JP2017188537A - Solar battery element, method for manufacturing the same, and solar battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a solar battery element having a passivation layer and an oxide film layer, by which the oxide film layer can be formed by a simple and easy manner.SOLUTION: A method for manufacturing a solar battery element having a passivation layer and an oxide film layer comprises the steps of: putting, on a semiconductor substrate, a composition for passivation layer formation, which includes a compound expressed by M(OR)(where M represents at least one kind selected from a group consisting of Al, Nb, Ta, VO, Y and Hf, R's independently represent an alkyl group or an aryl group, and m represents an integer of 1-5); and performing a thermal treatment on the composition for passivation layer formation.SELECTED DRAWING: None

Description

  The present invention relates to a solar cell element, a manufacturing method thereof, and a solar cell.

The manufacturing process of the conventional silicon solar cell element is demonstrated.
First, a p-type silicon substrate having a textured structure is prepared so as to promote the light confinement effect and achieve high efficiency, and subsequently, 800 ° C. to 900 ° C. in a mixed gas atmosphere of phosphorus oxychloride (POCl ₃ ), nitrogen and oxygen. The n-type diffusion layer is formed by performing several tens of minutes at a temperature. In this case, the n-type diffusion layer is formed not only on the surface (light-receiving surface) of the p-type silicon substrate but also on the surface (back surface) and the side surface opposite to the light-receiving surface. Therefore, side etching is performed to remove the n-type diffusion layer formed on the side surface. Thereafter, the n-type diffusion layer formed on the back surface needs to be converted into a p ⁺ -type diffusion layer. For this reason, by applying an aluminum paste containing aluminum powder and a binder to the entire back surface and heat-treating (baking) it, the n-type diffusion layer is converted into a p ⁺ -type diffusion layer and an aluminum electrode is formed. Get ohmic contact.

  However, since an aluminum electrode formed from an aluminum paste has low electrical conductivity, the aluminum electrode formed on the entire back surface usually has a thickness of about 10 μm to 20 μm after heat treatment (firing). Furthermore, since the thermal expansion coefficient differs greatly between silicon and aluminum, a large internal stress is generated in the silicon substrate during the heat treatment (firing) and cooling in the silicon substrate on which the aluminum electrode is formed, and the grain boundary Cause damage, crystal defect growth, and warping.

In order to solve this problem, there is a method of reducing the coating amount of the aluminum paste and reducing the thickness of 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 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. .

In relation to the above, a point contact technique has been proposed in which an aluminum paste is applied to a part of the surface of a silicon substrate to partially form a p ⁺ -type diffusion layer and an aluminum electrode (for example, see Patent Document 1). ).
In the case of a solar cell having such a point contact structure on the back surface, it is necessary to suppress the recombination rate of minority carriers on the surface of the portion other than the aluminum electrode. For this purpose, a SiO ₂ film or the like has been proposed as a passivation layer for the back surface (see, for example, Patent Document 2). As a passivation effect by forming such a SiO ₂ film, there is an effect of terminating the dangling bonds of silicon atoms in the back surface layer portion of the silicon substrate and reducing the surface state density causing recombination.

As another method of suppressing recombination of minority carriers, there is a method of reducing the minority carrier density by an electric field that generates fixed charges in the passivation layer. Such a passivation effect is generally called a field effect, and an aluminum oxide (Al ₂ O ₃ ) film or the like has been proposed as a material having a negative fixed charge (see, for example, Patent Document 3).
Such a passivation layer is generally formed by a method such as an ALD (Atomic Layer Deposition) method or a CVD (Chemical Vapor Deposition) method (for example, see Non-Patent Document 1). As a simple method for forming an aluminum oxide film on a semiconductor substrate, a sol-gel method has been proposed (see, for example, Non-Patent Documents 2 and 3). Furthermore, a passivation layer having a two-layer structure of aluminum oxide and silicon oxide has been proposed (for example, Non-Patent Document 4).

Japanese Patent No. 3107287 Japanese Patent Laid-Open No. 2004-6565 Japanese Patent No. 4767110

Journal of Applied Physics, 104 (2008), 113703-1 to 113703-7 Thin Solid Films, 517 (2009), 6327-6330 Chinese Physics Letters, 26 (2009), 088102-1 to 088102-4 Electrochemical and Solid-State Letters, 12 (2009), H388-H391.

  Since the method described in Non-Patent Document 1 includes complicated manufacturing processes such as vapor deposition, it may be difficult to improve productivity. In order to solve these problems, the inventors have developed a composition for forming a passivation layer that can be applied to simple techniques such as screen printing and spin coating. Further, as shown in Non-Patent Document 4, there is a report that the characteristics of a solar cell are improved by forming an oxide film on the surface of a silicon substrate when aluminum oxide is laminated by the ALD method of a competitive technique. However, the formation of the oxide film requires heat treatment, chemical treatment, and the like, and thus damages to the semiconductor substrate accompanying heat treatment, chemical treatment, and the like, and complication of the process become problems.

  The present invention has been made in view of the above-described conventional problems, and is obtained by a passivation layer capable of forming an oxide film layer by a simple method, a method for manufacturing a solar cell element having the oxide film layer, and this manufacturing method. It aims at providing a solar cell element and a solar cell containing this solar cell element.

  Specific means for achieving the above object are as follows.

<1> a step of providing a passivation layer forming composition containing a compound represented by the following general formula (I) on a semiconductor substrate;
Heat-treating the composition for forming a passivation layer,
The manufacturing method of the solar cell element which has a passivation layer and an oxide film layer.

M (OR ¹ ) _m (I)

[In General Formula (I), M represents at least one selected from the group consisting of Al, Nb, Ta, VO, Y, and Hf. R ¹ independently represents an alkyl group or an aryl group. m represents an integer of 1 to 5. ]

<2> The method for producing a solar cell element according to <1>, wherein the composition for forming a passivation layer contains water.

<3> The method for producing a solar cell element according to <1> or <2>, wherein the composition for forming a passivation layer contains a hydrolyzate of the compound represented by the general formula (I).

<4> Any one of <1> to <3>, wherein the composition for forming a passivation layer further includes a compound having an oxygen atom other than the compound represented by the general formula (I) in the molecular structure. The manufacturing method of the solar cell element of description.

<5> The method for producing a solar cell element according to <4>, wherein the compound having an oxygen atom in the molecular structure includes a compound represented by the following general formula (II).

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

<6> A solar cell element obtained by the method for manufacturing a solar cell element according to any one of <1> to <5>.

<7> A solar cell including the solar cell element according to <6>.

  According to the present invention, a passivation layer capable of forming an oxide film layer by a simple method, a method for manufacturing a solar cell element having the oxide film layer, a solar cell element obtained by this manufacturing method, and a solar cell including this solar cell element A battery is provided.

It is sectional drawing which shows typically an example of the manufacturing method of the solar cell element of this embodiment. It is sectional drawing which shows typically another example of the manufacturing method of the solar cell element of this embodiment. It is sectional drawing which shows typically another example of the manufacturing method of the solar cell element of this embodiment. It is a schematic plan view which shows an example of the light-receiving surface of the solar cell element of this embodiment. It is a schematic plan view which shows an example of the formation pattern of the passivation layer in a back surface. It is a schematic plan view which shows another example of the formation pattern of the passivation layer in a back surface. It is the schematic plan view to which the A section of FIG. 5 was expanded. It is the schematic plan view to which the B section of FIG. 5 was expanded. It is the schematic plan view to which the A section of FIG. 5 was expanded. It is the schematic plan view to which the B section of FIG. 5 was expanded. It is a schematic plan view which shows an example of the back surface of the solar cell element of this embodiment. It is a figure for demonstrating an example of the manufacturing method of the solar cell of this embodiment. It is a figure which shows the result of having observed the cross section of the silicon substrate obtained in Example 1 with the transmission electron microscope.

Hereinafter, the manufacturing method of the solar cell element which has the passivation layer and oxide film layer of this invention, the solar cell element obtained by this manufacturing method, and embodiment of the solar cell containing this solar cell element are described.
In this specification, the term “process” includes a process that is independent of other processes and includes the process if the purpose of the process is achieved even if it cannot be clearly distinguished from the other processes. It is.
In the present specification, the numerical ranges indicated by using “to” include numerical values described before and after “to” as the minimum value and the maximum value, respectively.
In the numerical ranges described stepwise in this specification, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of another numerical range. Good. Further, in the numerical ranges described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced with the values shown in the examples.
In the present specification, the content of each component in the composition is the sum of the plurality of substances present in the composition unless there is a specific indication when there are a plurality of substances corresponding to each component in the composition. It means the content rate of.
In the present specification, the particle diameter of each component in the composition is a mixture of the plurality of types of particles present in the composition unless there is a specific indication when there are a plurality of types of particles corresponding to each component in the composition. Means the value of.
In this specification, the term “layer” or “film” refers to a part of the region in addition to the case where the layer or the film is formed when the region where the layer or film exists is observed. It is also included when it is formed only.
In this specification, the term “lamination” indicates that layers are stacked, and two or more layers may be combined, or two or more layers may be detachable.

<Method for producing solar cell element>
A method for producing a solar cell element having a passivation layer and an oxide film layer according to the present embodiment (hereinafter sometimes referred to as “production method of the present embodiment”) is a compound represented by the following general formula (I) (hereinafter, A step of applying a composition for forming a passivation layer containing a “compound of formula (I)” onto a semiconductor substrate (hereinafter also referred to as “applying step”), and the composition for forming a passivation layer. And a step of heat-treating (sintering) the product (hereinafter sometimes referred to as “heat-treatment step”). The manufacturing method of this embodiment may further include other steps as necessary.

M (OR ¹ ) _m (I)

In general formula (I), M represents at least one selected from the group consisting of Al, Nb, Ta, VO, Y, and Hf. R ¹ independently represents an alkyl group or an aryl group. m represents an integer of 1 to 5.

  The manufacturing method of this embodiment can form a passivation layer and an oxide film layer by heat-treating (baking) after providing the composition for forming a passivation layer containing a compound of formula (I) on a semiconductor substrate. Therefore, in the manufacturing method of this embodiment, it is not always necessary to provide a step of forming an oxide film layer before the applying step. That is, the manufacturing method of this embodiment includes at least steps corresponding to steps (1) and (2) performed in the order described in A or B, which is a general method for manufacturing a solar cell element.

A:
(0) Step of forming an oxide film layer
(1) Step of forming a composition layer for forming a passivation layer
(2) Process B for forming a passivation layer by heat-treating (firing) the semiconductor substrate:
(1) Step of forming a composition layer for forming a passivation layer (2) Step of forming an oxide film layer and a passivation layer by heat-treating (firing) the semiconductor substrate

In the manufacturing method of this embodiment, since the step (0) can be omitted, the number of steps can be reduced, and the manufacturing method of the solar cell element can be simplified. Further, in the case where the manufacturing method of the present embodiment includes the step (0), when the step (0) requires heat treatment, the time during which the semiconductor substrate is heated can be shortened, and the thermal load applied to the semiconductor substrate is reduced. be able to. Therefore, it is possible to manufacture a solar cell element having a passivation layer that is more excellent in the passivation effect. Furthermore, when any one or more of a p ⁺ type diffusion layer and an n ⁺ type diffusion layer is formed on the semiconductor substrate, preventing the diffusion layer from diffusing more than necessary by heat treatment (firing). Can do.
In this embodiment, an oxide film layer refers to a layer containing an oxide of a metal element that constitutes a semiconductor substrate. When the semiconductor substrate is a silicon substrate, for example, the oxide film layer means a layer containing an oxide of Si that is a metal element constituting the silicon substrate.

  In this specification, the passivation effect of a semiconductor substrate is obtained by measuring the effective lifetime of minority carriers in a semiconductor substrate on which a passivation layer is formed, using a reflection microscopic device using a device such as WT-2000PVN manufactured by Nippon Semilab Co., Ltd. It can be evaluated by measuring by the wave conduction decay method.

Here, the effective lifetime τ is expressed by the following equation (A) by the bulk lifetime τb inside the semiconductor substrate and the surface lifetime τs on the surface of the semiconductor substrate. When the surface state density on the surface of the semiconductor substrate is small, τs increases, and as a result, the effective lifetime τ increases. Further, even if defects such as dangling bonds inside the semiconductor substrate are reduced, the bulk lifetime τb is increased and the effective lifetime τ is increased. That is, by measuring the effective lifetime τ, the interface characteristics between the passivation layer and the semiconductor substrate and the internal characteristics of the semiconductor substrate such as dangling bonds can be evaluated.
1 / τ = 1 / τb + 1 / τs (A)
Note that the longer the effective lifetime, the slower the recombination rate of minority carriers. Moreover, conversion efficiency improves by comprising a solar cell element using the semiconductor substrate with a long effective lifetime.

The semiconductor substrate is not particularly limited, and can be appropriately selected from those usually used for solar cell elements according to the purpose. As a semiconductor substrate, a silicon substrate, a germanium substrate, or the like is doped (diffused) with a p-type impurity or an n-type impurity. Of these, a silicon substrate is preferable. The semiconductor substrate may be a p-type semiconductor substrate or an n-type semiconductor substrate. Among these, from the viewpoint of the passivation effect, it is preferable that the surface on which the passivation layer is formed is a semiconductor substrate having a p-type layer. Even if the p-type layer on the semiconductor substrate is a p-type layer derived from the p-type semiconductor substrate, the p-type layer is formed on the n-type semiconductor substrate or the p-type semiconductor substrate as a p-type diffusion layer or a p ⁺ -type diffusion layer. It may be a thing.

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

<Oxide film layer formation process>
The manufacturing method of the present embodiment may include a step of forming an oxide film layer on at least one surface of the semiconductor substrate (hereinafter sometimes referred to as an oxide film layer forming step) as necessary. The surface on which the oxide film layer is formed is preferably the surface on the side to which the composition for forming a passivation layer is applied.

  The method for forming the oxide film layer can be appropriately selected from commonly used techniques depending on the purpose. Specifically, for example, thermal oxidation such as dry oxidation and wet oxidation, oxidation with a chemical solution such as nitric acid, oxidation by laser, plasma, etc., deposition of an oxide film by sputtering, CVD, ALD, etc., semiconductor substrate in an oxygen-existing environment And natural oxidation by placing.

  In the manufacturing method of the present embodiment, the oxide film layer is formed on the semiconductor substrate through the application process and the heat treatment process, and therefore the oxide film layer formation process can be omitted. This is because the moisture, oxygen, organic groups in metal alkoxide compounds, hydroxyl groups derived from metal alkoxide compounds, oxygen atoms in organic compounds such as solvents, etc. contained in the composition for forming a passivation layer form an oxide film layer. This is considered to be because an oxide film layer was formed on the surface of the substrate by the heat addition in the heat treatment process.

The thickness of the oxide film layer to be formed is preferably 0.5 nm or more. Further, it is more preferably 1 nm or more from the viewpoint of uniformity of the oxide film layer. Moreover, it is preferable that it is 10.0 nm or less from a viewpoint of the electric field effect in a passivation layer, and it is more preferable that it is 4.0 nm or less.
In another embodiment, the thickness of the oxide film layer to be formed is preferably 0.5 nm to 10.0 nm, more preferably 0.5 nm to 8.0 nm, and 0.5 nm to 6.0 nm. More preferably, it is particularly preferably 0.5 nm to 5.0 nm.
The method for measuring the thickness of the oxide film layer will be described in the following examples.

The oxide film layer only needs to have insulating properties, and is preferably a layer containing amorphous (amorphous). The oxide film layer may be a film containing a single substance or a composite film containing a plurality of substances.
Whether or not the oxide film layer contains amorphous can be confirmed by the following method. In addition, since the definition of amorphous is that it does not have a crystal structure, a method for confirming amorphous is performed by confirming no crystal structure in the oxide film layer.
When the oxide film layer contains amorphous, no peak derived from the crystal structure is observed in the oxide film layer by X-ray diffraction (XRD) or the like, or a very broad peak is observed. Become. Therefore, whether or not the oxide film layer contains amorphous can be determined by the presence or absence of a peak derived from the crystal structure by X-ray diffraction.
In addition, when crystalline and amorphous coexist in the location to be observed, after heating and cooling the semiconductor substrate to make the location to be observed crystalline, the peak intensity of X-ray diffraction before and after heating is measured. The presence of amorphous material may be determined from the change.
By providing a structure having an oxide film layer having a predetermined thickness on the surface of the semiconductor substrate, the passivation effect is improved. Although the mechanism is not clear, it is considered as follows. Although the passivation effect may be impaired by the generation of stress due to the deviation of the lattice constant between the crystal structure of the semiconductor substrate surface and the crystal structure of the passivation layer, an amorphous oxide film layer exists between the two. It is thought that stress is relieved. Further, if the thickness of the oxide film layer is equal to or less than a predetermined value, the distance between the fixed charge in the passivation layer and the recombination site of minority carriers does not become too long, so that the passivation effect is considered to be improved.

<Granting process>
The manufacturing method of this embodiment has the process (application | coating process) of providing the composition for passivation layer formation containing a compound of Formula (I) on a semiconductor substrate. By the applying step, the passivation layer forming composition layer can be formed on the semiconductor substrate.

  The shape of the composition layer for forming a passivation layer is not particularly limited and can be appropriately selected depending on the purpose. The composition layer for forming a passivation layer may be formed on the entire surface of the semiconductor substrate, or may be formed only on a part of the region. Moreover, the composition layer for forming a passivation layer may be formed only on one side of the semiconductor substrate or on both sides. Further, the passivation layer forming composition layer may be formed on a surface other than the surface on which the electrode forming composition layer is formed (that is, the surface on which the electrode forming composition layer is not formed). In particular, a passivation layer is formed in at least a part of a region where the electrode forming composition layer on the semiconductor substrate is not formed, that is, in at least a part of the region other than the region where the semiconductor substrate and the electrode forming composition layer are in contact with each other. It is preferable that a composition layer is formed. Thereby, it is suppressed that the contact resistance of an electrode raises. Further, the passivation layer can be formed by a simpler method. Details of the composition for forming a passivation layer will be described later.

  There is no restriction | limiting in particular in the method of providing the composition for formation of a passivation layer on a semiconductor substrate, According to the objective, it can select suitably. For example, the method of providing the composition for passivation layer formation on a semiconductor substrate can be mentioned using a well-known coating method. Specific examples include an immersion method, a screen printing method, an ink jet method, a dispenser method, a spin coating method, a brush coating method, a spray method, a doctor blade method, and a roll coating method. Among these, the screen printing method and the ink jet method are preferable from the viewpoints of pattern formability and productivity.

The thickness of the composition layer for forming a passivation layer formed on the semiconductor substrate is not particularly limited and can be appropriately selected depending on the purpose. For example, the thickness is preferably 5 nm to 50 μm, more preferably 10 nm to 30 μm, and still more preferably 15 nm to 20 μm.
In addition, the thickness of the formed composition layer for forming a passivation layer was measured by measuring the thickness at three points by an ordinary method using an interference type film thickness meter (for example, Filmetrics F20 film thickness measurement system). Calculated as an arithmetic average value.

<Heat treatment process>
The manufacturing method of this embodiment has the process (heat treatment process) of heat-processing (baking) the composition for formation of a passivation layer. In the heat treatment step, the semiconductor substrate having the passivation layer forming composition layer is heat treated (fired) to form a passivation layer that is a heat treated product (baked product) of the passivation layer forming composition layer, or passivation. A passivation layer and an oxide film layer, which are heat-treated products (baked products) of the layer-forming composition layer, are formed.

  The heat treatment step may be a single step or a plurality of steps.

  The heat treatment (firing) temperature is preferably 625 ° C. to 875 ° C., more preferably 650 ° C. to 850 ° C., and further preferably 670 ° C. to 820 ° C. from the viewpoint of passivation properties.

<Drying process>
The manufacturing method of this embodiment may have the process of drying the composition layer for passivation layer formation formed on the semiconductor substrate as needed. A passivation layer having a more uniform passivation effect can be formed by drying the composition layer for forming a passivation layer.

  The step of drying the passivation layer forming composition layer is not particularly limited as long as at least a part of the solvent that may be contained in the passivation layer forming composition can be removed. For example, the drying treatment can be performed at 30 ° C. to 500 ° C. for 1 minute to 60 minutes, and the drying treatment is preferably performed at 40 ° C. to 300 ° C. for 3 minutes to 40 minutes. The drying treatment may be performed under normal pressure or under reduced pressure.

  When the composition for forming a passivation layer contains a resin, the production method of this embodiment may further include a step of degreasing the composition layer for forming a passivation layer after the applying step and before the heat treatment step. . By having the process of degreasing the composition layer for forming a passivation layer, a more uniform passivation layer can be formed.

  The step of degreasing the passivation layer forming composition layer is not particularly limited as long as at least a part of the resin that may be contained in the passivation layer forming composition can be removed. The degreasing treatment can be performed, for example, at 250 ° C. to 450 ° C. for 3 minutes to 120 minutes, preferably at 300 ° C. to 400 ° C. for 10 minutes to 60 minutes. The degreasing treatment is preferably performed in the presence of oxygen, and more preferably performed in the air.

<Alkaline aqueous solution treatment process>
It is preferable that the manufacturing method of this embodiment further has the process (alkaline aqueous-solution process process) which contacts the aqueous alkali solution on a semiconductor substrate, and wash | cleans the surface of a semiconductor substrate before a provision process. By washing the surface of the semiconductor substrate with an alkaline aqueous solution, organic substances, particles and the like existing on the surface of the semiconductor substrate can be removed, and the passivation effect is improved.

  As a method for cleaning with an alkaline aqueous solution, generally known RCA cleaning and the like can be exemplified. For example, an organic substance, particles, and the like can be removed by immersing the semiconductor substrate in a mixed solution of ammonia water and hydrogen peroxide water and processing at 60 ° C. to 80 ° C. The cleaning time is preferably 10 seconds to 10 minutes, and more preferably 30 seconds to 5 minutes.

  The solar cell element having the passivation layer and the oxide film layer manufactured by the manufacturing method of the present embodiment can also be applied to a light emitting diode element or the like.

<Composition for forming a passivation layer>
The composition for forming a passivation layer contains a compound of formula (I).
The composition for forming a passivation layer may contain a compound of formula (I) and water. Hereinafter, the composition for forming a passivation layer containing the compound of formula (I) and water may be referred to as a first composition for forming a passivation layer.
Further, the composition for forming a passivation layer may contain a hydrolyzate of the compound of formula (I). Hereinafter, the composition for forming a passivation layer containing a hydrolyzate of the compound of formula (I) may be referred to as a second composition for forming a passivation layer.
The composition for forming a passivation layer may further contain other components as necessary. When the composition for forming a passivation layer contains the above-described components, it is possible to form a composition layer for forming a passivation layer that is excellent in pattern formability. Furthermore, by using the composition for forming a passivation layer, it is possible to form a passivation layer having a superior pattern forming property and an excellent passivation effect by a simple method.

M (OR ¹ ) _m (I)

In general formula (I), M represents at least one selected from the group consisting of Al, Nb, Ta, VO, Y, and Hf. R ¹ independently represents an alkyl group or an aryl group. m represents an integer of 1 to 5.

(Compound represented by formula (I) and hydrolyzate thereof)
The first composition for forming a passivation layer contains at least one compound of formula (I). In addition, the second composition for forming a passivation layer contains at least one hydrolyzate of the compound of formula (I). When the composition for forming a passivation layer contains at least one compound of formula (I) or a hydrolyzate thereof, a passivation layer having an excellent passivation effect can be formed. The reason can be considered as follows.

  A metal oxide formed by heat-treating (firing) a composition for forming a passivation layer containing a compound of formula (I) or a hydrolyzate thereof has defects of metal atoms or oxygen atoms, and generates a fixed charge. It will be easier. When this fixed charge generates charge near the interface of the semiconductor substrate, the concentration of minority carriers can be reduced. As a result, the carrier recombination rate at the interface is suppressed, and an excellent passivation effect is achieved. Conceivable.

  Here, regarding the state of the passivation layer that generates a fixed charge on the semiconductor substrate, the cross section of the semiconductor substrate is subjected to electron transmission loss electron spectroscopy (EELS, Electron Energy Loss Spectroscopy) using a scanning transmission electron microscope (STEM). It can be evaluated by examining the binding mode in the analysis of). Further, the crystal phase near the interface of the passivation layer can be confirmed by measuring the X-ray diffraction spectrum. Furthermore, the fixed charge of the passivation layer can be evaluated by a CV method (Capacitance Voltage measurement).

  In the general formula (I), M is at least one selected from the group consisting of Al, Nb, Ta, VO, Y, and Hf. The passivation effect, the pattern forming property of the composition for forming a passivation layer, and the passivation From the viewpoint of workability in preparing the layer forming composition, M is preferably at least one selected from the group consisting of Al, Nb, Ta and Y.

In general formula (I), each R ¹ independently represents an alkyl group or an aryl group, preferably an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 14 carbon atoms, and an alkyl group having 1 to 8 carbon atoms. Are more preferable, and an alkyl group having 1 to 4 carbon atoms is more preferable. The alkyl group represented by R ¹ may be linear or branched.
Specific examples of the alkyl group represented by R ¹ include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, t-butyl, hexyl, and octyl. Group, ethylhexyl group and the like.
Specific examples of the aryl group represented by R ¹ include a phenyl group.
The alkyl group represented by R ¹ may have a substituent, and examples of the substituent include an amino group, a hydroxy group, a carboxy group, a sulfo group, and a nitro group.
The aryl group represented by R ¹ may have a substituent, and examples of the substituent include a methyl group, an ethyl group, an isopropyl group, an amino group, a hydroxy group, a carboxy group, a sulfo group, and a nitro group. Can be mentioned.
Among these, R ¹ is preferably an unsubstituted alkyl group having 1 to 8 carbon atoms, and more preferably an unsubstituted alkyl group having 1 to 4 carbon atoms, from the viewpoint of reactivity with water and a passivation effect. preferable.

  In general formula (I), m represents an integer of 1 to 5. Here, from the viewpoint of reactivity with water, m is preferably 3 when M is Al, m is preferably 5 when M is Nb, and M is Ta. In some cases, m is preferably 5, m is preferably 3 when m is VO, m is preferably 3 when M is Y, and M is Hf. In this case, m is preferably 4.

As the compound of formula (I), M is at least one selected from the group consisting of Al, Nb, Ta and Y, R ¹ is an unsubstituted alkyl group having 1 to 4 carbon atoms, and m is It is preferably an integer of 1 to 5, more preferably M is Nb, R ¹ is an unsubstituted alkyl group having 1 to 4 carbon atoms, and m is 5.

  The state of the compound of formula (I) may be solid or liquid at room temperature (25 ° C.). From the viewpoint of the storage stability of the composition for forming a passivation layer and the miscibility in the case where a compound represented by the general formula (II) described later is used in combination, the compound represented by the general formula (I) is a liquid. It is preferable.

  The compound of formula (I) is specifically aluminum methoxide, aluminum ethoxide, aluminum isopropoxide, aluminum n-propoxide, aluminum n-butoxide, aluminum t-butoxide, aluminum isobutoxide, niobium methoxide, niobium. Ethoxide, niobium isopropoxide, niobium n-propoxide, niobium n-butoxide, niobium t-butoxide, niobium isobutoxide, tantalum methoxide, tantalum ethoxide, tantalum isopropoxide, tantalum n-propoxide, tantalum n- Butoxide, tantalum t-butoxide, tantalum isobutoxide, yttrium methoxide, yttrium ethoxide, yttrium isopropoxide, yttrium n-propoxide, yttrium n-butoxide Yttrium t-butoxide, yttrium isobutoxide, vanadium oxymethoxide, vanadium oxyethoxide, vanadium oxyisopropoxide, vanadium oxy n-propoxide, vanadium oxy n-butoxide, vanadium oxy t-butoxide, vanadium oxyisobutoxide , Hafnium methoxide, hafnium ethoxide, hafnium isopropoxide, hafnium n-propoxide, hafnium n-butoxide, hafnium t-butoxide, hafnium isobutoxide, etc., among which aluminum ethoxide, aluminum isopropoxide, Aluminum n-butoxide, niobium ethoxide, niobium n-propoxide, niobium n-butoxide, tantalum ethoxide, tantalum n-propyl Pokishido, tantalum n- butoxide, yttrium isopropoxide, and yttrium n- butoxide are preferred.

  In addition, the compound of formula (I) may be a prepared product or a commercially available product. Commercially available products include, for example, pentamethoxyniobium, pentaethoxyniobium, penta-i-propoxyniobium, penta-n-propoxyniobium, penta-i-butoxyniobium, penta-n-butoxyniobium from High Purity Chemical Laboratory Co. , Penta-sec-butoxy niobium, pentamethoxy tantalum, pentaethoxy tantalum, penta-i-propoxy tantalum, penta-n-propoxy tantalum, penta-i-butoxy tantalum, penta-n-butoxy tantalum, penta-sec-butoxy tantalum Penta-t-butoxytantalum, vanadium (V) trimethoxide oxide, vanadium (V) triethoxide oxide, vanadium (V) tri-i-propoxide oxide, vanadium (V) tri-n-propoxide oxide, vanadium( ) Tri-i-butoxide oxide, vanadium (V) tri-n-butoxide oxide, vanadium (V) tri-sec-butoxide oxide, vanadium (V) tri-t-butoxide oxide, tri-i-propoxy yttrium, tri- n-butoxy yttrium, tetramethoxy hafnium, tetraethoxy hafnium, tetra-i-propoxy hafnium, tetra-t-butoxy hafnium, pentaethoxyniobium, pentaethoxy tantalum, pentaboxy tantalum, yttrium-n-butoxide from Hokuko Chemical Co., Ltd. , Hafnium-tert-butoxide, vanadium oxytriethoxide, vanadium oxytrinormal propoxide, vanadium oxytrinormal butoxide, vanadium oxy from Nichia Corporation Triisobutoxide, mention may be made of vanadium oxy-tri secondary butoxide and the like.

  The compound of formula (I) is prepared by reacting a specific metal (M) halide with an alcohol in the presence of an inert organic solvent, and further adding ammonia or amines to extract the halogen (specialty). Known manufacturing methods such as Japanese Utility Model Laid-Open No. 63-227593 and Japanese Patent Laid-Open No. 3-291247) can be used.

  A part of the compound of formula (I) may be contained in the composition for forming a passivation layer as a compound having a chelate structure formed by mixing with a compound having a specific structure having two carbonyl groups described later.

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

  The content of the compound of formula (I) contained in the composition for forming a passivation layer can be appropriately selected as necessary. The content of the compound of formula (I) can be set to, for example, 0.1% by mass to 80% by mass in the composition for forming a passivation layer from the viewpoint of storage stability and a passivation effect, and 0.5% by mass. % To 70% by mass, more preferably 1% to 60% by mass, and still more preferably 1% to 50% by mass.

The content of the hydrolyzate of the compound of formula (I) contained in the second passivation layer forming composition can be appropriately selected as necessary. From the viewpoint of the passivation effect, the content of the hydrolyzate of the compound of formula (I) can be, for example, 0.1% by mass to 80% by mass in the second composition for forming a passivation layer. 0.5 mass% to 70 mass% is preferable, 1 mass% to 60 mass% is more preferable, and 1 mass% to 50 mass% is still more preferable.
In the present embodiment, the hydrolyzate of the compound of formula (I) refers to a hydrolysis product of the compound of formula (I) obtained by adding water to the compound of formula (I). In the hydrolyzate of the compound, the compound of formula (I) that has not reacted with water may remain, or water that has not reacted with the compound of formula (I) may remain.
In this embodiment, the hydrolyzate of the compound of formula (I) may contain a dehydration condensate of the hydrolyzate of the compound of formula (I).

(water)
The first composition for forming a passivation layer contains water. When the first composition for forming a passivation layer contains water, the composition for forming a passivation layer having excellent pattern forming properties is obtained. The reason can be considered as follows.

  Water reacts at least partially with the compound of formula (I) in the first composition for forming a passivation layer. The hydrolyzate of the compound of formula (I), which is a metal compound formed by reacting water with the compound of formula (I), is considered to form a network between metal compounds or between the metal compound and water. Further, it is considered that this network is easily broken when the composition for forming a passivation layer is flowing, and is re-formed when the composition becomes stationary again. This network increases the viscosity when the composition for forming a passivation layer is stationary, and decreases the viscosity when the composition is flowing. As a result, it is considered that the composition for forming a passivation layer develops thixotropy necessary for pattern formation.

  By using a composition for forming a passivation layer having excellent pattern forming properties, a composition layer for forming a passivation layer having a desired shape can be formed in a desired region. Accordingly, it is possible to manufacture a solar cell element in which a passivation layer is formed in a desired shape in a desired region.

  The water state may be solid or liquid. From the viewpoint of miscibility with the compound of formula (I), water is preferably a liquid.

The content of water contained in the first composition for forming a passivation layer can be appropriately selected as necessary.
From the viewpoint of imparting thixotropy to the first passivation layer forming composition, the water content is 1 of “OR ¹ group” contained in the compound of formula (I) in the first passivation layer forming composition. For example, it can be 0.1 mol or more, preferably 1 mol or more, more preferably 2 mol or more, and still more preferably 3 mol or more with respect to mol.
In addition, from the viewpoint of pattern formability and passivation effect, the water content is, for example, 1 mol of “OR ¹ group” contained in the compound of formula (I) in the first composition for forming a passivation layer, for example, It can be 0.1 mol-30 mol, It is preferable that it is 1 mol-25 mol, It is more preferable that it is 2 mol-20 mol, It is still more preferable that it is 3 mol-20 mol.

In addition, the second composition for forming a passivation layer may contain water. The content of water contained in the second passivation layer forming composition can be appropriately selected as necessary.
From the viewpoint of imparting thixotropy to the second passivation layer forming composition, the water content is “OR” contained in the compound (I) and the hydrolyzate thereof in the second passivation layer forming composition. For example, it can be 0.1 mol or more, preferably 1 mol or more, more preferably 2 mol or more, and still more preferably 3 mol or more with respect to 1 mol of ¹ group. .
From the viewpoint of pattern formability and passivation effect, the water content is, for example, about 0.1 mol relative to 1 mol of “OR ¹ group” contained in the compound of formula (I) in the second composition for forming a passivation layer. It can be 1-30 mol, It is preferable that it is 1-25 mol, It is more preferable that it is 2-20 mol, It is still more preferable that it is 3-20 mol.

The amount of water that has acted on the compound of formula (I) in the composition for forming a passivation layer can be calculated from the amount of alcohol liberated from the compound of formula (I). When water acts on the compound of formula (I), alcohol, that is, R ¹ OH is liberated from the compound of formula (I). The amount of this liberated alcohol is proportional to the number of functional groups of the compound of formula (I) on which water has acted. Therefore, by measuring the amount of this liberated alcohol, the amount of water acting on the compound of formula (I) can be calculated. The measurement of the amount of alcohol liberated can be confirmed, for example, using gas chromatography mass spectrometry (GC-MS).

0.5 mass%-70 mass% are preferable, and, as for the content rate of alcohol contained in the composition for forming a passivation layer, that is, liberated R ¹ OH, 1 mass% to 60 mass% are more preferable, and 1 mass% to 50 mass%. More preferred is mass%.

The composition for forming a passivation layer may further contain a compound having an oxygen atom other than the compound of formula (I) in the molecular structure (hereinafter sometimes referred to as “oxygen-containing compound”).
When the composition for forming a passivation layer contains an oxygen-containing compound, examples of the oxygen-containing compound include a compound represented by the following general formula (II), oxygen dissolved in the composition, water, ketone, ester, ether , Alcohol, amide compound and the like. Among these, the compound represented by the general formula (II) described later is preferable.
When the composition for forming a passivation layer contains an oxygen-containing compound, the content of the oxygen-containing compound is not particularly limited. Among them, the content of the oxygen-containing compound when the total content of the compound of formula (I) or a hydrolyzate thereof and the oxygen-containing compound is 100% by mass is 0.5% by mass to 80% by mass. It is preferably 1% by mass to 75% by mass, more preferably 2% by mass to 70% by mass, and particularly preferably 3% by mass to 70% by mass.
By setting the content of the oxygen-containing compound to 0.5% by mass or more, the passivation effect tends to be improved. Moreover, it exists in the tendency for the storage stability of the composition for passivation layer formation to improve by making an oxygen-containing compound into 80 mass% or less.

(Compound represented by formula (II))
The composition for forming a passivation layer may contain at least one compound represented by the following general formula (II) (hereinafter referred to as “organoaluminum compound”) as an oxygen-containing compound.

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

  When the composition for forming a passivation layer contains an organoaluminum compound, the passivation effect can be further improved. This can be considered as follows.

The organoaluminum compound includes compounds called aluminum alkoxide, aluminum chelate and the like, and preferably has an aluminum chelate structure in addition to the aluminum alkoxide structure. Also, Nippon Seramikkusu Kyokai Gakujutsu Ronbunshi, vol. 97, pp 369-399 (1989), the organoaluminum compound becomes aluminum oxide (Al ₂ O ₃ ) by heat treatment (firing). At this time, since the formed aluminum oxide is likely to be in an amorphous state, a four-coordinate aluminum oxide layer is easily formed in the vicinity of the interface with the semiconductor substrate, and may have a large negative fixed charge due to the four-coordinate aluminum oxide. It is considered possible. At this time, it is considered that a passivation layer having an excellent passivation effect can be formed as a result of compounding with the compound derived from the formula (I) having a fixed charge or an oxide derived from the hydrolyzate thereof.

  In addition to the above, by combining the compound of formula (I) or a hydrolyzate thereof and an organoaluminum compound as in the present embodiment, it is considered that the passivation effect is further enhanced by the respective effects in the passivation layer. Further, the compound (I) or the hydrolyzate thereof and the organoaluminum compound are heat-treated (fired), whereby the metal (M) and aluminum (Al) contained in the compound (I) are mixed. It is considered that the reactivity as a composite metal alkoxide and physical properties such as vapor pressure are improved, the denseness of the passivation layer as a heat-treated product (baked product) is improved, and as a result, the passivation effect is further enhanced.

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

In general formula (II), n represents an integer of 1 to 3. n is preferably 1 or 3 from the viewpoint of storage stability, and more preferably 1 from the viewpoint of solubility.
X ² and X ³ each independently represent an oxygen atom or a methylene group. From the viewpoint of storage stability, at least one of X ² and X ³ is preferably an oxygen atom.
R ³ , R ⁴ and R ⁵ in the general formula (II) each independently represent a hydrogen atom or an alkyl group. The alkyl group represented by R ³ , R ⁴ and R ⁵ may be linear or branched. The alkyl group represented by R ³ , R ⁴ and R ⁵ is preferably an alkyl group having 1 to 8 carbon atoms, and more preferably an alkyl group having 1 to 4 carbon atoms. Specific examples include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a t-butyl group, a hexyl group, an octyl group, and an ethylhexyl group.

Among these, from the viewpoint of storage stability and a passivation effect, R ³ and R ⁴ are each independently preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 8 carbon atoms, and preferably a hydrogen atom or 1 to 4 carbon atoms. The unsubstituted alkyl group is more preferable.
R ⁵ is preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 8 carbon atoms from the viewpoint of storage stability and a passivation effect, and is a hydrogen atom or an unsubstituted alkyl group having 1 to 4 carbon atoms. More preferably.

From the viewpoint of storage stability, the organoaluminum compound is preferably a compound in which n is an integer of 1 to 3, and R ⁵ is independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

From the viewpoint of storage stability and passivation effect, the organoaluminum compound is an integer from 1 to 3, R ² is each independently an alkyl group having 1 to 4 carbon atoms, and at least X ² and X ³ One is an oxygen atom, R ³ and R ⁴ are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ⁵ is a compound that is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. It is preferable. In the organoaluminum compound, n is an integer of 1 to 3, R ² is each independently an unsubstituted alkyl group having 1 to 4 carbon atoms, and at least one of X ² and X ³ is an oxygen atom, When R ³ or R ⁴ bonded to the oxygen atom is an alkyl group having 1 to ⁴ carbon atoms and X ² or X ³ is a methylene group, R ³ or R ⁴ bonded to the methylene group is a hydrogen atom. More preferably, R ⁵ is a hydrogen atom.

  Specific examples of the organoaluminum compound represented by the general formula (II) where n is an integer of 1 to 3 include aluminum ethyl acetoacetate diisopropylate and tris (ethyl acetoacetate) aluminum.

  Moreover, as the organoaluminum compound represented by the general formula (II) and n being an integer of 1 to 3, a prepared product or a commercially available product may be used. As a commercial item, the brand name of Kawaken Fine Chemical Co., Ltd., ALCH, ALCH-50F, ALCH-75, ALCH-TR, and ALCH-TR-20 can be mentioned, for example.

The organoaluminum compound represented by the general formula (II) and n is an integer of 1 to 3 is prepared by mixing an aluminum trialkoxide and a compound having a specific structure having two carbonyl groups described later. Can do. A commercially available aluminum chelate compound may also be used.
When an aluminum trialkoxide and a compound having a specific structure having two carbonyl groups are mixed, at least a part of the alkoxide group of the aluminum trialkoxide is substituted with the compound having the specific structure to form an aluminum chelate structure. At this time, if necessary, a liquid medium may be present, and heat treatment, addition of a catalyst, and the like may be performed. By replacing at least a part of the aluminum alkoxide structure with the aluminum chelate structure, the stability of the organoaluminum compound to hydrolysis and polymerization reaction is improved, and the storage stability of the composition for forming a passivation layer containing this is further improved. To do.

  The compound having a specific structure having two carbonyl groups is preferably at least one selected from the group consisting of a β-diketone compound, a β-ketoester compound, and a malonic acid diester from the viewpoint of reactivity and storage stability. . Specific examples of the compound having a specific structure having two carbonyl groups include acetylacetone, 3-methyl-2,4-pentanedione, 2,3-pentanedione, 3-ethyl-2,4-pentanedione, and 3-butyl. -2,4-pentanedione, 2,2,6,6-tetramethyl-3,5-heptanedione, 2,6-dimethyl-3,5-heptanedione, 6-methyl-2,4-heptanedione, etc. Β-diketone compound, methyl acetoacetate, ethyl acetoacetate, n-propyl acetoacetate, isopropyl acetoacetate, isobutyl acetoacetate, n-butyl acetoacetate, t-butyl acetoacetate, n-pentyl acetoacetate, isopentyl acetoacetate, N-hexyl acetoacetate, n-octyl acetoacetate, n-heptyl acetoacetate, 3-pentyl acetoacetate, 2-acetate Ethyl luheptanoate, ethyl 2-methylacetoacetate, ethyl 2-butylacetoacetate, ethyl hexylacetoacetate, ethyl 4,4-dimethyl-3-oxovalerate, ethyl 4-methyl-3-oxovalerate, ethyl 2-ethylacetoacetate Methyl 4-methyl-3-oxovalerate, ethyl 3-oxohexanoate, ethyl 3-oxovalerate, methyl 3-oxovalerate, methyl 3-oxohexanoate, ethyl 3-oxoheptanoate, 3-oxo Β-ketoester compounds such as methyl heptanoate, methyl 4,4-dimethyl-3-oxovalerate, dimethyl malonate, diethyl malonate, di-n-propyl malonate, diisopropyl malonate, di-n-butyl malonate, malon Di-t-butyl acid, dihexyl malonate, t-butylethyl malonate, methyl malonate Le, diethyl malonate, isopropyl malonate, n- butyl diethyl malonate, sec- butyl diethyl malonate, isobutyl diethyl malonate, and the like malonic acid diester, such as 1-methyl butyl diethylmalonate.

  The number of aluminum chelate structures can be controlled, for example, by appropriately adjusting the ratio of mixing aluminum trialkoxide and a compound having a specific structure having two carbonyl groups. Moreover, you may select suitably the compound which has a desired structure from a commercially available aluminum chelate compound.

  Among organoaluminum compounds, at least one selected from the group consisting of aluminum ethyl acetoacetate diisopropylate and triisopropoxyaluminum from the viewpoint of the passivation effect and compatibility with the solvent contained as necessary Is preferable, and aluminum ethyl acetoacetate diisopropylate is more preferable.

  The presence of the aluminum chelate structure in the organoaluminum compound can be confirmed by a commonly used analytical method. For example, it can confirm based on an infrared spectroscopy spectrum, a nuclear magnetic resonance spectrum, and melting | fusing point.

  The property of the organoaluminum compound may be liquid or solid, and is not particularly limited. From the viewpoint of the passivation effect and storage stability, the homogeneity of the formed passivation layer is further improved by using an organoaluminum compound having good stability at room temperature (25 ° C.) and solubility or dispersibility. A desired passivation effect can be stably obtained.

In the composition for forming a passivation layer, when an organoaluminum compound is included as the oxygen-containing compound, the organoaluminum compound has a total content of 100% by mass of the compound of formula (I) or a hydrolyzate thereof and the oxygen-containing compound. The content is preferably 0.5% by mass to 80% by mass, more preferably 1% by mass to 75% by mass, still more preferably 2% by mass to 70% by mass, and further preferably 3% by mass. It is especially preferable that it is -70 mass%.
By setting the content of the organoaluminum compound to 0.5% by mass or more, the passivation effect tends to be improved. Moreover, it exists in the tendency for the storage stability of the composition for passivation layer formation to improve by making an organoaluminum compound 80 mass% or less.

  When the composition for forming a passivation layer contains an organoaluminum compound, the content of the organoaluminum compound in the composition for forming a passivation layer can be appropriately selected as necessary. The content of the organoaluminum compound can be 0.1% by mass to 60% by mass in the composition for forming a passivation layer, and 0.5% by mass to 55% by mass from the viewpoint of storage stability and a passivation effect. It is preferable that it is 1 mass%-50 mass%, and it is still more preferable that it is 1 mass%-45 mass%.

(Liquid medium)
The composition for forming a passivation layer may contain a liquid medium (solvent or dispersion medium). When the composition for forming a passivation layer contains a liquid medium, the viscosity can be easily adjusted, the applicability can be further improved, and a more uniform passivation layer can be formed. It does not restrict | limit especially as a liquid medium, It can select suitably as needed. Among them, a liquid medium capable of dissolving a compound of formula (I) and an oxygen-containing compound such as an organoaluminum compound added as necessary to give a uniform solution is preferable, and more preferably contains at least one organic solvent. preferable. A liquid medium means a medium in a liquid state at room temperature (25 ° C.).

  Specific examples of the liquid medium include acetone, methyl ethyl ketone, methyl n-propyl ketone, methyl isopropyl ketone, methyl n-butyl ketone, methyl isobutyl ketone, methyl n-pentyl ketone, methyl n-hexyl ketone, diethyl ketone, Ketone solvents such as di-n-propyl ketone, diisobutyl ketone, trimethylnonanone, cyclohexanone, cyclopentanone, methylcyclohexanone, 2,4-pentanedione, acetonylacetone, diethyl ether, methyl ethyl ether, methyl-n-propyl Ether, diisopropyl ether, tetrahydrofuran, methyltetrahydrofuran, dioxane, dimethyldioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene Recall di-n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol methyl n-propyl ether, diethylene glycol methyl n-butyl ether, diethylene glycol di-n-propyl ether, Diethylene glycol di-n-butyl ether, diethylene glycol methyl-n-hexyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol methyl ethyl ether, triethylene glycol methyl n-butyl ether, triethylene glycol di-n-butyl ether , Triethylene Recall methyl-n-hexyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol methyl ethyl ether, tetraethylene glycol methyl-n-butyl ether, tetraethylene glycol di-n-butyl ether, tetraethylene glycol methyl-n -Hexyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol di-n-propyl ether, propylene glycol di-n-butyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, dipropylene glycol methyl ethyl ether, dipropylene Glycol methyl-n-butyl ether, dip Lopylene glycol di-n-propyl ether, dipropylene glycol di-n-butyl ether, dipropylene glycol methyl-n-hexyl ether, tripropylene glycol dimethyl ether, tripropylene glycol diethyl ether, tripropylene glycol methyl ethyl ether, tripropylene glycol methyl -N-butyl ether, tripropylene glycol di-n-butyl ether, tripropylene glycol methyl-n-hexyl ether, tetrapropylene glycol dimethyl ether, tetrapropylene glycol diethyl ether, tetrapropylene glycol methyl ethyl ether, tetrapropylene glycol methyl-n-butyl ether Tetrapropylene glycol methyl-n-hexyl A Ether solvent such as tetrapropylene glycol di-n-butyl ether, methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, sec-butyl acetate, n-pentyl acetate, sec-acetate Pentyl, 3-methoxybutyl acetate, methylpentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, 2- (2-butoxyethoxy) ethyl acetate, 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 methyl ether acetate, dipropylene glycol ethyl ether acetate, glycol diacetate, methoxytrie acetate Lenglycol, isoamyl acetate, ethyl propionate, n-butyl propionate, isoamyl propionate, diethyl oxalate, di-n-butyl oxalate, methyl lactate, 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 glycol ethyl ether acetate, propylene glycol propyl ether acetate, γ-butyrolactone, γ- Ester solvents such as valerolactone, acetonitrile, N-methylpyrrolidinone, N-ethylpyrrolidinone, Nn-propylpyrrolidi Aprotic polar solvents such as N, Nn-butylpyrrolidinone, Nn-hexylpyrrolidinone, N-cyclohexylpyrrolidinone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide, methylene chloride, chloroform, Hydrophobic organic solvents such as dichloroethane, benzene, toluene, xylene, hexane, octane, ethylbenzene, 2-ethylhexanoic acid, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, t-butanol N-pentanol, isopentanol, 2-methylbutanol, sec-pentanol, t-pentanol, 3-methoxybutanol, n-hexanol, 2-methylpentanol, sec-hexanol, 2 -Ethylbutanol, sec-heptanol, n-octanol, 2-ethylhexanol, sec-octanol, n-nonyl alcohol, n-decanol, sec-undecyl alcohol, trimethylnonyl alcohol, sec-tetradecyl alcohol, sec-heptadecyl Alcohol solvents such as alcohol, cyclohexanol, methylcyclohexanol, benzyl alcohol, ethylene glycol, 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 mono Examples thereof include glycol monoether solvents such as ethyl ether and tripropylene glycol monomethyl ether, and terpene solvents such as terpinene, terpineol, myrcene, alloocimene, limonene, dipentene, pinene, carvone, osymene, and ferrandrene. These liquid media are used alone or in combination of two or more.

  Among these, the liquid medium preferably contains at least one selected from the group consisting of a terpene solvent, an ester solvent, and an alcohol solvent from the viewpoint of impartability to a semiconductor substrate and pattern formation, and is selected from the group consisting of a terpene solvent. More preferably, it contains at least one selected from the above.

  When the composition for forming a passivation layer includes a liquid medium, the content of the liquid medium is determined in consideration of the imparting property, the pattern forming property, and the storage stability. For example, the content of the liquid medium is preferably 5% by mass to 98% by mass in the total mass of the composition for forming a passivation layer, from the viewpoint of impartability of the composition for forming a passivation layer and pattern forming properties. More preferably, it is 10 mass%-95 mass%.

(resin)
The composition for forming a passivation layer may further contain at least one resin. By including the resin, the shape stability of the passivation layer forming composition layer formed by applying the passivation layer forming composition on the semiconductor substrate is further improved, and the passivation layer is formed by the passivation layer forming composition layer. A desired shape can be formed in the formed region.

The type of resin is not particularly limited. The resin is preferably a resin whose viscosity can be adjusted within a range in which a good pattern can be formed when the composition for forming a passivation layer is applied onto a semiconductor substrate. Specific examples of the resin include polyvinyl alcohol, polyacrylamide, polyacrylamide derivatives, polyvinylamide, polyvinylamide derivatives, polyvinylpyrrolidone, polyethylene oxide, polyethylene oxide derivatives, polysulfonic acid, polyacrylamide alkylsulfonic acid, cellulose, and cellulose derivatives (carboxymethylcellulose). , Cellulose ethers such as hydroxyethyl cellulose and ethyl cellulose), gelatin, gelatin derivatives, starch, starch derivatives, sodium alginate, sodium alginate derivatives, xanthan, xanthan derivatives, guar gum, guar gum derivatives, scleroglucan, scleroglucan derivatives, tragacanth, Tragacanth derivative, dextrin, dextrin derivative, (meta) Examples include crylic acid resin, (meth) acrylic acid ester resin (alkyl (meth) acrylate resin, dimethylaminoethyl (meth) acrylate resin, etc.), butadiene resin, styrene resin, siloxane resin, and copolymers thereof. . These resins are used singly or in combination of two or more.
In the present embodiment, (meth) acryl represents acryl or methacryl, and (meth) acrylate represents acrylate or methacrylate.

Among these resins, from the viewpoint of storage stability and pattern formation, it is preferable to use a neutral resin having no acidic or basic functional group. Even when the content is small, viscosity and thixotropy are easily used. From the viewpoint of adjusting the properties, it is more preferable to use a cellulose derivative.
Further, the molecular weight of these resins is not particularly limited, and it is preferable to adjust appropriately in view of the desired viscosity as the composition for forming a passivation layer. The weight average molecular weight of the resin is preferably 1,000 to 10,000,000, and more preferably 1,000 to 5,000,000, from the viewpoints of storage stability and pattern formation. In addition, the weight average molecular weight of resin is calculated | required by converting using the analytical curve of a standard polystyrene from the molecular weight distribution measured using GPC (gel permeation chromatography).

The content of the resin in the composition for forming a passivation layer can be appropriately selected as necessary.
For example, when the composition for forming a passivation layer contains a resin, the content of the resin is preferably 0.1% by mass to 50% by mass in the total mass of the composition for forming a passivation layer. From the viewpoint of expressing thixotropy that facilitates pattern formation, the resin content is more preferably 0.2% by mass to 25% by mass, and 0.5% by mass to 20% by mass. Is more preferable, and it is particularly preferably 0.5% by mass to 15% by mass.
In addition, since the composition for forming a passivation layer is excellent in thixotropy, it is not necessary to develop thixotropy with a resin. Therefore, the content of the resin contained in the composition for forming a passivation layer is preferably 0.5% by mass or less, more preferably 0.2% by mass or less, still more preferably 0.1% by mass or less, and substantially a resin. It is particularly preferred not to contain.

(Other ingredients)
The composition for forming a passivation layer may further contain other components that are usually used in the field as necessary, in addition to the components described above.
The composition for forming a passivation layer may contain an acidic compound or a basic compound. When the composition for forming a passivation layer contains an acidic compound or a basic compound, from the viewpoint of storage stability, the content of the acidic compound or the basic compound is 1% by mass or less in the composition for forming a passivation layer, respectively. It is preferable that the content is 0.1% by mass or less.
Examples of acidic compounds include Bronsted acid and Lewis acid. Specific examples include inorganic acids such as hydrochloric acid and nitric acid, and organic acids such as acetic acid. Examples of basic compounds include Bronsted bases and Lewis bases. Specifically, examples of the basic compound include inorganic bases such as alkali metal hydroxides and alkaline earth metal hydroxides, and organic bases such as trialkylamine and pyridine.

  Examples of other components include plasticizers, dispersants, surfactants, thixotropic agents, other metal alkoxide compounds, and high-boiling materials. Among these, it is preferable to include at least one selected from thixotropic agents. By including at least one selected from thixotropic agents, the shape stability of the composition layer for forming a passivation layer formed by applying the composition for forming a passivation layer on a semiconductor substrate is further improved, and a passivation layer is formed. It can be formed in a desired shape in the region where the composition layer for forming a passivation layer is formed.

  Examples of thixotropic agents include fatty acid amides, polyalkylene glycol compounds, organic fillers, and inorganic fillers. Examples of the polyalkylene glycol compound include compounds represented by the following general formula (III).

R _< ⁶ _> -(O-R _< ⁸ _> ) _n- O-R _< ⁷ _> ... (III)

In general formula (III), R ⁶ and R ⁷ each independently represent a hydrogen atom or an alkyl group, and R ⁸ represents an alkylene group. n is an arbitrary integer of 3 or more. Incidentally, R ⁸ in the presence of a plurality of (O-R ⁸⁾ may or may not be the same.

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

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

In general formulas (1), (2), (3) and (4), R ⁹ and R ¹¹ each independently represent an alkyl group or alkenyl group having 1 to 30 carbon atoms, and R ¹⁰ represents 1 to ¹⁰ carbon atoms. Represents an alkylene group. R ⁹ and R ¹¹ may be the same or different.

  As an organic filler, the particle | grains of an acrylic resin, a cellulose resin, and a polystyrene resin are mentioned, for example.

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

The volume average particle diameter of the organic filler or inorganic filler is preferably 0.01 μm to 50 μm.
In this embodiment, the volume average particle diameter of the filler can be measured by a laser diffraction scattering method.

  Examples of other metal alkoxide compounds include titanium alkoxide, zirconium alkoxide, and silicon alkoxide.

(High boiling point material)
In the composition for forming a passivation layer, a high boiling point material may be used together with the resin or as a material replacing the resin. The high boiling point material is preferably a compound that is easily vaporized when heated and does not need to be degreased. Further, the high boiling point material is particularly preferably a high boiling point high boiling material capable of maintaining the shape of the passivation layer forming composition layer after application of the passivation layer forming composition. An example of a material that satisfies these conditions is isobornylcyclohexanol.

  Isobornylcyclohexanol is commercially available as “Telsolve MTPH” (Nippon Terpene Chemical Co., Ltd., trade name). Isobornylcyclohexanol has a boiling point as high as 308 ° C to 318 ° C, and when removing it from the passivation layer forming composition layer, it does not need to be degreased by heat treatment (firing) like a resin, but by heating It can be eliminated by vaporization. For this reason, most of the solvent and isobornyl cyclohexanol contained in the composition for forming a passivation layer as necessary can be removed in the drying step after coating on the semiconductor substrate.

  When the composition for forming a passivation layer contains a high-boiling material, the content of the high-boiling material is preferably 3% by mass to 95% by mass in the total mass of the composition for forming a passivation layer, and 5% by mass. More preferably, it is -90 mass%, and it is still more preferable that it is 7 mass%-80 mass%.

  The composition for forming a passivation layer may contain at least one oxide selected from the group consisting of alkaline earth metal elements, transition metal elements, boron, silicon, phosphorus, arsenic, and tellurium.

The viscosity of the composition for forming a passivation layer is not particularly limited, and can be appropriately selected depending on a method for applying the composition to a semiconductor substrate. For example, the viscosity of the composition for forming a passivation layer can be 0.01 Pa · s to 100,000 Pa · s. Among these, from the viewpoint of pattern formability, the viscosity of the composition for forming a passivation layer is preferably 0.1 Pa · s to 10000 Pa · s. The viscosity is measured at 25 ° C. and a shear rate of 1.0 s ⁻¹ using a rotary shear viscometer.

There is no restriction | limiting in particular in the manufacturing method of the composition for formation of a passivation layer. For example, it can be produced by mixing the compound of formula (I) with water, an organoaluminum compound, a liquid medium, a resin, and the like that are contained as necessary by a commonly used mixing method.
The components contained in the composition for forming a passivation layer and the content of each component are confirmed using thermal analysis such as TG / DTA, spectral analysis such as NMR and IR, and chromatographic analysis such as HPLC and GPC. can do.

<Solar cell element>
The solar cell element of this embodiment is obtained by the manufacturing method of the solar cell element of this embodiment. The solar cell element of this embodiment has a semiconductor substrate and a passivation layer and an oxide film layer provided on at least one surface of the semiconductor substrate. The solar cell element of this embodiment preferably has a configuration including a semiconductor substrate, an oxide film layer, and a passivation layer in this order.
The solar cell element of this embodiment has the passivation layer and oxide film layer which consist of the heat processing thing (baking thing) of the composition for formation of the passivation layer containing a formula (I) compound, and shows the outstanding passivation effect.

The semiconductor substrate used for the solar cell element of this embodiment may have a pn junction. The pn junction of the semiconductor substrate used in the solar cell element of this embodiment means a portion where the p-type layer (p-type region) and the n-type layer (n-type region) are in contact. The p-type layer and the n-type layer may exist on different surfaces of the semiconductor substrate or may exist on the same surface. The method for forming the pn junction on the semiconductor substrate is not particularly limited. The surface of the semiconductor substrate on which the passivation layer is provided may be a p-type layer or an n-type layer. From the viewpoint of conversion efficiency, a p-type layer is preferable.
The oxide film layer and the passivation layer are preferably provided on at least one selected from the group consisting of a p-type layer and an n-type layer existing on the surface of the semiconductor substrate. The solar cell element may further include other components as necessary.

An electrode may be disposed on at least one of the p-type layer and the n-type layer in the semiconductor substrate.
As a method for disposing the electrode on at least one of the p-type layer and the n-type layer in the semiconductor substrate, a commonly used method can be employed. For example, an electrode can be manufactured by applying a paste for forming an electrode such as a silver paste or an aluminum paste to a desired region of a semiconductor substrate and performing a heat treatment (firing) as necessary.

  There is no restriction | limiting in the shape of a solar cell element, a magnitude | size, etc. For example, it is preferable that one side is a square of 125 mm to 156 mm.

Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a sectional view schematically showing an example of a process for producing a solar cell element according to this embodiment. However, this process diagram does not limit the present invention at all.
In addition, the magnitude | size of the member in each figure is notional, The relative relationship of the magnitude | size between members is not limited to this. Moreover, the same code | symbol is provided to the member which has the substantially same function through all the drawings, and the overlapping description may be abbreviate | omitted.

  In FIG. 1A, the p-type semiconductor substrate 1 is washed with an alkaline aqueous solution to remove organic substances, particles, and the like on the surface of the p-type semiconductor substrate 1. Thereby, the passivation effect improves more. As a cleaning method using an alkaline aqueous solution, a method using generally known RCA cleaning and the like can be mentioned.

  Thereafter, as shown in FIG. 1B, the surface of the p-type semiconductor substrate 1 is subjected to alkali etching or the like to form irregularities (also referred to as texture) on the surface. Thereby, reflection of sunlight can be suppressed on the light receiving surface side. For alkali etching, an etching solution composed of NaOH and IPA (isopropyl alcohol) can be used.

Next, as shown in FIG. 1 (3), by thermally diffusing phosphorus or the like on the surface of the p-type semiconductor substrate 1, an n ⁺ -type diffusion layer 2 is formed with a thickness on the order of submicrons, and p A pn junction is formed at the boundary with the mold bulk portion.

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

Thereafter, as shown in FIG. 1 (4), the PSG layer 3 on the light receiving surface and the back surface is removed using an etching solution such as hydrofluoric acid. Further, as shown in FIG. 1 (5), the back surface is separately etched to remove the n ⁺ -type diffusion layer 2 on the back surface.

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

  Moreover, about the back surface, you may planarize the unevenness | corrugation of the back surface surface using alkaline aqueous solutions, such as NaOH.

  Next, as shown in FIG. 1 (7), after applying the passivation layer forming composition to a part of the back surface by screen printing or the like, after drying, heat treatment (baking) is performed at a temperature of 300 ° C. to 900 ° C., A passivation layer 5 is formed.

In FIG. 5, an example of the formation pattern of the passivation layer in the back surface is shown as a schematic plan view. FIG. 7 is an enlarged schematic plan view of a portion A in FIG. FIG. 8 is an enlarged schematic plan view of a portion B in FIG. In the case of the passivation layer formation pattern shown in FIG. 5, as can be seen from FIGS. 7 and 8, the back surface passivation layer 5 is formed in a dot shape except for the portion where the back surface output extraction electrode 7 is formed in a later step. The pattern semiconductor substrate 1 is formed with an exposed pattern. The pattern of the dot-shaped openings is defined by the dot diameter (L _a ) and the dot interval (L _b ), and is preferably arranged regularly. Dot diameter _{(L a)} and the dot interval _{(L b)} can be arbitrarily set, in view of suppressing the recombination of the passivation effect and minority carriers, that _{L a} is _{L b} in 5μm~2mm is 10μm~3mm preferably, more preferably _{L a} is _{L b} is 20μm~2.5mm in 10Myuemu～1.5Mm, it is more preferable _{L a} is _{L b} in 20μm~1.3mm is 30Myuemu～2mm.

In the case where the composition for forming a passivation layer has an excellent pattern forming property, the dot diameter (L _a ) and the dot interval (L _b ) are more regularly arranged in this dot-like opening pattern. For this reason, a preferable dot-shaped opening pattern can be formed by suppressing minority carrier recombination, and the power generation efficiency of the solar cell element is improved.

Further, the pattern of the openings may be linear, and FIG. 9 is an enlarged schematic plan view of the portion A of FIG. 5 in that case, and FIG. 10 is an enlarged schematic plan view of the portion B of FIG. In the case of the formation pattern of the passivation layer shown in FIG. 5, as can be seen from FIGS. 9 and 10, the passivation layer 5 on the back surface is p-shaped in a line shape except for a portion where the back surface output extraction electrode 7 is formed in a later step. The pattern semiconductor substrate 1 is formed with an exposed pattern. The pattern of the line openings is defined by the line width (L _a ) and the line interval (L _b ), and is preferably arranged regularly. The line width _{(L a)} and line spacing _{(L b)} can be arbitrarily set, in view of suppressing the recombination of the passivation effect and minority carriers, that _{L a} is _{L b} in 5μm~2mm is 10μm~3mm preferably, more preferably _{L a} is _{L b} is 20μm~2.5mm in 10Myuemu～1.5Mm, it is more preferable _{L a} is _{L b} in 20μm~1.3mm is 30Myuemu～2mm.

  Here, the passivation layer having a desired shape is formed by applying the composition for forming a passivation layer to a portion where the passivation layer is to be formed (portion other than the opening) and heat-treating (sintering). On the other hand, the passivation layer forming composition can be applied to the entire surface including the opening, and the passivation layer in the opening can be selectively removed by laser, photolithography, or the like after heat treatment (firing). Moreover, the composition for forming a passivation layer can be selectively applied by previously masking a portion such as an opening where a composition for forming a passivation layer is not desired to be applied with a mask material.

  Next, as shown in FIG. 1 (8), a silver electrode paste containing glass particles is applied to the light receiving surface by screen printing or the like. FIG. 4 is a schematic plan view showing an example of the light receiving surface of the solar cell element. As shown in FIG. 4, the light receiving surface electrode includes a light receiving surface current collecting electrode 8 and a light receiving surface output extraction electrode 9. In order to secure a light receiving area, it is necessary to suppress the formation area of these light receiving surface electrodes. In addition, from the viewpoint of the resistivity and productivity of the light receiving surface electrode, the width of the light receiving surface current collecting electrode 8 is preferably 10 μm to 250 μm, and the width of the light receiving surface output extraction electrode 9 is preferably 100 μm to 2 mm. In FIG. 4, two light receiving surface output extraction electrodes 9 are provided. However, from the viewpoint of minority carrier extraction efficiency (power generation efficiency), the number of light receiving surface output extraction electrodes 9 may be three or four. it can.

On the other hand, as shown in FIG. 1 (8), an aluminum electrode paste containing glass powder and a silver electrode paste containing glass particles are applied to the back surface by screen printing or the like. FIG.
These are the schematic plan views which show an example of the back surface of a solar cell element. Although the width | variety of the back surface output extraction electrode 7 is not restrict | limited in particular, From viewpoints, such as the connectivity of the wiring member in the manufacturing process of a later solar cell, it is preferable that the width | variety of the back surface output extraction electrode 7 is 100 micrometers-10 mm.

  After applying the electrode paste to the light receiving surface and the back surface, respectively, after drying, the light receiving surface and the back surface are heat-treated (fired) at a temperature of about 450 ° C. to 900 ° C. in the air, and the light receiving surface collecting electrode is applied to the light receiving surface. 8 and the light receiving surface output extraction electrode 9, and the back surface collecting aluminum electrode 6 and the back surface output extraction electrode 7 are formed on the back surface, respectively.

After heat treatment (firing), as shown in FIG. 1 (9), on the light receiving surface, the glass particles contained in the silver electrode paste forming the light receiving surface electrode react with the antireflection film 4 (fire through), The light-receiving surface electrode (light-receiving surface current collecting electrode 8, light-receiving surface output extraction electrode 9) and the n ⁺ -type diffusion layer 2 are electrically connected (ohmic contact). On the other hand, on the back surface, in the portion where the p-type semiconductor substrate 1 is exposed in the form of dots or lines (the portion where the passivation layer 5 is not formed), the aluminum in the aluminum electrode paste is converted into p-type semiconductor substrate by heat treatment (firing). By diffusing into 1, the p ⁺ -type diffusion layer 10 is formed. In this embodiment, by using the composition for forming a passivation layer according to this embodiment having excellent pattern formability, a passivation layer having excellent passivation effect can be formed by a simple method, and a solar cell element having excellent power generation performance Can be manufactured.

FIG. 2 is a cross-sectional view schematically showing another example of the method for manufacturing a solar cell element according to the present embodiment, and the n ⁺ -type diffusion layer 2 on the back surface is removed by an etching process. Later, the solar cell element can be manufactured in the same manner as in FIG. 1 except that the back surface is further flattened. When flattening, a technique such as immersing the back surface of the semiconductor substrate in a mixed solution of nitric acid, hydrofluoric acid and acetic acid or a potassium hydroxide solution can be used.

FIG. 3 is a sectional view schematically showing another process example of the method for manufacturing the solar cell element of the present embodiment. This method is the same as the method of FIG. 1 until the step of forming the texture structure, the n ⁺ -type diffusion layer 2 and the antireflection film 4 on the semiconductor substrate 1 (FIGS. 3 (19) to (24)).

After forming the antireflection film 4, as shown in FIG. 3 (25), a passivation layer forming composition is applied, and after drying, heat treatment (baking) is performed at a temperature of 300 ° C. to 900 ° C. Form.
FIG. 6 shows a schematic plan view of another example of the formation pattern of the passivation layer on the back surface. In the formation pattern of the passivation layer shown in FIG. 6, openings are arranged on the entire back surface, and openings are also arranged on the portion where the back surface output extraction electrode is formed in a later step.

Thereafter, as shown in FIG. 3 (26), boron or aluminum is diffused from the portion where the p-type semiconductor substrate 1 is exposed in the form of dots or lines on the back surface (the portion where the passivation layer 5 is not formed). ^{A +} type diffusion layer 10 is formed. When boron is diffused when forming the p ⁺ -type diffusion layer 10, a method of treating at a temperature around 1000 ° C. in a gas containing boron trichloride (BCl ₃ ) can be used. However, since the gas diffusion method is the same as in the case of using phosphorus oxychloride, the p ⁺ -type diffusion layer 10 is formed on the light-receiving surface, the back surface, and the side surface of the substrate. It is necessary to take measures such as masking the other portions to prevent boron from diffusing into unnecessary portions of the p-type semiconductor substrate 1.

In addition, when aluminum is diffused when forming the p ⁺ -type diffusion layer 10, an aluminum paste is applied to the entire back surface or the opening, and this is heat-treated (fired) at a temperature of 450 ° C. to 900 ° C. The p ⁺ type diffusion layer 10 is formed by diffusing aluminum, and then a heat treatment layer (baked product layer) made of an aluminum paste on the p ⁺ type diffusion layer 10 is etched with hydrochloric acid or the like.

  Next, as shown in FIG. 3 (27), aluminum is physically vapor-deposited on the entire back surface to form the back surface collecting aluminum electrode 11.

  Thereafter, as shown in FIG. 3 (28), a silver electrode paste containing glass particles is applied to the light receiving surface by screen printing or the like, and a silver electrode paste containing glass particles is applied to the back surface by screen printing or the like. . The silver electrode paste on the light receiving surface is applied in a pattern according to the shape of the light receiving surface electrode shown in FIG. 4, and the silver electrode paste on the back surface is applied in a pattern according to the shape of the back electrode shown in FIG.

After applying the electrode paste to each of the light receiving surface and the back surface, after drying, the light receiving surface and the back surface are both heat-treated (fired) at a temperature of about 450 ° C. to 900 ° C. in the atmosphere, as shown in FIG. A light receiving surface collecting electrode 8 and a light receiving surface output extraction electrode 9 are formed on the light receiving surface, and a back surface output extraction electrode 7 is formed on the back surface. At this time, the light receiving surface electrode and the n ⁺ -type diffusion layer 2 are electrically connected on the light receiving surface, and the back surface collecting aluminum electrode 11 and the back surface output extraction electrode 7 formed by vapor deposition are electrically connected on the back surface. Is done.

<Solar cell>
The solar cell of this embodiment includes at least one of the solar cell elements of this embodiment. The solar cell of this embodiment is configured by arranging a wiring member on the electrode of the solar cell element as necessary. That is, the solar cell of this embodiment may have a solar cell element and a wiring member disposed on the electrode of the solar cell element.
The solar cell of the present embodiment is configured by further connecting a plurality of solar cell elements via a wiring member as necessary, and further sealing with a sealing material. The wiring member and the sealing material are not particularly limited, and can be appropriately selected from those usually used in the technical field.

  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, “%” is based on mass.

(Preparation of composition 1 for forming a passivation layer)
2.037 g of pentaethoxyniobium (Hokuko Chemical Co., Ltd., structural formula: Nb (OC ₂ H ₅ ) ₅ , molecular weight: 318.2), aluminum ethyl acetoacetate diisopropylate (Kawaken Fine Chemical Co., Ltd., trade name: ALCH) 3.504 g, titanium tetraisopropoxide (Wako Pure Chemical Industries, Ltd.) 4.249 g, terpineol (Nippon Terpene Chemical Co., Ltd., sometimes abbreviated as TPO) 23.540 g, isobornylcyclo 64.489 g of hexanol (Nippon Terpene Chemical Co., Ltd., sometimes abbreviated as tersolve) is mixed and kneaded for 5 minutes, and then 2.182 g of pure water is added and further kneaded for 5 minutes to form a passivation layer forming composition 1 Was prepared.

Example 1
A texture structure was formed by alkali etching on both surfaces (light-receiving surface and back surface) of a single crystal p-type semiconductor substrate (156 mm square, thickness 200 μm). Next, treatment was performed at a temperature of 900 ° C. for 20 minutes in a mixed gas atmosphere of phosphorus oxychloride (POCl ₃ ), nitrogen, and oxygen to form n ⁺ -type diffusion layers on the light-receiving surface, the back surface, and the side surfaces. Thereafter, side etching was performed to remove the side silicate glass (PSG) layer and the n ⁺ -type diffusion layer, and the PSG layer on the light-receiving surface and the back surface was removed using an etching solution containing hydrofluoric acid. Further, the back surface was separately etched to remove the n ⁺ -type diffusion layer on the back surface. Thereafter, an antireflection film made of silicon nitride was formed on the n ⁺ type diffusion layer on the light receiving surface so as to have a thickness of about 90 nm by plasma CVD (PECVD). Further, the back surface was immersed in an aqueous NaOH solution at 80 ° C. for 4 minutes to flatten the surface.

The prepared composition 1 for forming a passivation layer was printed using a printing machine (LZ-0913, Neurong Seimitsu Kogyo Co., Ltd.). Thereafter, the semiconductor substrate provided with the composition 1 for forming a passivation layer was heated at 150 ° C. for 5 minutes to dry the liquid medium by evaporating. Next, the semiconductor substrate was heat-treated (baked) at a temperature of 800 ° C. for 10 minutes and then allowed to cool at room temperature (25 ° C.). The heat treatment (firing) was performed using a diffusion furnace (horizontal system 206A-M100 type, Koyo Thermo System Co., Ltd.) under the conditions of the atmospheric temperature, maximum temperature 800 ° C., and holding time 10 minutes. Moreover, the result of having observed the cross section of the semiconductor substrate at that time with the transmission electron microscope (H-90000NAR made from Hitachi High-Technologies) is shown in FIG.
In FIG. 13, a layer described as Si indicates a semiconductor substrate. The layer described as SiOx indicates an oxide film layer. The layer described as Mox represents a passivation layer.
The thickness of the oxide film layer (oxide film thickness) was determined from the result of observing the cross section of the semiconductor substrate with a transmission electron microscope (H-90000NAR manufactured by Hitachi High-Technologies).

  Next, an antireflection film made of silicon nitride was formed as a back surface protection film by plasma CVD (PECVD) so as to have a thickness of about 130 nm.

  The pattern of the opening was formed so as to have the pattern shown in FIGS. Specifically, an opening was made with a laser so that the semiconductor substrate was exposed at the line-shaped opening in the region where the back surface output extraction electrode (reference numeral 7 in FIG. 11) was formed. The line-shaped opening pattern had a line width (La) of 40 μm and a line interval (Lb) of 700 μm.

  Next, a commercially available aluminum electrode paste (PASE-1203, MONOCRYSTAl) was applied to the entire back surface of the semiconductor substrate by screen printing. This was heated at a temperature of 150 ° C. for 5 minutes to evaporate the liquid medium, thereby performing a drying treatment.

  Next, a commercially available silver electrode paste (PV-17F, DuPont) was applied to the light receiving surface of the semiconductor substrate so as to have the electrode pattern shown in FIG. 4 by screen printing. The electrode pattern is composed of a light receiving surface collecting electrode having a width of 120 μm and a light receiving surface output extraction electrode having a width of 1.5 mm. This was heated at a temperature of 150 ° C. for 5 minutes to evaporate the liquid medium, thereby performing a drying treatment.

  The printing conditions (screen plate mesh, printing speed and printing pressure) of the silver electrode paste and the aluminum electrode paste were as follows: back surface output extraction electrode after heat treatment (firing) (silver electrode, symbol 7 in FIG. 11) and back surface current collection The thickness of the electrodes for use (aluminum electrode, symbol 6 in FIG. 11) was adjusted appropriately so as to be 20 μm. After the application of each electrode paste, drying was performed by heating at a temperature of 150 ° C. for 5 minutes to evaporate the liquid medium.

  Subsequently, heat treatment (firing) was performed using a tunnel furnace (single-line transport W / B tunnel furnace, Noritake Co., Ltd.) under atmospheric conditions at a maximum temperature of 800 ° C. and a holding time of 10 seconds. The solar cell element 1 in which the electrode was formed was produced.

(Production of solar cells)
On the light-receiving surface output extraction electrode and the back surface output extraction electrode of the solar cell element 1 obtained above, a wiring member (solder-plated rectangular wire for solar cell, product name: SSA-TPS 0.2 × 1.5 (20 ), A copper wire with a thickness of 0.2 mm x a width of 1.5 mm, a Sn-Ag-Cu-based lead-free solder plated with a maximum thickness of 20 μm per side, Hitachi Metals, Ltd.), and a tab wire connection device ( NTS-150-M, Tabbing & Stringing Machine, NPC Co., Ltd.) and melting the solder under the conditions of a maximum temperature of 250 ° C. and a holding time of 10 seconds, the wiring member, the light receiving surface output extraction electrode, and the back surface output The extraction electrode was connected.

  Then, the solar cell 1 of the structure shown in FIG. 12 was produced using the glass plate (white plate tempered glass 3KWE33, Asahi Glass Co., Ltd.), the sealing material (ethylene vinyl acetate; EVA), and the back sheet. Specifically, the solar cell element 12 to which the glass plate 16, the sealing material 14, and the wiring member 13 are connected, the sealing material 14 and the back sheet 15 are superposed in this order, and this is laminated with a vacuum laminator (LM-50 × 50, The solar cell 1 was produced by vacuum lamination at 140 ° C. for 5 minutes so that a part of the wiring member 13 was exposed.

Evaluation of the solar cell characteristics (power generation performance) of the produced solar cell 1 includes pseudo-sunlight (WXS-155S-10, Wacom Electric Co., Ltd.) and a voltage-current (IV) evaluation measuring instrument (IV). CURVE TRACER MP-180, Hidehiro Seiki Co., Ltd.) was used in combination. Jsc (short circuit current), Voc (open voltage), F. F. (Curve factor) and η (conversion efficiency) are obtained by measuring in accordance with JIS-C-8913 (2005) and JIS-C-8914 (2005), respectively. The measured value of the solar cell (solar cell C1) having a passivation layer of aluminum oxide (Al ₂ O ₃ ) formed by the ALD method, which was prepared in Comparative Example 1 shown later, is 100.0. The relative value was converted. The obtained results are shown in Table 1.

<Example 2>
In Example 1, the oxide film layer was formed after the substrate was planarized, and the rest was the same as Example 1. Specifically, using a diffusion furnace (horizontal system 206A-M100 type, Koyo Thermo System Co., Ltd.), heating was performed at 550 ° C. for 20 minutes in an oxygen atmosphere to form an oxide film layer, thereby producing solar cell 2. . Table 1 shows the evaluation results evaluated in the same manner as in Example 1.

<Comparative Example 1>
In Example 1, an oxide film layer was formed after planarizing the substrate, and then an aluminum oxide layer was formed by ALD instead of applying a passivation layer forming composition. Specifically, using a diffusion furnace (horizontal system 206A-M100 type, Koyo Thermo System Co., Ltd.), an oxide film layer was formed by heating at 550 ° C. for 20 minutes in an oxygen atmosphere. Thereafter, an aluminum oxide layer was formed by ALD, and heated at 700 ° C. for 20 minutes using the same diffusion furnace. A solar cell C1 was produced in the same manner as in Example 1 except that the oxide film layer and the aluminum oxide layer were formed by the ALD method. Table 1 shows the evaluation results evaluated in the same manner as in Example 1.

<Comparative example 2>
In Comparative Example 1, a solar cell C2 was produced in the same manner as in Comparative Example 1 except that the oxide film layer was not formed after the substrate was flattened. Table 1 shows the evaluation results evaluated in the same manner as in Example 1.

  Comparing Example 1 and Example 2, Example 1 without the oxide film formation process shows higher characteristics. On the other hand, in the comparative example, the comparative example 2 without the oxide film formation process shows lower characteristics than the comparative example 1 with the oxide film formation process. Further, it can be confirmed from FIG. 13 that the oxide film layer is formed in Example 1. From this, it can be seen that the oxide film can be formed without the oxide film formation process by using the passivation layer forming composition according to the present embodiment.

  As mentioned above, according to the manufacturing method of the solar cell element of this embodiment, the solar cell element which has a passivation layer and an oxide film layer which can form an oxide film layer by a simple method can be obtained.

1: p-type semiconductor substrate, 2: n ⁺ -type diffusion layer, 3: PSG (phosphorus silicate glass) layer, 4: antireflection film, 5: passivation layer, 6: aluminum electrode paste, or heat-treated (fired) Back surface collecting aluminum electrode, 7: Back surface output extraction electrode paste, or back surface output extraction electrode obtained by heat treatment (baking), 8: Light receiving surface current collection electrode paste, or light receiving surface current collection obtained by heat treatment (firing) Electrode: 9: light receiving surface output extraction electrode paste, or light receiving surface output extraction electrode obtained by heat treatment (baking), 10: p ⁺ type diffusion layer, 11: aluminum electrode for backside current collection, 12: solar cell element, 13 : Wiring member, 14: Sealing material, 15: Back sheet, 16: Glass plate

Claims (7)

Applying a passivation layer forming composition containing a compound represented by the following general formula (I) on a semiconductor substrate;
Heat-treating the composition for forming a passivation layer,
The manufacturing method of the solar cell element which has a passivation layer and an oxide film layer.
M (OR ¹ ) _m (I)
[In General Formula (I), M represents at least one selected from the group consisting of Al, Nb, Ta, VO, Y, and Hf. R ¹ independently represents an alkyl group or an aryl group. m represents an integer of 1 to 5. ]   The method for manufacturing a solar cell element according to claim 1, wherein the composition for forming a passivation layer contains water.   The manufacturing method of the solar cell element of Claim 1 or Claim 2 in which the said composition for passivation layer formation contains the hydrolyzate of the compound represented by the said general formula (I).   4. The composition according to claim 1, wherein the composition for forming a passivation layer further comprises a compound having an oxygen atom other than the compound represented by the general formula (I) in the molecular structure. Manufacturing method of solar cell element. The manufacturing method of the solar cell element of Claim 4 with which the compound which has the said oxygen atom in molecular structure contains the compound represented by the following general formula (II).

[In General Formula (II), each R ² independently represents an alkyl group. n represents an integer of 1 to 3. X ² and X ³ each independently represent an oxygen atom or a methylene group. R ³ , R ⁴ and R ⁵ each independently represents a hydrogen atom or an alkyl group. ]   The solar cell element obtained by the manufacturing method of the solar cell element of any one of Claims 1-5.   A solar cell comprising the solar cell element according to claim 6.