JP2015153897A - Composition for p-type diffusion layer formation, and method for manufacturing solar battery element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a composition for p-type diffusion layer formation which enables the realization of a long life time of a substrate after a diffusion process; and a method for manufacturing a solar battery element.SOLUTION: A composition for p-type diffusion layer formation comprises: a compound including an acceptor element; a barium compound; and a dispersant. A composition for p-type diffusion layer formation comprises: a compound including an acceptor element; and a dispersant; in the composition, the compound including the acceptor element includes a barium compound.

Description

  The present invention relates to a p-type diffusion layer forming composition and a method for producing a solar cell element.

The manufacturing process of the conventional silicon solar cell element is demonstrated.
First, a p-type silicon substrate having a texture structure formed on the light-receiving surface side is prepared so as to promote the light confinement effect and increase the efficiency, and then in a mixed gas atmosphere of phosphorus oxychloride (POCl ₃ ), nitrogen and oxygen A treatment for several tens of minutes is performed at 800 ° C. to 900 ° C. to uniformly form an n-type diffusion layer on the surface of the p-type silicon substrate. In this conventional method, since phosphorus is diffused using a mixed gas, n-type diffusion layers are formed not only on the light receiving surface but also on the side surface and the back surface. Therefore, side etching is performed to remove the n-type diffusion layer formed on the side surface. In addition, the n-type diffusion layer formed on the back surface needs to be converted to a p ⁺ -type diffusion layer. Aluminum paste is printed on the back surface and heat-treated (fired) to convert the n-type diffusion layer into the p ⁺ -type diffusion layer. Layering and obtaining ohmic contact are performed together.

  However, the electrical conductivity of the aluminum electrode formed from the aluminum paste is low. Therefore, in order to lower the sheet resistance, the aluminum layer formed on the entire back surface must usually have a thickness of about 10 μm to 20 μm after heat treatment (firing). Furthermore, since the coefficient of thermal expansion differs greatly between silicon and aluminum, a large internal stress is generated in the silicon substrate in the process of heat treatment (firing) and cooling, resulting in damage to crystal grain boundaries, increase in crystal defects, and warpage. Cause.

In order to solve this problem, there is a method of reducing the amount of aluminum paste applied and thinning the back electrode layer. However, if the amount of aluminum paste applied is reduced, the amount of aluminum diffusing from the surface of the p-type silicon substrate to the inside becomes insufficient. As a result, the desired BSF (Back Surface Field) effect (the effect of improving the collection efficiency of the generated carriers due to the presence of the p ⁺ -type diffusion layer) is not sufficient, resulting in a problem that the characteristics of the solar cell are deteriorated.

The p-type diffusion layer can also be diffused using BBr ₃ gas. However, in order to form the p-type diffusion layer in a position-selective manner, if the p-type diffusion layer is formed only in the applied portion, the patterning of the diffusion layer is performed. (For example, refer to Patent Document 1).

  Further, after diffusion of phosphorus and boron to form a diffusion layer, heat treatment is performed at a temperature lower than the diffusion temperature (for example, 600 to 800 ° C.) to getter harmful impurities such as heavy metals, thereby increasing the lifetime of carriers in the substrate. There is known a method of lengthening (hereinafter also referred to as lifetime) (for example, see Patent Document 2).

  In addition, it has been reported that a harmful impurity such as heavy metal contained in the substrate is gettered to the boron silicide layer, thereby extending the lifetime.

  The presence of the boron silicide layer hinders the passivation process and increases resistance in ohmic contact with the electrode, and thus needs to be removed, but is insoluble in hydrofluoric acid. The boron silicide layer can be oxidized and then etched with hydrofluoric acid. However, it is known that the impurities gettered in the boron silicide layer are re-diffused into the substrate in the process of oxidation at a high temperature of 800 ° C. or higher, and the low temperature of 600 ° C. or lower in an oxygen plasma or ultraviolet irradiation ozone atmosphere. There has been proposed a method in which etching is removed after oxidation with (see, for example, Patent Document 3).

JP 2013-77804 A JP 2011-166021 A Japanese Patent Laid-Open No. 10-172913

  However, in the methods of Patent Document 2 and Patent Document 3, after diffusion, boron silicate glass, which is a diffusion source of boron, is removed by etching with hydrofluoric acid and the like, and then a heat treatment step and a boron silicide removal step are required. The increase in the number leads to an increase in the manufacturing cost of the solar cell. Further, the inventors have found that the gettering effect by the low-temperature heat treatment in Patent Document 2 is not so great in improving the lifetime. Further, it has been found from the results of further examination by the present inventors that the boron silicide oxidation method using plasma or ozone of Patent Document 3 cannot completely suppress the re-diffusion of the impurity element into the substrate.

  This invention makes it a subject to provide the manufacturing method of the p-type diffused layer formation composition which can implement | achieve the long lifetime of the board | substrate after a diffusion process, and the increase in the number of processes, and a solar cell element.

  Means for solving the above problems are as follows.

<1> A p-type diffusion layer forming composition containing a compound containing an acceptor element, a barium compound, and a dispersion medium.

<2> A p-type diffusion layer forming composition containing a compound containing an acceptor element and a dispersion medium, wherein the compound containing the acceptor element contains barium.

<3> The p-type diffusion layer forming composition according to <1> or <2>, wherein the acceptor element is boron.

<4> The p-type diffusion layer formation according to any one of <1> to <3>, wherein the acceptor element-containing compound is at least one boron compound selected from boric acid, boric acid ester, and B ₂ O _3. Composition.

<5> The p-type diffusion layer forming composition according to any one of <1> to <4>, wherein the compound containing the acceptor element is a glass compound.

<6> At least one glass component selected from Al ₂ O ₃ , SiO ₂ , K ₂ O, Na ₂ O, Li ₂ O, SrO, CaO, MgO, BeO, ZnO and ZrO ₂ is further contained. The p-type diffusion layer forming composition according to the above <5>, comprising glass.

<7> The p-type diffusion layer forming composition according to any one of <1> to <6>, wherein the barium compound is at least one selected from BaO, BaSO ₄ , BaCO ₃ , and Ba (OH) ₂ .

<8> The p-type diffusion layer according to any one of <1> to <7>, wherein a ratio of the barium compound contained in the p-type diffusion layer forming composition is 0.01% by mass or more and 50% by mass or less. Forming composition.

<9> The p-type diffusion layer according to any one of <1> to <8>, wherein a ratio of the barium compound contained in the p-type diffusion layer forming composition is 0.05% by mass or more and 30% by mass or less. Forming composition.

<10> The p-type diffusion layer according to any one of <1> to <9>, wherein the proportion of the barium compound contained in the p-type diffusion layer forming composition is 0.1% by mass or more and 10% by mass or less. Forming composition.

<11> A step of applying the p-type diffusion layer forming composition according to any one of <1> to <10> on a semiconductor substrate;
Applying a thermal diffusion treatment to form a p-type diffusion layer;
The manufacturing method of the solar cell element which has this.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the manufacturing method of the p-type diffused layer formation composition which can implement | achieve the long lifetime of the board | substrate after a diffusion process, and a solar cell element.

It is sectional drawing which shows typically an example of the manufacturing method of a solar cell element. It is sectional drawing which shows the other example of the manufacturing method of a solar cell element typically.

  In this specification, the term “process” is not limited to an independent process, and is included in the term if the intended purpose of the process is achieved even when it cannot be clearly distinguished from other processes. . Moreover, the numerical range shown using "to" shows the range which includes the numerical value described before and behind "to" as a minimum value and a maximum value, respectively. Furthermore, the amount of each component in the composition means the total amount of the plurality of substances present in the composition unless there is a specific notice when there are a plurality of substances corresponding to each component in the composition. In the present specification, “content ratio” represents mass% of each component when the total amount of the p-type diffusion layer forming composition is 100 mass% unless otherwise specified. In addition, in the present specification, the term “layer” includes a configuration of a shape formed in part in addition to a configuration of a shape formed on the entire surface when observed as a plan view.

  The p-type diffusion layer forming composition of this embodiment contains a compound containing an acceptor element, a barium compound, and a dispersion medium.

  Here, the p-type diffusion layer forming composition contains a compound containing an acceptor element, and after being applied to the semiconductor substrate, the acceptor element in the compound containing the acceptor element is thermally diffused into the semiconductor substrate to cause impurities in the semiconductor substrate. A material capable of forming a diffusion layer.

  The p-type diffusion layer forming composition of the present embodiment tends to increase the lifetime of the substrate in which the acceptor element is diffused by including a barium compound. Although the detailed mechanism is unknown, it is considered that the barium compound has a function of taking in an impurity metal such as iron, that is, gettering. On the other hand, an impurity metal such as iron is not preferable because it has a high diffusion rate into the semiconductor substrate and acts as a carrier recombination center if it exists in the substrate. Since the p-type diffusion layer forming composition itself has a gettering function, the impurity metal contained in the p-type diffusion layer forming composition is prevented from diffusing into the semiconductor substrate, and the impurity metal in the substrate is also gettered. It is thought to be ringed. Based on such a mechanism, the lifetime may be improved.

(Barium compound)
The barium compound is not particularly limited as long as it is a compound containing barium. As barium compounds, barium oxide, barium carbonate, barium sulfate, barium hydroxide, barium peroxide, barium bromide, barium sulfide, barium silicide, barium boride, barium nitrate, barium iodide, barium oxalate, barium fluoride, BaCl ₂ barium chloride, barium nitride, dimethoxy barium, diethoxy barium, di -i- propoxy barium, di -n- propoxy barium, di -i- butoxy barium, di -n- butoxy barium, di -sec- butoxy barium, di -T-Butoxybarium, bis (dipivaloylmethanato) barium, barium aluminate, barium ferrite, barium molybdate, barium selenite, barium niobate, barium chromate, barium titanate, barium tungstate, zirconate Ba Examples thereof include barium and barium stannate. Among these, it is preferable to contain barium oxide.

  Although there is no restriction | limiting in particular in the form of a barium compound, It is preferable that they are a barium compound particle or the particle | grains which contain a barium compound as one component.

  Although there is no restriction | limiting in particular in the barium compound in a p-type diffused layer formation composition, It is preferable that the ratio of a barium compound is 0.01 mass% or more and 50 mass% or less, and 0.05 mass% or more and 30 mass% or less. More preferably, it is 0.1 to 10% by mass. By including 0.01% by mass or more, a lifetime improvement effect is obtained, and when it is 50% by mass or less, characteristics as a p-type diffusion layer forming composition, for example, viscosity, without inhibiting the diffusion of the acceptor element. It will be easier to adjust.

(Compound containing acceptor element)
An acceptor element is an element that can form a p-type diffusion layer by diffusing into a semiconductor substrate. As the acceptor element, a Group 13 element can be used, and from the viewpoint of safety and the like, it is preferable to contain at least one of B (boron) and Al (aluminum).

There is no restriction | limiting in particular as a compound containing an acceptor element. As a metal oxide containing an acceptor element, an oxide of a single acceptor element such as B ₂ O ₃ or Al ₂ O ₃ ; a glass component substance is formed in addition to an acceptor element-containing substance such as B ₂ O ₃ or Al ₂ O ₃ Glass compounds as components (hereinafter also referred to as acceptor element-containing glass particles); boron, aluminum-doped silicon particles, boron nitride (BN), calcium borate, boric acid and other inorganic boron compounds; boron-containing silicon oxide compounds And organoaluminum compounds such as aluminum alkoxide and alkylaluminum.

Among these, boric acid, boric acid ester, BN, B ₂ O ₃ , glass particles containing an acceptor element, a boron-containing silicon oxide compound, and B ₂ O ₃ at a high temperature (for example, 800 ° C. or more) thermally diffusing into a semiconductor substrate. It is preferable to use one or more selected from the group consisting of compounds (for example, boric acid) that can be changed into the compounds to be contained. More preferably, glass particles are used.

  The compound containing an acceptor element is preferably BN particles, glass particles containing an acceptor element, or a boron-containing silicon oxide compound, and more preferably glass particles containing a BN particle or an acceptor element. By using glass particles or BN particles containing an acceptor element, out-diffusion (the acceptor element diffuses in addition to the coating part) tends to be suppressed, and is unnecessary except in the region to which the p-type diffusion layer forming composition is applied. Formation of the p-type diffusion layer can be suppressed. That is, a p-type diffusion layer can be formed in a more selective region by including glass particles or BN particles containing an acceptor element.

The glass particles containing an acceptor element can be formed including, for example, an acceptor element-containing substance and a glass component substance. The acceptor element-containing material used for introducing the acceptor element into the glass particles is preferably a compound containing at least one selected from the group consisting of B ₂ O ₃ and Al ₂ O ₃ .

  The content rate of the acceptor element-containing substance in the glass particles containing the acceptor element is not particularly limited. For example, from the viewpoint of acceptor element diffusivity, it is preferably 0.5% by mass or more and 100% by mass or less, and more preferably 2% by mass or more and 80% by mass or less.

Furthermore, from the viewpoint of acceptor element diffusibility, 0.5 mass of one or more selected from the group consisting of B ₂ O ₃ and Al ₂ O ₃ as the acceptor element-containing substance is contained in the p-type diffusion layer forming composition. % Or more and 100% by mass or less, preferably 5% by mass or more and 99% by mass or less, more preferably 30% by mass or more and 80% by mass or less.

When the compound containing the acceptor element is a glass particle, examples of the glass component substance include SiO ₂ , K ₂ O, Na ₂ O, Li ₂ O, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, and V ₂ O. ₅ , SnO, ZrO ₂ , WO ₃ , MoO ₃ , Y ₂ O ₃ , CsO ₂ , TiO ₂ , TeO ₂ , La ₂ O ₃ , Nb ₂ O ₅ , Ta ₂ O ₅ , GeO ₂ , Lu ₂ O ₃ and It is preferable to use at least one selected from the group consisting of MnO, 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,} MoO 3, GeO 2, Y 2 O 3, CsO 2 and more favorable is the use of at least one selected from the group consisting of TiO ₂ Selection _{properly, SiO 2, K 2 O,} Na 2 O, Li 2 O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, V 2 O 5, SnO, from the group consisting of ZrO ₂ and MoO ₃ It is more preferable to use at least one selected from the viewpoints of setting the softening point within the specified range and reducing the coefficient of thermal expansion of the semiconductor substrate and the difference therebetween.

Specific examples of the glass particles include glass particles containing both the acceptor element-containing substance and the glass component substance, and are described in the order of B ₂ O ₃ —SiO ₂ (acceptor element-containing substance-glass component substance, hereinafter The same), B ₂ O ₃ —ZnO system, B ₂ O ₃ —PbO system, B ₂ O ₃ single system, and other acceptor element-containing materials including B ₂ O ₃ , Al ₂ O ₃ —SiO ₂ system, etc. Examples of the acceptor element-containing material include glass particles such as a system containing Al ₂ O ₃ .
In the above it has been illustrated glass particles containing one or _{two-component,} B ₂ O ₃ -SiO 2 -CaO-based, etc., may be glass particles containing more than three components.
_Also, as in the Al _{2 O 3 -B 2} O 3 system or the like, it may be glass particles containing two or more acceptor element-containing material.

Moreover, the barium compound may be included as a structural component of glass, and it is preferable to include as BaO. The BaO component acts as a lifetime improving component while affecting the glass properties as a network-modifying oxide.
The glass particles containing a barium compound as a constituent of the _glass, B ₂ O 3 _-BaO-based, B ₂ O ₃ -SiO _{2 -BaO-based, B 2 O 3 -SiO 2 -CaO} -BaO _based, B 2 _{O 3} -SiO ₂ -Al ₂ O _{3 -BaO-based, B 2 O 3 -SiO 2 -Al} 2 O 3 -CaO-BaO based to can be exemplified.

Moreover, you may mix and use the acceptor element containing glass particle which does not contain a barium component, and the acceptor element containing glass particle containing a barium component. Moreover, you may mix and use the acceptor element containing glass particle which does not contain a barium component, and the glass particle which contains a barium component but does not contain an acceptor element. _{Specifically,} B ₂ O ₃ -SiO ₂ -CaO-based glass _particles, and methods of using B ₂ O ₃ by mixing -SiO 2 -BaO-based glass _particles, B ₂ O ₃ -SiO ₂ -CaO-based A method of mixing and using glass particles and SiO ₂ —BaO glass particles can be exemplified.
Although there is no restriction | limiting in particular in the method of mixing, It can mix by methods, such as a mortar, a ball mill, a jet mill, a bead mill, a kneader, a V blender, a homogenizer, a rocking mill, a vibration mill, a turbo mill, a cutter mill.

The acceptor element-containing glass particles (compound containing acceptor elements in the form of glass particles) include at least one acceptor element-containing substance selected from the group consisting of B ₂ O ₃ and Al ₂ O ₃ , and 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 , MoO ₃ , Y ₂ O ₃ , Containing at least one glass component material selected from the group consisting of TiO ₂ , TeO ₂ , La ₂ O ₃ , Nb ₂ O ₅ , Ta ₂ O ₅ , GeO ₂ , Lu ₂ O ₃ and MnO. And at least one acceptor element-containing material selected from the group consisting of B ₂ O ₃ and Al ₂ O ₃ , and SiO ₂ , K ₂ O, Na ₂ O, Li _{2 O, BaO, SrO, CaO} , MgO, BeO, selected ZnO, PbO, _CdO, from _{V 2 O 5, SnO, ZrO} 2, MoO 3, GeO 2, Y 2 O 3, the group consisting of CsO ₂ and TiO ₂ It is more preferable to contain at least one kind of glass component substance, and at least one acceptor element-containing substance selected from the group consisting of B ₂ O ₃ and Al ₂ O ₃ , SiO ₂ , K ₂ At least one glass selected from the group consisting of 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. more preferably containing a component material, and at least one acceptor element-containing material selected from the group consisting of B ₂ O ₃ and Al ₂ O _{3 SiO 2, K 2 O, Na} 2 O, Li 2 O, BaO, SrO, CaO, MgO, contain BeO, ZnO, and the glass component material at least one selected from the group consisting of ZrO _2, the Is particularly preferred.
Furthermore, the glass particles include Al ₂ O ₃ as the acceptor element-containing material, and at least one selected from the group consisting of SiO ₂ , ZnO, CaO, Na ₂ O, Li ₂ O, and BaO as the glass component material. It is preferable to include. When these component substances coexist than when B ₂ O ₃ which is an acceptor element-containing substance is used alone, the resistance of the formed impurity diffusion layer becomes lower, and the out diffusion can be suppressed. It becomes possible.

When BN is used as a compound containing an acceptor element, the crystal form of BN may be any of hexagonal, cubic, and rhombohedral, but the particle size can be easily controlled. A hexagonal crystal is preferable because it can be formed.
The method for preparing BN is not particularly limited, and can be prepared by a usual method. Specifically, a method in which boron powder is heated to 1500 ° C. or higher in a nitrogen stream, a method in which molten boric acid and nitrogen or ammonia are reacted in the presence of calcium phosphate, boric acid or an alkali boride, urea, guanidine, Illustrate a method of reacting organic nitrogen compounds such as melamine in a high temperature nitrogen-ammonia atmosphere, a method of reacting molten sodium borate and ammonium chloride in an ammonia atmosphere, and a method of reacting boron trichloride and ammonia at a high temperature. However, there is no problem with manufacturing methods other than those described above. Among the above production methods, it is preferable to use a method in which boron trichloride and ammonia are reacted at a high temperature because high-purity BN can be obtained.

  The compound containing an acceptor element may be a boron-containing silicon oxide compound. Here, the boron-containing silicon oxide compound will be described in detail. The boron-containing silicon oxide compound means a compound synthesized by reacting a boron compound with a silicon oxide precursor based on a sol-gel reaction, and boron glass can be distinguished from the glass particles so that the synthesis method is different. It will be described as a contained silicon oxide compound.

  The boron-containing silicon oxide compound obtained by reacting a silicon oxide precursor with a boron compound has a structure in which the boron compound is dispersed in a silicon oxide (siloxane) network, so that the volatility of the boron compound is suppressed, and silicon Outdiffusion tends to be suppressed at a high temperature at which a p-type diffusion layer is formed on a semiconductor substrate such as a substrate.

  The boron compound not included in the silicon oxide (siloxane) network may be removed by previously washing the boron-containing silicon oxide compound with water. By doing in this way, out diffusion can be suppressed.

As a method for synthesizing the boron-containing silicon oxide compound, a silicon oxide precursor, a boron compound, a solvent used in a sol-gel reaction, water, and an acid or alkali catalyst are mixed, and alcohol and water are mixed at a predetermined temperature. The method of synthesizing a silicon oxide compound containing a boron compound in a network of siloxanes can be exemplified by removing a hydrogen atom to cause a hydrolysis reaction of the silicon oxide precursor. Moreover, since hygroscopicity can also be suppressed, reaction with a dispersion medium and reaction with moisture can be suppressed, and chemical stability in the impurity diffusion layer forming composition can be improved.

  Examples of the silicon oxide precursor include silicon methoxide, silicon ethoxide, silicon propoxide, and silicon butoxide. However, at least one selected from the group consisting of silicon methoxide and silicon ethoxide is available because of availability. It is preferable to use seeds. The silicon oxide precursor is a raw material of the sol-gel reaction, and the sol-gel reaction here is a hydrolysis reaction of silicate and a condensation reaction of silanol groups, resulting in a three-dimensional structure having a silicon-oxygen bond as a structural unit. This reaction forms a crosslinked silica gel matrix.

  The solvent used in the sol-gel reaction is not particularly limited as long as it dissolves the polymer of the silicon oxide precursor, but alcohols such as ethanol and isopropanol, acetonitrile, glutaronitrile, methoxyacetonitrile, propionitrile, Nitrile compounds such as benzonitrile and cyclic ethers such as dioxane and tetrahydrofuran are preferably used. These may be used alone or in combination of two or more. The amount of the solvent is preferably 0 equivalent to 100 equivalents, more preferably 1 equivalent to 10 equivalents, relative to the silicon oxide precursor. If the amount of the solvent is too large, the sol-gel reaction of the silicon oxide precursor tends to be slow.

  Furthermore, it is preferable to use an acid or an alkali as a catalyst for controlling hydrolysis and dehydration condensation polymerization. As the alkali catalyst, alkali metal hydroxide such as sodium hydroxide, ammonia, tetramethylammonium hydroxide and the like are generally used. An inorganic or organic proton acid can be used as the acid catalyst. Examples of the inorganic protonic acid include hydrochloric acid, sulfuric acid, boric acid, nitric acid, perchloric acid, tetrafluoroboric acid, hexafluoroarsenic acid, hydrobromic acid and the like. Examples of the organic protonic acid include acetic acid, oxalic acid, methanesulfonic acid and the like. Since the solubility of the sol in the solvent changes depending on the amount of the acid, it may be adjusted so that the sol has a soluble solubility, and 0.0001 equivalent to 1 equivalent is preferable with respect to the silicon oxide precursor.

  Also, a boron-containing silicon oxide compound is prepared by adding a solution containing metal nitrate, ammonium salt, chloride salt, sulfate, etc. to the sol solution of the silicon oxide precursor and then proceeding with the sol-gel reaction. May be. Examples of the salt include, but are not limited to, aluminum nitrate, iron nitrate, zirconium oxynitrate, titanium chloride, aluminum chloride, zirconium oxychloride, zirconium oxynitrate, titanium sulfate, and aluminum sulfate. The salt solvent is not particularly limited as long as it dissolves the salt, but carbonate solvents such as ethylene carbonate and propylene carbonate; heterocyclic solvents such as 3-methyl-2-oxazolidinone and N-methylpyrrolidone; dioxane, Cyclic ether solvents such as tetrahydrofuran; chain ether solvents such as diethyl ether, ethylene glycol dialkyl ether, propylene glycol dialkyl ether, polyethylene glycol dialkyl ether, polypropylene glycol dialkyl ether; methanol, ethanol, isopropanol, ethylene glycol monoalkyl ether, propylene glycol Monoalkyl ether, polyethylene glycol monoalkyl ether, polypropylene glycol monoalkyl ether, etc. Polyol alcohol solvent such as ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, glycerin; Nitrile solvent such as acetonitrile, glutaronitrile, methoxyacetonitrile, propionitrile, benzonitrile; carboxylate ester, phosphate ester Ester solvents such as phosphonic acid esters; aprotic polar solvents such as dimethyl sulfoxide, sulfolane, dimethylformamide and dimethylacetamide; hydrocarbon solvents such as toluene and xylene; chlorinated solvents such as methylene chloride and ethylene chloride; be able to.

Examples of the boron compound used for the sol-gel reaction include boron oxide and boric acid. Boron oxide is a compound represented by B ₂ O ₃ and may be a crystallized product or a glassy material. Boric acid is a compound represented by H ₃ BO ₃ and B (OH) ₃ . These compounds are dissolved in water and exist in the state of H ₃ BO ₃ . In addition to boron oxide and boric acid, any compound that can be dissolved in water to form H ₃ BO ₃ is not limited to the type of boron compound used as an auxiliary material. Examples of the compound that dissolves in water to become H ₃ BO ₃ include boric acid esters.

As said boric acid ester, the compound represented by the following general formula (I) is mentioned. Here, R < ⁷ > -R < ⁹ > in general formula (I) is respectively independently a C1-C10 organic group or a hydrogen atom.

There is no restriction | limiting in particular as an organic group represented by R < ⁷ > -R < ⁹ > in general formula (I), Each is independently an alkyl group, an organic group which has a functional group, an organic group which has a hetero atom, and an unsaturated bond. The organic group which has.

The alkyl group represented by R ^{7 to} R ⁹ may be linear, branched or cyclic, and is preferably linear or branched. The alkyl group represented by R ^{7 to} R ⁹ preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, and 1 to 3 carbon atoms. Further preferred. Specific examples of the alkyl group represented by R ^{7 to} R ⁹ include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, and a decyl group. It is done.

In the organic group having a functional group represented by R ^{7 to} R ⁹ , examples of the functional group include chloro, bromo, and fluoro groups. The organic group having a functional group represented by R ^{7 to} R ⁹ preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, and 1 to 3 carbon atoms. More preferably. Specific examples of the organic group having a functional group represented by R ^{7 to} R ⁹ include chloroethyl, fluoroethyl, chloropropyl, dichloropropyl, fluoropropyl, difluoropropyl, chlorophenyl, and fluorophenyl groups.

In the organic group having a hetero atom represented by R ^{7 to} R ⁹ , examples of the hetero atom include a nitrogen atom, an oxygen atom, and a sulfur atom. The organic group having a heteroatom represented by R ^{7 to} R ⁹ preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, and 1 to 3 carbon atoms. More preferably. Specific examples of the organic group having a hetero atom represented by R ^{7 to} R ⁹ include dimethylamino, diethylamino, diphenylamino, methyl sulfoxide, ethyl sulfoxide, and phenyl sulfoxide groups.

The organic group having an unsaturated bond represented by R ^{7 to} R ⁹ preferably has 2 to 10 carbon atoms, more preferably 2 to 10 carbon atoms, and 2 to 4 carbon atoms. More preferably it is. Specific examples of the organic group having an unsaturated bond represented by R ^{7 to} R ⁹ include ethylenyl, ethynyl, propenyl, propynyl, butenyl, butynyl, and phenyl groups.

Among these, the monovalent organic group represented by R ^{7 to} R ⁹ is preferably an alkyl group, and more preferably an alkyl group having 1 to 10 carbon atoms.
As the boric acid ester used in the sol-gel reaction, it is preferable to use at least one selected from the group consisting of trimethyl borate, triethyl borate, tripropyl borate, and tributyl borate.

The content rate of the compound containing the acceptor element in the p-type diffusion layer forming composition is determined in consideration of the coating property, the diffusibility of the compound containing the acceptor element, and the like. In general, the content of the compound containing an acceptor element in the p-type diffusion layer forming composition is preferably 0.1% by mass or more and 95% by mass or less in the p-type diffusion layer forming composition. More preferably, it is more preferably not less than 90% by mass and more preferably not more than 1% by mass and not more than 80% by mass, particularly preferably not less than 2% by mass and not more than 50% by mass. As mentioned above, it is very preferable that it is 20 mass% or less.
When the content of the compound containing the acceptor element in the p-type diffusion layer forming composition is 0.1% by mass or more, the impurity diffusion layer can be sufficiently formed, and when it is 95% by mass or less, p The dispersibility of the compound containing the acceptor element in the composition for forming the diffusion layer is improved, and the coating property to the semiconductor substrate is improved.

(Dispersion medium)
The p-type diffusion layer forming composition of the present invention may further contain a dispersion medium.
The dispersion medium is a solvent for adjusting the viscosity in 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, ferrandrene, and the like; water . These are used singly or in combination of two or more.

  The content ratio of the dispersion medium in the p-type diffusion layer forming composition is determined in consideration of applicability and viscosity.

(High viscosity solvent)
The p-type diffusion layer forming composition of the present invention may contain a high viscosity solvent. High viscosity solvents are isobornyl cyclohexanol, isobornyl phenol, 1-isopropyl-4-methyl-bicyclo [2.2.2] oct-5-ene-2,3-dicarboxylic anhydride, p-mentenyl. It preferably contains at least one selected from phenol and at least one selected from isobornylcyclohexanol and isobornylphenol. These compounds decompose or volatilize at a low temperature (for example, 400 ° C. or lower), and have a high viscosity due to their bulky structure, so that they can be used as an alternative to conventionally used binder resins such as ethyl cellulose. In particular, when a p-type diffusion layer forming composition is applied to a semiconductor substrate by a screen printing method, it is necessary to increase the viscosity. In this case, a large amount of ethyl cellulose is used (for example, 5% by mass in the p-type diffusion layer forming composition). Must be included. In this case, in the drying and firing steps, the resin remains, and this residue becomes a resistor, which may adversely affect the power generation characteristics of the solar cell element. On the other hand, since the amount of the resin binder can be reduced by using the high-viscosity solvent, it can be reduced to such an extent that the residual resin does not become a problem.

  Although there is no restriction | limiting in particular in the ratio of the compound containing an acceptor element, and a high-viscosity solvent, 1 mass% or more of the compound containing an acceptor element in a p-type diffused layer formation composition is 50 mass% or less, and the said high viscosity solvent is 1 mass. Preferably, the compound containing the acceptor element in the p-type diffusion layer forming composition is contained in an amount of 5% by mass to 40% by mass, and the high-viscosity solvent is contained in an amount of 5% by mass to 95% by mass. It is more preferable.

(3) Binder The p-type diffusion layer forming composition of the present invention contains a binder from the viewpoint of preventing scattering of a compound containing an acceptor element in a state of being applied and dried on a substrate, or adjusting the viscosity. May be.
Examples of the binder include polyvinyl alcohol, polyacrylamides, polyvinylamides, polyvinylpyrrolidone, polyethylene oxides, polysulfonic acid, acrylamide alkylsulfonic acid, cellulose ethers, cellulose derivatives (carboxymethylcellulose, hydroxyethylcellulose, ethylcellulose, etc.), gelatin Starch, starch derivatives, sodium alginate, xanthan, guar and guar derivatives, scleroglucan and scleroglucan derivatives, tragacanth and tragacanth derivatives, dextrin and dextrin derivatives, (meth) acrylic acid resins, (meth) acrylic acid ester resins (For example, alkyl (meth) acrylate resin, dimethylaminoethyl (meth) acrylate resin, etc.), butadiene Fat, styrene resins and copolymers thereof, siloxane resin may appropriately selecting a metal alkoxide. Among these binders, it is preferable to use a cellulose derivative or an acrylic resin from the viewpoint of easily adjusting the viscosity and thixotropy even in a small amount.
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 as the composition.

  Although there is no restriction | limiting in particular in content of the binder in the p-type diffused layer formation composition of this embodiment, It is preferable that it is less than 10 mass%, It is more preferable that it is less than 3 mass%, It is less than 1 mass% More preferably it is.

(Inorganic filler)
The p-type diffusion layer forming composition of this embodiment may contain an inorganic filler. Examples of the inorganic filler include silica, clay, and silicon carbide. Among these, it is preferable to use a filler containing at least silica as a component. By adding the inorganic filler, it is possible to suppress thermal sagging of the coated material in the step of applying and drying the p-type diffusion layer forming composition to decompose and volatilize the high viscosity solvent. The cause of the thermal sag is that the viscosity of the solvent decreases at a temperature of about 100 ° C. to 500 ° C. where the high viscosity solvent is decomposed and volatilized. When an inorganic filler is included, since a decrease in viscosity can be suppressed, thermal sag can be suppressed.

The BET specific surface area of the inorganic filler is preferably 50 to 500 m ² / g, and more preferably 100 to 300 m ² / g. As such an inorganic filler having a high BET specific surface area, fumed silica can be exemplified. By using an inorganic filler having a high BET specific surface area, it tends to be easy to suppress a decrease in viscosity due to physical and van der Waals interaction with a solvent whose viscosity has been reduced in the drying step. The BET specific surface area can be calculated by measuring the amount of nitrogen adsorbed at 77K.

  The fumed silica may be either hydrophilic or hydrophobic.

  The content of the inorganic filler in the p-type diffusion layer forming composition is preferably 0.01% by mass to 40% by mass, more preferably 0.1% by mass to 20% by mass, and 0.2% by mass. It is still more preferable that it is% -5 mass%. By setting it as 0.01 mass or more, the effect which suppresses generation | occurrence | production of the thermal dripping in a drying process is acquired, and the application | coating characteristic of p-type diffused layer formation composition can be ensured by setting it as less than 40 mass%.

(Alkoxysilane)
The p-type diffusion layer forming composition of this embodiment may further contain alkoxysilane. By including alkoxysilane, the viscosity of the paste tends to be maintained when the paste is dried. The alkoxy group constituting the alkoxysilane is preferably a linear or branched alkyloxy group, more preferably a linear or branched alkyloxy group having 1 to 24 carbon atoms, More preferably, it is a linear or branched alkyloxy group having 1 to 10 carbon atoms, and particularly preferably a linear or branched alkyloxy group having 1 to 4 carbon atoms.
Specific examples of the alkoxy group include methyl group, ethyl group, propyl group, butyl group, i-propyl group, i-butyl group, pentyl group, hexyl group, octyl group, 2-ethylhexyl group, t-octyl group, Examples thereof include a decyl group, a dodecyl group, a tetradecyl group, a 2-hexyldecyl group, a hexadecyl group, an octadecyl group, a cyclohexylmethyl group, and an octylcyclohexyl group.
Among these, it is preferable to use tetramethoxysilane, tetraalkoxysilane, or tetraisopropoxysilane.

(Silane coupling agent)
The p-type diffusion layer forming composition of this embodiment may further contain a silane coupling agent. The silane coupling agent has two functional groups different in silicon, organic functional group and alkoxy group in one molecule, and there is no particular limitation on the structure, but it is represented by the following general formula (II) Can be illustrated.
^{_{X n R 2 (3-n}} ) SiR 1 -Y ··· (II)

In the general formula (II), X represents a methoxy group or an ethoxy group. Y is vinyl group, mercapto group, epoxy group, amino group, styryl group, isocyanurate group, isocyanate group, acrylic group, methacryl group, glycidoxy group, ureido group, sulfide group, carboxyl group, acryloxy group, methacryloxy group, alkyl group , Phenyl group or trifluoroalkyl group, alkylene glycol group, amino alcohol group, quaternary ammonium group, and the like. Of these, a vinyl group, an amino group, an epoxy group, an acryloxy group, a methacryloxy group, an alkyl group, and a trifluoroalkyl group are preferable, and an acryloxy group and a trifluoromethyl group are more preferable.
In the general formula (II), R ¹ represents an alkylene group having 0 to 10 carbon atoms or a divalent linking group having 2 to 5 atoms in the main chain and containing a nitrogen atom in the main chain. The alkylene group is preferably an ethylene group or a propylene group. The atomic group containing a nitrogen atom in the linking group is preferably an amino group or the like.
In the general formula (II), R ² represents an alkyl group having 1 to 5 carbon atoms, preferably a methyl group or an ethyl group, and more preferably a methyl group. Note that n represents an integer of 1 to 3.

  Specific examples of the silane coupling agent include the following groups (a) to (c). (A) Those having a (meth) acryloxy group: 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyldimethyldiethoxysilane, 3 -Methacryloxypropyltriethoxysilane, etc. (b) having an epoxy group or glycidoxy group: 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and 2- (3,4 epoxy) (Cyclohexyl) ethyltrimethoxysilane, etc. (c) those having an amino group: N- (2-aminoethyl) 3-aminopropylmethyldimethoxysilane, N- (aminoethyl) 3-aminopropyltrimethoxysilane, and 3 -Aminopro (D) those having a mercapto group: 3-mercaptopropyltrimethoxysilane, etc. (e) those having an alkyl group: methyltrimethoxysilane, dimethyldimethoxysilane, methyltriethoxysilane, dimethyldi Ethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, 1,6-bis (trimethoxysilyl) hexane, etc. (F) Those having a phenyl group: phenyltrimethoxysilane, phenyltriethoxysilane, etc. (g) Those having a trifluoroalkyl group: trifluoropropyltrimethoxysilane, etc.

The method for producing the p-type diffusion layer forming composition of the present embodiment is not particularly limited. For example, it can be obtained by mixing a compound containing an acceptor element and a highly viscous solvent using a blender, a mixer, a mortar, and a rotor. Moreover, when mixing, you may add a heat | fever as needed. When heating at the time of mixing, the temperature can be 30-100 degreeC, for example.
The components contained in the p-type diffusion layer forming composition and the content of each component are thermal analysis such as TG / DTA, NMR (nuclear magnetic resonance method), HPLC (high performance liquid chromatography), GPC (gel Permeation chromatography), GC-MS (gas chromatography mass spectrometry), IR (infrared spectroscopy), MALDI-MS (matrix-assisted laser desorption / ionization mass spectrometry) can be used.

  In the p-type diffusion layer forming composition of the present embodiment, the total amount of lifetime killer elements is preferably 1000 mass ppm or less, more preferably 500 mass ppm or less, and 100 mass pm or less. More preferred is 50 ppm or less. By being 1000 ppm or less, the lifetime of the substrate tends to be improved.

  Examples of the lifetime killer element include Fe, Cu, Ni, Mn, Cr, W, and Au. The amount of these elements can be analyzed by an ICP (inductively coupled plasma) mass spectrometer, an ICP emission spectrometer, or an atomic absorption spectrometer. The lifetime of the carrier can be measured by a microwave photoconductive decay method (μ-PCD method). These elements have a high diffusion rate in the semiconductor substrate, reach everywhere in the bulk of the substrate, and act as recombination centers.

<Manufacturing method of semiconductor substrate having p-type diffusion layer>
The method for producing a semiconductor substrate having a p-type diffusion layer according to the present embodiment is also referred to as a p-type diffusion layer forming composition containing a compound containing an acceptor element and a dispersion medium (hereinafter also referred to as “specific p-type diffusion layer forming composition”). ) Has a step of heat-treating the semiconductor substrate applied to a part of the region (hereinafter also referred to as “heat-treatment step”). The semiconductor substrate to which the specific p-type diffusion layer forming composition is applied may be a purchased product, or the specific p-type diffusion layer forming composition is applied to a partial region on the surface of the semiconductor substrate. You may produce by a process (henceforth a "giving process"). The method for producing a semiconductor substrate having a p-type diffusion layer of the present invention may further include other steps as necessary.

(Granting process)
In the applying step, a p-type diffusion layer forming composition containing a compound containing an acceptor element and a dispersion medium is applied to a partial region of the semiconductor substrate.

  A semiconductor substrate in particular is not restrict | limited, The normal thing used for a solar cell element can be applied. For example, silicon substrate, gallium phosphide substrate, gallium nitride substrate, diamond substrate, aluminum nitride substrate, indium nitride substrate, gallium arsenide substrate, germanium substrate, zinc selenide substrate, zinc telluride substrate, cadmium telluride substrate, cadmium sulfide Examples include a substrate, a gallium arsenide substrate, an indium phosphide substrate, a gallium nitride substrate, a silicon carbide, a silicon germanium substrate, and a copper indium selenium substrate. The semiconductor substrate is preferably pretreated before applying the p-type diffusion layer forming composition. Examples of the pretreatment include the following steps. In the following description, a p-type semiconductor substrate is used, but an n-type semiconductor substrate may be used.

  An alkaline solution is applied to the p-type semiconductor substrate to remove the damaged layer, and a texture structure is obtained by etching. Specifically, the damaged layer on the surface of the p-type semiconductor substrate generated when slicing from the ingot is removed with a 20% by mass aqueous sodium hydroxide solution. 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 solar cell element has a texture structure on the light receiving surface side, thereby promoting a light confinement effect and increasing efficiency.

Next, in a mixed gas atmosphere of phosphorus oxychloride (POCl ₃ ), nitrogen and oxygen, treatment is performed at 800 ° C. to 900 ° C. for several tens of minutes to uniformly form an n-type diffusion layer on the surface of the semiconductor substrate. . At this time, in the method using the phosphorus oxychloride atmosphere, the diffusion of phosphorus extends to the side surface and the back surface, and the n-type diffusion layer is formed not only on the light receiving surface but also on the side surface and the back surface. Therefore, side etching for removing the n-type diffusion layer formed on the side surface is performed.

  Then, a specific p-type diffusion layer forming composition is applied to a partial region of the pretreated semiconductor substrate. When a p-type semiconductor substrate is used, a specific p-type diffusion layer forming composition is applied on the n-type diffusion layer on the back surface (that is, the surface opposite to the light receiving surface).

  There is no restriction | limiting in particular in the provision method of a specific p-type diffused layer formation composition, A printing method, a spin coat method, brush coating, a spray coat method, a doctor blade method, a roll coat method, an inkjet method etc. are mentioned.

  The content ratio of the dispersion medium in the p-type diffusion layer forming composition is determined in consideration of applicability and acceptor concentration. The viscosity of the p-type diffusion layer forming composition is preferably 10 mPa · s to 1,000,000 mPa · s, more preferably 50 mPa · s to 500,000 mPa · s in consideration of applicability.

  Depending on the composition of the p-type diffusion layer forming composition, a drying step for volatilizing the solvent may be required after the p-type diffusion layer forming composition is applied to the semiconductor substrate and before the heat treatment step described later. . In this case, drying is performed at a temperature of about 80 ° C. to 300 ° C. for about 1 minute to 10 minutes when using a hot plate, and about 10 minutes to 30 minutes when using a dryer or the like. This drying condition can be appropriately adjusted according to the solvent composition of the p-type diffusion layer forming composition.

(Thermal diffusion process)
The heat treatment for diffusing boron is preferably performed at 600 ° C. to 1200 ° C., and more preferably at 850 ° C. to 1000 ° C. By this heat treatment, boron diffuses into the semiconductor substrate, and a p-type diffusion layer, a p ⁺ -type diffusion layer, and the like are formed. A known continuous furnace, batch furnace, or the like can be applied to the heat treatment.

  The gas composition in the atmosphere of the heat treatment is not particularly limited other than oxygen, and can be composed of nitrogen, argon, neon, xenon, krypton, helium, carbon dioxide, hydrogen, air, or the like. Among these, from the viewpoint of cost and safety, a gas composition composed of oxygen and nitrogen is preferable. When air is used as a gas other than oxygen, the oxygen concentration is adjusted in consideration of the amount of oxygen contained in the air.

  The diffusion atmosphere may be changed in the middle. For example, heat diffusion may be performed in a nitrogen atmosphere, and in the subsequent temperature lowering process, the atmosphere may be changed to an oxygen-containing atmosphere. At the time of diffusion, it is carried out in nitrogen to promote the formation of a boron silicide layer (boron rich layer), effectively gettering metal impurities, and then oxidizing the boron silicide layer in the temperature lowering process. The passivation effect in the passivation process can be sufficiently obtained. The proportion of oxygen in the temperature lowering process is preferably 0.1% by volume to 100% by volume, more preferably 1% by volume to 80% by volume, and further more preferably 5% by volume to 50% by volume. preferable.

Since a glass layer is formed as a heat-treated product (baked product) of the p-type diffusion layer forming composition on the surface of the p ⁺ -type diffusion layer formed by the heat treatment, the semiconductor substrate is treated with an etching solution after the heat treatment. You may have a process. Thereby, the produced | generated glass layer is removed by an etching. In addition, the oxide mask layer on the Si substrate formed outside the application region of the p-type diffusion layer forming composition is simultaneously etched with the etchant.
Examples of the etching solution include aqueous solutions of hydrogen fluoride, ammonium fluoride, ammonium hydrogen fluoride, and the like, and aqueous solutions of sodium hydroxide. As the etching process, a known method such as immersing a semiconductor substrate in an etching solution can be applied.
Before removing the glass layer, a step of wet oxidizing the boron silicide layer may be included. For example, the method of processing a semiconductor substrate in the state which heated the aqueous solution containing nitric acid to 80 to 200 degreeC is mentioned.

In the semiconductor substrate having the p-type diffusion layer obtained by the manufacturing method of the present embodiment, an electrode can be separately provided on the p ⁺ -type diffusion layer. That is, according to the present embodiment, the formation of the p-type diffusion layer and the formation of the electrode can be performed separately, and the following effects are obtained.

In the conventional manufacturing method, an aluminum paste is printed on the back surface, and this is heat-treated (fired) so that the n-type diffusion layer becomes a p ⁺ -type diffusion layer and an ohmic contact is obtained. However, since the electrical conductivity of the aluminum paste is low, the sheet resistance has to be lowered, and the aluminum layer 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 thermal expansion coefficients of silicon and aluminum differ greatly, a large internal stress is generated in the semiconductor substrate during the heat treatment (firing) and cooling, which causes warpage.

  This internal stress tends to damage the crystal grain boundaries and increase power loss. In addition, warping tends to damage cells in the transportation of solar cell elements and the connection with copper wires called tab wires in the module process. In recent years, due to the improvement of slicing technology, the thickness of the crystalline semiconductor substrate is being reduced, and the cells tend to be easily broken.

However, according to the manufacturing method of the present embodiment, after the n-type diffusion layer is converted into the p ⁺ -type diffusion layer by the specific p-type diffusion layer forming composition, an electrode is separately provided on the p ⁺ -type diffusion layer. That is, the p ⁺ type diffusion layer forming step and the ohmic contact forming step can be separated. Therefore, the material used for the back electrode is not limited to aluminum, for example, Ag (silver), Cu (copper) can be applied, and the thickness of the back electrode can be formed thinner than the conventional one. Furthermore, it is not necessary to form electrodes on the entire surface, and they may be formed partially like a comb shape. Therefore, it is possible to reduce internal stress and warpage in the semiconductor substrate that are generated in the course of heat treatment (firing) and cooling.

In the above method for manufacturing a semiconductor substrate having a p-type diffusion layer, a mixed gas of phosphorus oxychloride (POCl ₃ ), nitrogen and oxygen is used to form an n-type diffusion layer on the p-type semiconductor substrate. However, the n-type diffusion layer may be formed using the n-type diffusion layer forming composition. The n-type diffusion layer forming composition contains a Group 15 element such as P (phosphorus) or Sb (antimony) as a donor element.

  Next, a method for manufacturing a semiconductor substrate having a p-type diffusion layer will be described with reference to the drawings. FIG. 1 and FIG. 2 are sectional views showing process drawings schematically showing an example of a method for manufacturing a semiconductor substrate having a p-type diffusion layer. However, this process diagram does not limit the present invention.

  FIG. 1 is a diagram for explaining an example of a manufacturing process of a point contact type solar cell element. In FIGS. 1A to 1I, a p type diffusion layer used for a point contact type solar cell element is shown. A manufacturing process of a semiconductor substrate having the following will be described. In FIG. 1, description will be made using a p-type semiconductor substrate 10.

  First, the p-type semiconductor substrate 10 is preferably washed with an alkaline aqueous solution. By washing with an alkaline aqueous solution, organic substances, particles and the like existing on the surface of the p-type semiconductor substrate 10 can be removed, and the passivation effect is further improved. As a method for cleaning with an alkaline aqueous solution, generally known RCA cleaning and the like can be exemplified. For example, the p-type semiconductor substrate 10 is immersed in a mixed solution of aqueous ammonia and hydrogen peroxide and treated at 60 ° C. to 80 ° C., so that organic substances and particles can be removed and washed. The washing time is preferably 10 seconds to 10 minutes, and more preferably 30 seconds to 5 minutes.

  Next, a texture structure (pyramid shape) (not shown in FIG. 1A) is formed on the light receiving surface (front surface) of the p-type semiconductor substrate 10 by alkali etching or the like to suppress reflection of sunlight on the light receiving surface.

Thereafter, as shown in FIG. 1B, the n-type diffusion layer forming composition 11 is applied to a part of the light-receiving surface, and heat-treated as shown in FIG. Form. As the n-type diffusion layer forming composition 11, a liquid containing phosphorus or antimony can be used. For example, a liquid described in JP 2012-084830 A may be used. The heat treatment temperature is preferably 800 ° C to 1000 ° C. There is no particular limitation as an atmosphere of the heat treatment, only nitrogen, only O _2, air composition, etc. are preferably used.

  Next, as shown in FIG. 1D, a PSG (phosphosilicate glass) layer 14 is formed using phosphorus oxychloride or the like, and then, as shown in FIG. 1E, a second n-type diffusion layer 15 is formed. Form. Thereafter, the PSG layer 14 and the heat-treated product (baked product) 12 of the n-type diffusion layer forming composition are removed by immersing in an etching solution such as hydrofluoric acid (FIG. 1 (f)).

  Next, as shown in FIG. 1G, a specific p-type diffusion layer forming composition 16 is applied to the back surface. At this time, the region to which the p-type diffusion layer forming composition is applied may be a part of the back surface or the entire surface of the semiconductor substrate.

Next, as shown in FIG. 1H, heat treatment is performed to form a p ⁺ -type diffusion layer 17. The heat treatment temperature is preferably 800 ° C to 1050 ° C. The atmosphere during boron diffusion is preferably performed in nitrogen, and then preferably includes a step of heat treatment in an atmosphere containing oxygen. The diffusion atmosphere is preferably determined in consideration of the balance between the formation of the boron silicide layer, the subsequent oxidation of the boron silicide layer, and the ease of removal by hydrofluoric acid.

Next, as shown in FIG. 1 (i), a heat-treated product (baked product) of the p-type diffusion layer forming composition is immersed in an aqueous solution (etching solution) such as hydrogen fluoride, ammonium fluoride, and ammonium hydrogen fluoride. ) Remove 16 '. Thereby, the p-type semiconductor substrate 10 having the p ⁺ -type diffusion layer 17 is obtained. Further, the oxide layer functioning as a mask layer is also removed at a time.

  FIG. 2 is a diagram for explaining an example of a manufacturing method of a back electrode type solar cell element. In FIGS. 2A to 2H, a p type diffusion layer used for a back electrode type solar cell element is shown. A manufacturing process of a semiconductor substrate having the following will be described. In FIG. 2, description will be made using the n-type semiconductor substrate 30.

  In the n-type semiconductor substrate 30 shown in FIG. 2A, a texture structure (pyramid shape) (not shown) is formed on the light receiving surface (surface) by alkali etching or the like. The texture structure suppresses the reflection of sunlight from the light receiving surface.

  After that, as shown in FIG. 2B, a specific p-type diffusion layer forming composition 31 is applied to a part of the back surface, and heat treatment is performed as shown in FIG. To do. The specific p-type diffusion layer forming composition 31 contains glass particles containing a p-type impurity and a dispersion medium. The heat treatment temperature is preferably 800 ° C to 1050 ° C. The heat treatment is performed in an atmosphere having an oxygen concentration of 3% by volume or more. Here, the region other than the application region of the p-type diffusion layer forming composition 31 is oxidized to form an oxide mask layer (not shown).

  Thereafter, the heat-treated product (baked product) 31 'of the p-type diffusion layer forming composition is removed by immersing in an etching solution such as hydrofluoric acid (FIG. 2D). The oxide mask layer is also removed at a time.

Next, as shown in FIG. 2E, a mask layer 33 for preventing diffusion is formed on the surface of the p-type diffusion layer. The mask layer 33 can be formed by applying a liquid containing a siloxane resin or the like serving as a precursor of SiO ₂ and performing heat treatment (firing).

Next, as shown in FIG. 2F, the n-type diffusion layer forming composition 34 is applied to a part of the light receiving surface and the back surface. Next, as shown in FIG. 2G, the n ⁺ -type diffusion layer 35 is formed by heat treatment. The temperature for the heat treatment is preferably 800 ° C to 1050 ° C. There is no particular limitation as an atmosphere of the heat treatment, only nitrogen, only O _2, air composition, etc. are preferably used. As an n type diffused layer formation composition, you may use the thing of Unexamined-Japanese-Patent No. 2012-084830, for example.

  Next, it is immersed in an etching solution such as hydrofluoric acid to remove the heat-treated product (baked product) 34 ′ of the n-type diffusion layer forming composition (FIG. 2 (h)). Thereby, an n-type semiconductor substrate having the p-type diffusion layer 32 is obtained.

<Method for producing solar cell element>
The manufacturing method of the solar cell element of this embodiment has the process of forming an electrode on the p-type diffusion layer of the semiconductor substrate which has a p-type diffusion layer obtained by the above-mentioned manufacturing method. The method for forming the electrode is not particularly limited, and examples thereof include a method in which a metal paste for forming an electrode is applied by a screen printing method or the like, followed by heat treatment (firing). In the semiconductor substrate having the p-type diffusion layer, an antireflection film may be formed on the light receiving surface side before the electrode is formed. An example of a method for manufacturing a solar cell element will be described below.

In the above-described method for manufacturing a semiconductor substrate having a p-type diffusion layer, a p-type semiconductor substrate is used, an n-type diffusion layer is formed on the light receiving surface side, and a p-type diffusion layer is formed on the back surface side. In this case, an antireflection film is formed on the n-type diffusion layer formed on the light receiving surface side. The antireflection film is formed by applying a known technique. For example, when the antireflection film 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 orbitals that do not contribute to the bonding of silicon atoms, that is, dangling bonds and hydrogen are bonded to inactivate defects (hydrogen passivation). More specifically, the mixed gas flow ratio NH ₃ / SiH ₄ is 0.05 to 1.0, the reaction chamber pressure is 13.3 Pa to 266.6 Pa (0.1 Torr to 2 Torr), and the temperature during film formation is It is formed under conditions of 300 to 550 ° C. and a frequency for plasma discharge of 100 kHz or more.

  On the antireflection film of the light receiving surface, a metal paste for the light receiving surface electrode is printed by a screen printing method and dried to form the light receiving surface electrode. The metal paste for the light-receiving surface electrode includes metal particles and glass particles as essential components, and includes a resin binder, other additives, and the like as necessary.

Next, a back electrode is also formed on the p ⁺ -type diffusion layer on the back surface. As described above, in the present embodiment, the material and forming method of the back electrode are not particularly limited. For example, a back electrode paste containing a metal such as aluminum, silver, or copper may be applied and dried to form the back electrode. At this time, a silver paste for forming a silver electrode may be partially provided on the back surface for connection between cells in the module process.

A passivation film may be formed on the p ⁺ type diffusion layer. For example, a method of laminating an Al ₂ O ₃ layer by an ALD (atomic layer deposition) method or a thermally oxidized SiO ₂ film may be formed. At this time, it is preferable that the electrode forming portion is not formed with passivation by masking or the like, or is formed with a laser or the like after the passivation is formed on the entire surface.

  And an electrode is heat-processed (baking) and a solar cell element is completed. When heat treatment (firing) is performed in the range of 600 ° C. to 900 ° C. for several seconds to several minutes, the antireflection film, which is an insulating film, is melted by the glass particles contained in the electrode metal paste on the light receiving surface side, and part of the silicon surface is also formed. When melted, the metal particles (for example, silver particles) in the paste form a contact portion with the semiconductor substrate and solidify. Thereby, the formed light-receiving surface electrode and the semiconductor substrate are electrically connected. This is called fire-through.

  The light receiving surface electrode is generally composed of a bus bar electrode and a finger electrode intersecting with the bus bar electrode. Such a light-receiving surface electrode can be formed by means such as screen printing of the above-described metal paste, plating of the electrode material, or vapor deposition of the electrode material by electron beam heating in a high vacuum. The bus bar electrode and the finger electrode can be formed by a known method.

Next, the manufacturing method of a solar cell element is demonstrated, referring drawings.
In FIG. 1, a method for manufacturing a point contact type solar cell element will be described. In the p-type semiconductor substrate 10 having the p ⁺ -type diffusion layer 17 shown in FIG. 1 (i), an antireflection film 18 is formed on the light receiving surface as shown in FIG. 1 (j). Examples of the antireflection film 18 include a silicon nitride film and a titanium oxide film. A surface protective film (not shown) such as silicon oxide may further exist between the antireflection film 18 and the p-type semiconductor substrate 10.

  Next, as shown in FIG. 1K, a back surface passivation layer 19 such as a thermal oxide film or a silicon nitride film is formed on the entire back surface or a partial region. When the back surface passivation layer 19 is formed on the entire back surface of the semiconductor substrate 10, the back surface passivation layer 19 corresponding to the contact portion with the electrode is partially etched, or an electrode containing glass particles having fire-through properties as described later. It is preferable to use a forming paste. In the case of etching, a compound such as ammonium fluoride can be used.

  Thereafter, as shown in FIG. 1 (l), heat treatment is performed to form the light receiving surface electrode 20 and the back surface electrode 21 as shown in FIG. 1 (m). By using a paste containing fire-through glass particles as the electrode forming paste, the light-receiving surface electrode 20 is formed through the antireflection film 18 as shown in FIG. Ohmic contact can be obtained. As described above, a solar cell element having a point contact structure can be obtained.

In FIG. 2, the example of the manufacturing method of a back surface electrode type solar cell element is demonstrated. In the n-type semiconductor substrate 30 having the p-type diffusion layer 32 shown in FIG. 2 (h), a passivation layer 36 is formed on the light receiving surface and the back surface as shown in FIG. 2 (i). Examples of the passivation layer 36 include a silicon nitride film, a titanium oxide film, aluminum oxide, and silicon oxide. The passivation layer 36 on the light-receiving surface side may be improved in the antireflection function, for example, by forming a double-layer film of silicon oxide and silicon nitride. Further, the light-receiving surface side and the back surface side passivation layer 36 may be made of different materials, and the back surface passivation layer 36 has the surface of the semiconductor substrate having the p-type diffusion layer 32 and the n ⁺ -type diffusion layer 35. The composition of the passivation layer may be changed depending on the surface of the semiconductor substrate.

  Thereafter, as shown in FIG. 2 (j), an electrode forming paste for the p-electrode 37 and the n-electrode 38 is applied, followed by heat treatment to form an electrode. By using a paste containing fire-through glass particles as the electrode forming paste, the p-electrode 37 and the n-electrode 38 are formed through the passivation layer 36 as shown in FIG. Can be obtained. A back electrode type solar cell element can be obtained as described above.

<Solar cell element>
The solar cell element of this embodiment is obtained by the manufacturing method described above. Thereby, in the solar cell element, the p-type diffusion layer is prevented from being formed in an unnecessary region of the semiconductor substrate, and the battery performance is improved.
In the solar cell element, a wiring material such as a tab wire may be disposed on the electrode, and a plurality of solar cell elements may be connected via the wiring material to constitute a solar cell module. Furthermore, the solar cell module may be configured by being sealed with a sealing material.

  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]
(Synthesis of glass particles)
B ₂ O _3, the composition molar ratio of _SiO 2, _Al 2 _{O 3} and BaSO _4, respectively 40 mol%, 40 mol%, so that 10 mol% and _{10mol%, B 2 O 3,} SiO 2, Al 2 O 3 And BaSO ₄ (all manufactured by Kojundo Chemical Laboratory Co., Ltd.), mixed in an agate mortar, placed in a platinum crucible, held at 1500 ° C. for 2 hours in a glass melting furnace, and then rapidly cooled to glass A lump was obtained. This was ground in an agate mortar and then ground in a planetary ball mill to obtain glass particles having a spherical particle shape, an average particle size of 0.35 μm, and a softening temperature of about 800 ° C. 10 g, 6 g, and 84 g of the glass particles, ethyl cellulose, and terpineol were mixed to form a paste to prepare a p-type diffusion layer forming composition.

  Next, the composition A was applied to a part of the surface of a mirror-shaped n-type silicon substrate (thickness: 725 μm, specific resistance: 3.1 Ωcm, sheet resistance: 200 Ω / sq.) At 150 ° C. And dried for 10 minutes.

  The p-type diffusion layer forming composition is applied to one side of the n-type silicon substrate in a solid form by screen printing, dried at 150 ° C. for 1 minute, and then the n-type diffusion is applied to the other side of the p-type silicon substrate. The layer forming composition was applied by screen printing and dried at 150 ° C. for 1 minute.

Next, in a diffusion furnace (product name: 206A-M100, manufactured by Koyo Thermo System Co., Ltd.) in which nitrogen is supplied at 10 L / min, a boat containing a silicon substrate at 650 ° C. is introduced, and then 15 The temperature was raised to 950 ° C. at a temperature increase rate of ° C./min, and heat treatment was performed at 950 ° C. for 30 minutes to diffuse boron into the silicon substrate, thereby forming a p-type diffusion layer. Thereafter, O ₂ : 1 L / min and nitrogen: 9 L / min were flowed, the temperature was lowered to 650 ° C. at 4 ° C./min, and the boat was taken out at 650 ° C.

(Evaluation of sheet resistance)
The sheet resistance of the coating part was measured using a low resistivity meter (trade name: Loresta MCP-T360 (“Loresta” is a registered trademark) manufactured by Mitsubishi Chemical Analytech Co., Ltd.)). The sheet resistance of the coating part is 48Ω / sq. It was found that a p-type diffusion layer was formed.

(Lifetime evaluation)
Boron was diffused and the lifetime of the silicon substrate before hydrofluoric acid treatment was measured. Using a lifetime measuring device (trade name: WCT-120, manufactured by Sinton Instruments), the measurement was performed by the QSSPC method (pseudo steady state photoconductivity measurement method). The lifetime at an excess carrier density of 1 × 10 ¹⁵ cm ⁻³ was 125 μs.

[Example 2]
The same procedure as in Example 1 was performed except that a glass having a composition molar ratio of B ₂ O ₃ , SiO ₂ , Al ₂ O ₃ and BaO of 40 mol%, 40 mol%, 10 mol% and 10 mol% was used. The sheet resistance of the coating part is 51 Ω / sq. A p-type diffusion layer was formed. The lifetime was 130 μs.

[Example 3]
B ₂ O _3, the composition molar ratio of BaSO _4, respectively 90 mol%, so as to _{10mol%, B 2 O 3,} BaSO 4 ( all, manufactured by Kojundo Chemical Laboratory, Ltd.) was weighed, in an agate mortar Mixed. Thereafter, terpineol was added and dispersed with a planetary ball mill to prepare a B ₂ O ₃ + BaSO ₄ / terpineol solution. At this time, the total solid content of B ₂ O ₃ and BaSO ₄ was 30% by mass. Next, this solution and ethyl cellulose / terpineol are mixed and mixed to form a paste so that the total mass of B ₂ O ₃ and BaSO ₄ is 10 mass%, ethyl cellulose is 6 mass%, and terpineol is 84 mass%. A p-type diffusion layer forming composition was prepared.
The sheet resistance of the coating part is 51 Ω / sq. A p-type diffusion layer was formed. The lifetime was 105 μs.

[Example 4]
In Example 3, instead of B ₂ O _3, except for using boric acid (manufactured by Wako Pure Chemical Industries, Ltd.) is as in Example 3. The sheet resistance of the coating part is 53Ω / sq. A p-type diffusion layer was formed. The lifetime was 115 μs.

[Example 5]
In Example 3, instead of B ₂ O _3, boron nitride (Denki Kagaku Kogyo, trade name: GP) except for using is as in Example 3. The sheet resistance of the coating part is 53Ω / sq. A p-type diffusion layer was formed. The lifetime was 115 μs.

[Example 6]
In Example 3, instead of BaSO _4, except for using BaO (manufactured by Kojundo Chemical Laboratory Co., Ltd.) were the same as in Example 3. The sheet resistance of the coating part is 49Ω / sq. A p-type diffusion layer was formed. The lifetime was 111 μs.

[Example 7]
In Example 3, instead of BaSO _4, except for using BaCO ₃ (manufactured by Kojundo Chemical Laboratory Co., Ltd.) is as in Example 3. The sheet resistance of the coating part is 55 Ω / sq. A p-type diffusion layer was formed. The lifetime was 121 μs.

[Example 8]
(Synthesis of glass particles)
B ₂ O _3, the composition molar ratio of _SiO 2, _Al 2 _{O 3} and CaO, respectively 30 mol%, 50 mol%, so that 10 mol% and _{10mol%, B 2 O 3,} SiO 2, Al 2 O 3 and CaSO ₄ (all manufactured by Kojundo Chemical Laboratory Co., Ltd.) was weighed, mixed in an agate mortar, placed in a platinum crucible, held at 1500 ° C. for 2 hours in a glass melting furnace, and then rapidly cooled to a glass lump. Got. This was ground in an agate mortar.
_{Then, B 2 O 3, SiO 2} , Al 2 O 3 and composition molar ratio of BaO, respectively 30 mol%, 50 mol%, so that 10 mol% and _{10mol%, B 2 O 3,} SiO 2, Al 2 O ₃ and BaO (all manufactured by Kojundo Chemical Laboratory Co., Ltd.) were weighed, mixed in an agate mortar, placed in a platinum crucible, held at 1500 ° C. for 2 hours in a glass melting furnace, and then rapidly cooled to glass. A lump was obtained. This was ground in an agate mortar.
Synthesized _B 2 _O 3 ground by -SiO ₂ -Al ₂ O ₃ -CaO glass and _{B 2 O 3 -SiO 2 -Al 2} O 3 -BaO glass a planetary ball mill, and dispersed. In this _{case, B 2 O 3 -SiO 2 -Al} 2 O 3 -CaO glass and _{B 2 O 3 -SiO 2 -Al 2} O 3 -BaO mixing ratio of the glass was made to be 50:50 (weight%) . 10 g, 6 g and 84 g of the mixed glass particles, ethyl cellulose and terpineol were mixed to form a paste to prepare a p-type diffusion layer forming composition.
The rest was evaluated in the same manner as in Example 1. The sheet resistance of the coating part is 52 Ω / sq. A p-type diffusion layer was formed. The lifetime was 135 μs.

[Example 9]
Polyvinyl alcohol (molecular weight 10,000, partially saponified type, manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in water to prepare a 10% polyvinyl alcohol aqueous solution. 8 g of this solution, 1.5 g of boric acid (manufactured by Wako Pure Chemical Industries, Ltd.), 0.1 g of barium oxide (manufactured by Wako Pure Chemical Industries, Ltd.), fumed silica (manufactured by Nippon Aerosil Co., Ltd., trade name: R200) 0.1 g of surfactant (silicone surfactant, manufactured by Toray Dow Corning Co., Ltd., trade name: SH28PA) was mixed with an automatic mortar kneader to prepare a p-type diffusion layer forming composition. . Evaluation was performed in the same manner as in Example 1 except that this p-type diffusion layer forming composition was used. The lifetime was 105 μs.

[Example 10]
B ₂ O _3, the composition molar ratio of BaSO _4, respectively 99 mol%, so as to _{1mol%, B 2 O 3,} BaSO 4 ( all, manufactured by Kojundo Chemical Laboratory, Ltd.) was weighed, in an agate mortar Mixed. Thereafter, terpineol was added and dispersed with a planetary ball mill to prepare a B ₂ O ₃ + BaSO ₄ / terpineol solution. At this time, the total solid content of B ₂ O ₃ and BaSO ₄ was 30% by mass. Next, this solution is mixed with ethyl cellulose / terpineol, and mixed and pasted so that the total mass% of B ₂ O ₃ and BaSO ₄ is 10 mass%, ethyl cellulose is 6 mass%, and terpineol is 84 mass%. And a p-type diffusion layer forming composition was prepared.
The sheet resistance of the coating part is 48Ω / sq. A p-type diffusion layer was formed. The lifetime was 85 μs.

[Comparative Example 1]
In Example 3, the procedure was the same except that BaSO ₄ was not added. The sheet resistance of the coating part is 50Ω / sq. A p-type diffusion layer was formed. The lifetime was 25 μs.

[Comparative Example 2]
The same procedure as in Example 1 was performed except that a glass having a composition molar ratio of B ₂ O ₃ , SiO ₂ , Al ₂ O _3, and CaO of 40 mol%, 40 mol%, 10 mol%, and 10 mol% was used. The sheet resistance of the coating part is 46 Ω / sq. A p-type diffusion layer was formed. The lifetime was 20 μs.

DESCRIPTION OF SYMBOLS 10 ... p-type semiconductor substrate, 11 ... n-type diffusion layer forming composition, 12 ... heat-treated product (baked product) of n-type diffusion layer forming composition, 13 ... first n-type diffusion layer, 14 ... PSG (phosphorus silicate) Glass) layer, 15 ... second n-type diffusion layer, 16 ... p-type diffusion layer forming composition, 17 ... p ⁺ type diffusion layer, 18 ... antireflection film, 19 ... passivation layer, 20 ... light-receiving surface electrode, 21 ... back electrode, 30 ... n-type semiconductor substrate, 31 ... p-type diffusion layer forming composition, 31 '... heat-treated product (baked product) of p-type diffusion layer forming composition, 32 ... p-type diffusion layer, 33 ... mask layer 34 ... n-type diffusion layer forming composition, 34 '... heat-treated product (baked product) of n-type diffusion layer forming composition, 35 ... n ⁺ type diffusion layer, 36 ... passivation layer, 37 ... p electrode, 38 ... n electrode

Claims (11)

  A p-type diffusion layer forming composition containing a compound containing an acceptor element, a barium compound, and a dispersion medium.   A p-type diffusion layer forming composition containing a compound containing an acceptor element and a dispersion medium, wherein the compound containing the acceptor element contains barium.   The p-type diffusion layer forming composition according to claim 1, wherein the acceptor element is boron. The p-type diffusion layer forming composition according to any one of claims 1 to 3, wherein the compound containing the acceptor element is at least one boron compound selected from boric acid, boric acid ester, and B ₂ O ₃ .   The p-type diffusion layer forming composition according to any one of claims 1 to 4, wherein the compound containing the acceptor element is a glass compound. Including glass further containing at least one glass component selected from Al ₂ O ₃ , SiO ₂ , K ₂ O, Na ₂ O, Li ₂ O, SrO, CaO, MgO, BeO, ZnO and ZrO ₂ The p-type diffusion layer forming composition according to claim 5. The p-type diffusion layer forming composition according to claim 1, wherein the barium compound is at least one selected from BaO, BaSO ₄ , BaCO ₃ , and Ba (OH) ₂ .   The p-type diffusion layer forming composition according to any one of claims 1 to 7, wherein a ratio of the barium compound contained in the p-type diffusion layer forming composition is 0.01% by mass or more and 50% by mass or less.   The p-type diffusion layer forming composition according to any one of claims 1 to 8, wherein a proportion of a barium compound contained in the p-type diffusion layer forming composition is 0.05% by mass or more and 30% by mass or less.   The p-type diffusion layer forming composition according to any one of claims 1 to 9, wherein a ratio of a barium compound contained in the p-type diffusion layer forming composition is 0.1% by mass or more and 10% by mass or less. Applying a p-type diffusion layer forming composition according to any one of claims 1 to 10 on a semiconductor substrate;
Applying a thermal diffusion treatment to form a p-type diffusion layer;
The manufacturing method of the solar cell element which has this.

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