers 28 and 38 may be further removed by etching. For example, in the transparent electrode layer forming step and the base layer forming step described above, the base layers 291 and 391 and the transparent electrode layers 28 and 38 are removed by etching.

[0086] Thus, in the solar cell 1, the resin film 41 and the base layer 291 may not exist below the plating layer 29u in the valleys of the concavo-convex structure at least at the end portion of the first metal electrode layer 29, but a space may exist. Alternatively, in the solar cell 1, the resin film 41, the base layer 291, and the transparent electrode layer 28 may not exist below the plating layer 29u in the valleys of the concavo-convex structure at least at the end portion of the first metal electrode layer 29, but a space may exist.

[0087] Similarly, in solar cell 1, resin film 41 and base layer 391 may not exist below plating layer 39u in the valleys of the concavo-convex structure at least at the end portions of second metal electrode layer 39, but a space may exist. Alternatively, in solar cell 1, resin film 41, base layer 391, and transparent electrode layer 38 may not exist below plating layer 39u in the valleys of the concavo-convex structure at least at the end portions of second metal electrode layer 39, but a space may exist.

[0088] Or, as Figure 7D As shown, in solar cell 1, resin film 41 may be left without being etched, and base layers 291 and 391 may be removed by etching. Alternatively, transparent electrode layers 28 and 38 may be removed by etching, where resin film 41 is unevenly distributed in the valleys of the concavo-convex structure between base layer 291 and plating layer 29u in first metal electrode layer 29 and between base layer 391 and plating layer 39u in second metal electrode layer 39. As described above, for example, in the transparent electrode layer forming step and the base layer forming step, base layers 291 and 391 and transparent electrode layers 28 and 38 are removed by etching.

[0089] Thus, in the solar cell 1, the resin film 41 may be present below the plating layer 29u in the valleys of the concavo-convex structure at least at the end portion of the first metal electrode layer 29, without the base layer 29l, and a space may be present below the resin film 41 in the valleys of the concavo-convex structure. Alternatively, in the solar cell 1, the resin film 41 may be present below the plating layer 29u in the valleys of the concavo-convex structure at least at the end portion of the first metal electrode layer 29, without the base layer 29l and the transparent electrode layer 28, and a space may be present below the resin film 41 in the valleys of the concavo-convex structure.

[0090] Similarly, in the solar cell 1, the resin film 41 may be present below the plating layer 39u in the valleys of the concavo-convex structure at at least the end portion of the second metal electrode layer 39, without the base layer 39l, and a space may be present below the resin film 41 in the valleys of the concavo-convex structure. Alternatively, in the solar cell 1, the resin film 41 may be present below the plating layer 39u in the valleys of the concavo-convex structure at at least the end portion of the second metal electrode layer 39, without the base layer 39l and the transparent electrode layer 38, and a space may be present below the resin film 41 in the valleys of the concavo-convex structure.

[0091] In the above embodiment, a solar cell including an electrode layer including a transparent electrode layer and a metal electrode layer is exemplified. However, the present invention is not limited thereto and is also applicable to a solar cell including an electrode layer including only a metal electrode layer.

[0092] In the above embodiment, the solar cell 1 is exemplified as being made of crystalline silicon, but the present invention is not limited thereto. For example, various materials such as gallium arsenide (GaAs) may be used as the material of the solar cell.

[0093] In addition, in the above-mentioned embodiment, Figure 2 The example shown is a heterojunction solar cell 1. However, the present invention is not limited thereto, and is applicable to various solar cells such as a homojunction solar cell.

[0094] Description of Reference Numerals

[0095] 1…solar cell; 7…first region; 7f…finger; 7b…busbar; 8…second region; 8f…finger; 8b…busbar; 11…semiconductor substrate; 13, 23, 33…passivation layer; 15…optical adjustment layer; 25…first conductive semiconductor layer; 27…first electrode layer; 28…first transparent electrode layer; 28Z…transparent electrode layer material film; 29…first metal electrode layer; 29l…base layer; 29lZ…base layer material film; 29u…plating layer; 35…second conductive semiconductor layer; 37…second electrode layer; 38…second transparent electrode layer; 39…second metal electrode layer; 39l…base layer; 39u…plating layer; 40…resist; 41…resin film.

Claims

1. A solar cell, which is a back electrode type solar cell, The back electrode type solar cell comprises: a semiconductor substrate having a pyramid-shaped fine texture structure on one main surface side; a first conductive type semiconductor layer and a first metal electrode layer sequentially stacked on a first region which is a portion of the one main surface side of the semiconductor substrate; and a second conductive type semiconductor layer and a second metal electrode layer sequentially stacked on a second region which is another portion of the one main surface side of the semiconductor substrate. The solar cell is characterized in that A resin film is provided, the resin film being arranged at an end portion on a boundary side between at least the first region and the second region of each of the first metal electrode layer and the second metal electrode layer, The first metal electrode layer and the second metal electrode layer respectively include a base layer and a plating layer. The base layer has a pyramid-shaped fine texture structure corresponding to the pyramid-shaped fine texture structure of the semiconductor substrate. The mountain portion of the pyramid-shaped fine texture structure in the base layer is in contact with the plating layer. The resin film is interposed between the plated layer and the valley portion of the pyramid-shaped fine texture structure at least in the end portion of the base layer.

2. The solar cell according to claim 1, wherein The valley portion of the pyramid-shaped fine texture structure of the base layer, excluding the end portion, is in contact with the plating layer.

3. The solar cell according to claim 1, wherein The first metal electrode layer and the second metal electrode layer each contain copper as a main component.

4. The solar cell according to any one of claims 1 to 3, wherein Further possess: a first transparent electrode layer, the first transparent electrode layer being stacked between the first conductive semiconductor layer and the first metal electrode layer in the first region; and A second transparent electrode layer is stacked between the second conductive semiconductor layer and the second metal electrode layer in the second region.

5. A solar cell, which is a back electrode type solar cell, The back electrode type solar cell comprises: a semiconductor substrate having a pyramid-shaped fine texture structure on one main surface side; a first conductive type semiconductor layer and a first metal electrode layer sequentially stacked on a first region which is a portion of the one main surface side of the semiconductor substrate; and a second conductive type semiconductor layer and a second metal electrode layer sequentially stacked on a second region which is another portion of the one main surface side of the semiconductor substrate. The solar cell is characterized in that The first metal electrode layer and the second metal electrode layer respectively include a base layer and a plating layer. The base layer has a pyramid-shaped fine texture structure corresponding to the pyramid-shaped fine texture structure of the semiconductor substrate. The mountain portion of the pyramid-shaped fine texture structure in the base layer is in contact with the plating layer. In at least the end portion of each of the first metal electrode layer and the second metal electrode layer on the boundary side between the first region and the second region, a space exists below the plating layer at the valley portion of the pyramid-shaped fine texture structure.

6. The solar cell according to claim 5, characterized in that In at least the end portion, The base layer exists below the plating layer at the valley portion of the pyramid-shaped fine texture structure. The resin film is not interposed between the base layer and the plating layer at the valley portion of the pyramid-shaped fine texture structure, but the space is interposed.

7. The solar cell according to claim 5, characterized in that At least in the end portion, the resin film and the base layer do not exist below the plating layer at the valley portion of the pyramid-shaped fine texture structure, but the space exists.

8. The solar cell according to claim 5, characterized in that In at least the end portion, A resin film exists under the plating layer at the valley portion of the pyramid-shaped fine texture structure. The space exists under the resin film at the valley portion of the pyramid-shaped fine texture structure.

9. The solar cell according to claim 8, characterized in that At least in the end portion, the base layer does not exist below the plating layer in the valley portion of the pyramid-shaped fine texture structure.

10. The solar cell according to claim 7, wherein further comprising a transparent electrode layer, the transparent electrode layer being stacked between the first conductive type semiconductor layer and the first metal electrode layer in the first region, and between the second conductive type semiconductor layer and the second metal electrode layer in the second region, At least in the end portion, the transparent electrode layer does not exist below the plating layer in the valley portion of the pyramid-shaped fine texture structure.

11. The solar cell according to claim 9, wherein further comprising a transparent electrode layer, the transparent electrode layer being stacked between the first conductive type semiconductor layer and the first metal electrode layer in the first region, and between the second conductive type semiconductor layer and the second metal electrode layer in the second region, At least in the end portion, the transparent electrode layer does not exist below the plating layer in the valley portion of the pyramid-shaped fine texture structure.

12. The solar cell according to any one of claims 5 to 11, characterized in that The base layer is in contact with the plating layer at the valley portion of the pyramid-shaped fine texture structure except for at least the end portion.

13. The solar cell according to any one of claims 5 to 11, characterized in that The first metal electrode layer and the second metal electrode layer each contain copper as a main component.

14. A method for manufacturing a solar cell, which is a method for manufacturing a back electrode type solar cell. The back electrode type solar cell comprises: a semiconductor substrate having a pyramid-shaped fine texture structure on one main surface side; a first conductive type semiconductor layer and a first metal electrode layer sequentially stacked on a first region which is a portion of the one main surface side of the semiconductor substrate; and a second conductive type semiconductor layer and a second metal electrode layer sequentially stacked on a second region which is another portion of the one main surface side of the semiconductor substrate. The method for manufacturing a solar cell is characterized in that: The solar cell includes a resin film disposed at at least an end portion of each of the first metal electrode layer and the second metal electrode layer on a boundary side between the first region and the second region. The first metal electrode layer and the second metal electrode layer respectively include a base layer and a plating layer. The method for manufacturing the solar cell comprises: a base layer material film forming step of forming a series of base 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 so as to span the first region and the second region; a resist forming step of forming a resist on the material film of the base layer at a boundary between the first region and the second region; a plating layer forming step of forming the patterned plating layer on the base layer material film in each of the first region and the second region by a plating method using the resist as a mask; a resist removal step of removing the resist; as well as a base layer forming step of etching the base layer material film using an etching method using the plating layer as a mask, thereby forming the patterned base layer in the first region and the second region, In the base layer material film forming step, the base layer material film having a pyramid-shaped fine texture structure corresponding to the pyramid-shaped fine texture structure of the semiconductor substrate is formed. In the resist forming step, a printing material containing a resin material and a solvent is printed using a pattern printing method and cured to form the patterned resist, whereby the resin film formed by the resin material seeping out is arranged in the valley portion of the pyramid-shaped fine texture structure at least in the end portion of the base layer. In the plating layer forming step, the plating layer is formed on the resin film at the valleys of the pyramid-shaped fine texture structure in at least the end portion of the base layer and on the peaks of the pyramid-shaped fine texture structure in the base layer.

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