JP6630997B2 - Composition for forming passivation layer protective layer, solar cell element, method for manufacturing the same, and solar cell - Google Patents

Description

  The present invention relates to a composition for forming a passivation layer protective layer, a solar cell element, a method for producing the same, and a solar cell.

A description will be given of a manufacturing process of a conventional silicon solar cell element.
First, a texture structure is formed on the surface (at least one of the light-receiving surface and the back surface) of the p-type silicon substrate so as to promote the light confinement effect and achieve high efficiency, and then phosphorus oxychloride (POCl ₃ ), nitrogen and oxygen In the mixed gas atmosphere at 800 ° C. to 900 ° C. for several tens minutes to form an n-type diffusion layer uniformly on the surface of the p-type silicon substrate. In this conventional method, since phosphorus is diffused using a mixed gas, an n-type diffusion layer is formed not only on the front surface, which is the light receiving surface, but also on the side and back surfaces. Therefore, side etching or the like for removing the n-type diffusion layer formed on the side surface is performed. Further, it is necessary to convert the n-type diffusion layer formed on the back surface into a p ⁺ -type diffusion layer. For this reason, an aluminum paste containing an aluminum powder and a binder is applied to the entire back surface and heat-treated (fired) to convert the n-type diffusion layer into a p ⁺ -type diffusion layer called BSF (Back Surface Field). In addition, an aluminum electrode is formed to obtain an ohmic contact.

However, an aluminum electrode formed from an aluminum paste has low conductivity. Therefore, in order to reduce the sheet resistance, the aluminum electrode usually formed on the entire back surface must have a thickness of about 10 μm to 20 μm after heat treatment (firing). Furthermore, since the coefficient of thermal expansion is significantly different between silicon and aluminum, a large internal stress is generated in the silicon substrate on the aluminum substrate on which the aluminum electrode is formed during the heat treatment (firing) and cooling, and the crystal grain boundary is formed. Damage, growth of crystal defects, and warpage.
In addition, since the Al-Si alloy contained in the alloy layer formed at the interface between BSF or the aluminum electrode and silicon has a light absorbing ability, this alloy layer is a major factor in lowering the power generation efficiency.

In order to solve these problems, a point contact method has been proposed in which an aluminum paste is applied to a part of the surface of a silicon substrate to partially form a p + type diffusion layer and an aluminum electrode (for example, see Patent Document 1). 1).
In the case of a solar cell having a point contact structure on a surface opposite to such a light receiving surface (hereinafter, also referred to as a “back surface”), it is necessary to suppress the recombination rate of minority carriers on the surface of a portion other than the aluminum electrode. is there. For this purpose, an SiO ₂ film or the like has been proposed as a back surface passivation layer (for example, see Patent Document 2). As a passivation effect by forming such an SiO ₂ film, an effect of terminating dangling bonds of silicon atoms in the surface layer portion on the back surface of the silicon substrate and reducing the surface state density causing recombination can be mentioned. Can be

As another method for suppressing the recombination of minority carriers, there is a method of reducing the minority carrier density by an electric field in which fixed charges are generated in the passivation layer. Such a passivation effect is generally called an electric field effect, and an aluminum oxide (Al ₂ O ₃ ) film or the like has been proposed as a material having a negative fixed charge (for example, see Patent Document 3).
Such a passivation layer is generally formed by a method such as an ALD (Atomic Layer Deposition) method or a CVD (Chemical Vapor Deposition) method (for example, see Non-Patent Document 1). Furthermore, a method of forming a SiNx layer on a passivation layer by a PECVD (Plasma Enhanced Chemical Vapor Deposition) method has been proposed (for example, see Non-Patent Document 2).

Japanese Patent No. 3107287 JP-A-2004-6565 Japanese Patent No. 4767110

Journal of Applied Physics, 104 (2008), 113703-1 to 113703-7. IEEE Journal of Photovoltaics, 3 (2013), 690-696

  In the method described in Non-Patent Document 2, the SiNx layer is formed on the entire surface of the semiconductor substrate on the side where the passivation layer is formed by using the PECVD method. Therefore, after the formation of the SiNx layer, a step of forming a pattern of the SiNx layer by etching the region where the aluminum electrode is to be formed by laser irradiation, photolithography, or the like is required, which is complicated.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and provides a passivation method capable of forming a protective layer excellent in pattern formability and excellent in resistance to heat treatment of an electrode forming paste by a simple method. It is an object to provide a composition for forming a layer protective layer. Further, the present invention provides a solar cell element obtained by using the composition for forming a passivation layer protective layer of the present invention, comprising a protective layer having excellent resistance to heat treatment of an electrode forming paste, and having excellent conversion efficiency. And a method for manufacturing the same, and a solar cell.

Specific means of the present invention will be described below.
<1> A composition for forming a passivation layer protective layer, comprising a compound represented by the following general formula (I) and a resin.

[In the general formula (I), R ² each independently represents an alkyl group. n represents an integer of 1 to 3. X ² and X ³ each independently represent an oxygen atom or a methylene group. R ³ , R ⁴ and R ⁵ each independently represent a hydrogen atom or an alkyl group. ]

<2> The content of the compound represented by the general formula (I) is 0.1% by mass to 80% by mass with respect to the total mass of the composition for forming a passivation layer protective layer. A composition for forming a passivation layer protective layer.
<3> The passivation layer protective layer according to <1> or <2>, wherein the content of the resin is 0.1% by mass to 30% by mass based on the total mass of the composition for forming the passivation layer protective layer. Forming composition.

<4> forming a passivation layer containing aluminum oxide on at least one surface of the semiconductor substrate;
The composition for forming a passivation layer protective layer according to any one of <1> to <3> is applied to at least a part of the passivation layer in a pattern to form a composition layer for forming a protective layer. Forming a protective layer by heat treatment;
Providing an electrode on the side of the semiconductor substrate on which the passivation layer and the protective layer are formed,
A method for manufacturing a solar cell element comprising:

<5> The method for manufacturing a solar cell element according to <4>, wherein the temperature of the heat treatment is 300 ° C to 900 ° C.
<6> The method for manufacturing a solar cell element according to <4> or <5>, wherein the application of the composition for forming a passivation layer protective layer is performed by a screen printing method or an inkjet method.
<7> A solar cell element manufactured by the method for manufacturing a solar cell element according to any one of <4> to <6>.

<8> a semiconductor substrate;
A passivation layer provided on at least one surface of the semiconductor substrate and containing aluminum oxide;
A protective layer provided on the passivation layer and being a heat-treated product of the composition for forming a passivation layer protective layer according to any one of <1> to <3>;
An electrode provided on a side of the semiconductor substrate on which the passivation layer and the protective layer are formed;
A solar cell element having:

<9> The solar cell element according to <7> or <8>,
A wiring material arranged on the electrode of the solar cell element,
A solar cell having:

  According to the present invention, it is possible to provide a passivation layer protective layer forming composition capable of forming a protective layer excellent in pattern formability and excellent in resistance to heat treatment of an electrode forming paste by a simple method. it can. Further, a solar cell element having a protective layer obtained by using the composition for forming a passivation layer protective layer of the present invention and having excellent resistance to heat treatment of an electrode forming paste, and having excellent conversion efficiency, and a method of manufacturing the same In addition, a solar cell can be provided.

It is sectional drawing which shows typically the manufacturing method of the solar cell element which concerns on one Embodiment of this invention. It is sectional drawing which shows typically a part of manufacturing method of the solar cell element which concerns on another embodiment of this invention. It is a schematic plan view showing an example of the light-receiving surface of the solar cell element of the present invention. It is a schematic plan view showing an example of a pattern in the back of a protective layer concerning the present invention. It is a schematic plan view which shows another example of the pattern in the back surface of the protective layer which concerns on this invention. FIG. 5 is an enlarged schematic plan view of a portion A in FIG. 4. FIG. 6 is an enlarged schematic plan view of a portion B in FIG. 4 or 5. It is a schematic plan view showing an example of the back of the solar cell element of the present invention. It is a figure explaining an example of the manufacturing method of the solar cell of the present invention.

In the present specification, the term “step” is included in the term as well as an independent step, even if it cannot be clearly distinguished from other steps as long as the purpose of the step is achieved.
Further, a numerical range indicated by using “to” indicates a range including numerical values described before and after “to” as a minimum value and a maximum value, respectively.
Further, the content of each component in the composition, when there are a plurality of substances corresponding to each component in the composition, unless otherwise specified, means the total amount of the plurality of substances present in the composition .
Further, in this specification, the term “layer” includes, in a plan view, a configuration of a partly formed shape in addition to a configuration of a partly formed shape.

<Composition for forming passivation layer protective layer>
The composition for forming a passivation layer protective layer of the present invention is a composition for forming a passivation layer protective layer containing a compound represented by the following general formula (I) and a resin.

[In the general formula (I), R ² each independently represents an alkyl group. n represents an integer of 1 to 3. X ² and X ³ each independently represent an oxygen atom or a methylene group. R ³ , R ⁴ and R ⁵ each independently represent a hydrogen atom or an alkyl group. ]

Since the composition for forming a passivation layer protective layer of the present invention has the above-described configuration, it is possible to form a protective layer having excellent pattern formability and excellent resistance to heat treatment of an electrode forming paste by a simple method. It is possible. The reason for this is not clear, but is presumed as follows.
Since the composition for forming a passivation layer protective layer of the present invention is a composition, it can be selectively applied to a desired region on a semiconductor substrate in a desired shape, and is excellent in pattern formability. Further, by containing the compound represented by the general formula (I), aluminum oxide is generated by heat treatment, the passivation effect of the passivation layer is further improved, and the protective layer having excellent resistance to heat treatment of the electrode forming paste is provided. Can be obtained. Further, by containing a resin, a composition for forming a passivation layer protective layer is formed by applying the composition for forming a passivation layer protective layer onto a semiconductor substrate (hereinafter, also referred to as a “composition layer for forming a protective layer”). Is improved), and a desired shape can be formed.

(Compound represented by the general formula (I))
The composition for forming a passivation layer protective layer of the present invention (hereinafter, also abbreviated as “composition for forming protective layer”) contains a compound represented by the following general formula (I).

[In the general formula (I), R ² each independently represents an alkyl group. n represents an integer of 1 to 3. X ² and X ³ each independently represent an oxygen atom or a methylene group. R ³ , R ⁴ and R ⁵ each independently represent a hydrogen atom or an alkyl group. ]
By containing the compound represented by the general formula (I), the passivation effect of the passivation layer is further improved, and a protective layer having excellent resistance to heat treatment of the electrode forming paste tends to be obtained. This can be considered as follows.

The compound represented by the general formula (I) (hereinafter also referred to as “specific organoaluminum compound”) is a compound called aluminum chelate or the like, and preferably has an aluminum chelate structure in addition to an aluminum alkoxide structure. . In addition, Nippon Seramikkusu Kyokai Gakujutsu Ronbunshi, vol. 97, pp 369-399 (1989), the specific organoaluminum compound becomes aluminum oxide (Al ₂ O ₃ ) by heat treatment (firing). As described above, since the chemical species is the same as that of aluminum oxide as the lower passivation layer, it is considered that the protective layer can be formed without lowering the passivation function of the passivation layer.

In the general formula (I), R ² each independently represents an alkyl group, preferably an alkyl group having 1 to 8 carbon atoms, and more preferably an alkyl group having 1 to 4 carbon atoms. The alkyl group represented by R ² may be linear or branched. Specific examples of the alkyl group represented by R ² include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a t-butyl group, a hexyl group, and octyl. Group, 2-ethylhexyl group, 3-ethylhexyl group and the like. Among them, the alkyl group represented by R ² is preferably an unsubstituted alkyl group having 1 to 8 carbon atoms from the viewpoint of storage stability and passivation effect of the composition for forming a protective layer, and has 1 to 4 carbon atoms. Is more preferably an unsubstituted alkyl group.

In the general formula (I), n represents an integer of 1 to 3. n is preferably 1 or 3 from the viewpoint of storage stability of the composition for forming a protective layer, and more preferably 1 from the viewpoint of solubility of the specific organic aluminum compound.
X ² and X ³ each independently represent an oxygen atom or a methylene group. From the viewpoint of storage stability, at least one of X ² and X ³ is preferably an oxygen atom.

R ³ , R ⁴ and R ⁵ in the general formula (I) each independently represent a hydrogen atom or an alkyl group. The alkyl group represented by R ³ , R ⁴ and R ⁵ may be linear or branched. The alkyl group represented by R ³ , R ^4, and R ⁵ is preferably an alkyl group having 1 to 8 carbon atoms, and more preferably an alkyl group having 1 to 4 carbon atoms. Specific examples of the alkyl group represented by R ³ , R ⁴ and R ⁵ include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group and a t-butyl group. Group, hexyl group, octyl group, ethylhexyl group and the like. The alkyl group represented by R ³ , R ⁴ and R ⁵ may have a substituent or may be unsubstituted, and is preferably unsubstituted.

Among them, R ³ and R ⁴ in the general formula (I) are each independently a hydrogen atom or a hydrogen atom from the viewpoints of storage stability of the composition for forming a protective layer and resistance of the protective layer when the paste for forming an electrode is heat-treated. It is preferably an unsubstituted alkyl group having 1 to 8 carbon atoms, more preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 4 carbon atoms.
Further, R ⁵ in the general formula (I) is a hydrogen atom or an unsubstituted alkyl group having 1 to 8 carbon atoms from the viewpoint of storage stability and resistance of the protective layer when the electrode forming paste is heat-treated. Is preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 4 carbon atoms.

The compound represented by the general formula (I) is a compound in which n is an integer of 1 to 3 and R ⁵ is each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms from the viewpoint of storage stability. It is preferable that

In the compound represented by the general formula (I), n is an integer of 1 to 3 and R ² is independently from the viewpoint of storage stability and resistance of the protective layer when the electrode forming paste is heat-treated. An alkyl group having 1 to 4 carbon atoms, at least one of X ² and X ³ is an oxygen atom, and R ³ and R ⁴ are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, ⁵ is preferably a compound in which each is independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
In the compound represented by the general formula (I), n is an integer of 1 to 3, R ² is each independently an unsubstituted alkyl group having 1 to 4 carbon atoms, and at least X ² and X ³ When one is an oxygen atom, R ³ or R ⁴ bonded to the oxygen atom is an alkyl group having 1 to ⁴ carbon atoms, and when X ² or X ³ is a methylene group, R ³ or R ³ bonded to the methylene group is More preferably, R ⁴ is a hydrogen atom, and R ⁵ is a hydrogen atom.

  Specific examples of the compound represented by the general formula (I) include aluminum ethyl acetoacetate diisopropylate, tris (ethyl acetoacetate) aluminum and the like.

  As the compound represented by the general formula (I), a prepared product or a commercially available product may be used. Commercially available products include Kawaken Fine Chemical Co., Ltd., "ALCH", "ALCH-50F", "ALCH-75", "ALCH-TR", "ALCH-TR-20" (all trade names) and the like. be able to.

  The compound represented by the general formula (I) can be prepared by mixing an aluminum trialkoxide with a compound having a specific structure having two carbonyl groups described below. Alternatively, a commercially available aluminum chelate compound may be used.

  When the above-mentioned aluminum trialkoxide is mixed with a compound having a specific structure having two carbonyl groups, at least a part of the alkoxide group of the aluminum trialkoxide is replaced with a compound having a specific structure, thereby forming an aluminum chelate structure. At this time, if necessary, a liquid medium may be present, and heat treatment, addition of a catalyst or the like may be performed. By substituting at least a part of the aluminum alkoxide structure with an aluminum chelate structure, the stability of the compound represented by the general formula (I) to hydrolysis and polymerization is improved, and a protective layer-forming composition containing the same is provided. Tends to be more improved in storage stability.

  The compound having a specific structure having two carbonyl groups described above is at least one selected from the group consisting of β-diketone compounds, β-ketoester compounds, and malonic diesters from the viewpoint of reactivity and storage stability. Is preferred.

  Specific examples of the β-diketone compound include acetylacetone, 3-methyl-2,4-pentanedione, 2,3-pentanedione, 3-ethyl-2,4-pentanedione, and 3-butyl-2,4-pentane. Dione, 2,2,6,6-tetramethyl-3,5-heptanedione, 2,6-dimethyl-3,5-heptanedione, 6-methyl-2,4-heptanedione and the like can be mentioned.

  As the β-ketoester compound, specifically, methyl acetoacetate, ethyl acetoacetate, n-propyl acetoacetate, isopropyl acetoacetate, isobutyl acetoacetate, n-butyl acetoacetate, t-butyl acetoacetate, n-pentyl acetoacetate, Isopentyl acetoacetate, n-hexyl acetoacetate, n-octyl acetoacetate, n-heptyl acetoacetate, 3-pentyl acetoacetate, ethyl 2-acetylheptanoate, ethyl 2-methylacetoacetate, ethyl 2-butylacetoacetate, hexylacetoacetate Ethyl, ethyl 4,4-dimethyl-3-oxovalerate, ethyl 4-methyl-3-oxovalerate, ethyl 2-ethylacetoacetate, methyl 4-methyl-3-oxovalerate, ethyl 3-oxohexanoate, Ethyl 3-oxovalerate, methyl 3-oxovalerate, 3 Methyl-oxohexanoate, ethyl 3-oxo heptanoic acid, 3-oxo heptanoic acid methyl, can be mentioned 4,4-dimethyl-3-oxo-valerate, such as methyl.

  Specific examples of the malonate diester include dimethyl malonate, diethyl malonate, di-n-propyl malonate, diisopropyl malonate, di-n-butyl malonate, di-t-butyl malonate, dihexyl malonate, and malonate. T-butylethyl acid, diethyl methylmalonate, diethylethylmalonate, diethylisopropylmalonate, diethyln-butylmalonate, diethylsec-butylmalonate, diethylisobutylmalonate, diethyl 1-methylbutylmalonate and the like. Can be.

  The number of aluminum chelate structures can be controlled, for example, by appropriately adjusting the mixing ratio of the above-described aluminum trialkoxide and a compound having a specific structure having two carbonyl groups. Further, a compound having a desired structure may be appropriately selected from commercially available aluminum chelate compounds.

  Among the compounds represented by the general formula (I), from the viewpoint of the resistance of the protective layer when the electrode forming paste is heat-treated and the compatibility with the solvent contained as necessary, aluminum ethyl acetate It is preferable to use at least one selected from the group consisting of acetate diisopropylate and triisopropoxy aluminum, and it is more preferable to use aluminum ethyl acetoacetate diisopropylate.

  The presence of the aluminum chelate structure in the compound represented by the general formula (I) can be confirmed by a commonly used analytical method. For example, it can be confirmed based on an infrared spectrum, a nuclear magnetic resonance spectrum and a melting point.

  The compound represented by the general formula (I) may be liquid or solid, and is not particularly limited. A compound represented by the general formula (I) having good stability at room temperature (25 ° C.) and good solubility or dispersibility from the viewpoint of the resistance of the protective layer and the storage stability when the electrode forming paste is heat-treated. By using, the uniformity of the formed protective layer is further improved, and it becomes easy to stably obtain the resistance of the protective layer when heat-treating the desired electrode forming paste.

The content of the compound represented by the general formula (I) in the protective layer forming composition of the present invention is not particularly limited. The content of the compound represented by the general formula (I) is preferably 0.1% by mass to 80% by mass, and more preferably 0.5% by mass to 80% by mass relative to the total mass of the composition for forming a passivation layer protective layer. It is more preferably 80% by mass, still more preferably 1% by mass to 75% by mass, particularly preferably 2% by mass to 70% by mass, and extremely preferably 3% by mass to 70% by mass. preferable.
When the content of the compound represented by the general formula (I) is 0.1% by mass or more, the storage stability of the composition for forming a protective layer tends to be improved. When the content of the compound represented by the general formula (I) is set to 80% by mass or less, the resistance of the protective layer when the electrode forming paste is heat-treated tends to be improved.

(resin)
The composition for forming a passivation layer protective layer of the present invention further includes a resin. By including the resin, the shape stability of the protective layer forming composition layer formed by applying the protective layer forming composition on the semiconductor substrate is further improved, and the protective layer forming composition layer is formed. There is a tendency that a protective layer can be selectively formed in a desired shape in a region having a desired shape.

  The type of resin is not particularly limited. When applying the composition for forming a passivation layer protective layer onto a semiconductor substrate, it is preferable that the resin be a resin whose viscosity can be adjusted to a range where a good pattern can be formed. Specific examples of the resin include polyvinyl alcohol, polyacrylamide, polyacrylamide derivatives, polyvinylamide, polyvinylamide derivatives, polyvinylpyrrolidone, polyethylene oxide, polyethylene oxide derivatives, polysulfonic acid, acrylamide alkylsulfonic acid, cellulose, and cellulose derivatives (carboxymethylcellulose, Cellulose ethers such as hydroxyethylcellulose and ethylcellulose), gelatin, gelatin derivatives, starch, starch derivatives, sodium alginate, sodium alginate derivatives, xanthan, xanthan derivatives, guar gum, guar gum derivatives, scleroglucan, scleroglucan derivatives, tragacanth, tragacanth Derivatives, dextrins, dextrin derivatives, (meth) Examples thereof include a luic acid resin, a (meth) acrylate resin (such as an alkyl (meth) acrylate resin and a dimethylaminoethyl (meth) acrylate resin), a butadiene resin, a styrene resin, a siloxane resin, and a copolymer thereof. . These resins can be used alone or in combination of two or more.

  In this specification, “(meth) acrylic acid” means at least one of “acrylic acid” and “methacrylic acid”, and “(meth) acrylate” means at least one of “acrylate” and “methacrylate”. means.

  Among these resins, from the viewpoint of storage stability and pattern forming properties, it is preferable to use a neutral resin having no acidic or basic functional group, and even if the content is small, the viscosity and viscosity can be easily adjusted. From the viewpoint of controlling the thixotropy, it is more preferable to use a cellulose derivative such as ethyl cellulose.

  The molecular weight of the resin is not particularly limited, and is preferably adjusted as appropriate in view of the desired viscosity of the protective layer forming composition. The weight average molecular weight of the resin is preferably from 100 to 10,000,000, and more preferably from 1,000 to 5,000,000, from the viewpoint of storage stability and pattern formability. The weight average molecular weight of the resin can be determined by converting the molecular weight distribution measured using GPC (gel permeation chromatography) using a standard polystyrene calibration curve. The calibration curve is approximated by a cubic equation using five sample sets of standard polystyrene (Tosoh Corporation, “PStQuick MP-H, PStQuick B” (trade name)). GPC measurement conditions are shown below.

Equipment: (pump: Hitachi High-Technologies Corporation, “L-2130”)
(Detector: Hitachi High-Technologies Corporation, "L-2490 type RI")
(Column oven: Hitachi High-Technologies Corporation, "L-2350")
Column: Hitachi Chemical Co., Ltd., "Gelpack GL-R440" + "Gelpack GL-R450" + "Gelpack GL-R400M" (3 in total; all are trade names)
Column size: 10.7mm (inner diameter) x 300mm
Eluent: Tetrahydrofuran Sample concentration: 10mg / 2mL
Injection volume: 200 μL
Flow rate: 2.05 mL / min Measurement temperature: 25 ° C

  The content of the resin in the composition for forming the passivation layer protective layer can be appropriately selected as needed. For example, the content of the resin is preferably 0.1% by mass to 30% by mass based on the total mass of the composition for forming a passivation layer protective layer. From the viewpoint of developing thixotropy that can further improve pattern formation, the content of the resin is more preferably 1% by mass to 25% by mass, and still more preferably 1.5% by mass to 20% by mass. , 1.5 mass% to 10 mass%.

  The content ratio of the compound represented by the general formula (I) and the resin in the composition for forming a protective layer of the present invention can be appropriately selected as necessary. From the viewpoint of pattern formability and storage stability, the content ratio of the resin (resin / compound represented by the general formula (I)) to the total amount of the compound represented by the general formula (I) is 0.001 to 1000. Preferably, it is 0.01 to 100, more preferably 0.1 to 1.

(Liquid medium)
The passivation layer-forming protective composition of the present invention preferably further contains a liquid medium. When the composition for forming a protective layer contains a liquid medium, it becomes easier to adjust the viscosity of the composition for forming a protective layer, the imparting property is further improved, and a uniform heat treatment layer can be formed. is there. The liquid medium is not particularly limited as long as it can dissolve or disperse the compound represented by the general formula (I), and can be appropriately selected as needed. The liquid medium refers to a solvent or a dispersion medium that is in a liquid state at room temperature (25 ° C.).

  Specific examples of the liquid medium include acetone, methyl ethyl ketone, methyl-n-propyl ketone, methyl isopropyl ketone, methyl-n-butyl ketone, methyl isobutyl ketone, methyl-n-pentyl ketone, methyl-n-hexyl ketone, diethyl ketone, Ketone solvents such as dipropyl ketone, diisobutyl ketone, trimethylnonanone, cyclohexanone, cyclopentanone, methylcyclohexanone, 2,4-pentanedione, acetonylacetone; diethyl ether, methyl ethyl ether, methyl-n-propyl ether, diisopropyl Ether, tetrahydrofuran, methyltetrahydrofuran, dioxane, dimethyldioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol Rudi-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, triethylene Glycolme -N-hexyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol methyl ethyl ether, tetraethylene glycol methyl-n-butyl ether, tetraethylene 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, dipropylene glycol Tyl-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, tetrapropylene glycol methyl ethyl ether, tetra Propylene glycol methyl-n-butyl ether, tetrapropylene glycol Ether solvents such as benzyl-n-butyl ether, tetrapropylene glycol methyl-n-hexyl ether and tetrapropylene glycol di-n-butyl ether; methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl 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 acetate, benzyl acetate, Cyclohexyl acetate, methylcyclohexyl acetate, nonyl acetate, methyl acetoacetate, ethyl acetoacetate, diethylene glycol methyl ether acetate, diethylene glycol monoethyl ether acetate, dipropylene glycol methyl ether acetate Dipropylene glycol ethyl ether acetate, glycol diacetate, methoxytriethylene glycol acetate, isoamyl acetate, ethyl propionate, n-butyl propionate, isoamyl propionate, diethyl oxalate, di-n-butyl oxalate, methyl lactate, lactic acid, lactic acid Ethyl, 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 glycol ethyl ether Ester solvents such as acetate, propylene glycol propyl ether acetate, γ-butyrolactone, γ-valerolactone; acetonitrile Ryl, N-methylpyrrolidinone, N-ethylpyrrolidinone, N-propylpyrrolidinone, N-butylpyrrolidinone, N-hexylpyrrolidinone, N-cyclohexylpyrrolidinone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide and the like Aprotic polar solvent; hydrophobic organic solvents such as methylene chloride, chloroform, dichloroethane, benzene, toluene, xylene, hexane, octane, ethylbenzene, 2-ethylhexanoic acid, methyl isobutyl ketone, methyl ethyl ketone; methanol, ethanol, n-propanol , Isopropanol, n-butanol, isobutanol, sec-butanol, t-butanol, n-pentanol, isopentanol, 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, cyclohexanol, methylcyclohexanol, isobornylcyclohexanol, benzyl alcohol, ethylene glycol, 1, Alcohol solvents such as 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- glycol monoether solvents such as n-butyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, tripropylene glycol monomethyl ether; terpinene, terpineol, myrcene, allocymene, limonene, dipentene, pinene, carvone, Oshimen, Terpene solvents such as Erandoren; and water. These liquid media are used alone or in combination of two or more.

  Among them, the liquid medium is composed of a hydrophobic organic solvent, an aprotic organic solvent, a terpene solvent, an ester solvent, an ether solvent, and an alcohol solvent, from the viewpoint of imparting the protective layer forming composition to the semiconductor substrate and forming a pattern. It preferably contains at least one selected from the group, more preferably contains at least one selected from the group consisting of terpene solvents, ester solvents and alcohol solvents, and at least one selected from the group consisting of terpene solvents. More preferably, it comprises a species.

  When the composition for forming a protective layer contains a liquid medium, the content of the liquid medium in the composition for forming a protective layer is determined in consideration of impartability, pattern formability, storage stability and the like. For example, the content of the liquid medium is preferably from 5% by mass to 98% by mass with respect to the total mass of the composition for forming a protective layer, from the viewpoint of imparting property and pattern formability of the composition for forming a protective layer. And more preferably 10% to 95% by mass.

(Other components)
The composition for forming a protective layer of the present invention may further include a plasticizer, a dispersant, a surfactant, a thixotropic agent, a filler, and the like, if desired. Above all, by including at least one selected from a thixotropic agent and a filler, the shape stability of the protective layer forming composition layer formed by applying the protective layer forming composition to the passivation layer is further improved. In addition, it becomes easy to selectively form a protective layer in a desired shape in a region where the composition layer for forming a protective layer is formed.

  Examples of the thixotropic agent include a fatty acid amide, a polyalkylene glycol compound, an organic filler, and an inorganic filler.

  Examples of the polyalkylene glycol compound include a compound represented by the following general formula (III).

In the formula (III), R ⁶ and R ⁷ each independently represent a hydrogen atom or an alkyl group, and R ⁸ represents an alkylene group. n is an arbitrary integer of 3 or more. In addition, a plurality of R ⁸ may be the same or different.

  Examples of the fatty acid amide include compounds represented by the following general formulas (1), (2), (3) and (4).

R ⁹ CONH ₂ (1)
R ⁹ CONH-R ¹⁰ -NHCOR ⁹ (2)
R ⁹ NHCO-R ¹⁰ -CONHR ⁹ (3)
R ⁹ CONH-R ¹⁰ -N (R ¹¹ ) ₂ (4)

Formula (1), (2), (3) and (4) in, ^{R 9} and ^{R 11} each independently represents an alkyl group or an alkenyl group having 2 to 30 carbon atoms having from 1 to 30 carbon ^{atoms, R 10} Represents an alkylene group having 1 to 10 carbon atoms. Two R ¹¹ may be the same or different.

  Examples of the organic filler include particles or fibrous materials composed of an acrylic resin, a cellulose resin, a polystyrene resin, and the like.

  Examples of the inorganic filler include particles of silicon dioxide, aluminum hydroxide, aluminum nitride, silicon nitride, aluminum oxide, zirconium oxide, silicon carbide, glass, and the like.

  When the organic filler and the inorganic filler are in the form of particles, the volume average particle diameter may be 0.01 μm to 50 μm. The volume average particle diameter of the organic filler and the inorganic filler can be measured by a laser diffraction scattering particle size distribution analyzer (for example, Beckman Coulter LS13320), and the value obtained by calculating the median diameter from the obtained particle size distribution is calculated as the average particle diameter. It can be. The average particle diameter can also be determined by observing using an SEM (scanning electron microscope).

(Physical properties)
The viscosity of the composition for forming a protective layer is not particularly limited, and can be appropriately selected according to the method of applying the composition to the semiconductor substrate. For example, the viscosity of the composition for forming a protective layer can be 0.01 Pa · s to 10000 Pa · s. Above all, from the viewpoint of pattern formability, the viscosity of the composition for forming a protective layer is preferably from 0.1 Pa · s to 1000 Pa · s. The viscosity is measured at 25 ° C. and a shear rate of 1.0 s ⁻¹ using a rotary shear viscometer.

The shear viscosity of the composition for forming a protective layer is not particularly limited, and it is preferable that the composition for forming a protective layer has thixotropic properties. Among them from the viewpoints of pattern formability, thixotropic ratio calculated by dividing the shear viscosity eta ₁ at shear viscosity eta ₂ at a shear rate of ^{10s -1} at a shear rate of ^{_{1.0s -1 (η 1 / η 2}} ) is 1. It is preferably from 0 to 10, more preferably from 2.0 to 6.0. The shear viscosity is measured at a temperature of 25 ° C. using a rotary shear viscometer equipped with a cone plate (diameter 50 mm, cone angle 1 °).

  The components contained in the composition for forming a passivation layer and the content of each component are determined by thermal analysis such as differential thermogravimetry (TG / DTA), nuclear magnetic resonance (NMR), infrared spectroscopy (IR). ) And chromatographic analysis such as high performance liquid chromatography (HPLC) and gel permeation chromatography (GPC).

(Production method of composition for forming passivation layer protective layer)
The method for producing the composition for forming a passivation layer protective layer is not particularly limited. For example, it can be produced by mixing a compound represented by the general formula (I), a resin, and other components contained as necessary by a commonly used mixing method.

<Solar cell element>
The solar cell element of the present invention is provided on at least one surface of a semiconductor substrate, and includes a passivation layer containing aluminum oxide, and the composition for forming a passivation layer protective layer of the present invention, which is provided on the passivation layer. A solar cell element comprising: a protective layer that is a heat-treated product of (1); and an electrode provided on a side of the semiconductor substrate on which the passivation layer and the protective layer are formed.
The solar cell element of the present invention may further have other components as necessary. The solar cell element of the present invention has excellent conversion efficiency by having the protective layer formed from the composition for forming a passivation layer protective layer of the present invention.

(Semiconductor substrate)
The semiconductor substrate is not particularly limited, and can be appropriately selected from those usually used depending on the purpose. Examples of the semiconductor substrate include those obtained by doping (diffusing) p-type impurities or n-type impurities into silicon, germanium, or the like. Among them, a silicon substrate is preferable. Further, the semiconductor substrate may be a p-type semiconductor substrate or an n-type semiconductor substrate. In particular, from the viewpoint of the passivation effect, it is preferable that the surface on which the passivation layer is formed be a semiconductor substrate in which the surface is a p-type layer. Even if the p-type layer on the semiconductor substrate is a p-type layer derived from the p-type semiconductor substrate, it is formed on the n-type semiconductor substrate or the p-type semiconductor substrate as a p-type diffusion layer or a p ⁺ -type diffusion layer. It may be something.

  Further, the thickness of the semiconductor substrate is not particularly limited, and can be appropriately selected depending on the purpose. For example, the thickness of the semiconductor substrate can be 50 μm to 1000 μm, and preferably 75 μm to 750 μm.

(Passivation layer)
The passivation layer in the present invention contains aluminum oxide. The passivation layer may be a heat-treated product of an aluminum oxide layer formed by an ALD method, a CVD method, a PECVD method, or the like, or a heat-treated product of a passivation layer-forming composition layer composed of a passivation layer-forming composition. Is also good. The composition for forming a passivation layer is not particularly limited as long as the heat-treated product contains aluminum oxide and can function as a passivation layer, and a known composition for forming a passivation layer can be used. From the viewpoint that a relatively thin passivation layer can be formed as described below, a heat treatment of an aluminum oxide layer formed by an ALD method, a CVD method, a PECVD method, or the like is preferable.

The thickness of the passivation layer is not particularly limited, and can be appropriately selected depending on the purpose. For example, the thickness is preferably 1 nm to 50 μm, more preferably 1 nm to 30 μm, and still more preferably 1 nm to 20 μm.
The passivation layer preferably has a thickness of 1 nm to 50 nm, and more preferably has a thickness of 2 nm to 40 nm from the viewpoint of easily forming an ohmic contact through the passivation layer when the passivation effect and the electrode forming paste are heat-treated. More preferably, the thickness is more preferably 3 nm to 30 nm from the viewpoint of obtaining a stable passivation effect.
Here, the thickness of the passivation layer is measured by an ordinary method using an interference type film thickness meter (for example, Filmetrics, “F20 film thickness measurement system”), an ellipsometer, or the like. It is calculated as an average value.

(Protective layer)
The protective layer is provided on the passivation layer and is a heat-treated product of the passivation layer protective layer forming composition of the present invention. Since the protective layer in the present invention is formed using the composition for forming a passivation layer protective layer of the present invention, it can be formed in a desired region in a desired pattern.
The shape of the protective layer is not particularly limited, and preferably has an opening pattern having an opening in a region where an electrode is formed. Examples of the shape of the opening include a stripe shape and a dot shape.

The thickness of the protective layer is not particularly limited, and is preferably 20 nm or more, more preferably 30 nm or more, and more preferably 40 nm or more, from the viewpoint of the resistance of the protective layer when the electrode forming paste is heat-treated. More preferred. From the viewpoint of suppressing the occurrence of cracks in a layer in which the electrode forming paste can be alloyed with the substrate, the thickness is preferably 500 nm or less, more preferably 400 nm or less, and more preferably 300 nm or less. More preferred.
Here, the thickness of the protective layer is measured by an ordinary method using an interference type film thickness meter (for example, Filmetrics, “F20 film thickness measurement system”), an ellipsometer, or the like, and the arithmetic operation is performed. It is calculated as an average value.

(electrode)
Examples of the electrode provided on the side on which the passivation layer and the protective layer are provided include an aluminum electrode and a silver electrode. The electrode is preferably an electrode formed using an electrode forming paste. The electrodes are preferably formed in openings of the protective layer formed in a pattern. The paste for forming an electrode is not particularly limited, and a known paste for forming an electrode can be used. It is preferable to use an aluminum paste from the viewpoint of easy reaction with a passivation layer.

<Method for manufacturing solar cell element>
The solar cell element of the present invention is a solar cell element manufactured by the following method for manufacturing a solar cell element of the present invention.
The method for manufacturing a solar cell element according to the present invention includes a step of forming a passivation layer containing aluminum oxide on at least one surface of a semiconductor substrate; and a method of forming a passivation layer protective layer according to the present invention on at least a part of the passivation layer. Forming a protective layer forming composition layer by applying the forming composition in a pattern, forming a protective layer by heat treatment, and forming the protective layer on the side where the passivation layer and the protective layer are formed on the semiconductor substrate. Providing an electrode. The method for manufacturing a solar cell element may further include other steps as necessary.
In the method for producing a solar cell element of the present invention, a solar cell element having excellent conversion efficiency can be produced by a simple method by using the composition for forming a passivation layer protective layer of the present invention.

(Passivation layer forming step)
The method for manufacturing a solar cell element of the present invention includes a step of forming a passivation layer containing aluminum oxide on at least one surface of a semiconductor substrate (hereinafter, also referred to as a “passivation layer forming step”).
The passivation layer containing aluminum oxide may be formed entirely on at least one surface of the semiconductor substrate, or may be formed in a pattern on at least a part of at least one surface of the semiconductor substrate.

  The method for forming the passivation layer is not particularly limited, and includes a method for forming a passivation layer by an ALD method, a CVD method, a PECVD method, etc., a method for forming a composition for forming a passivation layer by a screen printing method, an inkjet method, a roll coating method, and a blade coating method. And the like. From the viewpoint that it is easy to form a passivation layer on at least one surface of the semiconductor substrate, an ALD method, a CVD method, a PECVD method, or the like is preferable. From the viewpoint of easy formation of a patterned passivation layer, a screen printing method, an inkjet method, or the like is preferable.

In the case of forming a patterned passivation layer, for example, a composition for forming a patterned passivation layer is applied on at least one surface of a semiconductor substrate by a screen printing method, an inkjet method or the like. Is formed, and the composition layer is heat-treated to form a patterned passivation layer.
As another method, for example, a heat treatment is performed after forming a precursor layer of a passivation layer on at least one surface of a semiconductor substrate, and an opening pattern is formed on the heat-treated material using a laser or the like. Thereby, a patterned passivation layer can be formed. In this method, the precursor layer may be an aluminum oxide layer formed by an ALD method, a CVD method, a PECVD method or the like, and formed by applying a composition for forming a passivation layer by a printing method such as a roll coating method. The composition layer for forming a passivation layer may be used.
The method for forming the opening pattern is not particularly limited, and examples include laser irradiation and photolithography.

  When the passivation layer is formed on the entire surface of at least one surface of the semiconductor substrate, an ALD method, a CVD method, and the like, from the viewpoint that a thin passivation layer can be formed as compared with the case where the composition for forming a passivation layer is used. It is preferable to use a PECVD method or the like. In this case, the thickness of the passivation layer is preferably 50 nm or less. When the thickness of the passivation layer formed over the whole is 50 nm or less, the passivation layer and the electrode precursor react (fire-through) in the electrode forming step to form an ohmic contact, and the diffusion layer and the electrode are formed together. Can be formed.

The heat treatment method for forming the passivation layer is not particularly limited. The heat treatment temperature is preferably from 600C to 800C.
When the composition for forming a passivation layer is used, the composition may be dried after forming the composition layer for forming a passivation layer and before the heat treatment.

(Protective layer forming step)
The method for manufacturing a solar cell according to the present invention includes forming a protective layer forming composition layer by applying the passivation layer protective layer forming composition of the present invention to at least a part of the passivation layer in a pattern, and performing heat treatment. A step of forming a protective layer (hereinafter, also referred to as a “protective layer forming step”) is included.

The method of applying the composition for forming a passivation layer protective layer in a pattern is not particularly limited as long as the pattern-like passivation layer can be formed, and printing such as a screen printing method, an inkjet method, a roll coating method, and a blade coating method. Law. It is preferable that the electrode is formed to have a pattern having an opening in a region where the electrode is formed. Examples of the shape of the opening include a stripe shape and a dot shape. From the viewpoint that it is easy to form a desired pattern in a desired region, it is preferable that the application of the composition for forming a passivation layer protective layer is performed by a screen printing method or an inkjet method.
By forming an electrode on the semiconductor substrate exposed to the opening, the electrode and the semiconductor substrate can be electrically connected. In particular, when the passivation layer is formed by the ALD method or the like and has a relatively small thickness, when the electrode forming paste is applied to the passivation layer and heat treatment is performed, the electrode forming paste reacts with the passivation layer (fire through) and the passivation occurs. It becomes possible to form an ohmic contact directly with the semiconductor substrate through the layer, and it is possible to form the diffusion layer and the electrode collectively.

  After forming the protective layer forming composition layer and before heat-treating the protective layer forming composition layer, the method may further include a step of drying the protective layer forming composition layer. Drying conditions are not particularly limited.

  The method of heat treatment is not particularly limited, and a known heat treatment device or the like can be used. The heat treatment temperature is preferably from 300C to 900C, more preferably from 400C to 850C, and even more preferably from 500C to 830C. The heat treatment time is preferably from 3 minutes to 120 minutes, more preferably from 5 minutes to 90 minutes, even more preferably from 7 minutes to 60 minutes. The heat treatment can be performed in an air atmosphere.

(Electrode formation step)
The method for manufacturing a solar cell according to the present invention further includes a step of providing an electrode on a side of the semiconductor substrate on which the passivation layer and the protective layer are formed (hereinafter, also referred to as an “electrode forming step”).
The method for forming the electrode is not particularly limited, and includes, for example, a method in which an electrode forming paste is applied to the side on which the passivation layer and the protective layer are formed and heat-treated.
The method for applying the electrode forming paste is not particularly limited, and examples thereof include a screen printing method and a blade coating method.
The heat treatment method for forming the electrode is not particularly limited. The heat treatment temperature is preferably from 450C to 900C, more preferably from 500C to 850C. The heat treatment time is preferably 0.1 seconds to 60 seconds, more preferably 1 second to 30 seconds.

Next, an embodiment of a method for manufacturing a solar cell element of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view schematically showing a method for manufacturing a solar cell element according to one embodiment of the present invention. However, the method for manufacturing a solar cell element of the present invention is not limited to the embodiment shown in FIG.

  First, as shown in FIG. 1A, the p-type semiconductor substrate 1 is washed with an alkaline aqueous solution to remove organic substances, particles, and the like on the surface of the p-type semiconductor substrate 1. Thereby, the passivation effect is further improved. As a cleaning method using an alkaline aqueous solution, a method using RCA cleaning or the like generally known may be used. For example, by immersing the semiconductor substrate in a mixed solution of aqueous ammonia and aqueous hydrogen peroxide and treating it at 60 ° C. to 80 ° C., organic substances and particles can be removed, and the semiconductor substrate can be washed. The washing time is preferably from 10 seconds to 10 minutes, more preferably from 30 seconds to 5 minutes.

  Next, as shown in FIG. 1 (2), the surface of the p-type semiconductor substrate 1 is subjected to an alkali etching treatment or the like to form irregularities (hereinafter also referred to as “texture”) on the surface. This makes it possible to suppress the reflection of sunlight on the light receiving surface side of the solar cell element. For the alkali etching treatment, for example, an etching solution composed of NaOH and IPA (isopropanol) can be used.

Next, as shown in FIG. 1C, the n ⁺ -type diffusion layer 2 is formed with a thickness on the order of submicrons by thermally diffusing a donor element such as phosphorus into the surface of the p-type semiconductor substrate 1. Pn junction (not shown) is formed at the boundary with the p-type bulk portion.

As a technique for diffusing a donor element such as phosphorus, for example, a method of performing a heat treatment for several tens minutes at 800 ° C. to 1000 ° C. in a mixed gas atmosphere of phosphorus oxychloride (POCl ₃ ), nitrogen, and oxygen can be given. . In this method, since phosphorus is diffused using a mixed gas, as shown in FIG. 1 (3), the n ⁺ type diffusion layer 2 is formed not only on the light receiving surface (front surface) but also on the back surface and side surfaces (not shown). Is formed. A PSG (phosphosilicate glass) layer 3 is formed on the n ⁺ type diffusion layer 2. Therefore, side etching is performed to remove the PSG layer 3 and the n ⁺ -type diffusion layer 2 formed on the side surfaces.

Thereafter, as shown in FIG. 1D, the PSG layer 3 formed on the light receiving surface and the back surface is removed using an etching solution such as hydrofluoric acid. Further, as shown in FIG. 1 (5), the back surface is separately etched to remove the n ⁺ -type diffusion layer 2 on the back surface and planarize the back surface. As a method of flattening, a method of immersing the back surface of the p-type semiconductor substrate 1 in a mixed solution of nitric acid, hydrofluoric acid and acetic acid or a potassium hydroxide solution can be used.

Next, as shown in FIG. 1 (6), an antireflection film 4 made of silicon nitride or the like is formed on the n ⁺ -type diffusion layer 2 formed on the light receiving surface by a PECVD (Plasma Enhanced Chemical Vapor Deposition) method or the like. It is provided with a thickness of about 90 nm.

Next, as shown in FIG. 1 (7), after an aluminum oxide layer is formed on a part of the back surface by the ALD method, heat treatment (firing) is performed at a temperature of 600 ° C. to 800 ° C. to form a passivation layer made of aluminum oxide. 5 is formed.
Next, as shown in FIG. 1 (8), the composition for forming a passivation layer protective layer of the present invention is applied to a part of the surface of the passivation layer 5 in a pattern by a screen printing method or the like. After drying, heat treatment (firing) is performed at a temperature of 300 ° C. to 900 ° C. to form a patterned protective layer 6.

FIG. 4 is a schematic plan view showing an example of the pattern of the protective layer 6 on the back surface. FIG. 6 is an enlarged schematic plan view of part A in FIG. FIG. 7 is an enlarged schematic plan view of a portion B in FIG. In the case of the protective layer 6 shown in FIG. 4, as can be seen from FIGS. 6 and 7, the protective layer 6 on the back surface is formed through a linear opening except for a portion where the back surface output extraction electrode 8 is formed in a later step. The passivation layer 5 has an exposed pattern. The pattern of the linear openings is preferably defined by _a line width (L _a ) and a line interval (L _b ) and arranged regularly. The line width (L _a ) and the line interval (L _b ) can be set arbitrarily. In terms of recombination-inhibiting passivation effect and minority carriers, it is preferable that _{L a} is 20μm~2mm _{L b} is 10Myuemu～5mm, _{L a} is 30μm~1mm _{L b} is 40μm~3mm Is more preferable, and L _a is more preferably 40 μm to 0.5 mm and L _b is more preferably 50 μm to 2 mm.
The shape of the protective layer 6 on the back surface is not limited to the pattern shown in FIG. 4, but may have the pattern shown in FIG. FIG. 5 is a schematic plan view showing another example of the pattern of the protective layer 6, and FIG. 7 is a schematic plan view enlarging a portion B in FIG.

  Next, as shown in FIG. 1 (9), an electrode paste containing glass particles (light receiving surface current collecting electrode paste 9 or light receiving surface output extraction electrode paste 10) is applied to the light receiving surface by a screen printing method or the like. . FIG. 3 is a schematic plan view showing an example of the light receiving surface of the solar cell element of the present invention. As shown in FIG. 3, the light receiving surface electrode includes a light receiving surface current collecting electrode 9 and a light receiving surface output extraction electrode 10. In order to secure a light receiving area, it is necessary to keep the formation area of these light receiving surface electrodes small. In addition, from the viewpoint of the resistivity of the light receiving surface electrode and the productivity, it is preferable that the width of the light receiving surface current collecting electrode 9 is 10 μm to 250 μm, and the width of the light receiving surface output extraction electrode 10 is 100 μm to 2 mm. Further, in FIG. 3, two light receiving surface output extraction electrodes 10 are provided, but from the viewpoint of minority carrier extraction efficiency (power generation efficiency), the number of light reception surface output extraction electrodes 10 may be three or four. it can.

  On the other hand, as shown in FIG. 1 (9), on the back surface, an aluminum electrode paste containing glass powder (back-side current collecting electrode paste 7) and a silver electrode paste containing glass particles (back-side output extraction electrode paste 8) are provided. It is provided by a screen printing method or the like. FIG. 8 is a schematic plan view illustrating an example of the back surface of the solar cell element. The width of the back surface output extraction electrode 8 is not particularly limited, and the width of the back surface output extraction electrode 8 is preferably 100 μm to 10 mm from the viewpoint of connectivity of a wiring material in a later solar cell manufacturing process. .

  After applying the electrode paste to each of the light receiving surface and the back surface, drying and heat-treating (baking) the light receiving surface and the back surface at a temperature of about 450 ° C. to 900 ° C. in the air to collect light on the light receiving surface. The electrode 9 and the light receiving surface output extraction electrode 10 are formed, and the back surface current collecting electrode 7 and the back surface output extraction electrode 8 are formed on the back surface, respectively.

After the heat treatment (firing), as shown in FIG. 1 (10), on the light receiving surface, the glass particles contained in the silver electrode paste forming the light receiving surface electrode react with the antireflection film 4 (fire through), The light receiving surface electrodes (light receiving surface current collecting electrode 9 and light receiving surface output extraction electrode 10) are electrically connected to n ⁺ type diffusion layer 2 (formation of ohmic contact). On the other hand, on the back surface, in the openings where the passivation layer 5 was exposed in a line shape in FIGS. 6 and 7 (portions where the protective layer 6 was not formed), the aluminum in the aluminum electrode paste was subjected to heat treatment (firing). By forming an ohmic contact by fire-through with the aluminum oxide contained in 5 and diffusing it into the semiconductor substrate 1, the p ⁺ -type diffusion layer 11 is formed.

  As another embodiment different from FIG. 1, after FIG. 1 (6), a protective layer 6 may be provided after a patterned passivation layer 5 is formed as shown in FIG. FIG. 2 is a cross-sectional view schematically showing an example of a method for manufacturing a solar cell element according to another embodiment different from FIG. 1, and has the same steps as FIG. 1 up to FIG. In the embodiment shown in FIG. 2, the antireflection film 4 is formed as shown in FIG. 1 (6), and then the patterned passivation layer 5 is formed as shown in FIG. 2 (7). The method for forming the passivation layer 5 is not particularly limited, and the passivation layer 5 may be formed by applying a composition for forming a passivation layer in a pattern and heat-treating the composition layer. As another method, the aluminum oxide layer formed by the ALD method may be heat-treated and then patterned by laser irradiation or the like.

  Next, as shown in FIG. 2 (8), the composition for forming a passivation layer protective layer of the present invention is applied on the surface of the patterned passivation layer 5 by a screen printing method or the like so as to overlap the pattern of the passivation layer 5. It is applied in a pattern. After drying, heat treatment (firing) is performed at a temperature of 300 ° C. to 900 ° C. to form a patterned protective layer 6.

Next, as shown in FIG. 2 (9), an electrode paste containing glass particles (light receiving surface current collecting electrode paste 9 or light receiving surface output extraction electrode paste 10) is applied to the light receiving surface by screen printing or the like.
On the other hand, as shown in FIG. 2 (9), on the back surface, an aluminum electrode paste containing glass powder (backside current collecting electrode paste 7) and a silver electrode paste containing glass particles (backside output extraction electrode paste 8) are provided. It is provided by a screen printing method or the like. After applying the electrode paste to each of the light receiving surface and the back surface, drying and heat-treating (baking) the light receiving surface and the back surface at a temperature of about 450 ° C. to 900 ° C. in the air to collect light on the light receiving surface. The electrode 9 and the light receiving surface output extraction electrode 10 are formed, and the back surface current collecting electrode 7 and the back surface output extraction electrode 8 are formed on the back surface, respectively.

After the heat treatment (firing), as shown in FIG. 2 (10), on the light-receiving surface, the glass particles contained in the silver electrode paste forming the light-receiving surface electrode react with the antireflection film 4 (fire through). The light receiving surface electrodes (light receiving surface current collecting electrode 9 and light receiving surface output extraction electrode 10) are electrically connected to n ⁺ type diffusion layer 2 (formation of ohmic contact). On the other hand, on the back surface, in the opening where the semiconductor substrate 1 is exposed (the portion where the protective layer 6 is not formed), the heat treatment (firing) causes the glass particles in the aluminum electrode paste and the passivation layer 5 to fire through and form an ohmic contact. By forming a contact and diffusing it into the semiconductor substrate 1, the p ⁺ type diffusion layer 11 is formed.

  In the method for manufacturing a solar cell element of the present invention, by using the composition for forming a passivation layer protective layer of the present invention having excellent pattern formability, a protective layer having excellent resistance to heat treatment of an electrode forming paste can be easily formed. A solar cell element that can be formed by a technique and has excellent power generation performance can be manufactured.

<Solar cells>
The solar cell of the present invention includes at least one of the solar cell elements of the present invention, and is configured by disposing a wiring material on an electrode of the solar cell element. That is, a solar cell of the present invention includes the solar cell element of the present invention and a wiring material disposed on an electrode of the solar cell element.
The solar cell of the present invention may be configured such that a plurality of solar cell elements are connected via a wiring material, if necessary, and further sealed with a sealing material. The wiring material and the sealing material are not particularly limited, and can be appropriately selected from those commonly used in the art.

  FIG. 9 is a diagram illustrating an example of a method for manufacturing a solar cell according to the present invention. For example, as shown in FIG. 9, the solar cell of the present invention is formed by laminating a glass plate 16, a sealing material 14, a solar cell element 12 to which a wiring material 13 is connected, a sealing material 14, and a back sheet 15 in this order. This laminate is vacuum laminated at a temperature of 140 ° C. for 5 minutes using a vacuum laminator (for example, NMC Corporation, “LM-50 × 50-S”) so that a part of the wiring member is exposed. It can be manufactured by doing.

  Hereinafter, the present invention will be described specifically with reference to examples. However, the present invention is not limited to these examples. Unless otherwise specified, “%” is based on mass.

<Example 1>
(Preparation of composition for forming protective layer)
41.9 g of ethyl cellulose and 377.1 g of terpineol were mixed and stirred at 150 ° C. for 1 hour to prepare a 10% ethyl cellulose solution. Separately, 22.6 g of aluminum ethyl acetoacetate diisopropylate (Kawaken Fine Chemical Co., Ltd., “ALCH” (trade name)) and 37.5 g of terpineol were mixed. By mixing this mixed solution with 98.7 g of the above 10% ethyl cellulose solution, a composition for forming a protective layer which was a colorless and transparent solution was produced.
The content of ethyl cellulose in the composition for forming a protective layer was 6.2% by mass, and the content of aluminum ethyl acetoacetate diisopropylate was 14.2% by mass.

(Production of solar cell element)
A single crystal p-type semiconductor substrate (156 mm square, 200 μm thick) was subjected to alkali etching treatment to form a texture structure on each of the light receiving surface and the back surface. Next, this single-crystal p-type semiconductor substrate is heat-treated at 900 ° C. for 20 minutes in a mixed gas atmosphere of phosphorus oxychloride (POCl ₃ ), nitrogen and oxygen, and the light-receiving surface, the back surface, and the side surface of the single-crystal p-type semiconductor substrate are formed. An n ⁺ type diffusion layer was formed. Thereafter, side etching was performed to remove the phosphorus silicate glass (PSG) layer and the n ⁺ -type diffusion layer formed on the side surfaces. Further, the PSG layer formed on the light receiving surface and the back surface was removed using an etching solution containing hydrofluoric acid. Next, an antireflection film made of silicon nitride was formed to a thickness of about 90 nm on the n ⁺ -type diffusion layer formed on the light receiving surface by PECVD. Further, the back surface was separately etched to remove the n ⁺ -type diffusion layer on the back surface and planarized.

Next, an aluminum oxide layer having a thickness of about 20 nm was formed on the back surface from which the n ⁺ -type diffusion layer was removed by ALD, and heat-treated at 700 ° C. for 20 minutes. After the heat treatment, the same opening pattern as that of the protective layer 6 shown in FIGS. 4, 6, and 7 was formed on the aluminum oxide layer using a laser device, and the passivation layer 5 was formed. The line width (L _a ) in FIGS. 6 and 7 was 100 μm, and the line interval (L _b ) was 1.8 mm.

Next, the composition for forming a protective layer prepared above was applied onto the above-mentioned passivation layer 5 by a screen printing method so as to have the opening patterns shown in FIGS. 4, 6 and 7. After that, it is dried at 150 ° C. for 5 minutes, and heat-treated (fired) using a diffusion furnace (Koyo Thermo System Co., Ltd., “260A-M100”) under the conditions of an air atmosphere at a maximum temperature of 700 ° C. and a holding time of 10 minutes. ) To form a protective layer 6 having a thickness of about 150 nm. The protective layer 6 had the shape shown in FIGS. 4, 6, and 7, the line width (L _a ) of the opening pattern was 100 μm, and the line interval (L _b ) was 1.8 mm.

  Next, a commercially available silver electrode paste (DuPont, "PV-16A") was printed on the light receiving surface in a pattern shown in FIG. 3 by a screen printing method. The electrode pattern is composed of a light-receiving surface current collecting electrode 9 having a width of 120 μm and a light-receiving surface output extraction electrode 10 having a width of 1.5 mm. The printing conditions (screening) are such that the thickness after heat treatment (firing) is 20 μm. The plate mesh, printing speed and printing pressure) were adjusted as appropriate. This was heat-treated at a temperature of 150 ° C. for 5 minutes, and a drying treatment was performed by scattering a liquid medium.

  On the other hand, a commercially available aluminum electrode paste (PVG-AD-02) and a commercially available silver electrode paste (Dupont, PV-505) are screen-printed on the back surface. Printing was performed in the pattern shown in FIG. 8 to produce a back surface current collecting electrode 7 as an aluminum electrode and a back surface output extraction electrode 8 as a silver electrode. The size of each of the back surface output extraction electrodes 8 was 123 mm × 4 mm.

The printing conditions of the aluminum electrode paste and the silver electrode paste (mesh of screen plate, printing speed and printing) were set so that the thickness of the back surface current collecting electrode 7 and the back surface output extraction electrode 8 after the heat treatment (firing) was 20 μm, respectively. Pressure) was adjusted appropriately.
After printing each electrode paste, it was heated at a temperature of 150 ° C. for 5 minutes, and a drying treatment was performed by scattering a liquid medium.

  Subsequently, a heat treatment (firing) was performed using a tunnel furnace (Noritake Co., Ltd., “Single-row W / B tunnel furnace”) under the conditions of an air atmosphere at a maximum temperature of 800 ° C. and a holding time of 10 seconds. Thus, a solar cell element on which a desired electrode was formed was manufactured.

(Production of solar cell)
Wiring member 13 (solder-plated rectangular wire for solar cell, Hitachi Metals, Ltd., "SSA-") is provided on light-receiving surface output extraction electrode 10 and back surface output extraction electrode 8 of the solar cell element of Example 1 obtained above. TPS ”, 0.2 x 1.5 (20), specification of Sn-Ag-Cu-based lead-free solder plated on a copper wire 0.2 mm thick x 1.5 mm wide with a maximum thickness of 20 µm per side) Then, using a tab wire connection device (NPC, “NTS-150-M Tabbing & Stringing Machine”), the solder is melted under the conditions of a maximum temperature of 250 ° C. and a holding time of 10 seconds, so that the above-mentioned wiring member is obtained. 13 and the light receiving surface output extraction electrode 10 and the back surface output extraction electrode 8 were connected.

  Then, using a glass plate (Asahi Glass Co., Ltd., “3KWE33” (white plate reinforced glass)), a sealing material (ethylene vinyl acetate; EVA) and a back sheet, as shown in FIG. The solar cell element 12 to which the material 14 and the wiring material 13 are connected, the sealing material 14 and the back sheet 15 are laminated in this order, and the laminated body is vacuum-laminated (LM-50 × 50-S )), And vacuum-laminated at a temperature of 140 ° C. for 5 minutes to expose a part of the wiring member, thereby producing a solar cell.

  The evaluation of the power generation performance of the manufactured solar cell of Example 1 was performed by using a simulated sunlight (“WXS-155S-10”) and a voltage-current (IV) evaluator (Eiko Seiki) Co., Ltd., "IV CURVE TRACER MP-180"). Jsc (short circuit current density), Voc (open circuit voltage), and F.C. F. (Shape factor) and Eff (conversion efficiency) were obtained by measuring in accordance with JIS C8913 (2005) and JIS C8914 (2005), respectively. Tables 1 and 2 show the results.

<Comparative Example 1>
A solar cell was produced and evaluated in the same manner as in Example 1 except that the protective layer was not formed in Example 1. Tables 1 and 2 show the results.

<Reference Example 1>
After forming the passivation layer 5 in Example 1, instead of using the composition for forming a protective layer to form the protective layer 6, a protective layer made of silicon nitride (SiNx) was formed. Similarly, a solar cell was prepared and evaluated. Specifically, after forming the passivation layer 5 in the same manner as in Example 1, a silicon nitride (SiNx) layer is formed to a thickness of about 200 nm by PECVD, and the silicon nitride layer is formed on the silicon nitride layer by using a laser device as shown in FIGS. The protective layer was formed by forming the same opening pattern as that of the protective layer 6 shown in FIG. The line width (L _a ) in FIGS. 6 and 7 was 100 μm, and the line interval (L _b ) was 1.8 mm. Tables 1 and 2 show the results.

  As described above, the solar cell of Example 1 was superior in conversion efficiency as compared with Comparative Example 1 in which the protective layer was not provided.

REFERENCE SIGNS LIST 1 p-type semiconductor substrate 2 n ⁺ type diffusion layer 3 PSG (phosphosilicate glass) layer 4 antireflection film 5 passivation layer 6 protective layer 7 back surface current collecting electrode paste or back surface current collecting electrode 8 back surface output extraction electrode paste or back surface Output extraction electrode 9 Light receiving surface current collecting electrode paste or light receiving surface current collecting electrode 10 Light receiving surface output extracting electrode paste or light receiving surface output extracting electrode 11 p + type diffusion layer 12 solar cell element 13 wiring member 14 sealing material 15 back sheet 16 Glass plate

Claims (5)

Forming an aluminum oxide layer on at least one surface of the semiconductor substrate, and then performing a heat treatment at 600 ° C. to 800 ° C. to form a passivation layer containing aluminum oxide;
At least a portion of the passivation layer, and the step of imparting the path Sshibeshon layer protective layer forming composition in a pattern to form a protective layer-forming composition layer, to form a protective layer by heat treatment,
Providing an electrode on the side of the semiconductor substrate on which the passivation layer and the protective layer are formed,
Only including,
The method for producing a solar cell element, wherein the composition for forming a passivation layer protective layer contains a compound represented by the following general formula (I) and a resin .


[In the general formula (I), R ² each independently represents an alkyl group. n represents an integer of 1 to 3. X ² and X ³ each independently represent an oxygen atom or a methylene group. R ³ , R ⁴ and R ⁵ each independently represent a hydrogen atom or an alkyl group. ] 2. The solar cell according to claim 1, wherein a content of the compound represented by the general formula (I) is 0.1% by mass to 80% by mass with respect to a total mass of the composition for forming a passivation layer protective layer. Device manufacturing method. The method for producing a solar cell element according to claim 1, wherein a content of the resin is 0.1% by mass to 30% by mass with respect to a total mass of the composition for forming a passivation layer protective layer. The method for manufacturing a solar cell element according to claim 1, wherein the aluminum oxide layer is formed by an atomic layer deposition method. The method for producing a solar cell element according to any one of claims 1 to 4, wherein the application of the composition for forming a passivation layer protective layer is performed by a screen printing method or an inkjet method.