JP7689431B2 - Solar cell and method for manufacturing solar cell - Google Patents

Description

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

A back junction solar cell, 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 side, is known as a heterojunction solar cell using a crystalline silicon substrate. In this back junction solar cell, since there is no metal electrode on the light-receiving side, the light-receiving side is uniformly black, making it highly aesthetically pleasing. Patent Document 1 discloses a back junction solar cell.

The solar cell described in Patent Document 1 comprises 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), which are deposited in sequence on a portion of the back surface of the substrate, and a first electrode, 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), which are deposited in sequence on another portion of the back surface of the substrate, and a second electrode. The solar cell also comprises a third intrinsic amorphous silicon thin film (hereinafter also referred to as the third silicon thin film or passivation thin film), and an optically adjustable silicon compound thin film, which are deposited in sequence on the light receiving surface of the substrate.

JP 2014-75526 A

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 (chemical vapor deposition) method or a PVD (physical vapor deposition) method in a vacuum chamber, and then an etching method using photolithography technology is used. However, the etching method using photolithography technology requires processes such as applying photoresist using a spin coat method, drying the photoresist, exposing the photoresist, developing the photoresist, etching the amorphous silicon thin film using the photoresist as a mask, and stripping the photoresist, making the process complicated.

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.

Here, when using a vacuum chamber, for example, with 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 surface. This may result in white streaks that look like white stripes on the periphery of the light-receiving surface.

Such white streaks on the periphery of the light receiving surface are particularly noticeable when using the 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 layered alternately.

The present invention aims to provide a solar cell and a method for manufacturing a solar cell that reduces white streaks that occur on the periphery of the light-receiving surface.

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 formed in sequence on a portion of the back surface side opposite the light-receiving surface side of the substrate, and a second-conductivity-type amorphous silicon thin film formed 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 formed in sequence in the center of the light-receiving surface side of the substrate. The optically adjusting silicon compound thin film is formed on the periphery of the light-receiving surface side of the substrate. In the periphery 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.

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 formed in sequence on a portion of the back surface side opposite 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 formed 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 formed in sequence in the center 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. 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.

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 which are 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 which are 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 on the entire surface of the back surface side of the substrate using a vacuum chamber, in which the material film of the first intrinsic amorphous silicon thin film and the material film of the first conductive type amorphous silicon thin film are 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 process includes a first patterning process for forming a patterned first intrinsic amorphous silicon thin film and a patterned first conductive type amorphous silicon thin film by removing the material film of the first intrinsic amorphous silicon thin film and the 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 are also removed in the peripheral portion of the light receiving surface side of the substrate, and a first resist removal process for removing the first resist.

The present invention can reduce white streaks that occur on the periphery of the light-receiving surface of a back-contact solar cell.

FIG. 2 is a diagram showing the solar cell according to the embodiment as viewed from the back surface side. 2 is an example of a cross-sectional view taken along line II-II of the solar cell shown in FIG. 1. 2 is another example of a cross-sectional view taken along line II-II of the solar cell shown in FIG. 1 . 2 is another example of a cross-sectional view taken along line II-II of the solar cell shown in FIG. 1 . 2 is another example of a cross-sectional view taken along line II-II of the solar cell shown in FIG. 1 . 3A to 3C are diagrams 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. 3A to 3C are diagrams illustrating a first silicon thin film forming step (first resist forming step) in the method for manufacturing a solar cell according to the first embodiment. 3A to 3C are diagrams illustrating a first silicon thin film forming step (first patterning step) in the method for manufacturing a solar cell according to the first embodiment. 3A to 3C are diagrams illustrating a first silicon thin film formation step (first resist removal step) in the method for manufacturing a solar cell according to the first embodiment. 4A to 4C are diagrams illustrating a second silicon thin film material film formation step in the solar cell manufacturing method according to the first embodiment. 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. 3A to 3C are diagrams illustrating an optical adjustment silicon compound thin film forming step in the solar cell manufacturing method according to the first embodiment. 11A to 11C are diagrams showing a third silicon thin film deposition step and a first silicon thin film material film formation step in the solar cell manufacturing method according to the second embodiment. 11A to 11C are diagrams illustrating a first silicon thin film forming step (first resist forming step) in the method for manufacturing a solar cell according to a second embodiment. 11A to 11C are diagrams illustrating a first silicon thin film formation step (first patterning step) in the method for manufacturing a solar cell according to a second embodiment. 11A to 11C are diagrams illustrating a first silicon thin film formation step in a solar cell manufacturing method according to a second embodiment. 11A to 11C are diagrams 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. 11A to 11C are diagrams illustrating a second silicon thin film formation step in the solar cell manufacturing method according to the second embodiment. 11A to 11C are diagrams showing an optical adjustment silicon compound thin film forming step in the solar cell manufacturing method according to the second embodiment.

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

(Solar Cell)
Fig. 1 is a view of the solar cell according to this embodiment as seen 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 includes a first region 7 and a second region 8.

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

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

The finger portions 7f and the finger portions 8f are arranged alternately in the first direction (X direction). The first region 7 and the second region 8 may be formed in a stripe pattern.

As shown in Figures 2A to 2D, the solar cell 1 includes a crystalline silicon substrate 11, 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 the light receiving side (one main surface side) of the main surface of the substrate 11. The 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 the substrate 11. The 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 side of the 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.

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

By using crystalline silicon as the material for 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.

The substrate 11 may have a pyramidal micro-uneven structure, known as a texture structure, on the back side. This increases the efficiency of collecting light that passes through the substrate 11 without being absorbed.

The substrate 11 may also have a pyramidal fine uneven structure, known as a texture structure, on the light-receiving surface side. This reduces the reflection of incident light on the light-receiving surface, improving the light trapping effect of the substrate 11.

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 the first region 7 on the back side of the substrate 11. The second intrinsic amorphous silicon thin film 33 is formed in the 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 mainly composed of intrinsic (i-type) amorphous silicon. 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 the recombination of carriers generated in the substrate 11 and increasing the carrier recovery efficiency.

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 of these.

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 back 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)).

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 back 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.

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.

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 that 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 that order on the second conductivity type amorphous silicon thin film 35.

The transparent electrodes 28, 38 are formed from a transparent conductive material. Examples of transparent conductive materials include ITO (Indium Tin Oxide: a composite oxide of indium oxide and tin oxide). The metal electrodes 29, 39 are formed from a conductive paste material containing a metal powder such as silver.

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

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

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 conductive 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 conductive 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.

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

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 portion of the peripheral portion R1, and the second conductivity type amorphous silicon thin film 35 may not be laminated.

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

(Method of manufacturing solar cell according to the first embodiment)
Hereinafter, the method for manufacturing the solar cell 1 according to the present embodiment shown in FIG. 1 and FIG. 2A to FIG. 2D will be described with reference to FIG. 3A to FIG. 3G. FIG. 3A is a diagram showing the third silicon thin film deposition step, the first silicon thin film material film deposition step (first deposition step), and the lift-off thin film deposition step in the method for manufacturing the solar cell according to the first embodiment, and FIG. 3B to FIG. 3D are diagrams showing the first silicon thin film deposition 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 the second silicon thin film material film deposition step (second deposition step) in the method for manufacturing the solar cell according to the first embodiment, and FIG. 3F is a diagram showing the second silicon thin film deposition step in the method for manufacturing the solar cell according to the first embodiment. FIG. 3G is a diagram showing the optical adjustment silicon compound thin film deposition step in the method for manufacturing the solar cell according to the first embodiment.

First, as shown in FIG. 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 process). At this time, the deposition gas flows around to the back side of the substrate 11, so that the third intrinsic amorphous silicon thin film 13 is also deposited on the side and peripheral portion of the back side of the substrate 11.

Next, using, for example, a CVD method or a PVD method using a vacuum chamber, the first intrinsic amorphous silicon thin film material film 23Z and the 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 formation 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 also deposited on the side surface of the substrate 11 and the peripheral portion of the light receiving surface.

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.

Next, a lift-off thin film (sacrificial thin film) 41 is deposited on the entire back surface of the substrate 11, specifically on the entire surface of the first conductive 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 process). At this time, the deposition gas flows around to the light-receiving surface side of the substrate 11, so that the lift-off thin film 41 is also deposited on the side surface of the substrate 11 and the peripheral portion of the light-receiving surface. The 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 of these.

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 the substrate 11 using, for example, a CVD method or a PVD method using a vacuum chamber.

Next, as shown in Figures 3B to 3D, 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 in the second region 8 are removed using a resist on the back side of the substrate 11, thereby forming a 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 silicon thin film formation process).

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 the 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). As the first resist 90, a resist generated using photolithography technology or printing technology is used.

Then, as shown in FIG. 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 to form a 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.

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

Then, as shown in FIG. 3D, the first resist 90 is removed (first resist removal process). Examples of a stripping solution for the first resist 90 include an organic solvent such as acetone, or an alkaline solution such as an aqueous solution of potassium hydroxide.

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 treatment with not only hydrofluoric acid, but also a mixture of hydrofluoric acid and other types of acids (for example, hydrochloric acid in the first cleaning step).

Next, as shown in FIG. 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 the substrate 11 using, for example, a CVD method or a PVD method using a vacuum chamber (second silicon thin film material film formation process: second deposition process). At this time, the deposition gas flows around to the light receiving surface side of the substrate 11, so that the second intrinsic amorphous silicon thin film material film 33Z and the second conductive type amorphous silicon thin film material film 35Z are also deposited on the side surface of the substrate 11 and the peripheral portion R1 of the light receiving surface.

In addition, in Figures 3E to 3G, the wraparound film formation 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 a form corresponding to the above-mentioned Figure 2A. However, the wraparound film formation form 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 various forms, for example, as shown in the above-mentioned Figures 2A to 2D.

Next, as shown in FIG. 3F, the second intrinsic amorphous silicon thin film material film 33Z and the second conductive type amorphous silicon thin film material film 35Z in the first region 7 are removed on the rear surface side of the substrate 11 using a lift-off method using a lift-off thin film (sacrificial thin film), thereby forming a patterned second intrinsic amorphous silicon thin film 33 and a second conductive type amorphous silicon thin film 35 in the second region 8 (second silicon thin film formation process).

Note that in FIG. 3F and FIG. 3G described below (and the above-mentioned FIGS. 2A to 2D), the second intrinsic amorphous silicon thin film 33 present between the first conductivity type amorphous silicon thin film 25 and the second conductivity type amorphous silicon thin film 35 shown in FIG. 3E is omitted for the sake of simplicity.

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 a patterned second intrinsic amorphous silicon thin film 33 and 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, an acidic solution such as hydrofluoric acid is used.

In this way, by adopting 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 solar cells.

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

Next, a first electrode 27 and a second electrode 37 are formed on the rear surface of the substrate 11 (electrode formation process, not shown).

Specifically, a transparent electrode material film is formed on the entire back surface of the substrate 11 using a PVD method (physical vapor deposition) such as sputtering. Then, a portion of the transparent electrode material film is removed 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.

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.

As described above, according to the solar cell manufacturing method of the first embodiment and the solar cell of this embodiment, in the patterning of the first silicon thin films 25, 23 (first patterning), the amorphous silicon thin film and silicon compound thin film that were 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 a 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. Therefore, it is possible to reduce white streaks that occur in the peripheral portion R1 of the light receiving surface of the substrate 11.

(Method of manufacturing solar cell according to the 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).

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

First, as shown in FIG. 4A, in the same manner 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 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 process). At this time, the deposition gas flows around to the back side of the substrate 11, so that the third intrinsic amorphous silicon thin film 13 is also deposited on the side and peripheral portion of the back side of the substrate 11.

Next, as in 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 formed on the entire back surface of the substrate 11 using, for example, a CVD method or a PVD method using a vacuum chamber (first silicon thin film material film formation process: first film formation process). At this time, the film formation 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 also formed on the side surface of the substrate 11 and the peripheral portion of the light receiving surface.

Next, as shown in Figures 4B to 4D, similar to the first embodiment, the first intrinsic amorphous silicon thin film material film 23Z and the first conductive type amorphous silicon thin film material film 25Z in the second region 8 are removed using a resist on the back side of the substrate 11, thereby forming a patterned first intrinsic amorphous silicon thin film 23 and a first conductive type amorphous silicon thin film 25 in the first region 7 (first silicon thin film formation process).

Specifically, as shown in FIG. 4B, a first resist 90 is formed in the first region 7 on the back surface side of the substrate 11 and in the 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 on the peripheral portion R1 on the light-receiving surface side (first resist formation process).

Then, as shown in FIG. 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 to form 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 the peripheral portion R1 on the light receiving surface are also etched and removed.

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).

Next, as shown in FIG. 4E, similar 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 formed on the entire back surface of the substrate 11 using, for example, a CVD method or a PVD method using a vacuum chamber (second silicon thin film material film formation process: second film formation process). At this time, the film formation gas flows around to the light receiving surface side of the substrate 11, so that the second intrinsic amorphous silicon thin film material film 33Z and the second conductive type amorphous silicon thin film material film 35Z are also formed on the side surface of the substrate 11 and the peripheral portion R1 of the light receiving surface.

Note that Figures 4E to 4G also show 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 a form corresponding to the above-mentioned Figure 2A. However, as described above, 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 take various forms, for example, as shown in the above-mentioned Figures 2A to 2D.

Next, as shown in FIG. 4F, the second intrinsic amorphous silicon thin film material film 33Z and the second conductive type amorphous silicon thin film material film 35Z in the first region 7 are removed using a resist on the back side of the substrate 11, thereby forming a patterned second intrinsic amorphous silicon thin film 33 and a patterned second conductive type amorphous silicon thin film 35 in the second region 8 (second silicon thin film formation process).

Specifically, similar to the first silicon thin film formation process described above, a second resist is formed on the second region 8 on the back surface side of the substrate 11 and the entire light receiving surface side of the substrate 11 (second resist formation process). Then, 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 using the second resist as a mask 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 process). Then, the second resist is removed (second resist removal process).

Next, as shown in FIG. 4G, similar 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 side of the substrate 11, so that the silicon compound thin film 15 for optical adjustment is also formed on the side and peripheral portion of the back side of the substrate 11.

Next, similarly to the first embodiment, the first electrode 27 and the second electrode 37 are formed on the rear 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.

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 during patterning of the first silicon thin films 25, 23 (first patterning). This makes it possible to reduce white streaks that occur around the peripheral portion R1 of the light receiving surface of the substrate 11.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above-mentioned embodiment, 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 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.

The solar cell manufacturing method and solar cell of this embodiment can be applied to such a configuration. That is, even in such a configuration, according to the solar cell manufacturing method and solar cell of this embodiment, in the patterning (first patterning) of the first silicon thin films 25, 23, the amorphous silicon thin film and silicon compound thin film that are formed 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.

REFERENCE SIGNS LIST 1 solar cell 7 first region 7b, 8b busbar portion 7f, 8f finger portion 8 second region 11 crystalline silicon substrate 13 third intrinsic amorphous silicon thin film (third silicon thin film, passivation thin film)
15 Silicon compound thin film for optical adjustment 23 First intrinsic amorphous silicon thin film (first silicon thin film)
23Z First 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: First electrode 28, 38: Transparent electrode 29, 39: Metal electrode 33: Second intrinsic amorphous silicon thin film (second silicon thin film)
33Z Second 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: peripheral portion

Claims (7)

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. 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. 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 . The solar cell according to claim 3, wherein the thickness of the second intrinsic amorphous silicon thin film in the peripheral portion of the light-receiving surface side of the substrate gradually decreases from the peripheral portion toward the central portion. The solar cell according to any one of claims 1 to 4, wherein the thickness of the second conductive 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. 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. 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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