Solar cell and method for manufacturing solar cell

Abstract

To provide a solar cell that reduces white streaks that appear on the periphery of a light-receiving surface side.SOLUTION: A solar cell 1 is a back junction type solar cell including a first conductivity type amorphous silicon thin film 25 formed on the back side of a crystalline silicon substrate 11, and a second conductivity type amorphous silicon thin film 35, in which a passivation thin film 13 and an optical adjustment silicon compound thin film 15 are formed in this order at the central portion on the light receiving surface side of the substrate 11, a silicon compound thin film 15 for optical adjustment is formed at a periphery R1 on the light receiving surface side of the substrate 11, and a silicon compound thin film other than the passivation thin film 13, the first conductivity type amorphous silicon thin film 25, and the silicon compound thin film 15 is not laminated between the substrate 11 and the silicon compound thin film 15 at peripheral edge portion R1 on the light-receiving surface side of the substrate 11.SELECTED DRAWING: Figure 2A

Description

[Technical field]

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

[0002] As a heterojunction solar cell using a crystalline silicon substrate, a back junction solar cell is known in which a p-type silicon thin film and an n-type silicon thin film are formed on the back side opposite the light receiving surface. In this back junction solar cell, since there is no metal electrode on the light receiving surface side, the light receiving surface side is uniformly black, which makes it highly aesthetically pleasing. Patent Document 1 discloses a back junction solar cell.

[0003] The solar cell described in Patent Document 1 includes a crystalline silicon substrate, a first intrinsic amorphous silicon thin film and a first conductive type amorphous silicon thin film (hereinafter also referred to as the first silicon thin film) and a first electrode, which are formed in this order on a portion of the back surface of the substrate, and a second intrinsic amorphous silicon thin film and a second conductive type amorphous silicon thin film (hereinafter also referred to as the second silicon thin film) and a second electrode, which are formed in this order on another portion of the back surface of the substrate. The solar cell also includes a third intrinsic amorphous silicon thin film (hereinafter also referred to as the third silicon thin film or passivation thin film) and an optically adjusting silicon compound thin film, which are formed in this order on the light receiving surface of the substrate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-75526 A Summary of the Invention [Problem to be solved by the invention]

[0005] In general, in the patterning of the first silicon thin film (first patterning) and the patterning of the second silicon thin film (second patterning), a silicon thin film is formed using, for example, a CVD method (chemical vapor deposition method) or a PVD method (physical vapor deposition method) using a vacuum chamber, and then an etching method using a photolithography technique is used. However, the etching method using a photolithography technique requires processes such as photoresist application by spin coating, photoresist drying, photoresist exposure, photoresist development, etching of the amorphous silicon thin film using the photoresist as a mask, and photoresist peeling, making the process complicated.

[0006] In this regard, Patent Document 1 describes a technique for simplifying the patterning process by using a lift-off method that uses a lift-off thin film (sacrificial thin film) in the second patterning.

[0007] Here, when using a vacuum chamber, for example, a CVD method or a PVD method, when depositing the silicon thin film on the back side, the silicon thin film on the back side may wrap around and be deposited on the periphery of the light-receiving side, which may result in white streaks appearing on the periphery of the light-receiving side.

[0008] Such white streaks on the periphery of the light receiving surface side are particularly noticeable when using a lift-off method as described in Patent Document 1. More specifically, white streaks are noticeable when amorphous silicon thin films and silicon compound thin films such as lift-off thin films, which have different refractive indices, are alternately layered.

[0009] An object of the present invention is to provide a solar cell that reduces white streaks that occur on the periphery of the light-receiving surface side, and a method for manufacturing the solar cell. [Means for solving the problem]

[0010] The solar cell according to the present invention is a back-junction solar cell including a crystalline silicon substrate, a first-conductivity-type amorphous silicon thin film deposited in sequence on a portion of the back surface side opposite to the light-receiving surface side of the substrate, and a second-conductivity-type amorphous silicon thin film deposited in sequence on another portion of the back surface side of the substrate. A passivation thin film and an optically adjusting silicon compound thin film are deposited in sequence on the central portion of the light-receiving surface side of the substrate. The optically adjusting silicon compound thin film is deposited on the peripheral portion of the light-receiving surface side of the substrate. In the peripheral portion of the light-receiving surface side of the substrate, no silicon compound thin films other than the passivation thin film, the first-conductivity-type amorphous silicon thin film, and the optically adjusting silicon compound thin film are stacked between the substrate and the optically adjusting silicon compound thin film.

[0011] Another solar cell according to the present invention is a back-junction solar cell including a crystalline silicon substrate, a first intrinsic amorphous silicon thin film and a first conductive type amorphous silicon thin film deposited in sequence on a portion of the back surface side opposite to the light receiving surface side of the substrate, and a second intrinsic amorphous silicon thin film and a second conductive type amorphous silicon thin film deposited in sequence on another portion of the back surface side of the substrate. A third intrinsic amorphous silicon thin film and an optical adjustment silicon compound thin film are deposited in sequence in the center of the light receiving surface side of the substrate. The optical adjustment silicon compound thin film is deposited on the peripheral portion of the light receiving surface side of the substrate. In the peripheral portion of the light receiving surface side of the substrate, no silicon compound thin films other than the third intrinsic amorphous silicon thin film, the first intrinsic amorphous silicon thin film, the first conductive type amorphous silicon thin film, and the optical adjustment silicon compound thin film are stacked between the substrate and the optical adjustment silicon compound thin film.

[0012] The method for manufacturing a solar cell according to the present invention is a method for manufacturing a back junction solar cell including a crystalline silicon substrate, a first intrinsic amorphous silicon thin film and a first conductivity type amorphous silicon thin film formed in that order in a first region which is a part of the back surface side opposite to the light receiving surface side of the substrate, and a second intrinsic amorphous silicon thin film and a second conductivity type amorphous silicon thin film formed in that order in a second region which is another part of the back surface side of the substrate, the method including a third silicon thin film forming step of forming a third intrinsic amorphous silicon thin film on the entire surface of the light receiving surface side of the substrate, a first silicon thin film forming step of forming patterned first intrinsic amorphous silicon thin film and first conductivity type amorphous silicon thin film in the first region of the back surface side of the substrate, a second silicon thin film forming step of forming patterned second intrinsic amorphous silicon thin film and second conductivity type amorphous silicon thin film in the second region of the back surface side of the substrate, and a silicon compound thin film forming step of forming an optically adjusting silicon compound thin film on the entire surface of the light receiving surface side of the substrate. The first silicon thin film forming step is a step of forming a material film of the first intrinsic amorphous silicon thin film and a material film of the first conductive type amorphous silicon thin film all over the back surface side of the substrate by using a vacuum chamber, the material film of the first intrinsic amorphous silicon thin film and the material film of the first conductive type amorphous silicon thin film being formed around a peripheral portion of the light receiving surface side of the substrate; a first resist forming step of forming a first resist in the first region of the back surface side of the substrate and in a region other than the peripheral portion of the light receiving surface side of the substrate; The method includes a first patterning step of forming a patterned first intrinsic amorphous silicon thin film and a patterned first conductive type amorphous silicon thin film by removing a material film of the first intrinsic amorphous silicon thin film and a material film of the first conductive type amorphous silicon thin film in the second region, in which the third intrinsic amorphous silicon thin film, the first intrinsic amorphous silicon thin film, the first conductive type amorphous silicon thin film, and silicon compound thin films other than the optical adjustment silicon compound thin film in the peripheral portion of the light-receiving surface side of the substrate are also removed, and a first resist removal step of removing the first resist. Effect of the Invention

[0013] According to the present invention, it is possible to reduce white streaks that occur on the peripheral portion of the light-receiving surface side of a back junction type solar cell. [Brief description of the drawings]

[0014] [Figure 1] FIG. 2 is a diagram showing the solar cell according to the embodiment as viewed from the back surface side. [Figure 2A] 2 is an example of a cross-sectional view taken along line II-II of the solar cell shown in FIG. 1. [Figure 2B] 2 is another example of a cross-sectional view taken along line II-II of the solar cell shown in FIG. 1. [Figure 2C] 2 is another example of a cross-sectional view taken along line II-II of the solar cell shown in FIG. 1. [Figure 2D] 2 is another example of a cross-sectional view taken along line II-II of the solar cell shown in FIG. 1. [Figure 3A] 4 is a diagram showing a third silicon thin film deposition step, a first silicon thin film material film formation step (first film deposition step), and a lift-off thin film formation step in the solar cell manufacturing method according to the first embodiment. FIG. [Figure 3B] 5 is a diagram showing a first silicon thin film forming step (first resist forming step) in the method for manufacturing the solar cell according to the first embodiment. FIG. [Figure 3C] 3A to 3C are diagrams illustrating a first silicon thin film forming step (first patterning step) in the method for manufacturing the solar cell according to the first embodiment. [Figure 3D] 5 is a diagram showing a first silicon thin film forming step (first resist removing step) in the solar cell manufacturing method according to the first embodiment. FIG. [Figure 3E] 5A to 5C are diagrams illustrating a second silicon thin film material film formation step in the solar cell manufacturing method according to the first embodiment. [Figure 3F] 5A to 5C are diagrams illustrating a second silicon thin film formation step in the method for manufacturing the solar cell according to the first embodiment. [Figure 3G] FIG. 2 is a diagram showing an optical adjustment silicon compound thin film forming step in the solar cell manufacturing method according to the first embodiment. [Figure 4A] 13A to 13C are diagrams showing a third silicon thin film forming step and a first silicon thin film material film forming step in the solar cell manufacturing method according to the second embodiment. [Figure 4B] FIG. 11 is a diagram showing a first silicon thin film forming step (first resist forming step) in the method for manufacturing a solar cell according to a second embodiment. [Figure 4C] 10 is a diagram showing a first silicon thin film forming step (first patterning step) in the method for manufacturing a solar cell according to a second embodiment. FIG. [Figure 4D] 11A to 11C are diagrams illustrating a first silicon thin film formation step in the method for manufacturing a solar cell according to a second embodiment. [Figure 4E] FIG. 11 is a diagram showing a second silicon thin film material film forming step (second film forming step) in the solar cell manufacturing method according to the second embodiment. [Figure 4F] 11A to 11C are diagrams illustrating a second silicon thin film formation step in the method for manufacturing a solar cell according to a second embodiment. [Figure 4G] FIG. 11 is a diagram showing an optical adjustment silicon compound thin film forming step in the solar cell manufacturing method according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals. For convenience, hatching and reference numerals may be omitted, in which case other drawings shall be referred to.

[0016] (Solar Cell) Fig. 1 is a view of the solar cell according to this embodiment as viewed from the back surface side, and Figs. 2A to 2D are examples of cross-sectional views taken along line II-II of the solar cell shown in Fig. 1, each of which is a different example. The solar cell 1 shown in Fig. 1 and Figs. 2A to 2D is a back junction type (also called back contact type or back electrode type) heterojunction solar cell. The solar cell 1 includes a crystalline silicon substrate 11 having two main surfaces, and the main surface of the substrate 11 has a first region 7 and a second region 8.

[0017] The first region 7 has a so-called comb shape and includes a plurality of finger portions 7f corresponding to the teeth of the comb and busbar portions 7b corresponding to supports for the teeth of the comb. The busbar portions 7b extend in a first direction (X direction) along one side of the substrate 11, and the finger portions 7f extend from the busbar portions 7b in a second direction (Y direction) intersecting the first direction (X direction).

[0018] Similarly, the second region 8 has a so-called comb shape and has a plurality of finger portions 8f corresponding to the teeth of the comb and busbar portions 8b corresponding to supports for the teeth of the comb. The busbar portions 8b extend in a first direction (X direction) along one side portion of the 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.

[0019] The finger portions 7f and the finger portions 8f are provided alternately in the first direction (X direction). The first region 7 and the second region 8 may be formed in a striped pattern.

[0020] As shown in FIGS. 2A to 2D, solar cell 1 includes a crystalline silicon substrate 11, and a third intrinsic amorphous silicon thin film (passivation thin film) 13 and an optical adjustment silicon compound thin film 15, which are deposited in this order on a light receiving surface side (one main surface side) of the main surface of substrate 11. Solar cell 1 also includes a first intrinsic amorphous silicon thin film 23, a first conductivity type amorphous silicon thin film 25, and a first electrode 27, which are deposited in this order on a portion (first region 7) of the back surface side (other main surface side) opposite the light receiving surface of the main surface of substrate 11. Solar cell 1 also includes a second intrinsic amorphous silicon thin film 33, a second conductivity type amorphous silicon thin film 35, and a second electrode 37, which are deposited in this order on another portion (second region 8) of the back surface of substrate 11. In the following, the first intrinsic amorphous silicon thin film 23 and the first conductive type amorphous silicon thin film 25 are also referred to as the first silicon thin film, and the second intrinsic amorphous silicon thin film 33 and the second conductive type amorphous silicon thin film 35 are also referred to as the second silicon thin film. Also, the third intrinsic amorphous silicon thin film (passivation thin film) 13 is also referred to as the third silicon thin film.

[0021] The substrate 11 is formed of a crystalline silicon material such as single crystal silicon or polycrystalline silicon. The substrate 11 is, for example, an n-type substrate in which a crystalline silicon material is doped with an n-type dopant. The substrate 11 may be, for example, a p-type substrate in which a crystalline silicon material is doped with a p-type dopant. An example of the n-type dopant is phosphorus (P). An example of the p-type dopant is boron (B). The substrate 11 functions as a photoelectric conversion substrate that absorbs incident light from the light-receiving surface side and generates photocarriers (electrons and holes).

[0022] By using crystalline silicon as the material of the 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.

[0023] The back surface of the substrate 11 may have a pyramidal fine uneven structure called a texture structure, which increases the efficiency of collection of light that is not absorbed by the substrate 11 and passes through it.

[0024] Furthermore, substrate 11 may have a pyramidal fine uneven structure, called a texture structure, on the light-receiving surface side, which reduces the reflection of incident light on the light-receiving surface and improves the light trapping effect of substrate 11.

[0025] The third intrinsic amorphous silicon thin film (passivation thin film) 13 is formed on the light receiving surface side of the substrate 11 (details will be described later). The first intrinsic amorphous silicon thin film 23 is formed in a first region 7 on the back side of the substrate 11. The second intrinsic amorphous silicon thin film 33 is formed in a second region 8 on the back side of the substrate 11. The first intrinsic amorphous silicon thin film 23, the second intrinsic amorphous silicon thin film 33, and the third intrinsic amorphous silicon thin film 13 are formed of a material containing intrinsic (i-type) amorphous silicon as a main component. The first intrinsic amorphous silicon thin film 23, the second intrinsic amorphous silicon thin film 33, and the third intrinsic amorphous silicon thin film 13 function as a so-called passivation film, suppressing recombination of carriers generated in the substrate 11 and increasing the carrier recovery efficiency.

[0026] The optical adjustment silicon compound thin film 15 is mainly formed on the third intrinsic amorphous silicon thin film (passivation thin film) 13 on the light-receiving surface side of the substrate 11 (details will be described later). The optical adjustment silicon compound thin film 15 functions as an anti-reflection film that prevents reflection of incident light, and also functions as a protective film that protects the light-receiving surface side of the substrate 11 and the third intrinsic amorphous silicon thin film 13. The optical adjustment silicon compound thin film 15 is formed of a silicon compound material such as silicon oxide (SiO), silicon nitride (SiN), silicon oxynitride (SiON), or a composite thereof.

[0027] The first conductive type amorphous silicon thin film 25 is formed on the first intrinsic amorphous silicon thin film 23, i.e., in the first region 7 on the rear surface side of the substrate 11. The first conductive type amorphous silicon thin film 25 is formed of an amorphous silicon material. The first conductive type amorphous silicon thin film 25 is, for example, a p-type thin film in which an amorphous silicon material is doped with a p-type dopant (for example, the above-mentioned boron (B)).

[0028] The second conductive type amorphous silicon thin film 35 is formed on the second intrinsic amorphous silicon thin film 33, i.e., in the second region 8 on the rear surface side of the substrate 11. The second conductive type amorphous silicon thin film 35 is formed of an amorphous silicon material. The second conductive type amorphous silicon thin film 35 is, for example, an n-type thin film 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 amorphous silicon thin film 25 may be an n-type thin film, and the second conductive type amorphous silicon thin film 35 may be a p-type thin film.

[0029] A portion of the second conductive type amorphous silicon thin film 35 and the second intrinsic amorphous silicon thin film 33 may or may not overlap a portion of the adjacent first conductive type amorphous silicon thin film 25 and the first intrinsic amorphous silicon thin film 23.

[0030] The first electrode 27 is formed on the first conductivity type amorphous silicon thin film 25, and the second electrode 37 is formed on the second conductivity type amorphous silicon thin film 35. The first electrode 27 has a transparent electrode 28 and a metal electrode 29 formed in this order on the first conductivity type amorphous silicon thin film 25. The second electrode 37 has a transparent electrode 38 and a metal electrode 39 formed in this order on the second conductivity type amorphous silicon thin film 35.

[0031] The transparent electrodes 28 and 38 are made of a transparent conductive material such as ITO (Indium Tin Oxide: a composite oxide of indium oxide and tin oxide). The metal electrodes 29 and 39 are made of a conductive paste material containing a metal powder such as silver.

[0032] Next, the peripheral portion R1 and side surfaces on the light-receiving surface side of substrate 11 will be described. As described above, in the region (hereinafter also referred to as the center portion) other than peripheral portion R1 on the light-receiving surface side of substrate 11, third intrinsic amorphous silicon thin film (passivation thin film) 13 and optical adjustment silicon compound thin film 15 are deposited in this order. Meanwhile, in peripheral portion R1 and side surfaces on the light-receiving surface side of substrate 11, optical adjustment silicon compound thin film 15 is deposited, but intrinsic amorphous silicon thin film (passivation thin film) 13 is not deposited.

[0033] Furthermore, as shown in FIG. 2A, in the peripheral portion R1 and the side surface on the light receiving surface side of the substrate 11, a second intrinsic amorphous silicon thin film 33 and a second conductivity type amorphous silicon thin film 35 are formed between the substrate 11 and the optical adjustment silicon compound thin film 15.

[0034] On the other hand, in the peripheral portion R1 on the light-receiving surface side of the substrate 11, the first intrinsic amorphous silicon thin film 23 and the first conductivity type amorphous silicon thin film 25 are not formed between the substrate 11 and the optical adjustment silicon compound thin film 15. Furthermore, in the peripheral portion R1 on the light-receiving surface side of the substrate 11, no amorphous silicon thin films other than the second intrinsic amorphous silicon thin film 33 and the second conductivity type amorphous silicon thin film 35, and no silicon compound thin films other than the optical adjustment silicon compound thin film 15 are stacked between the substrate 11 and the optical adjustment silicon compound thin film 15.

[0035] 2B and 2C, second intrinsic amorphous silicon thin film 33 and second conductive type amorphous silicon thin film 35 may be formed only on a part of peripheral portion R1 on the light-receiving surface side of substrate 11. In this case, neither second intrinsic amorphous silicon thin film 33 nor second conductive type amorphous silicon thin film 35 may be laminated in the region other than the part of peripheral portion R1 on the light-receiving surface side of substrate 11 as shown in Fig. 2B, or only second conductive type amorphous silicon thin film 35 may be formed as shown in Fig. 2C.

[0036] Alternatively, as shown in FIG. 2D, in the peripheral portion R1 on the light receiving surface side of the substrate 11, only the second intrinsic amorphous silicon thin film 33 may be formed on at least a part of the peripheral portion R1, and the second conductivity type amorphous silicon thin film 35 may not be laminated.

[0037] The film thickness of second intrinsic amorphous silicon thin film 33 at peripheral portion R1 on the light-receiving surface side of substrate 11 is thinner than the film thickness of third intrinsic amorphous silicon thin film (passivation thin film) 13 at the center of the light-receiving surface side of substrate 11. The film thickness of second intrinsic amorphous silicon thin film 33 at peripheral portion R1 on the light-receiving surface side of substrate 11 and the film thickness of second conductivity type amorphous silicon thin film 35 gradually decrease from the peripheral portion toward the center.

[0038] (Method of manufacturing a solar cell according to the first embodiment) Hereinafter, with reference to Figs. 3A to 3G, a method for manufacturing the solar cell 1 according to this embodiment shown in Figs. 1 and 2A to 2D will be described. Fig. 3A is a diagram showing a third silicon thin film deposition step, a first silicon thin film material film formation step (first film deposition step), and a lift-off thin film formation step in the method for manufacturing the solar cell according to the first embodiment, and Figs. 3B to 3D are diagrams showing a first silicon thin film formation step (first resist formation step, first patterning step, and first resist removal step) in the method for manufacturing the solar cell according to the first embodiment. Fig. 3E is a diagram showing a second silicon thin film material film formation step (second film deposition step) in the method for manufacturing the solar cell according to the first embodiment, and Fig. 3F is a diagram showing a second silicon thin film formation step in the method for manufacturing the solar cell according to the first embodiment. Fig. 3G is a diagram showing an optical adjustment silicon compound thin film deposition step in the method for manufacturing the solar cell according to the first embodiment.

[0039] 3A, a third intrinsic amorphous silicon thin film 13 is deposited on the entire light-receiving surface of a crystalline silicon substrate 11 using, for example, a CVD (chemical vapor deposition) method or a PVD (physical vapor deposition) method in a vacuum chamber (third silicon thin film deposition step). At this time, the deposition gas flows around to the back surface of substrate 11, so that third intrinsic amorphous silicon thin film 13 is deposited also on the side surfaces of substrate 11 and the peripheral portion of the back surface.

[0040] Next, using, for example, a CVD method or a PVD method using a vacuum chamber, a first intrinsic amorphous silicon thin film material film 23Z and a first conductive type amorphous silicon thin film material film 25Z are sequentially deposited on the entire back surface of the substrate 11 (first silicon thin film material film forming process: first deposition process). At this time, the deposition gas flows around to the light receiving surface side of the substrate 11, so that the first intrinsic amorphous silicon thin film material film 23Z and the first conductive type amorphous silicon thin film material film 25Z are deposited also on the side surface of the substrate 11 and the peripheral portion of the light receiving surface.

[0041] The order of deposition of the third intrinsic amorphous silicon thin film 13, the first intrinsic amorphous silicon thin film material film 23Z, and the first conductivity type amorphous silicon thin film material film 25Z is not limited.

[0042] Next, a lift-off thin film (sacrificial thin film) 41 is formed on the entire back surface of substrate 11, specifically, on the entire surface of first conductivity type amorphous silicon thin film material film 25Z, using, for example, a CVD method or a PVD method using a vacuum chamber (lift-off thin film formation step). At this time, the film formation gas flows around to the light receiving surface side of substrate 11, so that lift-off thin film 41 is also formed on the side surface of substrate 11 and the peripheral portion of the light receiving surface. Lift-off thin film 41 is formed of a silicon compound material such as silicon oxide (SiO), silicon nitride (SiN), silicon oxynitride (SiON), or a composite thereof.

[0043] At this time, a silicon compound thin film containing the same material as the lift-off thin film may be formed on the entire light-receiving surface side of substrate 11 by, for example, CVD or PVD using a vacuum chamber.

[0044] Next, as shown in Figures 3B to 3D, a resist is used to remove the first intrinsic amorphous silicon thin film material film 23Z, the first conductivity type amorphous silicon thin film material film 25Z, and the lift-off thin film 41 in the second region 8 on the back surface side of the substrate 11, thereby forming a patterned first intrinsic amorphous silicon thin film 23, the first conductivity type amorphous silicon thin film 25, and the lift-off thin film 41 in the first region 7 (first silicon thin film formation process).

[0045] Specifically, as shown in Fig. 3B, a first resist 90 is formed in the first region 7 on the back surface side of the substrate 11 and in a region (central portion) other than the peripheral portion R1 on the light-receiving surface side of the substrate 11. That is, no resist is formed in the peripheral portion R1 on the light-receiving surface side (first resist forming step). As the first resist 90, a resist generated by photolithography or printing technology is used.

[0046] 3C, the lift-off thin film 41, the first conductive type amorphous silicon thin film material film 25Z, and the first intrinsic amorphous silicon thin film material film 23Z in the second region 8 are etched using the first resist 90 as a mask, thereby forming the patterned first intrinsic amorphous silicon thin film 23, the first conductive type amorphous silicon thin film 25, and the lift-off thin film 41 in the first region 7 (first patterning step). At this time, the third intrinsic amorphous silicon thin film 13, the first intrinsic amorphous silicon thin film material film 23Z, the first conductive type amorphous silicon thin film material film 25Z, and the lift-off thin film 41 (silicon compound thin films other than the optical adjustment silicon compound thin film 15) on the side surface of the substrate 11 and the peripheral portion R1 on the light receiving surface are also etched and removed.

[0047] The etching solution for the lift-off thin film 41 may be, for example, a mixture of ozone dissolved in hydrofluoric acid, or an acidic solution such as a mixture of hydrofluoric acid and nitric acid. The etching solution for the p-type amorphous silicon thin film may be, for example, a mixture of ozone dissolved in hydrofluoric acid, or an acidic solution such as a mixture of hydrofluoric acid and nitric acid, and the etching solution for the n-type amorphous silicon thin film may be, for example, an alkaline solution such as an aqueous solution of potassium hydroxide.

[0048] 3D, the first resist 90 is removed (first resist removal step). As a stripping solution for the first resist 90, for example, an organic solvent such as acetone, or an alkaline solution such as an aqueous solution of potassium hydroxide can be used.

[0049] Next, both sides of the substrate 11 are cleaned (first cleaning step). In the first cleaning step, for example, ozone treatment is performed, followed by hydrofluoric acid treatment. The hydrofluoric acid treatment includes not only treatment with hydrofluoric acid, but also treatment with a mixture of hydrofluoric acid and another type of acid (for example, hydrochloric acid in the first cleaning step).

[0050] 3E, a second intrinsic amorphous silicon thin film material film 33Z and a second conductive type amorphous silicon thin film material film 35Z are sequentially deposited on the entire back surface of substrate 11 using, for example, a CVD method or a PVD method using a vacuum chamber (second silicon thin film material film forming step: second deposition step). At this time, the deposition gas flows around to the light receiving surface side of substrate 11, so that second intrinsic amorphous silicon thin film material film 33Z and second conductive type amorphous silicon thin film material film 35Z are also deposited on the side surface of substrate 11 and on peripheral portion R1 of the light receiving surface.

[0051] 3E to 3G, the wraparound deposition of the second intrinsic amorphous silicon thin film material film 33Z and the second conductive type amorphous silicon thin film material film 35Z is shown in the form corresponding to the above-mentioned Fig. 2A. However, the wraparound deposition of the second intrinsic amorphous silicon thin film material film 33Z and the second conductive type amorphous silicon thin film material film 35Z can be shown in various forms, for example, as shown in the above-mentioned Figs. 2A to 2D.

[0052] Next, as shown in FIG. 3F, a lift-off method using a lift-off thin film (sacrificial thin film) is used to remove the second intrinsic amorphous silicon thin film material film 33Z and the second conductivity type amorphous silicon thin film material film 35Z in the first region 7 on the back surface side of the substrate 11, thereby forming a patterned second intrinsic amorphous silicon thin film 33 and second conductivity type amorphous silicon thin film 35 in the second region 8 (second silicon thin film formation process).

[0053] In addition, in Figure 3F and Figure 3G described below (and the above-mentioned Figures 2A to 2D), in order to simplify the drawings, the second intrinsic amorphous silicon thin film 33 existing between the first conductivity type amorphous silicon thin film 25 and the second conductivity type amorphous silicon thin film 35 shown in Figure 3E is omitted.

[0054] Specifically, by removing the lift-off thin film 41, the second intrinsic amorphous silicon thin film material film 33Z and the second conductive type amorphous silicon thin film material film 35Z on the lift-off thin film 41 are removed, and the patterned second intrinsic amorphous silicon thin film 33 and the second conductive type amorphous silicon thin film 35 are formed in the second region 8 (second patterning step). As a removal solution for the lift-off thin film 41, for example, an acidic solution such as hydrofluoric acid is used.

[0055] In this way, by employing the lift-off method using a lift-off thin film (sacrificial thin film) in the patterning of the second silicon thin film (second patterning), it is possible to simplify the manufacturing process of the solar cell.

[0056] 3G, a silicon compound thin film 15 for optical adjustment is formed on the entire light receiving surface of the substrate 11 by, for example, a CVD method or a PVD method using a vacuum chamber (silicon compound thin film forming process for optical adjustment). At this time, the film forming gas flows around to the back surface of the substrate 11, so that the silicon compound thin film 15 for optical adjustment is also formed on the side surface of the substrate 11 and the peripheral portion of the back surface.

[0057] Next, the first electrode 27 and the second electrode 37 are formed on the back surface side of the substrate 11 (electrode formation step, not shown).

[0058] Specifically, a transparent electrode material film is formed on the entire back surface of the substrate 11 by using a PVD method (physical vapor deposition method) such as a sputtering method. Then, a part of the transparent electrode material film is removed by using an etching method using an etching paste, for example, to form patterned transparent electrodes 28, 38. As an etching solution for the transparent electrode material film, for example, hydrochloric acid or an aqueous solution of ferric chloride is used.

[0059] Thereafter, the metal electrode 29 is formed on the transparent electrode 28, and the metal electrode 39 is formed on the transparent electrode 38, by using, for example, a pattern printing method or a coating method, thereby forming the first electrode 27 and the second electrode 37. Through the above steps, back electrode type solar cell 1 according to this embodiment shown in FIG. 1 and FIGS. 2A to 2D is completed.

[0060] As described above, according to the solar cell manufacturing method of the first embodiment and the solar cell of this embodiment, in the patterning (first patterning) of the first silicon thin films 25, 23, the amorphous silicon thin film and the silicon compound thin film that have been deposited around the peripheral portion R1 of the light-receiving surface of the substrate 11 are removed. This makes it possible to prevent the amorphous silicon thin film and the silicon compound thin film such as the lift-off thin film, which have different refractive indices, from overlapping alternately in the peripheral portion R1 of the light-receiving surface of the substrate 11. This makes it possible to reduce white streaks that occur in the peripheral portion R1 of the light-receiving surface of the substrate 11.

[0061] (Method of manufacturing a solar cell according to a second embodiment) In the first embodiment, the lift-off method is used in the patterning of the second silicon thin film (second patterning). In the second embodiment, the etching method using a resist is used in the patterning of the second silicon thin film (second patterning) as in the patterning of the first silicon thin film (first patterning).

[0062] Hereinafter, with reference to Figs. 4A to 4G, a method for manufacturing the solar cell 1 according to this embodiment shown in Figs. 1 and 2A to 2D will be described. Fig. 4A is a diagram showing a third silicon thin film deposition step and a first silicon thin film material film formation step (first film deposition step) in the method for manufacturing a solar cell according to the second embodiment, and Figs. 4B to 4D are diagrams showing a first silicon thin film formation step (first resist formation step, first patterning step, and first resist removal step) in the method for manufacturing a solar cell according to the second embodiment. Fig. 4E is a diagram showing a second silicon thin film material film formation step (second film deposition step) in the method for manufacturing a solar cell according to the second embodiment, and Fig. 4F is a diagram showing a second silicon thin film formation step in the method for manufacturing a solar cell according to the second embodiment. Fig. 4G is a diagram showing an optical adjustment silicon compound thin film deposition step in the method for manufacturing a solar cell according to the second embodiment.

[0063] 4A, as in the first embodiment, a third intrinsic amorphous silicon thin film 13 is deposited on the entire light-receiving surface of a crystalline silicon substrate 11 by using, for example, a CVD (chemical vapor deposition) method or a PVD (physical vapor deposition) method using a vacuum chamber (third silicon thin film deposition step). At this time, the deposition gas flows around to the back surface of substrate 11, so that third intrinsic amorphous silicon thin film 13 is deposited also on the side surfaces of substrate 11 and the peripheral portion of the back surface.

[0064] Next, similarly to the first embodiment, a first intrinsic amorphous silicon thin film material film 23Z and a first conductive type amorphous silicon thin film material film 25Z are sequentially deposited on the entire back surface of substrate 11 using, for example, a CVD method or a PVD method using a vacuum chamber (first silicon thin film material film forming step: first deposition step). At this time, the deposition gas flows around to the light receiving surface side of substrate 11, so that first intrinsic amorphous silicon thin film material film 23Z and first conductive type amorphous silicon thin film material film 25Z are deposited also on the side surface of substrate 11 and the peripheral portion of the light receiving surface.

[0065] Next, as shown in Figures 4B to 4D, in the same manner as in the first embodiment, a resist is used to remove the first intrinsic amorphous silicon thin film material film 23Z and the first conductivity type amorphous silicon thin film material film 25Z in the second region 8 on the back surface side of the substrate 11, thereby forming patterned first intrinsic amorphous silicon thin film 23 and first conductivity type amorphous silicon thin film 25 in the first region 7 (first silicon thin film formation process).

[0066] 4B, a first resist 90 is formed in the first region 7 on the back surface side of the substrate 11 and in a region (central portion) other than the peripheral portion R1 on the light-receiving surface side of the substrate 11. In other words, no resist is formed in the peripheral portion R1 on the light-receiving surface side (first resist formation process).

[0067] 4C, the first conductive type amorphous silicon thin film material film 25Z and the first intrinsic amorphous silicon thin film material film 23Z in the second region 8 are etched using the first resist 90 as a mask, thereby forming a patterned first intrinsic amorphous silicon thin film 23 and first conductive type amorphous silicon thin film 25 in the first region 7 (first patterning step). At this time, the third intrinsic amorphous silicon thin film 13, the first intrinsic amorphous silicon thin film material film 23Z and the first conductive type amorphous silicon thin film material film 25Z on the side surface of the substrate 11 and in the peripheral portion R1 on the light-receiving surface are also etched and removed.

[0068] Thereafter, as shown in FIG. 4D, the first resist 90 is removed (first resist removal step). Next, similarly to the first embodiment, both sides of the substrate 11 are cleaned (first cleaning step).

[0069] 4E, similarly to the first embodiment, a second intrinsic amorphous silicon thin film material film 33Z and a second conductive type amorphous silicon thin film material film 35Z are sequentially deposited on the entire back surface of substrate 11 using, for example, a CVD method or a PVD method using a vacuum chamber (second silicon thin film material film forming process: second deposition process). At this time, the deposition gas flows around to the light receiving surface side of substrate 11, so that second intrinsic amorphous silicon thin film material film 33Z and second conductive type amorphous silicon thin film material film 35Z are also deposited on the side surface of substrate 11 and on peripheral portion R1 of the light receiving surface.

[0070] 4E to 4G also show the wraparound deposition of the second intrinsic amorphous silicon thin film material film 33Z and the second conductive type amorphous silicon thin film material film 35Z in the form corresponding to the above-mentioned FIG. 2A. However, as described above, the wraparound deposition of the second intrinsic amorphous silicon thin film material film 33Z and the second conductive type amorphous silicon thin film material film 35Z can be in various forms, for example, as shown in the above-mentioned FIG. 2A to FIG. 2D.

[0071] Next, as shown in FIG. 4F, a resist is used to remove the second intrinsic amorphous silicon thin film material film 33Z and the second conductivity type amorphous silicon thin film material film 35Z in the first region 7 on the back surface side of the substrate 11, thereby forming a patterned second intrinsic amorphous silicon thin film 33 and second conductivity type amorphous silicon thin film 35 in the second region 8 (second silicon thin film formation process).

[0072] Specifically, similarly to the above-mentioned first silicon thin film forming step, a second resist is formed on the second region 8 on the back surface side of the substrate 11 and the entire surface of the light receiving surface side of the substrate 11 (second resist forming step). Then, using the second resist as a mask, the second conductive type amorphous silicon thin film material film 35Z and the second intrinsic amorphous silicon thin film material film 33Z in the first region 7 are etched to form a patterned second intrinsic amorphous silicon thin film 33 and second conductive type amorphous silicon thin film 35 in the second region 8 (second patterning step). Then, the second resist is removed (second resist removing step).

[0073] 4G, similarly to the first embodiment, a silicon compound thin film 15 for optical adjustment is formed on the entire light receiving surface of the substrate 11 by, for example, a CVD method or a PVD method using a vacuum chamber. At this time, the film forming gas flows around to the back surface of the substrate 11, so that the silicon compound thin film 15 for optical adjustment is also formed on the side surface of the substrate 11 and the peripheral portion of the back surface.

[0074] Next, similarly to the first embodiment, the first electrode 27 and the second electrode 37 are formed on the back surface side of the substrate 11 (electrode formation step, not shown). Through the above steps, back electrode type solar cell 1 according to this embodiment shown in FIG. 1 and FIGS. 2A to 2D is completed.

[0075] In the solar cell manufacturing method of the second embodiment and the solar cell of this embodiment, the amorphous silicon thin film that has been deposited around the peripheral portion R1 of the light-receiving surface of the substrate 11 is also removed in the patterning (first patterning) of the first silicon thin films 25, 23. This makes it possible to reduce white streaks that occur in the peripheral portion R1 of the light-receiving surface of the substrate 11.

[0076] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments, and various modifications and variations are possible. For example, in the above-mentioned first embodiment, it has been described that a silicon compound thin film containing the same material as the lift-off thin film may be formed on the light-receiving surface side of the substrate 11 before the patterning (first patterning) of the first silicon thin films 25 and 23. Furthermore, before the patterning (first patterning) of the first silicon thin films 25 and 23, an amorphous silicon thin film and / or a silicon compound thin film may be formed on the lift-off thin film on the back side of the substrate 11 by using, for example, a CVD method or a PVD method using a vacuum chamber, or an amorphous silicon thin film and / or a silicon compound thin film may be formed on the silicon compound thin film on the light-receiving surface side of the substrate 11. In such a form, in the peripheral portion R1 of the light-receiving surface of the substrate 11, an amorphous silicon thin film and a silicon compound thin film having different refractive indices are alternately overlapped, and a white stripe is generated conspicuously.

[0077] The solar cell manufacturing method and the solar cell of this embodiment are also applicable to such a configuration. That is, even in such a configuration, according to the solar cell manufacturing method and the solar cell of this embodiment, in the patterning (first patterning) of the first silicon thin films 25, 23, the amorphous silicon thin film and the silicon compound thin film that are deposited around the peripheral portion R1 of the light receiving surface of the substrate 11 are removed. This makes it possible to prevent the amorphous silicon thin film and the silicon compound thin film, which have different refractive indices, from overlapping alternately in the peripheral portion R1 of the light receiving surface of the substrate 11. Therefore, it is possible to reduce white streaks that occur in the peripheral portion R1 of the light receiving surface of the substrate 11. [Explanation of symbols]

[0078] 1. Solar Cell 7 First area 7b, 8b Busbar section 7f,8f Finger section 8 Second area 11 Crystalline silicon substrate 13 Third intrinsic amorphous silicon thin film (third silicon thin film, passivation thin film) 15 Silicon compound thin films for optical adjustment 23 First intrinsic amorphous silicon thin film (first silicon thin film) 23Z 1st intrinsic amorphous silicon thin film material film 25 First conductive type amorphous silicon thin film (first silicon thin film) 25Z First conductive type amorphous silicon thin film material film 27 1st electrode 28,38 Transparent electrode 29,39 Metal electrode 33 Second intrinsic amorphous silicon thin film (second silicon thin film) 33Z 2nd intrinsic amorphous silicon thin film material film 35 Second conductive type amorphous silicon thin film (second silicon thin film) 35Z Second conductive type amorphous silicon thin film material film 37 Second electrode 41 Lift-off thin film 90 Resist R1 Periphery

Claims

1. A back junction solar cell comprising: a crystalline silicon substrate; a first conductivity type amorphous silicon thin film formed on a portion of a back surface side opposite to a light receiving surface side of the substrate; and a second conductivity type amorphous silicon thin film formed on another portion of the back surface side of the substrate, a passivation thin film and an optically adjustable silicon compound thin film are formed in this order on the central portion of the light receiving surface side of the substrate; the optical adjustment silicon compound thin film is formed on the peripheral portion of the light receiving surface side of the substrate, a second conductive type amorphous silicon thin film is formed between the substrate and the optical adjustment silicon compound thin film in at least a part of the peripheral portion of the light receiving surface side of the substrate, In the peripheral portion of the light receiving surface side of the substrate, neither the first conductive type amorphous silicon thin film nor a silicon compound thin film other than the optical adjustment silicon compound thin film is laminated between the substrate and the optical adjustment silicon compound thin film. Solar cell.

2. A back junction solar cell comprising: a crystalline silicon substrate; a first intrinsic amorphous silicon thin film and a first conductivity type amorphous silicon thin film formed in this order on a portion of a back surface side of the substrate opposite to a light receiving surface side; and a second intrinsic amorphous silicon thin film and a second conductivity type amorphous silicon thin film formed in this order on another portion of the back surface side of the substrate, a third intrinsic amorphous silicon thin film and an optically adjustable silicon compound thin film are sequentially formed on a central portion of the light receiving surface side of the substrate; the optical adjustment silicon compound thin film is formed on the peripheral portion of the light receiving surface side of the substrate, a second conductive type amorphous silicon thin film is formed between the substrate and the optical adjustment silicon compound thin film in at least a part of the peripheral portion of the light receiving surface side of the substrate, In the peripheral portion of the light receiving surface side of the substrate, none of the third intrinsic amorphous silicon thin film, the first intrinsic amorphous silicon thin film, the first conductive type amorphous silicon thin film, and a silicon compound thin film other than the optical adjustment silicon compound thin film are laminated between the substrate and the optical adjustment silicon compound thin film. Solar cell.

3. a second intrinsic amorphous silicon thin film is formed between the substrate and the optical adjustment silicon compound thin film in at least a part of the peripheral portion of the light receiving surface side of the substrate; a thickness of the second intrinsic amorphous silicon thin film in the peripheral portion on the light-receiving surface side of the substrate is thinner than a thickness of the third intrinsic amorphous silicon thin film in the central portion on the light-receiving surface side of the substrate; The solar cell according to claim 2 .

4. 4. The solar cell according to claim 3, wherein a thickness of the second intrinsic amorphous silicon thin film in the peripheral portion on the light-receiving surface side of the substrate gradually decreases from the peripheral portion toward the central portion.

5. 5. The solar cell according to claim 1, wherein the thickness of the second conductivity type amorphous silicon thin film in the peripheral portion on the light receiving surface side of the substrate gradually decreases from the peripheral portion toward the central portion.

6. A method for manufacturing a back junction solar cell comprising: a crystalline silicon substrate; a first intrinsic amorphous silicon thin film and a first conductivity type amorphous silicon thin film formed in that order in a first region which is a part of a back surface side of the substrate opposite to a light receiving surface side; and a second intrinsic amorphous silicon thin film and a second conductivity type amorphous silicon thin film formed in that order in a second region which is another part of the back surface side of the substrate, the method comprising: a third silicon thin film deposition step of depositing a third intrinsic amorphous silicon thin film on the entire light receiving surface side of the substrate; a first silicon thin film forming step of forming the first intrinsic amorphous silicon thin film and the first conductive type amorphous silicon thin film patterned in the first region on the back surface side of the substrate; a second silicon thin film forming step of forming the patterned second intrinsic amorphous silicon thin film and the patterned second conductive type amorphous silicon thin film in the second region on the back surface side of the substrate; a silicon compound thin film deposition step of depositing an optically adjustable silicon compound thin film on the entire light receiving surface side of the substrate; Including, The first silicon thin film forming step includes: a first film formation step of forming a material film of the first intrinsic amorphous silicon thin film and a material film of the first conductive type amorphous silicon thin film on the entire back surface side of the substrate using a vacuum chamber, the material film of the first intrinsic amorphous silicon thin film and the material film of the first conductive type amorphous silicon thin film being formed around a peripheral portion of the light receiving surface side of the substrate; a lift-off thin film deposition process, in which a lift-off thin film is deposited on the entire back surface of the substrate using a vacuum chamber, the lift-off thin film being deposited so as to wrap around the peripheral portion of the light receiving surface of the substrate; a first resist forming step of forming a first resist in the first region on the back surface side of the substrate and in a region other than the peripheral portion on the light receiving surface side of the substrate; a first patterning step of forming a patterned first intrinsic amorphous silicon thin film, the first conductive type amorphous silicon thin film, and the lift-off thin film by removing the material film of the first intrinsic amorphous silicon thin film, the material film of the first conductive type amorphous silicon thin film, and the lift-off thin film in the second region on the back surface side of the substrate using the first resist, wherein the third intrinsic amorphous silicon thin film, the material film of the first intrinsic amorphous silicon thin film, the material film of the first conductive type amorphous silicon thin film, and the lift-off thin film, which are silicon compound thin films other than the optical adjustment silicon compound thin film, are all removed in the peripheral portion on the light-receiving surface side of the substrate; a first resist removing step of removing the first resist; Including, The second silicon thin film forming step includes: a second film formation step of forming a material film of the second intrinsic amorphous silicon thin film and a material film of the second conductive type amorphous silicon thin film on the entire back surface side of the substrate using a vacuum chamber, the material film of the second intrinsic amorphous silicon thin film and the material film of the second conductive type amorphous silicon thin film being formed so as to wrap around to the peripheral portion of the light receiving surface side of the substrate; a second patterning step of removing the lift-off thin film by a lift-off method to remove the material film of the second intrinsic amorphous silicon thin film and the material film of the second conductive type amorphous silicon thin film in the first region on the back surface side of the substrate on the lift-off thin film, thereby forming patterned second intrinsic amorphous silicon thin film and second conductive type amorphous silicon thin film; Including, How solar cells are manufactured.

7. A method for manufacturing a back junction solar cell comprising: a crystalline silicon substrate; a first intrinsic amorphous silicon thin film and a first conductivity type amorphous silicon thin film formed in that order in a first region which is a part of a back surface side of the substrate opposite to a light receiving surface side; and a second intrinsic amorphous silicon thin film and a second conductivity type amorphous silicon thin film formed in that order in a second region which is another part of the back surface side of the substrate, the method comprising: a third silicon thin film deposition step of depositing a third intrinsic amorphous silicon thin film on the entire light receiving surface side of the substrate; a first silicon thin film forming step of forming the first intrinsic amorphous silicon thin film and the first conductive type amorphous silicon thin film patterned in the first region on the back surface side of the substrate; a second silicon thin film forming step of forming the patterned second intrinsic amorphous silicon thin film and the patterned second conductive type amorphous silicon thin film in the second region on the back surface side of the substrate; a silicon compound thin film deposition step of depositing an optically adjustable silicon compound thin film on the entire light receiving surface side of the substrate; Including, The first silicon thin film forming step includes: a first film formation step of forming a material film of the first intrinsic amorphous silicon thin film and a material film of the first conductive type amorphous silicon thin film on the entire back surface side of the substrate using a vacuum chamber, the material film of the first intrinsic amorphous silicon thin film and the material film of the first conductive type amorphous silicon thin film being formed around a peripheral portion of the light receiving surface side of the substrate; a first resist forming step of forming a first resist in the first region on the back surface side of the substrate and in a region other than the peripheral portion on the light receiving surface side of the substrate; a first patterning step of forming a patterned first intrinsic amorphous silicon thin film and a patterned first conductive type amorphous silicon thin film by removing a material film of the first intrinsic amorphous silicon thin film and a material film of the first conductive type amorphous silicon thin film in the second region on the back surface side of the substrate using the first resist, in which the third intrinsic amorphous silicon thin film in the peripheral portion on the light receiving surface side of the substrate, the material film of the first intrinsic amorphous silicon thin film, the material film of the first conductive type amorphous silicon thin film, and silicon compound thin films other than the optical adjustment silicon compound thin film are all removed; a first resist removing step of removing the first resist; Including, The second silicon thin film forming step includes: a second film formation step of forming a material film of the second intrinsic amorphous silicon thin film and a material film of the second conductive type amorphous silicon thin film on the entire back surface side of the substrate using a vacuum chamber, the material film of the second intrinsic amorphous silicon thin film and the material film of the second conductive type amorphous silicon thin film being formed so as to wrap around to the peripheral portion of the light receiving surface side of the substrate; a second resist forming step of forming a second resist on the second region on the back surface side of the substrate and on an entire region on the light receiving surface side of the substrate; a second patterning step of removing the material film of the second intrinsic amorphous silicon thin film and the material film of the second conductive type amorphous silicon thin film in the first region on the back surface side of the substrate by using the second resist to form patterned second intrinsic amorphous silicon thin film and second conductive type amorphous silicon thin film; a second resist removing step of removing the second resist; Including, How solar cells are manufactured.

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