阅读说明：本技术 高效背面电极型太阳能电池及其制造方法 (High efficiency back electrode type solar cell and method for manufacturing the same ) 是由 桥上洋 渡部武纪 大塚宽之 于 2018-05-07 设计创作，主要内容包括：本发明提供一种背面电极型太阳能电池,其在结晶硅基板的第一主表面上具备具有p型导电类型的p型区域与具有n型导电类型的n型区域,并具备形成在p型区域上的正电极与形成在n型区域上的负电极,其特征在于,正电极由形成在p型区域上且含有III族元素的第一导电体、与层叠在第一导电体上且III族元素的含有比例低于第一导电体的第二导电体的层叠导电体构成,负电极由形成在n型区域上的第二导电体构成。由此,可提供一种光电转换效率高且廉价的背面电极型太阳能电池。(The present invention provides a back electrode type solar cell including a p-type region having a p-type conductivity and an n-type region having an n-type conductivity on a first main surface of a crystalline silicon substrate, and including a positive electrode formed on the p-type region and a negative electrode formed on the n-type region, wherein the positive electrode is composed of a laminated conductor of a first conductor formed on the p-type region and containing a group III element and a second conductor laminated on the first conductor and having a lower content ratio of the group III element than the first conductor, and the negative electrode is composed of a second conductor formed on the n-type region. Thus, a back electrode type solar cell having high photoelectric conversion efficiency and low cost can be provided.)

1. A solar cell of a back electrode type having a p-type region having a p-type conductivity and an n-type region having an n-type conductivity on a first main surface of a crystalline silicon substrate, and having a positive electrode formed on the p-type region and a negative electrode formed on the n-type region,

the positive electrode is composed of a laminated conductor of a first conductor formed on the p-type region and containing a group III element, and a second conductor laminated on the first conductor and having a lower group III element content than the first conductor,

the negative electrode is formed of the second conductor formed on the n-type region.

2. The solar cell according to claim 1, wherein the first conductor contains silver as a main component.

3. The solar cell according to claim 1, wherein the first conductor contains aluminum as a main component.

4. The solar cell according to any one of claims 1 to 3, further comprising a passivation film formed on a surface of the p-type region and the n-type region on which the positive electrode and the negative electrode are not formed.

5. A solar cell module comprising the solar cell according to any one of claims 1 to 4 electrically connected.

6. A solar cell power generation system characterized by being formed by electrically connecting a plurality of solar cell modules according to claim 5.

7. A method for manufacturing a solar cell, comprising:

forming a p-type region having a p-type conductivity and an n-type region having an n-type conductivity on a first main surface of a crystalline silicon substrate;

forming a first conductor containing a group III element on the p-type region; and

forming a second conductor having a lower group III element content than the first conductor on the first conductor and the n-type region,

the step of forming the first conductor and the step of forming the second conductor form a positive electrode formed of a laminated conductor of the first conductor and the second conductor and a negative electrode formed of the second conductor.

8. The method according to claim 7, wherein the step of forming the first conductor and the step of forming the second conductor include a step of screen printing or dispensing an electrode material.

9. The method of manufacturing a solar cell according to claim 7 or 8, further comprising a step of forming a passivation film on the surfaces of the p-type region and the n-type region before the step of forming the first conductor and the step of forming the second conductor,

in the step of forming the first conductor, the first electrode agent containing a group III element is applied to the p-type region via the passivation film,

in the step of forming the second conductor, a second electrode agent having a lower content of group III element than the first electrode agent is applied to the first electrode agent and the n-type region with the passivation film interposed therebetween,

after the step of forming the second conductor, the first electrode agent and the second electrode agent are sintered to form the positive electrode and the negative electrode.

Technical Field

The present invention relates to a high-efficiency back electrode type solar cell and a method for manufacturing the same.

Background

As a method for improving the photoelectric conversion efficiency of a crystalline silicon solar cell, a so-called back electrode type solar cell in which an electrode on a light receiving surface is eliminated to eliminate optical loss due to electrode shading has been widely studied in recent years.

Fig. 6 is a schematic view showing a basic structure of a general back electrode type solar cell. The light receiving surface is shown facing downward in the same drawing. As shown in fig. 6, in back electrode type solar cell 601, p-type region 603 in which a group III element such as boron or aluminum is diffused at a high concentration is formed on the non-light-receiving surface of substrate 602, and n-type region 604 in which a group V element such as phosphorus or antimony is diffused at a high concentration is formed adjacent to this.

In order to reduce loss due to recombination of photogenerated carriers, the p-type region 603 and the n-type region 604 are mainly covered with a passivation film 605 made of a single-layer film or a laminated film of silicon oxide, silicon nitride, aluminum oxide, silicon carbide, or the like, and the opposite surface (light receiving surface) is covered with an antireflection film 606 made of a single-layer film or a laminated film of silicon nitride, titanium oxide, tin oxide, zinc oxide, silicon oxide, aluminum oxide, or the like.

In addition, a positive electrode 607 and a negative electrode 608 are formed so as to penetrate the passivation film 605. From the aspect of cost, these electrodes are generally formed by: a conductive paste in which fine metal particles such as silver are mixed in an organic binder is applied to a predetermined position by screen printing or dispensing, and then heat-treated at about several hundred to 850 ℃.

However, in practice, if the above-described normal silver paste is applied to p-type silicon and n-type silicon, the contact resistance between the p-type silicon and the electrode is increased in many cases. This is because the work function difference from the metal in the conductive paste differs depending on the conductivity type of silicon.

In view of the above problem, for example, patent document 1 describes that a good electrical contact can be obtained by adding 6 to 30 wt% of aluminum powder as a solid component of a conductive paste containing silver as a main component.

Patent document 2 describes a method of obtaining an electrical contact by using a silver paste to which gallium or indium is added and introducing the impurity into p-type silicon by heat treatment.

Disclosure of Invention

Technical problem to be solved by the invention

However, since the additive composed of a group III element has low conductivity, when the additive is blended in an electrode material, there is a problem that wiring resistance increases. Further, the back electrode type solar cell in which both positive and negative electrodes are arranged on the non-light-receiving surface of the substrate has a higher photocurrent density than the conventional type solar cell having electrodes on both surfaces of the substrate, and therefore, there is a problem that the decrease in output characteristics due to the high wiring resistance becomes particularly significant.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a back electrode type solar cell which is easy to manufacture, has high photoelectric conversion efficiency, and is inexpensive. Another object of the present invention is to provide a solar cell module and a solar cell power generation system that have high photoelectric conversion efficiency and are inexpensive. Another object of the present invention is to provide a method for manufacturing a back electrode type solar cell having a low resistance loss and high photoelectric conversion efficiency by a simple method.

Means for solving the problems

In order to achieve the above object, the present invention provides a back electrode type solar cell including a p-type region having a p-type conductivity and an n-type region having an n-type conductivity on a first main surface of a crystalline silicon substrate, and including a positive electrode formed on the p-type region and a negative electrode formed on the n-type region, wherein the positive electrode is composed of a laminated conductor of a first conductor formed on the p-type region and containing a group III element and a second conductor laminated on the first conductor and having a lower content ratio of the group III element than the first conductor, and the negative electrode is composed of the second conductor formed on the n-type region.

In such a positive electrode for a solar cell, the first conductor in contact with the silicon substrate contains a group III element, and therefore, the contact resistance is low, and the second conductor connected to the wiring has a lower content of the group III element than the first conductor, and therefore, the wiring resistance is low. That is, the silicon substrate of the positive electrode has good electrical contact with the electrode, and further, wiring resistance is reduced. As a result, the solar cell of the present invention is a high-efficiency back electrode type solar cell with less resistance loss.

In this case, the first conductor may be made to contain silver as a main component. Alternatively, the first conductor may be formed of aluminum as a main component.

If silver is used as the main component of the first conductor, a silver paste can be used. In addition, if aluminum, which is relatively inexpensive, is used as a main component of the first conductor, the cost of the solar cell can be reduced.

Further, the solar cell of the present invention preferably includes a passivation film formed on the surfaces of the p-type region and the n-type region where the positive electrode and the negative electrode are not formed.

Such a solar cell can suppress recombination of electrons and holes on the surface of the silicon substrate by the passivation film, and thus can be a more efficient solar cell.

In order to achieve the above object, the present invention provides a solar cell module, which is formed by electrically connecting the solar cells.

Thus, the solar cell module in which the solar cells of the present invention are electrically connected has less resistance loss.

In order to achieve the above object, the present invention provides a solar cell power generation system including a plurality of solar cell modules electrically connected to each other.

A solar cell power generation system can be manufactured by connecting a plurality of solar cells of the present invention electrically connected to each other, and the solar cell power generation system has a small resistance loss.

In order to achieve the above object, the present invention provides a method for manufacturing a solar cell, comprising: forming a p-type region having a p-type conductivity and an n-type region having an n-type conductivity on a first main surface of a crystalline silicon substrate; forming a first conductor containing a group III element on the p-type region; and a step of forming a second conductor having a lower content ratio of the group III element than the first conductor on the first conductor and the n-type region, wherein a positive electrode composed of a laminated conductor of the first conductor and the second conductor and a negative electrode composed of the second conductor are formed by the step of forming the first conductor and the step of forming the second conductor.

Thus, a back electrode type solar cell having a small resistance loss of the electrode and high photoelectric conversion efficiency can be manufactured by a simple method. In particular, according to this method, a part of the positive electrode and the negative electrode can be formed at the same time without providing a new step, and an efficient solar cell can be manufactured at low cost.

In this case, the step of forming the first conductor and the step of forming the second conductor preferably include a step of screen printing or dispensing an electrode material.

By using such a method, a solar cell can be manufactured at low cost with good productivity.

Preferably, the method for manufacturing a solar cell of the present invention further includes a step of forming a passivation film on the surfaces of the p-type region and the n-type region before the step of forming the first conductor and the step of forming the second conductor, wherein the step of forming the first conductor includes applying the first electrode agent containing a group III element to the p-type region via the passivation film, the step of forming the second conductor includes applying a second electrode agent containing a group III element at a lower content ratio than the first electrode agent to the first electrode agent and the n-type region via the passivation film, and the step of forming the second conductor includes sintering the first electrode agent and the second electrode agent to form the positive electrode and the negative electrode.

Thus, a more efficient solar cell can be manufactured by forming the passivation film. In addition, the above method is a simple method.

Effects of the invention

In the solar cell of the present invention, since the positive electrode having both good electrical contact and low wiring resistance is provided, the resistance loss of the solar cell output can be reduced. Further, according to the method for manufacturing a solar cell of the present invention, a high-efficiency solar cell having reduced resistance loss can be manufactured inexpensively and easily. In particular, in the method for manufacturing a solar cell of the present invention, since a screen printing method or a dispensing method can be used and a part of the formation of the positive electrode and the formation of the negative electrode can be performed simultaneously, a solar cell having high photoelectric conversion efficiency can be manufactured at lower cost and with higher productivity.

Drawings

Fig. 1 is a diagram showing one embodiment of the structure of a solar cell of the present invention.

Fig. 2 is a diagram showing an example of the method for manufacturing a solar cell of the present invention.

Fig. 3 is a diagram showing one embodiment of the back surface structure of the solar cell of the present invention.

Fig. 4 is a diagram showing one embodiment of a solar cell module according to the present invention.

Fig. 5 is a diagram showing one embodiment of a solar power generation system of the present invention.

Fig. 6 is a diagram showing a basic structure of a conventional back electrode type solar cell.

Detailed Description

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto.

First, an example of the structure of the solar cell of the present invention will be specifically described with reference to fig. 1. The light receiving surface is shown facing downward in fig. 1.

As shown in fig. 1, a back electrode type solar cell 101 (hereinafter, may be simply referred to as a solar cell) of the present invention includes a p-type region 103 having a p-type conductivity and an n-type region 104 having an n-type conductivity on a first main surface (a surface which becomes a non-light-receiving surface when the solar cell is manufactured) of a crystalline silicon substrate 102, and includes a positive electrode 107 formed on the p-type region 103 and a negative electrode 108 formed on the n-type region 104.

More specifically, the following back electrode type solar cell can be produced. In the back electrode type solar cell 101 of the present invention, a p-type region 103 having a p-type conductivity is locally formed on a first main surface (a surface which is a non-light-receiving surface when the solar cell is manufactured) of a crystalline silicon substrate 102 having a p-type or n-type conductivity, and a dopant imparting a p-type conductivity is added to the p-type region 103 at a higher concentration than that of the dopant of the crystalline silicon substrate 102. Further, an n-type region 104 having an n-type conductivity may be formed adjacent to the p-type region 103 on the same first main surface, the n-type region 104 being added with a dopant imparting the n-type conductivity at a concentration higher than that of the silicon substrate 102.

A positive electrode 107 formed of a laminated conductor 111 of a first conductor 109 and a second conductor 110 is formed on the p-type region 103. On the other hand, a negative electrode 108 made of a second conductor 110 is formed on the n-type region 104. The first conductor 109 constituting a part of the positive electrode 107 formed on the p-type region 103 contains a group III element.

For the purpose of reducing the contact resistance with p-type region 103, a sintered body of an aluminum paste to which a glass frit is added or a sintered body of a silver paste to which a group III element and a glass frit are added is suitably used for first conductor 109. The group III element may be a monomer or a compound of boron, gallium or indium, and preferably aluminum is used from the viewpoint of cost. More specifically, the compound of a group III element preferably contains one or more of boron nitride, boron oxide, aluminum chloride, and aluminum bromide. The content of the group III element in the first conductor 109 needs to be appropriately adjusted depending on the element to be added or the form thereof, and for example, when aluminum is used, the content may be approximately 3% by weight or more. Further, the first conductor preferably contains silver or aluminum as a main component. When silver is used as the main component, the content of silver is preferably 50 mass% or more. When aluminum is used as the main component, the content of aluminum is preferably 50 mass% or more.

The second conductor 110 contains a group III element at a lower ratio than the first conductor 109. In particular, the second conductor 110 is preferably formed of a sintered body of a normal silver paste to which a glass frit is added and to which no group III element is added. When a group III element is added to the second conductor 110 serving as the negative electrode 108, not only wiring resistance increases, but also energy barrier is formed on the surface of the n-type region 104, so that contact resistance increases, and solar cell characteristics deteriorate.

Thus, by forming the positive electrode 107 to have a laminated structure of the first conductor 109 and the second conductor 110 having low wiring resistance, which can provide good electrical contact with the p-type region 103, it is possible to reduce resistance loss and improve the photoelectric conversion efficiency of the solar cell.

Further, it is preferable that a passivation film 105 is formed on a portion of the p-type region 103 where no positive electrode is formed and a portion of the n-type region 104 where no negative electrode is formed. In this case, back electrode type solar cell 101 of the present invention includes passivation film 105 formed on the surfaces of p-type region 103 and n-type region 104 where positive electrode 107 and negative electrode 108 are not formed. Such a passivation film 105 can suppress recombination of holes and electrons on the surface of the crystalline silicon substrate 102, and thus can provide a more efficient solar cell. The passivation film 105 may be formed using silicon oxide, silicon nitride, aluminum oxide, silicon carbide, or the like. It may be used as a single layer or may be combined to form a laminated film. The thickness of the passivation film 105 may be set to several nm to 100nm in order to obtain a sufficient passivation effect. In addition, films having different structures may be applied to the surface of p-type region 103 and the surface of n-type region 104.

Further, an antireflection film 106 is preferably formed on the light-receiving surface of the crystalline silicon substrate 102. Since the antireflection film 106 is required to obtain a light confinement effect, a dielectric having a refractive index of 1.8 to 2.2 may be used, and for this purpose, silicon nitride, silicon carbide, titanium oxide, tin oxide, zinc oxide, or the like may be used. These dielectrics can be used with a film thickness of 70nm to 120nm in order to obtain the most appropriate light confinement effect. Further, it may be used as a single layer, and although not shown, an intermediate layer of silicon oxide or aluminum oxide having a film thickness of 40nm or less may be formed between the dielectric and the crystalline silicon substrate 102. Thus, the passivation effect of the surface of the light receiving surface can be improved.

Next, a method for manufacturing a solar cell according to the present invention will be described with reference to fig. 2, but the present invention is not limited thereto.

The crystalline silicon substrate 202 may be crystalline silicon having p-type or n-type conductivity with a resistivity of 0.1 to 10 Ω · cm, and an uneven structure for light confinement may be formed on the substrate surface, although not shown. The textured structure is obtained by immersing the crystalline silicon substrate 202 in an acidic or alkaline solution for a certain period of time. The acid solution is usually a mixed acid solution obtained by mixing acetic acid, phosphoric acid, sulfuric acid, water, and the like in a mixed solution of hydrofluoric acid and nitric acid, and when the crystalline silicon substrate 202 is immersed in the acid solution, fine grooves and the like are preferentially etched on a rough surface during processing of the substrate, thereby forming an uneven structure. Further, potassium hydroxide or sodium hydroxide solution, or tetramethylammonium hydroxide solution may be used as the alkali solution. Since the alkali etching proceeds by forming Si — OH bonds, the etching rate depends on the crystal plane orientation, and thus a concave-convex structure in which a crystal plane having a low etching rate is exposed is obtained.

The uneven structure is not necessarily required on the non-light-receiving surface of the crystalline silicon substrate 202. Instead, the surface area is reduced by flattening, and an effect of reducing the carrier recombination loss can be expected. In this case, a spin etching machine or an in-line single-side cleaning machine using a chemical solution containing a mixed solution of hydrofluoric acid and nitric acid can be used.

After the uneven structure is formed, the crystalline silicon substrate 202 is preferably cleaned in an acidic solution of hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, or the like, or a mixed solution of these acids. From the viewpoint of cost and characteristics, it is preferable to wash the resin in hydrochloric acid. In order to improve the cleanliness, 0.5 to 5% hydrogen peroxide is mixed with a hydrochloric acid solution, and the mixture is washed by heating to 60 to 90 ℃.

Next, a p-type region having a p-type conductivity type and an n-type region having an n-type conductivity type are formed on the first main surface of the crystalline silicon substrate. As described below, it can be formed by the steps shown in fig. 2(a) to (c), but is not limited thereto. First, as shown in fig. 2(a), a p-type region 203 is formed on one surface of a crystalline silicon substrate 202. The p-type region 203 can be formed by using a diffusion source containing a group III element, and for example, boron bromide can be used to perform vapor phase diffusion at 900 to 1000 ℃. In order to achieve the above-described requirement, it is necessary to form the p-type region 203 only on the back surface (surface which is not a light-receiving surface when the solar cell is manufactured), and in order to prevent boron from diffusing into the light-receiving surface, diffusion is performed in a state where two substrates are stacked on each other or a diffusion barrier layer such as silicon nitride is formed on the light-receiving surface side. In addition to the vapor phase diffusion, the p-type region 203 may be formed by coating a boron compound on a substrate, drying the boron compound, and then thermally diffusing the boron compound at 900 to 1000 ℃. According to this method, the diffusion of boron to the non-coated surface can be suppressed relatively easily. In addition, the single-side diffusion can be performed by a spin coating method, a spraying method, or the like using a diffusing agent.

In addition, a diffusion barrier layer 212 may be formed on the p-type region 203. Among them, silicon nitride or silicon oxide obtained by a chemical vapor deposition method or a physical vapor deposition method is preferably used. In this case, the thickness of the film is approximately 50 to 200nm, although the thickness varies depending on the method of manufacturing the film. In addition, a silicon oxide film obtained by heat treatment may be used. At this time, the substrate is heat-treated in an oxygen or water vapor atmosphere at 800 to 1100 ℃ to grow silicon oxide of 20 to 200 nm. The thermal oxidation may be performed continuously with the diffusion of a group III element such as boron.

Next, as shown in fig. 2(b), the diffusion barrier layer 212 at the position where the n-type region is formed is partially removed to expose the p-type region 203. Removal of the diffusion barrier 212 may be accomplished by: for example, the etching paste is screen-printed at a desired position and heat-treated at 100 to 400 ℃. In addition, laser ablation with a simpler process can also be performed.

Next, as shown in fig. 2(c), an n-type region 204 may be formed in the opening of the diffusion barrier layer. The n-type region 204 can be formed by using a diffusion source containing a group V element, and for example, phosphorus oxychloride can be used to perform gas phase diffusion at 800 to 980 ℃ in view of electrical characteristics and device simplicity. In order to achieve the above-described requirement, the solar cell of the present invention needs to form the n-type region 204 only on the back surface (non-light-receiving surface), and diffusion is performed in a state where two substrates are stacked on each other or a diffusion barrier layer such as silicon nitride is formed on the light-receiving surface side so that phosphorus does not diffuse into the light-receiving surface. In addition to the vapor phase diffusion, the n-type region 204 may be formed by coating a phosphorus compound on a substrate, drying the coating, and then thermally diffusing the coating at 800 to 980 ℃. According to this method, diffusion of phosphorus to the non-coated surface can be suppressed relatively easily.

In addition to the above method, the diffusion of the group V element such as phosphorus may be performed after the p-type region 203 exposed in the opening of the diffusion barrier layer 212 is etched and removed. In this case, for example, the crystalline silicon substrate 202 is immersed in a sodium hydroxide solution or a potassium hydroxide solution, and the diffusion barrier layer 212 functions as a mask to selectively remove the p-type region 203 in the opening.

The p-type region and the n-type region may be patterned so that, for example, as shown in fig. 3(a), the p-type region 303 and the n-type region 304 are linearly adjacent to each other in the crystalline silicon substrate 302, or as shown in fig. 3(b) and 3(c), one of the p-type region 303 and the n-type region 304 may be formed in an island shape.

After the diffusion of the group V element such as phosphorus, the boron glass, the diffusion barrier layer 212, and the phosphorus glass formed on the diffusion surface are removed using hydrofluoric acid or the like. In order to maintain the cleanness of the substrate surface, it is more preferable to mix ammonia water or a tetramethylammonium hydroxide solution with 0.5 to 5% hydrogen peroxide, and then heat the mixture to 60 to 90 ℃ for cleaning. In addition, hydrochloric acid, sulfuric acid, nitric acid, or a mixture of these acids, or these acids and 0.5 to 5% hydrogen peroxide may be mixed, and the mixture may be heated to 60 to 90 ℃ for cleaning. In addition, it is preferable that the oxide film on the substrate surface is removed by a hydrofluoric acid solution in the final stage.

Next, as shown in fig. 2(d), a passivation film 205 may be formed on the p-type region and the n-type region. Silicon nitride may be suitably used in the passivation film 205. In this case, a film having a high passivation effect can be obtained by appropriately adjusting the mixing ratio of silane, ammonia gas, and hydrogen gas by plasma CVD. Alternatively, silicon oxide, aluminum oxide, silicon carbide, or the like may be formed by a method such as heat treatment, a CVD method, a sputtering method, or an atomic layer deposition method. Further, these films may be formed of a single layer, or may be formed by combining and laminating any of the above. In addition, in order to obtain a sufficient passivation effect, the film thickness of the passivation film 205 may be formed to be several nm to 100 nm.

Next, the antireflection film 206 is formed on the light-receiving surface of the crystalline silicon substrate 202, and since the antireflection film 206 is required to obtain a light confinement effect, a dielectric having a refractive index of 1.8 to 2.2 can be used, and for this purpose, silicon nitride, silicon carbide, titanium oxide, tin oxide, zinc oxide, or the like can be used. These films can be used so that the film thickness is 70nm to 120nm in order to obtain an optimum light confinement effect. These films may be used as a single layer, and although not shown, an intermediate layer of silicon oxide or aluminum oxide having a thickness of 40nm or less may be formed between the film and the crystalline silicon substrate 202. This can improve the passivation effect on the surface of the light-receiving surface.

Next, as shown in fig. 2(e), the first electrode agent 209a is applied to the p-type region 2, and in order to obtain good electrical contact with the p-type region 203, an aluminum paste in which aluminum powder and glass frit are mixed in an organic binder, or a silver paste in which silver powder, glass frit, and a monomer or compound of a group III element are mixed in an organic binder is suitably used as the first electrode agent 209 a. In the latter case, the content of the group III element needs to be appropriately adjusted depending on the element to be added and the form thereof, and it is preferable to use a silver paste containing 3% by weight or more of aluminum powder in terms of solid content from the viewpoint of cost.

The method for forming the first electrode agent 209a is not particularly limited, and it is preferable to screen-print or form-dispense a conductive paste on the p-type region 203 from the viewpoint of productivity.

Then, the crystalline silicon substrate 202 is dried in an atmosphere at 100 to 300 ℃.

Next, as shown in fig. 2(f), a second electrode agent 210a is formed on the first electrode agent 209a and the n-type region 204 by coating. The second electrode agent 210a is suitably a silver paste containing no group III element and having silver powder and glass frit mixed in an organic binder.

Then, the substrate is dried in an atmosphere at 100 to 300 ℃.

Next, the substrate is fired, for example, in an atmosphere at about 700 to 890 ℃ for 1 second to 10 minutes. When the first electrode agent 209a and the second electrode agent 210b are sintered by this heat treatment, as shown in fig. 2(g), the positive electrode 207 and the negative electrode 208 are formed, and further, the passivation film 205 is eroded by the electrode agents, and both electrodes are in electrical contact with the crystalline silicon substrate 202. In this way, the back electrode type solar cell 201 of the present invention can be manufactured.

In addition, a plurality of solar cells of the present invention obtained by the above steps are connected in series, whereby a solar cell module can be obtained. Fig. 4 shows an example of the structure of the solar cell module 420 of the present invention on the non-light-receiving surface side. The positive electrode 407 of the solar cell 401 is electrically connected to the negative electrode 408 of the adjacent solar cell via a tab 421, and the number of solar cells required for a predetermined output power is connected thereto. The positive electrode 407 of one solar cell is connected to the positive terminal 422 of the solar cell module 420, and the negative electrode 408 of the other solar cell is connected to the negative terminal 423 of the solar cell module 420. Although not shown in fig. 4, the connected solar cells may be sealed by a glass cover sheet and filler, and a back sheet (backsheet). Soda lime glass is widely used for glass cover sheets. Further, ethylene vinyl acetate, polyolefin, silicone, or the like can be used as the filler. The backsheet may generally utilize a functional film using polyethylene terephthalate.

Fig. 5 shows a basic configuration of a solar cell power generation system in which a plurality of solar cell modules are electrically connected. In the solar cell power generation system 530, the plurality of solar cell modules 520 are connected in series by the wiring 531, and the generated power is supplied to the external load circuit 533 via the inverter 532. Although not shown in fig. 5, the system may further include a secondary battery that stores the generated electric power.