JP2015179866A - P-type diffusion layer formation composition, and solar cell and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a p-type diffusion layer formation composition capable of forming a p-type diffusion layer and a back electrode while suppressing occurrences of internal stress in a silicon substrate and substrate warpage, in a manufacturing process of a solar cell using a crystal silicon substrate, and to provide a solar cell formed by using the p-type diffusion layer formation composition.SOLUTION: A p-type diffusion layer formation composition includes: metal particles; glass particles containing an acceptor element; a resin; and a solvent. A solar cell is provided with a p-type diffusion layer and an electrode that are formed by heat treatment after the p-type diffusion layer formation composition is applied on a semiconductor substrate.

Description

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

In the manufacturing process of a conventional crystalline silicon solar cell, a p-type silicon substrate having a textured structure is prepared so as to promote the light confinement effect and achieve high efficiency, followed by phosphorus oxychloride (POCl ₃ ), nitrogen Then, several tens of minutes of treatment is performed at 800 to 900 ° C. in an oxygen mixed gas atmosphere to uniformly form an n-type diffusion layer on the substrate. In this conventional method, since phosphorus is diffused using a mixed gas, n-type diffusion layers are formed not only on the surface but also on the side surface and the back surface. Therefore, side etching is performed to remove the n-type diffusion layer on the side surface. Further, the back surface of the n-type diffusion layer must be converted into the p ⁺ -type diffusion layer, an aluminum paste is printed on the back, by firing this, the n-type diffusion layer at the same time as the p ⁺ -type diffusion layer , Got ohmic contact.

  However, the aluminum paste has a low electrical conductivity, and in order to reduce the sheet resistance, the aluminum layer usually formed on the entire back surface must have a thickness of 30 μm or more after firing. Furthermore, when a thick aluminum layer is formed in this way, the thermal expansion coefficient differs greatly between silicon and aluminum, so that a large internal stress is generated in the silicon substrate during the firing and cooling process, resulting in damage to the grain boundaries, In some cases, defects increased and warped.

In order to solve this problem, there is a method of reducing the coating amount of the paste composition and thinning the back electrode layer. However, when the application amount of the paste composition is reduced, the amount of aluminum diffusing from the surface of the p-type silicon semiconductor substrate 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) cannot be achieved, resulting in a problem that the characteristics of the solar cell deteriorate. .

  Therefore, for example, a paste composition comprising aluminum powder, an organic vehicle, and an inorganic compound powder having a thermal expansion coefficient smaller than that of aluminum and any one of a melting temperature, a softening temperature and a decomposition temperature higher than the melting point of aluminum. Has been proposed (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 2003-223813

However, even when the paste composition described in Patent Document 1 is used, there is a case where warpage cannot be sufficiently suppressed.
The present invention has been made in view of the above-described conventional problems, and in the manufacturing process of a solar battery cell using a crystalline silicon substrate, the p-type is suppressed while suppressing internal stress in the silicon substrate and warping of the substrate. It is an object of the present invention to provide a p-type diffusion layer forming composition capable of forming a diffusion layer and an electrode, a method for producing a solar cell using the composition, and a solar cell produced by the production method.

<1> A p-type diffusion layer forming composition containing metal particles, glass particles containing an acceptor element, a resin, and a solvent.
<2> The p-type diffusion layer forming composition according to <1>, wherein the acceptor element is at least one selected from B (boron), Al (aluminum), and Ga (gallium).
<3> The glass particles include at least one acceptor element-containing material selected from B ₂ O ₃ , Al ₂ O ₃ and Ga ₂ O ₃ , and SiO ₂ , K ₂ O, Na ₂ O, Li ₂ O. And at least one glass component material selected from BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, V ₂ O ₅ , Tl ₂ O ₃ , SnO, ZrO ₂ , and MoO ₃ The p-type diffusion layer forming composition according to <1> or <2>.
<4> The p-type diffusion layer forming composition according to <3>, wherein a content ratio of the acceptor element-containing substance in the glass particles is 1% by mass or more and 80% by mass or less.
<5> The p-type diffusion layer forming composition according to any one of <1> to <4>, wherein the metal particles are at least one selected from silver particles and silver-coated copper particles.

<6> The step of applying the p-type diffusion layer forming composition according to any one of <1> to <5> on the semiconductor substrate, and the formation of the p-type diffusion layer and the electrode by heat treatment And a heat treatment step for performing a solar cell manufacturing method.
<7> A p-type diffusion layer and an electrode formed by applying the p-type diffusion layer forming composition according to any one of <1> to <5> on a semiconductor substrate and heat-treating the composition. Solar cell provided.

  According to the present invention, in a manufacturing process of a solar battery cell using a crystalline silicon substrate, p-type diffusion layers and electrodes can be formed while suppressing the occurrence of internal stress in the silicon substrate and warping of the substrate. A mold diffusion layer forming composition, a method for producing a solar cell using the composition, and a solar cell produced by the production method can be provided.

In the present invention, the term “process” is not limited to an independent process, and is included in the term if the intended action of the process is achieved even when it cannot be clearly distinguished from other processes.
In the present specification, “to” indicates a range including numerical values described before and after that as a minimum value and a maximum value, respectively.

<P-type diffusion layer forming composition>
The p-type diffusion layer forming composition of the present invention includes at least one metal particle, at least one glass particle containing an acceptor element, at least one resin, and at least one solvent, and is necessary. Depending on the configuration, other components are included.
With such a configuration, it is possible to form a p-type diffusion layer only in a specific portion during the heat treatment when forming the electrode.

[Metal particles]
The p-type diffusion layer forming composition of the present invention contains at least one metal particle. The metal particles are not particularly limited as long as they can form electrodes by firing, and examples thereof include silver particles, copper-containing particles, platinum-containing particles, palladium-containing particles, and cobalt-containing particles.
The metal particles preferably include silver particles alone or at least one of silver particles and copper-containing particles.

(Silver particles)
The p-type diffusion layer forming composition of the present invention preferably contains at least one silver particle as metal particles. By including silver particles, the resistivity as an electrode to be formed is further reduced. Furthermore, the effect that the solder connection property at the time of setting it as a solar cell module improves is also acquired.

  The silver which comprises the said silver particle may contain the other atom mixed unavoidable. Examples of other atoms inevitably mixed include Sb, Si, K, Na, Li, Ba, Sr, Ca, Mg, Be, Zn, Pb, Cd, Tl, V, Sn, Al, Zr, and Mo. , Ti, Co and the like.

  The particle diameter of the silver particles in the present invention is not particularly limited, but the particle diameter (D50%) when the accumulated weight is 50% is preferably 0.4 μm or more and 10 μm or less, and 1 μm or more and 7 μm or less. It is more preferable that When the thickness is 0.4 μm or more, the connection resistance with the semiconductor is further reduced. Moreover, the contact area of metal particles, such as a silver particle and copper containing particle | grains in an electrode, becomes large because it is 10 micrometers or less, and resistivity falls more effectively. The particle size of the silver particles is measured by a microtrack particle size distribution measuring device (manufactured by Nikkiso Co., Ltd., MT3300 type).

  Further, the shape of the silver particles is not particularly limited and may be any of a substantially spherical shape, a flat shape, a block shape, a plate shape, a scale shape, and the like. Or a plate-like shape.

  Moreover, as content rate of the silver particle in the p-type diffused layer formation composition of this invention, from a viewpoint of the low resistivity of the electrode formed, 8.4-85.5 mass with respect to the p-type diffused layer formation composition. %, And more preferably 8.9 to 80.1% by mass.

(Copper-containing particles)
The copper-containing particles in the present invention are not particularly limited as long as an electrode can be formed by heat treatment. Specifically, for example, at least one selected from the group consisting of silver-coated copper particles, triazole compounds, saturated fatty acids, unsaturated fatty acids, inorganic metal compound salts, organometallic compound salts, polyaniline resins, and metal alkoxides. Surface-treated copper particles and phosphorus-containing copper alloy particles can be mentioned, and at least one selected from these is preferably used, and at least selected from silver-coated copper particles and surface-treated copper particles. It is more preferable to use one type. The copper-containing particles may be used alone or in combination of two or more.

Although there is no restriction | limiting in particular as a particle diameter of the said copper containing particle | grains, It is 0.4-10 micrometers as a particle diameter (Hereinafter, it may abbreviate as "D50%.") When the integrated weight is 50%. Is preferable, and it is more preferable that it is 1-7 micrometers. When the thickness is 0.4 μm or more, the oxidation resistance is more effectively improved. Moreover, the contact area of the copper containing particles in an electrode becomes large because it is 10 micrometers or less, and a resistivity falls more effectively. The particle diameter of the copper-containing particles is measured by a microtrack particle size distribution measuring device (manufactured by Nikkiso Co., Ltd., MT3300 type).
Further, the shape of the copper-containing particles is not particularly limited, and may be any of a substantially spherical shape, a flat shape, a block shape, a plate shape, a scale shape, and the like, from the viewpoint of oxidation resistance and low resistivity, It is preferably substantially spherical, flat, or plate-shaped.

As content rate of the said copper containing particle | grains contained in the p-type diffused layer formation composition of this invention, and the total content rate of the copper containing particle | grains and silver particle in the case of containing the above-mentioned silver particle, 70-94 mass is, for example From the viewpoint of oxidation resistance and low resistivity, the content is preferably 72 to 90% by mass, and more preferably 74 to 88% by mass.
In the present invention, conductive particles other than the copper-containing particles may be used in combination.

-Silver-coated copper particles-
As the silver-coated copper particles in the present invention, it is sufficient that at least a part of the surface of the copper particles is coated with silver. By using silver-coated copper particles as the copper-containing particles contained in the p-type diffusion layer forming composition of the present invention, an electrode having excellent oxidation resistance and low resistivity can be formed. Furthermore, since the copper particles are coated with silver, the interface resistance between the silver-coated copper particles and the silver particles is reduced, and an electrode with a lower resistivity can be formed. Furthermore, when the p-type diffusion layer forming composition is used, when moisture is mixed, by using the silver-coated copper particles, it is possible to suppress the oxidation of copper at room temperature and to improve the pot life. it can.

  The silver coating amount (silver content) in the silver-coated copper particles is not particularly limited. Specifically, for example, it is 1% by mass or more with respect to the total mass of the silver-coated copper particles, but 1 to 88 with respect to the total mass of the silver-coated copper particles from the viewpoint of oxidation resistance and low resistivity of the electrode. The mass is preferably 3% by mass, more preferably 3 to 80% by mass, and even more preferably 5 to 75% by mass.

The particle diameter of the silver-coated copper particles is not particularly limited, but the particle diameter when the accumulated weight is 50% (hereinafter sometimes abbreviated as “D50%”) is 0.4 μm to 10 μm. It is preferable that it is 1-7 micrometers. When the thickness is 0.4 μm or more, the oxidation resistance is more effectively improved. Moreover, the contact area of the silver covering copper particle in an electrode becomes large because it is 10 micrometers or less, and a resistivity falls more effectively.
Further, the shape of the silver-coated copper particles is not particularly limited and may be any of a substantially spherical shape, a flat shape, a block shape, a plate shape, a scale shape, and the like, from the viewpoint of oxidation resistance and low resistivity. It is preferably substantially spherical, flat or plate-like.

  Copper constituting the silver-coated copper particles may contain other atoms inevitably mixed. Examples of other atoms inevitably mixed include Sb, Si, K, Na, Li, Ba, Sr, Ca, Mg, Be, Zn, Pb, Cd, Tl, V, Sn, Al, Zr, and Mo. , Ti, Co and the like.

The method for preparing the silver-coated copper particles is not particularly limited as long as at least a part of the surface of the copper particles can be coated with silver. For example, copper powder is dispersed in an acidic solution such as sulfuric acid or hydrochloric acid, and a chelating agent is added to the copper powder dispersion to prepare a copper powder slurry. By adding a silver ion solution to the obtained copper powder slurry, a silver layer can be formed on the surface of the copper powder by a substitution reaction.
Although there is no restriction | limiting in particular as said chelating agent, For example, ethylenediaminetetraacetic acid salt, triethylenediamine, diethylenetriaminepentaacetic acid, iminodiacetic acid, etc. can be used. Moreover, as a silver ion solution, a silver nitrate solution etc. can be used, for example.

The total content of the silver-coated copper particles and the silver particles when the silver-coated copper particles are contained in the p-type diffusion layer forming composition of the present invention and the silver particles described above are included, for example, 70 to From the viewpoint of oxidation resistance and low resistivity, it is preferably 72 to 90% by mass, and more preferably 74 to 88% by mass.
In the present invention, the silver-coated copper particles may be used singly or in combination of two or more.

In the present invention, from the viewpoint of oxidation resistance and low resistivity of the electrode, the silver-coated copper particles having a silver content of 1 to 88% by mass relative to the total mass of the silver-coated copper particles are used as a p-type diffusion layer forming composition. 70 to 94% by mass (when silver particles are included, the total content of silver-coated copper particles and silver particles) is preferably included, and the silver-coated copper particles having a silver content of 5 to 75% by mass Is more preferably 74 to 88% by mass (when silver particles are included, the total content of silver-coated copper particles and silver particles) with respect to the p-type diffusion layer forming composition.
In the present invention, conductive particles other than the silver-coated copper particles may be used in combination.

-Surface treated copper particles-
The copper-containing particles in the present invention are a group consisting of a triazole compound, a saturated fatty acid, an unsaturated fatty acid, an inorganic metal compound salt, an organic metal compound salt, a polyaniline resin, and a metal alkoxide (hereinafter sometimes referred to as “surface treatment agent”). It is also preferable that the copper particles are surface-treated with at least one selected from the group consisting of triazole compounds, saturated fatty acids, unsaturated fatty acids, and inorganic metal compound salts. More preferably, it is a copper particle.
As the copper-containing particles contained in the p-type diffusion layer forming composition of the present invention, by using copper particles surface-treated with at least one surface treatment agent, an electrode having excellent oxidation resistance and low resistivity is formed. can do. Furthermore, when it is set as a p-type diffused layer formation composition, when a water | moisture content mixes, the effect that the oxidation of copper in room temperature can be suppressed and a pot life can be improved can be acquired by using a surface treating agent.
In the present invention, the surface treatment agents may be used singly or in combination of two or more.

  In the present invention, the surface-treated copper particles are at least one selected from the group consisting of triazole compounds, saturated fatty acids, unsaturated fatty acids, inorganic metal compound salts, organometallic compound salts, polyaniline resins, and metal alkoxides. Although it has been treated, other surface treatment agents may be used in combination as required.

Examples of the triazole compound in the surface treatment agent include benzotriazole and triazole. Examples of the saturated fatty acid in the surface treatment agent include enanthic acid, caprylic acid, pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, stearic acid, nonadecanoic acid, arachic acid, Examples include behenic acid. Examples of the unsaturated fatty acid in the surface treatment agent include acrylic acid, methacrylic acid, crotonic acid, isocrotonic acid, undecylenic acid, oleic acid, elaidic acid, cetreic acid, brassic acid, erucic acid, sorbic acid, and linoleic acid. Linolenic acid, arachidonic acid and the like.
Examples of the inorganic metal compound salt in the surface treatment agent include sodium silicate, sodium stannate, tin sulfate, zinc sulfate, sodium zincate, zirconium nitrate, sodium zirconate, zirconium chloride, titanium sulfate, and titanium chloride. And potassium oxalate titanate. Examples of the organometallic compound salt in the surface treatment agent include lead stearate, lead acetate, p-cumylphenyl derivative of tetraalkoxyzirconium, p-cumylphenyl derivative of tetraalkoxytitanium, and the like. Examples of the metal alkoxide in the surface treatment agent include titanium alkoxide, zirconium alkoxide, lead alkoxide, silicon alkoxide, tin alkoxide, and indium alkoxide.

Examples of other surface treatment agents include dodecylbenzene sulfonic acid.
When stearic acid or lead stearate is used as the surface treatment agent, the oxidation resistance is further improved and the resistivity is improved by using at least one of stearic acid and lead stearate and lead acetate as the surface treatment agent. Lower electrodes can be formed.

  In the surface-treated copper particles in the present invention, it is sufficient that at least a part of the surface of the copper particles is coated with at least one kind of the surface treatment agent. There is no restriction | limiting in particular as content of the surface treating agent contained in the surface-treated copper particle. Specifically, it is 0.01% by mass or more based on the total mass of the surface-treated copper particles, but 0.01% based on the total mass of the copper particles from the viewpoint of oxidation resistance and low resistivity of the electrode. It is preferable that it is -10 mass%, and it is more preferable that it is 0.05-8 mass%.

  The copper constituting the surface-treated copper particles may contain other atoms inevitably mixed. Examples of other atoms inevitably mixed include Sb, Si, K, Na, Li, Ba, Sr, Ca, Mg, Be, Zn, Pb, Cd, Tl, V, Sn, Al, Zr, and Mo. , Ti, Co and the like.

The particle diameter of the surface-treated copper particles is not particularly limited, but the particle diameter when the accumulated weight is 50% (hereinafter sometimes abbreviated as “D50%”) is 0.4 μm to The thickness is preferably 10 μm, more preferably 1 μm to 7 μm. When the thickness is 0.4 μm or more, the oxidation resistance is more effectively improved. Moreover, the contact area of the said surface-treated copper particle in an electrode becomes large because it is 10 micrometers or less, and a resistivity falls more effectively.
Further, the shape of the surface-treated copper particles is not particularly limited and may be any of a substantially spherical shape, a flat shape, a block shape, a plate shape, a scale shape, etc., but has an oxidation resistance and a low resistivity. From the viewpoint, it is preferably substantially spherical, flat, or plate-shaped.

  The surface treatment method of the copper particles using the surface treatment agent can be appropriately selected according to the surface treatment agent to be used. For example, by preparing a surface treatment solution in which the surface treatment agent is dissolved in a solvent capable of dissolving the surface treatment agent, and immersing and drying the copper particles in this, at least a part of the surface of the copper particles is coated with the surface treatment agent. Can be coated.

The solvent capable of dissolving the surface treatment agent can be appropriately selected according to the surface treatment agent. For example, water, alcohol solvents such as methanol, ethanol, isopropanol, glycol solvents such as ethylene glycol monoethyl ether, carbitol solvents such as diethylene glycol monobutyl ether, carbitol acetate solvents such as diethylene glycol monoethyl ether acetate, etc. Can be mentioned.
Specifically, for example, when benzotriazole, triazole, or dodecylbenzene sulfonic acid is used as the surface treatment agent, a surface treatment solution can be prepared using an alcohol solvent to treat the copper particles.
When stearic acid or lead stearate is used as the surface treatment agent, a surface treatment solution can be prepared using an alcohol solvent.

  The concentration of the surface treatment agent in the surface treatment solution can be appropriately selected according to the type of surface treatment agent used and the desired surface treatment amount. For example, it can be 1-90 mass%, and it is preferable that it is 2-85 mass%.

As the content of the surface-treated copper particles contained in the p-type diffusion layer forming composition of the present invention, and the total content of the surface-treated copper particles and silver particles in the case of containing silver particles described later, for example, 70 to 94% by mass, and from the viewpoint of oxidation resistance and low resistivity, it is preferably 72 to 90% by mass, and more preferably 74 to 88% by mass.
In the present invention, the surface-treated copper particles may be used singly or in combination of two or more.

In the present invention, from the viewpoint of oxidation resistance and low resistivity of the electrode, it is selected from the group consisting of triazole compounds, saturated fatty acids, unsaturated fatty acids, inorganic metal compound salts, organometallic compound salts, polyaniline resins, and metal alkoxides. The copper particles surface-treated so that at least one kind contained is contained in an amount of 0.01 to 10% by mass, based on the p-type diffusion layer forming composition, 70 to 94% by mass (when silver particles are included, the surface treatment is performed). The total content of copper particles and silver particles) is preferably included, and 0.05 to 8% by mass of at least one selected from the group consisting of triazole compounds, saturated fatty acids, unsaturated fatty acids, and inorganic metal compound salts is included. The surface-treated copper particles are 74 to 88% by mass with respect to the p-type diffusion layer forming composition (when silver particles are included, the total content of the surface-treated copper particles and silver particles) Mukoto is more preferable.
In the present invention, conductive particles other than the surface-treated copper particles may be used in combination.

-Phosphorus-containing copper alloy particles-
As a phosphorus-containing copper alloy, a brazing material called phosphorus copper brazing (phosphorus concentration: about 7% by mass or less) is known. Phosphorus copper brazing is also used as a bonding agent between copper and copper, but phosphorus-containing copper alloy particles can be used as the copper-containing particles contained in the p-type diffusion layer forming composition of the present invention.

There is no restriction | limiting in particular as phosphorus content rate contained in the phosphorus containing copper alloy in this invention. Specifically, it is 0.01% by mass or more based on the total mass of the phosphorus-containing copper alloy particles. In the present invention, from the viewpoint of oxidation resistance and low resistivity, it is preferably 0.01% by mass or more and 8% by mass or less, and more preferably 0.5% by mass or more and 7.8% by mass or less. More preferably, it is 1 mass% or more and 7.5 mass% or less.
When the phosphorus content contained in the phosphorus-containing copper alloy is 8% by mass or less, a lower resistivity can be achieved, and the productivity of the phosphorus-containing copper alloy is excellent. Moreover, the more outstanding acid resistance can be achieved because it is 0.01 mass% or more.

  The phosphorus-containing copper alloy particles are an alloy containing copper and phosphorus, but may further contain other atoms inevitably mixed therein. Examples of other atoms inevitably mixed include Sb, Si, K, Na, Li, Ba, Sr, Ca, Mg, Be, Zn, Pb, Cd, Tl, V, Sn, Al, Zr, and Mo. , Ti, Co and the like.

The particle diameter of the phosphorus-containing copper alloy particles is not particularly limited, but the particle diameter when the accumulated weight is 50% (hereinafter sometimes abbreviated as “D50%”) is 0.4 to 10 μm. It is preferably 1 to 7 μm. When the thickness is 0.4 μm or more, the oxidation resistance is more effectively improved. Moreover, the contact area of the phosphorus containing copper alloy particles in an electrode becomes large because it is 10 micrometers or less, and a resistivity falls more effectively.
The shape of the phosphorus-containing copper alloy particles is not particularly limited, and may be any of a substantially spherical shape, a flat shape, a block shape, a plate shape, a scale shape, and the like, but from the viewpoint of oxidation resistance and low resistivity. Therefore, it is preferably substantially spherical, flat, or plate-shaped.

The phosphorous copper alloy can be produced by a commonly used method. Also, the phosphorus-containing copper alloy particles can be prepared using a normal method of preparing metal powder using a phosphorus-containing copper alloy prepared so as to have a desired phosphorus content, for example, a water atomization method Can be produced by a conventional method. The water atomization method is described in Metal Handbook (Maruzen).
Specifically, for example, after phosphorus-containing copper alloy is dissolved and powdered by nozzle spray, the obtained powder is dried and classified, whereby desired phosphorus-containing copper alloy particles can be produced. Moreover, the phosphorus containing copper alloy particle | grains which have a desired particle diameter can be manufactured by selecting classification conditions suitably.

As the content rate of the phosphorus-containing copper alloy particles contained in the p-type diffusion layer forming composition of the present invention, and the total content rate of the phosphorus-containing copper alloy particles and silver particles in the case of containing silver particles described later, for example, 70 It can be -94 mass%, and it is preferable that it is 72-90 mass% from a viewpoint of oxidation resistance and a low resistivity, and it is more preferable that it is 74-88 mass%.
In the present invention, the phosphorus-containing copper alloy particles may be used singly or in combination of two or more.

Furthermore, in the present invention, from the viewpoint of oxidation resistance and low resistivity of the electrode, phosphorus-containing copper alloy particles having a phosphorus content of 0.01% by mass or more and 8% by mass or less are used as the p-type diffusion layer forming composition. It is preferable to contain 70-94 mass% with respect to a p-type diffused layer formation composition, and it is preferable to contain 74-88 mass% of phosphorus containing copper alloy particles whose phosphorus content rate is 1-7.5 mass%. More preferred.
In the present invention, conductive particles other than the phosphorus-containing copper alloy particles may be used in combination.

  It is also preferable that the p-type diffusion layer forming composition of the present invention contains at least one silver particle and at least one copper-containing particle. By containing silver particles in addition to the copper-containing particles, the oxidation resistance is further improved, and the resistivity as an electrode is further reduced. Furthermore, the effect that the solder connection property at the time of setting it as a solar cell module improves is also acquired. This can be considered as follows, for example.

  In general, in a temperature range of 600 ° C. to 900 ° C., which is an electrode formation temperature range, a small amount of silver is dissolved in copper and a small amount of copper is dissolved in silver, and copper is formed at the interface between copper and silver. -A silver solid solution layer (solid solution region) is formed. When a mixture of copper-containing particles and silver particles is heated to a high temperature and then slowly cooled to room temperature, it is considered that a solid solution region does not occur, but at the time of electrode formation, it is cooled from the high temperature region to room temperature in a few seconds. It is thought that the solid solution layer in FIG. 4 covers the surface of the silver particles and the copper-containing particles as a non-equilibrium solid solution phase or a eutectic structure of copper and silver. Such a copper-silver solid solution layer can be considered to contribute to the oxidation resistance of the copper-containing particles at the electrode formation temperature.

  The copper-silver solid solution layer starts to be formed at a temperature of 300 ° C. to 500 ° C. or higher. Therefore, by using silver particles together with copper-containing particles having a peak temperature of an exothermic peak showing a maximum area in differential thermal-thermogravimetric simultaneous measurement of 280 ° C. or more, the oxidation resistance of the copper-containing particles can be more effectively improved. It can be considered that the resistivity of the formed electrode is further reduced.

  In the p-type diffusion layer forming composition of the present invention, the relationship between the particle diameter of the copper-containing particles (D50%) and the particle diameter of the silver particles (D50%) is not particularly limited, but either one of the particle diameters (D50%) is preferably smaller than the other particle diameter (D50%), and the ratio of the other particle diameter to one of the particle diameters is more preferably 1 to 10. Thereby, the resistivity of an electrode falls more effectively. This can be attributed to, for example, an increase in contact area between metal particles such as copper-containing particles and silver particles in the electrode.

In the present invention, from the viewpoint of oxidation resistance and low resistivity of the electrode, the content of the copper-containing particles is 9 to 88% by mass when the total amount of the copper-containing particles and the silver particles is 100% by mass. Is more preferable, and it is more preferably 17 to 77% by mass.
When the content of the copper-containing particles is 9% by mass or more, for example, in the hydrofluoric acid aqueous solution treatment of the electrode-formed silicon substrate for the purpose of improving the energy conversion efficiency when a solar cell is formed, the hydrofluoric acid resistance of the electrode material Aqueous property (property that electrode material is not peeled off from silicon substrate by hydrofluoric acid aqueous solution) is improved.
Moreover, it becomes more suppressed that the content rate of the said copper containing particle | grain becomes 88 mass% or less, and the copper contained in a copper containing particle | grain contacts a silicon substrate, and the contact resistance of an electrode falls more.

  In the p-type diffusion layer forming composition of the present invention, the total content of the copper-containing particles and the silver particles is 70% by mass from the viewpoints of oxidation resistance, low resistivity of the electrode, and applicability to the silicon substrate. The content is preferably 94% by mass or less and more preferably 74% by mass or more and 88% by mass or less. When the total content of the copper-containing particles and the silver particles is 70% by mass or more, a suitable viscosity can be easily achieved when the p-type diffusion layer forming composition is applied. Moreover, generation | occurrence | production of the blurring at the time of providing a p-type diffused layer formation composition can be suppressed more effectively because the total content of the said copper containing particle | grains and the said silver particle is 94 mass% or less.

  Furthermore, in the p-type diffusion layer forming composition of the present invention, from the viewpoint of oxidation resistance and low resistivity of the electrode, the total content of the copper-containing particles and the silver particles is 70% by mass or more and 94% by mass or less. The glass particle content described later is 0.1% by mass or more and 10% by mass or less, and the total content of the solvent described later and the resin described later is preferably 3% by mass or more and 30% by mass or less. The total content of copper-containing particles and silver particles is 74% by mass or more and 88% by mass or less, the content of glass particles is 0.5% by mass or more and 8% by mass or less, and the total content of solvent and resin Is more preferably 7% by mass or more and 20% by mass or less, and the total content of copper-containing particles and silver particles is 74% by mass or more and 88% by mass or less, and the content of glass particles is 1% by mass or more and 7% by mass. Less than mass%, solvent and resin It is more preferable that the total content of 20 mass% or less 7 mass% or more.

[Glass particles]
The p-type diffusion layer forming composition of the present invention contains at least one glass particle containing an acceptor element. When the glass particles contain an acceptor element, a p-type diffusion layer or a p ⁺ -type diffusion layer is formed on the silicon substrate at the electrode formation temperature, and an ohmic contact between the electrode and the silicon substrate is formed.
The glass particles can be composed of, for example, an acceptor element-containing material and a glass component material.

  An acceptor element is an element that can form a p-type diffusion layer by doping into a silicon substrate. As the acceptor element, a Group 13 element can be used, and examples thereof include B (boron), Al (aluminum), and Ga (gallium).

Examples of the acceptor element-containing material used for introducing the acceptor element into the glass particles include B ₂ O ₃ , Al ₂ O ₃ , and Ga ₂ O ₃ , and B ₂ O ₃ , Al ₂ O _3, and Ga ₂ O. It is preferable to use at least one selected from ₃ .

The glass particles can be controlled in terms of melting temperature, softening point, glass transition point, chemical durability, etc. by adjusting the component ratio as necessary. Furthermore, it is preferable to contain the glass component substance described below.
Examples of glass component materials include SiO ₂ , K ₂ O, Na ₂ O, Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, Tl ₂ O, V ₂ O ₅ , SnO, and ZrO _2. , MoO ₃ , La ₂ O 3, Nb ₂ O ₅ , Ta ₂ O ₅ , Y ₂ O ₃ , TiO ₂ , GeO ₂ , TeO ₂ and Lu ₂ O _3, etc., SiO ₂ , K ₂ O, Na ₂ Use of at least one selected from O, Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, V ₂ O ₅ , Tl ₂ O, SnO, ZrO ₂ , and MoO _{3 preferably, SiO 2, K 2 O,} Na 2 O, Li 2 O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, Tl 2 O, SnO, ZrO 2, and MoO More preferably, at least one selected from ₃ is used.

Specific examples of the glass particles containing an acceptor element include B ₂ O ₃ —SiO ₂ system, B ₂ O ₃ —ZnO system, B ₂ O ₃ —PbO system, Al ₂ O ₃ —SiO ₂ system, and B ₂ O _3. -al ₂ O _{3 system,} Ga ₂ O 3 -SiO _{2 system, Ga 2 O 3 -B 2 O} 3 based _glass particles, and the like made of glass such as B 2 _{O 3} alone system.
In the above, the single component glass or the composite glass containing two components is exemplified, but three or more types of composite glass such as B ₂ O ₃ —SiO ₂ —Na ₂ O may be used as necessary.

  The content ratio of the acceptor element-containing substance in the glass particle is 1% by mass or more in consideration of the doping concentration of the acceptor element in the silicon substrate, the melting temperature of the glass particle, the softening point, the glass transition point, and the chemical durability. It is preferable that it is 80 mass% or less.

  When the content ratio of the acceptor element-containing substance in the glass particles is less than 1% by mass, the doping concentration of the acceptor element into the silicon substrate may be too low, and the p-type diffusion layer may not be sufficiently formed. Further, when the content ratio of the acceptor element-containing material is larger than 80% by mass, the acceptor element-containing material may be volatilized during the thermal diffusion treatment, and the acceptor element is diffused on the side surface and the back surface. There is a possibility that the p-type diffusion layer is formed not only on the surface to which the forming composition is applied, but also on the side and back surfaces other than the desired part.

  Furthermore, the content ratio of the acceptor element-containing substance in the glass particles is preferably 2% by mass to 80% by mass, and more preferably 10% by mass to 70% by mass.

  In particular, the surface sheet having a p-type diffusion layer formed even when a certain amount or more of the acceptor element is added to the p-type diffusion layer-forming composition while taking into account the amount of the acceptor element in which the p-type diffusion layer is sufficiently formed Considering that the resistance does not decrease beyond a certain value and that the influence of volatilization of the acceptor element-containing substance needs to be suppressed, the content ratio of the acceptor element-containing substance in the glass particles is 30% by mass or more and 70% by mass. It is even more preferable that:

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

Specifically, in the case of B ₂ O ₃ —SiO ₂ glass, the content ratio of B ₂ O ₃ is preferably 1% by mass to 80% by mass, and preferably 3% by mass to 80% by mass. It is more preferable that

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

  The particle size of the glass particles is desirably 50 μm or less. When glass particles having a particle size of 50 μm or less are used, a smooth coating film can be easily obtained. Furthermore, the particle size of the glass particles is more desirably 10 μm or less.

Glass particles containing an acceptor element are produced by the following procedure.
First, weigh the ingredients and fill the crucible. Examples of the material for the crucible include platinum, platinum-rhodium, iridium, alumina, quartz, carbon, and the like, which are appropriately selected in consideration of the melting temperature, atmosphere, reactivity with the molten material, and the like.
Next, it heats with the temperature according to a glass composition with an electric furnace, and is set as a uniform melt. At this time, it is desirable to stir the melt uniformly.
Subsequently, the melt that has become uniform is poured onto a zirconia substrate, a carbon substrate, or the like to vitrify the melt.
Finally, the glass is pulverized to form powder (particulate). A known method such as a jet mill, a bead mill, or a ball mill can be applied to the pulverization.

  The content ratio of the glass particles containing the acceptor element in the p-type diffusion layer forming composition is determined in consideration of applicability, acceptor element diffusibility, and the like. In general, the content ratio of the glass particles in the p-type diffusion layer forming composition is preferably 0.1% by mass or more and 95% by mass or less, and more preferably 1% by mass or more and 90% by mass or less.

(Resin and solvent)
The p-type diffusion layer forming composition of the present invention contains at least one solvent and at least one resin. Thereby, the liquid physical properties (for example, viscosity, surface tension, etc.) of the p-type diffusion layer forming composition of the present invention can be adjusted to the required liquid physical properties depending on the application method when applying to the silicon substrate. .

  There is no restriction | limiting in particular as said solvent. For example, hydrocarbon solvents such as hexane, cyclohexane and toluene; chlorinated hydrocarbon agents such as dichloroethylene, dichloroethane and dichlorobenzene; cyclics such as tetrahydrofuran, furan, tetrahydropyran, pyran, dioxane, 1,3-dioxolane and trioxane Ether solvents; amide solvents such as N, N-dimethylformamide and N, N-dimethylacetamide; sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide; ketone solvents such as acetone, methyl ethyl ketone, diethyl ketone and cyclohexanone; ethanol; Alcohol compounds such as 2-propanol, 1-butanol and diacetone alcohol; 2,2,4-trimethyl-1,3-pentanediol monoacetate, 2,2,4-toluene Methyl-1,3-pentanediol monopropiolate, 2,2,4-trimethyl-1,3-pentanediol monobutyrate, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, Ester solvents of polyhydric alcohols such as 2,2,4-triethyl-1,3-pentanediol monoacetate, ethylene glycol monobutyl ether acetate, diethylene glycol monobutyl ether acetate; ethers of polyhydric alcohols such as butyl cellosolve and diethylene glycol diethyl ether Terpene solvents such as α-terpinene, α-terpineol, myrcene, alloocimene, limonene, dipentene, α-pinene, β-pinene, terpineol, carvone, oximene, ferrandrene, and mixtures thereof Compound may be mentioned.

Examples of the solvent in the present invention include polyhydric alcohol ester solvents, terpene solvents, and polyhydric alcohol ethers from the viewpoints of coatability and printability when a p-type diffusion layer forming composition is formed on a silicon substrate. It is preferably at least one selected from a solvent based on a solvent, and more preferably at least one selected from an ester solvent for a polyhydric alcohol and a terpene solvent.
In this invention, the said solvent may be used individually by 1 type or in combination of 2 or more types.

  As the resin, any resin that is usually used in the technical field can be used without particular limitation as long as it can be thermally decomposed by firing. Specifically, for example, cellulose resins such as methylcellulose, ethylcellulose, carboxymethylcellulose, and nitrocellulose; polyvinyl alcohols; polyvinylpyrrolidones; acrylic resins; vinyl acetate-acrylic acid ester copolymers; butyral resins such as polyvinyl butyral; phenol Examples thereof include alkyd resins such as modified alkyd resins and castor oil fatty acid modified alkyd resins; epoxy resins; phenol resins; rosin ester resins.

The resin in the present invention is preferably at least one selected from cellulosic resins and acrylic resins, more preferably at least one selected from cellulosic resins, from the viewpoint of disappearance during firing. preferable.
In this invention, the said resin may be used individually by 1 type or in combination of 2 or more types.

In the p-type diffusion layer forming composition of the present invention, the content of the solvent and the resin can be appropriately selected according to the desired liquid properties and the type of solvent and resin used. For example, the total content of the solvent and the resin is preferably 3% by mass or more and 30% by mass or less, and preferably 5% by mass or more and 25% by mass or less with respect to the total mass of the p-type diffusion layer forming composition. More preferably, it is 7 mass% or more and 20 mass% or less.
When the total content of the solvent and the resin is within the above range, the application suitability when applying the p-type diffusion layer forming composition to the silicon substrate is improved, and an electrode having a desired width and height is easier. Can be formed.

(Other ingredients)
Furthermore, the p-type diffusion layer forming composition of the present invention can further contain other components usually used in the technical field, if necessary, in addition to the components described above. Examples of other components include antioxidants, fluxes, plasticizers, dispersants, surfactants, inorganic binders, metal oxides, ceramics, and organometallic compounds.

  There is no restriction | limiting in particular as a manufacturing method of the p-type diffused layer formation composition of this invention. The metal particles, glass particles, solvent, resin, and the like can be produced by dispersing and mixing using a commonly used dispersion and mixing method.

The p-type diffusion layer forming composition of the present invention is applied on a silicon substrate, and after drying, is fired in the presence of oxygen (for example, in the air) to form a p-type diffusion layer on the silicon substrate. At the same time, an electrode having a low resistivity can be formed.
Examples of the method for applying the p-type diffusion layer forming composition on the silicon substrate include screen printing, an inkjet method, a dispenser method, and the like. From the viewpoint of productivity, the application may be performed by screen printing. preferable.

The amount of the p-type diffusion layer forming composition applied to the silicon substrate is not particularly limited, but for example, the amount of solid content applied can be 3 to 100 g / m ² . Moreover, it can also be set as the application amount from which the thickness of the electrode formed becomes 5-50 micrometers, and it is preferable that it is the application quantity which becomes 5-25 micrometers.
In addition, solid content in a p-type diffused layer formation composition means the total amount of a non-volatile component.

  When the p-type diffusion layer forming composition of the present invention is applied by screen printing, it preferably has a viscosity in the range of 80 to 1000 Pa · s. The viscosity of the p-type diffusion layer forming composition is measured at 25 ° C. using a Brookfield HBT viscometer.

Moreover, as heat treatment conditions (firing conditions) when forming the p-type diffusion layer and the electrode using the p-type diffusion layer forming composition of the present invention, heat treatment conditions usually used in the technical field can be applied.
In general, the heat treatment temperature (firing temperature) is 800 to 900 ° C., and an electrode having good characteristics can be formed.
The heat treatment time can be appropriately selected according to the heat treatment temperature and the like, and can be, for example, 1 second to 300 seconds.
In general, the heat treatment time for forming the electrode is preferably as short as possible from the viewpoint of electrode performance, while the heat treatment time for thermally diffusing the acceptor element is preferably as long as possible. Therefore, it is preferable to appropriately adjust the heat treatment time according to these balances and the composition of the p-type diffusion layer forming composition.

<Solar cell>
The solar battery cell of the present invention has a p-type diffusion layer and an electrode formed by heat-treating the p-type diffusion layer forming composition applied on the silicon substrate. Thereby, the solar cell which has a favorable characteristic and the generation | occurrence | production of curvature was suppressed is obtained, and it is excellent in productivity of this solar cell.

Next, the manufacturing method of the photovoltaic cell using the p-type diffused layer formation composition of this invention is demonstrated.
First, an alkaline solution is applied to crystalline silicon that is a p-type semiconductor substrate to remove the damaged layer, and a texture structure is obtained by etching.
Specifically, the damaged layer on the silicon surface generated when slicing from the ingot is removed with 20% by mass caustic soda. Next, etching is performed with a mixed solution of 1% by mass caustic soda and 10% by mass isopropyl alcohol to form a texture structure. In the solar battery cell, by forming a texture structure on the light receiving surface (front surface) side, a light confinement effect is promoted and high efficiency is achieved.

Next, tens of minutes of treatment is performed at 800 to 900 ° C. in a mixed gas atmosphere of phosphorus oxychloride (POCl ₃ ), nitrogen, and oxygen to uniformly form an n-type diffusion layer. 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 surface but also on the side surface and the back surface. Therefore, side etching is performed to remove the n-type diffusion layer on the side surface.

  Then, the p-type diffusion layer forming composition is applied onto the n-type diffusion layer on the back surface of the p-type semiconductor substrate, that is, the surface that is not the light receiving surface. In the present invention, the coating method is not limited, and examples thereof include a printing method, a spin method, a brush coating, a spray method, a doctor blade method, a roll coater method, and an ink jet method.

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

The semiconductor substrate coated with the p-type diffusion layer forming composition is heat-treated at 600 to 1200 ° C. (preferably 800 to 900 ° C.). By this heat treatment, an acceptor element is diffused into the semiconductor substrate, together with the p ⁺ -type diffusion layer is formed, the p ⁺ -type diffusion metal particles are sintered onto the layer electrode is formed (ohmic contact). A known continuous furnace, batch furnace, or the like can be applied to the heat treatment. Moreover, the furnace atmosphere at the time of heat processing can also be suitably adjusted to air, oxygen, nitrogen, etc.
The heat treatment time can be appropriately selected according to the content of the acceptor element contained in the p-type diffusion layer forming composition. For example, it can be 1 second to 300 seconds.

Further, in the conventional manufacturing method, an aluminum paste is printed on the back surface, and this is baked to make the n-type diffusion layer a p ⁺ -type diffusion layer, and at the same time, an ohmic contact is obtained. However, aluminum paste has a low electrical conductivity, and in order to reduce the sheet resistance, the aluminum layer usually formed on the entire back surface must have a thickness of 30 μm or more after firing. Further, when such a thick aluminum layer is formed, the thermal expansion coefficient differs greatly between silicon and aluminum, so that a large internal stress is generated in the silicon substrate during the firing and cooling process, causing warpage.
This internal stress has a problem that the crystal grain boundary is damaged and the power loss increases. In addition, the warp easily causes the cell to be damaged in the transportation of the solar battery cell in the module process and the connection with the copper wire called a tab wire. In recent years, due to the improvement of slicing technology, the thickness of the crystalline silicon substrate is being reduced, and the cells tend to be easily broken.

However, according to the manufacturing method of the present invention, the p-type diffusion layer forming composition of the present invention converts the n-type diffusion layer into a p ⁺ -type diffusion layer, and an electrode is formed on the p ⁺ -type diffusion layer. . Therefore, the material used for electrode formation on the back surface (metal particles contained in the p-type diffusion layer forming composition) is not limited to aluminum, and for example, silver particles or copper-containing particles can be applied. By using metal particles having high conductivity, the thickness of the back electrode can be made thinner than that of the conventional one, and internal stress and warpage in the silicon substrate generated during firing and cooling can be reduced.

An antireflection film is formed on the formed n-type diffusion layer. 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 orbits that do not contribute to the bonding of silicon atoms, that is, dangling bonds and hydrogen are combined to inactivate defects (hydrogen passivation).
More specifically, the mixed gas flow ratio NH ₃ / SiH ₄ is 0.05 to 1.0, the pressure in the reaction chamber is 0.1 to 2 Torr, the temperature during film formation is 300 to 550 ° C., and plasma discharge Is formed under the condition of a frequency of 100 kHz or more.

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

The said metal paste layer for surface electrodes is baked, and a photovoltaic cell is completed. When baked for several seconds to several minutes in the range of 600 to 900 ° C., the antireflection film, which is an insulating film, is melted by the glass particles contained in the electrode metal paste on the surface side, and the silicon surface is also partially melted in the paste. The metal particles (for example, silver particles) form a contact portion with the silicon substrate 10 and solidify. Thereby, the formed surface electrode and the silicon substrate are electrically connected. This is called fire-through.
The formation of the front surface electrode may be performed simultaneously with the formation of the back surface electrode and the p ⁺ -type diffusion layer.

The shape of the surface electrode will be described. The surface electrode includes a bus bar electrode and a finger electrode that intersects the bus bar electrode.
Such a 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. A surface electrode composed of a bus bar electrode and a finger electrode is generally used as an electrode on the light receiving surface side and is well known, and known forming means for the bus bar electrode and the finger electrode on the light receiving surface side can be applied.

In the above-described method for manufacturing a p-type diffusion layer and solar battery cell, a mixed gas of phosphorus oxychloride (POCl ₃ ), nitrogen and oxygen is used to form an n-type diffusion layer in crystalline silicon that is a p-type semiconductor substrate. Although used, 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.
In the method using the n-type diffusion layer forming composition for forming the n-type diffusion layer, first, the n-type diffusion layer forming composition is applied to the light-receiving surface which is the surface of the p-type semiconductor substrate, and the p-type of the present invention is applied to the back surface. The diffusion layer forming composition is applied and subjected to thermal diffusion treatment at 600 to 1200 ° C. By this thermal diffusion treatment, the donor element diffuses into the p-type semiconductor substrate on the surface to form an n-type diffusion layer, and the acceptor element diffuses on the back surface to form a p ⁺ -type diffusion layer and a back electrode. Except for this step, solar cells are produced by the same steps as the above method.

  The p-type diffusion layer forming composition of the present invention is not limited to the use of solar cell electrodes. For example, electrode wiring and shield wiring of plasma displays, ceramic capacitors, antenna circuits, various sensor circuits, and semiconductor devices It can be suitably used for applications such as heat dissipation materials.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, “part” and “%” are based on mass.

<Example 1>
(A) Preparation of p-type diffusion layer forming composition 77% by mass of silver particles, B ₂ O ₃ —CeO ₂ -based glass (B ₂ O ₃ : 39.6%, CeO ₂ : 10%, BaO: 10.4) %, MoO ₃ : 10%, ZnO: 30%) 10% by mass of particles, 0.5% by mass of ethyl cellulose, and 12.5% by mass of terpineol were mixed in an agate mortar for 20 minutes to form a paste, and a p-type diffusion layer Forming composition A was prepared. The particle diameter (D50%) of the silver particles was 1.8 μm, and the particle diameter (D50%) of the glass particles was 3.0 μm.

(B) Production of Solar Cell A p-type semiconductor substrate having a film thickness of 190 μm having an n-type semiconductor layer having a sheet resistance of 100 Ω / cm ² on the light-receiving surface, a texture, and an antireflection film (silicon nitride film) is prepared. It cut out to a size of 125 mm × 125 mm. An electrode having a 150 μm wide finger line and a 1.1 mm wide bus bar using a screen printing method on the light receiving surface and an electrode paste (manufactured by DuPont), and having a thickness of 20 μm after firing. It printed so that it might become a pattern. Printing conditions (screen plate mesh, printing speed, printing pressure) were adjusted as appropriate. This was placed in an oven heated to 150 ° C. for 15 minutes, and the solvent was removed by evaporation.

Subsequently, the p-type diffusion layer forming composition obtained above was similarly printed on the entire back surface by screen printing. The printing conditions were appropriately adjusted so that the film thickness after firing was 20 μm. This was placed in an oven heated to 150 ° C. for 15 minutes, and the solvent was removed by evaporation.
Subsequently, a heat treatment (baking) is performed at 850 ° C. for 10 seconds in an air atmosphere in an infrared rapid heating furnace to form a sun on which a desired electrode is formed on the front surface and a p-type diffusion layer and an electrode are formed on the back surface. Battery cell 1 was produced.
The obtained solar cell 1 was not warped.

<Example 2>
In Example 1, the solar cell 2 in which the desired p-type diffusion layer and electrode were formed in the same manner as in Example 1 except that the heat treatment (firing) at the time of electrode formation was changed to 850 ° C. for 1 minute. Was made.
The obtained solar battery cell 2 was not warped.

<Example 3>
In Example 1, glass particles were changed to B ₂ O ₃ —ZnO-based glass (B ₂ O ₃ : 40%, ZnO: 40%, CeO ₂ : 10%, MgO: 5%, CaO: 5%). In the same manner as in Example 1, a p-type diffusion layer forming composition B was prepared. The glass particles had a particle size (D50%) of 3.2 μm. Next, in the same manner as in Example 1, a solar battery cell 3 on which a desired p-type diffusion layer and electrode were formed was produced.
The obtained solar battery cell 3 was not warped.

<Example 4>
In Example 1, the glass particles were changed to B ₂ O ₃ —SiO ₂ glass (B ₂ O ₃ : 30%, SiO ₂ : 50%, CeO ₂ : 10%, ZnO: 10%). In the same manner as in Example 1, a p-type diffusion layer forming composition C was prepared. The glass particles had a particle size (D50%) of 2.9 μm. Next, in the same manner as in Example 1, a solar battery cell 4 on which a desired p-type diffusion layer and electrode were formed was produced.
The obtained solar battery cell 4 was not warped.

<Example 5>
In Example 1, except that the glass particles were B ₂ O ₃ —PbO-based glass (B ₂ O ₃ : 30%, PbO: 50%, ZnO: 20%), p-type was performed in the same manner as in Example 1. A diffusion layer forming composition D was prepared. The particle diameter (D50%) of the glass particles was 3.1 μm. Next, in the same manner as in Example 1, a solar battery cell 5 on which a desired p-type diffusion layer and electrode were formed was produced.
The obtained solar battery cell 5 was not warped.

<Example 6>
In Example 1, glass particles were changed to B ₂ O ₃ —SiO ₂ glass (B ₂ O ₃ : 40%, SiO ₂ : 10%, PbO: 30%, ZnO: 10%, CaO: 10%). In the same manner as in Example 1, a p-type diffusion layer forming composition E was prepared. The particle size (D50%) of the glass particles was 3.0 μm. Next, in the same manner as in Example 1, a solar battery cell 6 in which a desired p-type diffusion layer and electrode were formed was produced.
The obtained solar cell 6 was not warped.

<Example 7>
In Example 1, glass particles other than B ₂ O ₃ —SiO ₂ glass (B ₂ O ₃ : 40%, SiO ₂ : 10%, PbO: 20%, ZnO: 20%, NaO: 10%) were used. Prepared a paste composition F for solar cell n-type diffusion layer forming function-imparting electrode in the same manner as in Example 1. The particle size (D50%) of the glass particles was 3.5 μm. Next, in the same manner as in Example 1, a solar battery cell 7 on which a desired electrode was formed was produced.
The obtained solar battery cell 7 was not warped.

<Example 8>
In Example 1, the glass particles were changed to B ₂ O ₃ —ZnO-based glass (B ₂ O ₃ : 30%, ZnO: 40%, CaO: 20%, Al ₂ O ₃ : 10%). In the same manner as in Example 1, a p-type diffusion layer forming composition G was prepared. The glass particles had a particle size (D50%) of 2.8 μm. Next, in the same manner as in Example 1, a solar battery cell 8 on which a desired p-type diffusion layer and electrode were formed was produced.
The obtained solar cell 8 was not warped.

<Example 9>
Example 1 is the same as Example 1 except that the glass particles are B ₂ O ₃ —SiO ₂ glass (B ₂ O ₃ : 50%, SiO ₂ : 10%, ZnO: 30%, CaO: 10). Similarly, a p-type diffusion layer forming composition H was prepared. The glass particles had a particle size (D50%) of 3.2 μm. Next, in the same manner as in Example 1, a solar battery cell 9 in which a desired p-type diffusion layer and electrode were formed was produced.
The obtained solar battery cell 9 was not warped.

<Example 10>
In Example 1, silver-coated copper particles (manufactured by Hitachi Chemical Co., Ltd., silver coating amount: 20% by mass, particle size: 5.8 μm) prepared according to the method described in JP-A No. 14-100191. P-type diffusion layer forming composition I was prepared in the same manner as in Example 1 except that. Next, in the same manner as in Example 1, a solar battery cell 10 in which a desired p-type diffusion layer and electrode were formed was produced.
The obtained solar battery cell 10 was not warped.

<Comparative Example 1>
In the preparation of the p-type diffusion layer forming composition in Example 1, B ₂ O ₃ —CeO ₂ based glass (B ₂ O ₃ : 39.6%, CeO ₂ : 10%, BaO: 10.4%, MoO ₃ : 10%, ZnO: 30%) A composition for forming an electrode in the same manner as in Example 1 except that PbO—SiO ₂ glass (PbO: 65%, SiO ₂ : 35%) particles were used without using the particles. C1 was prepared.
Next, a solar cell C1 was produced in the same manner as in Example 1 except that the electrode forming composition C1 was used.
Warpage did not occur in the obtained solar battery cell C1.

<Comparative Example 2>
In the preparation of the p-type diffusion layer forming composition in Example 1, B ₂ O ₃ —CeO ₂ based glass (B ₂ O ₃ : 39.6%, CeO ₂ : 10%, BaO: 10.4%, MoO ₃ : 10%, ZnO: 30%) Electrodes in the same manner as in Example 1 except that Na ₂ O—SiO ₂ glass (Na ₂ O: 35%, SiO ₂ : 65%) particles were used instead of particles. A forming composition C2 was prepared.
Next, a solar cell C2 was produced in the same manner as in Example 1 except that the electrode forming composition C2 was used.
Warpage did not occur in the obtained solar battery cell C2.

<Comparative Example 3>
A solar battery cell C3 was produced in the same manner as in Example 2 except that the electrode forming composition C1 in Comparative Example 1 was used instead of the p-type diffusion layer forming composition A in Example 2.
The obtained solar cell C3 was not warped.

<Comparative Example 4>
In Example 2, instead of p-type diffusion layer forming composition A, an aluminum electrode paste (manufactured by PVG Solutions) was used, except that the printing conditions were adjusted so that the film thickness after firing was 20 μm. In the same manner as in Example 2, a solar battery cell C4 was produced.
Warpage did not occur in the obtained solar battery cell C4.
<Comparative Example 5>
In Example 2, instead of p-type diffusion layer forming composition A, an aluminum electrode paste (manufactured by PVG Solutions) was used, except that the printing conditions were adjusted so that the film thickness after firing was 50 μm. In the same manner as in Example 2, a solar battery cell C4 was produced.
Warpage occurred in the obtained solar battery cell C5.

<Evaluation>
Evaluation of the produced solar cell is WXS-155S-10 manufactured by Wacom Denso Co., Ltd. as pseudo-sunlight, and I-V CURVE TRACER MP-160 (manufactured by EKO INSTRUMENT, Inc.) as a current-voltage (IV) evaluation measuring instrument. ) Was combined with the measuring device. Eff (conversion efficiency), FF (fill factor), Voc (open circuit voltage), and Jsc (short circuit current) indicating the power generation performance as a solar cell are JIS-C-8912, JIS-C-8913 and JIS-C-, respectively. It is obtained by performing measurement according to 8914. Each measured value obtained is shown in Table 1 in terms of a relative value with the measured value of Comparative Example 1 as 100.0.
Further, the produced solar battery cell was immersed in a mixed acid in which 50% hydrofluoric acid and nitric acid were mixed at 1: 1 (mass ratio) for 30 minutes to dissolve and remove the back electrode, and silicon in the portion where the back electrode was removed. The sheet resistance of the surface was evaluated.

From the above, by using the p-type diffusion layer forming composition of the present invention, the sheet resistance of the silicon surface in the portion where the p-type diffusion layer forming composition is formed can be lowered, and B (boron) which is an acceptor element Can be confirmed to be effectively diffused.
At the same time, the electrodes can be sintered satisfactorily, and it can be seen that a solar cell exhibiting excellent characteristics can be constructed.

Claims (7)

  A p-type diffusion layer forming composition comprising metal particles, glass particles containing an acceptor element, a resin, and a solvent.   The p-type diffusion layer forming composition according to claim 1, wherein the acceptor element is at least one selected from B (boron), Al (aluminum), and Ga (gallium). The glass particles include at least one acceptor element-containing material selected from B ₂ O ₃ , Al ₂ O ₃ and Ga ₂ O ₃ , SiO ₂ , K ₂ O, Na ₂ O, Li ₂ O, BaO, And at least one glass component material selected from SrO, CaO, MgO, BeO, ZnO, PbO, CdO, V ₂ O ₅ , Tl ₂ O ₃ , SnO, ZrO ₂ , and MoO _3. The p-type diffusion layer forming composition according to claim 1 or 2.   The p-type diffusion layer forming composition according to claim 3, wherein a content ratio of the acceptor element-containing substance in the glass particles is 1% by mass or more and 80% by mass or less.   The p-type diffusion layer forming composition according to claim 1, wherein the metal particles are at least one selected from silver particles and silver-coated copper particles. Applying a p-type diffusion layer forming composition according to any one of claims 1 to 5 on a semiconductor substrate;
A heat treatment step for forming a p-type diffusion layer and an electrode by heat treatment;
The manufacturing method of the photovoltaic cell which has this.   A solar cell comprising a p-type diffusion layer and an electrode formed by applying the p-type diffusion layer forming composition according to any one of claims 1 to 5 on a semiconductor substrate and heat-treating the composition. .