KR20140101287A - Crystalline silicon solar cell and manufacturing method thereof - Google Patents

Abstract

[PROBLEMS] To provide a crystalline silicon type solar cell which can sufficiently reduce the recombination speed of carriers and can be manufactured at low cost, and a manufacturing method thereof.
[MEANS FOR SOLVING PROBLEMS] A second passivation film having a film thickness of 5 to 30 nm is formed between the back electrode layer and the first semiconductor layer. Then, the electrode material of the back electrode layer is diffused to the first semiconductor layer through the second passivation film by firing, so that the first semiconductor layer and the back electrode layer are electrically connected to each other, and the first passivation film and the first semiconductor layer The first conductivity type high-concentration semiconductor layer having the first conductivity type impurity concentration higher than the semiconductor layer is formed. As a result, patterning of the electrode typified by photolithography is not required (without increasing the manufacturing cost), and the recombination speed of the carrier can be sufficiently lowered.

Description

TECHNICAL FIELD [0001] The present invention relates to a crystalline silicon type solar cell, and a method of manufacturing the same. BACKGROUND ART [0002]

The present invention relates to a crystalline silicon type solar cell having a passivation film between a semiconductor layer and a back electrode layer, and a manufacturing method thereof.

One of the major technical themes in the field of solar cells is the improvement of efficiency (photoelectric conversion efficiency). In order to improve the efficiency of the solar cell, it is effective to lead most of the carriers (holes and electrons) generated by light to the corresponding electrodes respectively. This corresponds to lowering the recombination speed of holes and electrons. As a technique therefor, a method of forming a back surface field (BSF) has been known for a long time.

The formation of such a back wall is performed by forming a p < + > -type semiconductor layer doped with a p-type impurity at a high concentration on the back side of the p-type silicon substrate. The electric field generated between the p-type semiconductor layer (p-type silicon substrate) and the p + -type semiconductor layer prevents the electrons in the carriers generated in the p-type semiconductor layer from reaching the back electrode, And the recombination speed of electrons is lowered. However, in this structure, since the recombination center remains on the back side of the p-type silicon substrate, it is difficult to sufficiently lower the recombination speed.

Japanese Patent Application Laid-Open No. 2012-33757 Japanese Patent Application Laid-Open No. 9-45945

As a technique for further lowering the recombination speed, in Patent Documents 1 and 2, a back passivation film (for example, a film mainly composed of silicon nitride) is formed between the p-type silicon substrate and the back electrode, , A technique of terminating a short dangling bond of silicon atoms which is the center of recombination by a passivation film is adopted.

However, in the above technique, since the back passivation film is an insulating film, it is necessary to pattern the back electrode in a method typified by photolithography in order to conduct the p-type silicon substrate and the back electrode, so that the manufacturing cost of the solar cell is increased do.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide a crystalline silicon type solar cell which can sufficiently reduce the recombination speed and can be manufactured at low cost, and a manufacturing method thereof.

According to a first aspect of the present invention, there is provided a semiconductor device comprising a back electrode layer, a first semiconductor layer of a first conductivity type, a second semiconductor layer of a second conductivity type, a first passivation film, And a second major surface on the side opposite to the first main surface of the light receiving side in this order from the side of the first main surface, wherein a thickness of 5 to 30 nm is provided between the back electrode layer and the first semiconductor layer And the electrode material of the back electrode layer is diffused to the first semiconductor layer through the second passivation film so that the first semiconductor layer and the back electrode layer are electrically connected to each other and the second passivation film is formed, And a high-concentration semiconductor layer of a first conductivity type having a first conductivity type impurity concentration higher than that of the first semiconductor layer is formed between the film and the first semiconductor layer.

The invention described in claim 2 is the crystalline silicon type solar cell according to claim 1, wherein the first passivation film has antireflection property.

The invention described in claim 3 is the crystalline silicon type solar cell according to claim 1 or 2, wherein the second passivation film is made of silicon nitride.

The invention described in claim 4 is the crystalline silicon type solar cell according to claim 3, wherein the refractive index of the second passivation film is 2.4 or more.

According to a fifth aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising the steps of: (a) introducing an impurity of the second conductivity type from the first main surface side of the light- A pn junction forming step of forming a pn junction between the first semiconductor layer and the second semiconductor layer of the second conductivity type existing on the first semiconductor layer; (b) forming a first passivation film on the first main surface Forming a second passivation film on the second main surface of the substrate; (c) forming a surface electrode layer on the first passivation film and forming an electrode layer on the second passivation film And (d) a firing step of firing the surface electrode layer and the back electrode layer, wherein the film thickness of the second passivation film formed in the step (b) is 5 to 30 (d) heating the surface electrode layer to reach the second semiconductor layer through the electrode material of the surface electrode layer through a part of the first passivation film; and And d-2) heating the back electrode layer to diffuse the electrode material of the back electrode layer through the second passivation film to the first semiconductor layer And a second conductive type impurity concentration higher than that of the first semiconductor layer is formed between the second passivation film and the first semiconductor layer by conducting the first semiconductor layer and the back electrode layer, And a diffusion step of forming a heavily doped semiconductor layer of a crystalline silicon type solar cell.

According to a sixth aspect of the present invention, in the method of manufacturing a crystalline silicon solar cell according to the fifth aspect, the first passivation film has antireflection properties.

According to a seventh aspect of the invention, there is provided a method of manufacturing a crystalline silicon type solar cell according to the fifth or sixth aspect, wherein the second passivation film is made of silicon nitride.

The invention according to claim 8 is the method for producing a crystalline silicon type solar cell according to claim 7, wherein the refractive index of the second passivation film is 2.4 or more.

According to the invention of claims 1 to 8, a second passivation film having a film thickness of 5 to 30 nm is formed between the back electrode layer and the first semiconductor layer. Since the electrode material for forming the back electrode layer is diffused to the first semiconductor layer through the second passivation film, the first semiconductor layer and the back electrode layer are electrically connected to each other, and the second passivation film is formed between the second passivation film and the first semiconductor layer The first conductivity type high-concentration semiconductor layer having the first conductivity type impurity concentration higher than that of the first semiconductor layer is formed.

As described above, since the first semiconductor layer and the back electrode layer are electrically connected by the diffusion of the electrode material for forming the back electrode layer, the patterning of the back electrode in the method typified by photolithography is not required and the manufacturing cost can be reduced have.

Further, since the second passivation film is formed on the back side of the first semiconductor layer, the recombination speed of carriers can be sufficiently lowered and the photoelectric conversion efficiency can be improved (passivation effect). Further, since the first conductivity type high-concentration semiconductor layer is formed between the second passivation film and the first semiconductor layer, the recombination of the carriers by the electric field generated between the first semiconductor layer and the first conductivity- The speed can be lowered and the photoelectric conversion efficiency can be improved.

In particular, according to the invention of claim 2 or claim 6, the first passivation film has antireflection property. Therefore, the light irradiated from the outside of the solar cell to the first passivation film can be efficiently inserted into the inside of the solar cell.

Particularly, according to the invention of Claim 4 or 8, the defect density of the second passivation film at the interface between the second passivation film and the silicon substrate is lowered by setting the silicon nitride as the main component and the refractive index thereof as 2.4 or more, The resistance is lowered, so that the photoelectric conversion efficiency can be improved.

1 is a sectional view showing a solar cell 1 according to an embodiment.
2 is a flow chart showing a manufacturing process of the solar cell 1 according to the embodiment.
3 is a cross-sectional view showing the manufacturing process of the solar cell 1 according to the embodiment.
4 is a cross-sectional view showing the manufacturing process of the solar cell 1 according to the embodiment.
5 is a cross-sectional view showing the manufacturing process of the solar cell 1 according to the embodiment.
6 is a cross-sectional view showing the manufacturing process of the solar cell 1 according to the embodiment.
7 is a cross-sectional view showing the manufacturing process of the solar cell 1 according to the embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<Embodiment 1>

&Lt; 1.1 Construction of Solar Cell (1) >

1 is a cross-sectional view schematically showing a configuration example of a solar cell which is an embodiment of the present invention. In Fig. 1 and the subsequent figures, for the sake of easy understanding, the dimensions and the number of each part are exaggerated or simplified as necessary.

1, the solar cell 1 of the present embodiment includes a back electrode layer 31, a second passivation film 21, a silicon substrate 10, a first passivation film 22, And a cell structure in which a surface electrode 32a formed on the first passivation film 22 is laminated in order from the light receiving side (the upper side in Fig. 1) (the lower side in Fig. 1) to be. 1, only a part of the area of the enlargement of the solar cell 1 in the lateral direction is shown, and other areas of the solar cell 1 have the same sectional structure.

The silicon substrate 10 is a p-type silicon substrate having a first main surface S1 as a main surface of a light receiving side and a second main surface S2 as a main surface opposite to the first main surface S1 (for example, (For example, a silicon substrate including a p-type impurity such as silicon, boron, or the like), and on both of the major surfaces S1 and S2, a periodic two- A repeated pattern in the form of a pyramid) is formed. A single crystal silicon substrate or a polycrystalline silicon substrate can be used for the silicon substrate 10. Hereinafter, a case where a single crystal silicon substrate is used will be described.

The n-type semiconductor layer 14 is formed by thermal diffusion of an n-type impurity (for example, phosphorus oxychloride) on the first main surface S1 of the silicon substrate 10 where the texture TX1 is formed.

On the other hand, on the second main surface S2 of the silicon substrate 10 on which the texture TX2 is formed, by thermal diffusion of the back electrode layer 31 (in this embodiment, aluminum is the main component in the present embodiment) And the p + -type semiconductor layer 12 having a higher p-type impurity concentration than the silicon substrate 10 are formed.

In the following description, a layer (silicon substrate 10) which does not belong to any of the alloy layer 11, the p + -type semiconductor layer 12 and the n-type semiconductor layer 14 in the silicon substrate 10 ) Is referred to as a p-type semiconductor layer 13.

As described above, the solar cell 1 of this embodiment has the p-type semiconductor layer 13 and the p + -type semiconductor layer 12, so that an electric field by the back barrier (BSF) is generated at the boundary of these layers, It is possible to reduce the recombination speed of the carrier in the vicinity of the carrier 31.

On the first main surface S1 side of the silicon substrate 10, a protective film having a light reflection preventing property (a film mainly composed of silicon nitride in this embodiment) is formed as the first passivation film 22. The light irradiated from the outside of the solar cell 1 to the main surface (hereinafter referred to as the "light receiving surface S3") of the main surface of the first passivation film 22 opposite to the silicon substrate 10, So that it can be effectively inserted into the inside of the solar cell 1.

A protective film having a refractive index of 2.4 or more (in this embodiment, a film mainly composed of silicon nitride) is formed as a second passivation film 21 on the second main surface S2 side of the silicon substrate 10 with a film thickness D of 5 to 30 nm .

The surface electrode 32a is an electrode made of a paste-like first electrode material obtained by kneading a metal (silver powder in this embodiment) and a glass frit having a low melting point in an organic binder. After the first electrode material is applied as a pattern of the surface electrode layer 32 to a part of the surface of the first passivation film 22 opposite to the silicon substrate 10 (Fig. 7), the resulting structure is fired, A part of the material reaches the n-type semiconductor layer 14 through a part of the first passivation film 22 (Fig. 1). As a result, the surface electrode 32a and the n-type semiconductor layer 14 are electrically connected.

The back electrode layer 31 is an electrode made of a paste-like second electrode material obtained by kneading a metal (powder of aluminum in this embodiment) and a glass frit having a low melting point in an organic binder. The second electrode material is applied on the side opposite to the silicon substrate 10 of the second passivation film 21 (Fig. 7), and then the obtained structure is fired so that a part of the second electrode material becomes the second passivation film 21, And is diffused into the silicon substrate 10 through the silicon substrate 10 side. As a result, the p-type semiconductor layer 13 and the back electrode layer 31 are electrically connected and the alloy layer 11 and the p + -type semiconductor layer 13 are formed between the second passivation film 21 and the p- 12 are formed.

Further, in this embodiment, the first electrode material and the second electrode material are made of different metals, and the use of the same kind of metal for the first and second electrode materials is not prohibited.

 As described above, in the solar cell 1 of the present embodiment, the p-type and n-type correspond to the "first conductivity type" and the "second conductivity type" in the present invention, Type semiconductor layer 13 and the n-type semiconductor layer 14 function as the "first semiconductor layer" and the "second semiconductor layer", and the p + -type semiconductor layer 12 functions as the npp + to be.

The solar cell 1 of the present embodiment is formed not only with the first passivation film 22 on the side of the light receiving surface S3 but also with the second passivation film 21 having a specific range of thickness and refractive index, The technical role of this second passivation film 21 is particularly large, and the reason for this will be described after the method of manufacturing the solar cell 1 is described.

&Lt; 1.2 Manufacturing Method of Solar Cell (1)

The manufacturing method of the solar cell 1 according to the present embodiment includes the manufacturing flow shown in Fig. 2, the sectional view of the solar cell 1 in the manufacturing process shown in Figs. 3 to 7, With reference to the sectional view of the solar cell 1 after the production.

First, a p-type silicon substrate 10 is prepared (Fig. 3) and a texture is formed on the first main surface S1 and the second main surface S2 as an uneven structure of the antireflection structure (step ST1: texture formation fair).

In the case of a solar cell, a substrate sliced from an ingot is often used as the silicon substrate 10. In this case, an alkali aqueous solution such as potassium hydroxide, an aqueous solution of sodium hydroxide, a mixed solution of hydrofluoric acid and acetic acid, or the like may be added to the surface of the substrate in order to remove the damage to the surface of the substrate due to scratches, The surface of the substrate is etched by about 10 to 20 占 퐉. In order to remove heavy metals such as iron attached to the surface of the substrate, a step of cleaning with a mixed solution of hydrochloric acid and hydrogen peroxide may be added. Thereafter, textures (TX1, TX2) having an antireflection structure are formed by using an aqueous alkali solution such as potassium hydroxide, sodium hydroxide solution or the like. 4 is a cross-sectional view of the silicon substrate 10 after the texturing process.

Next, as shown in Fig. 5, an n-type semiconductor layer 14 is formed by thermally diffusing an n-type impurity (for example, phosphorus oxychloride) on the surface of the p- . As a result, a pn junction of the p-type semiconductor layer 13 and the n-type semiconductor layer 14 formed on the p-type semiconductor layer 13 is formed in the silicon substrate 10 (step ST2: pn junction formation step) .

In the pn junction forming step (step ST2) of the present embodiment, various known pn junction methods can be employed. A typical example thereof will be described.

First, an n-type semiconductor layer 14 is formed on the entire surface of the silicon substrate 10. The depth of the n-type semiconductor layer 14 can be controlled with the diffusion temperature and the diffusion time as process conditions. Then, the n-type semiconductor layer 14 formed on the first main surface S1 side of the silicon substrate 10 is protected by the resist and then etched so as to leave the n-type diffusion layer only on the first main surface S1. The remaining resist after the treatment is removed using an organic solvent or the like.

Separately from the above method, a liquid coating material containing phosphorus such as PSG (Phospho-Silicate-Glass) is applied to the first main surface S1 of the silicon substrate 10 by using a spin coat or the like , And a diffusion method of annealing under appropriate conditions may be used.

6, a first passivation film 22 is formed on the first main surface S1 side of the silicon substrate 10 and a second passivation film 21 is formed on the second main surface S2 side (Step ST3: passivation film forming step).

In step ST3, a first passivation film 22 (for example, silicon nitride) is formed on the first main surface S1 of the silicon substrate 10 as a protective film having antireflective property on the n-type semiconductor layer 14 Film as a main part). Since the first passivation film 22 reduces the surface reflectance of the solar cell 1 with respect to the incident light, it is possible to increase the generated current with a large width.

The first passivation film 22 is formed using a vacuum evaporation method represented by a reduced pressure thermal CVD method or a plasma CVD method. Hereinafter, as a typical example of the film formation method of the first passivation film 22, a case of forming by the reduced pressure thermal CVD method and a case of forming by the plasma CVD method will be described.

In the case of the reduced pressure thermal CVD method, for example, dichlorosilane gas and ammonia gas may be heated at a temperature of 700 ° C or higher as a raw material. When the film is formed by the plasma CVD method, for example, the source gas may be decomposed by plasma using a mixed gas of monosilane and ammonia, and the film may be formed at a temperature of 300 to 550 ° C.

In this film forming method, by controlling the processing conditions such as the feed ratio of the raw material gas, the feed amount of the raw material gas, the heating temperature, the heating time, and the pressure during film formation, the film quality (film thickness, refractive index Etc.) can be adjusted. Further, the plasma CVD method is characterized in that it is a low-temperature film as compared with the thermal CVD, and is easily included in a protective film in which hydrogen contained in the raw material gas is deposited.

When the first passivation film 22 is formed on the first main surface S1 side of the silicon substrate 10 and then the second passivation film 21 is formed on the second main surface S2 side 6). As a result, the center of recombination such as the short bonding bond on the second main surface S2 side of the silicon substrate 10 is terminated by the silicon atom or hydrogen atom of the second passivation film 21, And the photoelectric conversion efficiency is increased (passivation effect).

As the method of forming the second passivation film 21, a vacuum vapor deposition method typified by a reduced pressure thermal CVD method, a plasma CVD method, or the like can be used, similarly to the method of forming the first passivation film 22. [ In addition, a low inductance antenna (LIA: Low Inductance Antenna) type plasma film forming apparatus can also be used for forming the second passivation film 21.

A second passivation film 21 having a refractive index of 2.4 or higher is formed on the second main surface S2 side of the silicon substrate 10 with a film thickness D of 5 to 30 nm by controlling the above- . As an example of the control of film formation processing conditions, the refractive index of the protective film to be formed can be increased by increasing the content of the silicon-based gas in the raw material gas, and the protective film to be formed can be thickened by increasing the film formation time.

When the heat treatment is added to the subsequent step of baking (step ST5), the refractive index of the first passivation film 22 and the second passivation film 21 is lower than that of the film immediately after film formation There is a case that it changes. In this case, it is possible to obtain a desired film quality (film thickness, refractive index, and the like) by coping with the processing condition of the film formation in step ST3 by taking into consideration the film quality change by the heat treatment in the firing step in advance.

In the above example, the case where the second passivation film 21 is formed after the first passivation film 22 is formed has been described. However, the order of the film formation may be reverse or simultaneous.

7, a surface electrode layer 32 is formed on the first passivation film 22, and a back electrode layer 31 is formed on the second passivation film 21 (step ST4: electrode formation fair).

Specifically, the first electrode material (the electrode material of the surface electrode layer 32) is formed on the main surface of the first passivation film 22 opposite to the silicon substrate 10 and the silicon substrate 10 of the second passivation film 21, (The electrode material of the back electrode layer 31) is applied in a layer form using a screen printing method to the main surface on the opposite side of the substrate 10 and dried. As a result, the surface electrode layer 32 and the back electrode layer 31 are formed.

Then, when the surface electrode layer 32 and the back electrode layer 31 are formed, firing is performed next (step ST5: firing step). In the firing step, the production process of the solar cell 1 formed in steps ST1 to ST4 is fired at 650 DEG C or higher for several seconds to several minutes.

The first electrode material is melted by firing, passes through a part of the first passivation film 22, and reaches the n-type semiconductor layer 14. Thereby, the surface electrode 32a is formed, and the surface electrode 32a and the n-type semiconductor layer 14 are electrically connected (step ST5A: conduction step).

As described above, the first electrode material contains a glass frit having a low melting point. By melting the glass frit, the first passivation film 22 can be melted and penetrated in the conduction process.

1, the penetration depth of the first electrode material in the conduction process is controlled so as to reach the depth reaching the n-type semiconductor layer 14 but not reaching the p-type semiconductor layer 13 do. The penetration depth is adjusted by controlling the processing conditions such as the firing temperature and firing time.

On the other hand, the second electrode material is melted by firing and diffused to the p-type semiconductor layer 13 through the second passivation film 21. [ This is because the film thickness D of the second passivation film 21 of this embodiment is as thin as 5 to 30 nm.

As a result, the back electrode layer 31 and the p-type semiconductor layer 13 are electrically connected to each other by the firing process, and a silicon component and aluminum (Al) are formed between the second passivation film 21 and the p- And the p + -type semiconductor layer 12 having a p-type impurity concentration higher than that of the p-type semiconductor layer 13 are formed (step ST5B: diffusion step).

As described above, in the fabrication of the solar cell 1 according to the present embodiment, since the back electrode layer 31 and the p-type semiconductor layer 13 are electrically connected without patterning the electrode typified by photolithography, .

Further, since the second passivation film is formed on the second main surface S2 side of the silicon substrate 10, the recombination speed of carriers can be sufficiently lowered and the photoelectric conversion efficiency can be improved (passivation effect). In order to make this passivation effect effective, the second passivation film 21 is formed with a film thickness D of at least 5 nm or more.

The p + -type semiconductor layer 12 is formed between the second passivation film and the p-type semiconductor layer 13 by diffusing the back electrode layer 31 containing aluminum as a main component. the recombination speed of the carriers is lowered by the electric field generated between the p + -type semiconductor layers 12, and the photoelectric conversion efficiency can be further improved (BSF effect).

1, the diffusion depth of the second electrode material in the diffusion process is controlled so as to be a diffusion depth that reaches the p-type semiconductor layer 13 but does not reach the n-type semiconductor layer 14 do. The diffusion depth is adjusted by controlling the processing conditions such as the firing temperature and firing time, as well as the penetration depth. That is, the processing conditions of the firing step are set based on the processing conditions in the conduction step and the diffusion step.

 The solar cell 1 of the present embodiment can be manufactured by the manufacturing steps of steps ST1 to ST5 described above.

<Advantages of the Solar Cell 1 of the Embodiment 1.3>

(1) As described above, in the solar cell 1 of the present embodiment, a second passivation film having a film thickness D of 5 to 30 nm is formed between the back electrode layer 31 and the p- (21) is formed. As described above, since the second passivation film 21 is extremely thin as 5 to 30 nm, the second electrode material (electrode material for forming the back electrode layer 31) is formed through the second passivation film 21, (13), and the p-type semiconductor layer (13) and the back electrode layer (31) are electrically connected to each other. As a result, patterning of the back surface electrode represented by photolithography is not required, and the manufacturing cost can be reduced.

(2) Since the second passivation film 21 is formed on the second main surface S2 side of the p-type semiconductor layer 13, the recombination speed of carriers can be sufficiently lowered and the photoelectric conversion efficiency can be improved effect). Particularly, since the second passivation film 21 of the present embodiment is a silicon nitride having a refractive index of 2.4 or more including silicon more than the stoichiometric ratio (Si: N = 3: 4, Si3N4, refractive index: 2.05) 2, the defect density at the interface between the passivation film 21 and the silicon substrate 10 is lowered and the internal resistance is lowered, so that the photoelectric conversion efficiency can be improved. In addition, the film thickness D of the second passivation film 21 of this embodiment is 5 nm or more, and the minimum film thickness capable of achieving the passivation effect is secured.

(3) Since the p + -type semiconductor layer 12 is formed between the second passivation film 21 and the p-type semiconductor layer 13, the p-type semiconductor layer 13 and the p- The recombination speed of the carriers can be lowered by the electric field generated between the layers 12 and the photoelectric conversion efficiency can be improved (BSF effect).

(4) Furthermore, the first passivation film 22 has antireflection property. Therefore, the light irradiated from the outside of the solar cell 1 to the light receiving surface S3 can be efficiently inserted into the inside of the solar cell 1.

(5) In the solar cell 1 of the present embodiment, a second passivation film 21 having a refractive index of 2.4 or more and a thickness (D) of 5 to 30 nm is provided between the back electrode layer 31 and the silicon substrate 10 (Thin dielectric) is formed. The light received from the light receiving surface S3 into the solar cell 1 is not scattered by the plasmons at the interface between the second passivation film 21 and the silicon substrate 10 (alloy layer 11) It is expected. This scattering effect is remarkable when the refractive index of the second passivation film 21 is high. Therefore, by using the second passivation film 21 having a high refractive index (refractive index of 2.4 or more) as in this embodiment, And the photoelectric conversion efficiency can be improved.

&Lt; 2 Modified Example &

 Although the embodiment of the present invention has been described above, the present invention can make various changes other than the above-described ones, without departing from the spirit of the present invention.

Although the solar cell 1 of the single crystal silicon type has been described in the above embodiment, the present invention can be applied to a polycrystalline silicon solar cell.

In the above embodiment, the description has been given of the solar cell 1 in which the p-type is the first conductivity type in the present invention and the n-type is the second conductivity type in the present invention. However, The present invention can be applied to a solar cell.

In the above embodiment, the description has been given of the solar cell 1 in which textures TX1 and TX2 are formed on both principal planes S1 and S2 of the silicon substrate 10. However, Only the main surface on one side may be formed, and it may not be formed.

In the above embodiment, silicon nitride is used as the first passivation film 22 and the second passivation film 21. However, the present invention is not limited thereto. For example, an aluminum oxide film (alumina) may be employed in place of the silicon nitride film 30.

In the above embodiment, the alloy layer 11 is formed by the manufacturing process, but this is not an essential structure of the present invention.

1: solar cell 10: silicon substrate
11: alloy layer 12: p + -type semiconductor layer
13: p-type semiconductor layer 14: n-type semiconductor layer
21: second passivation film 22: first passivation film
31: back electrode layer 32: surface electrode layer
32a: surface electrode D: film thickness
S1: first main surface S2: second main surface
S3: Light receiving surface TX1, TX2: Texture

Claims (8)

A first passivation film; and a second passivation film formed on the light-emitting side of the first main surface opposite to the first main surface on the light-receiving side from the second main surface side A solar cell according to claim 1,
A second passivation film having a film thickness of 5 to 30 nm is formed between the back electrode layer and the first semiconductor layer,
The electrode material of the back electrode layer is diffused to the first semiconductor layer through the second passivation film so that the first semiconductor layer and the back electrode layer are electrically connected to each other and the second passivation film and the first semiconductor layer And a high-concentration semiconductor layer of a first conductivity type having a first conductivity type impurity concentration higher than that of the first semiconductor layer is formed between the first semiconductor layer and the second semiconductor layer. The method according to claim 1,
Wherein the first passivation film has antireflection properties. The method according to claim 1 or 2,
Wherein the second passivation film is made of silicon nitride. The method of claim 3,
And the refractive index of the second passivation film is 2.4 or more. (a) introducing an impurity of the second conductivity type from the first main surface side of the light receiving surface side of the two major surfaces of the first conductivity type semiconductor silicon substrate to form a first semiconductor layer of the first conductivity type, A pn junction forming step of forming a pn junction of the second semiconductor layer of the second conductivity type present on one semiconductor layer,
(b) a passivation film forming step of forming a first passivation film on the first main surface and forming a second passivation film on a second main surface of the substrate,
(c) an electrode forming step of forming a surface electrode layer on the first passivation film and forming a back electrode layer on the second passivation film,
(d) a firing step of firing the surface electrode layer and the back electrode layer, the method comprising the steps of:
Wherein the film thickness of the second passivation film formed in the step (b) is within a range of 5 to 30 nm,
The step (d)
d-1) heating the surface electrode layer to penetrate the electrode material of the surface electrode layer through a part of the first passivation film to reach the second semiconductor layer; and forming the surface electrode formed by the arrival and the second semiconductor layer A conduction step for conduction,
d-2) heating the back electrode layer to diffuse the electrode material of the back electrode layer to the first semiconductor layer through the second passivation film to conduct the first semiconductor layer and the back electrode layer, And a diffusion step of forming a first conductivity type high concentration semiconductor layer having a first conductivity type impurity concentration higher than that of the first semiconductor layer between the passivation film and the first semiconductor layer, A method of manufacturing a solar cell. The method of claim 5,
Wherein the first passivation film has anti-reflection properties. The method according to claim 5 or 6,
Wherein the second passivation film is made of silicon nitride. The method of claim 7,
Wherein the refractive index of the second passivation film is 2.4 or more.

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