JP2006319170A - Solar cell and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a solar cell capable of keeping the appearance quality high without expressing a discoloration phenomenon in the superficial color of a silver electrode, even if used in the state of a module for a long period of time, and also without generating macro "color unevenness" or "color pattern" in the state of a module. <P>SOLUTION: The solar cell comprises a silicon substrate 10; a diffusion layer 20 formed on the surface of the silicon substrate; an insulating film 30 formed on the diffusion layer consisting of a silicone nitride film, a titanium oxide film, or a silicone oxide film; a surface silver electrode 801 which is formed so that it might fuse and penetrate an insulating film, while burning conductive metal paste material 800 containing silver powder, organic vehicle, glass powder and carbon, and it could come into electrical contact with the diffusion layer; a back-face aluminum electrode 61 formed in the back-face of the silicon substrate; and a back-face silver electrode 71 formed in the back-face of the silicon substrate. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a solar cell having no appearance change over a long period of time and a method for manufacturing the solar cell.

  At present, silicon solar cells are the mainstream of power solar cells used on the earth. In mass production of silicon solar cells, the process flow is simplified as much as possible to reduce the manufacturing cost. It is common. In particular, a method of forming a metal paste by screen printing or the like is employed for electrodes provided in solar cells.

  Initially, the manufacturing method of the conventional solar cell is demonstrated, referring FIG. As shown in FIG. 3A, a p-type Si substrate 10 is prepared and, for example, phosphorus (P) is thermally diffused on the surface to reverse the conductivity type, as shown in FIG. 3B. Then, the n-type diffusion layer 20 is formed. Usually, phosphorus oxychloride (POCl 3) is often used as a phosphorus diffusion source. In general, the n-type diffusion layer 20 is formed on the entire surface of the Si substrate 10. The sheet resistance of the n-type diffusion layer 20 is about several tens of ohms / square, and the thickness of the layer is about 0.3 to 0.5 μm.

  Subsequently, as shown in FIG. 3C, after protecting one surface of the n-type diffusion layer 20 with a resist, an etching process is performed so that the n-type diffusion layer 20 is left only on one main surface of the substrate. The residual resist after the treatment is removed using an organic solvent or the like.

  Next, as shown in FIG. 3D, a silicon nitride film 30 as an insulating film (antireflection film) is formed on the n-type diffusion layer 20 by a plasma CVD method or the like to a thickness of about 700 to 900 mm.

  Next, as shown in FIG. 3E, the aluminum paste 60 and the back surface silver paste 70 are respectively screen-printed and dried at desired positions on the back surface of the substrate. On the silicon nitride film 30, a silver paste 500 serving as a front electrode is screen-printed in the same manner as the back surface, dried, and baked in a near-infrared furnace at 700 ° C. to 900 ° C. for several minutes to several tens of minutes.

  As a result, as shown in FIG. 3 (f), on the back surface side of the substrate 10, aluminum as an impurity diffuses from the aluminum paste into the substrate during firing, and the p + layer 40 containing a high concentration impurity of aluminum is formed. It is formed. This layer is generally called a BSF (Back Surface Field) layer and contributes to the improvement of the energy conversion efficiency of the solar cell. Moreover, after baking, the aluminum paste 60 becomes the back surface aluminum electrode 61, and the back surface silver paste 70 also becomes the back surface silver electrode 71 at the same time. At the time of firing, the boundary between the back surface aluminum electrode 61 and the back surface silver electrode 71 becomes an alloy state and is electrically connected. Most of the back electrode needs to form a p + layer and is occupied by the back aluminum electrode 61. Since the back surface silver electrode 71 cannot be soldered to the back surface aluminum electrode 61, the back surface silver electrode 71 is formed on a part of the back surface as an electrode for connecting solar cells made of copper foil or the like.

  On the other hand, the surface electrode silver paste 500 becomes a surface silver electrode 501 which melts and penetrates the silicon nitride film during firing and takes electrical contact with the n-type diffusion layer. Such a method is generally called fire-through. In a method for manufacturing a semiconductor device in which an insulating film is formed on the surface of a semiconductor substrate having a pn junction, for example, Patent Document 1 discloses a metal paste containing glass having a property of melting an insulating film, for example, lead boron glass. The technique used is disclosed.

  In Patent Document 2, a region having another conductivity type is formed on one main surface side of a semiconductor substrate, an antireflection film is formed on one main surface side of the semiconductor substrate, and the electrode material is made of this antireflection film. In the method of forming a solar cell by coating from above the film, the electrode material contains, for example, lead, boron, silicon, etc., and a glass frit having a softening point of about 300 to 600 ° C., Ti, Bi, Co, Zn, A technique containing one or more of Zr, Fe, and Cr is disclosed.

  In these conventional techniques, a surface silver electrode is formed by fire-through, and then a solder layer is coated on the front and back silver electrodes by further dipping in a flux and then a solder solution. By passing through the above steps, it is said that sufficient characteristics can be obtained in the conversion efficiency of the solar cell and the tensile strength of the silver electrode which is important when the solar cells are connected to each other.

Further, Patent Document 3 discloses a method of manufacturing a semiconductor device in which a silicon nitride film is formed on a Si substrate, a conductive metal paste material is applied and printed thereon, fired, and a surface silver electrode is formed by fire-through. The silicon nitride film is formed by a CVD method, and the conductive metal paste material contains silver powder, an organic vehicle, and glass powder, and the added amount of the glass powder is 1.5% by weight or more with respect to the conductive metal paste material. A technique is disclosed in which the softening point of the glass powder is 450 ° C. to 550 ° C., the content of B ₂ O ₃ in the glass powder is 15% by weight or less, and the firing is performed at 800 to 850 ° C. in a dry air atmosphere. . According to this prior art, the reliability with respect to moisture resistance sufficiently satisfies the JIS standard in a module state, and a highly efficient solar cell can be obtained. In addition, since no solder coat is used, productivity can be greatly improved while lowering manufacturing costs, and lead is not used, which is extremely advantageous from an environmental point of view.

Japanese Patent Laid-Open No. 10-233518 JP 2001-313400 A JP 2004-207493 A

  Solar cells are used outdoors in a sealed module state through an assembly process, which is a subsequent process, and have been used for over 10 years. At that time, appearance quality is one of the reliability. It is important to ensure.

  In the solar cells of Patent Documents 1 and 2, as described above, in general, solder coating has been performed on the surface of the silver electrode in order to ensure moisture resistance. However, since the solder coating uses lead, there is a problem from an environmental point of view. In addition, the presence of the solder coating process has an adverse effect on productivity and manufacturing cost.

  Moreover, in the solar cell of patent document 3, as above-mentioned, while being excellent in moisture resistance, productivity is favorable, while being able to fully suppress manufacturing cost, it does not have a bad influence on global environment. Is obtained. However, since there is no solder coating on the surface of the silver electrode, when used in a module state for a long period of time, the surface color of the silver electrode which is generally glossy at first becomes gradually blackish or yellowish. And so-called discoloration phenomenon appears. This is generally a phenomenon called silver corrosion or sulfidation, and there is a problem that macro appearance of “color unevenness” or “color pattern” occurs in the module state due to the surface discoloration of the silver electrode, and the appearance quality is remarkably deteriorated.

  The present invention has been made in order to solve the above-described problems. The object of the present invention is to prevent the surface color of the silver electrode from causing a discoloration phenomenon even if it is used in a module state for a long time, and to make a macro in the module state. Thus, it is possible to obtain a solar cell that does not generate “color irregularity” or “color pattern” and can maintain high quality of appearance.

  The solar cell according to the present invention includes a silicon substrate, a diffusion layer formed on the silicon substrate, an insulating film formed on the diffusion layer, and a dark color after firing provided on the insulating film. A front surface silver electrode formed to be electrically connected to the diffusion layer by firing a metal paste material, a back surface aluminum electrode formed on the back surface of the silicon substrate, and formed on the back surface of the silicon substrate A back surface silver electrode is provided.

  A method for manufacturing a solar cell according to the present invention is a method for manufacturing a solar cell in which a diffusion layer having an inverted conductivity type is formed on a surface of a silicon substrate, and an antireflection film is formed on the diffusion layer. On the prevention film, a conductive metal paste material that is dark after firing is screen-printed and dried, and is fired in a near-infrared furnace in a dry air atmosphere at 800 ° C. to 850 ° C. for several minutes to ten and several minutes; And a step of forming a surface silver electrode capable of electrically contacting the diffusion layer by melting and penetrating the antireflection film during firing of the conductive metal paste material that is dark after firing. Is.

  Even if the solar cell according to the present invention is used in a module state for a long period of time, the surface color of the silver electrode does not exhibit a discoloration phenomenon, and a macro "color unevenness" or "color pattern" does not occur in the module state. There is an effect that the quality of the appearance can be kept high.

Embodiment 1 FIG.
A solar cell according to Embodiment 1 of the present invention will be described with reference to FIG. 1 is a diagram showing a method of manufacturing a solar cell according to Embodiment 1 of the present invention. In addition, in each figure, the same code | symbol shows the same or equivalent part.

  1, the solar cell according to the first embodiment includes a p-type Si substrate 10, an n-type diffusion layer 20 formed on the surface of the Si substrate 10, and silicon nitride formed on the n-type diffusion layer 20. The conductive metal paste material 800 including the film 30 and silver powder, organic vehicle, glass powder, and carbon powder melts and penetrates the silicon nitride film 30 during firing, and makes electrical contact with the n-type diffusion layer 20. A front surface silver electrode 801 formed so as to be capable of being formed, a back surface aluminum electrode 61 formed on the back surface of the Si substrate 10, and a back surface silver electrode 71 formed on the back surface of the Si substrate 10 are provided.

  First, as shown in FIG. 1A, a p-type Si substrate 10 is prepared. The Si substrate 10 is formed by using, for example, a single crystal manufactured by a pulling method or a polycrystalline silicon substrate manufactured by a casting method, on which a texture that is an uneven structure of an antireflection structure is formed. In the case of a solar cell, a substrate that has been sliced from the ingot formed as described above is often used. In this case, an alkaline aqueous solution such as potassium hydroxide or sodium hydroxide aqueous solution or a mixed solution of hydrofluoric acid and nitric acid is used to remove the substrate surface damage due to the wire saw used for slicing and contamination of the wafer slicing process. Then, the surface of the substrate is etched by about 10 to 20 μm. Furthermore, a step of washing with a mixed solution of hydrochloric acid and hydrogen peroxide may be added to remove heavy metals such as iron adhering to the substrate surface. Then, the texture structure which is an antireflection structure may be formed using alkaline aqueous solutions, such as potassium hydroxide and sodium hydroxide aqueous solution. This state is the Si substrate 10.

  Next, as shown in FIGS. 1B and 1C, an n-type diffusion layer 20 in which, for example, phosphorus (P) is thermally diffused and the conductivity type is inverted is formed on the surface of the Si substrate 10. Usually, phosphorus oxychloride (POCl 3) is often used as a phosphorus diffusion source. In general, the n-type diffusion layer 20 is formed on the entire surface of the Si substrate 10. The sheet resistance of the n-type diffusion layer 20 is about several tens of ohms / square, and the thickness of the layer is about 0.3 to 0.5 μm. The depth of the n-type diffusion layer 20 can be easily changed by controlling the diffusion temperature and time. Subsequently, after protecting one surface of the n-type diffusion layer 20 with a resist, an etching process is performed so that the n-type diffusion layer is left only on one main surface of the Si substrate 10. The residual resist after the treatment is removed using an organic solvent or the like. Separately, a liquid coating material containing phosphorus, such as PSG (Phospho-Silicate-Glass), is applied to only one surface of the Si substrate 10 by spin coating or the like and annealed under appropriate conditions. Although a diffusion method can be used, if there is a possibility that an n-type diffusion layer may be formed up to the back surface of the Si substrate 10, it is possible to improve the integrity by adopting a method using a resist.

  Next, as shown in FIG. 1D, a silicon nitride film 30 that functions as an insulating film (for example, an antireflection film) is formed on the n-type diffusion layer 20. Since the silicon nitride film 30 reduces the surface reflectance of the solar cell with respect to the incident light, the generated current can be greatly increased. Although the thickness of the silicon nitride film 30 depends on its refractive index, for example, in the case of a refractive index of about 1.9 to 2.0, about 700 to 900 mm is appropriate. The silicon nitride film 30 is formed using a low pressure thermal CVD method or a plasma CVD method. In the case of the thermal CVD method, dichlorosilane (SiCl 2 H 2) and ammonia (NH 3) gas can be used as raw materials, and film formation may be performed at a temperature of 700 ° C. or higher. In this method, since the source gas is thermally decomposed at a high temperature, the silicon nitride film 30 contains almost no hydrogen, the composition ratio of Si and N becomes Si3N4, which is almost stoichiometric, and the refractive index is also about 1. The range is from .96 to 1.98. Therefore, such a silicon nitride film 30 has a feature that the film quality (film thickness, refractive index) does not change even if a heat treatment is applied in a later step, so that the film quality is extremely dense. In the case of forming by a plasma CVD method, a mixed gas of SiH4 and NH3 is used as a source gas, the source gas is decomposed by plasma, and film formation may be performed at a temperature of 300 to 550 ° C. In the case of this plasma CVD method, film formation is performed at a lower temperature than thermal CVD, hydrogen contained in the source gas is also contained in the silicon nitride film 30, and since the gas decomposition is caused by plasma, the composition ratio of Si and N Has a feature that it can be greatly changed. Specifically, the composition ratio of Si, N, and hydrogen is changed by changing the flow rate ratio of the source gas, the pressure during film formation, the temperature, and the like, and the refractive index is 1.8 to 2.5. A range of silicon nitride film 30 can be formed. In the case of such film quality, when a heat treatment is applied in a later step, the refractive index may change compared to that immediately after the film formation due to a phenomenon such as hydrogen desorption in the electrode firing step. In this case, the silicon nitride film 30 necessary as a solar cell can be obtained by taking into account the film quality change caused by the heat treatment in the subsequent process and determining the film formation conditions.

  On the other hand, in FIG. 1D, a titanium oxide film may be formed instead of the silicon nitride film 30. The titanium oxide film is formed by a thermal CVD method in which an organic titanate (organic liquid material containing titanium) typified by TPT (tetrapropyl titanate) vapor and water vapor are mixed and thermally decomposed at 250 ° C. to 300 ° C. Can do.

  Further, in FIG. 1D, a silicon oxide film may be formed instead of the silicon nitride film 30. The silicon oxide film can be formed by a thermal oxidation method, preferably a thermal CVD method or a plasma CVD method. In the case of the thermal CVD method in this case, for example, a mixed gas of Si2Cl4 and O2 is used as a source gas, and the temperature is 700 to 900 ° C. In the case of the plasma CVD method, for example, a mixed gas of SiH 4 and O 2 is used as a source gas, and the temperature is 200 to 500 ° C.

  Next, as shown in FIGS. 1E and 1F, an aluminum paste 60 and a back surface silver paste 70 are screen-printed at desired positions on the back surface of the Si substrate 10 and dried. Further, on the silicon nitride film 30, a conductive metal paste material 800 to be a front electrode is screen-printed in the same manner as the back surface, dried, and near infrared in a dry air atmosphere at 800 ° C. to 850 ° C. for several minutes to several tens of minutes. Bake in a furnace. In addition, the dry air atmosphere as used in the field of this invention means the air whose dew point is -60 degrees C or less, for example.

  This conductive metal paste material 800 becomes a surface silver electrode 801 capable of melting and penetrating the silicon nitride film 30 during firing and making electrical contact with the n-type diffusion layer 20. In the present invention, in order to achieve a desired effect such as moisture resistance, the firing needs to be performed within this temperature range. On the other hand, on the back surface side of the Si substrate 10, aluminum as an impurity diffuses from the aluminum paste 60 into the Si substrate 10 during firing, and a p + layer 40 containing a high concentration impurity of aluminum is formed.

  After firing, the aluminum paste 60 becomes the back surface aluminum electrode 61 and the back surface silver paste 70 also becomes the back surface silver electrode 71 at the same time. At the time of firing, the boundary between the back surface aluminum electrode 61 and the back surface silver electrode 71 becomes an alloy state and is electrically connected. Most of the back electrode needs to form a p + layer and is occupied by the back aluminum electrode 61. Since the back surface silver electrode 71 cannot be soldered to the aluminum electrode, the back surface silver electrode 71 is formed on a part of the back surface as an electrode for mutually connecting solar cells made of copper foil or the like.

  Conductive metal paste material 800 that is dark after firing in Embodiment 1 of the present invention is obtained by adding carbon powder to a conductive metal paste material made of silver powder, organic vehicle, glass powder, or the like. Silver powder, glass powder, and carbon powder are dispersed in an organic vehicle.

  The particle size of the silver powder is not particularly limited, but it is desirable that the average particle size does not exceed 10 microns, and preferably does not exceed 5 microns. The content of the silver powder in the conductive metal paste material 800 is, for example, 50 to 90% by weight. When the organic vehicle is removed, the content is usually 60 to 99% by weight in the solid component of the conductive metal paste material 800. .

Glass powder has the property of melting and penetrating an insulating film when it is applied, printed, and baked on the insulating film. This glass powder needs to have a softening point of 450 ° C. to 550 ° C. in order to provide long-term reliability with respect to moisture resistance. In addition, the softening point as used in the field of this invention means the value obtained by the fiber elongation method of ASTM C338-57. Most preferably used glass powders are borosilicate frit, such as lead borosilicate frit, bismuth, barium, calcium or other alkaline earth borosilicate frit. However, in order to ensure long-term moisture resistance, the B ₂ O ₃ content in the glass powder composition needs to be 15% by weight or less. The production of such glass frit is well known and is obtained, for example, by melting together glass components in the form of oxides and pouring the molten composition into water to form a frit. The glass is preferably ground in a vibration mill to reduce the frit particle size with water to obtain a substantially uniform size frit. Moreover, the amount of the glass powder in the conductive metal paste material 800 is 1.5% by weight or more, preferably 2.0 to 5.0% by weight. The particle size of the glass powder is preferably 0.5 to 6.0 μm in terms of average particle size.

  Carbon powder is added to keep the electrode dark. For this reason, the particle diameter is not particularly limited, but is preferably smaller than the particle diameter of the silver powder which is a metal powder.

  The organic vehicle in the conductive metal paste material 800 is preferably a non-aqueous inert liquid. The organic vehicle can also contain various additives such as thickeners and stabilizers. A preferable organic medium includes, for example, a combination of 20 parts by weight of ethylene cellulose and 80 parts by weight of texanol. This blending ratio provides a good viscosity for screen printing.

  As described above, the first embodiment is characterized in that the conductive metal paste material 800 includes silver powder, organic vehicle, glass powder, and carbon powder. Therefore, the surface silver electrode 801 is darkened and has a certain level. Even if it is used in a module state for a long time in order to maintain a low resistance value, the surface color of the silver electrode does not exhibit a discoloration phenomenon, and macro “color unevenness” or “color pattern” does not occur in the module state. There is an effect of obtaining a high-quality solar cell module.

Embodiment 2. FIG.
A solar cell according to Embodiment 2 of the present invention will be described with reference to FIG. FIG. 2 is a diagram showing a method for manufacturing a solar cell according to Embodiment 2 of the present invention.

  2, the solar cell according to the second embodiment includes a p-type Si substrate 10, an n-type diffusion layer 20 formed on the surface of the Si substrate 10, and silicon nitride formed on the n-type diffusion layer 20. The conductive metal paste material 900 including the film 30 and the silver powder, the organic vehicle, and the glass powder can melt and penetrate the silicon nitride film 30 during firing, and can be in electrical contact with the n-type diffusion layer 20. The surface silver electrode 901 formed as described above, and the surface silver electrode 801 formed by firing a conductive metal paste material 800 containing silver powder, organic vehicle, glass powder, and carbon powder on the surface silver electrode 901. A back surface aluminum electrode 61 formed on the back surface of the Si substrate 10 and a back surface silver electrode 71 formed on the back surface of the Si substrate 10 are provided.

  2A to 2D are exactly the same as those in the first embodiment.

  As shown in FIGS. 2E and 2F, an aluminum paste 60 and a back surface silver paste 70 are screen-printed at desired positions on the back surface of the Si substrate 10 and dried. Further, on the silicon nitride film 30, a conductive metal paste material 900 to be a first surface electrode is screen-printed and dried in the same manner as the back surface.

  Next, the conductive metal paste material 800 which becomes the surface electrode of the second layer is screen-printed in the same manner as the back surface, dried, and in a near-infrared furnace in a dry air atmosphere at 800 ° C. to 850 ° C. for several minutes to ten and several minutes. Bake with. In addition, the dry air atmosphere as used in the field of this invention means the air whose dew point is -60 degrees C or less, for example.

  Of the conductive metal paste materials 900 and 800, the conductive metal paste material 900 melts and penetrates the silicon nitride film 30 during firing, and is surface silver capable of making electrical contact with the n-type diffusion layer 20. It becomes the electrode 901. In addition, the conductive metal paste material 800 becomes a surface silver electrode 801 capable of making electrical contact with the n-type diffusion layer 20 through the surface silver electrode 901. In order to achieve a desired effect such as moisture resistance, the firing needs to be performed within this temperature range.

  On the other hand, on the back surface side of the Si substrate 10, aluminum as an impurity diffuses from the aluminum paste 60 into the Si substrate 10 during firing, and a p + layer 40 containing a high concentration impurity of aluminum is formed.

  After firing, the aluminum paste 60 becomes the back surface aluminum electrode 61 and the back surface silver paste 70 also becomes the back surface silver electrode 71 at the same time. At the time of firing, the boundary between the back surface aluminum electrode 61 and the back surface silver electrode 71 becomes an alloy state and is electrically connected. Most of the back electrode needs to form a p + layer and is occupied by the back aluminum electrode 61. Since the back surface silver electrode 71 cannot be soldered to the aluminum electrode, the back surface silver electrode 71 is formed on a part of the back surface as an electrode for mutually connecting solar cells made of copper foil or the like.

  The conductive metal paste material 900 according to the second embodiment of the present invention is a conductive metal paste material containing silver powder, organic vehicle, and glass powder, and the conductive metal paste material 800 that is dark after firing is silver Carbon powder is added to a conductive metal paste material made of powder, organic vehicle, glass powder or the like. Silver powder, glass powder, and carbon powder are dispersed in an organic vehicle.

  As described above, since the conductive metal paste material 800 contains carbon powder for darkening, the resistance value of the conductive metal paste material 800 is higher than that of the conductive metal paste material 900. In the solar cell, it is desirable that the resistance value of the surface silver electrode be as low as possible in order to effectively capture the charge generated in the substrate. Therefore, it is better to form a two-layer structure in which the lower layer is the surface silver electrode 901 and the upper layer is the surface silver electrode 801, rather than the single surface silver electrode 801 as shown in the first embodiment. In addition, the surface color can be darkened.

Embodiment 3 FIG.
In Embodiments 1 and 2 above, carbon powder is included in the conductive metal paste material 800 to darken the surface silver electrode 801. However, it is not necessary to be a powder at all, including particles, carbon. If it is a contained material, the form is arbitrary and there exists the same effect.

Embodiment 4 FIG.
In the above first to third embodiments, carbon is contained in the conductive metal paste material 800 in order to darken the surface silver electrode 801 and maintain a certain low resistance value, but it is necessary to stick to carbon. Even if, for example, a pigment exhibiting a silicon substrate color is added, the same effect can be obtained.

It is a figure which shows the manufacturing method of the solar cell which concerns on Embodiment 1 of this invention. It is a figure which shows the manufacturing method of the solar cell which concerns on Embodiment 2 of this invention. It is a figure which shows the manufacturing method of the conventional solar cell.

Explanation of symbols

  10 p-type Si substrate, 20 n-type diffusion layer, 30 silicon nitride film, 40 p + layer, 60 aluminum paste, 61 back surface aluminum electrode, 70 back surface silver paste, 71 back surface silver electrode, 800 conductive metal that is dark after firing Paste material, 801 dark surface silver electrode, 900 conductive metal paste material, 901 surface silver electrode.

Claims (8)

A silicon substrate;
A diffusion layer formed on the silicon substrate;
An insulating film formed on the diffusion layer;
A surface silver electrode formed so as to be electrically connected to the diffusion layer by firing a conductive metal paste material that is dark after firing provided on the insulating film;
A back surface aluminum electrode formed on the back surface of the silicon substrate;
A back surface silver electrode formed on the back surface of the silicon substrate. A silicon substrate;
A diffusion layer formed on the silicon substrate;
An insulating film formed on the diffusion layer;
The conductive metal paste material provided on the insulating film and the conductive metal paste material that is dark after firing provided on the conductive metal paste are fired to be electrically connected to the diffusion layer. A surface silver electrode formed as follows:
A back surface aluminum electrode formed on the back surface of the silicon substrate;
A back surface silver electrode formed on the back surface of the silicon substrate. The solar cell according to claim 1, wherein the conductive metal paste material that is dark after firing has carbon. The solar cell according to claim 3, wherein the carbon is powder. The solar cell according to claim 4, wherein the conductive metal paste material that is dark after firing has a metal powder having a particle size larger than that of carbon powder. A silicon substrate;
A diffusion layer formed on the silicon substrate;
An insulating film formed on the diffusion layer;
A surface silver electrode formed on the insulating film so as to be electrically connected to the diffusion layer by firing a conductive metal paste material which is a silicon substrate color after firing;
A back surface aluminum electrode formed on the back surface of the silicon substrate;
A back surface silver electrode formed on the back surface of the silicon substrate. A method for manufacturing a solar cell, comprising forming a diffusion layer having a conductivity type inverted on a surface of a silicon substrate, and forming an antireflection film on the diffusion layer,
A step of screen-printing and drying a conductive metal paste material that is dark after firing on the antireflection film, and firing in a near-infrared furnace in a dry air atmosphere at 800 ° C. to 850 ° C. for several minutes to ten and several minutes. When,
A step of forming a surface silver electrode in which the conductive metal paste material, which is dark after firing, melts and penetrates the antireflection film during firing and is capable of making electrical contact with the diffusion layer. Battery manufacturing method. A method for manufacturing a solar cell, comprising forming a diffusion layer having a conductivity type inverted on a surface of a silicon substrate, and forming an antireflection film on the diffusion layer,
A step of screen-printing and drying a conductive metal paste on the antireflection film, and
On the conductive metal paste, a conductive metal paste material that is dark after firing is screen-printed and dried, and fired in a near-infrared furnace in a dry air atmosphere at 800 ° C. to 850 ° C. for several minutes to ten and several minutes. Process,
Forming a surface silver electrode capable of melting and penetrating the antireflection film during firing and making electrical contact with the diffusion layer during firing.

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