JP2013026472A - N-type diffusion layer formation composition, manufacturing method of n-type diffusion layer, and manufacturing method of solar cell element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an n-type diffusion layer formation composition, a manufacturing method of an n-type diffusion layer, and a manufacturing method of a solar cell element capable of forming an n-type diffusion layer in a specific part without forming the n-type diffusion layer in an unnecessary region in a manufacturing step of a solar cell element using a silicon element and obtaining a sufficient ohmic contact by a simplified step.SOLUTION: An n-type diffusion layer formation composition contains a glass powder including a donor element and a dispersion medium. An n-type diffusion layer and a solar cell element having this n-type diffusion layer are manufactured by coating this n-type diffusion layer formation composition on a semiconductor substrate and performing thermal diffusion treatment.

Description

  The present invention relates to an n-type diffusion layer forming composition for a solar cell element, a method for producing an n-type diffusion layer, and a method for producing a solar cell element, and more specifically, a specific portion of a silicon substrate that is a semiconductor substrate. The present invention relates to a technique that makes it possible to form an n-type diffusion layer.

The manufacturing process of the conventional silicon solar cell element is demonstrated.
First, a p-type silicon substrate having a textured structure formed on the light receiving surface is prepared so as to promote the light confinement effect, and then a donor element-containing compound such as phosphorus oxychloride (POCl ₃ ), nitrogen, oxygen In this mixed gas atmosphere, several tens of minutes are performed at 800 ° C. to 900 ° C. to uniformly form the n-type diffusion layer on the substrate. In this conventional method, since phosphorus is diffused using a mixed gas, n-type diffusion layers are formed not only on the surface but also on the side surface and the back surface. Therefore, a side etching process for removing the side n-type diffusion layer is necessary. Further, the n-type diffusion layer on the back surface needs to be converted into a p ⁺ -type diffusion layer. An aluminum paste is applied on the n-type diffusion layer on the back surface, and this is baked, and the n-type diffusion layer is diffused by aluminum diffusion. To a p ⁺ type diffusion layer.

On the other hand, in the semiconductor manufacturing field, by applying a solution containing a phosphate such as phosphorus pentoxide (P ₂ O ₅ ) or ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ) as a donor element-containing compound. A method for forming an n-type diffusion layer has been proposed (see, for example, Patent Document 1). However, in this method, since the donor element or a compound containing the same is scattered from the solution that is the diffusion source, the diffusion of phosphorus extends to the side surface and the back surface when the diffusion layer is formed, as in the gas phase reaction method using the mixed gas. An n-type diffusion layer is formed not only on the surface but also on the coated part.

JP 2002-75894 A

  As described above, in forming a n-type diffusion layer, in the gas phase reaction using phosphorus oxychloride, not only one side (usually the light receiving surface or the surface) that originally requires the n-type diffusion layer but also the other side An n-type diffusion layer is also formed on the surface (non-light-receiving surface or back surface) and side surfaces. Further, even in the method of applying a solution containing phosphate and thermally diffusing, an n-type diffusion layer is formed on the surface other than the surface as in the gas phase reaction method. Therefore, in order to have a pn junction structure as an element, it is necessary to perform etching on the side surface and convert the n-type diffusion layer to the p-type diffusion layer on the back surface. In general, an aluminum paste which is a Group 13 element is applied to the back surface and fired to convert the n-type diffusion layer into a p-type diffusion layer.

  In addition, a glass layer is formed on the n-type diffusion layer also in a conventional gas phase reaction method or a method of applying a phosphate-containing solution. When an electrode is formed on the n-type diffusion layer via the glass layer, the ohmic contact between the electrode and the n-type diffusion layer is hindered by the electrical resistance of the glass layer, so a step of removing the generated glass layer by etching is necessary. It has become.

  The present invention has been made in view of the above-described conventional problems, and in a manufacturing process of a solar cell element using a silicon substrate, an n-type diffusion layer is not formed in a specific portion without forming an n-type diffusion layer in an unnecessary region. PROBLEM TO BE SOLVED: To provide an n-type diffusion layer forming composition capable of forming a diffusion layer and obtaining sufficient ohmic contact even if the process is simplified, a method for producing an n-type diffusion layer, and a method for producing a solar cell element And

Means for solving the problems are as follows.
<1> An n-type diffusion layer forming composition containing a glass powder containing a donor element and silver oxide, and a dispersion medium.
<2> The n-type diffusion layer forming composition according to <1>, wherein the donor element is at least one selected from P (phosphorus) and Sb (antimony).
<3> The glass powder containing the donor element and silver oxide is at least one donor element-containing material selected from P ₂ O ₃ , P ₂ O ₅ and Sb ₂ O ₃ , AgO, SiO ₂ , K _At least one glass component selected from ₂ O, Na ₂ O, Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, V ₂ O ₅ , SnO, ZrO ₂ , and MoO ₃ The composition for forming an n-type diffusion layer according to <1> or <2>, containing a substance.

<4> An n-type diffusion comprising a step of applying the n-type diffusion layer forming composition according to any one of <1> to <3> on a semiconductor substrate and a step of performing a thermal diffusion treatment. Layer manufacturing method.
<5> A step of applying the n-type diffusion layer forming composition according to any one of <1> to <3> on the semiconductor substrate and a thermal diffusion treatment to form an n-type diffusion layer. The manufacturing method of the solar cell element which has a process and the process of forming an electrode on the formed n type diffused layer.
<6> The glass layer formed on the n-type diffusion layer is not removed between the step of forming the n-type diffusion layer and the step of forming the electrode, or a part of the glass layer is removed. The method for producing a solar cell element according to <5>, wherein the solar cell element is removed.

  According to the present invention, in a manufacturing process of a solar cell element using a silicon substrate, it is possible to form an n-type diffusion layer in a specific portion without forming an n-type diffusion layer in an unnecessary region. Even if this is simplified, sufficient ohmic contact can be obtained.

It is sectional drawing which shows notionally an example of the manufacturing process of the solar cell element of this invention. (A) is the top view which looked at the solar cell element from the surface, (B) is the perspective view which expands and shows a part of (A).

First, the n-type diffusion layer forming composition of the present invention will be described, and then the n-type diffusion layer and solar cell element manufacturing method using the n-type diffusion layer forming composition will be described.
In this specification, the term “process” is not limited to an independent process, and even if it cannot be clearly distinguished from other processes, the term “process” is used if the intended action of the process is achieved. included. In the present specification, “to” indicates a range including the numerical values described before and after the values as a minimum value and a maximum value, respectively.

The n-type diffusion layer forming composition of the present invention contains a glass powder containing at least a donor element and silver oxide (hereinafter sometimes simply referred to as “glass powder”) and a dispersion medium, and further has coating properties and the like. In consideration of the above, other additives may be contained as necessary.
Here, the n-type diffusion layer forming composition contains a glass powder containing a donor element and silver oxide, and after applying to a silicon substrate, the n-type diffusion layer is formed by thermally diffusing this donor element. A possible material. By using the n-type diffusion layer forming composition of the present invention, an n-type diffusion layer is formed at a desired site, and an unnecessary n-type diffusion layer is not formed on the back surface or side surface.

Therefore, if the composition for forming an n-type diffusion layer of the present invention is applied, the side etching step that is essential in the gas phase reaction method that has been widely employed is not required, and the process is simplified. In addition, the step of converting the n-type diffusion layer formed on the back surface into the p ⁺ -type diffusion layer is not necessary. Therefore, the method for forming the p ⁺ -type diffusion layer on the back surface and the material, shape, and thickness of the back electrode are not limited, and the choice of manufacturing method, material, and shape to be applied is widened. Although details will be described later, generation of internal stress in the silicon substrate due to the thickness of the back electrode is suppressed, and warpage of the silicon substrate is also suppressed.

  In addition, since the donor component in the glass powder is difficult to volatilize even during firing, it is suppressed that the n-type diffusion layer is formed not only on the surface but also on the back surface and side surfaces due to the generation of the volatilizing gas. The reason for this is considered that the donor component is bonded to an element in the glass powder or is taken into the glass, so that it is difficult to volatilize.

  Thus, since the n-type diffusion layer forming composition of the present invention can form an n-type diffusion layer having a desired concentration at a desired site, a selective region having a high n-type dopant concentration is formed. It becomes possible to form. On the other hand, it is generally difficult to form a selective region having a high n-type dopant concentration by a gas phase reaction method, which is a general method of an n-type diffusion layer, or a method using a phosphate-containing solution. .

  In addition, the glass powder contained in the n type diffused layer formation composition of this invention fuse | melts by baking, and forms a glass layer on an n type diffused layer. In a conventional gas phase reaction method or a method of applying a phosphate-containing solution, a glass layer is formed on the n-type diffusion layer. Therefore, the generated glass layer is removed by etching, and then on the n-type diffusion layer. An electrode is formed on the substrate.

  Here, in the present invention, glass powder containing silver oxide is used. This silver oxide is deposited as silver particles in a glass layer formed on the n-type diffusion layer through a thermal diffusion treatment step. When the silver particles are distributed in the glass layer, the conductivity of the glass layer itself can be increased. As a result, a good ohmic contact can be formed between the electrode and the silicon substrate without removing the glass layer by an etching step before forming the electrode on the n-type diffusion layer. Therefore, according to the present invention, even when the glass layer etching step is omitted, the ohmic contact between the electrode and the n-type diffusion layer is sufficient.

Next, the glass powder containing the donor element and silver oxide according to the present invention will be described in detail.
A donor element is an element that can form an n-type diffusion layer by doping into a silicon substrate. As the donor element, a Group 15 element can be used, and examples thereof include P (phosphorus), Sb (antimony), Bi (bismuth), As (arsenic), and the like. From the viewpoints of safety, ease of vitrification, etc., P or Sb is preferred.

  The glass powder can control the melting temperature, softening temperature, glass transition temperature, chemical durability, and the like by adjusting the component ratio as necessary.

Examples of the donor element-containing material used for introducing the donor element into the glass powder include P ₂ O ₃ , P ₂ O ₅ , Sb ₂ O ₃ , Bi ₂ O ₃ and As ₂ O ₃ , and P ₂ O ₃ It is preferable to use at least one selected from P ₂ O ₅ and Sb ₂ O ₃ .

  The content ratio of the donor element-containing substance in the glass powder is preferably set appropriately in consideration of the melting temperature, the softening temperature, the doping behavior of the donor element, and chemical durability, and is generally 1% by mass or more and 90% by mass. The content is preferably 3% by mass or more and more preferably 80% by mass or less.

The content ratio of silver oxide in the glass powder is preferably set in consideration of the precipitation amount of silver particles, the melting temperature, the softening temperature, and the chemical durability, and is generally 1% by mass to 75% by mass. It is preferably 3% by mass or more and 70% by mass or less.
Further, in the glass powder, the content of silver oxide with respect to the donor element-containing substance is preferably set appropriately in consideration of the precipitation amount of silver particles, the melting temperature, the softening temperature, and the chemical durability. % To 200% by mass, and more preferably 5% to 150% by mass.

Moreover, it is preferable that glass powder contains the glass component substance further described below.
Examples of glass component materials include SiO ₂ , K ₂ O, Na ₂ O, Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, V ₂ O ₅ , SnO, ZrO ₂ , WO ₃ , Examples include MoO ₃ , MnO, La ₂ O ₃ , Nb ₂ O ₅ , Ta ₂ O ₅ , Y ₂ O ₃ , TiO ₂ , ZrO ₂ , GeO ₂ , TeO _2, and Lu ₂ O _3. SiO ₂ , K _Use at least one selected from ₂ O, Na ₂ O, Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, V ₂ O ₅ , SnO, ZrO ₂ , and MoO _3. Is preferred.

Specific examples of the glass powder containing a donor element and silver oxide include a system containing the donor element-containing substance, silver oxide, and the glass component substance, and a P ₂ O ₅ —AgO—SiO ₂ system (containing a donor element) substances - silver oxide - described in the order of the glass component material, hereinafter the _{same), P 2 O 5 -AgO-} K 2 O _{-based, P 2 O 5 -AgO-Na} 2 O _{-based, P 2 O 5 -AgO-Li} 2 _O-based, P ₂ O 5 -AgO-BaO _based, P ₂ O 5 _{-AgO-SrO-based,} P ₂ O 5 _{-AgO-CaO-based,} P ₂ O 5 _{-AgO-MgO-based,} P ₂ O 5 -AgO- BeO system, P ₂ O ₅ —AgO—ZnO system, P ₂ O ₅ —AgO—CdO system, P ₂ O ₅ —AgO—PbO system, P ₂ O ₅ —AgO—V ₂ O ₅ system, P ₂ O ₅ -AgO-SnO _{system, P 2 O 5 -AgO-GeO} 2 _{, P 2 O 5 -AgO-TeO} 2 system like system containing _P 2 _{O 5} as a donor element-containing material, Sb ₂ as a donor element-containing material instead of _P 2 _{O 5} of system containing _P 2 _{O 5} of the Examples thereof include glass powders containing O ₃ .

Note that glass powder containing two or more kinds of donor element-containing substances may be used, such as P ₂ O ₅ —AgO—Sb ₂ O ₃ system and P ₂ O ₅ —AgO—As ₂ O ₃ system. Further, _P 2 _O 5 -AgO system containing no glass component material _may be a glass powder Sb ₂ O 3 -AgO system or the like.
Although the composite glass containing three components was illustrated above, four or more kinds of components such as P ₂ O ₅ —AgO—SiO ₂ —V ₂ O ₅ , P ₂ O ₅ —AgO—SiO ₂ —CaO, and the like are necessary. Glass powder containing

  The content ratio of the glass component substance in the glass powder is preferably set in consideration of the melting temperature, the softening temperature, the glass transition temperature, and the chemical durability, and is generally 0.1% by mass to 95% by mass. Or less, more preferably 0.5% by mass or more and 90% by mass or less.

Specifically, for example, in the case of P ₂ O ₅ —AgO—ZnO-based glass powder, the content ratio of ZnO is preferably 1% by mass to 50% by mass, and preferably 3% by mass to 40% by mass. % Or less is more preferable.

  The softening temperature of the glass powder is preferably 200 ° C. to 1000 ° C., more preferably 300 ° C. to 900 ° C., from the viewpoints of diffusibility during the diffusion treatment and dripping.

Examples of the shape of the glass powder include a substantially spherical shape, a flat shape, a block shape, a plate shape, a scale shape, and the like. From the viewpoint of the application property to the substrate and the uniform diffusibility when it is an n-type diffusion layer forming composition, It is desirable to have a substantially spherical shape, a flat shape, or a plate shape.
The particle size of the glass powder is desirably 100 μm or less. When glass powder having a particle size of 100 μm or less is used, a smooth coating film is easily obtained. Furthermore, the particle size of the glass powder is more desirably 50 μm or less. The lower limit is not particularly limited, but is preferably 0.01 μm or more.
Here, the particle diameter of glass represents an average particle diameter, and can be measured by a laser scattering diffraction particle size distribution measuring apparatus or the like.

A glass powder containing a donor element and silver oxide is produced by the following procedure.
First, raw materials, for example, the donor element-containing material, silver oxide, and the glass component material are weighed and filled in a crucible. Examples of the material for the crucible include platinum, platinum-rhodium, gold, iridium, alumina, quartz, carbon, and the like, which are appropriately selected in consideration of the melting temperature, atmosphere, reactivity with the molten material, and the like.
Next, it heats with the temperature according to a glass composition with an electric furnace, and is set as a melt. At this time, it is desirable to stir the melt uniformly.
Subsequently, the obtained melt is poured onto a zirconia substrate, a carbon substrate or the like to vitrify the melt.
Finally, the glass is crushed into powder. A known method such as a jet mill, a bead mill, or a ball mill can be applied to the pulverization.

  The content ratio of the glass powder containing the donor element and silver oxide in the n-type diffusion layer forming composition is determined in consideration of the coating property, the diffusibility of the donor element, and the like. Generally, the content ratio of the glass powder in the n-type diffusion layer forming composition is preferably 0.1% by mass or more and 95% by mass or less, and more preferably 1% by mass or more and 90% by mass or less.

Next, the dispersion medium will be described.
The dispersion medium is a medium in which the glass powder is dispersed in the composition. Specifically, a binder, a solvent, or the like is employed as the dispersion medium.

  Examples of the binder include polyvinyl alcohol, polyacrylamides, polyvinyl amides, polyvinyl pyrrolidone, polyethylene oxides, polysulfonic acid, acrylamide alkyl sulfonic acid, cellulose ethers, cellulose derivatives, carboxymethyl cellulose, hydroxyethyl cellulose, ethyl cellulose, gelatin, starch And starch derivatives, sodium alginates, xanthan, gua and gua derivatives, scleroglucan and scleroglucan derivatives, tragacanth and tragacanth derivatives, dextrin and dextrin derivatives, (meth) acrylic acid resins, (meth) acrylic acid ester resins (e.g. , Alkyl (meth) acrylate resins, dimethylaminoethyl (meth) acrylate resins, etc.), butadiene resin , Styrene resin, or copolymers thereof, Additional be appropriately selected siloxane resin. These are used singly or in combination of two or more.

  The molecular weight of the binder is not particularly limited, and it is desirable to adjust appropriately in view of the desired viscosity of the composition.

  Examples of the solvent include acetone, methyl ethyl ketone, methyl-n-propyl ketone, methyl-iso-propyl ketone, methyl-n-butyl ketone, methyl-iso-butyl ketone, methyl-n-pentyl ketone, methyl-n-hexyl ketone, Ketone solvents such as diethyl ketone, dipropyl ketone, di-iso-butyl ketone, trimethylnonanone, cyclohexanone, cyclopentanone, methylcyclohexanone, 2,4-pentanedione, acetonylacetone; diethyl ether, methyl ethyl ether, methyl -N-propyl ether, di-iso-propyl ether, tetrahydrofuran, methyltetrahydrofuran, dioxane, dimethyldioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether Ter, ethylene glycol di-n-propyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol methyl n-propyl ether, diethylene glycol methyl n-butyl ether, diethylene glycol di-n-propyl ether , Diethylene glycol di-n-butyl ether, diethylene glycol methyl-n-hexyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol methyl ethyl ether, triethylene glycol methyl n-butyl ether, triethylene glycol di-n- Butyl ether, G Ethylene glycol methyl-n-hexyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetradiethylene glycol methyl ethyl ether, tetraethylene glycol methyl n-butyl ether, diethylene glycol di-n-butyl ether, tetraethylene glycol methyl n-hexyl Ether, tetraethylene glycol di-n-butyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol di-n-propyl ether, propylene glycol dibutyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, dipropylene glycol methyl ethyl Ether, zip Lopylene glycol methyl-n-butyl ether, dipropylene glycol di-n-propyl ether, dipropylene glycol di-n-butyl ether, dipropylene glycol methyl-n-hexyl ether, tripropylene glycol dimethyl ether, tripropylene glycol diethyl ether, tripropylene Glycol methyl ethyl ether, tripropylene glycol methyl-n-butyl ether, tripropylene glycol di-n-butyl ether, tripropylene glycol methyl-n-hexyl ether, tetrapropylene glycol dimethyl ether, tetrapropylene glycol diethyl ether, tetradipropylene glycol methyl ethyl Ether, tetrapropylene glycol methyl-n-butyl ether Ether solvents such as dipropylene glycol di-n-butyl ether, tetrapropylene glycol methyl-n-hexyl ether, tetrapropylene glycol di-n-butyl ether; methyl acetate, ethyl acetate, n-propyl acetate, i-propyl acetate, acetic acid n-butyl, i-butyl acetate, sec-butyl acetate, n-pentyl acetate, sec-pentyl acetate, 3-methoxybutyl acetate, methylpentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, 2- (2- Butoxyethoxy) ethyl, benzyl acetate, cyclohexyl acetate, methyl cyclohexyl acetate, nonyl acetate, methyl acetoacetate, ethyl acetoacetate, diethylene glycol methyl ether acetate, diethylene glycol monoethyl ether acetate, dipropylene glycol acetate Methyl ether, dipropylene glycol ethyl ether, glycol diacetate, methoxytriglycol acetate, ethyl propionate, n-butyl propionate, i-amyl propionate, diethyl oxalate, di-n-butyl oxalate, lactic acid Methyl, ethyl lactate, n-butyl lactate, n-amyl lactate, ethylene glycol methyl ether propionate, ethylene glycol ethyl ether propionate, ethylene glycol methyl ether acetate, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, propylene Ester solvents such as glycol ethyl ether acetate, propylene glycol propyl ether acetate, γ-butyrolactone, γ-valerolactone; N-methylpyrrolidinone, N-ethylpyrrolidinone, N-propylpyrrolidinone, N-butylpyrrolidinone, N-hexylpyrrolidinone, N-cyclohexylpyrrolidinone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide, etc. Aprotic polar solvent: methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, sec-butanol, t-butanol, n-pentanol, i-pentanol, 2-methylbutanol, sec -Pentanol, t-pentanol, 3-methoxybutanol, n-hexanol, 2-methylpentanol, sec-hexanol, 2-ethylbutanol, sec-heptanol, n-octanol, 2-ethylhexanol, sec-octanol, n-nonyl alcohol, n-decanol, sec-undecyl alcohol, trimethylnonyl alcohol, sec-tetradecyl alcohol, sec-heptadecyl alcohol, phenol, cyclohexanol, methylcyclohexanol, benzyl alcohol, ethylene glycol, Alcohol solvents such as 1,2-propylene glycol, 1,3-butylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monophenyl ether, Diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol Mono-n-butyl ether, diethylene glycol mono-n-hexyl ether, ethoxytriglycol, tetraethylene glycol mono-n-butyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, tripropylene glycol monomethyl ether Glycol monoether solvents such as α-terpinene, α-terpineol, myrcene, alloocimene, limonene, dipentene, α-pinene, β-pinene, terpineol, carvone, ocimene, and ferrandrene; water and the like It is done. These are used singly or in combination of two or more.

The content ratio of the dispersion medium in the n-type diffusion layer forming composition is determined in consideration of applicability and donor concentration.
The viscosity of the n-type diffusion layer forming composition is preferably 10 mPa · s or more and 1000000 mPa · s or less, more preferably 50 mPa · s or more and 500000 mPa · s or less in consideration of applicability.

  Next, the manufacturing method of the n type diffused layer and solar cell element of this invention is demonstrated, referring FIG. FIG. 1 is a schematic cross-sectional view conceptually showing an example of the manufacturing process of the solar cell element of the present invention. In the subsequent drawings, common constituent elements are denoted by the same reference numerals.

In FIG. 1A, an alkaline solution is applied to a silicon substrate which is a p-type semiconductor substrate 10 to remove a damaged layer, and a texture structure is obtained by etching.
Specifically, the damaged layer on the silicon surface generated when slicing from the ingot is removed with 20% by mass caustic soda. Next, etching is performed with a mixed solution of 1% by mass caustic soda and 10% by mass isopropyl alcohol to form a texture structure (the description of the texture structure is omitted in the figure). In the solar cell element, by forming a texture structure on the light receiving surface (surface) side, a light confinement effect is promoted, and high efficiency is achieved.

In FIG. 1B, the n-type diffusion layer forming composition layer 11 is formed by applying the n-type diffusion layer forming composition to the surface of the p-type semiconductor substrate 10, that is, the surface that becomes the light receiving surface. In the present invention, the coating method is not limited, and examples thereof include a printing method, a spin method, a brush coating, a spray method, a doctor blade method, a roll coater method, and an ink jet method.
Is not particularly limited as coated amount of the n-type diffusion layer forming composition, for example, be a 0.01g ^{/ m 2} ~100g ^/ m 2 as a glass powder content, 0.1 g ^/ m 2 to 10 g / M ² is preferable.

  Depending on the composition of the n-type diffusion layer forming composition, a drying step for volatilizing the solvent contained in the composition may be necessary after coating. In this case, drying is performed at a temperature of about 80 ° C. to 300 ° C. for 1 minute to 10 minutes when a hot plate is used, and about 10 minutes to 30 minutes when a dryer or the like is used. The drying conditions depend on the solvent composition of the n-type diffusion layer forming composition, and are not particularly limited to the above conditions in the present invention.

Further, when the manufacturing method of the present invention is used, the manufacturing method of the p ⁺ -type diffusion layer (high concentration electric field layer) 14 on the back surface is limited to a method by conversion from an n-type diffusion layer to a p-type diffusion layer with aluminum. Therefore, any conventionally known method can be adopted, and the options of the manufacturing method are expanded. Therefore, for example, the high-concentration electric field layer 14 can be formed by applying the composition 13 containing a Group 13 element such as B (boron).

As the composition 13 containing a Group 13 element such as B (boron), for example, a glass powder containing an acceptor element is used instead of a glass powder containing a donor element, and the same as the composition for forming an n-type diffusion layer. A p-type diffusion layer forming composition constituted as described above can be given. The acceptor element may be an element belonging to Group 13, and examples thereof include B (boron), Al (aluminum), and Ga (gallium). The glass powder containing acceptor element preferably comprises at least one selected from _{B 2 O 3, Al 2 O} 3 and _Ga 2 _{O 3.}
Furthermore, the method for applying the p-type diffusion layer forming composition to the back surface of the silicon substrate is the same as the method for applying the n-type diffusion layer forming composition described above on the silicon substrate.
The high-concentration electric field layer 14 can be formed on the back surface by subjecting the p-type diffusion layer forming composition applied to the back surface to a thermal diffusion treatment similar to the thermal diffusion treatment in the n-type diffusion layer forming composition described later. . The thermal diffusion treatment of the p-type diffusion layer forming composition is preferably performed simultaneously with the thermal diffusion treatment of the n-type diffusion layer forming composition.

Next, the semiconductor substrate 10 on which the n-type diffusion layer forming composition layer 11 is formed is subjected to thermal diffusion treatment at 600 ° C. to 1200 ° C. By this thermal diffusion treatment, as shown in FIG. 1C, the donor element diffuses into the semiconductor substrate, and the n-type diffusion layer 12 is formed. A known continuous furnace, batch furnace, or the like can be applied to the thermal diffusion treatment. Further, the furnace atmosphere during the thermal diffusion treatment can be appropriately adjusted to air, oxygen, nitrogen or the like.
The thermal diffusion treatment time can be appropriately selected according to the content of the donor element contained in the n-type diffusion layer forming composition. For example, it may be 1 minute to 60 minutes, and more preferably 2 minutes to 30 minutes.

  Since a glass layer (not shown) such as phosphate glass is formed on the surface of the n-type diffusion layer 12 formed, this phosphate glass is removed by etching in a normal method. As the etching, a known method such as a method of immersing in an acid such as hydrofluoric acid or a method of immersing in an alkali such as caustic soda can be applied.

  Here, according to the present invention, silver particles are deposited on the glass layer on the surface of the n-type diffusion layer 12, and the glass layer itself exhibits high conductivity. Therefore, it is possible to proceed to the next step (formation of an antireflection film) without performing the etching. Alternatively, without completely removing the glass layer, it is possible to leave a part and proceed to the next step. The presence or absence of the etching step and the degree of etching can be appropriately selected in consideration of the thickness of the formed glass layer, the amount of silver particles deposited, the conductivity of the glass layer, and the like. Therefore, according to the manufacturing method of the present invention, the etching process of the glass layer becomes unnecessary, or etching until the glass layer is completely removed is not required, and the process is simplified.

In the method for forming an n-type diffusion layer of the present invention in which the n-type diffusion layer 12 is formed using the n-type diffusion layer forming composition 11 of the present invention shown in FIGS. Thus, the n-type diffusion layer 12 is formed, and no unnecessary n-type diffusion layer is formed on the back surface or the side surface.
Therefore, in the conventional method of forming an n-type diffusion layer by a gas phase reaction method, a side etching process for removing an unnecessary n-type diffusion layer formed on a side surface is essential. According to the manufacturing method of the invention, the side etching process is not required, and the process is simplified.

Further, in the conventional manufacturing method, it is necessary to convert an unnecessary n-type diffusion layer formed on the back surface into a p-type diffusion layer. As this conversion method, a group 13 element is added to the n-type diffusion layer on the back surface. A method is adopted in which an aluminum paste is applied and baked to diffuse aluminum into the n-type diffusion layer and convert it into a p-type diffusion layer. In this method, conversion to the p-type diffusion layer is sufficient, and in order to form a high-concentration electric field layer of the p ⁺ -type diffusion layer, a certain amount of aluminum is required. There was a need to form. However, since the thermal expansion coefficient of aluminum is significantly different from that of silicon used as a substrate, a large internal stress is generated in the silicon substrate during the firing and cooling process, causing warpage of the silicon substrate. .
This internal stress has a problem that the crystal grain boundary is damaged and the power loss increases. Further, the warp easily causes the element to be damaged in the transportation of the solar cell element in the module process and the connection with the lead wire called the tab wire. In recent years, the thickness of the silicon substrate has been reduced due to the improvement of the slice processing technique, and the elements tend to be easily broken.

However, according to the manufacturing method of the present invention, since an unnecessary n-type diffusion layer is not formed on the back surface, it is not necessary to perform conversion from the n-type diffusion layer to the p ⁺ -type diffusion layer, and it is necessary to increase the thickness of the aluminum layer. Disappear. As a result, generation of internal stress and warpage in the silicon substrate can be suppressed. As a result, it is possible to suppress an increase in power loss and damage to the element.

When the manufacturing method of the present invention is used, the manufacturing method of the p ⁺ -type diffusion layer (high-concentration electric field layer) 14 on the back surface is limited to a method by conversion from an n-type diffusion layer by aluminum to a p ⁺ -type diffusion layer. However, either method can be adopted, and the choice of manufacturing method is expanded.
For example, using a glass powder containing an acceptor element instead of a glass powder containing a donor element, a p-type diffusion layer forming composition configured in the same manner as the n-type diffusion layer forming composition is formed on the back surface (n The p ⁺ -type diffusion layer (high-concentration electric field layer) 14 may be formed on the back surface by applying to the surface opposite to the surface on which the composition for forming the mold diffusion layer is applied and baking.
As will be described later, the material used for the back surface electrode 20 is not limited to Group 13 aluminum, and for example, Ag (silver), Cu (copper), or the like can be applied. In addition, it can be formed thinner than the conventional one.

In FIG. 1 (4), an antireflection film 16 is formed on the n-type diffusion layer 12. The antireflection film 16 is formed by applying a known technique. For example, when the antireflection film 16 is a silicon nitride film, it is formed by a plasma CVD method using a mixed gas of SiH ₄ and NH ₃ as a raw material. At this time, hydrogen diffuses into the crystal, and orbits that do not contribute to the bonding of silicon atoms, that is, dangling bonds and hydrogen are combined to inactivate defects (hydrogen passivation).
More specifically, the mixed gas flow rate ratio NH ₃ / SiH ₄ is 0.05 to 1.0, the reaction chamber pressure is 13.3 Pa (0.1 Torr) to 266.6 Pa (2 Torr), It is formed under conditions where the temperature is 300 ° C. to 550 ° C. and the frequency for plasma discharge is 100 kHz or more.

  In FIG. 1 (5), the surface electrode 18 is formed on the antireflection film 16 on the surface (light-receiving surface) by printing and drying the surface electrode metal paste by screen printing. The metal paste for a surface electrode contains (1) metal particles and (2) glass particles as essential components, and includes (3) a resin binder and (4) other additives as necessary.

  Next, the back electrode 20 is also formed on the high-concentration electric field layer 14 on the back surface. As described above, in the present invention, the material and forming method of the back electrode 20 are not particularly limited. For example, the back electrode 20 may be formed by applying and drying a back electrode paste containing a metal such as aluminum, silver, or copper. At this time, a silver paste for forming a silver electrode may be partially provided on the back surface for connection between elements in the module process.

  In FIG. 1 (6), an electrode is baked and a solar cell element is completed. When firing at a temperature of 600 ° C. to 900 ° C. for several seconds to several minutes, the antireflection film 16 that is an insulating film is melted by the glass particles contained in the electrode metal paste on the surface side, and the silicon 10 surface is also partially melted. The metal particles (for example, silver particles) in the paste form a contact portion with the silicon substrate 10 and solidify. Thereby, the formed surface electrode 18 and the silicon substrate 10 are electrically connected. This is called fire-through.

  The shape of the surface electrode 18 will be described. The surface electrode 18 includes a bus bar electrode 30 and finger electrodes 32 intersecting with the bus bar electrode 30. FIG. 2A is a plan view of a solar cell element in which the surface electrode 18 includes a bus bar electrode 30 and a finger electrode 32 intersecting with the bus bar electrode 30 as viewed from the surface. FIG. 2B is an enlarged perspective view illustrating a part of FIG.

  Such a surface electrode 18 can be formed by means such as screen printing of the above-described metal paste, plating of an electrode material, or vapor deposition of an electrode material by electron beam heating in a high vacuum. The surface electrode 18 composed of the bus bar electrode 30 and the finger electrode 32 is generally used as an electrode on the light receiving surface side and is well known, and it is possible to apply known forming means for the bus bar electrode and finger electrode on the light receiving surface side. it can.

In the above description, the solar cell element in which the n-type diffusion layer is formed on the front surface, the p ⁺ -type diffusion layer is formed on the back surface, and the front surface electrode and the back surface electrode are further provided on the respective layers has been described. If a layer formation composition is used, it is also possible to produce a back contact type solar cell element.
The back contact type solar cell element has all electrodes provided on the back surface to increase the area of the light receiving surface. That is, in the back contact type solar cell element, it is necessary to form both the n-type diffusion region and the p ⁺ -type diffusion region on the back surface to form a pn junction structure. The n-type diffusion layer forming composition of the present invention can form an n-type diffusion site at a specific site, and can therefore be suitably applied to the production of a back contact type solar cell element.

  Examples of the present invention will be described more specifically below, but the present invention is not limited to these examples. Unless otherwise stated, all chemicals used reagents. “%” Means “% by mass” unless otherwise specified.

[Example 1]
_{P 2 O 5 -AgO-V 2} O 5 type glass _{(P 2 O 5: 35.1%} , AgO: 40.3%, V 2 O 5: 10%, BaO: 10.4%, K 2 O: 4.2%) powder (hereinafter sometimes abbreviated as “G01”) was prepared. 20 g of the obtained glass powder (G01), 0.3 g of ethyl cellulose, and 7 g of 2- (2-butoxyethoxy) ethyl acetate were mixed using an automatic mortar kneader to make a paste, and an n-type diffusion layer forming composition A product was prepared.

  Next, the prepared paste was applied by screen printing to the p-type silicon substrate surface on which the texture was formed, and dried on a hot plate at 150 ° C. for 5 minutes. Subsequently, a thermal diffusion treatment was performed for 10 minutes in an electric furnace set at 1000 ° C., and then the substrate was immersed in a 10% hydrofluoric acid aqueous solution for 5 minutes to remove the glass layer, and washed with running water. No glass layer remained on the p-type silicon substrate surface.

  Subsequently, an antireflection film (silicon nitride film) having a thickness of 90 nm was formed on the surface on which the n-type diffusion layer was formed by plasma CVD. A commercially available silver electrode paste (manufactured by DuPont, trade name: PV159) was printed on the light receiving surface so as to have an electrode pattern as shown in FIG. The electrode pattern was composed of a finger line with a width of 150 μm and a bus bar with a width of 1.5 mm, and the printing conditions (screen plate mesh, printing speed, printing pressure) were appropriately adjusted so that the film thickness after firing was 20 μm. This was placed in an oven heated to 150 ° C. for 15 minutes, and the solvent was removed by evaporation.

  Subsequently, an aluminum electrode paste (manufactured by PVG Solutions, trade name: Hyper BSF Al Paste) was printed on the entire back surface using the screen printing method as described above. Moreover, the printing conditions of the aluminum electrode paste were appropriately adjusted so that the film thickness of the aluminum electrode was 30 μm. This was placed in an oven heated to 150 ° C. for 15 minutes, and the solvent was removed by evaporation.

  Subsequently, using a tunnel furnace (manufactured by Noritake Co., Ltd., single-row transport W / B tunnel furnace), a heat treatment (firing) is performed in an air atmosphere at a firing maximum temperature of 800 ° C. and a holding time of 10 seconds. The formed solar cell element 1 was produced.

[Example 2]
A solar cell element 2 was produced by forming an n-type diffusion layer in the same manner as in Example 1 except that the antireflection film and the electrode were formed without performing hydrofluoric acid treatment and running water washing after the thermal diffusion treatment. .

[Example 3]
An n-type diffusion layer was formed in the same manner as in Example 1 except that the thermal diffusion treatment time was 20 minutes, and a solar cell element 3 was produced. The glass layer did not remain on the surface of the p-type silicon substrate after the hydrofluoric acid treatment.

[Example 4]
An n-type diffusion layer was formed in the same manner as in Example 2 except that the thermal diffusion treatment time was 20 minutes, and a solar cell element 4 was produced.

[Example 5]
An n-type diffusion layer was formed in the same manner as in Example 1 except that the temperature of the thermal diffusion treatment was set to 900 ° C., and a solar cell element 5 was produced. The glass layer did not remain on the surface of the p-type silicon substrate after the hydrofluoric acid treatment.

[Example 6]
An n-type diffusion layer was formed in the same manner as in Example 2 except that the temperature of the thermal diffusion treatment was 900 ° C., and a solar cell element 6 was produced.

[Example 7]
The glass powder composition was P ₂ O ₅ —AgO—SnO-based glass (P ₂ O ₅ : 44.1%, AgO: 25.8%, SnO: 21.3%, CaO: 8.8%, hereinafter “G02”) The solar cell element 7 was fabricated by forming an n-type diffusion layer in the same manner as in Example 1 except that the solar cell element 7 was abbreviated. The glass layer did not remain on the surface of the p-type silicon substrate after the hydrofluoric acid treatment.

[Example 8]
An n-type diffusion layer was formed in the same manner as in Example 7 except that the antireflection film and the electrode were formed without performing hydrofluoric acid treatment and running water washing after the thermal diffusion treatment, and the solar cell element 8 was produced. .

[Example 9]
An n-type diffusion layer was formed in the same manner as in Example 7 except that the temperature of the thermal diffusion treatment was set to 900 ° C., and a solar cell element 9 was produced. The glass layer did not remain on the surface of the p-type silicon substrate after the hydrofluoric acid treatment.

[Example 10]
An n-type diffusion layer was formed in the same manner as in Example 8 except that the temperature of the thermal diffusion treatment was set to 900 ° C., and a solar cell element 10 was produced.

[Example 11]
An n-type diffusion layer was formed in the same manner as in Example 7 except that the temperature of the thermal diffusion treatment was 800 ° C., and a solar cell element 11 was produced. The glass layer did not remain on the surface of the p-type silicon substrate after the hydrofluoric acid treatment.

[Example 12]
An n-type diffusion layer was formed in the same manner as in Example 8 except that the temperature of the thermal diffusion treatment was 800 ° C., and a solar cell element 12 was produced.

[Example 13]
The glass powder composition was P ₂ O ₅ —AgO—ZnO-based glass (P ₂ O ₅ : 40.0%, AgO: 40.0%, ZnO: 10.5%, CaO: 9.5%, hereinafter “G03”) The solar cell element 13 was fabricated by forming an n-type diffusion layer in the same manner as in Example 1 except that the solar cell element 13 was sometimes abbreviated. The glass layer did not remain on the surface of the p-type silicon substrate after the hydrofluoric acid treatment.

[Example 14]
An n-type diffusion layer was formed in the same manner as in Example 13 except that the antireflection film and the electrode were formed without performing hydrofluoric acid treatment and washing with running water after the thermal diffusion treatment, and the solar cell element 14 was produced. .

[Example 15]
An n-type diffusion layer was formed in the same manner as in Example 13 except that the temperature of the thermal diffusion treatment was 950 ° C., and a solar cell element 15 was produced. No glass layer remained on the p-type silicon substrate surface after the hydrofluoric acid treatment.

[Example 16]
An n-type diffusion layer was formed in the same manner as in Example 14 except that the temperature of the thermal diffusion treatment was 950 ° C., and a solar cell element 16 was produced.

[Example 17]
An n-type diffusion layer was formed in the same manner as in Example 13 except that the thermal diffusion treatment temperature was 900 ° C. and the treatment time was 20 minutes, and a solar cell element 17 was produced. The glass layer did not remain on the surface of the p-type silicon substrate after the hydrofluoric acid treatment.

[Example 18]
An n-type diffusion layer was formed in the same manner as in Example 14 except that the thermal diffusion treatment temperature was 900 ° C. and the treatment time was 20 minutes, and a solar cell element 18 was produced.

[Comparative Example 1]
An n-type diffusion layer was formed on the p-type silicon substrate surface on which the texture was formed by the following general method. First, the silicon substrate was placed on a quartz boat and inserted into a quartz tube heated to 850 ° C. An n-type diffusion layer was formed by diffusing phosphorus over the entire surface of the substrate by a gas diffusion method using phosphorus oxychloride (POCl ₃ ) as a diffusion source. Specifically, nitrogen (N ₂ ) as a carrier gas was passed through liquid POCl ₃ filled in a bubbler container, and POCl ₃ was introduced into the quartz tube. When POCl ₃ is mixed with oxygen (O ₂ ), P ₂ O ₅ is deposited on the surface of the silicon substrate, and this serves as a diffusion source to diffuse phosphorus into the silicon substrate. The heat treatment time was 30 minutes.

  Thereafter, a 10% hydrofluoric acid aqueous solution treatment was applied to the entire surface of the silicon substrate, and the phosphate glass formed on the substrate surface was removed. Subsequent formation of the antireflection film, printing of the electrode paste, and baking were performed in the same manner as in Example 1 to fabricate a solar cell element C1.

[Comparative Example 2]
An n-type diffusion layer was formed in the same manner as in Comparative Example 1 except that the antireflection film and the electrode were formed without performing hydrofluoric acid treatment and running water washing after the thermal diffusion treatment, and a solar cell element C2 was produced. .

[Comparative Example 3]
P ₂ O ₅ -V ₂ O ₅ -based glass _{(P 2 O 5: 55.1%} , V 2 O 5: 30.3%, BaO: 10.4%, K 2 O: 4.2%) powder ( Hereinafter, “G04” may be abbreviated). 20 g of the obtained glass powder (G04), 0.3 g of ethyl cellulose, and 7 g of 2- (2-butoxyethoxy) ethyl acetate were mixed using an automatic mortar kneader to make a paste, and an n-type diffusion layer forming composition A product was prepared.
Next, the prepared paste was applied by screen printing to the p-type silicon substrate surface on which the texture was formed, and dried on a hot plate at 150 ° C. for 5 minutes. Subsequently, a thermal diffusion treatment was performed for 10 minutes in an electric furnace set at 1000 ° C. to form an n-type diffusion layer.

  Thereafter, without performing hydrofluoric acid treatment, an antireflection film and an electrode were formed in the same manner as in Example 1 to produce a solar cell element C3.

[Comparative Example 4]
P ₂ O ₅ —ZnO-based glass (P ₂ O ₅ : 45.0%, ZnO: 45.5%, CaO: 9.5%, hereinafter sometimes abbreviated as “G05”) was prepared. 20 g of the obtained glass powder (G05), 0.3 g of ethyl cellulose, and 7 g of 2- (2-butoxyethoxy) ethyl acetate were mixed using an automatic mortar kneader to make a paste, and an n-type diffusion layer forming composition A product was prepared.

  Next, the prepared paste was applied by screen printing to the p-type silicon substrate surface on which the texture was formed, and dried on a hot plate at 150 ° C. for 5 minutes. Subsequently, a thermal diffusion treatment was performed for 10 minutes in an electric furnace set at 1000 ° C. to form an n-type diffusion layer.

  Thereafter, without performing hydrofluoric acid treatment, an antireflection film and an electrode were formed in the same manner as in Example 1 to fabricate a solar cell element C4.

  Table 1 collectively shows the conditions for forming the n-type diffusion layer and the conditions for producing the solar cell in the examples and comparative examples.

<Evaluation>
Evaluation of the produced solar cell element is as follows: WXS-155S-10 manufactured by Wacom Denso Co., Ltd. as pseudo-sunlight, and I-V CURVE TRACER MP-160 (manufactured by EKO INSTRUMENT Co., Ltd.) as a current-voltage (IV) evaluation measuring instrument. ) Was combined with the measuring device. Jsc (short-circuit current), Voc (open circuit voltage), FF (fill factor), and Eff (conversion efficiency) indicating power generation performance as a solar cell are JIS-C-8912, JIS-C-8913, and JIS-C-, respectively. It is obtained by performing measurement according to 8914. In the solar cell element having a double-sided electrode structure, the obtained measured values are converted into relative values with the measured value of Comparative Example 1 (solar cell element C1) as 100.0, and are shown in Table 2.

From Table 2, it can be seen that in Comparative Examples 2 to 4, the power generation performance was degraded as compared with Comparative Example 1. This can be considered as follows. In Comparative Example 2, since the hydrofluoric acid treatment was not performed after forming the n-type diffusion layer by POCl ₃ , the resistance of the phosphate glass formed on the surface of the n-type diffusion layer caused the n-type diffusion on the electrode and the silicon substrate. It is thought that ohmic contact between layers was hindered. Also in Comparative Example 3 and Comparative Example 4, since the glass powder does not contain silver oxide, the resistance of the molten glass layer formed during the thermal diffusion treatment is increased, and the resistance between the electrode and the n-type diffusion layer on the silicon substrate is increased. It is thought that ohmic contact was insufficient.

  On the other hand, the power generation performance of the solar cell elements produced in Examples 1 to 18 was almost equal to the measured value of the solar cell element of Comparative Example 1. In particular, good power generation performance was exhibited even when hydrofluoric acid treatment was not performed after thermal diffusion treatment. This is presumably because the silver particles were precipitated in the glass during the thermal diffusion treatment and the conductivity was improved.

  In Comparative Example 1, the sheet resistance of the back surface to which the n-type diffusion layer forming composition was not applied was 40.4 Ω / □, and the n-type diffusion layer was also formed on the back surface. On the other hand, in Examples 1 to 18, the sheet resistance on the back surface to which the n-type diffusion layer forming composition was not applied exceeds 1000000, and the n-type diffusion layer is not substantially formed. It was judged. Therefore, when the n-type diffusion layer forming compositions of Examples 1 to 18 are used, the n-type diffusion layer is formed in a specific portion without forming the n-type diffusion layer in an unnecessary region. I was able to.

10 p-type semiconductor substrate 12 n-type diffusion layer 14 high-concentration electric field layer 16 antireflection film 18 surface electrode 20 back electrode (electrode layer)
30 Busbar electrode 32 Finger electrode

Claims (6)

  An n-type diffusion layer forming composition containing a glass powder containing a donor element and silver oxide, and a dispersion medium.   The n-type diffusion layer forming composition according to claim 1, wherein the donor element is at least one selected from P (phosphorus) and Sb (antimony). The glass powder containing the donor element and silver oxide includes at least one donor element-containing material selected from P ₂ O ₃ , P ₂ O ₅ and Sb ₂ O ₃ , AgO, SiO ₂ , K ₂ O, At least one glass component material selected from Na ₂ O, Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, V ₂ O ₅ , SnO, ZrO ₂ , and MoO ₃ ; The n-type diffused layer formation composition of Claim 1 or Claim 2 containing this.   A method for producing an n-type diffusion layer, comprising: a step of applying the n-type diffusion layer forming composition according to any one of claims 1 to 3 on a semiconductor substrate; and a step of applying a thermal diffusion treatment. .   The process of apply | coating the n-type diffused layer formation composition of any one of Claims 1-3 on a semiconductor substrate, the process of giving a thermal diffusion process, and forming an n-type diffused layer, and formation Forming an electrode on the formed n-type diffusion layer, and a method for manufacturing a solar cell element.   The glass layer formed on the n-type diffusion layer is not removed or a part of the glass layer is removed between the step of forming the n-type diffusion layer and the step of forming the electrode. Item 6. A method for producing a solar cell element according to Item 5.