TWI619261B - Photovoltaic cell element, production method thereof and photovoltaic cell module - Google Patents

Abstract

The present invention provides a solar cell element comprising: a semiconductor substrate having a light receiving surface and a back surface opposite to the light receiving surface; a first impurity diffusion region arranged on a part of the light receiving surface and diffusing impurities; a second An impurity diffusion region is disposed on the light receiving surface and has a lower impurity concentration than the first impurity diffusion region; a light receiving surface electrode is disposed on at least a portion of the first impurity diffusion region; a back electrode is disposed on the back surface; and passivation A layer disposed on at least one of the light-receiving surface and the back surface, and containing 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 .

Description

Solar cell element, manufacturing method thereof, and solar cell module

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

The manufacturing steps of a conventional silicon solar cell element will be described.

First, in order to promote the light confinement effect and achieve high efficiency, a p-type silicon substrate having a textured structure formed on the light receiving surface side is prepared, followed by a mixed gas environment of phosphorus oxychloride (POCl ₃ ), nitrogen, and oxygen. During the treatment at 800 ° C to 900 ° C for several tens of minutes, an n-type diffusion layer is uniformly formed. In this conventional method, since the diffusion of phosphorus is performed using a mixed gas, an n-type diffusion layer is formed not only on the surface serving as a light receiving surface but also on the side surfaces and the back surface. Therefore, side etching is performed to remove the n-type diffusion layer formed on the side. In addition, the n-type diffusion layer formed on the back surface must be converted into a p ⁺ -type diffusion layer. Therefore, an aluminum paste containing aluminum powder, glass frit, a dispersion medium, an organic binder, and the like is applied to the entire back surface, and the aluminum electrode is formed by heat treatment (calcination) to adjust the n-type diffusion layer. It is a p ⁺ -type diffusion layer, thereby obtaining an ohmic contact.

However, the conductivity of aluminum electrodes formed from aluminum paste is low. Therefore, in order to reduce the sheet resistance, the aluminum electrode usually formed on the entire back surface must have a thickness of about 10 μm to 20 μm after heat treatment. Furthermore, since the thermal expansion coefficients of silicon and aluminum are very different, a large internal stress is generated in the silicon substrate during heat treatment and cooling, which causes damage to grain boundaries, growth of crystal defects, and warpage.

In order to solve this problem, there is a method of reducing the application amount of the aluminum paste and reducing the thickness of the back electrode layer. However, if the amount of aluminum paste applied is reduced, the amount of aluminum diffused from the surface of the p-type silicon semiconductor substrate to the inside becomes insufficient. As a result, the following problem arises: the desired back surface field (BSF) effect (the effect of improving the collection efficiency of carriers generated by the presence of the p ⁺ -type diffusion layer) cannot be achieved, so the characteristics of the solar cell are reduced.

In connection with the above, a method of point contact has been proposed in which a part of the surface of a silicon substrate is provided with an aluminum paste to locally form a p ⁺ -type diffusion layer and an aluminum electrode (for example, refer to Japanese Patent No. 3107287). .

In the case of such a solar cell having a point contact structure on the side opposite to the light receiving surface (hereinafter also referred to as the back surface), it is necessary to suppress the recombination speed of minority carriers on the surface of the portion other than the aluminum electrode. As a semiconductor substrate passivation layer (hereinafter also simply referred to as a "passivation layer") for this purpose, a SiO ₂ layer or the like has been proposed (for example, refer to Japanese Patent Laid-Open No. 2004-6565). The passivation effect obtained by forming the SiO ₂ layer has the effect of capping unbonded bonds of silicon atoms in the surface layer portion of the back surface of the silicon substrate and reducing the surface energy density that causes recombination.

In addition, as another method for suppressing the recombination of minority carriers, there is a method of reducing the minority carrier density by an electric field generated by a fixed charge in the passivation layer. Such a passivation effect is generally called an electric field effect. As a material having a negative fixed charge, an aluminum oxide (Al ₂ O ₃ ) film or the like has been proposed (for example, refer to Japanese Patent No. 4767110). Such a passivation layer is usually formed by using atomic layer deposition (ALD) method, chemical vapor deposition (CVD) method, or other methods (for example, refer to the Journal of Applied Physics, 104 (2008), 113703-1 to 113703-7). In addition, as a simple method for forming an aluminum oxide layer on a semiconductor substrate, a method using a sol-gel method has been proposed (for example, refer to Thin Solid Films, 517 (2009), 6327 to 6330, and Chinese Physics Express (Chinese Physics Letters), 26 (2009), 088022-1 ~ 088102-4).

The methods described in the Journal of Applied Physics, 104 (2008), 113703-1 to 113703-7 include complex manufacturing steps such as vapor deposition, and thus it is sometimes difficult to improve productivity. In addition, the methods described in "Thin Solid Films", 517 (2009), 6327 ~ 6330 or "Chinese Physics Letters", 26 (2009), 088022-1 ~ 088102-4 The composition for forming a passivation layer may cause undesirable conditions such as gelation over time, and it is difficult to call it sufficient storage stability. Furthermore, studies on forming a passivation layer having an excellent passivation effect using an oxide containing a metal element other than aluminum have not been sufficient so far.

The present invention has been made in view of the above existing problems, and an object thereof is to provide Solar cell element having excellent conversion efficiency and suppression of degradation of solar cell characteristics over time, simple manufacturing method thereof, and solar cell having excellent conversion efficiency and suppression of degradation of solar cell characteristics over time Module.

The specific means to solve the above-mentioned problems are as follows.

<1> A solar cell element comprising: a semiconductor substrate having a light receiving surface and a back surface opposite to the light receiving surface; a first impurity diffusion region arranged on a part of the light receiving surface and having impurities diffused thereon; A diffusion region is disposed on the light receiving surface and has an impurity concentration lower than that of the first impurity diffusion region; a light receiving surface electrode is disposed on at least a portion of the first impurity diffusion region; a back electrode is disposed on the back surface; and a passivation layer Is arranged on at least one of the light receiving surface and the back surface, and contains one or more 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 .

<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 density of the passivation layer is 1.0 g / cm ³ to 10.0 g / cm ³ .

<4> The solar cell element according to any one of <1> to <3>, wherein the average thickness of the passivation layer is 5 nm to 50 μm.

<5> The solar cell element according to any one of <1> to <4>, wherein the passivation layer is a heat-treated product of a composition for a passivation film.

<6> The solar cell element according to <5>, wherein the composition for a passivation film contains a material 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 One or more of the group consisting of the compound represented by formula (I), M (OR ¹ ) _m (I)

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

<7> The solar cell element according to <6>, wherein the composition for forming a passivation layer further contains one selected from the group consisting of Al ₂ O ₃ and a compound represented by the following general formula (II) The above aluminum compounds,

In the formula, 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 independently represent an oxygen atom or a methylene group; R ³ , R ^4, and R ⁵ Each independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.

<8> The solar cell element according to <7>, wherein in the general formula (II), R ^{2 is} each independently an alkyl group having 1 to 4 carbon atoms.

<9> The solar cell element according to <7> or <8>, wherein in the general formula (II), n is an integer of 1 to 3, and R ^{5 is} each independently a hydrogen atom or a carbon number of 4 or 5 alkyl.

<10> The solar cell element according to any one of <7> to <9>, wherein the composition for forming a passivation layer contains a compound selected from the group consisting of Al ₂ O ₃ and the compound represented by the general formula (II) One or more aluminum compounds in the group, and the total content of the aluminum compounds in the composition for forming a passivation layer is 0.1% to 80% by mass.

<11> The solar cell element according to any one of <6> to <10>, wherein the composition for forming a passivation layer contains a compound selected from the group consisting of Nb ₂ O ₅ and M in the general formula (I) where N is Nb One or more niobium compounds in the formed group, and the total content of the niobium compound in the composition for forming a passivation layer is 0.1% to 99.9% by mass in terms of Nb ₂ O ₅ .

<12> The solar cell element according to any one of <5> to <11>, wherein the composition for forming a passivation layer contains a liquid medium.

<13> The solar cell element according to <12>, wherein the liquid medium contains a group 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. At least one of.

<14> A method for manufacturing a solar cell element, which is the method for manufacturing a solar cell element according to any one of <1> to <13>, including the steps of: having a light-receiving surface and being opposite to the light-receiving surface; A step of forming a first impurity diffusion region on a part of the light receiving surface of the semiconductor substrate on the back side; a step of forming a second impurity diffusion region having an impurity concentration lower than the first impurity diffusion region on the light receiving surface; A step of forming a light-receiving surface electrode on at least a part of an impurity diffusion region; a step of forming a back-surface electrode on the back surface; and providing a passivation layer on at least one surface selected from the group consisting of the light-receiving surface and the back surface A step of forming a composition layer. The composition for forming a passivation layer contains a compound 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 the following general formula (I). One or more of the group consisting of the represented compound; and heat-treating the composition layer to form a composition containing a material 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 group Step of one or more passivation layers in a group; M (OR ¹ ) _m (I)

In the formula, M contains at least one metal element selected from the group consisting of niobium (Nb), tantalum (Ta), vanadium (V), yttrium (Y), and hafnium (Hf); R ¹ each independently represents carbon An alkyl group having 1 to 8 or an aryl group having 6 to 14 carbons; m represents an integer of 1 to 5.

<15> The method for producing a solar cell element according to <14>, wherein the composition for forming a passivation layer further contains a group selected from the group consisting of Al ₂ O ₃ and a compound represented by the following general formula (II) More than one of them,

In the formula, 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 independently represent an oxygen atom or a methylene group; R ³ , R ^4, and R ⁵ Each independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.

<16> The method for producing a solar cell element according to <14> or <15>, wherein the temperature of the heat treatment is 400 ° C or higher.

<17> The method for manufacturing a solar cell element according to any one of <14> to <16>, wherein the step of forming the composition layer includes forming the passivation layer using a screen printing method or an inkjet method. Using composition.

<18> A solar cell module having: such as <1> to <13> The solar cell element according to any one of the above, and a wiring material disposed on an electrode of the solar cell element.

According to the present invention, it is possible to provide a solar cell element having excellent conversion efficiency and time-dependent reduction of solar cell characteristics, a simple manufacturing method thereof, and Reduction of suppressed solar cell modules.

10‧‧‧p-type semiconductor substrate

11‧‧‧n-type diffusion region forming composition

Calcined composition of 12‧‧‧n-type diffusion region forming composition

13‧‧‧The first n-type diffusion area

14‧‧‧PSG layer

15‧‧‧second n-type diffusion region

16‧‧‧p-type diffusion region forming composition

16'‧‧‧p-type diffusion region forming composition

17‧‧‧p ⁺ type diffusion area

18, 103, 113‧‧‧Anti-reflective film

19‧‧‧ passivation layer

20‧‧‧ light receiving electrode

21‧‧‧Back electrode

50‧‧‧ light-receiving bus bar electrode

51‧‧‧ light-receiving finger electrode

60, OA‧‧‧ opening

61‧‧‧Non-opening

101, 111‧‧‧ silicon substrate

102, 112‧‧‧ diffusion layer

104‧‧‧BSF floor

105、115‧‧‧First electrode

106‧‧‧Second electrode

107‧‧‧ passivation film

114‧‧‧p ⁺ layer

116‧‧‧electrode

L1, L2, L3, L4, L5‧‧‧ length

L8, L9‧‧‧Width

FIG. 1 is a cross-sectional view schematically showing an example of a method for manufacturing a solar cell element according to this embodiment.

FIG. 2 is a plan view schematically showing an example of the arrangement of the back electrode of the solar cell element according to this embodiment.

FIG. 3 is a plan view schematically showing another example of the arrangement of the back electrode of the solar cell element according to this embodiment.

FIG. 4 is a plan view schematically showing an example of the arrangement of the light-receiving surface electrodes of the solar cell element according to this embodiment.

FIG. 5 is a plan view schematically showing an example of the arrangement of the passivation layer and the back surface electrode of the solar cell element according to this embodiment.

FIG. 6 is a plan view schematically showing another example of the arrangement of the passivation layer and the back surface electrode of the solar cell element according to this embodiment.

FIG. 7 shows a screen mask for forming a light-receiving surface electrode according to this embodiment. An example of a floor plan.

FIG. 8 is a plan view showing an example of a screen mask for forming a back electrode in this embodiment.

FIG. 9 is a cross-sectional view showing a structure of a double-sided electrode type solar cell element.

10 is a cross-sectional view showing a first configuration example of a solar cell element according to a reference embodiment.

11 is a cross-sectional view showing a second configuration example of a solar cell element according to a reference embodiment.

12 is a cross-sectional view showing a third configuration example of a solar cell element according to a reference embodiment.

13 is a cross-sectional view showing a fourth configuration example of a solar cell element according to a reference embodiment.

14 is a cross-sectional view showing another configuration example of a solar cell element according to a reference embodiment.

In this specification, the term "step" does not only refer to an independent step. Even if it cannot be clearly distinguished from other steps, as long as the purpose of the step can be achieved, it is included in the term. In addition, the numerical range indicated by "~" indicates a range including the numerical value described before and after "~" as the minimum value and the maximum value, respectively. Further, regarding the content of each component in the composition, when there are a plurality of substances corresponding to each component in the composition, unless otherwise specified, it means the total amount of the plurality of substances present in the composition. In addition, in this specification, the term "layer" In addition to the configuration of the shape formed on the entire surface when viewed in the form of a plan view, the configuration includes the configuration of the shape formed on a part.

<Solar cell element>

The solar cell element of the present invention has a light receiving surface and a back surface opposite to the light receiving surface, the light receiving surface having a first impurity diffusion region containing impurities, a second impurity diffusion region having an impurity concentration lower than the first impurity diffusion region, and The light-receiving surface electrode disposed on at least a part of the first impurity diffusion region, the back surface has a back surface electrode, and at least one selected from the group consisting of the light-receiving surface and the back surface has a passivation layer containing One or more of the groups consisting of ₂ O ₅ , Ta ₂ O ₅ , V ₂ O ₅ , Y ₂ O ₃ and HfO ₂ (hereinafter also referred to as “specific metal oxides”). Metal elements are also called "specific metal elements").

A solar cell element having an electrode and a passivation layer containing a specific metal oxide on the back surface of the semiconductor substrate is excellent in conversion efficiency, and degradation of solar cell characteristics over time is suppressed. The reason is considered to be, for example, that since the passivation layer contains a specific metal oxide, an excellent passivation effect is exhibited, and the lifetime of the carrier in the semiconductor substrate is prolonged, so that high efficiency can be achieved. In addition, it is considered that the passivation effect of the passivation layer can be maintained by containing a specific metal oxide, and the deterioration of the solar cell characteristics (for example, conversion efficiency) over time can be suppressed. Here, the degradation of the solar cell characteristics over time can be evaluated by the solar cell characteristics after being left in a constant temperature and humidity tank for a predetermined time.

The reason why a solar cell element having an electrode and a passivation layer containing a specific metal oxide on the back surface of a semiconductor substrate is excellent in conversion efficiency and suppresses deterioration of solar cell characteristics over time can be considered as follows. That is, the specific metal oxide is a compound having a fixed charge. It is considered that by the presence of a compound having a fixed charge on the surface of the semiconductor substrate, band bending is generated and carrier recombination is suppressed. In addition, even if the compound has a small fixed charge or does not have a fixed charge, it is only necessary to show a passivation effect such as a function of repairing defects on the surface of the semiconductor substrate.

The fixed charge of the compound existing on the surface of the semiconductor substrate can be evaluated by a capacitance-voltage measurement (Capacitance Voltage Measurement, CV). When the CV method is used to evaluate the surface level density of a passivation layer formed by subjecting a composition for forming a passivation layer described later to a heat treatment, compared with the case of a passivation layer formed by an ALD method or a CVD method, the density may be more severe. Big value. However, the electric field effect of the passivation layer of the solar cell element of the present invention is large, the concentration of minority carriers is reduced, and the surface life time τ _{s is} increased. Therefore, the surface level density is relatively unproblematic.

In this specification, the passivation effect of a semiconductor substrate can be evaluated by using a device such as WT-2000PVN of Japan Semilab Co., Ltd., and reflecting the passivation layer formed by the reflection microwave conduction attenuation method. The effective life of the minority carriers in the semiconductor substrate is measured.

Here, the effective life time τ is represented by the bulk life time τ _b inside the semiconductor substrate and the surface life time τ _{s of the} surface of the semiconductor substrate as shown in the following formula (A). When the surface energy density of the surface of the semiconductor substrate is small, τ _s becomes longer, and as a result, the effective life time τ becomes longer. In addition, even if there are fewer defects such as dangling bonds inside the semiconductor substrate, the body life τ _b becomes longer and the effective life τ becomes longer. That is, the interface characteristics of the passivation layer and the semiconductor substrate, and the internal characteristics of the semiconductor substrate such as dangling bonds can be evaluated by measuring the effective life time τ.

1 / τ = 1 / τ _b + 1 / τ _s (A)

In addition, a longer effective life indicates a slower recombination rate of minority carriers. In addition, by using a semiconductor substrate having a long effective life to constitute a solar cell element, conversion efficiency is improved.

The solar cell element includes a semiconductor substrate having a light receiving surface and a back surface opposite to the light receiving surface. Examples of the semiconductor substrate include those in which p-type impurities or n-type impurities are doped (diffused) in silicon, germanium, or the like. 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, a semiconductor substrate on which the passivation layer is formed is preferably a p-type layer. The p-type layer on the semiconductor substrate may be a p-type layer derived from a p-type semiconductor substrate, or may be formed on an n-type semiconductor substrate or a p-type semiconductor substrate as a p-type diffusion region or a p ⁺ -type diffusion region.

In the above semiconductor substrate, it is preferable that the p-type region and the n-type region are pn-bonded. That is, when the semiconductor substrate is a p-type semiconductor substrate, it is preferable that an n-type region is formed on the light receiving surface or the back surface of the semiconductor substrate. When the semiconductor substrate is an n-type semiconductor substrate, it is preferably on the light receiving surface of the semiconductor substrate. Or, a p-type region is formed on the back surface. A method for forming a p-type region or an n-type region on a semiconductor substrate is not particularly limited, and may be appropriately selected from methods generally used.

The thickness of the semiconductor substrate is not particularly limited, and can be appropriately selected according to the purpose. For example, it can be set to 50 μm to 1000 μm, and preferably 75 μm to 750 μm. The shape and size of the semiconductor substrate are not particularly limited. For example, the shape can be a square with a side of 125 mm to 156 mm.

The solar cell element of the present invention includes a semiconductor substrate having a light-receiving surface electrode disposed on a light-receiving surface and a back-surface electrode disposed on a back surface opposite to the light-receiving surface. The light-receiving surface electrode is at least a part of a first impurity diffusion region having a relatively high impurity concentration arranged on a light-receiving surface of a semiconductor substrate. The light-receiving surface electrode has a function of collecting a current on the light-receiving surface of the semiconductor substrate, for example. The back surface electrode disposed on the back surface of the semiconductor substrate has a function of outputting current to the outside, for example.

The material and thickness of the light receiving surface electrode are not particularly limited. Examples of the material of the light-receiving surface electrode include silver, copper, and aluminum. From the viewpoint of conductivity and homogeneity, the thickness of the light-receiving surface electrode is preferably from 0.1 μm to 50 μm.

The shape and size of the light-receiving surface electrode are not particularly limited. For example, in the total area of the first impurity diffusion region, the size of the region where the light-receiving surface electrode is formed is preferably 50% or more, and more preferably 80% or more.

The material of the back electrode is not particularly limited, and examples thereof include silver, copper, and aluminum. From the viewpoint of forming a back electrode and forming a p ⁺ -type diffusion region, the material of the back electrode is preferably aluminum. The thickness of the back electrode is not particularly limited, but from the viewpoints of conductivity and warpage of the substrate, it is preferably from 0.1 μm to 50 μm.

The light-receiving surface electrode and the back surface electrode can be manufactured by a commonly used method. For example, an electrode can be manufactured by applying a paste for electrode formation such as silver paste, aluminum paste, and copper paste on a desired region of a semiconductor substrate, and performing heat treatment (calcination) if necessary.

The first impurity diffusion region and the second impurity diffusion region are n-type diffusion regions or p-type diffusion regions.

When the semiconductor substrate is a p-type semiconductor, a first n-type diffusion region as a first impurity diffusion region and a n-type impurity concentration as a second impurity diffusion region are arranged on the light-receiving surface of the semiconductor substrate. A second n-type diffusion region. Preferably, the first n-type diffusion region is disposed in a region where the light-receiving surface electrode is formed, and the second n-type diffusion region is disposed in a region other than the region where the light-receiving surface electrode is formed. By disposing the first n-type diffusion region having an impurity concentration higher than that of the second n-type diffusion region in the region where the light-receiving surface electrode is formed, the contact resistance with the electrode can be reduced. In a solar cell element using a semiconductor substrate having such a structure, the series resistance can be reduced.

On the other hand, by arranging a second n-type diffusion region having a low impurity concentration in a region other than the region where the light-receiving surface electrode is disposed, it is possible to effectively use short-wavelength sunlight, and to reduce the amount of light generated by absorption of sunlight. Electron and hole recombination speed. This structure is called a selective emitter structure.

When the semiconductor substrate is an n-type semiconductor, a first p-type diffusion region as a first impurity diffusion region, And the second p-type diffusion region having a lower p-type impurity concentration as the second impurity diffusion region is lower than the first p-type diffusion region. Preferably, the first p-type diffusion region is disposed in a region other than the region where the light-receiving surface electrode is formed, and the second p-type diffusion region is disposed in a region other than the region where the light-receiving surface electrode is formed.

The solar cell element having the selective emitter structure as described above can generate electricity with high conversion efficiency. The sheet resistance of the first impurity diffusion region (the first n-type diffusion region or the first p-type diffusion region) is preferably 20 Ω / □ to 60 Ω / □, more preferably 30 Ω / □ to 55 Ω / □, and further preferably 35 Ω / □. □ ~ 50Ω / □. The sheet resistance of the second impurity diffusion region (the second n-type diffusion region or the second p-type diffusion region) is preferably 60 Ω / □ to 150 Ω / □, more preferably 70 Ω / □ to 130 Ω / □, and further preferably 80 Ω / □. □ ~ 120Ω / □. The sheet resistance can be measured by a four-probe method.

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 and the back surface of the semiconductor substrate. The passivation layer may be provided on a part or the entire surface of at least one of the light-receiving surface and the back surface, and is preferably provided on a part or all of a region other than a region where the back electrode is disposed on the back surface. In addition, the passivation layer may be provided on at least a part of the side surface and the light receiving surface of the semiconductor substrate in addition to the back surface.

The shape and size in the surface direction of the region where the passivation layer is formed on at least one of the light-receiving surface and the back surface of the semiconductor substrate are not particularly limited, and can be appropriately selected depending on the purpose and the like. When a passivation layer is formed on a part of the back surface of a semiconductor substrate, it is preferable to form a passivation layer on a part or all of a region other than a region where a back electrode is disposed, and more preferably a region where a back electrode is disposed. other than A passivation layer is formed in the entire region.

From the viewpoint of more fully obtaining the passivation effect, it is more preferable that there is no region where neither the back electrode nor the passivation layer exists between the back electrode and the passivation layer. In this case, there may be a region where the back electrode and the passivation film overlap.

From the viewpoint of obtaining a sufficient passivation effect, the content rate of the specific metal oxide contained in the passivation layer is preferably 0.1% to 100% by mass, more preferably 1% to 100% by mass, and even more preferably 10%. Mass% ~ 100%.

The content rate of the specific metal oxide contained in the passivation layer can be measured as follows. That is, the proportion of inorganic substances is calculated by thermogravimetric analysis using atomic absorption spectrometry, inductively coupled plasma emission spectrometry, thermogravimetric analysis, X-ray photoelectric spectrometry, and the like. Then, the ratio of the compound containing the specific metal element in the inorganic substance is calculated by atomic absorption spectrometry, inductively coupled plasma emission spectrometry, etc., and the specific metal content is calculated by X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, etc. The ratio of the specific metal oxide in the compound of the element can obtain the content rate of the specific metal oxide.

The passivation layer may further contain a metal oxide other than the specific metal oxide. Such a metal oxide is preferably a compound having a fixed charge similar to a specific metal oxide, and examples thereof include alumina, silicon oxide, titanium oxide, gallium oxide, zirconia, boron oxide, indium oxide, phosphorus oxide, and zinc oxide. , Lanthanum oxide, scandium oxide, neodymium oxide, scandium oxide, scandium oxide, scandium oxide, scandium oxide, scandium oxide, scandium oxide, scandium oxide, scandium oxide, scandium oxide, scandium oxide, scandium oxide, etc. From the viewpoint of obtaining a high passivation effect and a stable passivation effect, the specific metal oxide contained in the passivation layer The other metal oxides are preferably alumina, silica, titania, zirconia, and neodymium oxide, and more preferably alumina.

When the passivation layer contains a metal oxide other than a specific metal oxide, its content rate is preferably 99.9% by mass or less, and more preferably 80% by mass or less. The content rate of the metal oxide other than the specific metal oxide contained in the passivation layer can be measured in the same manner as the measurement of the content rate of the specific metal oxide described above.

<Composition for forming passivation layer>

The passivation layer of the solar cell element of the present invention is preferably a heat-treated product of a 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, and may include the specific metal oxide itself, or a metal alkoxide containing a specific metal element, etc. Precursors of specific metal oxides. Hereinafter, the specific metal oxide and its precursor are also referred to as a specific metal compound.

The specific metal compound is preferably at least one selected from the group consisting of the specific metal oxide itself and a compound represented by the following general formula (I) (hereinafter also referred to as a compound of formula (I)).

M (OR ¹ ) _m (I)

In the formula, 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 from 1 to 5.

In the general formula (I), M contains at least one metal element selected from the group consisting of Nb, Ta, V, Y, and Hf. For passivation effect and passivation layer formation From the viewpoints of storage stability of the composition and workability when preparing a composition for forming a passivation layer, M is preferably Nb, Ta, or Y. Further, 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 more preferably contains Nb. At least one of the group consisting of, Ta, V, and Hf.

In the general formula (I), R ¹ each independently represents an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 14 carbon atoms, and is preferably an alkyl group having 1 to 4 carbon atoms or 6 to 8 carbon atoms. Aryl. The alkyl group represented by R ¹ may be linear or branched. Specific examples of the alkyl group represented by R ¹ include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, 2-butyl, third butyl, pentyl, hexyl, heptyl, and octyl. Group, 2-ethylhexyl, phenyl and the like. 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 of the alkyl group include a halogen atom, an amine group, a hydroxyl group, a carboxyl group, a fluorenyl group, and a nitro group. Examples of the substituent of the aryl group include a halogen atom, a methyl group, an ethyl group, an isopropyl group, an amine group, a hydroxyl group, a carboxyl group, a fluorenyl group, and a nitro group.

Among these, in terms of storage stability and passivation effect, 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.

In the general formula (I), m represents an integer of 1 to 5. When M is Nb, m is preferably 5; when M is Ta, m is 5; when M is VO, m is 3; when M is Y; Preferably, m is 3, and when M is Hf, m is preferably 4.

From the viewpoint of the passivation effect, the compound represented by the general formula (I) is preferably M is Nb, Ta, or Y. From the viewpoint of storage stability and the passivation effect, R ¹ is more preferably a carbon number of 1 to The unsubstituted alkyl group of 4 is preferably an integer of 1 to 5 from the viewpoint of storage stability.

The compound of formula (I) may be solid or liquid. From the viewpoint of the storage stability of the composition for forming a passivation layer and the compatibility with the organoaluminum compound when the organoaluminum compound represented by the following general formula (II) is used in combination, the compound of the formula (I) is preferably liquid.

Examples of the compound of formula (I) include: methanol niobium, ethanol niobium, isopropanol niobium, n-propanol niobium, n-butanol niobium, tertiary butanol niobium, isobutanol niobium, methanol tantalum, ethanol tantalum, and isopropanol tantalum , Tantalum n-propanol, tantalum n-butoxide, tantalum third-butoxide, tantalum isobutoxide, yttrium methanol, yttrium ethanol, yttrium isopropanol, yttrium n-propanol, yttrium n-butoxide, yttrium third butanol Yttrium butanol, vanadium methanol oxide, vanadium ethanol alcohol, vanadium isopropanol oxide, n-propanol vanadium oxide, n-butanol vanadium oxide, third butanol vanadium oxide, isobutanol vanadium oxide, methanol gadolinium, ethanol gadolinium, isopropyl alcohol Propanol 铪, n-propanol 铪, n-butanol 铪, tertiary butanol 铪, isobutanol 铪, etc. Among them, ethanol niobium, n-propanol niobium, n-butanol niobium, tantalum ethanol, and n-propanol are preferred. Tantalum, tantalum n-butoxide, yttrium isopropoxide and yttrium n-butoxide. From the viewpoint of obtaining a negative fixed charge density, ethanol niobium, n-propanol niobium, n-butanol niobium, tantalum ethanol, tantalum n-propanol, tantalum n-butoxide, ethanol vanadium oxide, and n-propanol vanadium oxide are preferred. , N-butanol vanadium oxide, ethanol thorium, n-propanol thorium and n-butanol thorium.

The compound of formula (I) may be a prepared product or a commercially available product. Examples of commercially available products include: Pentamethoxyniobium, Pentaethoxyniobium, Pentaisopropoxyniobium, Penta-n-propoxyniobium, Penta-isobutoxyniobium, Penta-N Butyl niobium, penta-2-butoxy niobium, pentamethoxy tantalum, pentaethoxy tantalum, pentaisopropoxy Tantalum, penta-n-propoxy tantalum, penta-isobutoxy tantalum, penta-n-butoxy tantalum, penta-2-butoxy tantalum, penta-third butoxy tantalum, trimethanol vanadium oxide (V), three Vanadium ethoxylate (V), Vanadium triisopropoxide (V), Vanadium tri-n-propanol (V), Vanadium tri-isobutanol (V), Vanadium tri-n-butanol (V), Three -2-Butanol vanadium oxide (V), tri-tertiary butanol vanadium oxide (V), yttrium isopropoxide, yttrium tri-n-butoxide, tetramethoxyphosphonium, tetraethoxyphosphonium, tetra Isopropoxy hydrazone, tetra-third butoxy rhenium; Beixing Chemical Industry Co., Ltd. pentaethoxy niobium, pentaethoxy tantalum, pentabutoxy tantalum, n-butanol yttrium, third butanol rhenium ; Vanadium oxytriethanol, vanadium oxytri-n-propoxide, vanadium oxytri-n-butoxide, vanadium oxytriisobutoxide, vanadium oxytri-butanol, etc .;

In the case of preparing the compound of formula (I), a known method such as the following method may be used for preparing the compound of formula (I): the halide of the metal element (M) and the alcohol contained in the compound of formula (I) in the presence of an inactive organic solvent A method in which ammonia or an amine compound is added in order to extract a halogen (see, for example, Japanese Patent Laid-Open No. 63-227593, Japanese Patent Laid-Open No. 3-291247, etc.).

The content rate of the compound of the formula (I) contained in the composition for forming a passivation layer is appropriately selected as necessary. From the standpoint of storage stability and passivation effect, the content rate of the compound of formula (I) in the composition for forming a passivation layer can be set to 0.1% to 80% by mass, preferably 0.5% to 70% by mass, It is more preferably 1% to 60% by mass, and even more preferably 1% to 50% by mass.

When the composition for forming a passivation layer contains a compound of formula (I), a chelating agent (chelating agent) may be added. Examples of the chelating agent: Ethylene Diamine Tetraacetic Acid (EDTA), bipyridine (bipyridine), heme, naphthyridine, benzimidazolyl methylamine, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, tartaric acid, maleic acid, phthalic acid Dicarboxylic acid compounds such as formic acid, β-diketone compounds, β-ketoester compounds, and malonic acid diester compounds. From the viewpoint of chemical stability, a β-diketone compound and a β-ketoester compound are preferred.

Specific examples of β-diketone compounds include acetone, 3-methyl-2,4-pentanedione, 2,3-pentanedione, 3-ethyl-2,4-pentanedione, and 3-butane. -2,4-pentanedione, 2,2,6,6-tetramethyl-3,5-heptanedione, 2,6-dimethyl-3,5-heptanedione, 6-methyl -2,4-heptanedione, etc.

Specific examples of β-ketoester compounds include methyl ethyl acetate, ethyl ethyl acetate, propyl ethyl acetate, isobutyl ethyl acetate, butyl ethyl acetate, third butyl ethyl acetate, and ethyl ethyl acetate Amyl acetate, isoamyl acetate, hexyl acetate, n-octyl acetate, heptyl acetate, 3-pentyl acetate, 2-pentyl ethylheptanoate, 2- Ethyl butylacetamate, ethyl 4,4-dimethyl-3-oxopentanoate, ethyl 4-methyl-3-oxopentanoate, ethyl 2-ethylacetamate, hexyl Ethyl acetoacetate, methyl 4-methyl-3-oxopentanoate, isopropyl acetoacetate, ethyl 3-oxohexanoate, ethyl 3-oxopentanoate, 3-oxopentanoate Methyl ester, methyl 3-oxohexanoate, ethyl 2-methylacetamate, ethyl 3-oxoheptanoate, methyl 3-oxoheptanoate, 4,4-dimethyl-3 -Methyl oxovalerate and the like.

Specific examples of the malonic acid diester include dimethyl malonate, diethyl malonate, dipropyl malonate, diisopropyl malonate, dibutyl malonate, and di-malonate. Third butyl ester, dihexyl malonate, third butyl ethyl malonate, diethyl methylmalonate, diethyl ethylmalonate, diethyl isopropylmalonate, Butyl malonate Ethyl acetate, diethyl 2-butylmalonate, diethyl isobutylmalonate, diethyl 1-methylbutylmalonate, and the like.

In the case where the compound of formula (I) has a chelate structure, the existence of the chelate structure can be confirmed by an analysis method generally used. For example, infrared spectroscopic spectrum, nuclear magnetic resonance spectrum, and melting point can be used for confirmation.

The compound of formula (I) can also be used in a state of being hydrolyzed and dehydrated and polycondensed. In order to carry out hydrolysis and dehydration polycondensation, the reaction can be carried out in the presence of water and catalyst, or water and catalyst can be distilled off after hydrolysis and dehydration polycondensation. Examples of the catalyst include inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, boric acid, phosphoric acid, and hydrofluoric acid; and formic acid, acetic acid, propionic acid, butyric acid, oleic acid, linoleic acid, and salicylic acid. Organic acids such as acids, benzoic acid, phthalic acid, oxalic acid, lactic acid, and succinic acid. Alternatively, a base such as ammonia or amine may be added as a catalyst.

The composition for forming a passivation layer may contain a precursor of a specific metal oxide other than the compound of the formula (I). The precursor of the specific metal oxide is not particularly limited as long as it becomes the specific metal oxide by heat treatment. Specific examples include: niobic acid, niobium chloride, niobium monoxide, niobium carbide, niobium hydroxide, tantalic acid, tantalum chloride, tantalum pentabromide, vanadium oxychloride, vanadium trioxide, and oxobis (2, 4-pentanedionate) vanadium, yttrium chloride, yttrium nitrate, yttrium oxalate, yttrium stearate, yttrium carbonate, yttrium naphthenate, yttrium propionate, yttrium nitrate, yttrium octoate, thorium chloride, tetrakis (2, 4-pentanedionate) hydrazone and the like.

The composition for forming a passivation layer may further contain a metal oxide other than a specific metal compound or a precursor thereof. Examples of such metal oxides or precursors thereof include aluminum oxide, silicon oxide, titanium oxide, gallium oxide, zirconia, boron oxide, and oxide. Indium, phosphorus oxide, zinc oxide, lanthanum oxide, praseodymium oxide, neodymium oxide, praseodymium oxide, praseodymium oxide, praseodymium oxide, praseodymium oxide, praseodymium oxide, praseodymium oxide, oxide, praseodymium oxide, praseodymium oxide, praseodymium oxide, praseodymium oxide, Precursors of these oxides. From the viewpoint of stability of the passivation effect, alumina, silica, titania, zirconia, neodymium oxide, or precursors of these oxides are preferred, and from the viewpoint of high passivation effects, oxidation is more preferred. Aluminum or its precursors.

The composition for forming a passivation layer preferably contains, in addition to a specific metal compound, one or more members selected from the group consisting of alumina and its precursor. The precursor of alumina is preferably a compound represented by the following general formula (II) (hereinafter also referred to as an organoaluminum compound).

The organoaluminum compound is a compound called aluminum alkoxide, chelate aluminum, or the like. As described in "Nippon Seramikkusu Kyokai Gakujutsu Ronbunshi" and 97 (1989) 369-399, the above-mentioned organoaluminum compound becomes alumina (Al ₂ O ₃ ) by heat treatment.

In the general formula (II), R ² each independently represents an alkyl group having 1 to 8 carbon atoms. n represents an integer from 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.

In the general formula (II), R ² each independently represents an alkyl group having 1 to 8 carbon atoms, and 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, ethyl, propyl, isopropyl, butyl, isobutyl, 2-butyl, third butyl, hexyl, octyl, and ethylhexyl. . Among these, in terms of storage stability and passivation effect, the alkyl group represented by R ² 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. alkyl.

In the general formula (II), n represents an integer of 0 to 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, it is preferable that at least one of X ² and X ³ is 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 groups represented by R ³ , R ⁴ and R ⁵ are each independently 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 methyl, ethyl, propyl, isopropyl, butyl, isobutyl, 2-butyl, third butyl, hexyl, and octyl. Group, 2-ethylhexyl, 3-ethylhexyl and the like. Among these, from the viewpoints of storage stability and passivation effect, R ³ and R ⁴ in the general formula (II) are each preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 8 carbon atoms, and more preferably It is a hydrogen atom or an unsubstituted alkyl group having 1 to 4 carbon atoms.

From the viewpoint of storage stability and passivation effect, R ⁵ in the general formula (II) is preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 8 carbon atoms, and more preferably a hydrogen atom or carbon number. 1 to 4 unsubstituted alkyl.

From the viewpoint of storage stability, the organoaluminum compound represented by the general formula (II) is preferably a compound in which n is an integer of 1 to 3 and R ^{5 is} each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

From the viewpoint of storage stability and passivation effect, the organoaluminum compound represented by the general formula (II) is preferably at least one selected from the group consisting of: n is 0, and R ^{2 is} each independently carbon Compounds of alkyl groups of 1 to 4; and n is 1 to 3, R ^{2 is} independently an alkyl group of 1 to 4 carbons, at least one of X ² and X ³ is an oxygen atom, and R ³ and R ⁴ are independent A compound which is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ^{5 is} each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

Furthermore, the organoaluminum compound represented by the general formula (II) is more preferably at least one selected from the group consisting of: n is 0, and R ^{2 is} each independently an unsubstituted alkane having 1 to 4 carbon atoms. And n is 1 to 3, R ^{2 is} independently 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 is} bonded to the above oxygen atom Or R ⁴ is an alkyl group having 1 to 4 carbon atoms. When X ² or X ³ is a methylene group, R ³ or R ⁴ bonded to the methylene group is a hydrogen atom, and R ⁵ is a hydrogen atom. Compound.

Three as the organoaluminum compound represented by the general formula (II) and n is 0 Specific examples of the aluminum alkoxide include trimethoxy aluminum, triethoxy aluminum, triisopropoxy aluminum, tri-2-butoxy aluminum, mono-2-butoxy-diisopropoxy aluminum, Tri-tertiary butoxyaluminum, tri-n-butoxyaluminum, and the like.

Specific examples of the organoaluminum compound represented by the general formula (II) and n is 1 to 3 include ethyl ethylacetoacetate diisopropoxide, aluminum tris (ethylacetoacetate) aluminum, and the like.

The organoaluminum compound represented by the general formula (II) and n is 1 to 3 may be a prepared product or a commercially available product. Commercial products include, for example, the trade names ALCH, ALCH-50F, ALCH-75, ALCH-TR, ALCH-TR-20, etc. of Chuanyan Chemical Co., Ltd.

The organoaluminum compound preferably has n of 1 to 3, that is, it has a chelated aluminum structure in addition to the aluminum alkoxide structure. In a case where n is 0, that is, in the state of being in the state of an aluminum alkoxide structure, the chelating agent (chelating agent) is preferably added to the composition for forming a passivation layer. Examples of the chelating agent include the above-mentioned examples of the chelating agent.

When the organoaluminum compound has a chelate structure, the existence of the chelate structure can be confirmed by an analysis method generally used. For example, infrared spectroscopic spectrum, nuclear magnetic resonance spectrum, and melting point can be used for confirmation.

It is considered that by using aluminum alkoxide in combination with a chelating agent or using a chelated organoaluminum compound, the thermal stability and chemical stability of the organoaluminum compound are improved, and the conversion to alumina during heat treatment is suppressed. As a result, it is considered that the transition to alumina that is thermodynamically stable in a crystalline state is suppressed, and it is easy to form an alumina in an amorphous state.

In addition, the state of the metal oxide in the formed passivation layer can be confirmed by measuring X-ray diffraction (XRD). For example, it can be confirmed that XRD does not show a specific reflection pattern and it is an amorphous structure. When the composition for forming a passivation layer contains an organoaluminum compound, the alumina in the passivation layer obtained by heat-treating it preferably has an amorphous structure. If the alumina is in an amorphous state, aluminum defects or oxygen defects are easily generated, a fixed charge is easily generated in the passivation layer, and a large passivation effect is easily obtained.

The organoaluminum compound represented by the general formula (II) and n is 1 to 3 can be prepared by mixing the trialkoxyaluminum with a chelating agent. Examples of the chelating agent include compounds having a specific structure having two carbonyl groups. Specifically, when the trialkoxy aluminum is mixed with a compound having a specific structure having two carbonyl groups, at least a part of the trialkoxy aluminum alkoxide group is replaced with a compound having a specific structure to form a chelated aluminum structure. . In this case, a solvent may be present if necessary, and a heat treatment or a catalyst may be added. By replacing at least a part of the aluminum alkoxide structure with a chelated aluminum structure, the stability of the organoaluminum compound to hydrolysis and polymerization reactions is improved, and the storage stability of the composition for forming a passivation layer containing the same is further improved.

From the viewpoint of reactivity and storage stability, the compound having a specific structure having two carbonyl groups is preferably selected from the group consisting of a β-diketone compound, a β-ketoester compound, and a malonic acid diester. At least one. Specific examples of the β-diketone compound, β-ketoester compound, and malonic acid diester include the compounds described above as the chelating agent.

In the case where the organoaluminum compound has a chelated aluminum structure, as long as the chelated aluminum The number of structures is 1 to 3, and there is no particular limitation. Among them, 1 or 3 is preferable from the viewpoint of storage stability, and 1 is more preferable from the viewpoint of solubility. The number of chelated aluminum structures can be controlled, for example, by appropriately adjusting the ratio of mixing the trialkoxyaluminum with the compound capable of forming a chelate with aluminum. In addition, a compound having a desired structure may be appropriately selected from commercially available chelated aluminum compounds.

Among the organoaluminum compounds represented by the general formula (II), from the viewpoints of passivation effect and compatibility with a solvent added as needed, specifically, it is preferable to use a diisocyanate selected from ethyl acetamidine acetate. As the at least one of the group consisting of aluminum propoxide and aluminum triisopropoxide, it is more preferable to use aluminum ethyl isopropoxide diisopropoxide.

The organoaluminum compound may be liquid or solid, and is not particularly limited. From the viewpoint of passivation effect and storage stability, the uniformity of the passivation layer formed is further improved by using an organoaluminum compound having stability at normal temperature (about 10 ° C to 40 ° C) or good solubility or dispersibility. It can be improved to obtain the required passivation effect stably.

When the composition for forming a passivation layer contains one or more aluminum compounds selected from the group consisting of Al ₂ O ₃ and the organoaluminum compound, the total of the aluminum compounds in the composition for forming a passivation layer The content rate is preferably 0.1% by mass to 80% by mass, and more preferably 10% by mass to 70% by mass. From the viewpoint of high passivation effect, the total ratio of the aluminum compound in the total amount of the specific metal compound and the aluminum compound is preferably 0.1% by mass or more and 99.9% by mass or less, more preferably 0.5% by mass or more and 99% by mass % Or less, more preferably 1% by mass or more and 95% by mass or less.

When the composition for forming a passivation layer contains the aluminum compound, the composition of the specific metal oxide in the passivation layer obtained by heat-treating the composition for forming a passivation layer may include Nb ₂ O ₅ -Al ₂ O ₃ , Binary composite oxides such as Al 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 ; 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 ₂ O ₅ and other ternary compound oxides.

From the viewpoint of high passivation effect and time-dependent stability of the passivation effect, the composition for forming a passivation layer preferably contains a compound selected from the group consisting of Nb ₂ O ₅ and a compound in which M is Nb in the general formula (I). At least one niobium compound in the group. In addition, the total content of the niobium compound in the composition for forming a passivation layer is preferably 0.1% to 99.9% by mass in terms of Nb ₂ O ₅ conversion, more preferably 1% to 99% by mass, and even more preferably 5 mass% to 90 mass%. Oxidation of a specific metal in a passivation layer obtained by heat-treating a composition for forming a passivation layer containing at least one niobium compound selected from the group consisting of Nb ₂ O ₅ and a compound in which M is Nb in the general formula (I). Examples of the composition include: Nb ₂ O ₅ -Al ₂ O ₃ , Nb 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 other binary system composite oxides; 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 Ternary composite oxides such as _3- V ₂ O ₅ and Nb ₂ O ₅ -HfO ₂ -Ta ₂ O ₅ .

A composition for forming a passivation layer containing a specific metal compound is formed on a semiconductor substrate to form a composition layer in a desired shape, and the composition layer is heat-treated, whereby a passivation layer having an excellent passivation effect can be formed. Desired shape.

The reason why the passivation layer having an excellent passivation effect can be formed by heat-treating the composition for forming a passivation layer described above is considered by the inventors as follows. It is considered that by heat-treating the composition for forming a passivation layer containing a specific metal compound, defects such as metal atoms or oxygen atoms are generated, and a large fixed charge is generated near the interface with the semiconductor substrate. This large fixed charge generates an electric field near the interface of the semiconductor substrate, thereby reducing the concentration of minority carriers, and as a result, the carrier recombination speed at the interface is suppressed, so a passivation layer having an excellent passivation effect can be formed. Further, it is considered that occurrence of undesirable conditions such as gelation of the composition for forming a passivation layer is suppressed, and the storage stability over time is excellent.

(Liquid medium)

It is preferable that the said composition for passivation layer formation contains a liquid medium. When the composition for forming a passivation layer contains a liquid medium, the viscosity can be adjusted more easily, the impartability is further improved, and a more uniform passivation layer can be formed. The liquid medium is not particularly limited as long as it can dissolve or disperse the specific metal compound, and may be appropriately selected according to need.

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, dipropyl ketone, diisobutyl ketone, trimethylnonanone, cyclohexanone, cyclopentanone, methylcyclohexanone, 2,4-pentanedione, Ketone solvents such as acetone acetone; diethyl ether, methyl ethyl ether, methyl n-propyl ether, diisopropyl ether, tetrahydrofuran, methyl tetrahydrofuran, dioxane, dimethyl dioxane, ethylene glycol dimethyl ether Ether, ethylene glycol diethyl ether, ethylene glycol di-n-propyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether 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 glycol methyl n-hexyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol methyl ethyl ether, tetraethylene glycol Ethylene 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-butyl ether Propyl ether, propylene glycol dibutyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, dipropylene glycol methyl ethyl ether, dipropylene glycol methyl n-butyl ether, dipropylene glycol di-n-propyl ether, dipropylene glycol di-n-butyl ether, Dipropylene glycol methyl n-hexyl ether, tripropylene glycol dimethyl ether, tripropylene glycol diethyl ether, tripropylene glycol methyl ethyl ether, tripropylene glycol methyl n-butyl ether, tripropylene glycol di-n-butyl ether , Tripropylene glycol methyl n-hexyl ether, tetrapropylene glycol dimethyl ether, tetrapropylene glycol diethyl ether, tetrapropylene glycol methyl ethyl ether, tetrapropylene glycol methyl n-butyl ether, tetrapropylene glycol di-n-butyl ether, tetrapropylene glycol methyl n-hexyl Ether solvents such as ether, tetrapropylene glycol di-n-butyl ether; methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, 2-butyl acetate, n-pentyl acetate , 2-pentyl acetate, 3-methoxybutyl acetate, methylpentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, 2- (2-butoxyethoxy) acetate ) Ethyl acetate, benzyl acetate, cyclohexyl acetate, methyl cyclohexyl acetate, nonyl acetate, methyl ethyl acetate, ethyl ethyl acetate, diethylene glycol methyl ether, diethylene glycol monoacetate Diethyl ether, dipropylene glycol methyl ether, dipropylene glycol ethyl ether, diethylene glycol diacetate, methoxytriethylene glycol acetate, isoamyl acetate, ethyl propionate, propyl N-butyl ester, isoamyl propionate, diethyl oxalate, di-n-butyl oxalate, methyl lactate, ethyl lactate, n-butyl lactate, n-amyl lactate, ethylene glycol methyl ether propionate, ethyl acetate Glycol ether propionate, ethylene glycol methyl ether acetate, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, propylene glycol propyl ether acetate, γ-butyrolactone, Ester solvents such as γ-valerolactone; acetonitrile, N-methylpyrrolidone, N-ethylpyrrolidone, N-propylpyrrolidone, N-butylpyrrolidone, N-hexylpyrrolidone, N-cyclohexylpyrrolidone, N, N- Aprotic polar solvents such as dimethylformamide, N, N-dimethylacetamide, dimethylmethane; methylene chloride, chloroform, dichloroethane, benzene, toluene, xylene, hexane , Octane, ethylbenzene, 2-ethylhexanoic acid, methyl isobutyl ketone, methyl ethyl ketone and other hydrophobic organic solvents; methanol, ethanol, n-propanol, 2-propanol, n-butanol, isopropyl alcohol Butanol, 2-butanol, tertiary butanol, n-pentanol, isoamyl alcohol, 2-methylbutanol, 2-pentanol, tertiary pentanol, 3-methoxybutanol, n-hexanol, 2 -Methylpentanol, 2-hexane , 2-ethylbutanol, 2-heptanol, n-octanol, 2-ethylhexanol, 2-octanol, n-nonanol, n-decanol, 2-undecanol, trimethylnonyl Alcohol, 2-tetradecananol, 2-heptadecananol, cyclohexanol, methylcyclohexanol, isobornylcyclohexanol, benzyl alcohol, ethylene glycol, 1,2-propanediol, 1, 3-butanediol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol and other alcohol solvents; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monophenyl ether, diethylene glycol mono Methyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol mono-n-hexyl ether, ethoxytriethylene glycol, tetraethylene glycol mono-n-butyl ether, propylene glycol monomethyl ether, dipropylene glycol Glycol monoether solvents such as monomethyl ether, dipropylene glycol monoethyl ether, and tripropylene glycol monomethyl ether; terpinene, terpineol, myrcene, alloocimene, limonene, dipentene, pinene , Carbon, ocimene, phellandrene And other terpene solvents; water, etc. These liquid media can be used alone or in combination of two or more.

From the viewpoint of imparting properties to a semiconductor substrate and pattern forming properties (inhibiting coarsening of a pattern during the application and drying of a composition for forming a passivation layer), the liquid medium preferably contains a solvent selected from a terpene solvent, At least one of the group consisting of an ester solvent and an alcohol solvent, and more preferably at least one of a terpene solvent.

When the composition for forming a passivation layer contains a liquid medium, the content rate is determined in consideration of the imparting property, the pattern forming property, and the storage stability. For example, from the viewpoints of the imparting properties and pattern forming properties of the composition, the content of the liquid medium in the total mass of the composition for forming a passivation layer is preferably 5 to 98% by mass, and more preferably 10%. Mass% to 95% by mass.

(Resin)

The composition for forming a passivation layer preferably further contains at least one resin. By containing a resin, the shape stability of the composition layer formed by applying the passivation layer-forming composition to a semiconductor substrate is further improved, and it is easier to selectively select a desired shape in a region where the composition layer is formed. A passivation layer is formed.

The type of the resin is not particularly limited, and when the composition for forming a passivation layer is provided on a semiconductor substrate, it is preferable to adjust the viscosity to a range within which a good pattern can be formed. Specific examples of the resin include polyvinyl alcohol, polypropylene amidamine, polyvinyl amidamine, polyvinyl pyrrolidone, polyethylene oxide, polyfluorene, polypropylene amidinyl alkyl, cellulose, and carboxymethyl. Cellulose derivatives such as cellulose, hydroxyethyl cellulose, ethyl cellulose and other cellulose ethers, gelatin and gelatin derivatives, starch and starch Derivatives, Sodium Alginate and Sodium Alginate Derivatives, Xanthan and Sanxanthan Derivatives, Guar Gum and Guar Gum Derivatives, Scleroglucan and Hard Glucose Glycan derivatives, tragacanth gum and tragacanth derivatives, dextrin and dextrin derivatives, (meth) acrylic resins, (meth) acrylate resins (e.g. (meth) Alkyl acrylate resins, dimethylaminoethyl (meth) acrylate resins, etc.), butadiene resins, styrene resins, siloxane resins, copolymers thereof, and the like. These resins can be used alone or in combination of two or more.

Among these resins, from the standpoint of storage stability and pattern formation properties, neutral resins having no acidic and basic functional groups are preferably used, and can be easily adjusted even when the content is small. From the viewpoint of viscosity and thixotropy, cellulose derivatives are more preferably used.

The molecular weight of the resin is not particularly limited, and it is preferably adjusted appropriately in consideration of a required viscosity as a composition for forming a passivation layer. From the viewpoints of storage stability and pattern formation property, the weight average molecular weight of the resin is preferably 1,000 to 10,000,000, and more preferably 3,000 to 5,000,000. The weight-average molecular weight of the resin was calculated from a molecular weight distribution measured by gel permeation chromatography (GPC) using a calibration curve of standard polystyrene. The calibration curve was obtained using a standard polystyrene sample set (PStQuick MP-H, PStQuick B [Tosoh Corporation, trade name]) in a cubic approximation. The measurement conditions of GPC are shown below.

Device: (Pump: L-2130 [Hitachi High-Technologies) Inc.])

(Detector: L-2490 Refractive Index Detector (Refractive Index, RI) [Hitachi High-Technologies Co., Ltd.])

(Column oven: L-2350 [Hitachi High-Technologies Co., Ltd.])

Column: Gelpack GL-R440 + Gelpack GL-R450 + Gelpack GL-R400M (3 in total) (Hitachi Kasei Co., Ltd., trade name)

Column size: 10.7mm (inner diameter) × 300mm

Eluent: Tetrahydrofuran

Sample concentration: 10mg / 2mL

Injection volume: 200 μL

Flow: 2.05mL / min

Measurement temperature: 25 ° C

When the composition for forming a passivation layer contains a resin, the content rate of the resin in the composition for forming a passivation layer may be appropriately selected as needed. For example, the total mass of the composition for forming a passivation layer is preferably 0.1% by mass to 30% by mass. From the viewpoint of showing that the pattern-forming thixotropy is more easily performed, the content ratio is more preferably 1% to 25% by mass, still more preferably 1.5% to 20% by mass, and even more preferably 1.5% by mass. ~ 10% by mass.

When the composition for forming a passivation layer contains a resin, the content ratio of the said organoaluminum compound and the said resin in the said composition for passivation layer formation can be suitably selected as needed. Among them, from the viewpoint of pattern formability and storage stability, When the total amount of one or more selected from the group consisting of alumina and its precursors, which is contained in the specific metal compound and if necessary, is set to 1, the ratio of the resin is preferably 0.001 to 1,000, more preferably It is 0.01 to 100, and more preferably 0.1 to 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 rate of the acidic compound or the basic compound in the composition for forming a passivation layer is preferably 1 respectively. Mass% or less, more preferably 0.1 mass% or less.

Examples of the acidic compound include Bronsted acid and Lewis acid. Specific examples include inorganic acids such as hydrochloric acid and nitric acid; organic acids such as acetic acid and the like. Examples of the basic compound include a Brnister base and a Lewis base. Specific examples include inorganic bases such as alkali metal hydroxides and alkaline earth metal hydroxides; organic bases such as trialkylamine and pyridine.

The composition for forming a passivation layer may contain various additives, such as a thickener, a wetting agent, a surfactant, an inorganic powder, a resin containing a silicon atom, and a thixotropic agent, as other components as needed.

Examples of the inorganic powder include silicon dioxide (silicon oxide), clay, silicon carbide, silicon nitride, montmorillonite, bentonite, and carbon black. Among these inorganic powders, a filler containing silicon dioxide as a component is preferably used. Here, the so-called clay refers to layered clay minerals, and specific examples thereof include kaolinite, imogolite, montmorillonite, smectite, sericite, and illite. ), Talc, stevensite, zeolite, etc. When the composition for forming a passivation layer contains an inorganic powder, The imparting property of the composition for forming a passivation layer tends to improve.

Examples of the surfactant include nonionic surfactants, cationic surfactants, and anionic surfactants. Among these, a non-ionic surfactant or a cationic surfactant is preferred in terms of less impurities such as heavy metals introduced into the semiconductor element. Examples of the nonionic surfactant include a silicon-based surfactant, a fluorine-based surfactant, and a hydrocarbon-based surfactant. When the composition for forming a passivation layer contains a surfactant, the thickness of the composition layer formed from the composition for forming a passivation layer and the uniformity of the composition tend to be improved.

Examples of the resin containing a silicon atom include modified amino acids at both ends, polyamine-silicone alternating copolymer, side chain alkyl modified silicone, side chain polyether modified silicone, and terminal alkyl modified silicone. Modified silicone, silicone modified polyglucose, silicone modified acrylic resin, etc. When the composition for forming a passivation layer contains a silicon-containing resin, the thickness of the composition layer formed from the composition for forming a passivation layer and the uniformity of the composition tend to be improved.

Examples of the thixotropic agent include polyether compounds, fatty acid ammonium, fumed silica, hydrogenated castor oil, urethane amidoamine, polyvinylpyrrolidone, and oil-based gelling agents. When the composition for forming a passivation layer contains a thixotropic agent, the pattern forming property tends to be improved when the composition for forming a passivation layer is provided. Examples of the polyether compound include polyethylene glycol, polypropylene glycol, and a poly (ethylene-propylene) glycol copolymer.

The viscosity of the composition for forming a passivation layer is not particularly limited, and can be appropriately selected depending on a method of applying the semiconductor substrate and the like. For example, the viscosity of the composition for forming a passivation layer can be set to 0.01 Pa. s ~ 10000Pa. 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 ~ 1000Pa. s. The viscosity is a value obtained by measuring at 25 ° C. using a rotary shear viscosity meter at a shear rate of 1.0 s ^-1 .

The composition for forming a passivation layer is preferably thixotropic. In particular, when the composition for forming a passivation layer contains a resin, it is preferable to divide the shear viscosity η ₁ at a shear rate of 1.0s ^-1 by a shear rate of 10s ^-1 from the viewpoint of pattern formation. The thixotropic ratio (η ₁ / η ₂ ) calculated from the shear viscosity η ₂ is 1.05 to 100, and more preferably 1.1 to 50. The shear viscosity was measured at 25 ° C. using a rotary shear viscosity meter equipped with a cone plate (50 mm in diameter and 1 ° cone angle).

The manufacturing method of the composition for passivation layer formation is not specifically limited. For example, it can be manufactured by mixing a specific metal compound with a liquid medium or the like which is contained as necessary, by a commonly used method. It can also be produced by mixing a liquid medium in which a resin is dissolved with a specific metal compound.

Furthermore, the specific metal compound may be prepared by mixing a compound of the formula (I) with a compound that can form a chelate compound with a metal element contained in the compound of the formula (I). In this case, a solvent may be appropriately used, and a heat treatment may be performed. The composition for forming a passivation layer can also be manufactured using the specific metal compound prepared in this way.

In addition, the components contained in the composition for forming a passivation layer and the content of each component can be measured by thermal analysis such as differential gravimetric-differential thermal analysis (TG / DTA) and nuclear magnetic resonance (Nuclear Magnetic Resonance). (NMR), Infrared spectroscopy (IR) and other spectral analysis, High Performance Liquid Chromatography (High Performance Liquid Chromatography (HPLC), Gel Permeation Chromatography (GPC) and other chromatographic analysis.

<Manufacturing method of solar cell element>

The method for manufacturing a solar cell element of the present invention includes the steps of forming a first impurity diffusion region on a part of the light receiving surface of a semiconductor substrate having a light receiving surface and a back surface opposite to the light receiving surface; and A step of forming a second impurity diffusion region having a lower impurity concentration than the first impurity diffusion region; a step of forming a light-receiving surface electrode on at least a portion of the first impurity diffusion region; a step of forming a back electrode on the back surface; The step of forming a composition layer for forming a passivation layer on at least one of the groups consisting of the light-receiving surface and the back surface, wherein the composition for forming a passivation layer contains a compound selected from a specific metal oxide and a general formula. At least one of the group consisting of the compound represented by (I); and a step of heat-treating the composition layer to form a passivation layer containing at least one specific metal oxide. The method for manufacturing a solar cell element of the present invention may further include other steps as necessary.

According to the above method, a passivation layer having an excellent passivation effect can be formed on a semiconductor substrate. Furthermore, the passivation layer can be formed by a simple and highly productive method that does not require a vapor deposition device or the like.

Having an impurity diffusion region (p-type diffusion region or n-type diffusion region) The semiconductor substrate can be manufactured by a method generally used. For example, it can manufacture according to the method described in Japanese Patent No. 3522940. As a method of forming a light-receiving surface electrode on at least a part of the first impurity diffusion region, for example, forming the light-receiving surface electrode by applying a paste for electrode formation such as silver paste or aluminum paste to a desired region of the light-receiving surface of the semiconductor substrate. Heat treatment as required. The step of forming the electrode may be performed before the step of forming the passivation layer, or may be performed after the step of forming the passivation layer.

The method of forming a composition layer by providing a composition for forming a passivation layer containing a specific metal compound on at least one surface selected from the group consisting of a light receiving surface and a back surface of a semiconductor substrate is not particularly limited. Specific examples include a printing method such as a dipping method, 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 inkjet method. Among these methods, a printing method and an inkjet method are preferred from the viewpoint of pattern formation, and a screen printing method is more preferred.

The application amount of the composition for forming a passivation layer to a semiconductor substrate can be appropriately selected according to the purpose. For example, it can adjust appropriately so that the thickness of the passivation layer formed may become a desired thickness.

The composition layer formed by applying the composition for forming a passivation layer to a semiconductor substrate is heat-treated to form a heat-treated product layer derived from the composition layer, thereby forming a passivation layer on the semiconductor substrate.

The heat treatment conditions of the composition layer are not particularly limited as long as they are conditions for forming a passivation layer containing a specific metal oxide. In the case where the composition for forming a passivation layer contains a precursor of a specific oxide, the conditions for converting the precursor of the specific oxide to a specific metal oxide as a heat-treated product thereof are not particularly limited. system. Among them, firing conditions that can form an amorphous specific metal oxide layer having no crystal structure are preferred. By forming the passivation layer with an amorphous specific metal oxide, the passivation layer of the semiconductor substrate can more effectively have a negative charge, and a more excellent passivation effect can be obtained. Specifically, the heat treatment temperature is preferably 400 ° C or higher, more preferably 400 ° C to 900 ° C, and even more preferably 600 ° C to 800 ° C. The heat treatment time can be appropriately selected depending on the heat treatment temperature and the like. For example, it can be set to 5 seconds to 10 hours, preferably 10 seconds to 5 hours.

The density of the passivation layer is preferably 1.0 g / cm ³ to 10.0 g / cm ³ , more preferably 2.0 g / cm ³ to 8.0 g / cm ³ , and even more preferably 3.0 g / cm ³ to 7.0 g / cm ³ . When the density of the passivation layer is 1.0 g / cm ³ to 10.0 g / cm ³ , a sufficient passivation effect can be obtained. In addition, the high passivation effect tends to be difficult to change with time. It can be presumed that if the density of the passivation layer is 1.0 g / cm ³ or more, external moisture and impurity gases cannot easily reach the interface between the semiconductor substrate and the passivation layer, so it is easy to maintain the passivation effect; / cm ³ or less, the interaction with the semiconductor substrate tends to increase. The method of measuring the density of the passivation layer includes: a method of measuring the mass and volume of the passivation layer to calculate the density; the X-ray reflectance method is used to make X-rays incident on the sample surface at a very shallow angle, The method of determining the film thickness and density of a sample by measuring the X-ray intensity distribution reflected in the specular direction and comparing the distribution obtained by the measurement with the simulation result to optimize the simulation parameters.

The average thickness of the passivation layer is preferably 5 nm to 50 μm, more preferably 20 nm to 20 μm, and even more preferably 30 nm to 5 μm. If the average thickness of the passivation layer is 5 nm or more, it is easy to obtain a sufficient passivation effect, and if it is 50 μm or less, it may be considered. Considering the tendency of other components constituting the solar cell element to design the element structure.

The average thickness of the passivation layer is set to an arithmetic mean value of the thickness of five points measured using an interference film thickness meter.

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view showing a step chart schematically showing an example of a method for manufacturing a solar cell element according to this embodiment. However, this step diagram does not limit the invention in any way.

An example when a p-type semiconductor substrate is used as a semiconductor substrate will be described using FIG. 1. First, it is preferable to clean the p-type semiconductor substrate 10 with an alkaline aqueous solution. By washing with an alkaline aqueous solution, organic substances, particles, and the like existing on the surface of the semiconductor substrate can be removed, and the passivation effect can be further improved. Examples of the cleaning method using an alkaline aqueous solution include RCA (Radio Corporation of America) cleaning, which is generally known. For example, a semiconductor substrate can be immersed in a mixed solution of ammonia water and hydrogen peroxide water and processed at 60 ° C to 80 ° C to remove organic matter and particles. The processing time is preferably 10 seconds to 10 minutes, and more preferably 30 seconds to 5 minutes.

Next, as shown in FIG. 1 (a), a texture structure (pyramid shape) for suppressing reflection of sunlight is formed on the light receiving surface of the p-type semiconductor substrate 10 by alkali etching or the like. Thereafter, as shown in FIG. 1 (b), a composition 11 is provided on a part of the light-receiving surface to form an n-type diffusion region, and as shown in FIG. 1 (c), impurities are diffused into the semiconductor substrate by heat treatment. Forming a first impurity diffusion region Domain (first n-type diffusion region 13). As the n-type diffusion region forming composition 11, for example, a composition containing phosphorus or ammonia can be used. The temperature of the heat treatment is preferably set to 800 ° C to 1000 ° C.

The n-type diffusion region forming composition may be, for example, those described in Japanese Patent Application Laid-Open No. 2012-084830.

Next, as shown in FIG. 1 (d), a phosphorous silicate glass (PSG) layer 14 is formed using phosphorus oxychloride or the like, and heat treatment is performed to form a second one as shown in FIG. 1 (e). Impurity diffusion region (second n-type diffusion region 15). Thereafter, as shown in FIG. 1 (f), the semiconductor substrate is immersed in an etching solution such as hydrofluoric acid, thereby removing the PSG layer 14 and the calcined product 12 of the n-type diffusion region forming composition.

Then, as shown in FIG. 1 (g), a p-type diffusion region forming composition 16 is provided on the back surface of the p-type semiconductor substrate 10. At this time, the p-type diffusion region forming composition may be applied to a part of the back surface of the p-type semiconductor substrate 10 or may be applied to the entire surface. As the p-type diffusion region forming composition, for example, a composition containing boron or the like can be used. Then, as shown in FIG. 1 (h), the impurity is diffused by the heat treatment to form a p ⁺ -type diffusion region 17. The temperature of the heat treatment is preferably set to 800 ° C to 1050 ° C.

As the p-type diffusion region forming composition, for example, those described in Japanese Patent Application Laid-Open No. 2011-005312 can be used.

Next, as shown in FIG. 1 (i), the semiconductor substrate is immersed in an etching solution such as hydrofluoric acid, thereby removing the calcined product 16 'of the p-type diffusion region forming composition.

Then, as shown in (j) of FIG. An anti-reflection film 18 is formed on the light surface. Examples of the antireflection film 18 include a silicon nitride film and a titanium oxide film. A surface protection film (not shown) such as silicon oxide may be further provided between the antireflection film 18 and the p-type semiconductor substrate 10. Alternatively, a passivation layer may be used as the surface protection film.

Next, as shown in FIG. 1 (k), a passivation layer-forming composition containing a specific metal compound is provided on a part of the back surface of the p-type semiconductor substrate 10 to form a composition layer, and the composition layer is heat-treated to Forming a passivation layer 19. The method for imparting a composition for forming a passivation layer is not particularly limited. Examples thereof include printing methods such as a dipping method, screen printing, a spin coating method, a brush coating method, a spray method, a doctor blade method, a roll coating method, and an inkjet method. Among these methods, a printing method and an inkjet method are preferred from the viewpoint of pattern formation, and a screen printing method is more preferred.

The amount of the composition for forming the passivation layer can be appropriately selected depending on the purpose. For example, the amount of the composition for forming a passivation layer can be appropriately adjusted so that the thickness of the formed passivation layer 19 becomes the above-mentioned preferred thickness. The conditions for the heat treatment of the composition layer can be appropriately selected according to the above conditions. By forming the passivation layer 19 on the back surface of the semiconductor substrate, a solar cell element having excellent power generation efficiency can be manufactured.

Thereafter, as shown in FIG. 1 (1), a paste for electrode formation is applied to the light-receiving surface and the back surface side of the p-type semiconductor substrate 10, and heat treatment is performed to form the light-receiving surface electrode 20 and Back electrode 21. By using a glass powder having a burn-through property as the light-receiving surface electrode forming paste, as shown in (m) of FIG. 1, the light-receiving surface that is in contact with the surface of the p-type semiconductor substrate 10 can be formed through the antireflection film 18 The electrode 20 obtains ohmic contact. As described above, a solar cell element can be obtained. A region where the passivation layer 19 and the back electrode 21 overlap may exist as shown in FIG. 1 (m).

The solar cell element manufactured by the method including the steps shown in FIG. 1 can set the back electrode made of aluminum or the like into a point contact structure (for example, the electrode configuration shown in FIG. 2), thereby reducing the warpage of the substrate and the like. Furthermore, the passivation layer can be formed with excellent productivity by applying a composition for forming a passivation layer to a desired region on the surface of the semiconductor substrate and performing heat treatment.

The solar cell element of the present invention can also be manufactured using an n-type semiconductor substrate. Specifically, the solar cell element can be manufactured by: in the manufacturing steps shown in FIG. 1, the p-type semiconductor substrate 10 is replaced with an n-type semiconductor substrate, and the n-type diffusion region forming composition 11 is replaced with p The type-type diffusion region forming composition is replaced with the calcined product 12 of the n-type diffusion region forming composition and the p-type diffusion region forming composition is calcined. The first n-type diffusion region 13 is replaced with the first p-type diffusion region. Replace the second n-type diffusion region 15 with a second p-type diffusion region, replace the p-type diffusion region-forming composition 16 with an n-type diffusion region-forming composition, and replace the calcined product 16 'of the p-type diffusion region-forming composition with The n-type diffusion region forms a calcined product of the composition. The p ⁺ -type diffusion region 17 is replaced with an n ⁺ -type diffusion region, and the PSG (phosphosilicate glass) layer 14 is replaced with borosilicate glass (BSG). Floor.

FIG. 2 is a plan view schematically showing an example of the arrangement of the back electrode 21 of the semiconductor substrate on which the back electrode 21 is formed. In FIG. 2, a plurality of rectangular back electrodes 21 are arranged on the back surface of the p-type semiconductor substrate 10 while being separated from each other.

FIG. 3 is a plan view schematically showing another example of the arrangement of the back electrode of the semiconductor substrate on which the back electrode 21 is formed. In FIG. 3, two rectangular back electrodes 21 are arranged on the back of the p-type semiconductor substrate 10 so that their respective long sides are parallel. on. The arrangement of the back electrode 21 of the present invention may be the embodiment shown in FIG. 2 or the embodiment shown in FIG. 3, or may be another embodiment that can achieve the effect of the present invention.

FIG. 4 is a plan view schematically showing an example of the arrangement of the light-receiving surface electrodes of the p-type semiconductor substrate 10 on which the light-receiving surface electrodes 20 are formed. For example, as shown in FIG. 4, a light-receiving surface bus bar electrode 50 and a light-receiving surface finger electrode 51 may be formed as the light-receiving surface electrode 20. In FIG. 4, L2 represents the length of one side of the semiconductor substrate, L8 represents the width of the light-receiving surface bus bar electrode 50, and L9 represents the width of the light-receiving surface finger electrode 51. The width L8 of the light-receiving surface bus bar electrode 50 is preferably 500 μm to 3 mm, and the width L9 of the light-receiving surface finger electrode 51 is preferably 10 μm to 400 μm.

FIG. 5 is an example of a plan view of a back surface of a semiconductor substrate on which a back electrode 21 and a passivation layer 19 are formed on a p-type semiconductor substrate 10. In FIG. 5, a plurality of rectangular back electrodes 21 are arranged apart from each other, and a passivation layer 19 is formed in a region other than the back electrodes 21. In FIG. 5, L1 indicates the length of one side of the region where the passivation layer 19 is formed, and L2 indicates the length of one side of the p-type semiconductor substrate 10. L3 and L4 each indicate the length of one side of the rectangular back electrode 21. L3 and L4 are each preferably 10 μm to 156 mm.

FIG. 6 is another example of a plan view of a back surface of a semiconductor substrate in which a back electrode 21 and a passivation layer 19 are formed on a p-type semiconductor substrate 10. In FIG. 6, two rectangular back electrodes 21 are arranged so that their long sides are parallel, and a passivation layer 19 is formed in a region other than the back electrodes 21. In FIG. 6, L1 represents the length of one side of the region where the passivation layer 19 is formed, and L2 represents one side of the p-type semiconductor substrate 10. length. L5 indicates the length of the short side of the rectangular back electrode 21. L5 is preferably 50 μm to 10 mm.

The length L2 of one side of the p-type semiconductor substrate 10 is preferably 125 mm to 156 mm. The length L1 of one side of the region where the passivation layer 19 is formed is preferably 100 μm to 156 mm.

<Solar Cell Module>

A solar cell module of the present invention includes the solar cell element of the present invention and a wiring material disposed on an electrode of the solar cell element. The solar cell module may include a plurality of solar cell elements connected via a wiring material, or may be sealed with a sealing material. The wiring material and the sealing material are not particularly limited, and may be appropriately selected from materials generally used in this technical field. The size of the solar cell module is not particularly limited, and it can be set to, for example, 0.5 m ² to 3 m ² .

[Example]

Hereinafter, the present invention will be specifically described by examples, but the present invention is not limited to these examples.

<Example 1>

(Preparation of composition for forming passivation layer)

Al ₂ O ₃ thin film coating material (High Purity Chemical Research Institute Co., Ltd., SYM-A104, Al ₂ O ₃ : 2% by mass, xylene: 87% by mass, 2-propanol: 5% by mass, stabilizer : 6% by mass) 1.0 g, Nb ₂ O ₅ thin film coating material (High Purity Chemical Research Institute Co., Ltd., Nb-05, Nb ₂ O ₅ : 5% by mass, n-butyl acetate: 56% by mass, stabilizer : 16.5 mass%, viscosity modifier: 22.5 mass%) 1.0 g were 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 Sumitomo Corporation (SUMCO) Co., Ltd., 50 mm square, thickness: 625 μm) having a mirror-shaped surface was used. The silicon substrate was immersed in a RCA cleaning solution (Kanto Chemical Co., Ltd., Frontier Cleaner-A01) at 70 ° C. for 5 minutes and cleaned to perform a pretreatment.

Thereafter, using the spin coater (Mikasa Co., Ltd., MS-100), the composition 1 for passivation layer formation obtained above was applied to the pretreated silicon substrate at 4000 rpm (min ^-1 ) for 30 seconds. One side of the entire surface. Then, it dried at 150 degreeC for 3 minutes. Then, it was calcined in air at 700 ° C for 10 minutes, and then left to cool at room temperature (25 ° C) to produce a substrate for evaluation having a passivation layer.

(Measurement of effective life)

A service life measuring device (Semilab Japan Co., Ltd., WT-2000PVN) measures the area of the passivation layer formed on the substrate for evaluation obtained by the reflected microwave photoconductive attenuation method at room temperature. Effective life (μs). The effective life is 480 μs.

(Measurement of average thickness)

The thickness of the passivation layer was measured at five points in the plane using an interference film thickness meter (Filmetrics Co., Ltd., F20 film thickness measurement system), and the average value was calculated. The average was 82 nm.

(Determination of density)

The density is calculated from the mass and average thickness of the passivation layer. The density was 3.2 g / cm ³ .

(Preparation of n-type diffusion region forming composition)

A mixture of SiO ₂ (Wako Pure Chemical Industries, Ltd.), P ₂ O ₅ (Wako Pure Chemical Industries, Ltd.) and CaCO ₃ (Wako Pure Chemical Industries, Ltd.) (molar ratio is SiO ₂ : P ₂ O ₅ : CaCO ₃ = 30: 60: 10) was put into an alumina crucible, and the temperature was raised from room temperature (25 ° C.) to 400 ° C./h to 1400 ° C., and then kept for 1 hour. Then, it was rapidly cooled by flowing to a glassy carbon plate at room temperature (25 ° C) to obtain a P ₂ O ₅ -SiO ₂ -CaO-based glass. The obtained glass was pulverized using an automatic mortar kneading device, and glass particles containing P (phosphorus) as a donor element were obtained in a powder state.

The particle shape of the obtained glass particles was approximately spherical, and the volume average particle diameter measured by a laser diffraction type particle size distribution measurement device was 8 μm. Here, the volume average particle diameter is a relationship between the intensity of scattered light and the angle of the laser light irradiated to the glass particles, and is calculated based on the Mie scattering theory. Specifically, a sample obtained by dispersing 0.1 g of glass particles in 10 g of terpineol (Nippon Terpene Chemical Co., Ltd., terpineol-LW) was used as a measurement sample.

Next, a solution containing 6.0% of terpineol (Nippon Terpene Chemical Co., Ltd., Terpineol-LW) of ethyl cellulose (The Dow Chemical Company, STD200) was prepared. 9 g of this solution was mixed with 1 g of the glass powder obtained as a donor element-containing compound in a mortar to prepare an n-type diffusion region forming composition.

(Fabrication of solar cell elements)

Using the mask of the pattern shown in FIG. 7, the n-type diffusion region forming composition was imparted to a 156 mm square p-type silicon substrate by screen printing (Advantec Co., Ltd., substrate resistivity: 2 Ω.cm, thickness: 200 μm), and dried on a hot plate at 150 ° C. for 1 minute. Thereafter, the p-type silicon substrate was placed on a quartz boat and placed in a diffusion furnace (Koyo Thermal Systems Co., Ltd., 206A-M100) at 700 ° C. Then, the temperature was increased to 850 ° C. and held for 30 minutes to form a first impurity diffusion region (first n-type diffusion region). Thereafter, the temperature was lowered to 820 ° C., and a second impurity diffusion region (second n-type diffusion region) was formed by processing with POCl ₃ gas. Specifically, after being held at 820 ° C for 5 minutes, the POCl ₃ gas was circulated for 10 minutes, and then the POCl ₃ gas was stopped, and then the phosphorus was diffused by drive-in for 10 minutes to form a second n-type diffusion. region. Then, the temperature was lowered to 700 ° C, and the temperature was maintained at 700 ° C for 1 hour. Thereafter, the quartz boat and the silicon substrate were taken out.

Then, an inkjet device (Microjet Co., Ltd., MJP-1500V, inkjet head: IJH-80, nozzle size: 50 μm × 70 μm) was used to form the composition layer into the passivation layer 19 shown in FIG. 5. In the form of a pattern, the composition 1 for forming a semiconductor substrate passivation layer obtained as described above is provided on the back surface of a p-type silicon substrate. Specifically, a screen mask plate for forming a back surface electrode having a square-shaped opening portion 60 and a non-opening portion 61 having a square shape of 8 mm × 8 mm as shown in FIG. 8 is used in an opposite opening pattern (the opening portion in FIG. 8). 60 is a non-opening portion, and non-opening portion 61 is an opening portion). The screen printing composition 1 for forming a passivation layer of a semiconductor substrate is screen-printed so that the film thickness after drying becomes 5 μm, which is performed at 150 ° C. Dry for 3 minutes. Then, it was heat-treated at 550 ° C for 1 hour, and left to cool to room temperature (25 ° C). until. In this manner, a passivation layer is formed in a region other than the region where the back electrode is to be formed.

Next, a screen printing aluminum electrode paste (PVG Solutions (PVG Solutions) Co., Ltd., PVG-AD- 02), and dried at 150 ° C for 3 minutes. Then, as shown in FIG. 7, a screen mask for forming a light-receiving surface electrode having an opening portion having a bus bar width of 1.5 mm and a finger width of 150 μm as shown in FIG. 7 was used, and a screen printing silver electrode paste (DuPont ( Dupont) Co., Ltd., PV159A), was dried at 150 ° C for 3 minutes. Thereafter, a tunnel-type calcining furnace (Noritake Co., Ltd.) was used to perform heat treatment at 820 ° C. for a takt time of 10 seconds to form a light-receiving surface electrode and a back surface electrode. In this way, a solar cell element was produced.

Immediately after the production of the solar cell element (1 hour later), a solar cell element solar simulator (Wacom Electric Co., Ltd., XS-155S-10) was used to evaluate the power generation characteristics.

The evaluation was performed by simulating sunlight (device name: WXS-155S-10, Wacom Electric Co., Ltd.) and a voltage-current (IV) evaluation measuring device (device name: IV curve plotter (IV CURVE TRACER) MP-160 (Inho Seiki Co., Ltd.) is used in combination. Jsc (short-circuit current density), Voc (open-circuit voltage), FF (fill factor), and Eff1 (conversion efficiency) of the solar cell's power generation performance are based on Japanese Industrial Standards (JIS)- C-8913 (2005) and JIS-C-8914 (2005).

The results are shown in Table 2. The evaluation was performed by covering the mask so that the light receiving area became 125 mm × 125 mm. The produced solar cell element was placed in a constant temperature and humidity tank at 50 ° C. and 80% RH, and the power generation characteristics after one month of storage were evaluated. The results are shown in Table 3. The conversion efficiency of the solar cell element after storage was 98.7% of the conversion efficiency Eff2 before storage, and the conversion efficiency was reduced by 1.3%.

<Example 2>

(Preparation of composition for forming passivation layer)

Ta ₂ O ₅ film coating material (High Purity Chemical Research Institute Co., Ltd., 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) as the composition 2 for forming a passivation layer.

A passivation layer was formed on a pre-processed silicon substrate in the same manner as in Example 1 except that the composition 2 for forming a passivation layer was used to prepare a substrate for evaluation, and evaluation was performed in the same manner as in Example 1. The effective life is 450 μs. The average thickness and density of the passivation layer were 75 nm and 3.6 g / cm ³ , respectively.

A solar cell element was produced in the same manner as in Example 1 except that the composition 2 for forming a passivation layer was used instead of the composition 1 for forming a passivation layer, and the power generation characteristics were evaluated. The results are shown in Tables 2 and 3. The conversion efficiency of solar cell elements after storage was 98.7% of the conversion efficiency before storage, and the conversion efficiency was reduced by 1.3%.

<Example 3>

HfO ₂ film coating material (High Purity Chemical Research Institute Co., Ltd., Hf-05, HfO ₂ : 5 mass%, isoamyl acetate: 73 mass%, n-octane: 10 mass%, 2-propanol: 5 mass%, stabilizer: 7 mass%) as the composition 3 for forming a passivation layer.

A passivation layer was formed on a pre-processed silicon substrate in the same manner as in Example 1 except that the prepared composition 3 for forming a passivation layer was used to prepare a substrate for evaluation, and evaluation was performed in the same manner as in Example 1. The effective life is 380μs. The average thickness and density of the passivation layer were 71 nm and 3.2 g / cm ³ , respectively.

A solar cell element was produced in the same manner as in Example 1 except that the composition 3 for forming a passivation layer was used instead of the composition 1 for forming a passivation layer, and the power generation characteristics were evaluated. The results are shown in Tables 2 and 3. The conversion efficiency of the solar cell element after storage was 98.4% of the conversion efficiency before storage, and the conversion efficiency was reduced by 1.6%.

<Example 4>

Y ₂ O ₃ film coating material (High Purity Chemical Research Institute Co., Ltd., 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, terpene oil: 45% by mass, viscosity modifier: 9% by mass) as composition 4 for forming a passivation layer.

A passivation layer was formed on the pre-processed silicon substrate in the same manner as in Example 1 except that the composition 4 for forming a passivation layer prepared as described above was used to prepare a substrate for evaluation, and evaluation was performed in the same manner as in Example 1. The effective life is 390 μs. The average thickness and density of the passivation layer were 68 nm and 2.8 g / cm ³ , respectively.

A solar cell element was produced in the same manner as in Example 1 except that the composition 4 for forming a passivation layer was used instead of the composition 1 for forming a passivation layer, and the power generation characteristics were evaluated. The results are shown in Tables 2 and 3. The conversion efficiency of the solar cell element after storage was 98.3% of the conversion efficiency before storage, and the conversion efficiency was decreased by 1.7%.

<Example 5>

Aluminium diisopropanolacetate (Chuanken Refining Co., Ltd., ALCH), niobium pentaethoxylate (Beixing Chemical Industry Co., Ltd.), acetone (Wako Pure Chemical Industries, Ltd.) Xylene (Wako Pure Chemical Industries, Ltd.), 2-propanol (Wako Pure Chemical Industries, Ltd.), and terpineol (Japan Terpene Chemical Co., Ltd.) are mixed in a ratio shown in Table 1, Used as a composition 5 for forming a passivation layer.

A passivation layer was formed on the pre-processed silicon substrate in the same manner as in Example 1 except that the prepared composition 5 for forming a passivation layer was used to prepare a substrate for evaluation, and evaluation was performed in the same manner as in Example 1. The effective life is 420 μs. The average thickness and density of the passivation layer were 94 nm and 2.6 g / cm ³ , respectively.

A solar cell element was produced in the same manner as in Example 1 except that the composition 5 for forming a passivation layer was used instead of the composition 1 for forming a passivation layer, and the power generation characteristics were evaluated. The results are shown in Tables 2 and 3. The conversion efficiency of the solar cell element after storage was 97.9% of the conversion efficiency before storage, and the conversion efficiency was reduced by 2.1%.

<Example 6>

In Example 1, instead of using a screen printing method to form an aluminum electrode, an aluminum vapor deposition machine (sanyu-electron Co., Ltd., SVC-700TM) was used to vapor-deposit an entire pattern of 125 mm × 125 mm. A substrate for evaluation and a solar cell element were produced in the same manner as in Example 1 except that aluminum was used to form a back electrode. Aluminum vapor deposition was started after the degree of vacuum became 10 ^-4 Pa or less. The distance between the substrate and the vapor deposition source was set to 70 mm, and processing was performed for 5 minutes.

The passivation layer is formed before the aluminum vapor deposition in a region other than a region where a back electrode of 125 mm × 125 mm is formed.

The effective life of the substrate for evaluation was measured and evaluated in the same manner as in Example 1. As a result, it was 110 μs. The evaluation results of the power generation characteristics of the solar cell element are shown in Tables 2 and 3. The conversion efficiency of the solar cell element after storage was 99.4% of the conversion efficiency before storage, and the conversion efficiency was reduced by 0.6%.

<Comparative example 1>

Except that the composition 1 for forming a passivation layer was not provided in Example 1, a substrate for evaluation was produced in the same manner as in Example 1, and evaluation was performed in the same manner as in Example 1. The effective life is 20 μs.

Except that the composition 1 for forming a passivation layer was not provided in Example 1, a solar cell element was produced in the same manner as in Example 1, and the power generation characteristics were evaluated. The results are shown in Tables 2 and 3. The conversion efficiency of the solar cell element after storage was 93.0% of the conversion efficiency before storage, and the conversion efficiency was reduced by 7.0%.

<Comparative example 2>

6.0 g of ethyl cellulose (The Dow Chemical, STD200) and 34.0 g of terpineol (Terpine Chemical Co., Ltd., Terpineol-LW) were mixed, and dissolved at 150 ° C for 2 hours to prepare 15 masses. Parts of ethyl cellulose / terpineol solution. Next, 2.00 g of Al ₂ O ₃ particles (High Purity Chemical Research Institute Co., Ltd., with an average particle diameter of 1 μm), 3.9 g of terpineol and 15 parts by mass of the ethyl cellulose / terpineol solution prepared above were prepared. 4.1 g were mixed to prepare composition C2.

A passivation layer was formed on the pretreated silicon substrate in the same manner as in Example 1 except that the composition C2 prepared as described above was used to prepare a substrate for evaluation, and evaluation was performed in the same manner as in Example 1. The effective life is 21 μs. The average thickness and density of the passivation layer were 2.1 μm and 1.4 g / cm ³ , respectively.

The average thickness of the passivation layer was measured using a stylus-type step meter (Ambios, XP-2). Specifically, a part of the passivation layer was removed by using a spatula, and the step difference between the remaining portion of the passivation layer and the cut 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 film thickness.

A solar cell element was produced in the same manner as in Example 1 except that the composition C2 prepared above was used instead of the composition 1 for forming a passivation layer, and the power generation characteristics were evaluated. The results are shown in Tables 2 and 3. The conversion efficiency of the solar cell element after storage was 92.1% of the conversion efficiency before storage, and the conversion efficiency was reduced by 7.9%.

<Comparative example 3>

2.01 g of tetraethoxysilane, 15 parts by mass of the ethyl cellulose / terpineol solution 4.02 g and terpineol 3.97 g prepared above were mixed to prepare a colorless and transparent composition C3.

A passivation layer was formed on the pretreated silicon substrate in the same manner as in Example 1 except that the composition C3 prepared as described above was used to prepare a substrate for evaluation, and evaluation was performed in the same manner as in Example 1. The effective life is 23 μs. The average thickness and density of the passivation layer were 85 nm and 2.1 g / cm ³ , respectively.

A solar cell element was produced and evaluated in the same manner as in Example 1 except that the composition C3 prepared above was used instead of the composition 1 for forming a passivation layer. Power generation characteristics. The results are shown in Tables 2 and 3. The conversion efficiency of the solar cell element after storage was 93.3% of the conversion efficiency before storage, and the conversion efficiency was decreased by 6.7%.

From the above, it is understood that the solar cell element of the present invention contains a passivation layer having an excellent passivation effect, and therefore 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 into a desired shape by a simple process.

<Reference Embodiment 1>

The following is the passivation film, coating material, solar cell element, and silicon substrate with a passivation film of Reference Embodiment 1.

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

<2> The passivation film according to <1>, wherein a mass ratio (niobium oxide / alumina) of the niobium oxide to the alumina 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 alumina is 90% by mass or more.

<4> The passivation film according to any one of <1> to <3>, further comprising 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 alumina precursor and a niobium oxide precursor.

<6> A coating material containing an alumina precursor and a niobium oxide precursor for forming a passivation film for a solar cell element having a silicon substrate.

<7> A solar cell element comprising: a p-type silicon substrate including monocrystalline or polycrystalline silicon 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 of the silicon substrate The first electrode is formed on the surface of the n-type impurity diffusion layer on the light-receiving surface side of the silicon substrate; the passivation film is formed on the surface on the back side of the silicon substrate, has a plurality of openings, and contains oxidation Aluminum and niobium oxide; and a second electrode that is electrically connected to a surface of the back surface side of the silicon substrate through the plurality of openings.

<8> A solar cell element comprising: a p-type silicon substrate including monocrystalline or polycrystalline silicon 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 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; The p-type impurity diffusion layer is formed on a part or all of the back surface side of the silicon substrate, and impurities are added at a higher concentration than the silicon substrate. A passivation film is formed on the surface of the back surface side of the silicon substrate. Openings containing alumina and niobium oxide; and a second electrode electrically connected to the surface of the p-type impurity diffusion layer on the back side of the silicon substrate via the plurality of openings.

<9> A solar cell element comprising: an n-type silicon substrate including monocrystalline or polycrystalline silicon 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 of the silicon substrate A second electrode formed on the back surface side of the silicon substrate; a passivation film formed on the light-receiving surface side surface of the silicon substrate, having a plurality of openings, and containing alumina and niobium oxide; and a first electrode, It is formed on the surface of the p-type impurity diffusion layer on the light receiving surface side of the silicon substrate, and is electrically connected to the surface on the light receiving surface side of the silicon substrate through the plurality of openings.

<10> The solar cell element according to any one of <7> to <9>, wherein a mass ratio of niobium oxide to alumina (niobium oxide / alumina) 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 alumina in the passivation film is 90% by mass or more.

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

According to the above-mentioned reference embodiment, a passivation film having a negative fixed charge and extending the carrier life of a silicon substrate can be realized at a low cost. In addition, a coating-type material can be provided to realize the formation of the passivation film. In addition, a highly efficient solar cell element using the passivation film can be realized at a low cost. In addition, it is possible to realize a silicon substrate with a passivation film that has a negative fixed charge and has an extended carrier life at a low cost.

The passivation film of this embodiment is a passivation film used in a silicon solar cell element, and contains aluminum oxide and niobium oxide.

In addition, in this embodiment, the amount of fixed charges possessed by the film can be controlled by changing the composition of the passivation film.

From the viewpoint of stabilizing the negative fixed charge, the mass ratio of niobium oxide to alumina is more preferably 30/70 to 80/20. From the viewpoint of making the negative fixed charge more stable, the mass ratio of niobium oxide to alumina is more preferably 35/65 to 70/30. In addition, from the viewpoint of both the improvement of the carrier life and the negative fixed charge, the mass ratio of niobium oxide to alumina is preferably 50/50 to 90/10.

The mass ratio of niobium oxide to aluminum oxide in the passivation film can be determined by Energy Dispersive X-ray spectroscope (EDX), Secondary Ion Mass Spectrometer (SIMS), and high frequency 1. inductively coupled plasma-mass analysis spectrometry (ICP-MS). Specific measurement conditions are as follows. The passivation film is dissolved in an acid or alkaline aqueous solution, the solution is made into a mist and introduced into an Ar plasma, the light emitted when the excited element returns to the ground state is spectroscopically measured, and the wavelength and intensity are measured. The element is identified by the wavelength and quantified based on the intensity obtained.

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

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

In addition, the passivation film can also contain components other than niobium oxide and aluminum oxide in the form of organic components from the viewpoint of improving film quality or adjusting elastic modulus. The presence of organic components in the passivation film can be confirmed by elemental analysis and measurement of Fourier Transform-Infrared Spectroscopy (FT-IR) of the film.

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

The passivation film can also be coated with alumina precursor and niobium oxide precursor. It is obtained in the form of a heat-treated product of a cloth material. The coating material will be described in detail below.

The coating material of this embodiment contains an alumina precursor and a niobium oxide precursor, and is used to form a passivation film for a solar cell element having a silicon substrate.

The alumina precursor can be used without particular limitation as long as it produces alumina. The alumina precursor is preferably an organic alumina precursor in terms of uniformly dispersing alumina on a silicon substrate and chemically stable. Examples of organic alumina precursors include aluminum triisopropoxide (structural formula: Al (OCH (CH ₃ ) ₂ ) ₃ ), SYM-AL04 of the Institute of High-Purity Chemistry, etc. .

The niobium oxide precursor can be used without particular limitation as long as it produces niobium oxide. From the viewpoint of uniformly dispersing niobium oxide on a silicon substrate and from the viewpoint of chemical stability, it is preferable to use an organic niobium oxide precursor. Examples of the organic niobium oxide precursor include ethanol niobium (V) (structural formula: Nb (OC ₂ H ₅ ) ₅ , molecular weight: 318.21), Nb-05 of the Institute of High-Purity Chemistry, and the like.

A coating method or a printing method can be used to form a coating type material containing an organic niobium oxide precursor and an organic alumina precursor, and then remove the organic component by a subsequent heat treatment (calcination) to obtain a coating material. Passive film. Therefore, as a result, the passivation film may be a passivation film containing an organic component.

<Structure Description of Solar Cell Element>

Referring to FIGS. 10 to 13, the solar cell element of this embodiment is referred to. The structure is explained. 10 to 13 are cross-sectional views showing first to fourth configuration examples of a solar cell element using a passivation film on the back surface according to this embodiment.

As the silicon substrate (crystalline silicon substrate, semiconductor substrate) 101 used in this embodiment, any of single-crystal silicon and polycrystalline silicon can be used. In addition, as the silicon substrate 101, any of crystalline silicon having a conductivity type of p-type or crystalline silicon having a conductivity type of n-type can be used. From the viewpoint of further exerting the effects of this embodiment, crystalline silicon having a conductivity type of p-type is more suitable.

An example using p-type single crystal silicon as the silicon substrate 101 will be described in FIGS. 10 to 13 below. In addition, the monocrystalline silicon or polycrystalline silicon used in the silicon substrate 101 may be any one, and the resistivity is preferably 0.5Ω. cm ~ 10Ω. cm monocrystalline or polycrystalline silicon.

As shown in FIG. 10 (first configuration example), an n-type diffusion layer 102 doped with a group V element such as phosphorus is formed on the light-receiving surface side (upper side, first surface in the figure) of the p-type silicon substrate 101. 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 anti-reflection film 103 such as a silicon nitride (SiN) film and a first electrode 105 (a light-receiving surface-side electrode, a first-surface electrode, and the like) using silver (Ag) or the like are formed. Surface electrode, light receiving surface electrode). The light-receiving surface anti-reflection film 103 may also function as a light-receiving surface passivation film. By using the SiN film, both the functions of the light-receiving surface antireflection film and the light-receiving surface passivation film can be combined.

In addition, the solar cell element of this embodiment may or may not have the light-receiving surface anti-reflection film 103. In addition, on the light-receiving surface of the solar cell element, in order to reduce the reflectance of the surface, it is preferable to form a concave-convex junction. Texture (textured structure). The solar cell element of this embodiment may or may not have a textured structure.

On the other hand, a back surface field (BSF) layer as a layer doped with a group III element such as aluminum and boron is formed on the back side (lower side, second side, and back side) of the silicon substrate 101. 104. 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 formed on the back side of the silicon substrate 101 to make electrical contact with the BSF layer 104 (the surface on the back side of the silicon substrate 101 when the BSF layer 104 is not present). The electrode 106 (an electrode on the back side, a second surface electrode, a back electrode).

Next, in FIG. 10 (first configuration example), a contact region (except for the BSF layer 104 (the surface of the back surface side of the silicon substrate 101 when the BSF layer 104 is not present)) and the second electrode 106 is electrically connected except A passivation film (passivation layer) 107 containing alumina and niobium oxide is formed in a portion other than the opening OA). The passivation film 107 of this embodiment may have a negative fixed charge. With this fixed charge, electrons, which are minority carriers among carriers generated in the silicon substrate 101 by light, are reflected back to the surface side. Therefore, the short-circuit current is increased, and the photoelectric conversion efficiency can be expected to be improved.

Next, a second configuration example shown in FIG. 11 will be described. In FIG. 10 (first configuration example), the second electrode 106 is formed on the entire surface of the contact area (opening OA) and the passivation film 107, while in FIG. 11 (second configuration example), only the contact is formed. A second electrode 106 is formed on the area (opening OA). The second electrode may be formed on only a part of the contact area (opening OA) and the passivation film 107. Composition of 106. Even with the solar cell element having the configuration shown in FIG. 11, the same effects as those of FIG. 10 (first configuration example) can be obtained.

Next, a third configuration example shown in FIG. 12 will be described. In the third configuration example shown in FIG. 12, the BSF layer 104 is formed on only a part of the back surface side including the contact area (opening portion OA portion) with the second electrode 106, instead of as shown in FIG. 10 (first configuration Example) Generally formed on the entire surface on the back side. Even with a solar cell element having such a configuration (FIG. 12), the same effect as that of FIG. 10 (first configuration example) can be obtained. In addition, according to the solar cell element of the third configuration example in FIG. 12, the BSF layer 104, that is, a region doped with impurities at a higher concentration than the silicon substrate 101 by doping a group III element such as aluminum or boron, is less, A photoelectric conversion efficiency higher than that of FIG. 10 (first configuration example) can be obtained.

Next, a fourth configuration example shown in FIG. 13 will be described. In FIG. 12 (third configuration example), the second electrode 106 is formed on the entire surface of the contact area (opening OA) and the passivation film 107, while in FIG. 13 (fourth configuration example), only the contact is formed. A second electrode 106 is formed on the area (opening OA). A configuration in which the second electrode 106 is formed on only a part of the contact area (the opening OA) and the passivation film 107 may be set. Even with the solar cell element having the configuration shown in FIG. 13, the same effect as that of FIG. 12 (third configuration example) can be obtained.

In the case where the second electrode 106 is provided by a printing method and is formed on the entire surface of the back surface by firing at a high temperature, a warp that is convex upward is likely to occur during the cooling process. Such warpage may cause damage to the solar cell element, and the yield may decrease. In addition, warpage during the development of thin-film silicon substrates The problem becomes bigger. The reason for this warping is that the thermal expansion coefficient of the second electrode 106 containing a metal (for example, aluminum) is larger than that of the silicon substrate, and therefore the shrinkage during the temperature reduction process is large, so that stress is generated.

Based on the above, when the second electrode 106 is not formed on the entire surface of the back surface as shown in FIG. 11 (second configuration example) and FIG. 13 (fourth configuration example), the electrode structure tends to be vertically symmetrical and difficult to occur. The stress due to the difference in thermal expansion coefficient is preferred. In this case, it is preferable to provide a separate reflective layer.

<Explanation of the manufacturing method of solar cell elements>

Next, an example of the manufacturing method of the solar cell element (FIG. 11 thru | or FIG. 13) which has the said structure of this embodiment is demonstrated. However, this embodiment is not limited to the solar cell element produced by the method described below.

First, a texture structure is formed on the surface of the silicon substrate 101 shown in FIG. 10 and the like. The formation of the texture structure may be formed on both surfaces of the silicon substrate 101 or may be formed on only one surface (light-receiving surface side). In order to form a texture structure, the silicon substrate 101 is first immersed in a heated solution of potassium hydroxide or sodium hydroxide, and the damaged layer of the silicon substrate 101 is removed. After that, it is immersed in a solution containing potassium hydroxide and isopropyl alcohol as main components, thereby forming a texture structure on both sides or one side (light-receiving surface side) of the silicon substrate 101. In addition, as described above, the solar cell element of this embodiment may or may not have a texture structure, so this step may be omitted.

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

Thereafter, a solution of a coating-type dopant containing boron, aluminum, or the like is applied to the back surface side of the silicon substrate 101, and a heat treatment is performed to form a BSF layer 104 on the back surface side. For the application, methods such as screen printing, inkjet, dispensing, and spin coating can be used. After the heat treatment, layers such as boro glass and aluminum formed on the back surface are removed by hydrofluoric acid, hydrochloric acid, or the like, thereby forming a BSF layer 104. The method of forming the BSF layer 104 is not particularly limited. The BSF layer 104 is preferably formed in such a manner that the concentration range of boron and aluminum becomes 10 ¹⁸ cm ^-3 to 10 ²² cm ^-3 , and the BSF layer 104 is preferably formed in a dot shape or a line shape. . In addition, since the solar cell element of this embodiment may or may not have the BSF layer 104, this step may be omitted.

In addition, when the diffusion layer 102 on the light receiving surface and the BSF layer 104 on the back surface are both formed using a coating-type dopant solution, the solution of the dopant material may be separately provided to the silicon substrate 101. On both sides, a phosphorus diffusion layer (n ⁺ layer) as a diffusion layer 102 and a BSF layer 104 are formed together, and thereafter phosphorous glass, boron glass, and the like formed on the surface are removed together.

Thereafter, a silicon nitride film is formed on the diffusion layer 102 as the light-receiving surface anti-reflection film 103. The method of forming the light-receiving surface anti-reflection film 103 is not particularly limited. Receiving light The surface anti-reflection film 103 is preferably formed so that the thickness is in a range of 50 nm to 100 nm and the refractive index is in a range of 1.9 to 2.2. The light-receiving surface anti-reflection 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 anti-reflection film 103 such as a silicon nitride film can be produced by plasma CVD, thermal CVD, and the like. It is preferable to use plasma CVD to form the surface anti-reflection film 103 in a temperature range of 350 ° C to 500 ° C. Antireflection film 103.

Then, a passivation film 107 is formed on the back surface side of the silicon substrate 101. The passivation film 107 contains alumina and niobium oxide, and is formed, for example, by applying a heat treatment (calcination) to the following material (passivation material). The material (passivation material) contains an organic material that can be obtained by heat treatment (calcination). An alumina precursor represented by a metal decomposition coating type material and a niobium oxide precursor represented by a commercially available organometallic decomposition coating type material which can be obtained by heat treatment (calcination) of niobium oxide.

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

The coating material is applied to the area including the contact area (opening) by a method such as screen printing, overprint printing, printing using inkjet, printing using a dispenser, and the like. OA) on a predetermined pattern. In addition, the coating material is preferably pre-baked in a range of 80 ° C. to 180 ° C. to evaporate the solvent, and then carried out at 600 ° C. to 1000 ° C. for 30 minutes in a nitrogen environment or in the air. A heat treatment (annealing) for about 3 hours produces a passivation film 107 (an oxide film).

Furthermore, the openings (holes for contact) OA are preferably formed on the BSF layer 104 in a dot shape or a line shape.

The passivation film 107 used in the solar cell element described above preferably has a mass ratio of niobium oxide to alumina (niobium oxide / alumina) of 30/70 to 90/10, more preferably 30/70 to 80/20, and further preferably It is 35/65 ~ 70/30. This stabilizes the negative fixed charge. In addition, from the viewpoint of both the improvement of the carrier life and the negative fixed charge, the mass ratio of niobium oxide to alumina is preferably 50/50 to 90/10.

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

Then, a first electrode 105 is formed as an electrode on the light-receiving surface side. The first electrode 105 is formed by forming a paste containing silver (Ag) as a main component by screen printing on the light-receiving surface anti-reflection film 103 and performing heat treatment (fire-through). The shape of the first electrode 105 may be any shape, and may be, for example, a well-known shape including a finger electrode and a bus bar electrode.

Then, a second electrode 106 is formed as an electrode on the back side. The second electrode 106 is formed by applying a screen printing or dispenser to apply a paste containing aluminum as a main component and heat-treating the paste. The shape of the second electrode 106 is preferably the same as the shape of the BSF layer 104 and covers the entire surface on the back side. Shape, comb shape, grid shape, etc. In addition, the first electrode 105 and the second electrode 106, which are used to form the electrodes on the light-receiving surface side, may be printed separately, and then heat-treated (fired through) to form the first electrode 105 and the second electrode together. Electrode 106.

In addition, when the second electrode 106 is formed, a contact portion between the second electrode 106 and the silicon substrate 101 is self-aligned by using a paste containing aluminum (Al) as a main component and aluminum as a dopant to diffuse. A BSF layer 104 is formed. In addition, as described above, a solution of a coating-type dopant containing boron, aluminum, or the like may be applied to the back surface side of the silicon substrate 101 and heat-treated to form a BSF layer 104 separately.

In addition, the configuration example and manufacturing method using p-type silicon in the silicon substrate 101 are described above, and an n-type silicon substrate may be used as the silicon substrate 101. In this case, the diffusion layer 102 is formed by doping a group III element such as boron, and the BSF layer 104 is formed by doping a group V element such as phosphorus. However, in this case, it is necessary to pay attention to the following aspects: A negative fixed charge may sometimes cause a leakage current to flow when the inversion layer formed on the interface communicates with a portion in contact with the metal on the back side, and it is difficult to improve the conversion efficiency.

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. 14. FIG. 14 is a cross-sectional view showing a configuration example of a solar cell element using a light-receiving surface passivation film according to this embodiment.

In this case, the diffusion layer 102 on the light-receiving surface side is doped with boron to become p-type, holes in the generated carriers are collected on the light-receiving surface side, and electrons are collected on the back-surface side. Therefore, it is preferable that the passivation film 107 having a negative fixed charge is located on the light-receiving surface side.

An antireflection film made of SiN or the like may be further formed on a passivation film containing niobium oxide and aluminum oxide by CVD or the like.

Hereinafter, a detailed description will be given with reference to a reference example and a comparative example of this embodiment.

[Reference Example 1-1]

A commercially available organometallic decomposition coating type material that can obtain alumina (Al ₂ O ₃ ) by heat treatment (calcination) [SYM-AL04, High Purity Chemical Research Institute Co., Ltd., concentration: 2.3% by mass] 3.0 g, and a commercially available organometallic decomposition coating type material that can obtain niobium oxide (Nb ₂ O ₅ ) by heat treatment (calcination) [Nb-05 of High Purity Chemical Research Institute Co., Ltd., concentration: 5 mass% ] 3.0 g were mixed to prepare a passivation material (a-1) as a coating material.

The passivation material (a-1) was spin-coated on one side of an 8-inch p-type silicon substrate (8 Ω cm to 12 Ω cm) with a thickness of 725 μm and a natural oxide film removed by hydrofluoric acid at a concentration of 0.049% by mass. Pre-bake on a hot plate at 120 ° C for 3 minutes. Thereafter, a heat treatment (calcination) was performed at 650 ° C. for 1 hour under a nitrogen atmosphere to obtain a passivation film containing niobium oxide and niobium oxide [niobium oxide / alumina = 68/32 (mass ratio)]. The film thickness was measured by an ellipsometer, and it was 43 nm. When the FT-IR of the passivation film was measured, a very weak peak derived from an alkyl group was seen around 1200 cm ^-1 .

Then, on the passivation film, a plurality of aluminum electrodes with a diameter of 1 mm were formed through a metal mask through evaporation to form a metal-insulator-semiconductor (MIS) structure capacitor. The voltage dependency (CV characteristic) of the capacitance of the capacitor was measured with a commercially available prober and an LCR meter (HP Corporation, 4275A). The results show that the flat band voltage (Vfb) moves from -0.81V of the ideal value to + 0.32V. From this amount of movement, it is known that the passivation film obtained from the passivation material (a-1) exhibits a fixed charge with a fixed charge density (Nf) of -7.4 × 10 ¹¹ cm ^-2 and a negative value.

The passivation material (a-1) was applied to both sides of an 8-inch p-type silicon substrate in the same manner as described above, pre-baked, and heat-treated (calcined) at 650 ° C for 1 hour in a nitrogen atmosphere to produce a silicon substrate A sample covered on both sides by a passivation film. The carrier life of these samples was measured by a life measuring device (Kobelco Research Institute Co., Ltd., RTA-540). As a result, the carrier lifetime was 530 μs. For comparison, the same 8-inch p-type silicon substrate was passivated by the iodine passivation method and measured. As a result, the carrier lifetime was 1100 μs.

From the above, it is known that the passivation film obtained by heat-treating (calcining) the passivation material (a-1) shows a certain degree of passivation performance and shows a negative fixed charge.

[Reference Example 1-2]

As in Reference Example 1-1, a commercially available organometallic decomposition coating type material capable of obtaining alumina (Al ₂ O ₃ ) by heat treatment (calcination) [High Purity Chemical Research Institute Co., Ltd., SYM -AL04, concentration: 2.3% by mass], and a commercially available organometallic decomposition coating type material that can obtain niobium oxide (Nb ₂ O ₅ ) by heat treatment (calcination) [High Purity Chemical Research Institute Co., Ltd., Nb -05, with a concentration of 5% by mass], and mixed by changing the ratio to prepare the passivation materials (a-2) to passivation materials (a-7) shown in Table 4.

In the same manner as in Reference Example 1-1, the passivation material (a-2) to the passivation material (a-7) Each is provided on one surface of a p-type silicon substrate, and is heat-treated (fired) 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 based on this.

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

Depending on the ratio (mass ratio) of niobium oxide / alumina after heat treatment (calcination), the results are different, but regarding the passivation material (a-2) to passivation material (a-7), the carrier life after heat treatment (calcination) Since it shows a certain value, it is suggested that it functions as a passivation film. It is learned that the passivation films obtained from the passivation materials (a-2) to (a-7) all show a negative fixed charge stably, and can also be preferably used as a passivation film for a p-type silicon substrate.

[Reference Example 1-3]

Commercially available ethanol niobium (V) (structural formula: Nb (OC ₂ H ₅ ) ₅ , molecular weight: 318.21) 3.18 g (0.010 mol), commercially available aluminum triisopropoxide (structural formula: Al (OCH (CH (CH ₃ ) ₂ ) ₃ , molecular weight: 204.25) 1.02 g (0.005 mol) was dissolved in 80 g of cyclohexane to prepare a passivation material (c-1) having a concentration of 5% by mass.

The passivation material (c-1) was spin-coated on one side of an 8-inch p-type silicon substrate (8Ωcm ~ 12Ωcm) with a thickness of 725 μm and a natural oxide film removed by hydrofluoric acid at a concentration of 0.049% by mass, Pre-baking was performed on a hot plate at 120 ° C for 3 minutes. Thereafter, a heat treatment (calcination) was performed at 600 ° C. for 1 hour in a nitrogen atmosphere to obtain a passivation film containing alumina and niobium oxide. The film thickness was measured by an ellipsometer, and it was 50 nm. Elementary analysis revealed that Nb / Al / C = 81/14/5 (mass%). When the FT-IR of the passivation film was measured, a very weak peak derived from an alkyl group was seen around 1200 cm ^-1 .

Then, on the passivation film, a plurality of aluminum electrodes with a diameter of 1 mm were formed through a metal mask through evaporation to form a metal-insulator-semiconductor (MIS) structure capacitor. The voltage dependency (CV characteristic) of the capacitance of the capacitor was measured with a commercially available prober and an LCR meter (HP Corporation, 4275A). The results show that the flat band voltage (Vfb) moves from -0.81V of the ideal value to + 4.7V. From this amount of movement, it is known that the passivation film obtained from the passivation material (c-1) exhibits a fixed charge with a fixed charge density (Nf) of -3.2 × 10 ¹² cm ^-2 and a negative value.

The passivation material (c-1) was applied to both sides of an 8-inch p-type silicon substrate in the same manner as described above, pre-baked, and heat-treated (calcined) at 600 ° C for 1 hour in a nitrogen atmosphere to produce a silicon substrate The two sides of the sample were covered by a passivation film. By The life measuring device (Kobelco Research Institute Co., Ltd., RTA-540) measures the carrier life of these samples. As a result, the carrier lifetime was 330 μs. For comparison, the same 8-inch p-type silicon substrate was passivated by the iodine passivation method and measured. As a result, the carrier lifetime was 1100 μs.

From the above, it is known that the passivation film obtained by heat-treating (calcining) the passivation material (c-1) shows a certain degree of passivation performance and shows a negative fixed charge.

[Reference Example 1-4]

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

The passivation material (c-2) was spin-coated on one side of an 8-inch p-type silicon substrate (8 Ω cm to 12 Ω cm) with a thickness of 725 μm and a natural oxide film removed by hydrofluoric acid at a concentration of 0.049% by mass. Pre-baking was performed on a hot plate at 120 ° C for 3 minutes. Thereafter, a heat treatment (calcination) was performed at 600 ° C. for 1 hour in a nitrogen atmosphere to obtain a passivation film containing alumina and niobium oxide. The film thickness was measured by an ellipsometer, and 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 very weak peak derived from an alkyl group was seen around 1200 cm ^-1 .

Then, on the passivation film, a plurality of aluminum electrodes with a diameter of 1 mm were formed by vapor deposition through a metal mask to produce a metal-insulator-semiconductor (Semiconductor, MIS) structure capacitor. The voltage dependency (CV characteristic) of the capacitance of the capacitor was measured with a commercially available prober and an LCR meter (HP Corporation, 4275A). The results show that the flat band voltage (Vfb) moves from -0.81V of the ideal value to + 0.10V. From this amount of movement, it was found that the passivation film obtained from the passivation material (c-2) showed a fixed charge with a fixed charge density (Nf) of -0.8 × 10 ¹¹ cm ^-2 and a negative value.

The passivation material (c-2) was applied to both sides of an 8-inch p-type silicon substrate in the same manner as described above, pre-baked, and heat-treated (calcined) at 600 ° C for 1 hour in a nitrogen atmosphere to produce a silicon substrate. The two sides of the sample were covered by a passivation film. The carrier life of this sample was measured by a life 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 passivated by the iodine passivation method and measured. As a result, the carrier lifetime was 1100 μs.

From the above, it is known that the passivation film obtained from the passivation material (c-2) shows a certain degree of passivation performance and shows 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 type material capable of obtaining alumina (Al ₂ O ₃ ) by heat treatment (calcination) [SYM of High Purity Chemical Research Institute Co., Ltd.] -AL04, concentration: 2.3% by mass], and a commercially available organometallic decomposition coating type material that can obtain niobium oxide (Nb ₂ O ₅ ) by heat treatment (calcination) [Nb of High Purity Chemical Research Institute Co., Ltd. -05, with a concentration of 5 mass%] and mixed with varying ratios to prepare the passivation materials (b-1) to passivation materials (b-7) shown in Table 5.

In the same manner as in Reference Example 1-1, the passivation material (b-1) to the passivation material (b-7) were respectively applied to one side of a p-type silicon substrate, and heat treatment (calcination) was performed to prepare a passivation film. The voltage dependence of the capacitance was measured with a passivation film, and a fixed charge density was calculated based on this.

Further, in the same manner as in Reference Example 1-1, a passivation material (coated material) was applied to both sides of the p-type silicon substrate, and the carrier life was measured using a cured sample. The obtained results are summarized in Table 5.

It is known that the carrier lifetime of the passivation film obtained from the passivation material (b-1) to the passivation material (b-6) is large, and it has a function as a passivation layer. In addition, when the niobium oxide / alumina is 10/90 and 20/80, the value of the fixed charge density varies greatly, and a negative fixed charge density cannot be obtained stably. However, it was confirmed that the Achieve negative fixed charge density. It was found that when the measurement was performed by the CV method using a passivation material having a niobium oxide / alumina of 10/90 and 20/80, it sometimes became positive. A constant-charge passivation film does not stably show a negative fixed charge. Furthermore, a passivation film showing a positive fixed charge can be used as a passivation film of an n-type silicon substrate.

On the other hand, the passivation material (b-7) whose alumina reached 100% by mass cannot obtain a negative fixed charge density.

[Reference Comparative Example 1-2]

A commercially available organometallic decomposition coating type material that can be obtained by heat treatment (calcination) to obtain titanium oxide (TiO ₂ ) as a passivation material (d-1) [Ti-03-, High Purity Chemical Research Institute Co., Ltd. P, concentration is 3% by mass], as a passivation material (d-2), a commercially available organometallic decomposition coating type material capable of obtaining tantalum titanate (BaTiO ₃ ) by heat treatment (calcination) [high purity chemical research BT-06 Co., Ltd., a concentration of 6% by mass], and a commercially available organometallic decomposition coating capable of obtaining hafnium oxide (HfO ₂ ) by heat treatment (calcination) as a passivation material (d-3) Type material [Hf-05 of High Purity Chemical Research Institute Co., Ltd., concentration: 5 mass%].

The passivation material (d-1) to the passivation material (d-3) were applied to one side of a p-type silicon substrate in the same manner as in Reference Example 1-1, and then subjected to heat treatment (calcination) to produce a passivation film. This passivation film was used to measure the voltage dependence of the electrostatic capacitance, and based on this, a fixed charge density was calculated.

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

It is known that the carrier lifetime of the passivation film obtained from the passivation material (d-1) to the passivation material (d-3) is small, and the passivation function is insufficient. In addition, it showed a positive fixed charge. Although the passivation film obtained from the passivation material (d-3) has a negative fixed charge, its value is small. In addition, the carrier life is relatively short and the passivation function is insufficient.

[Reference Example 1-6]

A monocrystalline silicon substrate doped with boron was used as the silicon substrate 101 to produce a solar cell element having a structure shown in FIG. 12. After the surface of the silicon substrate 101 is textured, a coating-type phosphorus diffusion material is applied to the light-receiving surface side, and a diffusion layer 102 (phosphorus diffusion layer) is formed by heat treatment. After that, the coating-type phosphorus diffusion material was removed by dilute hydrofluoric acid.

Then, a SiN film produced by plasma CVD is formed on the light-receiving surface side as the light-receiving surface anti-reflection film 103. Thereafter, the passivation material (a-1) prepared in Reference Example 1-1 was applied to an area other than the contact area (opening portion OA) in the back surface side of the silicon substrate 101 by an inkjet method. Thereafter, heat treatment is performed to form a passivation film 107 having an opening OA.

In addition, as the passivation film 107, another sample using the passivation material (c-1) prepared in Reference Example 1-3 was also prepared.

Next, on a light receiving surface antireflection film 103 (SiN film) formed on the light receiving surface side of the silicon substrate 101, a paste having silver as a main component is screen-printed in a predetermined shape of a finger electrode and a bus bar electrode. On the back side, a paste screen containing aluminum as a main component is printed on the entire surface. Thereafter, heat treatment (burn-through) was performed at 850 ° C. to form electrodes (first electrode 105 and second electrode 106), and aluminum was diffused into the opening portion OA on the back surface to form a BSF layer 104 to form FIG. 12. The solar cell element of the structure shown.

The silver electrode on the light-receiving surface is described here as a firing step without opening holes in the SiN film. However, the opening portion OA may be formed in the SiN film by etching or the like in advance, and then a silver electrode may be formed.

For comparison, in the above manufacturing steps, the passivation film 107 is not formed, but an aluminum paste is printed on the entire surface of the back side, and a p ⁺ layer 114 corresponding to the BSF layer 104 and a second electrode are formed on the entire surface. The corresponding electrode 116 forms a solar cell element having a structure shown in FIG. 9. The solar cell elements were evaluated for characteristics (short-circuit current, open-circuit voltage, curve factor, and conversion efficiency). The characteristic evaluation was measured based on JIS-C-8913 (2005) and JIS-C-8914 (2005). The results are shown in Table 7.

Table 7 shows that the solar cell element with a passivation film 107 containing a niobium oxide and aluminum oxide layer has a higher short-circuit current and open-circuit voltage than a solar cell element without a passivation film 107, and has the highest conversion efficiency (photoelectric conversion efficiency). Increase by 1%.

<Reference Embodiment 2>

The following is the passivation film, coating material, solar cell element, and silicon substrate with a passivation film of Reference Embodiment 2.

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

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

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

<4> The passivation film according to any one of <1> to <3>, which contains an oxide of two or three vanadium group elements selected from the group consisting of vanadium oxide, niobium oxide, and tantalum oxide. As an oxide of the vanadium group element.

<5> The passivation film according to any one of <1> to <4>, which is a heat-treated product of a coating material that contains a precursor of alumina, 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.

<6> A coating material containing a precursor of alumina 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, and A passivation film for forming a solar cell element having a silicon substrate.

<7> A solar cell element including: a p-type silicon substrate; an n-type impurity diffusion layer formed on a first surface side that is a light-receiving surface side of the silicon substrate; a first electrode formed on the impurity diffusion layer; and passivation A film is formed on the second surface side of the silicon substrate opposite to the light-receiving surface side and has an opening; and a second electrode is formed on the second surface side of the silicon substrate and communicates with the above through the opening of the passivation film The second surface side of the silicon substrate is electrically connected; and the passivation film contains aluminum oxide and an oxide of at least one vanadium group element selected from the group consisting of vanadium oxide and tantalum oxide.

<8> The solar cell element according to <7>, which has a p-type impurity diffusion layer which is formed on a part or all of the second surface side of the silicon substrate, and which Impurities are added at a higher concentration, and the second electrode is electrically connected to the p-type impurity diffusion layer through the opening of the passivation film.

<9> A solar cell element comprising: an n-type silicon substrate; a p-type impurity diffusion layer formed on a first surface side that is a light-receiving surface side of the silicon substrate; a first electrode formed on the impurity diffusion layer; and passivation A film is formed on the second surface side of the silicon substrate opposite to the light-receiving surface side and has an opening; and a second electrode is formed on the second surface side of the silicon substrate and communicates with the above through the opening of the passivation film The second surface side of the silicon substrate is electrically connected; and the passivation film contains aluminum oxide and an oxide of at least one vanadium group element selected from the group consisting of vanadium oxide and tantalum oxide.

<10> The solar cell element according to <9>, which has an n-type impurity diffusion layer which is formed on a part or all of the second surface side of the silicon substrate, and which Impurities are added at a higher concentration, and the second electrode is electrically connected to the n-type impurity diffusion layer through the 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 to the alumina of 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 vanadium group element oxide and the alumina of the passivation film is 90% or more.

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

<14> A silicon substrate with a passivation film, comprising: a silicon substrate; and the solar cell element according to any one of <1> to <5> provided on the entire surface or a part of the silicon substrate. Passive film.

According to the above-mentioned reference embodiment, a passivation film having a negative fixed charge and extending the carrier life of a silicon substrate can be realized at a low cost. In addition, a coating-type material can be provided to realize the formation of the passivation film. 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 negative fixed charge and extending the carrier life of the silicon substrate can be realized at a low cost.

The passivation film of this embodiment is a passivation film used in a silicon solar cell element, and contains an oxide of at least one vanadium group element selected from the group consisting of vanadium oxide and tantalum oxide.

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

From the viewpoint of stabilizing the negative fixed charge, the mass ratio of the oxide of the vanadium group element to the alumina is more preferably 35/65 to 90/10, and further preferably 50/50 to 90/10.

The mass ratio of the vanadium group oxide to alumina in the passivation film can be determined by energy dispersive X-ray spectroscopy (EDX), secondary ion mass spectrometry (SIMS), and high-frequency inductively coupled plasma mass spectrometry ( ICP-MS). Specific measurement conditions are as follows in the case of ICP-MS, for example. The passivation film is dissolved in an acid or alkaline aqueous solution, the solution is made into a mist and introduced into an Ar plasma, the light emitted when the excited element returns to the ground state is spectroscopically measured, and the wavelength and intensity are measured. The element is identified by the wavelength and quantified based on the intensity obtained.

The total content of the vanadium group element oxide and alumina in the passivation film is preferably 80% by mass or more, and from the viewpoint of maintaining good characteristics, it is more preferably 90% by mass or more. When there are many components other than oxides of vanadium group elements and alumina in a passivation film, the effect of a negative fixed charge becomes large.

In addition, from the viewpoint of improving the film quality and adjusting the elastic modulus in the passivation film, components other than the oxide of the vanadium group element and alumina can also be contained as organic components. The presence of organic components in the passivation film can be confirmed by elemental analysis and measurement of Fourier Transform-Infrared Spectroscopy (FT-IR) of the film.

From the viewpoint of obtaining a larger negative fixed charge, the vanadium group element oxide is preferably selected from vanadium oxide (V ₂ O ₅ ).

The passivation film may contain an oxide of two or three vanadium group elements selected from the group consisting of vanadium oxide, niobium oxide, and tantalum oxide as the vanadium group element oxide.

The passivation film is preferably obtained by heat-treating a coating material. It is more preferable to obtain it by forming a coating-type material into a film using a coating method or a printing method, and then removing the organic component by heat treatment. That is, the passivation film can also be obtained as a heat-treated product of a coating-type material containing an alumina precursor and a precursor of an oxide of a vanadium group element. The details of the coating material will be described later.

The coating material of this embodiment is a coating material for a passivation film for a solar cell element having a silicon substrate, and contains a precursor of alumina, and a precursor selected from a precursor of vanadium oxide and a precursor of tantalum oxide. A precursor of an oxide of at least one vanadium group element in the composed group. From the viewpoint of the negative fixed charge of the passivation film formed of the coating material, the precursor of the vanadium group element oxide contained in the coating material is preferably a precursor of selected vanadium oxide (V ₂ O ₅ ). . The coating material may also contain, as a vanadium group, a precursor of an oxide of two or three vanadium group elements selected from the group consisting of a precursor of vanadium oxide, a precursor of niobium oxide, and a precursor of tantalum oxide. A precursor of an oxide of an element.

The alumina precursor can be used without particular limitation as long as it produces alumina. From the viewpoint of uniformly dispersing alumina on a silicon substrate and from the viewpoint of chemical stability, an alumina precursor is preferably an organic alumina precursor. Examples of the organic alumina precursor include aluminum triisopropoxide (structural formula: Al (OCH (CH ₃ ) ₂ ) ₃ ), and SYM-AL04 of the Institute of High-Purity Chemistry.

The precursor of an oxide of a vanadium group element can be used without particular limitation as long as it produces an oxide of a vanadium group element. From the viewpoint of uniformly dispersing alumina on a silicon substrate and from the viewpoint of chemical stability, the precursor of the vanadium group element oxide is preferably a precursor using an organic vanadium group element oxide.

Examples of organic vanadium oxide precursors include: vanadium oxytriethanol (V) (structural formula: VO (OC ₂ H ₅ ) ₃ , molecular weight: 202.13), V- 02. Examples of the organic tantalum oxide precursor include tantalum methanol (V) (structural formula: Ta (OCH ₃ ) ₅ , molecular weight: 336.12), and Ta-10-P of the Institute of High-Purity Chemistry. Examples of the organic niobium oxide precursor include ethanol niobium (V) (structural formula: Nb (OC ₂ H ₅ ) ₅ , molecular weight: 318.21), and Nb-05 of the Institute of High-Purity Chemistry.

A coating method or a printing method is used to form a coating material containing a precursor of an organic vanadium group oxide and an organic alumina precursor, and then remove the organic component by a subsequent heat treatment. This makes it possible to obtain a passivation film. Therefore, as a result, the passivation film may be a passivation film containing an organic component. The content of the organic component in the passivation film is preferably less than 10% by mass, more preferably 5% by mass or less, and even more preferably 1% by mass or less.

The solar cell element (photoelectric conversion device) of this embodiment has a passivation film (insulating film, protective insulating film) described in the above embodiment near the photoelectric conversion interface of the silicon substrate, that is, it contains aluminum oxide, and is selected from vanadium oxide and A film of an oxide of at least one vanadium group element in a group consisting of tantalum oxide. An oxide containing alumina and at least one vanadium group element selected from the group consisting of vanadium oxide and tantalum oxide can extend the carrier life of a silicon substrate and have a negative fixed charge, thereby improving solar cell elements. Characteristics (photoelectric conversion efficiency).

For a description of the structure and manufacturing method of the solar cell element according to this embodiment, refer to the description of the structure and manufacturing method of the solar cell element according to Embodiment 1.

Hereinafter, a detailed description will be given with reference to a reference example and a comparative example of this embodiment.

<Case where vanadium oxide is used as an oxide of a vanadium group element>

[Reference Example 2-1]

A commercially available organometallic thin film coating-type material that can obtain alumina (Al ₂ O ₃ ) by heat treatment (calcination) [Institute of High Purity Chemistry (Institute of Chemistry), SYM-AL04, concentration: 2.3% by mass] 3.0 g. Commercially available organometallic thin film coating type materials that can obtain vanadium oxide (V ₂ O ₅ ) by heat treatment (calcination) [Institute of High Purity Chemistry, Ltd., V-02, concentration: 2% by mass ] 6.0 g were mixed to prepare a passivation material (a2-1) as a coating material.

A passivation material (a2-1) was spin-coated on an 8-inch p-type silicon substrate (8 Ω · cm ~ 12 Ω · cm) with a thickness of 725 μm and a natural oxide film removed by hydrofluoric acid at a concentration of 0.49% by mass. On one side, it was placed on a hot plate and pre-baked at 120 ° C for 3 minutes. Thereafter, a heat treatment (calcination) was performed at 700 ° C. for 30 minutes under a nitrogen atmosphere to obtain a passivation film containing vanadium oxide and vanadium oxide [vanadium oxide / alumina = 63/37 (mass%)]. The film thickness was measured by an ellipsometer, and it was 51 nm. When the FT-IR of the passivation film was measured, a very weak peak derived from an alkyl group was seen around 1200 cm ^-1 .

Then, on the passivation film, a plurality of aluminum electrodes with a diameter of 1 mm were formed through a metal mask through evaporation to form a metal-insulator-semiconductor (MIS) structure capacitor. The voltage dependency (CV characteristic) of the capacitance of the capacitor was measured with a commercially available prober and an LCR meter (HP Corporation, 4275A). The results show that the flat band voltage (Vfb) moves from -0.81V of the ideal value to + 0.02V. From this amount of movement, it is known that the passivation film obtained from the passivation material (a2-1) exhibits a fixed charge with a fixed charge density (Nf) of -5.2 × 10 ¹¹ cm ^-2 and a negative value.

The passivation material (a2-1) was coated on both sides of an 8-inch p-type silicon substrate in the same manner as described above, pre-baked, and heat-treated (calcined) at 650 ° C for 1 hour in a nitrogen atmosphere to produce silicon A sample in which both sides of the substrate were covered with a passivation film. The carrier life of this sample was measured by a life measuring device (Kobelco Research Institute (Stock), RTA-540). As a result, the carrier lifetime was 400 μs. For comparison, the same 8-inch p-type silicon substrate was passivated by the iodine passivation method and measured. As a result, the carrier lifetime was 1100 μs. In addition, after 14 days had elapsed after the sample was prepared, the carrier lifetime was measured again. As a result, the carrier lifetime was 380 μs. From this, it is understood that the decrease in carrier life (400 μs to 380 μs) is within -10%, and the decrease in carrier life is small.

From the above, it is known that the passivation film obtained by heat-treating (calcining) the passivation material (a2-1) shows a certain degree of passivation performance and shows a negative fixed charge.

[Reference Example 2-2]

As in Reference Example 2-1, a commercially available organometallic thin film coating type material capable of obtaining alumina (Al ₂ O ₃ ) by heat treatment (calcination) [Institute of High Purity Chemistry (Institute of Chemistry), SYM -AL04, concentration: 2.3% by mass], and a commercially available organometallic film coating type material that can obtain vanadium oxide (V ₂ O ₅ ) by heat treatment [Institute of High Purity Chemistry, Inc., V-02, The concentration was 2% by mass] and the ratio was changed and mixed to prepare passivation materials (a2-2) to passivation materials (a2-7) shown in Table 8.

In the same manner as in Reference Example 2-1, a passivation material (a2-2) to a passivation material (a2-7) were each coated on one side of a p-type silicon substrate, and heat-treated (calcined) to prepare a passivation film. The voltage dependence of the capacitance of the obtained passivation film was measured, and the fixed charge density was calculated based on this.

Then, in the same manner as in Reference Example 2-1, a passivation material was applied to both sides of the p-type silicon substrate, and heat treatment (calcination) was performed, and the carrier life was measured using the obtained sample.

The obtained results are summarized in Table 8. In addition, the carrier life was measured again after 14 days after the sample was produced. As a result, the carrier life reduction of the passivation film using the passivation material (a2-2) to the passivation material (a2-7) shown in Table 8 was- Within 10%, the decrease in carrier life is small.

Depending on the ratio (mass ratio) of vanadium oxide / alumina after heat treatment (calcination), the results are different, but the passivation material (a2-2) ~ passivation material (a2-7) all show negative fixation after heat treatment (calcination). The charge and carrier lifetime also show a certain value, so it is suggested to function as a passivation film. It is learned that the passivation films obtained from the passivation material (a2-2) to the passivation material (a2-7) all stably show a negative fixed charge, and can also be preferably used as a passivation film for a p-type silicon substrate.

[Reference Example 2-3]

The commercially available compound may be by heat treatment (calcination) obtained by vanadium oxide (V ₂ O ₅₎ a triethanolammonium group vanadium (V) (structural _{formula: VO (OC 2 H 5)} 3, molecular weight: 202.13) 1.02 g (0.010 mol) and a commercially available aluminum triisopropoxide (structure formula: Al (OCH (CH ₃ ) ₂ ) as a compound capable of obtaining alumina (Al ₂ O ₃ ) by heat treatment (calcination) ₃ , molecular weight: 204.25) 2.04 g (0.010 mol) was dissolved in 60 g of cyclohexane to prepare a passivation material (b2-1) having a concentration of 5% by mass.

The passivation material (b2-1) was spin-coated on an 8-inch p-type silicon substrate (8 Ω · cm ~ 12 Ω · cm) with a thickness of 725 μm and a natural oxide film removed by hydrofluoric acid at a concentration of 0.49% by mass. On one side, pre-baking was performed on a hot plate at 120 ° C for 3 minutes. Thereafter, a heat treatment (calcination) was performed at 650 ° C. for 1 hour under a nitrogen atmosphere to obtain a passivation film containing alumina and vanadium oxide. The film thickness was measured by an ellipsometer, and it was 60 nm. Elementary analysis revealed that V / Al / C = 64/33/3 (mass%). When the FT-IR of the passivation film was measured, a very weak peak derived from an alkyl group was seen around 1200 cm ^-1 .

Then, on the passivation film, a plurality of aluminum electrodes with a diameter of 1 mm were formed through a metal mask through evaporation to form a metal-insulator-semiconductor (MIS) structure capacitor. The voltage dependency (CV characteristic) of the capacitance of the capacitor was measured with a commercially available prober and an LCR meter (HP Corporation, 4275A). The results show that the flat band voltage (Vfb) moves from -0.81V of the ideal value to + 0.10V. From this amount of movement, it is known that the passivation film obtained from the passivation material (b2-1) exhibits a fixed charge with a fixed charge density (Nf) of -6.2 × 10 ¹¹ cm ^-2 and a negative value.

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

From the above, it is known that the passivation film obtained by heat-treating (calcining) the passivation material (b2-1) shows a certain degree of passivation performance and shows a negative fixed charge.

[Reference Example 2-4]

Commercially available vanadium oxytriethanol (V) (structural formula: VO (OC ₂ H ₅ ) ₃ , molecular weight: 202.13) 1.52 g (0.0075 mol), 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 novolac resin were dissolved in 10 g of diethylene glycol monobutyl ether acetate and 10 g of cyclohexane to prepare a passivation material (b2 -2).

The passivation material (b2-2) was spin-coated on an 8-inch p-type silicon substrate (8 Ω · cm ~ 12 Ω · cm) with a thickness of 725 μm and a natural oxide film removed by hydrofluoric acid at a concentration of 0.49% by mass. On one side, it was placed on a hot plate and pre-baked at 120 ° C for 3 minutes. Then, it heated at 650 degreeC for 1 hour in nitrogen atmosphere, and obtained the passivation film containing alumina and vanadium oxide. The film thickness was measured by an ellipsometer, and 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 very weak peak derived from an alkyl group was seen around 1200 cm ^-1 .

Then, on the passivation film, a plurality of aluminum electrodes with a diameter of 1 mm were formed through a metal mask through evaporation to form a metal-insulator-semiconductor (MIS) structure capacitor. The voltage dependency (CV characteristic) of the capacitance of the capacitor was measured with a commercially available prober and an LCR meter (HP Corporation, 4275A). The results show that the flat band voltage (Vfb) moves from -0.81V of the ideal value to + 0.03V. From this amount of movement, it was found that the passivation film obtained from the passivation material (b2-2) showed a fixed charge with a fixed charge density (Nf) of -2.0 × 10 ¹¹ cm ^-2 and a negative value.

In the same manner as above, a passivation material (b2-2) was coated on both sides of an 8-inch p-type silicon substrate, pre-baked, and heat-treated (calcined) at 600 ° C for 1 hour in a nitrogen atmosphere to produce A sample with both sides of a silicon substrate covered with a passivation film. With a life measuring device (Kobelco Research Institute) (Strand), RTA-540) The carrier life of this sample was measured. As a result, the carrier lifetime was 170 μs. For comparison, the same 8-inch p-type silicon substrate was passivated by the iodine passivation method and measured. As a result, the carrier lifetime was 1100 μs.

From the above, it is known that the passivation film hardened by the passivation material (b2-2) shows a certain degree of passivation performance and shows a negative fixed charge.

<Case where tantalum oxide is used as an oxide of a vanadium group element>

[Reference Example 2-5]

A commercially available organometallic thin film coating type material that can obtain alumina (Al ₂ O ₃ ) by heat treatment (calcination) [Institute of High Purity Chemistry (Institute of Chemistry), SYM-AL04, concentration: 2.3% by mass], Change the ratio with a commercially available organometallic thin film coating type material that can obtain tantalum oxide (Ta ₂ O ₅ ) by heat treatment [Institute of High Purity Chemistry (Stock), Ta-10-P, concentration: 10% by mass] While mixing, passivation materials (c2-1) to passivation materials (c2-6) shown in Table 9 were prepared.

A passivation material (c2-1) to a passivation material (c2-6) were spin-coated on an 8-inch p-type silicon substrate (725 μm in thickness and 725 μm in which the natural oxide film was removed with hydrofluoric acid at a concentration of 0.49 mass%) 8Ω.cm ~ 12Ω.cm) on one side, placed on a hot plate and pre-baked at 120 ° C for 3 minutes. Thereafter, a heat treatment (calcination) was performed at 700 ° C. for 30 minutes under a nitrogen atmosphere to obtain a passivation film containing alumina and tantalum oxide. Using this passivation film, the voltage dependency of the capacitance was measured, and the fixed charge density was calculated based on this.

Then, the passivation material (c2-1) to the passivation material (c2-6) were respectively coated on both sides of an 8-inch p-type silicon substrate, and pre-baking was performed under a nitrogen atmosphere. A heat treatment (calcination) was performed at 650 ° C for 1 hour to prepare a sample in which both sides of the silicon substrate were covered with a passivation film. The carrier life of this sample was measured by a life measuring device (Kobelco Research Institute (Korea), RTA-540).

The obtained results are summarized in Table 9. In addition, the carrier life was measured again after 14 days after the sample was prepared. As a result, it was found that the carrier life reductions of the passivation films using the passivation material (c2-1) to the passivation material (c2-6) shown in Table 9 are all Within -10%, the decrease in carrier life is small.

Depending on the ratio (mass ratio) of tantalum oxide / alumina after heat treatment (calcination), the results are different, but the passivation material (c2-1) to passivation material (c2-6) all show negative fixation after heat treatment (calcination). The charge and carrier lifetime also show a certain value, so it is suggested to function as a passivation film.

[Reference Example 2-6]

Commercially available tantalum methanol (V) (structure: Ta (OCH ₃ ) ₅ , molecular weight: 336.12) 1.18 g (0.0025 mol) as a compound capable of obtaining tantalum oxide (Ta ₂ O ₅ ) by heat treatment (calcination) ), And commercially available aluminum triisopropoxide (structural formula: Al (OCH (CH ₃ ) ₂ ) ₃ , which is a compound capable of obtaining alumina (Al ₂ O ₃ ) by heat treatment (calcination), 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.

A passivation material (d2-1) was spin-coated on an 8-inch p-type silicon substrate (8 Ω · cm ~ 12 Ω · cm) with a thickness of 725 μm and a natural oxide film having a concentration of 0.49% by mass of hydrofluoric acid removed in advance. On one side, it was placed on a hot plate and pre-baked at 120 ° C for 3 minutes. Then, it heated at 700 degreeC for 1 hour in nitrogen atmosphere, and obtained the passivation film containing alumina and tantalum oxide. The film thickness was measured by an ellipsometer, and 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 very weak peak derived from an alkyl group was seen around 1200 cm ^-1 .

Then, on the passivation film, a plurality of aluminum electrodes with a diameter of 1 mm were formed through a metal mask through evaporation to form a metal-insulator-semiconductor (MIS) structure capacitor. The voltage dependency (CV characteristic) of the capacitance of the capacitor was measured with a commercially available prober and an LCR meter (HP Corporation, 4275A). The results show that the flat band voltage (Vfb) moves from -0.81V, which is the ideal value, to -0.30V. From this amount of movement, it is known that the passivation film obtained from the passivation material (d2-1) exhibits a fixed charge with a fixed charge density (Nf) of -6.2 × 10 ¹⁰ cm ^-2 and a negative value.

The passivation material (d2-1) was coated on both sides of an 8-inch p-type silicon substrate in the same manner as above, and pre-baking was performed at 600 ° C for 1 hour in a nitrogen atmosphere. Heat treatment (calcination) to produce a sample in which both sides of the silicon substrate are covered with a passivation film. The carrier life of this sample was measured by a life measuring device (Kobelco Research Institute (Korea), RTA-540). As a result, the carrier lifetime was 610 μs. For comparison, the same 8-inch p-type silicon substrate was passivated by the iodine passivation method and measured. As a result, the carrier lifetime was 1100 μs.

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

[Reference Example 2-7]

Commercially available tantalum methanol (V) (structure: Ta (OCH ₃ ) ₅ , molecular weight: 336.12) 1.18 g (0.005 mol) as a compound capable of obtaining tantalum oxide (Ta ₂ O ₅ ) by heat treatment (calcination) ), A commercially available aluminum triisopropoxide (structure: Al (OCH (CH ₃ ) ₂ ) ₃ , molecular weight: 204.25) as a compound capable of obtaining alumina (Al ₂ O ₃ ) by heat treatment (calcination) 1.02 g (0.005 mol) and 10 g of novolac 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).

A passivation material (d2-2) was spin-coated on an 8-inch p-type silicon substrate (8 Ω · cm ~ 12 Ω · cm) with a thickness of 725 μm and a natural oxide film removed by hydrofluoric acid at a concentration of 0.49 mass%. On one side, pre-baking was performed on a hot plate at 120 ° C for 3 minutes. Then, it heated at 650 degreeC for 1 hour in nitrogen atmosphere, and obtained the passivation film containing alumina and tantalum oxide. The film thickness was measured by an ellipsometer, and 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 very weak peak derived from an alkyl group was seen around 1200 cm ^-1 .

Then, on the passivation film, a plurality of aluminum electrodes with a diameter of 1 mm were formed through a metal mask through evaporation to form a metal-insulator-semiconductor (MIS) structure capacitor. The voltage dependency (CV characteristic) of the capacitance of the capacitor was measured with a commercially available prober and an LCR meter (HP Corporation, 4275A). The results show that the flat band voltage (Vfb) moves from -0.81V, which is the ideal value, to -0.43V. From this amount of movement, it is known that the passivation film obtained from the passivation material (d-2) exhibits a fixed charge with a fixed charge density (Nf) of -5.5 × 10 ¹⁰ cm ^-2 and a negative value.

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

From the above, it is known that the passivation film obtained by heat-treating (calcining) the passivation material (d2-2) shows a certain degree of passivation performance and shows a negative fixed charge.

<Case where two or more vanadium group element oxides are used>

[Reference Example 2-8]

A commercially available organometallic thin film coating type material that can obtain alumina (Al ₂ O ₃ ) by heat treatment (calcination) [Institute of High Purity Chemistry (Institute of Chemistry), SYM-AL04, concentration: 2.3% by mass], A commercially available organometallic thin film coating type material that can obtain vanadium oxide (V ₂ O ₅ ) by heat treatment (calcination) [Institute of High Purity Chemistry (Stock), V-02, concentration: 2% by mass], and Commercially available organometallic thin film coating-type material capable of obtaining tantalum oxide (Ta ₂ O ₅ ) by heat treatment (calcination) [Institute of High Purity Chemistry (Stock), Ta-10-P, concentration: 10% by mass] These were mixed to prepare a passivation material (e2-1) as a coating material (see Table 10).

A commercially available organometallic thin film coating type material that can obtain alumina (Al ₂ O ₃ ) by heat treatment (calcination) [Institute of High Purity Chemistry (Institute of Chemistry), SYM-AL04, concentration: 2.3% by mass], A commercially available organometallic thin film coating type material that can obtain vanadium oxide (V ₂ O ₅ ) by heat treatment (calcination) [Institute of High Purity Chemistry (Stock), V-02, concentration: 2% by mass], and A commercially available organometallic film coating type material [Niobium Oxide (Nb-05, Nb-05, concentration: 5 mass%)] can be obtained by heat treatment (calcination) to obtain niobium oxide (Nb ₂ O ₅ ), A passivation material (e2-2) was prepared as a coating material (see Table 10).

A commercially available organometallic thin film coating type material that can obtain alumina (Al ₂ O ₃ ) by heat treatment (calcination) [Institute of High Purity Chemistry (Institute of Chemistry), SYM-AL04, concentration: 2.3% by mass], Commercially available organometallic thin film coating-type material capable of obtaining tantalum oxide (Ta ₂ O ₅ ) by heat treatment (calcination) [Institute of High Purity Chemistry (Stock), Ta-10-P, concentration: 10% by mass] And a commercially available organometallic thin film coating-type material that can obtain niobium oxide (Nb ₂ O ₅ ) by heat treatment (calcination) [Institute of High Purity Chemistry, Inc., Nb-05, concentration: 5% by mass] They were mixed to prepare a passivation material (e2-3) as a coating material (see Table 10).

A commercially available organometallic thin film coating type material that can obtain alumina (Al ₂ O ₃ ) by heat treatment (calcination) [Institute of High Purity Chemistry (Institute of Chemistry), SYM-AL04, concentration: 2.3% by mass], A commercially available organometallic thin film coating type material that can obtain vanadium oxide (V ₂ O ₅ ) by heat treatment (calcination) [Institute of High Purity Chemistry (Stock), V-02, concentration: 2% by mass], A commercially available organometallic film coating type material obtained by heat treatment (calcination) of tantalum oxide (Ta ₂ O ₅ ) [Institute of High Purity Chemistry (Institute of Chemistry), Ta-10-P, concentration: 10% by mass], And a commercially available organometallic thin film coating type material that can obtain niobium oxide (Nb ₂ O ₅ ) by heat treatment (calcination) [Institute of High Purity Chemistry (Institute of Chemical Engineering), Nb-05, concentration: 5% by mass] is mixed A passivation material (e2-4) was prepared as a coating material (see Table 10).

The passivation material (e2-1) to the passivation material (e2-4) were spin-coated in the same manner as in Reference Example 2-1, and the thickness of the natural oxide film was removed in advance by using hydrofluoric acid with a concentration of 0.49% by mass. An 8-inch p-type silicon substrate (8 Ω · cm ~ 12 Ω · cm) on one side was placed on a hot plate and pre-baked at 120 ° C for 3 minutes. Thereafter, a heat treatment (calcination) was performed at 650 ° C. for 1 hour under a nitrogen atmosphere to obtain a passivation film containing alumina and an oxide of two or more vanadium group elements.

The voltage dependence of the capacitance was measured using the obtained passivation film, and a fixed charge density was calculated based on this.

Then, the passivation material (e2-1) to the passivation material (e2-4) were respectively coated on both sides of an 8-inch p-type silicon substrate, and pre-baking was performed at 650 ° C for 1 hour under a nitrogen atmosphere. Heat treatment (calcination), passivation of both sides of the silicon substrate Film covered sample. The carrier life of this sample was measured by a life measuring device (Kobelco Research Institute (Korea), RTA-540).

The obtained results are summarized in Table 10.

Depending on the ratio (mass ratio) of oxides of two or more vanadium group elements to alumina after heat treatment (calcination), the results are different, but passivation using passivation material (e2-1) ~ passivation material (e2-4) After heat treatment (calcination), the film shows a negative fixed charge and the carrier lifetime also shows a certain value. Therefore, it is suggested that the film functions as a passivation film.

[Reference Example 2-9]

As in Reference Example 2-1, a commercially available organometallic thin film coating type material capable of obtaining alumina (Al ₂ O ₃ ) by heat treatment (calcination) [Institute of High Purity Chemistry (Institute of Chemistry), SYM -AL04, concentration: 2.3% by mass], a commercially available organometallic thin film coating type material that can obtain vanadium oxide (V ₂ O ₅ ) by heat treatment (calcination) [Institute of High Purity Chemistry, Inc., V- 02, with a concentration of 2% by mass], or a commercially available organometallic film coating type material that can obtain tantalum oxide (Ta ₂ O ₅ ) by heat treatment (calcination) [Institute of High Purity Chemistry, Inc., Ta- 10-P, with a concentration of 10% by mass], to prepare a passivation material (f2-1) to a passivation material (f2-8) as coating materials (see Table 10).

In addition, a passivation material (f2-9) using alumina alone was prepared (see Table 11).

In the same manner as in Reference Example 2-1, a passivation material (f2-1) to a passivation material (f2-9) were respectively coated on one side of a p-type silicon substrate, and then heat-treated (calcined) to produce a passivation film. Using this passivation film, the voltage dependency of the capacitance was measured, and the fixed charge density was calculated based on this.

Further, in the same manner as in Reference Example 2-1, the passivation material (f2-1) to the passivation material (f2-9) were coated on both sides of a p-type silicon substrate, respectively, and heat-treated (calcined), and the obtained sample was used. To determine the carrier lifetime. The obtained results are summarized in Table 11.

As shown in Table 11, when the alumina / vanadium oxide or tantalum oxide in the passivation material is 90/10 and 80/20, the variation of the fixed charge density value is large, and a negative fixed charge density cannot be obtained stably. However, it was confirmed that a negative fixed charge density can be achieved by using alumina and niobium oxide. It was found that when the measurement was performed by the CV method using a passivation material of alumina / vanadium oxide or tantalum oxide at 90/10 and 80/20, it sometimes became a passivation film showing a positive fixed charge and did not display stably. Negative fixed charge. Furthermore, a passivation film showing a positive fixed charge can be used as a passivation film of an n-type silicon substrate. On the other hand, the passivation material (f2-9) whose alumina reaches 100% by mass cannot obtain a negative Fixed charge density.

[Reference Example 2-10]

A single-crystal silicon substrate using boron as a dopant was used as the silicon substrate 101 to produce a solar cell element having a structure shown in FIG. 12. After the surface of the silicon substrate 101 is textured, a coating-type phosphorus diffusion material is applied to the light-receiving surface side, and a diffusion layer 102 (phosphorus diffusion layer) is formed by heat treatment. After that, the coating-type phosphorus diffusion material was removed by dilute hydrofluoric acid.

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

Next, on a light receiving surface antireflection film 103 (SiN film) formed on the light receiving surface side of the silicon substrate 101, a paste having silver as a main component is screen-printed in a predetermined shape of a finger electrode and a bus bar electrode. On the back side, a paste screen containing aluminum as a main component is printed on the entire surface. Thereafter, heat treatment (burn-through) was performed at 850 ° C. to form electrodes (first electrode 105 and second electrode 106), and aluminum was diffused into the opening portion OA on the back surface to form a BSF layer 104 to form FIG. 12. The solar cell element of the structure shown.

In addition, the formation of the silver electrode on the light-receiving surface here describes the firing step without opening holes in the SiN film. However, the opening portion OA may be formed in the SiN film by etching or the like in advance, and then the silver electrode is formed. .

For comparison, in the above manufacturing steps, the passivation film 107 is not formed, but an aluminum paste is printed on the entire surface of the back side, and a p ⁺ layer 114 corresponding to the BSF layer 104 and a second electrode are formed on the entire surface. The corresponding electrode 116 forms a solar cell element having the structure shown in FIG. 9. The solar cell elements were evaluated for characteristics (short-circuit current, open-circuit voltage, curve factor, and conversion efficiency). The characteristic evaluation was measured based on JIS-C-8913 (2005) and JIS-C-8914 (2005). The results are shown in Table 12.

Table 12 shows that compared with a solar cell element without a passivation film 107, a short-circuit current and an open-circuit voltage are both increased, and the conversion efficiency (photoelectric conversion efficiency) is increased by a maximum of 0.6%.

All the contents disclosed in Japanese Patent Application No. 2012-160336, Japanese Patent Application No. 2013-011934, Japanese Patent Application No. 2013-040153, and Japanese Patent Application No. 2013-040155 are incorporated by reference To this manual. All documents, Japanese patent applications, and technical standards described in this specification are incorporated into this specification by reference in the same manner as the following cases. The above cases are specific and separately described. Where standards are incorporated by reference.

10‧‧‧p-type semiconductor substrate

11‧‧‧n-type diffusion region forming composition

Calcined composition of 12‧‧‧n-type diffusion region forming composition

13‧‧‧The first n-type diffusion area

14‧‧‧PSG layer

15‧‧‧second n-type diffusion region

16‧‧‧p-type diffusion region forming composition

16'‧‧‧p-type diffusion region forming composition

17‧‧‧p ⁺ type diffusion area

18‧‧‧Anti-reflective film

19‧‧‧ passivation layer

20‧‧‧ light receiving electrode

21‧‧‧Back electrode

Claims (14)

A solar cell element includes a semiconductor substrate having a light receiving surface and a back surface opposite to the light receiving surface; a first impurity diffusion region disposed on a part of the light receiving surface and diffusing impurities; and a second impurity diffusion region disposed on The light receiving surface, and the impurity concentration is lower than the first impurity diffusion region; the light receiving surface electrode is disposed on at least a part of the first impurity diffusion region; the back electrode is disposed on the back surface; and the passivation layer is disposed on the light receiving surface and At least one side of the back surface, and contains 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 ; the passivation layer is a passivation layer A heat-treated product of a composition for forming, the composition for forming a passivation layer comprising: a material 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 the following general formula (I) One or more of the group consisting of the compound represented by the compound and one or more aluminum compounds selected from the group consisting of Al ₂ O ₃ and the compound represented by the following general formula (II); group The total content of 0.1 mass% to 80 mass% of the aluminum in the compound _{^{thereof; M (OR 1) m (}} I) [ the formula, M is selected from the group consisting of containing Nb, the group consisting of Ta, V, Y and Hf At least one kind of metal element; 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 1 to 5]; [Wherein 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 ³ each independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms]. The solar cell element according to item 1 of the patent application scope, wherein the passivation layer further contains Al ₂ O ₃ . The solar cell element according to item 1 or item 2 of the scope of patent application, wherein the density of the passivation layer is 1.0 g / cm ³ to 10.0 g / cm ³ . The solar cell element according to item 1 or item 2 of the scope of patent application, wherein the average thickness of the passivation layer is 5 nm to 50 μm. The solar cell element according to item 1 or item 2 of the scope of patent application, wherein in the general formula (11), R ^{2 is} independently an alkyl group having 1 to 4 carbon atoms. The solar cell element according to item 1 or item 2 of the scope of patent application, wherein in the general formula (II), n is an integer of 1 to 3, and R ^{5 is} each independently a hydrogen atom or a carbon number of 4 or 5 alkyl. The solar cell element according to claim 1 or claim 2, wherein the composition for forming a passivation layer contains a member selected from the group consisting of Nb ₂ O ₅ and a compound in which M is Nb in the general formula (I). One or more niobium compounds in the group, and the total content of the niobium compound in the composition for forming a passivation layer is 0.1 to 99.9% by mass in terms of Nb ₂ O ₅ conversion. The solar cell element according to claim 1 or claim 2, wherein the composition for forming a passivation layer contains a liquid medium. The solar cell element according to item 8 of the scope of patent application, wherein the liquid medium contains a group 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 At least one of. A method for manufacturing a solar cell element, which is the method for manufacturing a solar cell element according to any one of claims 1 to 9 of a patent application scope, comprising: a light-receiving surface and a back surface opposite to the light-receiving surface; A step of forming a first impurity diffusion region on a part of the light receiving surface of the semiconductor substrate; forming a second impurity diffusion region with an impurity concentration lower than the first impurity diffusion region on the light receiving surface; A step of forming at least a part of a light-receiving surface electrode; a step of forming a back-surface electrode on the back surface; and providing a composition for forming a passivation layer on at least one surface selected from the group consisting of the light-receiving surface and the back surface to form a composition A step of forming a layer, wherein the composition for forming a passivation layer contains a compound 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) One or more selected from the group consisting of: and heat-treating the composition layer to form a composition 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 A step of one or more passivation layers in the group of M, M (OR ¹ ) _m (I) [where 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 1 to 5]. The method for manufacturing a solar cell element according to claim 10, wherein the composition for forming a passivation layer further contains a group selected from the group consisting of Al ₂ O ₃ and a compound represented by the following general formula (II) More than one of the aluminum compounds, [Wherein 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 represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms]. The method for manufacturing a solar cell element according to item 10 or item 11 of the scope of patent application, wherein the temperature of the heat treatment is 400 ° C or higher. The method for manufacturing a solar cell element according to claim 10 or claim 11, 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 solar cell module includes the solar cell element according to any one of items 1 to 9 of the scope of patent application, and a wiring material disposed on an electrode of the solar cell element.