JPWO2014014111A1 - Solar cell element, method for manufacturing solar cell element, and solar cell module - Google Patents

Abstract

A light receiving surface, a semiconductor substrate having a back surface opposite to the light receiving surface, and a side surface; a light receiving surface electrode disposed on the light receiving surface; a back electrode disposed on the back surface; the light receiving surface; And a passivation layer containing at least one compound selected from the group consisting of Nb2O5, Ta2O5, V2O5, Y2O3, and HfO2 and disposed on at least one of the back surface and the side surface.

Description

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

The manufacturing process of the conventional silicon solar cell element is demonstrated.
First, a p-type silicon substrate having a texture structure formed on the light-receiving surface side is prepared so as to promote the light confinement effect and increase the efficiency, and then in a mixed gas atmosphere of phosphorus oxychloride (POCl ₃ ), nitrogen and oxygen An n-type diffusion layer is uniformly formed by performing several tens of minutes at 800 ° C. to 900 ° C. In this conventional method, since phosphorus is diffused using a mixed gas, n-type diffusion layers are formed not only on the front surface, which is the light receiving surface, but also on the side surface and the back surface. Therefore, side etching is performed to remove the n-type diffusion layer formed on the side surface. Further, 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 particles 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, an aluminum electrode formed from an aluminum paste has low conductivity. Therefore, in order to reduce the sheet resistance, the aluminum electrode formed on the entire back surface usually must have a thickness of about 10 μm to 20 μm after heat treatment (firing). Furthermore, since the thermal expansion coefficient of silicon and aluminum differ greatly, a silicon substrate on which an aluminum electrode is formed generates a large internal stress in the process of heat treatment (firing) and cooling, resulting in damage to grain boundaries, Causes defects to grow and warp.

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

In relation to the above, a point contact method has been proposed in which an aluminum paste is applied to a part of the surface of a silicon substrate to partially form a p ⁺ -type diffusion layer and an aluminum electrode (for example, Japanese Patent No. 3107287). (See the publication).
In the case of a solar cell having a point contact structure on the surface opposite to the light receiving surface (hereinafter also referred to as “back surface”), it is necessary to suppress the recombination rate of minority carriers on the surface of the portion other than the aluminum electrode. is there. For this purpose, a SiO ₂ film or the like has been proposed as a passivation layer for the back surface (see, for example, JP-A-2004-6565). 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, Japanese Patent No. 4767110).
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, Journal of Applied Physics, 104 (2008), 113703, 113703). 113703-7). As a simple method for forming an aluminum oxide film on a semiconductor substrate, a sol-gel method has been proposed (for example, Thin Solid Films, 517 (2009), 6327-6330, and Chinese Physics Letters, 26 (2009)). ), 088102-1 to 088102-4).

  The method described in Journal of Applied Physics, 104 (2008), 113703-1 to 113703-7 includes a complicated manufacturing process such as vapor deposition, and thus it may be difficult to improve productivity. In the composition for forming a passivation layer used in the methods described in Thin Solid Films, 517 (2009), 6327-6330, and Chinese Physics Letters, 26 (2009), 088102-1 to 088102-4, It is difficult to say that the storage stability is sufficient because of problems such as crystallization.

  The present invention has been made in view of the above-described conventional problems, has a high conversion efficiency, and suppresses a decrease in conversion efficiency over time, a simple manufacturing method thereof, and a solar battery module. It is an issue to provide.

Specific means for solving the above problems are as follows.
<1> a semiconductor substrate having a light receiving surface, a back surface opposite to the light receiving surface, and a side surface;
A light-receiving surface electrode disposed on the light-receiving surface;
A back electrode disposed on the back surface;
At least one selected from the group consisting of Nb ₂ O ₅ , Ta ₂ O ₅ , V ₂ O ₅ , Y ₂ O ₃ and HfO ₂ disposed on at least one of the light receiving surface, the back surface and the side surface. A passivation layer containing seed compounds;
A solar cell element having

<2> The solar cell element according to <1>, wherein the passivation layer further contains Al ₂ O ₃ .

<3> The solar cell element according to <1> or <2>, wherein the passivation layer is a heat-treated product of the composition for forming a passivation layer.

<4> The composition for forming a passivation layer is composed of Nb ₂ O ₅ , Ta ₂ O ₅ , V ₂ O ₅ , Y ₂ O ₃ , HfO ₂ and a compound represented by the following general formula (I). The solar cell element according to <3>, containing at least one selected compound.

M (OR ¹ ) _m (I)

In formula (I), M contains at least one metal element selected from the group consisting of Nb, Ta, V, Y, and Hf. R ¹ each independently represents an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 14 carbon atoms. m represents an integer of 0 to 5.

<5> The passivation layer forming composition contains at least one niobium compound selected from the group consisting of Nb ₂ O ₅ and a compound in which M in the general formula (I) is Nb, and the passivation layer. The solar cell element according to <4>, wherein the total content of the niobium compound in the composition for formation is 0.1% by mass to 99.9% by mass in terms of Nb ₂ O ₅ .

<6> The <3> to <3>, wherein the composition for forming a passivation layer further contains at least one aluminum compound selected from the group consisting of compounds represented by Al ₂ O ₃ and the following general formula (II). The solar cell element as described in any one of <5>.

In formula (II), each R ² independently represents an alkyl group having 1 to 8 carbon atoms. n represents an integer of 0 to 3. X ² and X ³ each independently represent an oxygen atom or a methylene group. R ³ , R ⁴ and R ⁵ each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.

<7> The solar cell element according to <6>, wherein R ² in the general formula (II) is each independently an alkyl group having 1 to 4 carbon atoms.

<8> As described in <6> or <7>, in the general formula (II), 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. Solar cell element.

<9> The composition for forming a passivation layer, wherein the composition for forming a passivation layer contains at least one aluminum compound selected from the group consisting of Al ₂ O ₃ and the compound represented by the general formula (II). The solar cell element as described in any one of said <6>-<8> whose content rate of the said aluminum compound in a thing is 0.1 mass%-80 mass%.

<10> The solar cell element according to any one of <3> to <9>, wherein the composition for forming a passivation layer further contains a liquid medium.

<11> The sun according to <10>, wherein the liquid medium includes at least one selected from the group consisting of a hydrophobic organic solvent, an aprotic organic solvent, a terpene solvent, an ester solvent, an ether solvent, and an alcohol solvent. Battery element.

<12> forming a light receiving surface electrode on the light receiving surface of the semiconductor substrate;
Forming a back electrode on the back surface of the semiconductor substrate opposite to the light receiving surface;
From at least one of the light receiving surface, the back surface and the side surface, Nb ₂ O ₅ , Ta ₂ O ₅ , V ₂ O ₅ , Y ₂ O ₃ , HfO ₂ and a compound represented by the following general formula (I) Forming a composition layer by applying a composition for forming a passivation layer containing at least one compound selected from the group consisting of:
Heat-treating the composition layer to form a passivation layer;
The method for producing a solar cell element according to any one of <1> to <11>, wherein:

M (OR ¹ ) _m (I)

In formula (I), M contains at least one metal element selected from the group consisting of Nb, Ta, V, Y, and Hf. R ¹ each independently represents an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 14 carbon atoms. m represents an integer of 0 to 5.

<13> In the above <12>, the composition for forming a passivation layer further contains at least one aluminum compound selected from the group consisting of compounds represented by Al ₂ O ₃ and the following general formula (II). The manufacturing method of the solar cell element of description.

In formula (II), each R ² independently represents an alkyl group having 1 to 8 carbon atoms. n represents an integer of 0 to 3. X ² and X ³ each independently represent an oxygen atom or a methylene group. R ³ , R ⁴ and R ⁵ each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.

<14> The method for producing a solar cell element according to <12> or <13>, wherein the temperature of the heat treatment is 400 ° C. or higher.

<15> The step according to any one of <12> to <14>, wherein the step of forming the composition layer includes applying the composition for forming a passivation layer by a screen printing method or an inkjet method. A battery element manufacturing method.

<16> The solar cell element according to any one of <1> to <11>,
A wiring material disposed on the electrode of the solar cell element;
A solar cell module.

  ADVANTAGE OF THE INVENTION According to this invention, it can provide the solar cell element which has the outstanding conversion efficiency, and the time-dependent fall of conversion efficiency is suppressed, its manufacturing method, and a solar cell module.

It is sectional drawing which shows typically an example of the manufacturing method of the solar cell element which has a passivation layer concerning this embodiment. It is sectional drawing which shows typically another example of the manufacturing method of the solar cell element which has a passivation layer concerning this embodiment. It is a top view which shows typically the printing pattern of the composition for passivation layer formation in an Example, and the printing pattern of an aluminum electrode. It is a top view which shows typically the printing pattern of the silver electrode in an Example. It is sectional drawing which showed the structure of the double-sided electrode type solar cell element. It is sectional drawing which shows the 1st structural example of the solar cell element which concerns on reference embodiment. It is sectional drawing which shows the 2nd structural example of the solar cell element which concerns on reference embodiment. It is sectional drawing which shows the 3rd structural example of the solar cell element which concerns on reference embodiment. It is sectional drawing which shows the 4th structural example of the solar cell element which concerns on reference embodiment. It is sectional drawing which shows another structural example of the solar cell element which concerns on reference embodiment.

  In this specification, the term “process” is not limited to an independent process, and is included in the term if the intended purpose of the process is achieved even when it cannot be clearly distinguished from other processes. . In the present specification, a numerical range indicated by using “to” indicates a range including the numerical values described before and after “to” as the minimum value and the maximum value, respectively. Further, in the present specification, the content of each component in the composition is the total amount of the plurality of substances present in the composition unless there is a specific notice when there are a plurality of substances corresponding to each component in the composition. Means. In addition, in the present specification, the term “layer” includes a configuration of a shape formed in part in addition to a configuration of a shape formed on the entire surface when observed as a plan view.

<Solar cell element>
The solar cell element of the present invention includes a light receiving surface, a back surface opposite to the light receiving surface, a semiconductor substrate having a side surface, a light receiving surface electrode disposed on the light receiving surface, and a back surface disposed on the back surface. An electrode, disposed on at least one of the light receiving surface, the back surface, and the side surface, and selected from the group consisting of Nb ₂ O ₅ , Ta ₂ O ₅ , V ₂ O ₅ , Y ₂ O _3, and HfO _2. And a passivation layer containing at least one compound (hereinafter also referred to as “specific metal oxide”, and a metal element contained in each specific metal oxide is also referred to as “specific metal element”). The solar cell element may further include other components as necessary.

  A solar cell element having a passivation layer containing a specific metal oxide on at least one of a light receiving surface, a back surface, and a side surface of a semiconductor substrate has excellent conversion efficiency and suppresses a decrease in conversion efficiency over time. . This is considered to be because, for example, since the passivation layer contains a specific metal oxide, an excellent passivation effect is exhibited and the lifetime of carriers in the semiconductor substrate is extended, so that high efficiency can be achieved. Moreover, it is thought that by having the passivation layer containing the specific metal oxide, the passivation effect is maintained, and a decrease in conversion efficiency over time can be suppressed. Here, the deterioration of the solar cell characteristics over time can be evaluated by the solar cell characteristics after being left for a predetermined time in a constant temperature and humidity chamber.

  The reason why the passivation layer containing the specific metal oxide on at least one of the light receiving surface, the back surface, and the side surface of the semiconductor substrate has an excellent passivation effect can be considered as follows. That is, by providing a passivation layer containing a specific metal oxide on the surface of the semiconductor substrate, a fixed charge is generated near the interface with the semiconductor substrate due to defects of a specific metal element or oxygen atom in the specific metal oxide. Is considered to exist. This fixed charge generates an electric field in the vicinity of the interface of the semiconductor substrate, so that band bending occurs and the concentration of minority carriers can be reduced. As a result, since the carrier recombination rate at the interface is suppressed, it is considered that an excellent passivation effect is exhibited.

The fixed charge possessed by the specific metal oxide can be evaluated by the CV method (Capacitance Voltage measurement). When the surface state density of a passivation layer formed by heat-treating a composition for forming a passivation layer, which will be described later, is evaluated by a CV method, the value is larger than that of a passivation layer formed by an ALD method or a CVD method. There is. However, the passivation layer included in the solar cell element of the present invention has a large electric field effect, a decrease in the concentration of minority carriers, and a surface lifetime τ _s increases. Therefore, the surface state density is not a relative problem.

  In this specification, the passivation effect of a semiconductor substrate refers to an effective lifetime of minority carriers in a semiconductor substrate on which a passivation layer is formed, by reflection microwave conduction attenuation using a device such as Nippon Semi-Lab Co., Ltd. or WT-2000PVN. It can be evaluated by measuring by the method.

Here, the effective lifetime τ is expressed by the following equation (A) by the bulk lifetime τ _b inside the semiconductor substrate and the surface lifetime τ _s of the semiconductor substrate surface. When the surface state density on the surface of the semiconductor substrate is small, τ _s becomes long, resulting in a long effective lifetime τ. Further, even if defects such as dangling bonds in the semiconductor substrate are reduced, the bulk lifetime τ _b 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 / τ _b + 1 / τ _s (A)

  In addition, it shows that the recombination rate of a minority carrier is so slow that effective lifetime (tau) is long. Moreover, conversion efficiency improves by comprising a solar cell element using the semiconductor substrate with a long effective lifetime.

The solar cell element includes a semiconductor substrate having a light receiving surface and a back surface opposite to the light receiving surface. The semiconductor substrate is not particularly limited, and can be appropriately selected from those usually used according to the purpose. Examples of the semiconductor substrate include those obtained by doping (diffusing) p-type impurities or n-type impurities into silicon, germanium, or the like. Of these, a silicon substrate is preferable. Further, 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 (that is, at least one of the light receiving surface, the back surface, and the side surface) is a semiconductor substrate that is a p-type layer. Even if the p-type layer on the semiconductor substrate is a p-type layer derived from the p-type semiconductor substrate, 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.

  In the semiconductor substrate, the p-type layer and the n-type layer are preferably pn-junctioned. That is, when the semiconductor substrate is a p-type semiconductor substrate, an n-type layer is preferably formed on the light-receiving surface or the back surface of the semiconductor substrate. When the semiconductor substrate is an n-type semiconductor substrate, a p-type layer is preferably formed on the light-receiving surface or the back surface of the semiconductor substrate. The method for forming the p-type layer or the n-type layer on the semiconductor substrate is not particularly limited, and can be appropriately selected from commonly used methods.

  The thickness in particular of a semiconductor substrate is not restrict | limited, According to the objective, it can select suitably. For example, the thickness of the semiconductor substrate can be 50 μm to 1000 μm, and preferably 75 μm to 750 μm. The shape and size of the semiconductor substrate are not limited, and for example, a square having a side of 125 mm to 156 mm can be used.

  The solar cell element of this invention has the light-receiving surface electrode arrange | positioned on a light-receiving surface, and the back surface electrode arrange | positioned on the back surface on the opposite side to the light-receiving surface of a semiconductor substrate. For example, the light receiving surface electrode has a function of collecting current on the light receiving surface of the semiconductor substrate. The back electrode has a function of outputting a current to the outside, for example.

The material of the light-receiving surface electrode is not particularly limited, and examples thereof include silver, copper, and aluminum. The thickness of the light-receiving surface electrode is not particularly limited, and is preferably 0.1 μm to 50 μm from the viewpoint of conductivity and homogeneity.
The material of the back electrode is not particularly limited, and examples thereof include silver, copper, and aluminum. The material of the back electrode is preferably aluminum from the viewpoint of forming the back electrode and forming a p ⁺ -type diffusion layer by diffusing aluminum atoms in the semiconductor substrate. The thickness of the back electrode is not particularly limited, and is preferably 0.1 μm to 50 μm from the viewpoint of conductivity and warpage of the substrate.

  The light-receiving surface electrode and the back surface electrode can be manufactured by a commonly used method. For example, the light-receiving surface electrode and the back electrode are manufactured by applying an electrode forming paste such as a silver paste, an aluminum paste, or a copper paste to a desired region of a semiconductor substrate, and performing a heat treatment (firing) as necessary. Can do.

The solar cell element of the present invention has a passivation layer containing a specific metal oxide on at least one of the light receiving surface, the back surface, and the side surface of the semiconductor substrate. Furthermore, the passivation layer may contain Al ₂ O ₃ . The passivation layer may be provided on a part or the entire surface of the at least one surface, and is preferably provided in a region other than the electrode. The electrode may be formed so as to overlap with the passivation layer.

  The average thickness of the passivation layer formed on the semiconductor substrate is not particularly limited and can be appropriately selected according to the purpose. For example, the average thickness of the passivation layer is preferably 5 nm to 50 μm, more preferably 10 nm to 30 μm, and still more preferably 15 nm to 20 μm from the viewpoint of the passivation effect. Here, the average thickness of the passivation layer is calculated as an arithmetic average value by measuring the thickness at five points by an ordinary method using an interference film thickness meter (for example, F20 film thickness measurement system manufactured by Filmetrics). The

From the viewpoint of obtaining a sufficient passivation effect, the content of the specific metal oxide contained in the passivation layer is preferably 0.1% by mass to 100% by mass, and 1% by mass to 100% by mass. Is more preferable, and it is still more preferable that it is 10 mass%-100 mass%.
The content rate of the specific metal oxide contained in the passivation layer is measured by the following method. The ratio of the inorganic substance is calculated from the thermogravimetric analysis method using atomic absorption spectrometry, inductively coupled plasma emission spectrometry, thermogravimetric analysis, X-ray photoelectric spectroscopy, or the like. Next, the ratio of the compound of the specific metal element in the inorganic substance is calculated by atomic absorption spectrometry, inductively coupled plasma emission spectrometry, etc., and further the specific metal element in the compound by X-ray photoelectric spectroscopy, X-ray absorption spectroscopy, etc. The ratio of the specific metal oxide is calculated.

  The passivation layer may further contain an inorganic oxide other than the specific metal oxide. Other inorganic oxides are preferably compounds having a fixed charge. Specifically, aluminum oxide, silicon oxide, titanium oxide, gallium oxide, zirconium oxide, boron oxide, indium oxide, phosphorus oxide, zinc oxide, lanthanum oxide , Praseodymium oxide, neodymium oxide, promethium oxide, samarium oxide, europium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, lutetium oxide, etc. From this viewpoint, it is preferably at least one selected from the group consisting of silicon oxide, titanium oxide, zirconium oxide, neodymium oxide and aluminum oxide, and preferably contains at least aluminum oxide. Preferred.

  The content of other inorganic oxides in the passivation layer is preferably 80% by mass or less, and more preferably 60% by mass or less. The content of other inorganic oxides contained in the passivation layer can be measured in the same manner as the above-described method for measuring the content of the specific metal oxide.

The density of the passivation layer, from the viewpoint of temporal stability of the passivation ^effect, preferably ^{1.0g / cm 3 ~8.0g / cm 3} , more preferably ^{2.0g / cm 3 ~6.0g / cm 3} , 3 .0g ^/ cm ³ ~5.0g ^/ cm 3 is more preferred.
The density of the passivation layer is calculated from the area and thickness of the passivation layer and the mass of the passivation layer. Specifically, the density of the passivation layer is measured using a pressure floating method or a temperature floating method.

<Composition for forming a passivation layer>
It is preferable that the passivation layer of the solar cell element of the present invention is a heat-treated product of the composition for forming a passivation layer. The composition for forming a passivation layer is not particularly limited as long as it can form a passivation layer containing a specific metal oxide by heat treatment (firing), and even if the specific metal oxide itself is included, the specific metal The precursor used as an oxide may be included. The specific metal oxide and its precursor are also referred to as a specific metal compound.

From the viewpoint of the high passivation effect, the composition for forming a passivation layer includes the specific metal oxides (Nb ₂ O ₅ , Ta ₂ O ₅ , V ₂ O ₅ , Y ₂ O ₃ and HfO ₂ ), and the specific It is preferable to include at least one compound selected from the group consisting of compounds represented by the following general formula (I) (hereinafter also referred to as compounds of formula (I)) as the metal oxide precursor.

M (OR ¹ ) _m (I)

In formula (I), M contains at least one metal element selected from the group consisting of Nb, Ta, V, Y, and Hf. R ¹ each independently represents an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 14 carbon atoms. m represents an integer of 0 to 5.

In the general formula (I), each R ¹ independently represents an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 14 carbon atoms, preferably an alkyl group having 1 to 8 carbon atoms, and preferably 1 to 4 carbon atoms. The alkyl group 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 group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, t-butyl group, hexyl group, octyl group, 2- An ethylhexyl group etc. can be mentioned. Specific examples of the aryl group represented by R ¹ include a phenyl group.
The alkyl group and aryl group represented by R ¹ may have a substituent. Examples of the substituent for the alkyl group include a halogen atom, an amino group, a hydroxyl group, a carboxyl group, a sulfone group, and a nitro group. Examples of the substituent for the aryl group include a halogen atom, a methyl group, an ethyl group, an isopropyl group, an amino group, a hydroxyl group, a carboxyl group, a sulfone group, and a nitro group.
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 storage stability and a passivation effect.

  In general formula (I), m represents an integer of 0 to 5. m is preferably an integer of 1 to 5 from the viewpoint of storage stability.

  As the compound represented by the general formula (I), it is preferable that M contains at least one metal element selected from the group consisting of Nb, Ta and Y from the viewpoint of the passivation effect. From the viewpoint of making the fixed charge density of the passivation layer negative, M preferably contains at least one metal element selected from the group consisting of Nb, Ta, V, and Hf, and Nb, Ta, VO And at least one selected from the group consisting of Hf.

As the compound of general formula represented by the formula (I), from the viewpoint of storage stability and passivation effect, more preferably R ¹ is an unsubstituted alkyl group having 1 to 4 carbon atoms, the storage stability From the viewpoint, m is preferably an integer of 1 to 5.

  The state of the compound represented by the general formula (I) may be solid or liquid. 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 at room temperature (25 ° C.). And is preferably a liquid.

  Compounds represented by the general formula (I) are niobium, niobium methoxide, niobium ethoxide, niobium isopropoxide, niobium n-propoxide, niobium n-butoxide, niobium t-butoxide, niobium isobutoxide, tantalum methoxide, Tantalum ethoxide, tantalum, tantalum isopropoxide, tantalum n-propoxide, tantalum n-butoxide, tantalum t-butoxide, tantalum isobutoxide, yttrium, yttrium methoxide, yttrium ethoxide, yttrium isopropoxide, yttrium n-propoxy Yttrium n-butoxide, yttrium t-butoxide, yttrium isobutoxide, vanadium, vanadium methoxide oxide, vanadium ethoxide oxide, vanadium isopropoxide Oxide, vanadium n-propoxide oxide, vanadium n-butoxide oxide, vanadium t-butoxide oxide, vanadium isobutoxide oxide, hafnium, hafnium methoxide, hafnium ethoxide, hafnium isopropoxide, hafnium n-propoxide, hafnium n- Examples thereof include butoxide, hafnium t-butoxide, hafnium isobutoxide, etc. Among them, niobium ethoxide, niobium n-propoxide, niobium n-butoxide, tantalum ethoxide, tantalum n-propoxide, tantalum n-butoxide, yttrium isotope Propoxide and yttrium n-butoxide are preferred. From the viewpoint of obtaining a negative fixed charge density, niobium ethoxide, niobium n-propoxide, niobium n-butoxide, tantalum ethoxide, tantalum n-propoxide, tantalum n-butoxide, vanadium ethoxide oxide, vanadium n-propoxy Preference is given to oxides, vanadium n-butoxide oxide, hafnium ethoxide, hafnium n-propoxide and hafnium n-butoxide.

  Moreover, the compound represented by general formula (I) may use what was prepared, or may use a commercial item. 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, Inc. , 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) triethoxy oxide, vanadium (V) tri-i-propoxide oxide, vanadium (V) tri-n-propoxide oxide, vanadium (V 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 Riisobutokishido, it can be mentioned vanadium oxy-tri secondary butoxide and the like.

  In the case of preparing the compound of formula (I) (in the case of m: 1 to 5), the preparation method includes an inert organic compound containing a halide of a specific metal element (M) contained in the compound of formula (I) and an alcohol. A known production method such as a method of reacting in the presence of a solvent and adding ammonia or an amine compound to extract a halogen (JP-A 63-227593 and JP-A 3-291247) can be used. .

  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 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. The mass is preferably 1% by mass, more preferably 1% by mass to 60% by mass, and still more preferably 1% by mass to 50% by mass.

  When the composition for forming a passivation layer contains a compound of m = 1 to 5 in the compound of formula (I) (hereinafter also referred to as a specific metal alkoxide compound), a chelating reagent (chelating agent) is added to the metal alkoxide compound. May be. As a chelating reagent, EDTA (ethylenediaminetetraacetic acid), bipyridine, heme, naphthyridine, benzimidazolylmethylamine, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, tartaric acid, maleic acid, phthalic acid and the like, A β-diketone compound, a β-ketoester compound, and a malonic acid diester can be exemplified.

  Specific examples of chelating agents include acetylacetone, 3-methyl-2,4-pentanedione, 2,3-pentanedione, 3-ethyl-2,4-pentanedione, and 3-butyl-2,4-pentanedione. Β-diketone compounds such as 2,2,6,6-tetramethyl-3,5-heptanedione, 2,6-dimethyl-3,5-heptanedione, 6-methyl-2,4-heptanedione; Methyl acetate, ethyl acetoacetate, propyl acetoacetate, isobutyl acetoacetate, butyl acetoacetate, t-butyl acetoacetate, pentyl acetoacetate, isopentyl acetoacetate, hexyl acetoacetate, n-octyl acetoacetate, heptyl acetoacetate, acetoacetic acid 3 -Pentyl, ethyl 2-acetylheptanoate, ethyl 2-butylacetoacetate, 4,4-dimethyl-3- Ethyl xovalerate, ethyl 4-methyl-3-oxovalerate, ethyl 2-ethylacetoacetate, ethyl hexylacetoacetate, methyl 4-methyl-3-oxovalerate, isopropyl acetoacetate, ethyl 3-oxohexanoate, 3 -Ethyl oxovalerate, methyl 3-oxovalerate, methyl 3-oxohexanoate, ethyl 2-methylacetoacetate, ethyl 3-oxoheptanoate, methyl 3-oxoheptanoate, 4,4-dimethyl-3-oxoyoshi Β-ketoester compounds such as methyl herbate; dimethyl malonate, diethyl malonate, dipropyl malonate, diisopropyl malonate, dibutyl malonate, di-t-butyl malonate, dihexyl malonate, t-butylethyl malonate, methyl malonic acid Diethyl, diethyl ethylmalonate, isopropylmalonate diethyl It can be exemplified butyl diethyl malonate, sec- butyl diethyl malonate, isobutyl diethyl malonate, malonic acid diester, such as 1-methyl butyl diethylmalonate.

  When the specific metal alkoxide compound has a chelate structure, the presence of the chelate structure can be confirmed by a commonly used analysis method. For example, it can be confirmed using an infrared spectrum, a nuclear magnetic resonance spectrum or a melting point.

  The specific metal alkoxide compound may be used in a state of hydrolysis and dehydration condensation polymerization. For hydrolysis and dehydration condensation polymerization, the reaction can proceed in the presence of water and a catalyst. After hydrolysis and dehydration condensation polymerization, water and catalyst may be distilled off. Catalysts include inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, boric acid, phosphoric acid, hydrofluoric acid; and formic acid, acetic acid, propionic acid, butyric acid, oleic acid, linoleic acid, salicylic acid, benzoic acid, phthalic acid, oxalic acid And organic acids such as lactic acid and succinic acid. Moreover, you may add bases, such as ammonia and an amine, as a catalyst.

  The composition for forming a passivation layer may contain other precursors of a specific metal oxide other than the compound of formula (I). The other precursor of a specific metal oxide will not be restrict | limited especially if it becomes a specific metal oxide by heat processing (baking). Specifically, other precursors of specific metal oxides include niobic acid, niobium chloride, niobium monoxide, niobium carbide, niobium hydroxide, tantalum acid, tantalum chloride, tantalum pentabromide, vanadium oxychloride, Divanadium oxide, oxobis (2,4-pentanedionato) vanadium, yttrium chloride, yttrium nitrate, yttrium oxalate, yttrium stearate, yttrium carbonate, yttrium naphthenate, yttrium propionate, yttrium nitrate, yttrium octylate, hafnium chloride And tetrakis (2,4-pentanedionato) hafnium.

  The composition for forming a passivation layer may further contain at least one selected from other inorganic oxides other than the specific metal compound and precursors thereof (hereinafter also referred to as other inorganic compounds). Other inorganic compounds include aluminum oxide, silicon oxide, titanium oxide, gallium oxide, zirconium oxide, boron oxide, indium oxide, phosphorus oxide, zinc oxide, lanthanum oxide, praseodymium oxide, neodymium oxide, promethium oxide, samarium oxide, oxide Examples include europium, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, lutetium oxide, and precursors thereof. From the viewpoint of high passivation effect and suppression of deterioration over time, the other inorganic compound is at least one selected from the group consisting of silicon oxide, titanium oxide, zirconium oxide, neodymium oxide, aluminum oxide, and precursors thereof. In view of further improving the passivation effect, it is more preferable to contain at least one selected from the group consisting of aluminum oxide and its precursor. As a precursor of aluminum oxide, a compound represented by the following general formula (II) is preferable.

Wherein, R ² each independently represent an alkyl group having 1 to 8 carbon atoms. n represents an integer of 0 to 3. X ² and X ³ each independently represent an oxygen atom or a methylene group. R ³ , R ⁴ and R ⁵ each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. Here, when any one of R ^{2 to} R ⁵ , X ² and X ³ is present in plural, groups represented by the same plural symbols may be the same or different from each other.

From the viewpoint of further improving the passivation effect, it contains at least one aluminum compound selected from the group consisting of Al ₂ O ₃ and a compound represented by the following general formula (II) (hereinafter also referred to as an organoaluminum compound). It is preferable.

In general formula (II), R ² each independently represents an alkyl group having 1 to 8 carbon atoms is 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 group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, t-butyl group, hexyl group, octyl group, 2- An ethylhexyl group etc. can be mentioned. 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 the integer of 0-3. From the viewpoint of storage stability, n is preferably an integer of 1 to 3, and more preferably 1 or 3. 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 having 1 to 8 carbon atoms. 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 may have a substituent or may be unsubstituted, and is preferably unsubstituted. The alkyl group represented by R ³ , R ⁴ and R ⁵ is an alkyl group having 1 to 8 carbon atoms, and preferably an alkyl group having 1 to 4 carbon atoms. Specific examples of the alkyl group represented by R ³ , R ⁴ and R ⁵ include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a t-butyl group, and a hexyl group. Octyl group, 2-ethylhexyl group and the like.

Among these, from the viewpoint of storage stability and a passivation effect, R ³ and R ⁴ in the general formula (II) are preferably each independently a hydrogen atom or an unsubstituted alkyl group having 1 to 8 carbon atoms. Or it is more preferable that it is a C1-C4 unsubstituted alkyl group.
R ⁵ in the general formula (II) 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 1 to 4 carbon atoms. It is more preferably an unsubstituted alkyl group.

In the compound represented by the general formula (II), from the viewpoint of storage stability, 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. Is preferred.

The compound represented by the general formula (II) is a compound in which n is 0, R ² is each independently an alkyl group having 1 to 4 carbon atoms, and n is from the viewpoint of storage stability and a passivation effect. 1 to 3, R ² is independently an alkyl group having 1 to 4 carbon atoms, at least one of X ² and X ³ is an oxygen atom, and R ³ and R ⁴ are each independently a hydrogen atom. or an alkyl group having 1 to 4 carbon atoms, it is preferred that R ⁵ is at least one selected from the group consisting of the compounds a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
More preferably, in the compound represented by the general formula (II), n is 0, R ² is an unsubstituted alkyl group having 1 to 4 carbon atoms, and n is 1 to 3, ² is an unsubstituted alkyl group having 1 to 4 carbon atoms, at least one of X ² and X ³ is an oxygen atom, and R ³ or R ⁴ bonded to the oxygen atom is an alkyl group having 1 to ⁴ carbon atoms And when X ² or X ³ is a methylene group, at least one selected from the group consisting of compounds wherein R ³ or R ⁴ bonded to the methylene group is a hydrogen atom and R ⁵ is a hydrogen atom is there.

  Specific examples of the organoaluminum compound (aluminum trialkoxide) represented by the general formula (II) where n is 0 include trimethoxyaluminum, triethoxyaluminum, triisopropoxyaluminum, tri-2-butoxyaluminum, and mono-2-butoxy. -Diisopropoxyaluminum, tri-t-butoxyaluminum, tri-n-butoxyaluminum, etc. can be mentioned.

  Specific examples of the organoaluminum compound represented by the general formula (II), wherein n is 1 to 3, include aluminum ethyl acetoacetate diisopropylate [(ethylacetoacetate) aluminum isopropoxide)], tris (ethyl Acetoacetate) aluminum and the like.

  As the organoaluminum compound represented by the general formula (II) and n of 1 to 3, a prepared product or a commercially available product may be used. Examples of commercially available products include Kawaken Fine Chemical Co., Ltd. trade names, ALCH, ALCH-50F, ALCH-75, ALCH-TR, ALCH-TR-20, and the like.

The organoaluminum compound is preferably an aluminum chelate compound of n = 1 to 3 in the formula (II). The aluminum chelate compound has an aluminum chelate structure in addition to the aluminum alkoxide structure of n = 0.
When the aluminum alkoxide having n = 0 in formula (II) is contained in the composition for forming a passivation layer, it is preferable to contain a chelating reagent (chelating agent) in the composition for forming a passivation layer. Examples of the chelating reagent include the above-mentioned chelating reagents, and compounds having a specific structure having two carbonyl groups such as a β-diketone compound, a β-ketoester compound, and a malonic acid diester are preferable.

  The presence of an alkoxide structure and a chelate structure in the organoaluminum compound can be confirmed by a commonly used analytical method. For example, it can be confirmed using an infrared spectrum, a nuclear magnetic resonance spectrum, a melting point, or the like.

  By using an aluminum alkoxide and a chelating reagent in combination or using a chelated organoaluminum compound, the thermal and chemical stability of the organoaluminum compound is improved, and the transition to aluminum oxide during heat treatment is suppressed. it is conceivable that. As a result, the transition to thermodynamically stable crystalline aluminum oxide is suppressed, and it is considered that amorphous aluminum oxide is easily formed.

  In addition, the state of the metal oxide in the formed passivation layer can be confirmed by measuring an X-ray diffraction spectrum (XRD, X-ray diffraction). For example, it can be confirmed that the XRD has an amorphous structure by not showing a specific reflection pattern. When the composition for forming a passivation layer contains an organoaluminum compound, the aluminum oxide in the passivation layer obtained by heat treatment (firing) preferably has an amorphous structure. When the aluminum oxide is in an amorphous state, aluminum deficiency or oxygen deficiency is likely to occur, fixed charges are likely to be generated in the passivation layer, and a large passivation effect is likely to be obtained.

  An organoaluminum compound represented by the general formula (II) and n is 1 to 3 is prepared by mixing an aluminum trialkoxide in which n is 0 and a compound having a specific structure having two carbonyl groups. Can do. Examples of the compound having a specific structure having two carbonyl groups include the chelating reagent. A commercially available aluminum chelate compound may also be used. When the aluminum trialkoxide and the chelating reagent are mixed, at least a part of the alkoxide group of the aluminum trialkoxide is substituted with a compound having a specific structure to form an aluminum chelate structure. At this time, if necessary, a solvent may be present, or heat treatment or addition of a catalyst 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.

  When the organoaluminum compound has an aluminum chelate structure, the number of aluminum chelate structures is not particularly limited as long as it is 1 to 3. Among these, from the viewpoint of storage stability, it is preferably 1 or 3, and more preferably 1. The number of aluminum chelate structures can be controlled, for example, by appropriately adjusting the mixing ratio of the aluminum trialkoxide and the compound having a specific structure having the two carbonyl groups. Moreover, you may select suitably the compound which has a desired structure from a commercially available aluminum chelate compound.

  Among the compounds represented by the general formula (II), from the viewpoint of the passivation effect and the compatibility with the solvent contained as necessary, specifically, it consists of aluminum ethyl acetoacetate diisopropylate and triisopropoxyaluminum. It is preferable to use at least one selected from the group, and it is more preferable to use aluminum ethyl acetoacetate diisopropylate.

  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.

When the composition for forming a passivation layer contains at least one aluminum compound selected from the group consisting of Al ₂ O ₃ and the compound represented by the general formula (II), the content of the aluminum compound is The content is preferably 0.1% by mass to 80% by mass, and more preferably 10% by mass to 70% by mass. From the viewpoint of further improving the passivation effect, the content of the aluminum compound with respect to the total amount of the specific metal compound, the compound represented by the general formula (II) and Al ₂ O ₃ is 0.1% by mass to 99.9%. The mass is preferably 1% by mass, more preferably 1% by mass to 99% by mass, and still more preferably 2% to 70% by mass.

When the composition for forming a passivation layer contains an aluminum compound, the composition of the metal oxide in the passivation layer obtained by heat-treating the composition for forming the passivation layer includes Nb ₂ O ₅ —Al ₂ O ₃ , Al Binary complex oxides such as ₂ O ₃ —Ta ₂ O ₅ , Al ₂ O ₃ —Y ₂ O ₃ , Al ₂ O ₃ —V ₂ O ₅ , Al ₂ O ₃ —HfO ₂ ; and Nb ₂ O _{5 -Al 2 O 3 -Ta 2 O 5} , Al 2 O 3 -Y 2 O 3 -Ta 2 O 5, Nb 2 O 5 -Al 2 O 3 -V 2 O 5, Al 2 O 3 -HfO 2 -Ta _And ternary complex oxides such as ₂ O ₅ .

The composition for forming a passivation layer preferably contains at least one niobium compound selected from the group consisting of Nb ₂ O ₅ and a compound in which M in the general formula (I) is Nb. When the composition for forming a passivation layer contains the niobium compound, the content of the niobium compound in the composition for forming a passivation layer is 0.1% by mass to 99.9% by mass in terms of Nb ₂ O _5. It is preferably 1% by mass to 99% by mass, and more preferably 30% by mass to 85% by mass.

When the composition for forming a passivation layer contains a niobium compound, the composition of the metal oxide in the passivation layer obtained by heat-treating the composition for forming a passivation layer includes Nb ₂ O ₅ —Al ₂ O ₃ , Nb Binary complex oxides such as ₂ O ₅ —Ta ₂ O ₅ , Nb ₂ O ₅ —Y ₂ O ₃ , Nb ₂ O ₅ —V ₂ O ₅ , Nb ₂ O ₅ —HfO ₂ ; and Nb ₂ O _{5 -Al 2 O 3 -Ta 2 O 5} , Nb 2 O 5 -Y 2 O 3 -Ta 2 O 5, Nb 2 O 5 -Al 2 O 3 -V 2 O 5, Nb 2 O 5 -HfO 2 -Ta _And ternary complex oxides such as ₂ O ₅ . It is.

  The composition for forming a passivation layer is applied to a semiconductor substrate to form a composition layer having a desired shape, and the composition layer is heat-treated (fired) to form a passivation layer having an excellent passivation effect. be able to. In addition, the composition for forming a passivation layer is excellent in storage stability over time because the occurrence of problems such as gelation is suppressed.

(Liquid medium)
The composition for forming a passivation layer preferably contains 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 impartability can be further improved, and a uniform heat treatment layer can be formed. The liquid medium is not particularly limited as long as it can dissolve or disperse the specific metal compound, and can be appropriately selected as necessary. 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 dipropyl ketone, diisobutyl ketone, trimethylnonanone, cyclohexanone, cyclopentanone, methylcyclohexanone, 2,4-pentanedione, acetonylacetone; diethyl ether, methyl ethyl ether, methyl-n-propyl ether, diisopropyl Ether, tetrahydrofuran, methyltetrahydrofuran, dioxane, dimethyldioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol Rudi-n-propyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol methyl n-propyl ether, diethylene glycol methyl n-butyl ether, diethylene glycol di-n-propyl ether, diethylene glycol di- n-butyl ether, diethylene glycol methyl-n-hexyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol methyl ethyl ether, triethylene glycol methyl-n-butyl ether, triethylene glycol di-n-butyl ether, triethylene Glycolme Ru-n-hexyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol methyl ethyl ether, tetraethylene glycol methyl n-butyl ether, tetraethylene glycol di-n-butyl ether, tetraethylene glycol methyl n- Hexyl ether, tetraethylene glycol di-n-butyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol di-n-propyl ether, propylene glycol dibutyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, dipropylene glycol methyl Ethyl ether, dipropylene glycol Cyl-n-butyl ether, dipropylene glycol di-n-propyl ether, dipropylene glycol di-n-butyl ether, dipropylene glycol methyl-n-hexyl ether, tripropylene glycol dimethyl ether, tripropylene glycol diethyl ether, tripropylene glycol methyl Ethyl ether, tripropylene glycol methyl-n-butyl ether, tripropylene glycol di-n-butyl ether, tripropylene glycol methyl-n-hexyl ether, tetrapropylene glycol dimethyl ether, tetrapropylene glycol diethyl ether, tetrapropylene glycol methyl ethyl ether, tetra Propylene glycol methyl-n-butyl ether, tetrapropylene glycol Ether solvents such as alkyl di-n-butyl ether, tetrapropylene glycol methyl-n-hexyl ether, tetrapropylene glycol di-n-butyl ether; methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate Sec-butyl acetate, n-pentyl acetate, sec-pentyl acetate, 3-methoxybutyl acetate, methylpentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, 2- (2-butoxyethoxy) ethyl acetate, benzyl acetate, Cyclohexyl acetate, 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, glycol diacetate, methoxytriethylene glycol acetate, isoamyl acetate, ethyl propionate, n-butyl propionate, isoamyl propionate, diethyl oxalate, di-n-butyl oxalate, methyl lactate, lactic acid Ethyl, n-butyl lactate, n-amyl lactate, ethylene glycol methyl ether propionate, ethylene glycol ethyl ether propionate, ethylene glycol methyl ether acetate, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, propylene glycol ethyl ether Ester solvents such as acetate, propylene glycol propyl ether acetate, γ-butyrolactone, γ-valerolactone; Ril, N-methylpyrrolidinone, N-ethylpyrrolidinone, N-propylpyrrolidinone, N-butylpyrrolidinone, N-hexylpyrrolidinone, N-cyclohexylpyrrolidinone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide, etc. Aprotic polar solvents; hydrophobic organic solvents such as methylene chloride, chloroform, dichloroethane, benzene, toluene, xylene, hexane, octane, ethylbenzene, 2-ethylhexanoic acid, methyl isobutyl ketone, methyl ethyl ketone; methanol, ethanol, n-propanol , Isopropanol, n-butanol, isobutanol, sec-butanol, t-butanol, n-pentanol, isopentanol, 2-methylbutanol, sec-pentanol , T-pentanol, 3-methoxybutanol, n-hexanol, 2-methylpentanol, sec-hexanol, 2-ethylbutanol, sec-heptanol, n-octanol, 2-ethylhexanol, sec-octanol, n- Nonyl alcohol, n-decanol, sec-undecyl alcohol, trimethylnonyl alcohol, sec-tetradecyl alcohol, sec-heptadecyl alcohol, cyclohexanol, methylcyclohexanol, isobornyl cyclohexanol, benzyl alcohol, ethylene glycol, 1, Alcohol solvents such as 2-propylene glycol, 1,3-butylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monophenyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol mono-n-hexyl ether, ethoxytriglycol, tetraethylene glycol mono- Glycol monoether solvents such as n-butyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, tripropylene glycol monomethyl ether; terpinene, terpineol, myrcene, alloocimene, limonene, dipentene, pinene, carvone, Osmen, Terpene solvents such as Erandoren; and water. These liquid media are used alone or in combination of two or more.

  Above all, the liquid medium is at least selected from the group consisting of a hydrophobic organic solvent, an aprotic organic solvent, a terpene solvent, an ester solvent, an ether solvent, and an alcohol solvent from the viewpoint of impartability to a semiconductor substrate and pattern formation. 1 type is preferably included, more preferably at least one selected from the group consisting of terpene solvents, ester solvents, and alcohol solvents, and more preferably at least one selected from the group consisting of terpene solvents. Further preferred.

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

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

The type of resin is not particularly limited. Among these, when the composition for forming a passivation layer is applied on a semiconductor substrate, a resin capable of adjusting the viscosity within a range in which a good pattern can be formed is preferable. Specific examples of the resin include polyvinyl alcohol, polyacrylamide, polyacrylamide derivatives, polyvinyl amide, polyvinyl amide derivatives, polyvinyl pyrrolidone, polyethylene oxide, polyethylene oxide derivatives, polysulfonic acid, acrylamide alkyl sulfonic acid, cellulose, cellulose derivatives (carboxymethyl cellulose, Hydroxyethyl cellulose, cellulose ethers such as 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 Derivatives, dextrin, dextrin derivatives, (meth) ac Examples thereof include phosphoric acid resins, (meth) acrylic acid ester resins (alkyl (meth) acrylate resins, dimethylaminoethyl (meth) acrylate resins, etc.), butadiene resins, styrene resins, siloxane resins, and copolymers thereof. . These resins can be used alone or in combination of two or more.
In the present specification, “(meth) acrylic acid” means at least one of “acrylic acid” and “methacrylic acid”, and “(meth) acrylate” means at least one of “acrylate” and “methacrylate”. means.

  Among these resins, from the viewpoint of storage stability and pattern formation, it is preferable to use a neutral resin having no acidic or basic functional group, and even when the content is small, viscosity and From the viewpoint of adjusting thixotropy, it is more preferable to use a cellulose derivative such as ethyl cellulose.

  The molecular weight of the resin is not particularly limited, and is preferably adjusted 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 100 to 10,000,000, 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 calibration curve is approximated by a cubic equation using a standard polystyrene 5 sample set (PStQuick MP-H, PStQuick B [Tosoh Corporation, trade name]). The measurement conditions for GPC are shown below.

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

  When the composition for forming a passivation layer contains a resin, the content of the resin in the composition for forming a passivation layer can be appropriately selected as necessary. For example, the resin content is preferably 0.1% by mass to 30% by mass in the composition for forming a passivation layer. From the viewpoint of expressing thixotropy that facilitates pattern formation, the resin content is more preferably 1% by mass to 25% by mass, and further preferably 1.5% by mass to 20% by mass. Preferably, it is especially preferable that it is 1.5 mass%-10 mass%.

  When the composition for forming a passivation layer contains a resin, the content ratio of the specific metal compound and the resin can be appropriately selected as necessary. Among these, from the viewpoint of pattern formability and storage stability, the content ratio of the resin to the total amount of the specific metal compound (resin / specific metal compound) is preferably 0.001 to 1000, and preferably 0.01 to 100. More preferably, it is still more preferably 0.1-1.

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 basic compounds include inorganic bases such as alkali metal hydroxides and alkaline earth metal hydroxides, and trialkyls. Examples thereof include organic bases such as amine and pyridine.

  The composition for forming a passivation layer contains, as necessary, various additives such as a thickener, a wetting agent, a surfactant, inorganic particles, a resin containing silicon atoms, and a thixotropic agent. Also good.

  Examples of the inorganic particles include silica (silicon oxide), clay, silicon carbide, silicon nitride, montmorillonite, bentonite, and carbon black. Among these, it is preferable to use a filler containing silica as a component. Here, clay refers to a layered clay mineral, and specific examples include kaolinite, imogolite, montmorillonite, smectite, sericite, illite, talc, stevensite, and zeolite. When the composition for forming a passivation layer contains inorganic particles, the impartability of the composition for forming a passivation layer tends to be improved.

  Examples of the surfactant include nonionic surfactants, cationic surfactants, and anionic surfactants. Among these, nonionic surfactants or cationic surfactants are preferred because impurities such as heavy metals are not brought into the semiconductor device. Furthermore, examples of the nonionic surfactant include a silicon surfactant, a fluorine surfactant, and a hydrocarbon surfactant. When the composition for forming a passivation layer contains a surfactant, the thickness and composition uniformity of the composition layer formed from the composition for forming a passivation layer tend to be improved.

  Examples of the resin containing silicon atom include terminal lysine-modified silicone, alternating copolymer of polyamide and silicone, side chain alkyl-modified silicone, side chain polyether-modified silicone, terminal alkyl-modified silicone, silicone-modified pullulan, silicone-modified acrylic, etc. can do. The thickness and composition uniformity of the composition layer formed from the passivation layer forming composition tend to be improved.

  Examples of thixotropic agents include polyether compounds, fatty acid amides, fumed silica, hydrogenated castor oil, urea urethane amide, polyvinyl pyrrolidone, and oily gelling agents. When the composition for forming a passivation layer contains a thixotropic agent, fine line formability (when applying the composition for forming a passivation layer and when drying the composition layer, the expansion of the line width of the linear pattern is suppressed. Tend to improve). Examples of the polyether compound include polyethylene glycol, polypropylene glycol, poly (ethylene-propylene) glycol copolymer, and the like.

The viscosity of the composition for forming a passivation layer is not particularly limited, and can be appropriately selected according to a method for applying to the semiconductor substrate. For example, the viscosity of the composition for forming a passivation layer can be 0.01 Pa · s to 10000 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 1000 Pa · s. The viscosity is measured at 25 ° C. and a shear rate of 1.0 s ⁻¹ using a rotary shear viscometer.

Moreover, the shear viscosity of the composition for forming a passivation layer is not particularly limited. Among them from the viewpoints of pattern formability, thixotropic ratio calculated by dividing the shear viscosity eta ₁ at shear viscosity eta ₂ at a shear rate of ^{10s -1} at a shear rate of ^{_{1.0s -1 (η 1 / η 2}} ) is 1. It is preferable that it is 05-100, and it is more preferable that it is 1.1-50. The shear viscosity is measured at a temperature of 25 ° C. using a rotary shear viscometer equipped with a cone plate (diameter 50 mm, cone angle 1 °).

There is no restriction | limiting in particular in the manufacturing method of the composition for formation of a passivation layer. For example, a specific metal compound and a liquid medium or the like contained as necessary can be mixed and produced by a commonly used method. Moreover, you may manufacture by mixing the liquid medium and resin which dissolved resin, and a specific metal compound.
Further, the specific metal compound is obtained by mixing a specific metal alkoxide compound with m = 1 to 5 in formula (I) and a compound capable of forming a chelate with respect to a specific metal element contained in the specific metal alkoxide compound. It may be prepared. At that time, a liquid medium may be appropriately used or heat treatment may be performed. A composition for forming a passivation layer may be produced using the specific metal compound thus prepared.
In addition, the kind of component contained in the said composition for passivation layer formation and content of each component are thermal analysis, such as TG / DTA; Spectrum analysis, such as NMR and IR; Chromatographic analysis, such as HPLC and GPC; Can be used to confirm.

<Method for producing solar cell element>
The method for manufacturing a solar cell element of the present invention includes a step of forming a light receiving surface electrode on a light receiving surface of a semiconductor substrate, a step of forming a back electrode on the back surface opposite to the light receiving surface of the semiconductor substrate, From at least one of the light receiving surface, the back surface, and the side surface, Nb ₂ O ₅ , Ta ₂ O ₅ , V ₂ O ₅ , Y ₂ O ₃ , HfO ₂ and the compound represented by the general formula (I) Providing a composition for forming a passivation layer containing at least one compound selected from the group consisting of forming a composition layer; and heat-treating the composition layer to form a passivation layer; Have The method for manufacturing a solar cell element of the present invention may further include other steps as necessary. What was demonstrated by the solar cell element is applicable about the composition for formation of a passivation layer.

  According to the above method, a passivation layer having an excellent passivation effect can be formed on the semiconductor substrate. Further, the passivation layer can be formed with high productivity by a simple method that does not require a vapor deposition apparatus or the like. Therefore, according to the said method, the solar cell element excellent in conversion efficiency can be manufactured by a simple method.

  As a method for forming the light receiving surface electrode and the back surface electrode on the semiconductor substrate, a commonly used method can be employed. For example, it can be formed by applying an electrode forming paste 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.

  The step of forming the light receiving surface electrode and the step of forming the back surface electrode include a step of forming the composition layer by applying the composition for forming a passivation layer to at least one of the light receiving surface, the back surface, and the side surface of the semiconductor substrate. It may be before or after. Further, the heat treatment (firing) for forming the electrode and the heat treatment (firing) for forming the passivation layer from the composition layer may be performed collectively or separately as independent steps.

  Moreover, it is preferable to further have the process of providing alkaline aqueous solution to a semiconductor substrate before the process of forming a composition layer. That is, it is preferable to wash the surface of the semiconductor substrate with an alkaline aqueous solution before applying the passivation layer forming composition onto the semiconductor substrate. By washing with an alkaline aqueous solution, organic substances, particles, and the like present on the surface of the semiconductor substrate can be removed, and the passivation effect is further improved.

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

  There is no particular limitation on the method of forming the composition layer on the light-receiving surface, back surface, and side surface of the semiconductor substrate using the passivation layer forming composition. For example, a method for applying a composition for forming a passivation layer on a semiconductor substrate using a known application method or the like can be mentioned. Specific examples include a printing method such as an immersion method and a screen printing method, a spin coating method, a brush coating method, a spray method, a doctor blade method, a roll coating method, and an ink jet method. Among these, from the viewpoint of pattern formability, the screen printing method and the ink jet method are preferable, and the screen printing method is more preferable.

  The amount of the passivation layer forming composition applied to the semiconductor substrate can be appropriately selected depending on the purpose. For example, the thickness of the passivation layer to be formed can be appropriately adjusted so as to have a desired thickness described later.

A passivation layer is formed on a semiconductor substrate by heat-treating (baking) the composition layer formed by the composition for forming a passivation layer to form a heat-treated material layer (baked material layer) derived from the composition layer. be able to.
There are no particular restrictions on the heat treatment (firing) conditions of the composition layer. When the composition for forming a passivation layer contains a specific metal compound and other optional metal compounds (such as organoaluminum compounds), the specific metal oxide and other inorganic oxides that are heat-treated products (fired products) If it can be converted into (aluminum oxide (Al ₂ O ₃ ) or the like), the heat treatment (firing) conditions of the composition layer are not particularly limited.

  Among them, the heat treatment (firing) conditions that can form an amorphous specific metal oxide having no crystal structure are preferable. When the passivation layer is composed of an amorphous specific metal oxide, the passivation layer can effectively have a negative charge, and a more excellent passivation effect can be obtained. Specifically, the heat treatment (firing) temperature is preferably 400 ° C or higher, more preferably 400 ° C to 900 ° C, and still more preferably 600 ° C to 800 ° C. The heat treatment (firing) temperature here means the maximum temperature in the furnace used for the heat treatment (firing). The heat treatment (firing) time can be appropriately selected according to the heat treatment (firing) temperature and the like. For example, it can be 5 seconds to 10 hours, and is preferably 10 seconds to 5 hours. The heat treatment (firing) time here means the holding time at the maximum temperature.

  In addition, heat processing (baking) can be performed using a diffusion furnace (For example, ACCURON CQ-1200, Hitachi Kokusai Electric; 206A-M100, Koyo Thermo System Co., Ltd.), etc. The atmosphere in which the heat treatment (firing) is performed is not particularly limited, and can be performed in the air.

  Moreover, you may further have the process of drying a composition layer before the process of heat-processing (baking) a composition layer and forming a passivation layer. By having the process of drying the composition layer, a passivation layer having a more uniform passivation effect can be formed.

  The step of drying the composition layer is not particularly limited as long as at least a part of the liquid medium that may be contained in the passivation layer forming composition can be removed. The drying treatment can be, for example, a heat treatment at 30 ° C. to 250 ° C. for 10 seconds to 60 minutes, and is preferably a heat treatment at 40 ° C. to 220 ° C. for 30 seconds to 10 minutes. The drying treatment may be performed under normal pressure or under reduced pressure.

Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 illustrates, as a cross-sectional view, a process diagram schematically showing an example of a method for producing a solar cell element having a passivation layer according to the present embodiment. However, this process diagram does not limit the usage method of the present invention.

As shown in FIG. 1A, in a p-type semiconductor substrate 1, an n ⁺ -type diffusion layer 2 is formed in the vicinity of the surface, and an antireflection film 3 is formed on the surface. As the antireflection film 3, a silicon nitride film, a titanium oxide film, or the like is known. A surface protective film (not shown) such as silicon oxide may be present between the antireflection film 3 and the p-type semiconductor substrate 1. Further, the passivation layer according to the present invention may be used as a surface protective film. In that case, although not shown, an antireflection film may be further laminated on the passivation layer to form a two-layer structure. When the passivation layer according to the present invention is formed on the light receiving surface, high conversion efficiency is achieved even in a solar cell (not shown) having a general structure in which an aluminum electrode is formed on the entire back surface, instead of a point contact structure as described later. It can be realized.

Next, as shown in FIG. 1B, a material for forming the back electrode 5 such as an aluminum electrode paste is applied to a partial region of the back surface, and then heat-treated (fired) to form the back electrode 5, and p A p ⁺ type diffusion layer 4 is formed by diffusing aluminum atoms in the type semiconductor substrate 1.

Next, as shown in FIG. 1C, the electrode-forming paste is applied to the light-receiving surface side, and then heat-treated (fired) to form the light-receiving surface electrode 7. By using those containing glass particles having a fire-through property as an electrode forming paste, it reaches through the antireflective film 3, as shown in FIG. 1 (c), on the n ⁺ -type diffusion layer 2, the light-receiving surface The electrode 7 can be formed to obtain an ohmic contact.

  And as shown in FIG.1 (d), the composition for passivation layer formation is provided by screen printing etc. on the p-type layer of the back surface other than the area | region in which the back electrode 5 was formed, and a composition layer is formed. . The passivation layer 6 is formed by heat-treating (baking) the composition layer formed on the p-type layer. By forming the passivation layer 6 on the p-type layer on the back surface, a solar cell element having excellent power generation efficiency can be manufactured.

  In the solar cell element manufactured by the manufacturing method including the manufacturing process shown in FIG. 1, the back electrode made of aluminum or the like can have a point contact structure, and the warpage of the substrate can be reduced.

1D shows a method of forming a passivation layer only on the back surface portion, but in addition to the back surface of the p-type semiconductor substrate 1, a passivation layer forming composition is also applied to the side surface, and this is subjected to heat treatment ( The passivation layer 6 may be further formed on the side surface (edge) of the semiconductor substrate 1 by baking (not shown). Thereby, the solar cell element excellent in power generation efficiency can be manufactured.
Furthermore, the passivation layer 6 may be formed by forming the passivation layer forming composition of the present invention only on the side surface without forming the passivation layer on the back surface, and performing heat treatment (firing). When the composition for forming a passivation layer of the present invention is used in a place where there are many crystal defects such as side surfaces, the effect is particularly great.

  In FIG. 1, the embodiment in which the passivation layer is formed after forming the electrode has been described. However, after the passivation layer is formed, an electrode such as aluminum may be formed on the entire surface by vapor deposition or the like, and it is necessary to perform heat treatment (firing) at a high temperature. No electrode may be formed on the entire surface.

FIG. 2 illustrates, as a cross-sectional view, a process diagram schematically showing another example of a method for manufacturing a solar cell element having a passivation layer according to the present embodiment. Specifically, FIG. 2 shows the heat treatment of the aluminum electrode paste after forming the p ⁺ type diffusion layer using the aluminum electrode paste or the p type diffusion layer forming composition capable of forming the p ⁺ type diffusion layer by thermal diffusion treatment. The process drawing including the process of removing the heat-treated product of the product or the p ⁺ -type diffusion layer forming composition will be described as a cross-sectional view. Here, the p-type diffusion layer forming composition can be configured to include, for example, an acceptor element-containing material and a glass component.

As shown in FIG. 2A, an n ⁺ -type diffusion layer 2 is formed in the vicinity of the surface of the p-type semiconductor substrate 1, and an antireflection film 3 is formed on the surface. As the antireflection film 3, a silicon nitride film, a titanium oxide film, or the like is known.

Next, as shown in FIG. 2B, the p ⁺ -type diffusion layer 4 is formed by applying a p ⁺ -type diffusion layer forming composition to a partial region of the back surface and then performing heat treatment. On the p ⁺ type diffusion layer 4, a heat treatment product 8 of a composition for forming a p ⁺ type diffusion layer is formed.
Here, an aluminum electrode paste may be used instead of the p-type diffusion layer forming composition. When an aluminum electrode paste is used, an aluminum electrode 8 is formed on the p ⁺ type diffusion layer 4.

Next, as shown in FIG. 2C, the heat-treated product 8 or the aluminum electrode 8 of the p-type diffusion layer forming composition formed on the p ⁺ -type diffusion layer 4 is removed by a technique such as etching.

Next, as shown in FIG. 2 (d), the electrode forming paste is selectively applied to the light receiving surface (front surface) and a part of the back surface, and then heat-treated, and the light receiving surface electrode 7 is applied to the light receiving surface (front surface). The back electrode 5 is formed on the back surface. By using those containing glass particles having a fire-through property as an electrode forming paste to be applied to the light-receiving surface side, it reaches through the antireflective film 3, as shown in FIG. 2 (c), n ⁺ -type diffusion layer 2 A light receiving surface electrode 7 is formed on the surface to obtain an ohmic contact.

Since the p ⁺ -type diffusion layer 4 has already been formed in the region where the back electrode is formed, the electrode forming paste for forming the back electrode 5 is not limited to the aluminum electrode paste, but a lower electrode such as a silver electrode paste. An electrode paste capable of forming a resistive electrode can also be used. As a result, the power generation efficiency can be further increased.

And as shown in FIG.2 (e), the composition for passivation layer formation of this invention is provided on the p-type layer of the back surface other than the area | region in which the back electrode 5 was formed, and a composition layer is formed. The application can be performed by a method such as screen printing. The passivation layer 6 is formed by heat-treating (firing) the composition layer formed on the p ⁺ -type diffusion layer 4. By forming the passivation layer 6 on the p-type layer, a solar cell element excellent in power generation efficiency can be manufactured.

  Further, FIG. 2E shows a method of forming a passivation layer only on the back surface portion. However, in addition to the back surface side of the p-type semiconductor substrate 1, a passivation layer forming composition is applied to the side surface and heat treatment (firing). ) To further form a passivation layer on the side surface (edge) of the p-type semiconductor substrate 1 (not shown). Thereby, the solar cell element excellent in power generation efficiency can be manufactured.

  Furthermore, without forming a passivation layer on the back surface, the passivation layer forming composition of the present invention may be applied only to the side surface, and this may be heat-treated (fired) to form a passivation layer. When the composition for forming a passivation layer of the present invention is used in a place where there are many crystal defects such as side surfaces, the effect is particularly great.

  In FIG. 2, the embodiment in which the passivation layer is formed after forming the electrode has been described. However, after the passivation layer is formed, an electrode such as aluminum may be formed on the entire surface by vapor deposition or the like, or heat treatment (firing) is performed at a high temperature. An unnecessary electrode may be formed on the entire surface.

In the embodiment described above, the case where a p-type semiconductor substrate having an n ⁺ -type diffusion layer formed on the light-receiving surface has been described. However, an n-type semiconductor substrate having a p ⁺ -type diffusion layer formed on the light-receiving surface is described. Similarly, when used, a solar cell element can be produced. In this case, an n ⁺ type diffusion layer is formed on the back side.

<Solar cell module>
The solar cell module of this invention has the above-mentioned solar cell element and the wiring material arrange | positioned on the electrode of the said solar cell element. The solar cell module includes at least one of the solar cell elements, and is configured by arranging a wiring material such as a tab wire on the electrode of the solar cell element. If necessary, the solar cell may be constituted by connecting a plurality of solar cell elements via a wiring material and further sealing with a sealing material. The wiring material and the sealing material are not particularly limited, and can be appropriately selected from those usually used in the industry. There is no restriction | limiting in the magnitude | size of the said solar cell module. It is preferably 0.5m ² ~3m ^2.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

<Example 1>
(Preparation of a composition for forming a passivation layer)
Al ₂ O ₃ thin film coating material (High-Purity Chemical Laboratory, Ltd. “SYM-Al04”, Al ₂ O ₃ : 2 mass%, xylene: 87 mass%, 2-propanol: 5 mass%, stabilizer: 6 mass %) And 1.0 g of Nb ₂ O ₅ thin film coating material (High Purity Chemical Research Laboratory “Nb-05”, Nb ₂ O ₅ : 5% by mass, n-butyl acetate: 56% by mass, stabilizer : 16.5 mass%, viscosity modifier: 22.5 mass%) was mixed to prepare a composition 1 for forming a passivation layer.

(Formation of passivation layer)
As the semiconductor substrate, a single crystal p-type silicon substrate (SUMCO, 50 mm square, thickness: 625 μm) having a mirror-shaped surface was used. The silicon substrate was cleaned by immersing it at 70 ° C. for 5 minutes using an RCA cleaning solution (Kanto Chemical Co., Ltd., Frontier Cleaner-A01).
Thereafter, a spin coater (Mikasa Co., Ltd., “MS-100”) is applied to the entire surface of one surface of the silicon substrate pretreated with the passivation layer forming composition 1 obtained above at 30 rpm at 4000 rpm (min ⁻¹ ). It was given on condition of second. Then, it dried at 150 ° C. for 3 minutes. Subsequently, after heat-treating (baking) in the air at 700 ° C. for 10 minutes, it was allowed to cool at room temperature (25 ° C.) to produce an evaluation substrate. The heat treatment (firing) was performed using a horizontal diffusion furnace (206A-M100, Koyo Thermo System Co., Ltd.) under the conditions of a maximum temperature of 700 ° C. and a holding time of 10 minutes in an air atmosphere.

(Measurement of effective lifetime)
The effective lifetime (μs) of the region where the passivation layer of the evaluation substrate obtained above is formed is reflected at room temperature (25 ° C.) using a lifetime measurement device (Nippon Semi-Lab Co., Ltd., WT-2000PVN). It was measured by the microwave photoconductive decay method. The effective lifetime was 480 μs.

(Measurement of average thickness)
Using an interference type film thickness meter (Filmmetrics Corporation, F20 film thickness measurement system), the thickness of the passivation layer was measured at five points, and the average value was calculated. The average thickness was 82 nm.

(Density measurement)
The density was calculated from the mass and average thickness of the passivation layer. The density was 3.2 g / cm ³ .

(Production of solar cell element)
156 mm square p-type silicon substrate (Advantech Co., Ltd., n-type diffusion layer sheet resistance: 60 Ω / □, formed with an n-type diffusion layer on both sides using phosphorous oxychloride and an SiNx film on one side (light-receiving side) Double-sided texture-treated, SiNx film thickness: 80 nm), and passivation layer forming composition 1 on the back side by inkjet (Microjet Corporation, inkjet device “MJP-1500V”, head: IJH-80, (Nozzle size: 50 μm × 70 μm) The composition 1 for forming a passivation layer 1 was applied to a region 10 other than the opening 9 so that the pattern shown in FIG. Then, it dried at 150 ° C. for 3 minutes. Next, using a horizontal diffusion furnace (206A-M100, Koyo Thermo System Co., Ltd.), after heat treatment (firing) under atmospheric conditions at a maximum temperature of 700 ° C. and a holding time of 1 hour, to room temperature (25 ° C.) Allowed to cool.

  Thereafter, an aluminum electrode (PVG solutions, PVG-AD-02) was screen-printed on the back side with a solid pattern of 125 mm × 125 mm, and dried at 150 ° C. for 3 minutes. Next, a silver electrode (DuPont, PV159A) was screen-printed on the light receiving surface side using a printing mask having a pattern shown in FIG. Next, after drying at 150 ° C., a solar cell element was produced by heat treatment (firing) at 700 ° C. using a tunnel-type firing furnace (Noritake Co., Ltd.).

  One hour after producing the solar cell element, the power generation characteristics were evaluated using a solar cell element solar simulator (Wacom Denso Co., Ltd., XS-155S-10). Evaluation of the power generation performance is simulated sunlight (WXS-155S-10, Wacom Denso Co., Ltd.) and voltage-current (IV) evaluation measuring instrument (IV CURVE TRACER MP-180, manufactured by EKO INSTRUMENT) The measurement apparatus was combined. Jsc (short circuit current density), Voc (open circuit voltage), FF (form factor), and η (conversion efficiency) indicating power generation performance as a solar cell are JIS-C-8913 (fiscal 2005) and JIS-C-8914, respectively. It was obtained by measuring according to (2005). The results are shown in Table 2.

Moreover, the produced solar cell element was put in a constant temperature and humidity chamber at 50 ° C. and 80% RH, and power generation characteristics after storage for 1 month were evaluated. The results are shown in Table 3. The rate of change in conversion efficiency after storage of the solar cell element (conversion efficiency η ² [%] after storage relative to conversion efficiency η ¹ before storage) was 99.7%.

<Example 2>
(Preparation of a composition for forming a passivation layer)
Ta ₂ O ₅ thin film coating material (High Purity Chemical Laboratory, “Ta-10-P”, Ta ₂ O ₅ : 10% by mass, n-octane: 9% by mass, n-butyl acetate: 60% by mass, Stabilizer: 21% by mass) was used as composition 2 for forming a passivation layer.

A substrate for evaluation was produced in the same manner as in Example 1 except that the composition 2 for forming a passivation layer prepared above was used, and evaluated in the same manner as in Example 1. The effective lifetime was 450 μs. The thickness of the passivation layer was 75 nm, and the density was 3.6 g / cm ³ .

  A solar cell element was produced in the same manner as in Example 1 except that the passivation layer forming composition 2 was used instead of the passivation layer forming composition 1, and power generation characteristics were evaluated.

<Example 3>
HfO ₂ thin film coating material (High Purity Chemical Laboratory, “Hf-05”, HfO ₂ content: 5 mass%, isoamyl acetate: 73 mass%, n-octane: 10 mass%, isopropyl alcohol: 5 mass% , Stabilizer: 7% by mass) was used as composition 3 for forming a passivation layer.

An evaluation substrate was prepared in the same manner as in Example 1 except that the passivation layer forming composition 3 prepared above was used, and evaluated in the same manner as in Example 1. The effective lifetime was 380 μs. The thickness of the passivation layer was 71 nm and the density was 3.2 g / cm ³ .

  A solar cell element was produced in the same manner as in Example 1 except that the passivation layer forming composition 3 was used instead of the passivation layer forming composition 1, and power generation characteristics were evaluated.

<Example 4>
Y ₂ O ₃ thin film coating material (High-Purity Chemical Laboratory, “Y-03”, Y ₂ O ₃ : 3% by mass, 2-ethylhexanoic acid: 12.5% by mass, n-butyl acetate: 22. 5% by mass, ethyl acetate: 8% by mass, terpin oil: 45% by mass, viscosity modifier: 9% by mass) were used as the composition 4 for forming a passivation layer.

An evaluation substrate was prepared in the same manner as in Example 1 except that the passivation layer forming composition 4 prepared above was used, and evaluation was performed in the same manner as in Example 1. The effective lifetime was 390 μs. The thickness of the passivation layer was 68 nm and the density was 2.8 g / cm ³ .

  A solar cell element was produced in the same manner as in Example 1 except that the passivation layer forming composition 4 was used instead of the passivation layer forming composition 1, and power generation characteristics were evaluated.

<Example 5>
Ethyl acetoacetate aluminum diisopropylate (“ALCH” manufactured by Kawaken Fine Chemical Co., Ltd.), pentaethoxyniobium (Hokuko Chemical Co., Ltd.), acetylacetone (Wako Pure Chemical Industries, Ltd.), xylene (Wako Pure Chemical Industries, Ltd.), 2-Propanol (Wako Pure Chemical Industries, Ltd.) and terpineol (Nippon Terpene Chemical Co., Ltd.) were mixed at the orientation ratio shown in Table 1 and used as the passivation layer forming composition 5.

A passivation layer was formed on a pretreated silicon substrate and evaluated in the same manner as in Example 1 except that the composition 5 for forming a passivation layer prepared above was used. The effective lifetime was 420 μs. The thickness of the passivation layer was 94 nm and the density was 2.6 g / cm ³ .

  A solar cell element was produced in the same manner as in Example 1 except that the passivation layer forming composition 5 was used in place of the passivation layer forming composition 1, and power generation characteristics were evaluated.

<Comparative Example 1>
In Example 1, an evaluation substrate and a solar cell element were produced in the same manner as in Example 1, except that the passivation layer forming composition 1 was not applied. The effective lifetime of the evaluation substrate was measured and evaluated. The effective lifetime was 20 μs.

<Comparative example 2>
5.0 g of ethyl cellulose (Nihon Kasei Co., Ltd., ETHOCEL 200 cps) as a resin and 95.0 g of terpineol (Nippon Terpene Chemical Co., Ltd.) as a liquid medium were mixed and stirred at 150 ° C. for 1 hour to prepare an ethyl cellulose solution.
A colorless and transparent composition C2 was prepared by mixing 2.00 g of Al ₂ O ₃ particles (High Purity Chemical Laboratory Co., Ltd., average particle size 1 μm), 1.98 g of terpineol, and 3.98 g of ethyl cellulose solution.
A substrate for evaluation was produced in the same manner as in Example 1 except that the composition C2 prepared above was used, and evaluated in the same manner as in Example 1. The effective lifetime was 21 μs. The thickness of the passivation layer was 2.1 μm, and the density was 1.4 g / cm ³ . Here, since the thickness could not be measured with an interference type film thickness meter, the thickness was measured with a stylus type step meter (AmBios, XP-2). Specifically, a part of the substrate was scraped off with a spatula, and the level difference between the applied portion and the scraped portion was measured under the conditions of a speed of 0.1 mm / s and a needle load of 0.5 mg. The measurement was performed three times, and the average value was calculated as the thickness.
A solar cell element was produced in the same manner as in Example 1 except that the composition C2 was used instead of the composition 1 for forming a passivation layer, and power generation characteristics were evaluated.

<Comparative Example 3>
A colorless and transparent composition C3 was prepared by mixing 2.01 g of tetraethoxysilane, 1.99 g of terpineol, and 4.04 g of an ethylcellulose solution prepared in the same manner as in Comparative Example 2.
An evaluation substrate was prepared in the same manner as in Example 1 except that the composition C3 prepared above was used, and evaluated in the same manner as in Example 1. The effective lifetime was 23 μs. The thickness of the passivation layer was 85 nm and the density was 2.1 g / cm ³ .
A solar cell element was produced in the same manner as in Example 1 except that the composition C3 was used instead of the composition 1 for forming a passivation layer, and power generation characteristics were evaluated.

  From the above, it can be seen that the solar cell element of the present invention has a passivation layer having an excellent passivation effect, and thus exhibits high conversion efficiency and suppresses deterioration of solar cell characteristics over time. Furthermore, it turns out that the passivation layer of the solar cell element of this invention can be formed in a desired shape by a simple process.

<Reference Embodiment 1>
The following are the passivation film, the coating material, the solar cell element, and the silicon substrate with the passivation film according to Reference Embodiment 1.

<1> A passivation film used for a solar cell element including aluminum oxide and niobium oxide and having a silicon substrate.

<2> The passivation film according to <1>, wherein a mass ratio (niobium oxide / aluminum oxide) between the niobium oxide and the aluminum oxide is 30/70 to 90/10.

<3> The passivation film according to <1> or <2>, wherein a total content of the niobium oxide and the aluminum oxide is 90% by mass or more.

<4> The passivation film according to any one of <1> to <3>, further including an organic component.

<5> The passivation film according to any one of <1> to <4>, which is a heat-treated product of a coating material containing an aluminum oxide precursor and a niobium oxide precursor.

<6> A coating-type material that includes an aluminum oxide precursor and a niobium oxide precursor and is used to form a passivation film for a solar cell element having a silicon substrate.

<7> A p-type silicon substrate made of single crystal silicon or polycrystalline silicon and having a light receiving surface and a back surface opposite to the light receiving surface;
An n-type impurity diffusion layer formed on the light-receiving surface side of the silicon substrate;
A first electrode formed on the surface of the n-type impurity diffusion layer on the light-receiving surface side of the silicon substrate;
A passivation film comprising aluminum oxide and niobium oxide formed on the back surface of the silicon substrate and having a plurality of openings;
A second electrode forming an electrical connection with the surface on the back side of the silicon substrate through the plurality of openings;
A solar cell element comprising:

<8> A p-type silicon substrate made of single crystal silicon or polycrystalline silicon and having a light receiving surface and a back surface opposite to the light receiving surface;
An n-type impurity diffusion layer formed on the light-receiving surface side of the silicon substrate;
A first electrode formed on the surface of the n-type impurity diffusion layer on the light-receiving surface side of the silicon substrate;
A p-type impurity diffusion layer formed on a part or all of the back side of the silicon substrate and doped with impurities at a higher concentration than the silicon substrate;
A passivation film comprising aluminum oxide and niobium oxide formed on the back surface of the silicon substrate and having a plurality of openings;
A second electrode that forms an electrical connection with the surface of the p-type impurity diffusion layer on the back side of the silicon substrate through the plurality of openings;
A solar cell element comprising:

<9> An n-type silicon substrate made of single crystal silicon or polycrystalline silicon and having a light receiving surface and a back surface opposite to the light receiving surface;
A p-type impurity diffusion layer formed on the light-receiving surface side of the silicon substrate;
A second electrode formed on the back side of the silicon substrate;
A passivation film formed on the light-receiving surface side surface of the silicon substrate and including a plurality of openings and containing aluminum oxide and niobium oxide;
A first electrode formed on the surface of the p-type impurity diffusion layer on the light-receiving surface side of the silicon substrate and forming an electrical connection with the surface on the light-receiving surface side of the silicon substrate through the plurality of openings; ,
A solar cell element comprising:

<10> The solar cell element according to any one of <7> to <9>, wherein the mass ratio of niobium oxide to aluminum oxide (niobium oxide / aluminum oxide) in the passivation film is 30/70 to 90/10.

<11> The solar cell element according to any one of <7> to <10>, wherein a total content of the niobium oxide and the aluminum oxide in the passivation film is 90% by mass or more.

<12> a silicon substrate;
The passivation film according to any one of <1> to <5> provided on the entire surface or a part of the silicon substrate;
A silicon substrate with a passivation film.

  According to the reference embodiment described above, a passivation film having a long silicon carrier lifetime and a negative fixed charge can be realized at a low cost. In addition, a coating type material for realizing the formation of the passivation film can be provided. In addition, a highly efficient solar cell element using the passivation film can be realized at low cost. In addition, a silicon substrate with a passivation film having a long carrier lifetime and a negative fixed charge can be realized at low cost.

  The passivation film of the present embodiment is a passivation film used for a silicon solar cell element, and includes aluminum oxide and niobium oxide.

  In this embodiment mode, the fixed charge amount of the film can be controlled by changing the composition of the passivation film.

  Further, it is more preferable that the mass ratio of niobium oxide and aluminum oxide is 30/70 to 80/20 from the viewpoint that the negative fixed charge can be stabilized. Further, the mass ratio of niobium oxide and aluminum oxide is more preferably 35/65 to 70/30 from the viewpoint that the negative fixed charge can be further stabilized. In addition, it is preferable that the mass ratio of niobium oxide and aluminum oxide is 50/50 to 90/10 from the viewpoint that both improvement of carrier lifetime and negative fixed charge can be achieved.

  The mass ratio of niobium oxide to aluminum oxide in the passivation film is measured by energy dispersive X-ray spectroscopy (EDX), secondary ion mass spectrometry (SIMS), and high frequency inductively coupled plasma mass spectrometry (ICP-MS). be able to. Specific measurement conditions are as follows. Dissolving the passivation film in acid or alkaline aqueous solution, atomizing this solution and introducing it into Ar plasma, measuring the wavelength and intensity by spectroscopically analyzing the light emitted when the excited element returns to the ground state, Element qualification is performed from the obtained wavelength, and quantification is performed from the obtained intensity.

  The total content of niobium oxide and aluminum oxide in the passivation film is preferably 80% by mass or more, and more preferably 90% by mass or more from the viewpoint of maintaining good characteristics. As the components of niobium oxide and aluminum oxide in the passivation film increase, the effect of negative fixed charges increases.

  The total content of niobium oxide and aluminum oxide in the passivation film can be measured by combining thermogravimetric analysis, fluorescent X-ray analysis, ICP-MS, and X-ray absorption spectroscopy. Specific measurement conditions are as follows. The ratio of inorganic components can be calculated by thermogravimetric analysis, the ratio of niobium and aluminum can be calculated by fluorescent X-ray or ICP-MS analysis, and the ratio of oxide can be examined by X-ray absorption spectroscopy.

  Further, the passivation film may contain components other than niobium oxide and aluminum oxide as organic components from the viewpoint of improving the film quality and adjusting the elastic modulus. The presence of the organic component in the passivation film can be confirmed by elemental analysis and measurement of the FT-IR of the film.

  The content of the organic component in the passivation film is more preferably less than 10% by mass, further preferably 5% by mass or less, and particularly preferably 1% by mass or less in the passivation film.

  The passivation film may be obtained as a heat-treated product of a coating type material containing an aluminum oxide precursor and a niobium oxide precursor. Details of the coating type material will be described next.

  The coating material of the present embodiment includes an aluminum oxide precursor and a niobium oxide precursor, and is used for forming a passivation film for a solar cell element having a silicon substrate.

The aluminum oxide precursor can be used without particular limitation as long as it produces aluminum oxide. As the aluminum oxide precursor, it is preferable to use an organic aluminum oxide precursor from the viewpoint of uniformly dispersing aluminum oxide on the silicon substrate and chemically stable. Examples of the organic aluminum oxide precursor include aluminum triisopropoxide (structural formula: Al (OCH (CH ₃ ) ₂ ) ₃ , High Purity Chemical Research Laboratory SYM-AL04, and the like.

The niobium oxide precursor can be used without particular limitation as long as it produces niobium oxide. As the niobium oxide precursor, it is preferable to use an organic niobium oxide precursor from the viewpoint of uniformly dispersing niobium oxide on the silicon substrate and chemically stable. Examples of organic niobium oxide precursors include niobium (V) ethoxide (structural formula: Nb (OC ₂ H ₅ ) ₅ , molecular weight: 318.21), High Purity Chemical Laboratory Nb-05, etc. be able to.

  A passivation film is formed by forming a coating type material containing an organic niobium oxide precursor and an organic aluminum oxide precursor using a coating method or a printing method, and then removing organic components by a subsequent heat treatment (firing). Can be obtained. Therefore, as a result, a passivation film containing an organic component may be used.

<Structure explanation of solar cell element>
The structure of the solar cell element according to the present embodiment will be described with reference to FIGS. 6-9 is sectional drawing which shows the 1st-4th structural example of the solar cell element which used the passivation film for the back surface of this Embodiment.

  As the silicon substrate (crystalline silicon substrate, semiconductor substrate) 101 used in this embodiment mode, either single crystal silicon or polycrystalline silicon may be used. Further, as the silicon substrate 101, either p-type crystalline silicon or n-type crystalline silicon may be used. From the standpoint of exerting the effects of the present embodiment, p-type crystalline silicon is more suitable.

  6 to 9 below, an example in which p-type single crystal silicon is used as the silicon substrate 101 will be described. Note that single crystal silicon or polycrystalline silicon used for the silicon substrate 101 may be any material, but single crystal silicon or polycrystalline silicon having a resistivity of 0.5 Ω · cm to 10 Ω · cm is preferable.

  As shown in FIG. 6 (first configuration example), an n-type diffusion layer 102 doped with a group V element such as phosphorus on the light-receiving surface side (upper side, first surface in the figure) of a p-type silicon substrate 101. Is formed. A pn junction is formed between the silicon substrate 101 and the diffusion layer 102. On the surface of the diffusion layer 102, a light receiving surface antireflection film 103 such as a silicon nitride (SiN) film, and a first electrode 105 (light receiving surface side electrode, first surface electrode, upper surface electrode) using silver (Ag) or the like. , A light receiving surface electrode) is formed. The light receiving surface antireflection film 103 may also have a function as a light receiving surface passivation film. By using the SiN film, both functions of the light receiving surface antireflection film and the light receiving surface passivation film can be provided.

  Note that the solar cell element of the present embodiment may or may not have the light-receiving surface antireflection film 103. In addition, the light receiving surface of the solar cell element is preferably formed with a concavo-convex structure (texture structure) in order to reduce the reflectance on the surface, but the solar cell element of the present embodiment has a texture structure. It may or may not have.

  On the other hand, a BSF (Back Surface Field) layer 104, which is a layer doped with a group III element such as aluminum or boron, is formed on the back side (lower side, second side, back side in the figure) of the silicon substrate 101. . However, the solar cell element of this embodiment may or may not have the BSF layer 104.

  A second surface made of aluminum or the like is used on the back surface side of the silicon substrate 101 to make contact (electrical connection) with the BSF layer 104 (or the surface on the back surface side of the silicon substrate 101 when the BSF layer 104 is not provided). Electrodes 106 (back side electrode, second side electrode, back side electrode) are formed.

  Furthermore, in FIG. 6 (first configuration example), the contact region (the surface on the back surface side of the silicon substrate 101 when the BSF layer 104 is not provided) and the second electrode 106 are electrically connected. A passivation film (passivation layer) 107 containing aluminum oxide and niobium oxide is formed in a portion excluding the opening OA). The passivation film 107 of this embodiment can have a negative fixed charge. With this fixed charge, electrons which are minority carriers among the carriers generated in the silicon substrate 101 by light are bounced back to the surface side. For this reason, a short circuit current increases and it is anticipated that photoelectric conversion efficiency will improve.

  Next, a second configuration example shown in FIG. 7 will be described. In FIG. 6 (first configuration example), the second electrode 106 is formed on the entire surface of the contact region (opening OA) and the passivation film 107. In FIG. The second electrode 106 is formed only in the region (opening OA). The second electrode 106 may be formed only in part on the contact region (opening OA) and the passivation film 107. Even with the solar cell element having the configuration shown in FIG. 7, the same effect as that of FIG. 6 (first configuration example) can be obtained.

  Next, a third configuration example shown in FIG. 8 will be described. In the third configuration example shown in FIG. 8, the BSF layer 104 is formed only on a part of the back surface side including the contact region (opening OA portion) with the second electrode 106, and FIG. 6 (first configuration example). Thus, it is not formed on the entire back surface side. Even with the solar cell element having such a configuration (FIG. 8), the same effect as in FIG. 6 (first configuration example) can be obtained. Further, according to the solar cell element of the third configuration example of FIG. 8, impurities are doped at a higher concentration than the silicon substrate 101 by doping the BSF layer 104, that is, a group III element such as aluminum or boron. Since the area is small, it is possible to obtain higher photoelectric conversion efficiency than that in FIG. 6 (first configuration example).

  Next, a fourth configuration example shown in FIG. 9 will be described. In FIG. 8 (third configuration example), the second electrode 106 is formed on the entire surface of the contact region (opening OA) and the passivation film 107, but in FIG. 9 (fourth configuration example), the contact is formed. The second electrode 106 is formed only in the region (opening OA). The second electrode 106 may be formed only in part on the contact region (opening OA) and the passivation film 107. Even with the solar cell element having the configuration shown in FIG. 9, the same effect as that of FIG. 8 (third configuration example) can be obtained.

  In addition, when the second electrode 106 is applied by a printing method and baked at a high temperature to form the entire surface on the back surface side, a convex warpage tends to occur in the temperature lowering process. Such warpage may cause damage to the solar cell element, which may reduce the yield. Further, the problem of warpage increases as the silicon substrate becomes thinner. The cause of this warp is that stress is generated because the thermal expansion coefficient of the second electrode 106 made of metal (for example, aluminum) is larger than that of the silicon substrate, and the shrinkage in the temperature lowering process is correspondingly large.

  From the above, when the second electrode 106 is not formed on the entire back surface side as shown in FIG. 7 (second configuration example) and FIG. 9 (fourth configuration example), the electrode structure tends to be symmetrical vertically. This is preferable because stress due to the difference in thermal expansion coefficient is unlikely to occur. However, in that case, it is preferable to provide a separate reflective layer.

<Description of manufacturing method of solar cell element>
Next, an example of the manufacturing method of the solar cell element (FIGS. 6 to 9) of the present embodiment having the above-described configuration will be described. However, the present embodiment is not limited to the solar cell element manufactured by the method described below.

  First, a texture structure is formed on the surface of the silicon substrate 101 shown in FIG. The texture structure may be formed on both sides of the silicon substrate 101 or only on one side (light receiving side). In order to form a texture structure, first, the damaged layer of the silicon substrate 101 is removed by immersing the silicon substrate 101 in a heated potassium hydroxide or sodium hydroxide solution. Then, a texture structure is formed on both surfaces or one surface (light receiving surface side) of the silicon substrate 101 by dipping in a solution containing potassium hydroxide and isopropyl alcohol as main components. Note that, as described above, the solar cell element of the present embodiment may or may not have a texture structure, and thus this step may be omitted.

Subsequently, after the silicon substrate 101 is washed with a solution of hydrochloric acid, hydrofluoric acid, etc., a phosphorus diffusion layer (n ⁺ layer) is formed as the diffusion layer 102 by thermal diffusion of phosphorus oxychloride (POCl ₃ ) or the like on the silicon substrate 101. To do. The phosphorus diffusion layer can be formed, for example, by applying a coating-type doping material solution containing phosphorus to the silicon substrate 101 and performing heat treatment. After the heat treatment, the phosphorous glass layer formed on the surface is removed with an acid such as hydrofluoric acid, whereby a phosphorous diffusion layer (n ⁺ layer) is formed as the diffusion layer 102. The method for forming the phosphorus diffusion layer is not particularly limited. The phosphorus diffusion layer may be formed so that the depth from the surface of the silicon substrate 101 is in the range of 0.2 μm to 0.5 μm, and the sheet resistance is in the range of 40Ω / □ to 100Ω / □ (ohm / square). preferable.

Thereafter, a BSF layer 104 on the back surface side is formed by applying a coating-type doping material solution containing boron, aluminum or the like to the back surface side of the silicon substrate 101 and performing heat treatment. For the application, methods such as screen printing, inkjet, dispensing, spin coating and the like can be used. After the heat treatment, the BSF layer 104 is formed by removing a layer of boron glass, aluminum, or the like formed on the back surface with hydrofluoric acid, hydrochloric acid, or the like. The method for forming the BSF layer 104 is not particularly limited. Preferably, the BSF layer 104 is preferably formed such that the concentration range of boron, aluminum, or the like is 10 ¹⁸ cm ⁻³ to 10 ²² cm ^−3, and the BSF layer 104 is formed in a dot shape or a line shape It is preferable to do. Note that the solar cell element of the present embodiment may or may not have the BSF layer 104, and thus this step may be omitted.

Further, when the diffusion layer 102 on the light-receiving surface and the BSF layer 104 on the back surface are formed using a coating-type doping material solution, the above-described doping material solution is applied to both sides of the silicon substrate 101 to diffuse. The phosphorous diffusion layer (n ⁺ layer) and the BSF layer 104 as the layer 102 may be formed in a lump, and then phosphorous glass, boron glass, or the like formed on the surface may be removed all at once.

  Thereafter, a silicon nitride film as the light-receiving surface antireflection film 103 is formed on the diffusion layer 102. The method for forming the light receiving surface antireflection film 103 is not particularly limited. The light-receiving surface antireflection film 103 is preferably formed to have a thickness in the range of 50 to 100 nm and a refractive index in the range of 1.9 to 2.2. The light-receiving surface antireflection film 103 is not limited to a silicon nitride film, and may be a silicon oxide film, an aluminum oxide film, a titanium oxide film, or the like. The surface antireflection film 103 such as an silicon nitride film can be manufactured by a method such as plasma CVD or thermal CVD, and is preferably manufactured by plasma CVD that can be formed in a temperature range of 350 ° C. to 500 ° C.

  Next, a passivation film 107 is formed on the back side of the silicon substrate 101. The passivation film 107 contains aluminum oxide and niobium oxide. For example, an aluminum oxide precursor typified by an organometallic decomposition coating material from which aluminum oxide can be obtained by heat treatment (firing), and niobium oxide obtained by heat treatment (firing). It is formed by applying a material (passivation material) containing a niobium oxide precursor typified by a commercially available organometallic decomposition coating type material and heat-treating (firing).

  The formation of the passivation film 107 can be performed as follows, for example. The above coating material is spin-coated on one side of a 725 μm thick 8-inch (20.32 cm) p-type silicon substrate (8Ω-12Ωcm) from which a natural oxide film has been previously removed with hydrofluoric acid having a concentration of 0.049% by mass. Then, pre-baking is performed on a hot plate at 120 ° C. for 3 minutes. Thereafter, heat treatment is performed at 650 ° C. for 1 hour in a nitrogen atmosphere. In this case, a passivation film containing aluminum oxide and niobium oxide is obtained. The thickness of the passivation film 107 formed by the above method is usually about several tens of nanometers as measured by an ellipsometer.

  The coating material is applied to a predetermined pattern including the contact region (opening OA) by a method such as screen printing, offset printing, ink jet printing, or dispenser printing. In addition, after apply | coating the said coating type material, after pre-baking in the range of 80 to 180 degreeC and evaporating a solvent, in nitrogen atmosphere or in air, it is 600 to 1000 degreeC, and 30 minutes to 3 hours. It is preferable to perform a degree of heat treatment (annealing) to form a passivation film 107 (oxide film).

  Furthermore, the opening (contact hole) OA is preferably formed on the BSF layer 104 in a dot shape or a line shape.

  As the passivation film 107 used for the above solar cell element, the mass ratio of niobium oxide to aluminum oxide (niobium oxide / aluminum oxide) is preferably 30/70 to 90/10, and 30/70 to 80/20. More preferably, it is more preferably 35/65 to 70/30. Thereby, the negative fixed charge can be stabilized. In addition, it is preferable that the mass ratio of niobium oxide and aluminum oxide is 50/50 to 90/10 from the viewpoint that both improvement of carrier lifetime and negative fixed charge can be achieved.

  Further, in the passivation film 107, the total content of niobium oxide and aluminum oxide is preferably 80% by mass or more, and more preferably 90% by mass or more.

  Next, the first electrode 105 which is an electrode on the light receiving surface side is formed. The first electrode 105 is formed by forming a paste mainly composed of silver (Ag) on the light-receiving surface antireflection film 103 by screen printing and performing a heat treatment (fire through). The shape of the 1st electrode 105 may be arbitrary shapes, for example, may be a known shape which consists of a finger electrode and a bus-bar electrode.

  And the 2nd electrode 106 which is an electrode of the back side is formed. The second electrode 106 can be formed by applying a paste containing aluminum as a main component using screen printing or a dispenser and heat-treating it. The shape of the second electrode 106 is preferably the same shape as the shape of the BSF layer 104, a shape covering the entire back surface, a comb shape, a lattice shape, or the like. The paste for forming the first electrode 105 and the second electrode 106, which are the electrodes on the light receiving surface side, is first printed, and then heat-treated (fire-through), whereby the first electrode 105 and the second electrode 106 are formed. The two electrodes 106 may be formed together.

  Further, by using a paste containing aluminum (Al) as a main component for forming the second electrode 106, aluminum diffuses as a dopant, and the BSF layer 104 is formed in a contact portion between the second electrode 106 and the silicon substrate 101 in a self-alignment manner. Is formed. As described above, the BSF layer 104 may be separately formed by applying a coating-type doping material solution containing boron, aluminum, or the like to the back side of the silicon substrate 101 and heat-treating it. .

  In the above description, a structural example and a manufacturing method example in which p-type silicon is used for the silicon substrate 101 are shown, but an n-type silicon substrate can also be used as the silicon substrate 101. In this case, the diffusion layer 102 is formed by a layer doped with a group III element such as boron, and the BSF layer 104 is formed by doping a group V element such as phosphorus. However, it should be noted that in this case, a leakage current flows through a portion where the inversion layer formed at the interface due to the negative fixed charge and the metal on the back surface are in contact with each other, and the conversion efficiency may be difficult to increase.

  When an n-type silicon substrate is used, a passivation film 107 containing niobium oxide and aluminum oxide can be used on the light receiving surface side as shown in FIG. FIG. 10 is a cross-sectional view showing a configuration example of a solar cell element using the light-receiving surface passivation film of the present embodiment.

  In this case, the diffusion layer 102 on the light receiving surface side is p-type doped with boron, and collects holes of the generated carriers on the light receiving surface side and electrons on the back surface side. For this reason, it is preferable that the passivation film 107 having a negative fixed charge is on the light receiving surface side.

  On the passivation film containing niobium oxide and aluminum oxide, an antireflection film made of SiN or the like may be further formed by CVD or the like.

  Hereafter, it demonstrates in detail, referring the reference Example and reference comparative example of this Embodiment.

[Reference Example 1-1]
3.0 g of a commercially available organometallic decomposition coating type material [High Purity Chemical Laboratory, Ltd. SYM-AL04, concentration 2.3 mass%] from which aluminum oxide (Al ₂ O ₃ ) can be obtained by heat treatment (firing), and heat treatment A commercially available organometallic decomposition coating-type material [High Purity Chemical Laboratory Nb-05, concentration 5% by mass] from which niobium oxide (Nb ₂ O ₅ ) is obtained by (baking) is mixed with 3.0 g, A passivation material (a-1) which is a coating type material was prepared.

The passivation material (a-1) was spin-coated on one side of a 725 μm-thick 8-inch p-type silicon substrate (8 Ωcm to 12 Ωcm) from which a natural oxide film was previously removed with hydrofluoric acid having a concentration of 0.049% by mass. Pre-baking was performed on the plate at 120 ° C. for 3 minutes. Thereafter, a heat treatment (firing) was performed at 650 ° C. for 1 hour in a nitrogen atmosphere to obtain a passivation film containing nitric oxide and niobium oxide [niobium oxide / aluminum oxide = 68/32 (mass ratio)]. It was 43 nm when the film thickness was measured with the ellipsometer. When the FT-IR of the passivation film was measured, a peak due to a very few alkyl groups was observed in the vicinity of 1200 cm ⁻¹ .

Next, a plurality of aluminum electrodes having a diameter of 1 mm were formed by vapor deposition on the passivation film through a metal mask, and a capacitor having a MIS (Metal-Insulator-Semiconductor) structure was produced. . The voltage dependence (CV characteristics) of the capacitance of this capacitor was measured with a commercially available prober and LCR meter (HP, 4275A). As a result, it was found that the flat band voltage (Vfb) shifted from an ideal value of −0.81 V to +0.32 V. From this shift amount, it was found that the passivation film obtained from the passivation material (a-1) showed a negative fixed charge with a fixed charge density (Nf) of −7.4 × 10 ¹¹ cm ⁻² .

  In the same manner as described above, the passivation material (a-1) is applied to both sides of an 8-inch p-type silicon substrate, pre-baked, and subjected to heat treatment (baking) at 650 ° C. for 1 hour in a nitrogen atmosphere. A sample in which both surfaces of the substrate were covered with a passivation film was produced. The carrier lifetime of this sample was measured by a lifetime measuring device (Kobelco Research Institute, RTA-540). As a result, the carrier lifetime was 530 μs. For comparison, the same 8-inch p-type silicon substrate was measured by passivation using the iodine passivation method, and the carrier lifetime was 1100 μs.

  From the above, it was found that the passivation film obtained by heat-treating (sintering) the passivation material (a-1) exhibits a certain degree of passivation performance and a negative fixed charge.

[Reference Example 1-2]
As in Reference Example 1-1, a commercially available organometallic decomposition coating material from which aluminum oxide (Al ₂ O ₃ ) can be obtained by heat treatment (firing) [High Purity Chemical Laboratory, SYM-AL04, concentration 2. 3 mass%] and a commercially available organometallic decomposable coating material from which niobium oxide (Nb ₂ O ₅ ) is obtained by heat treatment (firing) [High Purity Chemical Laboratory, Nb-05, concentration 5 mass%] , And changing the ratio, the passivation materials (a-2) to (a-7) shown in Table 4 were prepared.

  Similarly to Reference Example 1-1, each of the passivation materials (a-2) to (a-7) was applied to one side of a p-type silicon substrate, and heat treatment (firing) was performed to produce a passivation film. The voltage dependence of the capacitance of the obtained passivation film was measured, and the fixed charge density was calculated therefrom.

  Further, in the same manner as in Reference Example 1-1, the carrier lifetime was measured using a sample obtained by applying a passivation material to both sides of a p-type silicon substrate and performing heat treatment (firing). The results obtained are summarized in Table 4.

  Although the results are different depending on the ratio (mass ratio) of niobium oxide / aluminum oxide after heat treatment (firing), the passivation materials (a-2) to (a-7) also have a carrier lifetime after heat treatment (firing). Since it showed a certain value, it was suggested that it functions as a passivation film. It was found that all of the passivation films obtained from the passivation materials (a-2) to (a-7) stably show negative fixed charges and can be suitably used as a passivation for a p-type silicon substrate. .

[Reference Example 1-3]
3.18 g (0.010 mol) of commercially available niobium (V) ethoxide (structural formula: Nb (OC ₂ H ₅ ) ₅ , molecular weight: 318.21) and commercially available aluminum triisopropoxide (structural formula: Al ( A passivation material (c-1) having a concentration of 5% by mass was prepared by dissolving 1.02 g (0.005 mol) of OCH (CH ₃ ) ₂ ) ₃ , molecular weight: 204.25) in 80 g of cyclohexane.

The passivation material (c-1) is spin-coated on one side of a 725 μm-thick 8-inch p-type silicon substrate (8 Ωcm to 12 Ωcm) from which a natural oxide film has been previously removed with hydrofluoric acid having a concentration of 0.049% by mass. Pre-baking was performed at 120 ° C. for 3 minutes on the plate. Thereafter, heat treatment (baking) was performed at 600 ° C. for 1 hour in a nitrogen atmosphere to obtain a passivation film containing aluminum oxide and niobium oxide. When the film thickness was measured with an ellipsometer, it was 50 nm. As a result of elemental analysis, it was found that Nb / Al / C = 81/14/5 (mass%). When the FT-IR of the passivation film was measured, a peak due to a very few alkyl groups was observed in the vicinity of 1200 cm ⁻¹ .

Next, a plurality of aluminum electrodes having a diameter of 1 mm were formed by vapor deposition on the passivation film through a metal mask, and a capacitor having a MIS (Metal-Insulator-Semiconductor) structure was produced. . The voltage dependence (CV characteristics) of the capacitance of this capacitor was measured with a commercially available prober and LCR meter (HP, 4275A). As a result, it was found that the flat band voltage (Vfb) was shifted from an ideal value of −0.81 V to +4.7 V. From this shift amount, it was found that the passivation film obtained from the passivation material (c-1) had a fixed charge density (Nf) of −3.2 × 10 ¹² cm ⁻² and a negative fixed charge.

  In the same manner as above, the passivation material (c-1) is applied to both sides of an 8-inch p-type silicon substrate, pre-baked, and subjected to heat treatment (baking) at 600 ° C. for 1 hour in a nitrogen atmosphere to obtain silicon. A sample in which both surfaces of the substrate were covered with a passivation film was produced. The carrier lifetime of this sample was measured by a lifetime measuring device (Kobelco Research Institute, RTA-540). As a result, the carrier lifetime was 330 μs. For comparison, the same 8-inch p-type silicon substrate was measured by passivation using the iodine passivation method, and the carrier lifetime was 1100 μs.

  From the above, it was found that the passivation film obtained by heat-treating (sintering) the passivation material (c-1) showed a certain degree of passivation performance and a negative fixed charge.

[Reference Example 1-4]
2.35 g (0.0075 mol) of commercially available niobium (V) ethoxide (structural formula: Nb (OC ₂ H ₅ ) ₅ , molecular weight: 318.21) and commercially available aluminum triisopropoxide (structural formula: Al ( 1.02 g (0.005 mol) of OCH (CH ₃ ) ₂ ) ₃ , molecular weight: 204.25) and 10 g of novolac resin were dissolved in 10 g of diethylene glycol monobutyl ether acetate and 10 g of cyclohexane to obtain a passivation material (c -2) was prepared.

The passivation material (c-2) is spin-coated on one side of a 725 μm-thick 8-inch p-type silicon substrate (8 Ωcm to 12 Ωcm) from which a natural oxide film has been removed in advance with a hydrofluoric acid having a concentration of 0.049% by mass. Pre-baking was performed at 120 ° C. for 3 minutes on the plate. Thereafter, heat treatment (baking) was performed at 600 ° C. for 1 hour in a nitrogen atmosphere to obtain a passivation film containing aluminum oxide and niobium oxide. When the film thickness was measured by an ellipsometer, it was 14 nm. As a result of elemental analysis, it was found that Nb / Al / C = 75/17/8 (mass%). When the FT-IR of the passivation film was measured, a peak due to a very few alkyl groups was observed in the vicinity of 1200 cm ⁻¹ .

Next, a plurality of 1 mm diameter aluminum electrodes are deposited on the passivation film through a metal mask to form a MIS (Metal-Insulator-Semiconductor) capacitor. did. The voltage dependence (CV characteristics) of the capacitance of this capacitor was measured with a commercially available prober and LCR meter (HP, 4275A). As a result, it was found that the flat band voltage (Vfb) shifted from an ideal value of −0.81 V to +0.10 V. From this shift amount, it was found that the passivation film obtained from the passivation material (c-2) showed a negative fixed charge with a fixed charge density (Nf) of −0.8 × 10 ¹¹ cm ⁻² .

  In the same manner as described above, the passivation material (c-2) is applied to both sides of an 8-inch p-type silicon substrate, pre-baked, and subjected to heat treatment (firing) at 600 ° C. for 1 hour in a nitrogen atmosphere to obtain silicon. A sample in which both surfaces of the substrate were covered with a passivation film was produced. The carrier lifetime of this sample was measured by a lifetime measuring device (Kobelco Research Institute Co., Ltd., RTA-540). As a result, the carrier lifetime was 200 μs. For comparison, the same 8-inch p-type silicon substrate was measured by passivation using the iodine passivation method, and the carrier lifetime was 1100 μs.

  From the above, it was found that the passivation film obtained from the passivation material (c-2) exhibited a certain degree of passivation performance and a negative fixed charge.

[Reference Example 1-5 and Reference Comparative Example 1-1]
As in Reference Example 1-1, a commercially available organometallic decomposition coating material from which aluminum oxide (Al ₂ O ₃ ) can be obtained by heat treatment (calcination) [SYM-AL04, Purity Chemical Laboratory Co., Ltd., concentration 2.3]. % By mass] and a commercially available organometallic decomposable coating type material [High Purity Chemical Laboratory Nb-05, concentration 5% by mass] from which niobium oxide (Nb ₂ O ₅ ) can be obtained by heat treatment (firing) The materials were changed and mixed to prepare passivation materials (b-1) to (b-7) shown in Table 5.

  As in Reference Example 1-1, each of the passivation materials (b-1) to (b-7) was applied to one side of a p-type silicon substrate, and heat treatment (firing) was performed to produce a passivation film. Using this, the voltage dependence of the capacitance was measured, and the fixed charge density was calculated therefrom.

  Furthermore, as in Reference Example 1-1, a carrier material was measured using a sample obtained by applying a passivation material (coating material) to both sides of a p-type silicon substrate and curing it. The results obtained are summarized in Table 5.

It was found that the passivation film obtained from the passivation materials (b-1) to (b-6) has a large carrier lifetime and has a function as a passivation. In addition, when the niobium oxide / aluminum oxide ratios were 10/90 and 20/80, the fixed charge density values varied greatly, and a negative fixed charge density could not be stably obtained. It was confirmed that a negative fixed charge density can be realized by using niobium oxide. When measured by the CV method using passivation materials with niobium oxide / aluminum oxide of 10/90 and 20/80, a negative fixed charge is stably generated because a passivation film showing a positive fixed charge is obtained in some cases. It turns out that it has not reached to show. Note that a passivation film exhibiting a fixed charge can be used as a passivation for an n-type silicon substrate.
On the other hand, a negative fixed charge density could not be obtained with the passivation material (b-7) containing 100% by mass of aluminum oxide.

[Reference Comparative Example 1-2]
Commercially available organometallic decomposable coating material that can obtain titanium oxide (TiO ₂ ) by heat treatment (firing) as the passivation material (d-1) [High-Purity Chemical Laboratory Co., Ltd. Ti-03-P, concentration 3 mass%] As a passivation material (d-2), a commercially available organometallic decomposition coating type material [High Purity Chemical Research Institute BT-06, concentration 6 mass%] from which barium titanate (BaTiO ₃ ) is obtained by heat treatment (firing) As a passivation material (d-3), a commercially available organometallic decomposition coating material [High-Purity Chemical Laboratory Co., Ltd., Hf-05, concentration 5 mass%] from which hafnium oxide (HfO ₂ ) is obtained by heat treatment (firing) is used. Got ready.

  As in Reference Example 1-1, each of the passivation materials (d-1) to (d-3) is applied to one side of a p-type silicon substrate, and then heat-treated (fired) to produce a passivation film. Using this, the voltage dependence of the capacitance was measured, and the fixed charge density was calculated therefrom.

  Further, as in Reference Example 1-1, a passivation material was applied to both sides of a p-type silicon substrate, and a carrier lifetime was measured using a sample obtained by heat treatment (firing). The results obtained are summarized in Table 6.

  It was found that the passivation film obtained from the passivation materials (d-1) to (d-3) has a small carrier lifetime and an insufficient function as a passivation. It also showed a positive fixed charge. The passivation film obtained from the passivation material (d-3) had a negative fixed charge, but its value was small. It was also found that the carrier lifetime was relatively small and the function as a passivation was insufficient.

[Reference Example 1-6]
Using a single crystal silicon substrate doped with boron as the silicon substrate 101, a solar cell element having the structure shown in FIG. 8 was manufactured. After the surface of the silicon substrate 101 was textured, a coating type phosphorous diffusion material was applied to the light receiving surface side, and a diffusion layer 102 (phosphorus diffusion layer) was formed by heat treatment. Thereafter, the coating type phosphorus diffusing material was removed with dilute hydrofluoric acid.

Next, an SiN film produced by plasma CVD was formed as the light-receiving surface antireflection film 103 on the light-receiving surface side. Thereafter, the passivation material (a-1) prepared in Reference Example 1-1 was applied to the region excluding the contact region (opening OA) on the back surface side of the silicon substrate 101 by an inkjet method. Thereafter, heat treatment was performed to form a passivation film 107 having an opening OA.
In addition, a sample using the passivation material (c-1) prepared in Reference Example 1-3 was separately prepared as the passivation film 107.

  Next, on the light-receiving surface antireflection film 103 (SiN film) formed on the light-receiving surface side of the silicon substrate 101, a paste mainly composed of silver was screen-printed in the shape of predetermined finger electrodes and bus bar electrodes. On the back side, a paste mainly composed of aluminum was screen-printed on the entire surface. Thereafter, heat treatment (fire-through) is performed at 850 ° C. to form electrodes (first electrode 105 and second electrode 106), and aluminum is diffused into the opening OA on the back surface to form the BSF layer 104. Thus, a solar cell element having the structure shown in FIG. 8 was formed.

  In this case, regarding the silver electrode on the light receiving surface, the fire-through process in which the SiN film is not perforated is described, but the opening OA is first formed in the SiN film by etching or the like, and then the silver electrode is formed. You can also.

For comparison, the passivation film 107 is not formed in the above manufacturing process, aluminum paste is printed on the entire back surface, and the p ⁺ layer 114 corresponding to the BSF layer 104 and the electrode 116 corresponding to the second electrode. Was formed on the entire surface to form a solar cell element having the structure shown in FIG. About these solar cell elements, characteristic evaluation (a short circuit current, an open circuit voltage, a fill factor, and conversion efficiency) was performed. Characteristic evaluation was measured based on JIS-C-8913 (2005) and JIS-C-8914 (2005). The results are shown in Table 7.

  According to Table 7, the solar cell element having the passivation film 107 including the niobium oxide and aluminum oxide layers has both increased short-circuit current and open-circuit voltage as compared with the solar cell element not having the passivation film 107, and the conversion efficiency ( It was found that the photoelectric conversion efficiency was improved by 1% at the maximum.

<Reference Embodiment 2>
The following are the passivation film, coating material, solar cell element, and silicon substrate with passivation film according to Reference Embodiment 2.

  <1> A passivation film for use in a solar cell element having a silicon substrate, comprising aluminum oxide and at least one oxide of vanadium group element selected from the group consisting of vanadium oxide and tantalum oxide.

  <2> The passivation film according to <1>, wherein a mass ratio of the vanadium group element oxide to the aluminum oxide (vanadium group element oxide / aluminum oxide) is 30/70 to 90/10.

  <3> The passivation film according to <1> or <2>, in which a total content of the oxide of the vanadium group element and the aluminum oxide is 90% or more.

  <4> The oxide of the vanadium group element includes any of oxides of two or three vanadium group elements selected from the group consisting of vanadium oxide, niobium oxide, and tantalum oxide. Any of <1> to <3> The passivation film according to claim 1.

  <5> Heat treatment of a coating-type material comprising: a precursor of aluminum oxide; and a precursor of an oxide of at least one vanadium group element selected from the group consisting of a precursor of vanadium oxide and a precursor of tantalum oxide. The passivation film according to any one of <1> to <4>, which is a product.

  <6> an aluminum oxide precursor, and at least one vanadium group element oxide precursor selected from the group consisting of a vanadium oxide precursor and a tantalum oxide precursor, and having a silicon substrate A coating type material used for forming a passivation film of a solar cell element.

<7> a p-type silicon substrate;
An n-type impurity diffusion layer formed on the first surface side which is the light-receiving surface side of the silicon substrate;
A first electrode formed on the impurity diffusion layer;
A passivation film formed on the second surface side opposite to the light receiving surface side of the silicon substrate and having an opening;
A second electrode formed on the second surface side of the silicon substrate and electrically connected to the second surface side of the silicon substrate through the opening of the passivation film;
The said passivation film is a solar cell element containing aluminum oxide and the oxide of the at least 1 sort (s) of vanadium group element selected from the group which consists of vanadium oxide and a tantalum oxide.

<8> A p-type impurity diffusion layer formed on part or all of the second surface side of the silicon substrate and doped with an impurity at a higher concentration than the silicon substrate,
The solar cell element according to <7>, wherein the second electrode is electrically connected to the p-type impurity diffusion layer through an opening of the passivation film.

<9> an n-type silicon substrate;
A p-type impurity diffusion layer formed on the first surface which is the light-receiving surface side of the silicon substrate;
A first electrode formed on the impurity diffusion layer;
A passivation film formed on the second surface side opposite to the light receiving surface side of the silicon substrate and having an opening;
A second electrode formed on the second surface side of the silicon substrate and electrically connected to the second surface side of the silicon substrate through the opening of the passivation film;
The said passivation film is a solar cell element containing aluminum oxide and the oxide of the at least 1 sort (s) of vanadium group element selected from the group which consists of vanadium oxide and a tantalum oxide.

<10> An n-type impurity diffusion layer formed on a part or all of the second surface side of the silicon substrate and doped with impurities at a higher concentration than the silicon substrate,
The solar cell element according to <9>, wherein the second electrode is electrically connected to the n-type impurity diffusion layer through an opening of the passivation film.

  <11> The solar cell element according to any one of <7> to <10>, wherein a mass ratio of the oxide of the vanadium group element and the aluminum oxide in the passivation film is 30/70 to 90/10. .

  <12> The solar cell element according to any one of <7> to <11>, wherein a total content of the oxide of the vanadium group element and the aluminum oxide in the passivation film is 90% or more.

  <13> The oxide of the vanadium group element includes oxides of two or three vanadium group elements selected from the group consisting of vanadium oxide, niobium oxide, and tantalum oxide, <7> to <12> The solar cell element according to any one of the above.

<14> a silicon substrate;
The passivation film for solar cell elements according to any one of <1> to <5>, provided on the entire surface or a part of the silicon substrate,
A silicon substrate with a passivation film.

  According to the reference embodiment described above, a passivation film having a long silicon carrier lifetime and a negative fixed charge can be realized at a low cost. In addition, a coating type material for realizing the formation of the passivation film can be provided. In addition, a low-cost and highly efficient solar cell element using the passivation film can be realized. In addition, a silicon substrate with a passivation film having a long carrier lifetime and a negative fixed charge can be realized at low cost.

  The passivation film of the present embodiment is a passivation film used for a silicon solar cell element, and includes aluminum oxide and an oxide of at least one vanadium group element selected from the group consisting of vanadium oxide and tantalum oxide. It is what was included.

  In this embodiment mode, the amount of fixed charges included in the passivation film can be controlled by changing the composition of the passivation film. Here, the vanadium group element is a Group 5 element in the periodic table, and is an element selected from vanadium, niobium, and tantalum.

  The mass ratio of the vanadium group element oxide to aluminum oxide is more preferably 35/65 to 90/10, from the viewpoint that the negative fixed charge can be stabilized, and is 50/50 to 90/10. More preferably.

  The mass ratio of vanadium group element oxide and aluminum oxide in the passivation film is determined by energy dispersive X-ray spectroscopy (EDX), secondary ion mass spectrometry (SIMS), and high frequency inductively coupled plasma mass spectrometry (ICP-MS). ) Can be measured. Specific measurement conditions are as follows in the case of ICP-MS, for example. Dissolving the passivation film in acid or alkaline aqueous solution, atomizing this solution and introducing it into Ar plasma, measuring the wavelength and intensity by spectroscopically analyzing the light emitted when the excited element returns to the ground state, Element qualification is performed from the obtained wavelength, and quantification is performed from the obtained intensity.

  The total content of vanadium group oxide and aluminum oxide in the passivation film is preferably 80% by mass or more, and more preferably 90% by mass or more from the viewpoint of maintaining good characteristics. When the components other than the oxide of vanadium group elements and aluminum oxide in the passivation film increase, the effect of negative fixed charges increases.

  Further, in the passivation film, components other than the oxide of vanadium group element and aluminum oxide may be contained as an organic component from the viewpoint of improving the film quality and adjusting the elastic modulus. The presence of the organic component in the passivation film can be confirmed by elemental analysis and measurement of the FT-IR of the film.

As the oxide of the vanadium group element, it is preferable to select vanadium oxide (V ₂ O ₅ ) from the viewpoint of obtaining a larger negative fixed charge.

  The passivation film may include an oxide of a vanadium group element selected from the group consisting of vanadium oxide, niobium oxide, and tantalum oxide as an oxide of a vanadium group element.

  The passivation film is preferably obtained by heat-treating a coating-type material, and can be obtained by forming a coating-type material using a coating method or a printing method, and then removing organic components by heat treatment. More preferred. That is, the passivation film may be obtained as a heat-treated product of a coating type material containing an aluminum oxide precursor and a vanadium group element oxide precursor. Details of the coating type material will be described later.

The coating type material of the present embodiment is a coating type material used for a passivation film for a solar cell element having a silicon substrate, and includes a precursor of aluminum oxide, a precursor of vanadium oxide, and a precursor of tantalum oxide. And a precursor of an oxide of at least one vanadium group element selected from the group. As a precursor of the oxide of the vanadium group element contained in the coating material, a precursor of vanadium oxide (V ₂ O ₅ ) is selected from the viewpoint of the negative fixed charge of the passivation film formed from the coating material. It is preferable. The coating type material is composed of two or three vanadium group elements selected from the group consisting of vanadium oxide precursors, niobium oxide precursors and tantalum oxide precursors as vanadium group oxide precursors. An oxide precursor may also be included.

The aluminum oxide precursor can be used without particular limitation as long as it produces aluminum oxide. As the aluminum oxide precursor, it is preferable to use an organic aluminum oxide precursor from the viewpoint of uniformly dispersing aluminum oxide on the silicon substrate and a chemically stable viewpoint. Examples of the organic aluminum oxide precursor include aluminum triisopropoxide (structural formula: Al (OCH (CH ₃ ) ₂ ) ₃ , Kojundo Chemical Laboratory, SYM-AL04.

  The precursor of the oxide of the vanadium group element can be used without particular limitation as long as it generates an oxide of the vanadium group element. The vanadium group element oxide precursor is preferably an organic vanadium group oxide oxide precursor from the viewpoint of uniformly dispersing aluminum oxide on the silicon substrate and chemically stable. .

Examples of organic vanadium oxide precursors include vanadium (V) oxytriethoxide (structural formula: VO (OC ₂ H ₅ ) ₃ , molecular weight: 202.13), High Purity Chemical Laboratory, V-02 can be mentioned. Examples of organic tantalum oxide precursors include tantalum (V) methoxide (structural formula: Ta (OCH ₃ ) ₅ , molecular weight: 336.12), Kojundo Chemical Laboratory, Ta-10-P Can be mentioned. Examples of organic niobium oxide precursors include niobium (V) ethoxide (structural formula: Nb (OC ₂ H ₅ ) ₅ , molecular weight: 318.21), High Purity Chemical Laboratory, Nb-05. Can be mentioned.

  By forming a coating type material containing an organic vanadium group oxide precursor and an organic aluminum oxide precursor using a coating method or a printing method, and then removing the organic components by a heat treatment, A passivation film can be obtained. Therefore, as a result, a passivation film containing an organic component may be used. The content of the organic component in the passivation film is more preferably less than 10% by mass, still more preferably 5% by mass or less, and particularly preferably 1% by mass or less.

  The solar cell element (photoelectric conversion device) of the present embodiment includes the passivation film (insulating film, protective insulating film) described in the above embodiment in the vicinity of the photoelectric conversion interface of the silicon substrate, that is, aluminum oxide and vanadium oxide. And at least one oxide of a vanadium group element selected from the group consisting of tantalum oxide. By containing aluminum oxide and an oxide of at least one vanadium group element selected from the group consisting of vanadium oxide and tantalum oxide, the carrier lifetime of the silicon substrate can be extended and negative fixed charges can be obtained. And the characteristics (photoelectric conversion efficiency) of the solar cell element can be improved.

  For the description of the structure and manufacturing method of the solar cell element according to the present embodiment, reference can be made to the description of the structure and manufacturing method of the solar cell element according to Reference Embodiment 1.

  Hereafter, it demonstrates in detail, referring the reference Example and reference comparative example of this Embodiment.

<When vanadium oxide is used as the oxide of vanadium group element>
[Reference Example 2-1]
3.0 g of a commercially available organometallic thin film coating type material [High purity chemical research laboratory, SYM-AL04, concentration 2.3 mass%] from which aluminum oxide (Al ₂ O ₃ ) can be obtained by heat treatment (firing) And 6.0 g of a commercially available organometallic thin film coating material [Vitamin Purity Laboratory, V-02, concentration 2 mass%] from which vanadium oxide (V ₂ O ₅ ) can be obtained by heat treatment (firing). By mixing, a passivation material (a2-1) which is a coating type material was prepared.

Passivation of passivation material (a2-1) to one side of a 725 μm thick 8-inch p-type silicon substrate (8 Ω · cm to 12 Ω · cm) with natural oxide film removed beforehand with hydrofluoric acid at a concentration of 0.49% by mass It was applied and placed on a hot plate and prebaked at 120 ° C. for 3 minutes. Thereafter, a heat treatment (firing) was performed at 700 ° C. for 30 minutes in a nitrogen atmosphere to obtain a passivation film containing vanadium oxide and vanadium oxide [vanadium oxide / aluminum oxide = 63/37 (mass%)]. It was 51 nm when the film thickness was measured with the ellipsometer. When the FT-IR of the passivation film was measured, a peak due to a very few alkyl groups was observed in the vicinity of 1200 cm ⁻¹ .

Next, a plurality of aluminum electrodes having a diameter of 1 mm were formed on the above-described passivation film by vapor deposition through a metal mask, thereby manufacturing a capacitor having a metal-insulator-semiconductor (MIS) structure. . The voltage dependence (CV characteristics) of the capacitance of this capacitor was measured with a commercially available prober and LCR meter (HP, 4275A). As a result, it was found that the flat band voltage (Vfb) shifted from an ideal value of −0.81 V to +0.02 V. From this shift amount, it was found that the passivation film obtained from the passivation material (a2-1) showed a negative fixed charge with a fixed charge density (Nf) of −5.2 × 10 ¹¹ cm ⁻² .

  In the same manner as described above, the passivation material (a2-1) was applied to both sides of an 8-inch p-type silicon substrate, pre-baked, and subjected to heat treatment (baking) at 650 ° C. for 1 hour in a nitrogen atmosphere. A sample in which both surfaces of the substrate were covered with a passivation film was produced. The carrier lifetime of this sample was measured with a lifetime measuring device (Kobelco Research Institute, RTA-540). As a result, the carrier lifetime was 400 μs. For comparison, the same 8-inch p-type silicon substrate was measured by passivation using the iodine passivation method, and the carrier lifetime was 1100 μs. Further, when the carrier lifetime was measured again 14 days after the preparation of the sample, the carrier lifetime was 380 μs. Thereby, it was found that the decrease in carrier lifetime (from 400 μs to 380 μs) was within −10%, and the decrease in carrier lifetime was small.

  From the above, it was found that the passivation film obtained by heat-treating (sintering) the passivation material (a2-1) exhibits a certain degree of passivation performance and a negative fixed charge.

[Reference Example 2-2]
Similar to Reference Example 2-1, a commercially available organometallic thin film coated material from which aluminum oxide (Al ₂ O ₃ ) can be obtained by heat treatment (firing) [High Purity Chemical Laboratory, SYM-AL04, concentration 2 .3 mass%] and a commercially available organic metal thin film coating type material [Vitamin Purity Laboratory, V-02, concentration 2 mass%] from which vanadium oxide (V ₂ O ₅ ) is obtained by heat treatment, Passivation materials (a2-2) to (a2-7) shown in Table 8 were prepared by changing the ratio.

  As in Reference Example 2-1, each of the passivation materials (a2-2) to (a2-7) was applied to one side of a p-type silicon substrate, and heat treatment (firing) was performed to produce a passivation film. The voltage dependence of the capacitance of the obtained passivation film was measured, and the fixed charge density was calculated therefrom.

  Further, in the same manner as in Reference Example 2-1, the carrier lifetime was measured using a sample obtained by applying a passivation material to both surfaces of a p-type silicon substrate and performing heat treatment (firing).

  The results obtained are summarized in Table 8. Further, when the carrier lifetime was measured again 14 days after the preparation of the sample, the decrease in the carrier lifetime was found in any of the passivation films using the passivation materials (a2-2) to (a2-7) shown in Table 8. It was within -10%, and it was found that the decrease in carrier lifetime was small.

  Although the results are different depending on the ratio (mass ratio) of vanadium oxide / aluminum oxide after heat treatment (firing), the passivation materials (a2-2) to (a2-7) are all negative after heat treatment (firing). Since it showed a fixed charge and a certain carrier lifetime, it was suggested that it functions as a passivation film. It was found that all the passivation films obtained from the passivation materials (a2-2) to (a2-7) stably show negative fixed charges, and can be suitably used as a passivation for a p-type silicon substrate. .

[Reference Example 2-3]
As a compound for obtaining vanadium oxide (V ₂ O ₅ ) by heat treatment (firing), commercially available vanadium (V) oxytriethoxide (structural formula: VO (OC ₂ H ₅ ) ₃ , molecular weight: 202.13) is 1 0.02 g (0.010 mol) and a compound obtained from aluminum oxide (Al ₂ O ₃ ) by heat treatment (calcination), commercially available aluminum triisopropoxide (structure: Al (OCH (CH ₃ ) ₂ ) ₃ , A passivation material (b2-1) having a concentration of 5% by mass was prepared by dissolving 2.04 g (0.010 mol) of molecular weight: 204.25) in 60 g of cyclohexane.

Passivation of passivation material (b2-1) on one side of a 725 μm thick 8-inch p-type silicon substrate (8Ω · cm to 12Ω · cm) from which a natural oxide film was previously removed with hydrofluoric acid having a concentration of 0.49% by mass This was applied and prebaked at 120 ° C. for 3 minutes on a hot plate. Thereafter, a heat treatment (firing) was performed at 650 ° C. for 1 hour in a nitrogen atmosphere to obtain a passivation film containing aluminum oxide and vanadium oxide. When the film thickness was measured with an ellipsometer, it was 60 nm. As a result of elemental analysis, it was found that V / Al / C = 64/33/3 (mass%). When the FT-IR of the passivation film was measured, a peak due to a very few alkyl groups was observed in the vicinity of 1200 cm ⁻¹ .

Next, a plurality of aluminum electrodes having a diameter of 1 mm were formed on the above-described passivation film by vapor deposition through a metal mask, thereby manufacturing a capacitor having a metal-insulator-semiconductor (MIS) structure. . The voltage dependence (CV characteristics) of the capacitance of this capacitor was measured with a commercially available prober and LCR meter (HP, 4275A). As a result, it was found that the flat band voltage (Vfb) shifted from an ideal value of −0.81 V to +0.10 V. From this shift amount, it was found that the passivation film obtained from the passivation material (b2-1) showed a negative fixed charge with a fixed charge density (Nf) of −6.2 × 10 ¹¹ cm ⁻² .

  In the same manner as described above, the passivation material (b2-1) was applied to both sides of an 8-inch p-type silicon substrate, pre-baked, and subjected to heat treatment (baking) at 600 ° C. for 1 hour in a nitrogen atmosphere. A sample in which both surfaces of the substrate were covered with a passivation film was produced. The carrier lifetime of this sample was measured by a lifetime measuring device (Kobelco Research Institute, RTA-540). As a result, the carrier lifetime was 400 μs. For comparison, the same 8-inch p-type silicon substrate was measured by passivation using the iodine passivation method, and the carrier lifetime was 1100 μs.

  From the above, it was found that the passivation film obtained by heat-treating (sintering) the passivation material (b2-1) exhibited a certain degree of passivation performance and a negative fixed charge.

[Reference Example 2-4]
1.52 g (0.0075 mol) of commercially available vanadium (V) oxytriethoxide (structural formula: VO (OC ₂ H ₅ ) ₃ , molecular weight: 202.13) and commercially available aluminum triisopropoxide (structural formula : Al (OCH (CH ₃ ) ₂ ) ₃ , molecular weight: 204.25), 1.02 g (0.005 mol) and 10 g of novolak resin were dissolved in 10 g of diethylene glycol monobutyl ether acetate and 10 g of cyclohexane to passivate. Material (b2-2) was prepared.

Passivation of passivation material (b2-2) on one side of a 725 μm thick 8-inch p-type silicon substrate (8 Ω · cm to 12 Ω · cm) with natural oxide film removed beforehand with hydrofluoric acid at a concentration of 0.49% by mass It was applied and placed on a hot plate and prebaked at 120 ° C. for 3 minutes. Thereafter, heating was performed at 650 ° C. for 1 hour in a nitrogen atmosphere to obtain a passivation film containing aluminum oxide and vanadium oxide. When the film thickness was measured with an ellipsometer, it was 22 nm. As a result of elemental analysis, it was found that V / Al / C = 71/22/7 (mass%). When the FT-IR of the passivation film was measured, a peak due to a very few alkyl groups was observed in the vicinity of 1200 cm ⁻¹ .

Next, a plurality of aluminum electrodes having a diameter of 1 mm were formed on the above-described passivation film by vapor deposition through a metal mask, thereby manufacturing a capacitor having a metal-insulator-semiconductor (MIS) structure. . The voltage dependence (CV characteristics) of the capacitance of this capacitor was measured with a commercially available prober and LCR meter (HP, 4275A). As a result, it was found that the flat band voltage (Vfb) shifted from the ideal value of −0.81 V to +0.03 V. From this shift amount, it was found that the passivation film obtained from the passivation material (b2-2) had a fixed charge density (Nf) of −2.0 × 10 ¹¹ cm ⁻² and a negative fixed charge.

  In the same manner as described above, the passivation material (b2-2) is applied to both sides of an 8-inch p-type silicon substrate, pre-baked, and subjected to heat treatment (baking) at 600 ° C. for 1 hour in a nitrogen atmosphere to obtain silicon. A sample in which both surfaces of the substrate were covered with a passivation film was produced. The carrier lifetime of this sample was measured by a lifetime measuring device (Kobelco Research Institute, RTA-540). As a result, the carrier lifetime was 170 μs. For comparison, the same 8-inch p-type silicon substrate was measured by passivation using the iodine passivation method, and the carrier lifetime was 1100 μs.

  From the above, it was found that the passivation film obtained by curing the passivation material (b2-2) exhibited a certain degree of passivation performance and a negative fixed charge.

<When tantalum oxide is used as the oxide of vanadium group element>
[Reference Example 2-5]
Commercially available organometallic thin film coating type material [High Purity Chemical Laboratory, SYM-AL04, concentration 2.3 mass%] from which aluminum oxide (Al ₂ O ₃ ) can be obtained by heat treatment (firing) and oxidation by heat treatment A commercially available organometallic thin film coating type material [Tapuro Chemical Laboratory Co., Ltd., Ta-10-P, concentration 10% by mass] from which tantalum (Ta ₂ O ₅ ) can be obtained is mixed at different ratios. The passivation materials (c2-1) to (c2-6) shown in 9 were prepared.

  Each of the passivation materials (c2-1) to (c2-6) is a 725 μm thick 8-inch p-type silicon substrate (8Ω · cm to 12Ω) from which the natural oxide film has been removed in advance with hydrofluoric acid having a concentration of 0.49% by mass. (Cm) was spin-coated on one side, placed on a hot plate, and pre-baked at 120 ° C. for 3 minutes. Thereafter, a heat treatment (firing) was performed at 700 ° C. for 30 minutes in a nitrogen atmosphere to obtain a passivation film containing aluminum oxide and tantalum oxide. Using this passivation film, the voltage dependence of the capacitance was measured, and the fixed charge density was calculated therefrom.

  Next, each of the passivation materials (c2-1) to (c2-6) was applied to both sides of an 8-inch p-type silicon substrate, pre-baked, and heat-treated (fired) at 650 ° C. for 1 hour in a nitrogen atmosphere. ) To prepare a sample in which both surfaces of the silicon substrate were covered with a passivation film. The carrier lifetime of this sample was measured by a lifetime measuring device (Kobelco Research Institute, RTA-540).

  The results obtained are summarized in Table 9. Further, when the carrier lifetime was measured again 14 days after the preparation of the sample, the decrease in the carrier lifetime was any of the passivation films using the passivation materials (c2-1) to (c2-6) shown in Table 9. It was within -10%, and it was found that the decrease in carrier lifetime was small.

  Although the results differ depending on the ratio (mass ratio) of tantalum oxide / aluminum oxide after heat treatment (firing), the passivation materials (c2-1) to (c2-6) are all negative after heat treatment (firing). Since it showed a fixed charge and a certain carrier lifetime, it was suggested that it functions as a passivation film.

[Reference Example 2-6]
As a compound from which tantalum oxide (Ta ₂ O ₅ ) can be obtained by heat treatment (firing), 1.18 g (0.002) of commercially available tantalum (V) methoxide (structural formula: Ta (OCH ₃ ) ₅ , molecular weight: 336.12) is obtained. As a compound from which aluminum oxide (Al ₂ O ₃ ) can be obtained by heat treatment (firing), commercially available aluminum triisopropoxide (structural formula: Al (OCH (CH ₃ ) ₂ ) ₃ , molecular weight: 204.25 2.04 g (0.010 mol) was dissolved in 60 g of cyclohexane to prepare a passivation material (d2-1) having a concentration of 5% by mass.

Passivation of passivation material (d2-1) to one side of a 725 μm thick 8-inch p-type silicon substrate (8 Ω · cm to 12 Ω · cm) with natural oxide film removed beforehand with hydrofluoric acid at a concentration of 0.49% by mass It was applied and placed on a hot plate and prebaked at 120 ° C. for 3 minutes. Thereafter, heating was performed at 700 ° C. for 1 hour in a nitrogen atmosphere to obtain a passivation film containing aluminum oxide and tantalum oxide. When the film thickness was measured with an ellipsometer, it was 40 nm. As a result of elemental analysis, it was found that Ta / Al / C = 75/22/3 (wt%). When the FT-IR of the passivation film was measured, a peak due to a very few alkyl groups was observed in the vicinity of 1200 cm ⁻¹ .

Next, a plurality of aluminum electrodes having a diameter of 1 mm were formed on the above-described passivation film by vapor deposition through a metal mask, thereby manufacturing a capacitor having a metal-insulator-semiconductor (MIS) structure. . The voltage dependence (CV characteristics) of the capacitance of this capacitor was measured with a commercially available prober and LCR meter (HP, 4275A). As a result, it was found that the flat band voltage (Vfb) was shifted from an ideal value of −0.81 V to −0.30 V. From this shift amount, it was found that the passivation film obtained from the passivation material (d2-1) showed a negative fixed charge at a fixed charge density (Nf) of −6.2 × 10 ¹⁰ cm ⁻² .

  In the same manner as described above, the passivation material (d2-1) was applied to both sides of an 8-inch p-type silicon substrate, pre-baked, and subjected to heat treatment (baking) at 600 ° C. for 1 hour in a nitrogen atmosphere. A sample in which both surfaces of the substrate were covered with a passivation film was produced. The carrier lifetime of this sample was measured by a lifetime measuring device (Kobelco Research Institute, RTA-540). As a result, the carrier lifetime was 610 μs. For comparison, the same 8-inch p-type silicon substrate was measured by passivation using the iodine passivation method, and the carrier lifetime was 1100 μs.

  From the above, it was found that the passivation film obtained by heat-treating the passivation material (d2-1) exhibits a certain degree of passivation performance and a negative fixed charge.

[Reference Example 2-7]
As a compound for obtaining tantalum oxide (Ta ₂ O ₅ ) by heat treatment (firing), 1.18 g (0.005 mol) of commercially available tantalum (V) methoxide (structural formula: Ta (OCH ₃ ) ₅ , molecular weight: 336.12) ) And aluminum oxide (Al ₂ O ₃ ) obtained by heat treatment (firing), a commercially available aluminum triisopropoxide (structure: Al (OCH (CH ₃ ) ₂ ) ₃ , molecular weight: 204.25) 1.02 g (0.005 mol) and 10 g of novolak resin were dissolved in a mixture of 10 g of diethylene glycol monobutyl ether acetate and 10 g of cyclohexane to prepare a passivation material (d2-2).

Passivation of passivation material (d2-2) on one side of a 725 μm thick 8-inch p-type silicon substrate (8 Ω · cm to 12 Ω · cm) with natural oxide film removed beforehand with hydrofluoric acid at a concentration of 0.49% by mass This was applied and prebaked at 120 ° C. for 3 minutes on a hot plate. Thereafter, heating was performed at 650 ° C. for 1 hour in a nitrogen atmosphere to obtain a passivation film containing aluminum oxide and tantalum oxide. When the film thickness was measured with an ellipsometer, it was 18 nm. As a result of elemental analysis, it was found that Ta / Al / C = 72/20/8 (wt%). When the FT-IR of the passivation film was measured, a peak due to a very few alkyl groups was observed in the vicinity of 1200 cm ⁻¹ .

Next, a plurality of aluminum electrodes having a diameter of 1 mm were formed on the above-described passivation film by vapor deposition through a metal mask, thereby manufacturing a capacitor having a metal-insulator-semiconductor (MIS) structure. . The voltage dependence (CV characteristics) of the capacitance of this capacitor was measured with a commercially available prober and LCR meter (HP, 4275A). As a result, it was found that the flat band voltage (Vfb) shifted from an ideal value of −0.81 V to −0.43 V. From this shift amount, it was found that the passivation film obtained from the passivation material (d-2) had a fixed charge density (Nf) of −5.5 × 10 ¹⁰ cm ⁻² and a negative fixed charge.

  In the same manner as above, the passivation material (d2-2) was applied to both sides of an 8-inch p-type silicon substrate, pre-baked, and subjected to heat treatment (baking) at 600 ° C. for 1 hour in a nitrogen atmosphere. A sample in which both surfaces of the substrate were covered with a passivation film was produced. The carrier lifetime of this sample was measured by a lifetime measuring device (Kobelco Research Institute, RTA-540). As a result, the carrier lifetime was 250 μs. For comparison, the same 8-inch p-type silicon substrate was measured by passivation using the iodine passivation method, and the carrier lifetime was 1100 μs.

  From the above, it was found that the passivation film obtained by heat-treating (sintering) the passivation material (d2-2) exhibited a certain degree of passivation performance and a negative fixed charge.

<When two or more vanadium group element oxides are used>
[Reference Example 2-8]
Commercially available organometallic thin film coating type material that can obtain aluminum oxide (Al ₂ O ₃ ) by heat treatment (firing) [High Purity Chemical Laboratory, SYM-AL04, concentration 2.3 mass%], heat treatment (firing) Commercially available organometallic thin film coating type material (VCO, Co., Ltd., V-02, concentration 2% by mass) from which vanadium oxide (V ₂ O ₅ ) can be obtained by heat treatment, and tantalum oxide (Ta ₂ O ₅ ), a commercially available organometallic thin film coating material [High Purity Chemical Laboratory, Ta-10-P, concentration 10% by mass] is mixed to form a passivation material (e2) that is a coating material. -1) was prepared (see Table 10).

By commercially available organometallic thin film coating type material [Coal Chemical Industries Ltd. SYM-AL04, concentration 2.3 mass%] from which aluminum oxide (Al ₂ O ₃ ) can be obtained by heat treatment (firing), heat treatment (firing) Niobium oxide (Nb ₂ O) by commercially available organometallic thin film coating type material (Vitamin Co., Ltd., V-02, concentration 2 mass%) from which vanadium oxide (V ₂ O ₅ ) is obtained, and heat treatment (firing) ₅ ) A commercially available organometallic thin film coating type material [Co., Ltd., High Purity Chemical Laboratory Co., Ltd., Nb-05, concentration 5 mass%] is mixed to obtain a passivation material (e2-2) which is a coating type material. Prepared (see Table 10).

By commercially available organometallic thin film coating type material [Coal Chemical Industries Ltd. SYM-AL04, concentration 2.3 mass%] from which aluminum oxide (Al ₂ O ₃ ) can be obtained by heat treatment (firing), heat treatment (firing) Niobium oxide (Nb) by commercially available organometallic thin film coating material [Tapuro Chemical Laboratories Ta-10-P, concentration 10% by mass] from which tantalum oxide (Ta ₂ O ₅ ) can be obtained, and heat treatment (firing) ₂ O ₅ ), a commercially available organometallic thin film coating material [High Purity Chemical Laboratory Nb-05, concentration 5 mass%] is mixed to form a passivation material (e2-3) that is a coating material. Was prepared (see Table 10).

By commercially available organometallic thin film coating type material [Coal Chemical Industries Ltd. SYM-AL04, concentration 2.3 mass%] from which aluminum oxide (Al ₂ O ₃ ) can be obtained by heat treatment (firing), heat treatment (firing) Tantalum oxide (Ta ₂ O ₅ ) by commercially available organic metal thin film coating type material [Co., Ltd., Purity Chemical Laboratory V-02, concentration 2 mass%] from which vanadium oxide (V ₂ O ₅ ) is obtained, and heat treatment (firing) Niobium oxide (Nb ₂ O ₅ ) can be obtained by a commercially available organometallic thin film coating type material [High purity chemical research laboratory Ta-10-P, concentration 10% by mass] and heat treatment (firing). Commercially available organic metal thin film coating type material [Co., Ltd. High Purity Chemical Laboratory Nb-05, concentration 5 mass%] was mixed to prepare a passivation material (e2-4) which is a coating type material (see Table 10). ).

  Each of the passivation materials (e2-1) to (e2-4) has a thickness of 725 μm and 8 inches, in which the natural oxide film is previously removed with hydrofluoric acid having a concentration of 0.49% by mass, as in Reference Example 2-1. A p-type silicon substrate (8 Ω · cm to 12 Ω · cm) was spin-coated on one side, placed on a hot plate, and pre-baked at 120 ° C. for 3 minutes. Thereafter, a heat treatment (firing) was performed at 650 ° C. for 1 hour in a nitrogen atmosphere to obtain a passivation film containing aluminum oxide and two or more vanadium group element oxides.

  Using the passivation film obtained above, the voltage dependence of the capacitance was measured, and the fixed charge density was calculated therefrom.

  Next, each of the passivation materials (e2-1) to (e2-4) is applied to both sides of an 8-inch p-type silicon substrate, pre-baked, and heat-treated (fired) at 650 ° C. for 1 hour in a nitrogen atmosphere. ) To prepare a sample in which both surfaces of the silicon substrate were covered with a passivation film. The carrier lifetime of this sample was measured by a lifetime measuring device (Kobelco Research Institute, RTA-540).

  The results obtained are summarized in Table 10.

  Passivation using passivation materials (e2-1) to (e2-4), depending on the ratio (mass ratio) of the oxide of two or more vanadium group elements and the aluminum oxide after heat treatment (firing). Regarding the films, all showed negative fixed charges after heat treatment (firing), and the carrier lifetime also showed a certain value, suggesting that it functions as a passivation film.

[Reference Example 2-9]
Similar to Reference Example 2-1, a commercially available organometallic thin film coated material from which aluminum oxide (Al ₂ O ₃ ) can be obtained by heat treatment (firing) [High Purity Chemical Laboratory, SYM-AL04, concentration 2 .3 mass%] and a commercially available organic metal thin film coating type material that can be obtained by heat treatment (firing) vanadium oxide (V ₂ O ₅ ) [High Purity Chemical Laboratory, V-02, concentration 2 mass%] Or a commercially available organic metal thin film coating type material [Tapuro Chemical Laboratory Co., Ltd., Ta-10-P, concentration 10% by mass] from which tantalum oxide (Ta ₂ O ₅ ) can be obtained by heat treatment (firing) is mixed. Then, passivation materials (f2-1) to (f2-8), which are application-type materials, were prepared (see Table 11).

  Moreover, the passivation material (f2-9) which used aluminum oxide independently was prepared (refer Table 11).

  As in Reference Example 2-1, each of the passivation materials (f2-1) to (f2-9) was applied to one side of a p-type silicon substrate, and then heat treatment (firing) was performed to form a passivation film. This was used to measure the voltage dependence of the capacitance, and the fixed charge density was calculated therefrom.

  Further, as in Reference Example 2-1, samples obtained by applying each of the passivation materials (f2-1) to (f2-9) to both sides of a p-type silicon substrate and heat-treating (firing) were obtained. Used to measure the carrier lifetime. The results obtained are summarized in Table 11.

  As shown in Table 11, when the aluminum oxide / vanadium oxide or tantalum oxide in the passivation material is 90/10 and 80/20, the fixed charge density varies greatly, and the negative fixed charge density is stable. However, it was confirmed that a negative fixed charge density can be realized by using aluminum oxide and niobium oxide. When measured by the CV method using a passivation material in which aluminum oxide / vanadium oxide or tantalum oxide is 90/10 and 80/20, a passivation film showing a positive fixed charge is obtained in some cases. It turns out that it has not reached to show stably. Note that a passivation film exhibiting a positive fixed charge can be used as a passivation film for an n-type silicon substrate. On the other hand, in the passivation material (f2-9) in which aluminum oxide is 100% by mass, a negative fixed charge density could not be obtained.

[Reference Example 2-10]
Using a single crystal silicon substrate with boron as a dopant as the silicon substrate 101, a solar cell element having the structure shown in FIG. 8 was manufactured. After the surface of the silicon substrate 101 was textured, a coating type phosphorous diffusion material was applied only to the light receiving surface side, and a diffusion layer 102 (phosphorus diffusion layer) was formed by heat treatment. Thereafter, the coating type phosphorus diffusing material was removed with dilute hydrofluoric acid.

  Next, a SiN film was formed on the light receiving surface side by plasma CVD as the light receiving surface antireflection film 103. Thereafter, the passivation material (a2-1) prepared in Reference Example 2-1 was applied to the region excluding the contact region (opening OA) on the back surface side of the silicon substrate 101 by an inkjet method. Thereafter, heat treatment was performed to form a passivation film 107 having an opening OA. In addition, a sample using the passivation material (c2-1) prepared in Reference Example 2-5 was separately prepared as the passivation film 107.

  Next, on the light-receiving surface antireflection film 103 (SiN film) formed on the light-receiving surface side of the silicon substrate 101, a paste mainly composed of silver was screen-printed in the shape of predetermined finger electrodes and bus bar electrodes. On the back side, a paste mainly composed of aluminum was screen-printed on the entire surface. Thereafter, heat treatment (fire-through) is performed at 850 ° C. to form electrodes (first electrode 105 and second electrode 106), and aluminum is diffused into the opening OA on the back surface to form the BSF layer 104. Thus, a solar cell element having the structure shown in FIG. 8 was formed.

  In this case, regarding the formation of the silver electrode on the light-receiving surface, the fire-through process in which the SiN film is not perforated is described. You can also

For comparison, the passivation film 107 is not formed in the above manufacturing process, aluminum paste is printed on the entire back surface, and the p ⁺ layer 114 corresponding to the BSF layer 104 and the electrode 116 corresponding to the second electrode. Was formed on the entire surface to form a solar cell element having the structure of FIG. About these solar cell elements, characteristic evaluation (a short circuit current, an open circuit voltage, a fill factor, and conversion efficiency) was performed. Characteristic evaluation was measured based on JIS-C-8913 (2005) and JIS-C-8914 (2005). The results are shown in Table 12.

  From Table 12, the solar cell element having the passivation film 107 has both the short-circuit current and the open voltage increased as compared with the solar electronic element not having the passivation film 107, and the conversion efficiency (photoelectric conversion efficiency) is 0 at the maximum. It was found to improve by 6%.

  The disclosures of Japanese Patent Application Nos. 2012-160336, 2012-218389, 2013-011934, 2013-040152, and 2013-0410153 are incorporated herein by reference in their entirety. All documents, patent applications, and technical standards mentioned in this specification are to the same extent as if each individual document, patent application, and technical standard were specifically and individually stated to be incorporated by reference, Incorporated herein by reference.

The light-receiving surface of the semiconductor substrate, a solar cell element having a passivation layer containing a specific metal oxide on at least one surface of the back and sides, decreasing over time in且one conversion efficiency superior conversion efficiency can be suppressed. This is considered to be because, for example, since the passivation layer contains a specific metal oxide, an excellent passivation effect is exhibited and the lifetime of carriers in the semiconductor substrate is extended, so that high efficiency can be achieved. Moreover, it is thought that by having the passivation layer containing the specific metal oxide, the passivation effect is maintained, and a decrease in conversion efficiency over time can be suppressed. Here, the deterioration of the solar cell characteristics over time can be evaluated by the solar cell characteristics after being left for a predetermined time in a constant temperature and humidity chamber.

Specific examples of the organoaluminum compound represented by the general formula (II), wherein n is 1 to 3, include aluminum ethyl acetoacetate diisopropylate [(ethylacetoacetate) aluminum isopropoxide ] , tris (ethylacetate). Acetato) aluminum and the like.

When the composition for forming a passivation layer contains a niobium compound, the composition of the metal oxide in the passivation layer obtained by heat-treating the composition for forming a passivation layer includes Nb ₂ O ₅ —Al ₂ O ₃ , Nb Binary complex oxides such as ₂ O ₅ —Ta ₂ O ₅ , Nb ₂ O ₅ —Y ₂ O ₃ , Nb ₂ O ₅ —V ₂ O ₅ , Nb ₂ O ₅ —HfO ₂ ; and Nb ₂ O _{5 -Al 2 O 3 -Ta 2 O 5} , Nb 2 O 5 -Y 2 O 3 -Ta 2 O 5, Nb 2 O 5 -Al 2 O 3 -V 2 O 5, Nb 2 O 5 -HfO 2 -Ta ternary composite oxide such as ₂ O _5; the Ru mentioned.

Specific examples of the liquid medium include acetone, methyl ethyl ketone, methyl n-propyl ketone, methyl isopropyl ketone, methyl n-butyl ketone, methyl isobutyl ketone, methyl n-pentyl ketone, methyl n-hexyl ketone, diethyl ketone, Ketone solvents such as dipropyl ketone, diisobutyl ketone, trimethylnonanone, cyclohexanone, cyclopentanone, methylcyclohexanone, 2,4-pentanedione, acetonylacetone; diethyl ether, methyl ethyl ether, methyl-n-propyl ether, diisopropyl Ether, tetrahydrofuran, methyltetrahydrofuran, dioxane, dimethyldioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol Rudi-n-propyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol methyl n-propyl ether, diethylene glycol methyl n-butyl ether, diethylene glycol di-n-propyl ether, diethylene glycol di- n-butyl ether, diethylene glycol methyl-n-hexyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol methyl ethyl ether, triethylene glycol methyl-n-butyl ether, triethylene glycol di-n-butyl ether, triethylene Glycolme Ru-n-hexyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol methyl ethyl ether, tetraethylene glycol methyl n-butyl ether, tetraethylene glycol di-n-butyl ether, tetraethylene glycol methyl n- Hexyl ether, tetraethylene glycol di-n-butyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol di-n-propyl ether, propylene glycol dibutyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, dipropylene glycol methyl Ethyl ether, dipropylene glycol Cyl-n-butyl ether, dipropylene glycol di-n-propyl ether, dipropylene glycol di-n-butyl ether, dipropylene glycol methyl-n-hexyl ether, tripropylene glycol dimethyl ether, tripropylene glycol diethyl ether, tripropylene glycol methyl Ethyl ether, tripropylene glycol methyl-n-butyl ether, tripropylene glycol di-n-butyl ether, tripropylene glycol methyl-n-hexyl ether, tetrapropylene glycol dimethyl ether, tetrapropylene glycol diethyl ether, tetrapropylene glycol methyl ethyl ether, tetra Propylene glycol methyl-n-butyl ether, tetrapropylene glycol Ruji -n- butyl ether, ethers such as tetrapropylene glycol methyl -n- Hekishiruete Le solvents; methyl acetate, ethyl acetate, n- propyl, isopropyl acetate, n- butyl acetate, isobutyl acetate sec- butyl acetate n- Pentyl, sec-pentyl acetate, 3-methoxybutyl acetate, methyl pentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, 2- (2-butoxyethoxy) ethyl acetate, benzyl acetate, cyclohexyl acetate, methylcyclohexyl acetate, nonyl acetate , Methyl acetoacetate, ethyl acetoacetate, acetic acid diethylene glycol methyl ether, acetic acid diethylene glycol monoethyl ether, acetic acid dipropylene glycol methyl ether, acetic acid dipropylene glycol ethyl ether, diacetic acid Recall, methoxytriethylene glycol acetate, isoamyl acetate, ethyl propionate, n-butyl propionate, isoamyl propionate, diethyl oxalate, di-n-butyl oxalate, methyl lactate, ethyl lactate, n-butyl lactate, n-lactate -Amyl, 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 -Ester solvents such as butyrolactone and γ-valerolactone; acetonitrile, N-methylpyrrolidinone, N-ethylpyrrolidi Aprotic polar solvents such as N, propylpyrrolidinone, N-butylpyrrolidinone, N-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, methyl isobutyl ketone, methyl ethyl ketone; methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, t-butanol, n-pentanol, isopentanol, 2-methylbutanol, sec-pentanol, t-pentanol, 3-methoxybutanol, n- Hexanol, 2-methylpentanol, sec-hexanol, 2-ethylbutanol, sec-heptanol, n-octanol, 2-ethylhexanol, sec-octanol, n-nonyl alcohol, n-decanol, sec-undecyl alcohol, trimethyl Nonyl alcohol, sec-tetradecyl alcohol, sec-heptadecyl alcohol, cyclohexanol, methylcyclohexanol, isobornylcyclohexanol, benzyl alcohol, ethylene glycol, 1,2-propylene glycol, 1,3-butylene glycol, diethylene glycol, Alcohol solvents such as dipropylene glycol, triethylene glycol, tripropylene glycol; ethylene glycol monomethyl ether, ethylene glycol Cole 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 Glycol monoether solvents such as monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, and tripropylene glycol monomethyl ether; Terpene solvent; water etc. These liquid media are used alone or in combination of two or more.

<Example 4>
Y ₂ O ₃ thin film coating material (High-Purity Chemical Laboratory, “Y-03”, Y ₂ O ₃ : 3% by mass, 2-ethylhexanoic acid: 12.5% by mass, n-butyl acetate: 22. 5 wt%, ethyl acetate: 8 wt%, terpine oil: 45 wt%, a viscosity adjustment agent: 9% by mass) was used as a passivation layer forming composition 4.

<Example 5>
Ethyl acetoacetate aluminum diisopropylate (“ALCH” manufactured by Kawaken Fine Chemical Co., Ltd.), pentaethoxyniobium (Hokuko Chemical Co., Ltd.), acetylacetone (Wako Pure Chemical Industries, Ltd.), xylene (Wako Pure Chemical Industries, Ltd.), 2-propanol (Wako Pure chemical Industries, Ltd.) and terpineol (Nippon terpene chemicals, Inc.) were mixed with Blend ratio shown in Table 1, it was used as a passivation layer forming composition 5.

Thereafter, a silicon nitride film as the light-receiving surface antireflection film 103 is formed on the diffusion layer 102. The method for forming the light receiving surface antireflection film 103 is not particularly limited. The light-receiving surface antireflection film 103 is preferably formed to have a thickness in the range of 50 to 100 nm and a refractive index in the range of 1.9 to 2.2. The light-receiving surface antireflection film 103 is not limited to a silicon nitride film, and may be a silicon oxide film, an aluminum oxide film, a titanium oxide film, or the like. Receiving surface antireflection film 103 such as a nitride silicic Motomaku a plasma CVD, can be manufactured by a method such as thermal CVD, it is preferably prepared in a form capable of plasma CVD at a temperature range of 350 ° C. to 500 ° C..

Although the results are different depending on the ratio (mass ratio) of niobium oxide / aluminum oxide after heat treatment (firing), the passivation materials (a-2) to (a-7) also have a carrier lifetime after heat treatment (firing). Since it showed a certain value, it was suggested that it functions as a passivation film. It can be seen that the passivation films obtained from the passivation materials (a-2) to (a-7) all stably show negative fixed charges and can be suitably used as a passivation film for a p-type silicon substrate. It was.

In the same manner as described above, the passivation material (c-2) is applied to both sides of an 8-inch p-type silicon substrate, pre-baked, and subjected to heat treatment (firing) at 600 ° C. for 1 hour in a nitrogen atmosphere to obtain silicon. A sample in which both surfaces of the substrate were covered with a passivation film was produced. The carrier lifetime of this sample was measured by a lifetime measuring device (Kobelco Research Institute , RTA-540). As a result, the carrier lifetime was 200 μs. For comparison, the same 8-inch p-type silicon substrate was measured by passivation using the iodine passivation method, and the carrier lifetime was 1100 μs.

It was found that the passivation film obtained from the passivation materials (b-1) to (b-6) has a large carrier lifetime and has a function as a passivation. In addition, when the niobium oxide / aluminum oxide ratios were 10/90 and 20/80, the fixed charge density values varied greatly, and a negative fixed charge density could not be stably obtained. It was confirmed that a negative fixed charge density can be realized by using niobium oxide. When measured by the CV method using passivation materials with niobium oxide / aluminum oxide of 10/90 and 20/80, a negative fixed charge is stably generated because a passivation film showing a positive fixed charge is obtained in some cases. It turns out that it has not reached to show. Note that a passivation film exhibiting a fixed charge can be used as a passivation film for an n-type silicon substrate.
On the other hand, a negative fixed charge density could not be obtained with the passivation material (b-7) containing 100% by mass of aluminum oxide.

Although the results are different depending on the ratio (mass ratio) of vanadium oxide / aluminum oxide after heat treatment (firing), the passivation materials (a2-2) to (a2-7) are all negative after heat treatment (firing). Since it showed a fixed charge and a certain carrier lifetime, it was suggested that it functions as a passivation film. It can be seen that the passivation films obtained from the passivation materials (a2-2) to (a2-7) all stably show negative fixed charges and can be suitably used as a passivation film for a p-type silicon substrate. It was.

From Table 12, the solar cell element having a passivation layer 107 is different from the solar cells elements having no passivation film 107 has increased short-circuit current and open circuit voltage are both conversion efficiency (photoelectric conversion efficiency) at the maximum It was found to improve by 0.6%.

Claims (16)

A semiconductor substrate having a light receiving surface, a back surface opposite to the light receiving surface, and a side surface;
A light-receiving surface electrode disposed on the light-receiving surface;
A back electrode disposed on the back surface;
At least one selected from the group consisting of Nb ₂ O ₅ , Ta ₂ O ₅ , V ₂ O ₅ , Y ₂ O ₃ and HfO ₂ disposed on at least one of the light receiving surface, the back surface and the side surface. A passivation layer containing seed compounds;
A solar cell element having The solar cell element according to claim 1, wherein the passivation layer further contains Al ₂ O ₃ .   The solar cell element according to claim 1 or 2, wherein the passivation layer is a heat-treated product of the composition for forming a passivation layer. The composition for forming a passivation layer is selected from the group consisting of Nb ₂ O ₅ , Ta ₂ O ₅ , V ₂ O ₅ , Y ₂ O ₃ , HfO ₂ and a compound represented by the following general formula (I). The solar cell element according to claim 3, comprising at least one compound.
M (OR ¹ ) _m (I)
[In Formula (I), M contains at least one metal element selected from the group consisting of Nb, Ta, V, Y, and Hf. R ¹ each independently represents an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 14 carbon atoms. m represents an integer of 0 to 5. ] The composition for forming a passivation layer contains Nb ₂ O ₅ and at least one niobium compound selected from the group consisting of compounds in which M in the general formula (I) is Nb, and the composition for forming a passivation layer The solar cell element according to claim 4, wherein the total content of the niobium compound in the product is 0.1% by mass to 99.9% by mass in terms of Nb ₂ O ₅ . The composition for forming a passivation layer further contains at least one kind of aluminum compound selected from the group consisting of compounds represented by Al ₂ O ₃ and the following general formula (II). The solar cell element as described in any one.


[In formula (II), ^{R 2} each independently represent an alkyl group having 1 to 8 carbon atoms. n represents an integer of 0 to 3. X ² and X ³ each independently represent an oxygen atom or a methylene group. R ³ , R ⁴ and R ⁵ each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. ] The solar cell element according to claim 6, wherein R ² in the general formula (II) is independently an alkyl group having 1 to 4 carbon atoms. The solar cell element according to claim 6 or 7, wherein n in the general formula (II) is an integer of 1 to 3, and R ⁵ is each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. . In the composition for forming a passivation layer, the composition for forming a passivation layer contains at least one aluminum compound selected from the group consisting of compounds represented by Al ₂ O ₃ and the general formula (II). The solar cell element as described in any one of Claims 6-8 whose content rate of the said aluminum compound is 0.1 mass%-80 mass%.   The solar cell element according to any one of claims 3 to 9, wherein the composition for forming a passivation layer further contains a liquid medium.   The solar cell element according to claim 10, wherein the liquid medium contains at least one selected from the group consisting of a hydrophobic organic solvent, an aprotic organic solvent, a terpene solvent, an ester solvent, an ether solvent, and an alcohol solvent. Forming a light receiving surface electrode on the light receiving surface of the semiconductor substrate;
Forming a back electrode on the back surface of the semiconductor substrate opposite to the light receiving surface;
From at least one of the light receiving surface, the back surface and the side surface, Nb ₂ O ₅ , Ta ₂ O ₅ , V ₂ O ₅ , Y ₂ O ₃ , HfO ₂ and a compound represented by the following general formula (I) Forming a composition layer by applying a composition for forming a passivation layer containing at least one compound selected from the group consisting of:
Heat-treating the composition layer to form a passivation layer;
The manufacturing method of the solar cell element as described in any one of Claims 1-11 which has these.
M (OR ¹ ) _m (I)
[In Formula (I), M contains at least one metal element selected from the group consisting of Nb, Ta, V, Y, and Hf. R ¹ each independently represents an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 14 carbon atoms. m represents an integer of 0 to 5. ] The solar cell according to claim 12, wherein the composition for forming a passivation layer further contains at least one aluminum compound selected from the group consisting of compounds represented by Al ₂ O ₃ and the following general formula (II). Device manufacturing method.

[In formula (II), ^{R 2} each independently represent an alkyl group having 1 to 8 carbon atoms. n represents an integer of 0 to 3. X ² and X ³ each independently represent an oxygen atom or a methylene group. R ³ , R ⁴ and R ⁵ each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. ]   The method for manufacturing a solar cell element according to claim 12 or 13, wherein a temperature of the heat treatment is 400 ° C or higher.   The process of forming the said composition layer includes providing the said composition for formation of a passivation layer by a screen printing method or the inkjet method, Manufacture of the solar cell element as described in any one of Claims 12-14. Method. The solar cell element according to any one of claims 1 to 11,
A wiring material disposed on the electrode of the solar cell element;
A solar cell module.