JP2015118979A - Solar cell and method of manufacturing solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solar cell in which photoelectric conversion efficiency is enhanced by reducing the contact resistance, and to provide a method of manufacturing a solar cell in which the masking process is reduced.SOLUTION: In a solar cell having, on the first principal surface of a first conductivity type semiconductor substrate, a first conductivity type layer of the same conductivity type as the first conductivity type and a second conductivity type layer of the conductivity type opposite from the first conductivity type, irregularities are provided on the surface of the first conductivity type layer and the second principal surface of the semiconductor substrate.

Description

  The present invention relates to a solar cell and a method for manufacturing a solar cell.

  There is a back electrode type solar cell as a solar cell having a potentially high photoelectric conversion efficiency. FIG. 4 is a schematic cross-sectional view of a general back electrode type solar cell. As shown in FIG. 4, the back electrode type solar cell 200 has a structure in which a base layer 205 and an emitter layer 203 are arranged in the same plane with respect to a semiconductor substrate 201 such as silicon, and positive and negative are formed on these layers. Electrodes 209 and 210 are arranged. As shown in FIG. 4, since it is necessary to provide two diffusion layers (emitter layer 203 and base layer 205) in the same plane, a diffusion mask is formed with a silicon oxide film or the like in the manufacturing process to avoid mutual diffusion. It is necessary to do.

  On the light receiving surface side, fine unevenness 204a called texture is usually formed for reducing the reflectance, and an antireflection film 208 is further provided thereon. A back surface passivation layer 207 is provided on the back surface. As described above, since all the electrodes are disposed on the back surface side, loss of incident light due to the electrodes is eliminated, and high photoelectric conversion efficiency is exhibited. In order to further increase the conversion efficiency, an electric field layer (FSF (Front Surface Field) layer 206) having the same conductivity type as the substrate may be provided on the substrate surface. The FSF layer is a known method in Patent Documents 1 to 3 and the like.

  A thermal diffusion method is widely used as a method for forming the emitter layer, the base layer, and the FSF layer. For example, when an emitter layer is formed on a substrate, the substrate is put in a heat treatment furnace, and when the substrate is n-type, it is a p-type diffusion source, such as B, Al, Ga, etc. n when the substrate is p-type A diffusion layer is formed by using P, As, Sb, or the like as the diffusion source of the mold and allowing the diffusion source to stay for a predetermined temperature and time and thermally diffuse from the surface of the substrate.

JP-A-3-285360 JP 2008-186927 A JP 2011-159783 A JP 2010-161310 A

  In the back electrode type solar cell, the collection efficiency of photogenerated carriers is improved when the area occupied by the base layer 205 is smaller. However, as the base area is reduced, the contact area with the electrode decreases and the contact resistance increases, resulting in a decrease in conversion efficiency. On the other hand, in order to improve the adhesion to the electrode, it is preferable that the surface area be large. Accordingly, in order to increase the conversion efficiency, it is necessary to increase the surface area of the base layer and maintain the contact resistance while reducing the base area.

  Further, the back electrode type solar cell has a problem that the number of man-hours is increased because the mask process is increased in order to avoid mutual diffusion as described above. On the other hand, Patent Document 4 discloses an excellent invention in which a passivation film on the back surface is used as a mask for forming a light receiving surface texture. However, even if this method is used, the mask forming and removing steps are generated twice, which is not a simple method.

  This invention is made | formed in view of the said problem, and it aims at providing the solar cell which reduced contact resistance and improved the photoelectric conversion efficiency. Moreover, it aims at providing the manufacturing method of a solar cell with few mask processes.

In order to solve the above problems, in the present invention, a first conductivity type layer of the same conductivity type as the first conductivity type and the first conductivity type on the first main surface of the semiconductor substrate of the first conductivity type. A solar cell having a second conductivity type layer opposite to the conductivity type,
Provided is a solar cell having irregularities on the surface of the first conductivity type layer and the second main surface of the semiconductor substrate.

  In such a solar cell, the area of the first conductivity type layer (base area) with respect to the entire first main surface (back surface) is reduced while increasing the surface area of the first conductivity type layer (base layer). Can do. As a result, a solar cell with reduced contact resistance and increased photoelectric conversion efficiency can be obtained.

  Moreover, it is preferable that the height of the unevenness is 1 to 50 μm.

  It is particularly preferable for the solar cell of the present invention to have such height irregularities.

  Moreover, it is preferable that the said unevenness | corrugation is a texture.

  With such a solar cell, the reflectance of the second main surface can be further reduced.

  Moreover, it is preferable that the surface of said 2nd conductivity type layer does not have an unevenness | corrugation.

  Such a solar cell is more preferable as a back electrode type solar cell.

Furthermore, in the present invention, a step of forming a second conductivity type layer of a conductivity type opposite to the first conductivity type on at least a part of the first main surface of the first conductivity type semiconductor substrate;
Partially forming a mask on the first main surface;
Forming irregularities on the second main surface on the semiconductor substrate and on the first main surface where the mask is not formed;
And a step of forming a first conductivity type layer of the same conductivity type as the first conductivity type on the first main surface of the portion where the irregularities are formed. provide.

  With such a solar cell manufacturing method, a solar cell with reduced contact resistance and increased photoelectric conversion efficiency can be stably obtained. Moreover, a mask process can be reduced compared with the manufacturing method of the conventional back electrode type solar cell. As a result, manufacturing costs can be reduced and productivity can be improved.

  In the step of forming the second conductivity type layer, the second conductivity type layer is formed on the entire surface of the first main surface, and in the step of forming the mask, the first conductivity type layer is formed. In addition to the above, it is preferable to form the mask.

  With such a method of manufacturing a solar cell, it is not necessary to form a mask on the first main surface or the like when forming the second conductivity type layer (emitter layer), so that the number of manufacturing steps can be further reduced.

  In the step of forming the second conductivity type layer, the second conductivity type layer is partially formed on the first main surface, and in the step of forming the mask, the second conductivity type layer is formed on the second conductivity type layer. It is preferable to form a mask.

  If it is the manufacturing method of such a solar cell, the 2nd conductivity type layer of a desired pattern can be previously formed in a 1st main surface.

  Moreover, it is preferable to make the said unevenness into a texture.

  By making the unevenness as a texture, a solar cell in which the reflectance of the second main surface is further reduced can be obtained.

  The texture is preferably formed by immersing the semiconductor substrate in an alkaline solution.

  With such a method, a texture can be easily formed.

  The first conductive type layer and the second conductive type layer are preferably formed by thermal diffusion.

  Such a method is preferable in terms of manufacturing cost.

  If it is the solar cell of this invention, the occupation area (base area) of the 1st conductivity type layer with respect to the whole 1st main surface can be made small, enlarging the surface area of a 1st conductivity type layer (base layer). As a result, a solar cell with reduced contact resistance and increased photoelectric conversion efficiency can be obtained. Further, according to the method for manufacturing a solar cell of the present invention, in the back electrode type solar cell, the base layer and the FSF layer can be formed at a time while simplifying the process. The surface area of the base region increases and the contact resistance with the electrode is kept low. Therefore, the solar cell obtained by this has high photoelectric conversion efficiency.

It is a cross-sectional schematic diagram which shows an example of the solar cell of this invention. It is a flowchart which shows an example of the embodiment of the manufacturing method of the solar cell of this invention. It is a flowchart which shows another example of the embodiment of the manufacturing method of the solar cell of this invention. It is a cross-sectional schematic diagram of a general back electrode type solar cell.

The present invention will be described in detail below.
As described above, there is a need for solar cells that have reduced contact resistance and increased photoelectric conversion efficiency.

As a result of intensive studies to achieve the above object, the present inventors have found that the first conductivity type of the same conductivity type as the first conductivity type is formed on the first main surface of the first conductivity type semiconductor substrate. A solar cell having a mold layer and a second conductivity type layer opposite to the first conductivity type,
The solar cell having irregularities on the surface of the first conductivity type layer and the second main surface of the semiconductor substrate was found to have low contact resistance and excellent photoelectric conversion efficiency, and the solar cell of the present invention was completed.

  Furthermore, as described above, there is a need for a method for manufacturing a solar cell with few mask processes.

As a result of intensive studies to achieve the above object, the present inventors have found that at least a part of the first main surface of the semiconductor substrate of the first conductivity type has a conductivity opposite to that of the first conductivity type. Forming a second conductive type layer of the mold;
Partially forming a mask on the first main surface;
Forming irregularities on the second main surface on the semiconductor substrate and on the first main surface where the mask is not formed;
A method of manufacturing a solar cell having a step of forming a first conductivity type layer of the same conductivity type as the first conductivity type on the first main surface of the portion where the unevenness is formed has few masking steps. The present invention was completed by finding that it is a method for producing a solar cell.

  In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention and how to implement it in specific embodiments. However, it will be understood that the invention may be practiced without these specific details. In the following description, well-known methods, procedures, and techniques are not shown in detail in order not to obscure the present invention. The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto. The drawings included and described herein are schematic and are not limiting the scope of the invention. Also, in the drawings, the size of some of the elements is exaggerated for illustrative purposes and therefore is not to scale.

[Solar cell]
Hereinafter, although the solar cell of this invention is demonstrated using FIG. 1 taking the case of an n-type board | substrate as an example, this invention is not limited to this. Hereinafter, the first conductivity type layer is also referred to as a base layer, the second conductivity type layer as an emitter layer, the first main surface as a back surface, and the second main surface as a surface or a light receiving surface.

  As described above, the solar cell of the present invention has irregularities on the surface of the first conductivity type layer on the first main surface and the second main surface of the semiconductor substrate, that is, the surface of the base layer on the back surface of the semiconductor substrate. The light receiving surface has fine irregularities. With such a solar cell, the area occupied by the base layer with respect to the entire back surface can be reduced while increasing the surface area of the base layer. As a result, a solar cell with reduced contact resistance and increased photoelectric conversion efficiency can be obtained.

  FIG. 1 is a schematic cross-sectional view showing an example of the solar cell of the present invention. As shown in FIG. 1, a solar cell 100 of the present invention has a structure in which a base layer 105 and an emitter layer 103 are arranged in the same plane with respect to a semiconductor substrate 101 made of silicon or the like, and positive and negative are formed on these layers. Electrodes 109 and 110 are arranged. Further, unevenness 104 a is formed on the light receiving surface, and unevenness 104 b is formed on the surface of the base layer 105. Further, normally, an FSF layer 106 is formed on the light receiving surface. Further, an antireflection film 108 is provided on the FSF layer 106, and a back surface passivation layer 107 is provided on the back surface.

  Moreover, it is preferable that the uneven | corrugated height is 1-50 micrometers. It is particularly preferable for the solar cell of the present invention to have such height irregularities. When the thickness is in the range of 1 to 50 μm, the antireflection effect is large and it can be formed relatively easily.

  Moreover, it is preferable that an unevenness | corrugation is a texture. With such a solar cell, the reflectance of the second main surface can be further reduced.

  Moreover, it is preferable that the surface of said 2nd conductivity type layer does not have an unevenness | corrugation. Such a solar cell is more preferable as a back electrode type solar cell. This is because, during power generation, minority carriers generated in the emitter layer recombine on the surface. That is, if the unevenness is eliminated and the surface area is reduced, the possibility of recombination is reduced, leading to an improvement in photoelectric conversion efficiency.

[Method for manufacturing solar cell]
Hereinafter, an example of a method for manufacturing a solar cell according to the present invention will be described with reference to FIGS. 2 and 3 taking an n-type substrate as an example, but the present invention is not limited to this.

  FIG. 2 is a flowchart showing an example of an embodiment of the method for manufacturing a solar cell of the present invention, and includes a step of partially forming a second conductivity type layer (emitter layer) on the first main surface (back surface). FIG. FIG. 3 is a flowchart showing another example of the embodiment of the method for manufacturing a solar cell according to the present invention, and a process of forming the second conductivity type layer (emitter layer) on the entire surface of the first main surface (back surface). FIG.

  First, as shown in the step (2-a) of FIG. 2 and the step (3-a) of FIG. 3, high purity silicon is doped with a group V element such as phosphorus, arsenic, and antimony, and the specific resistance is 0.1. Slicing damage on the surface of an as-cut single crystal {100} n-type silicon substrate 101 of ˜5 Ω · cm, high concentration alkali such as sodium hydroxide or potassium hydroxide at a concentration of 5 to 60%, or hydrofluoric acid and nitric acid Etching is performed using a mixed acid or the like. The single crystal silicon substrate may be produced by either the CZ method or the FZ method, and the etching step is not necessarily required if subsequent dopant diffusion can be performed with good reproducibility. Further, the substrate is not necessarily a single crystal and may be a polycrystal. However, in the case of a polycrystal, a single crystal is preferable for aiming at high efficiency because the lifetime of minority carriers is small.

Next, an emitter layer (second conductivity type layer) 103 is formed on the back surface of the n-type substrate 101. The emitter layer may be formed in a pattern, or may be formed on the entire back surface for later reasons. The emitter layer can be formed by epitaxial film formation or an implantation (ion implantation) method of accelerating the dopant element and irradiating the substrate, but the thermal diffusion method is preferable from the viewpoint of cost. As the diffusion source, boron, aluminum, gallium or the like can be used. When boron is used, a diffusion source such as BBr ₃ is introduced into a heat treatment furnace together with a carrier gas and diffused, or a boron source such as boric acid is dissolved in a solvent and applied to a substrate for heat treatment. A diffusion method or the like can be used.

Here, the case where the emitter layer is formed on the entire back surface of the substrate will be described below.
As shown in the step (3-d) of FIG. 3, the two substrates 101 and 101 ′ are placed in a superposed state in a heat treatment furnace, together with a diffusion source such as BBr _{3 and} a carrier gas such as argon and nitrogen. By performing heat treatment at 900 to 1100 ° C. for about 1 to 60 minutes, the emitter layers 103 and 103 ′ can be formed on the entire back surface (two-layer diffusion). The emitter layer can also be formed on the entire back surface by applying a coating agent in which boric acid or the like is dissolved in pure water or alcohol on the back surface and performing heat treatment at 900 to 1100 ° C. for about 1 to 60 minutes. At this time, it is preferable to carry out the above two-layer diffusion because the wraparound of boron to the light receiving surface can be reduced and the productivity can be improved.

  With such a method, since it is not necessary to form a mask on the back surface or the like when forming the emitter layer, the number of manufacturing steps can be further reduced.

Next, a method for forming the emitter layer in a pattern (partially) will be described below.
The emitter layer may be formed in a pattern. In the case of pattern formation, a mask (diffusion mask) is required. As the diffusion mask, a silicon oxide film, a silicon nitride film or the like can be used. A chemical vapor deposition (CVD) method can be used for forming the silicon nitride film, and a CVD method or a thermal oxidation method can be used for forming the silicon oxide film. As shown in step (2-b) of FIG. 2, after these methods are used to form diffusion masks 102a and 102b on the entire back surface, photolithography is performed as shown in step (2-c) of FIG. Only the portion where the emitter is to be formed is opened using a method or etching paste. The pattern may be parallel lines with a period of 0.5 to 2 mm, for example, but may be periodically scattered instead of the line, or the substantially entire surface may be an emitter and non-emitter regions may be scattered. After opening, as shown in step (2-d) of FIG. 2, emitter diffusion is performed using the above method to form the emitter layer 103.

  After the emitter layer is diffused, if there is an oxide film on the light receiving surface, it must be removed. Further, when diffusion is performed, a glass layer is formed on the surface. These oxide film and glass layer are removed with hydrofluoric acid or the like. For example, it can be removed by immersing the entire substrate in an aqueous hydrofluoric acid solution having a concentration of 1 to 10% for a short time. Note that this removal step is not necessarily a necessary step when there is no oxide film on the light receiving surface.

  Next, a mask is partially formed on the first main surface (back surface) to prepare for forming the base layer (first conductivity type layer) 105. As described above, a silicon oxide film, a silicon nitride film, or the like can be used as the diffusion mask. A CVD method can be used for forming the silicon nitride film, and a CVD method or a thermal oxidation method can be used for forming the silicon oxide film. After these methods are used to form a mask on the entire back surface, only the portion where the base is to be formed is opened using a photolithographic method or an etching paste. When the thermal oxidation method is used, an oxide film is also formed on the light receiving surface, and this is also removed by the same method. The pattern can be parallel lines with a period of 0.5 to 2 mm, for example, but may be periodically scattered instead of the line.

  When the emitter layer is formed on the entire surface, as shown in step (3-e) of FIG. 3, a mask 102c is formed in addition to the portion for forming the base layer. When the emitter layer is partially formed, a mask 102c is formed on the partially formed emitter layer as shown in step (2-e) of FIG.

  Subsequently, as shown in the step (2-f) of FIG. 2 and the step (3-f) of FIG. 3, the masks on the second main surface (light receiving surface) and the first main surface (back surface) of the semiconductor substrate are formed. The minute irregularities 104a and 104b are formed on the portion that is not formed (the portion where the base is formed). By forming the unevenness 104a on the light receiving surface, the reflectance of the light receiving surface can be reduced. By forming the unevenness 104b in the base formation portion, the surface area of the base formation portion can be increased.

The minute irregularities are formed by using either a gas phase etching method using an etching gas such as CF ₄ or CHF ₃ or a liquid phase etching method in which the substrate is immersed in an alkaline or acidic solution. Can do. In particular, when an alkaline solution is used, it utilizes the property that the etching rate varies depending on the plane orientation of the single crystal substrate. When a {100} substrate is used, a regular tetrahedral fine pyramid structure called a texture is used. Can be formed innumerably on the substrate surface. The uneven shape formed by any one of these methods can be confirmed by, for example, a scanning electron microscope. The difference between the highest point and the lowest point in the image obtained by the electron microscope can be regarded as the unevenness height.

  The texture is immersed for about 10 to 30 minutes in an alkali solution (concentration 1 to 10%, temperature 60 to 100 ° C.) such as heated sodium hydroxide, potassium hydroxide, potassium carbonate, sodium carbonate, sodium hydrogen carbonate, etc. It is formed. In many cases, a predetermined amount of 2-propanol is dissolved in the solution to promote the reaction.

  As a result, the texture is formed only in the portion where the mask is opened. That is, as shown in step (2-f) of FIG. 2, the emitter layer is not altered, and a texture is formed only on the base portion and the light receiving surface. Further, when the emitter is formed on the entire back surface in the above description, as shown in step (3-f) of FIG. 3, the diffusion layer in the opening is removed by this etching process.

  After texture formation, washing is performed in an acidic aqueous solution of hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, or the like, or a mixture thereof. Hydrogen peroxide water may be mixed with any of these acid solutions and heated, and in this case, cleanliness is improved, which is preferable.

  Subsequently, as shown in the step (2-g) of FIG. 2 and the step (3-g) of FIG. 3, the base layer 105 is formed. The base layer can also be formed by epitaxial film formation or an implantation method in which the substrate is accelerated to irradiate the substrate, but the thermal diffusion method is preferable from the viewpoint of cost. As a diffusion source, phosphorus, arsenic, antimony, or the like can be used. When phosphorus is used, a diffusion source such as phosphorus oxychloride is introduced into a heat treatment furnace together with a carrier gas and diffused, or a phosphorus source such as phosphoric acid is dissolved in a solvent and applied to a substrate for heat treatment. A coating diffusion method or the like can be used.

  The substrate is placed in a heat treatment furnace and subjected to heat treatment at 800 to 1000 ° C. for about 1 to 60 minutes together with a diffusion source such as phosphorus oxychloride and a carrier gas such as argon and nitrogen, whereby the base layer 105 is formed on the back opening. The FSF layer 106 can be simultaneously formed on the light receiving surface. Also, the base layer can be formed by applying a coating agent in which phosphoric acid or the like is dissolved in pure water or alcohol on the back surface and performing a heat treatment at 800 to 1000 ° C. for about 1 to 60 minutes. In this case, phosphorus diffuses to the light receiving surface by autodoping and forms a thin diffusion layer, which is preferable as the FSF layer.

Next, as shown in the step (2-h) of FIG. 2 and the step (3-h) of FIG. 3, the antireflection film 108 is formed on the light receiving surface. The antireflection film such as SiNx film or SiO ₂ film by a plasma CVD apparatus can be used, the thermal oxide film can be used. A film thickness of 85 to 105 nm is preferable because the effect of reducing the reflectance is maximized. In the case of a SiNx film, monosilane (SiH ₄ ) and ammonia (NH ₃ ) are often mixed and used as the reaction gas. However, nitrogen can be used instead of NH ₃ , and the process pressure In some cases, hydrogen is mixed into the reaction gas in order to promote the adjustment, dilution of the reaction gas, and further to promote the bulk passivation effect of the substrate when polycrystalline silicon is used for the substrate. In the case of SiO ₂ , a method of decomposing and using tetraethoxysilane is common.

  Next, as shown in the step (2-h) of FIG. 2 and the step (3-h) of FIG. 3, a back surface passivation layer 107 is formed by forming a SiNx film or the like on the back surface and performing passivation. When a thermal oxide film is used as the antireflection film, additional film formation on the back surface is unnecessary.

  Finally, as shown in step (2-i) in FIG. 2 and step (3-i) in FIG. 3, electrodes are formed. For electrode formation, a vapor deposition method, a sputtering method, a plating method, an ink jet method or the like can be used, but a printing method is preferable from the viewpoint of cost. When the screen printing method is used, an Ag paste in which Ag powder and glass frit are mixed with an organic binder is printed in a comb-like pattern, for example. After the electrode printing, Ag powder is penetrated through the surface insulating film by firing (fire through), and the electrodes 109 and 110 are electrically connected to the semiconductor substrate 101 such as silicon. Firing is usually performed by treating at a temperature of 700 to 900 ° C. for 5 to 30 minutes.

  According to the method for manufacturing a solar cell of the present invention, the base layer and the FSF layer can be formed at one time while simplifying the process, and furthermore, even if the base area is reduced, unevenness (for example, texture) exists, so the surface area is As a result, the contact resistance with the electrode is kept low. Therefore, the solar cell obtained by this has high photoelectric conversion efficiency. If it is the manufacturing method of the solar cell of this invention, since the process is simplified as mentioned above, the solar cell which has a high output can be manufactured at low cost than before.

  As described above, the case of an n-type substrate has been described as an example, but even in the case of a p-type substrate, the above dopant material may be used in reverse, and there is no problem.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to these Examples.

  In order to confirm the effectiveness of this invention, the solar cell was produced with the manufacturing method of the solar cell of this invention.

[Example]
The damage layer was removed with a hot concentrated potassium hydroxide aqueous solution on eight phosphorus-doped {100} n-type as-cut silicon substrates having a substrate thickness of 200 μm and a specific resistance of 1 Ω · cm.

Next, a back emitter layer was formed by a vapor phase diffusion method using BBr ₃ . The two substrates were put into a heat treatment furnace, and heat treatment was performed at 1000 ° C. for 30 minutes in a BBr ₃ atmosphere using argon as a carrier gas. The sheet resistance measured by the four probe method was 35Ω.

  Next, a thermal oxide film was formed as a diffusion mask. A heat treatment was performed in an oxygen atmosphere at a temperature of 1050 ° C. for 2 hours, and an oxide film of about 110 nm was formed on both surfaces of the substrate. Subsequently, a resist was spin coated on the back surface, exposed and developed in a pattern, and immersed in 10% concentration hydrofluoric acid to remove the base layer forming portion and the oxide film on the light receiving surface. The pattern was a 1.4 mm period and the opening was a parallel line of 200 μm.

  After opening, it was immersed in a 72 ° C. aqueous potassium hydroxide / 2-propanol solution to form a texture, and subsequently washed in a hydrochloric acid / hydrogen peroxide mixed solution heated to 75 ° C. Thereby, it was visually confirmed that the texture was formed only in the openings (base layer forming portion and light receiving surface) as a decrease in reflectance. Subsequently, vapor phase diffusion was performed using phosphorus oxychloride at a temperature of 850 ° C. for 40 minutes, and a base layer was formed at the back opening and an FSF layer was simultaneously formed at the light receiving surface.

  Next, a silicon nitride film having a thickness of 95 nm was formed on the light receiving surface and the back surface by using plasma CVD. The reaction gas was monosilane and ammonia, and the film forming temperature was 400 ° C.

  Finally, Ag paste was screen printed in a comb shape on each of the base layer and the emitter layer, dried, and fired in an air atmosphere at 780 ° C. to complete a solar cell.

[Comparative example]
As a comparative example, a cell in which no texture was formed on the base layer was also produced. Phosphorus diffusion was performed without forming a texture after the above-described diffusion mask formation and mask opening, and a silicon nitride film having a thickness of 95 nm was formed by plasma CVD only on the back surface. Thereafter, a texture of the light receiving surface was formed, a silicon nitride film was formed on the light receiving surface, and finally an electrode was formed by screen printing.

The current-voltage characteristics were measured under pseudo-sunlight conditions of spectrum AM1.5G (global) and 100 mW per illuminance 1 cm ² . The average value of each condition is shown in Table 1 below.

  Compared to the comparative example, which is a cell in which no texture is formed on the base layer, in the example, the short-circuit current and the open-circuit voltage are improved by forming the FSF layer on the light receiving surface, and further, the texture is formed on the surface of the base layer. Contact resistance is improved and form factor is improved.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

100, 200 ... solar cell, 101, 101 ', 201 ... semiconductor substrate,
102a, 102b, 102c ... diffusion mask,
103, 103 ', 203 ... emitter layer (second conductivity type layer),
104a, 104b, 204a ... irregularities 105, 205 ... base layer (first conductivity type layer),
106, 206 ... FSF layer, 107, 207 ... backside passivation layer,
108, 208 ... antireflection film, 109, 110, 209, 210 ... electrode.

Claims (10)

On the first main surface of the semiconductor substrate of the first conductivity type, the first conductivity type layer of the same conductivity type as the first conductivity type and the second conductivity type layer of the conductivity type opposite to the first conductivity type. A solar cell having
A solar cell having irregularities on the surface of the first conductivity type layer and the second main surface of the semiconductor substrate.   The solar cell according to claim 1, wherein the height of the unevenness is 1 to 50 μm.   The solar cell according to claim 1, wherein the unevenness is a texture.   The solar cell according to any one of claims 1 to 3, wherein the surface of the second conductivity type layer has no irregularities. Forming a second conductivity type layer of a conductivity type opposite to the first conductivity type on at least a part of the first main surface of the first conductivity type semiconductor substrate;
Partially forming a mask on the first main surface;
Forming irregularities on the second main surface on the semiconductor substrate and on the first main surface where the mask is not formed;
Forming a first conductivity type layer of the same conductivity type as the first conductivity type on the first main surface of the portion where the irregularities are formed.   In the step of forming the second conductivity type layer, the second conductivity type layer is formed on the entire surface of the first main surface, and in the step of forming the mask, in addition to the portion for forming the first conductivity type layer. The method for manufacturing a solar cell according to claim 5, wherein the mask is formed.   In the step of forming the second conductivity type layer, the second conductivity type layer is partially formed on the first main surface, and in the step of forming the mask, the mask is formed on the second conductivity type layer. It forms, The manufacturing method of the solar cell of Claim 5 characterized by the above-mentioned.   The method for manufacturing a solar cell according to claim 5, wherein the unevenness is textured.   The method of manufacturing a solar cell according to claim 8, wherein the texture is formed by immersing the semiconductor substrate in an alkaline solution.   The method for manufacturing a solar cell according to any one of claims 5 to 9, wherein the first conductive type layer and the second conductive type layer are formed by thermal diffusion.

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