JP6295952B2 - SOLAR CELL DEVICE, ITS MANUFACTURING METHOD, AND SOLAR CELL MODULE - Google Patents

Description

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

The manufacturing process of the conventional silicon solar cell element is demonstrated.
First, a p-type silicon substrate having a texture structure formed on the light-receiving surface side is prepared so as to promote the light confinement effect and increase the efficiency, and then in a mixed gas atmosphere of phosphorus oxychloride (POCl ₃ ), nitrogen and oxygen An n-type diffusion layer is uniformly formed by performing several tens of minutes at 800 ° C. to 900 ° C. In this conventional method, since phosphorus is diffused using a mixed gas, n-type diffusion layers are formed not only on the front surface, which is the light receiving surface, but also on the side surface and the back surface. Therefore, side etching is performed to remove the n-type diffusion layer formed on the side surface. Further, the n-type diffusion layer formed on the back surface needs to be converted into a p ⁺ -type diffusion layer. Therefore, aluminum powder on the entire back surface, glass frit, an aluminum paste applied containing a dispersion medium and organic binder and the like, by forming an aluminum electrode which heat treatment (firing) to the n-type diffusion layer p ⁺ In addition, an ohmic contact is obtained in the mold diffusion layer.

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

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

In relation to the above, a point contact method has been proposed in which an aluminum paste is applied to a part of the surface of a silicon substrate to partially form a p ⁺ -type diffusion layer and an aluminum electrode (for example, Japanese Patent No. 3107287). See the official gazette).
In the case of 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 rate of minority carriers on the surface of the portion other than the aluminum electrode. For this purpose, a SiO ₂ layer or the like has been proposed as a backside semiconductor substrate passivation layer (hereinafter also simply referred to as “passivation layer”) (see, for example, Japanese Patent Application Laid-Open No. 2004-6565). As a passivation effect by forming the SiO ₂ layer, there is an effect of terminating the dangling bonds of silicon atoms in the surface layer portion on the back surface of the silicon substrate, and reducing the surface state density that causes recombination.

As another method of suppressing recombination of minority carriers, there is a method of reducing the minority carrier density by an electric field that generates fixed charges in the passivation layer. Such a passivation effect is generally called a field effect, and aluminum oxide (Al ₂ O ₃ ) or the like has been proposed as a material having a negative fixed charge (see, for example, Japanese Patent No. 4767110).

  Such a passivation layer is generally formed by a method such as an ALD (Atomic Layer Deposition) method or a CVD (Chemical Vapor Deposition) method (for example, Journal of Applied Physics, 104 (2008), 113703-1). 113703-7). As a simple method for forming an aluminum oxide layer on a semiconductor substrate, a sol-gel method has been proposed (for example, Thin Solid Films, 517 (2009), 6327-6330, Chinese Physics Letters, 26 (2009)). , 088102-1 to 088102-4).

  Since the technique described in Journal of Applied Physics, 104 (2008), 113703-1 to 113703-7 includes a complicated manufacturing process such as vapor deposition, it may be difficult to improve productivity. In addition, the composition for forming a passivation layer used in the method described in Thin Solid Films, 517 (2009), 6327-6330 Chinese Physics Letters, 26 (2009), 088102-1 to 088102-4 has problems such as gelation over time. It is difficult to say that the storage stability is sufficient. Further, there has not been sufficiently studied to form a passivation layer having an excellent passivation effect using an oxide containing a metal element other than aluminum.

  The present invention has been made in view of the above-described conventional problems, has a high conversion efficiency, a solar cell element in which deterioration of solar cell characteristics over time is suppressed, a simple manufacturing method thereof, and an excellent It is an object of the present invention to provide a solar cell module having high conversion efficiency and capable of suppressing deterioration of solar cell characteristics over time.

Specific means for solving the above problems are as follows.
<1> a semiconductor substrate having a light-receiving surface and a back surface opposite to the light-receiving surface, and having a p-type diffusion region containing a p-type impurity and an n-type diffusion region containing an n-type impurity on the back surface;
Provided in part or all of the back surface of the semiconductor substrate, containing 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 A passivation layer to
A first metal electrode provided in at least a part of the p-type diffusion region;
And a second metal electrode provided in at least a part of the n-type diffusion region.

<2> The p-type diffusion region and the n-type diffusion region are spaced apart from each other, and each has a plurality of rectangular portions having short sides and long sides,
The plurality of rectangular portions of the p-type diffusion region are arranged such that the long sides of the plurality of rectangular portions are along the long sides of the plurality of rectangular portions of the n-type diffusion region,
The solar cell element according to <1> , wherein the plurality of rectangular portions included in the p-type diffusion region and the plurality of rectangular portions included in the n-type diffusion region are alternately arranged.

<3> The solar cell element according to <1> or <2>, wherein the solar cell element has a back contact structure.

<4> The solar cell element according to any one of <1> to <3>, wherein the passivation layer further contains Al ₂ O ₃ .

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

<6> The composition for forming a passivation layer is composed of Nb ₂ O ₅ , Ta ₂ O ₅ , V ₂ O ₅ , Y ₂ O ₃ , HfO ₂ and a compound represented by the following general formula (I). The solar cell element according to <5>, including one or more selected.
M (OR ¹ ) m (I)
[Wherein M includes 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. ]

<7> the passivation layer forming composition further comprises Al ₂ O ₃ and one or more aluminum compounds selected from the group consisting of compounds represented by the following formula (II), according to <6> Solar cell element.

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

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

<9> In the general formula (II), <7> or <8>, wherein n is an integer of 1 to 3, and R ⁵ is independently a hydrogen atom or an alkyl group having 4 or 5 carbon atoms. The solar cell element described.

<10> The composition for forming a passivation layer includes at least one aluminum compound selected from the group consisting of Al ₂ O ₃ and the aluminum compound, and the inclusion of the aluminum compound in the composition for forming a passivation layer Solar cell element as described in any one of <7>-<9> whose rate is 0.1 mass%-80 mass%.

<11> The passivation layer forming composition includes Nb ₂ O ₅ and one or more niobium compounds selected from the group consisting of compounds in which M is Nb in the general formula (I), and the passivation layer is formed. The solar cell according to any one of <6> to <9>, wherein the total content of the niobium compound in the composition for use is 0.1% by mass to 99.9% by mass in terms of Nb ₂ O _5. element.

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

<13> The solar cell element according to <12>, wherein the liquid medium includes at least one selected from the group consisting of a hydrophobic organic solvent, an aprotic organic solvent, a terpene solvent, an ester solvent, an ether solvent, and an alcohol solvent.

<14> The density of the passivation layer is ^{1.0g / cm 3 ~10.0g / cm 3} , <1> ~ solar cell device according to any one of <13>.

<15> The solar cell element according to any one of <1> to <14>, wherein an average thickness of the passivation layer is 5 nm to 50 μm.

<16> A first metal in at least a part of the p-type diffusion region of the semiconductor substrate having a light-receiving surface and a back surface opposite to the light-receiving surface, and having a p-type diffusion region and an n-type diffusion region on the back surface. Forming a second metal electrode on at least a part of the n-type diffusion region; and
A part or all of the back surface of the semiconductor substrate is made 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). Providing a composition for forming a passivation layer containing at least one selected from the group to form a composition layer;
Heat-treating the composition layer to form a passivation layer 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 ; The manufacturing method of the solar cell element of any one of <1>-<15> which has these.
M (OR ¹ ) m (I)

In the formula, M includes 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.

<17> The solar cell according to <16>, wherein the composition for forming a passivation layer further includes at least one selected from the group consisting of compounds represented by Al ₂ O ₃ and the following general formula (II). Device manufacturing method.

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

<18> The method for producing a solar cell element according to <16> or <17>, wherein the temperature of the heat treatment is 400 ° C. or higher.

<19> The process according to any one of <16> to <18>, wherein the step of forming the composition layer includes applying the composition for forming a passivation layer by a screen printing method or an inkjet method. A battery element manufacturing method.

<20> A solar cell module comprising the solar cell element according to any one of <1> to <15> and a wiring material disposed on an electrode of the solar cell element.

  ADVANTAGE OF THE INVENTION According to this invention, it has the outstanding conversion efficiency, the solar cell element by which the fall of the solar cell characteristic with time is suppressed, its simple manufacturing method, and the solar cell which has the outstanding conversion efficiency, and with time It is possible to provide a solar cell module in which deterioration of characteristics is suppressed.

It is a top view which shows typically an example of the back surface electrode structure of the solar cell element which has the back contact structure concerning this embodiment. It is sectional drawing which shows typically an example of the manufacturing method of the solar cell element which has the back contact structure concerning this embodiment. It is sectional drawing which shows typically another example of the solar cell element which has the back contact structure concerning this embodiment. It is sectional drawing which shows typically an example of the solar cell element which has the via-hole type back contact structure concerning this embodiment. It is a top view which shows typically an example of the back surface electrode structure of the solar cell element which has the via-hole type back contact structure concerning this embodiment. It is sectional drawing which showed the structure of the double-sided electrode type solar cell element. It is sectional drawing which shows the 1st structural example of the solar cell element concerning reference embodiment. It is sectional drawing which shows the 2nd structural example of the solar cell element concerning reference embodiment. It is sectional drawing which shows the 3rd structural example of the solar cell element concerning reference embodiment. It is sectional drawing which shows the 4th structural example of the solar cell element concerning reference embodiment. It is sectional drawing which shows another structural example of the solar cell element concerning reference embodiment.

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

<Solar cell element>
The solar cell element of the present invention has a light receiving surface and a back surface opposite to the light receiving surface, a semiconductor substrate having a p-type diffusion region and an n-type diffusion region on the back surface, and a part of the back surface of the semiconductor substrate. Or 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 (hereinafter referred to as “specific metal oxide”). A passivation layer containing a metal element included in each metal oxide), a first metal electrode provided in at least a part of the p-type diffusion region, and the n-type And a second metal electrode provided on at least a part of the diffusion region.

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

  The reason why a solar cell element having a passivation layer containing an electrode and 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. it can. That is, the specific metal oxide is a compound having a fixed charge. It can be considered that the presence of a compound having a fixed charge on the surface of the semiconductor substrate causes band bending and suppresses carrier recombination. Further, even if the compound has a small fixed charge or does not have a fixed charge, it may have a passivation effect such as having 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 CV method (Capacitance Voltage Measurement). When the surface state density of a passivation layer formed by heat-treating a composition for forming a passivation layer, which will be described later, is evaluated by a CV method, the value is larger than that of a passivation layer formed by an ALD method or a CVD method. There is. However, the passivation layer included in the solar cell element of the present invention has a large electric field effect, and the concentration of minority carriers is reduced, and the surface lifetime τ _s is increased. Therefore, the surface state density is not a relative problem.

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

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

  The solar cell element includes a semiconductor substrate having a light receiving surface and a back surface opposite to the light receiving surface, and having a p-type diffusion region and an n-type diffusion region on the back surface. Examples of the semiconductor substrate include those obtained by doping (diffusing) p-type impurities or n-type impurities into silicon, germanium, or the like. The semiconductor substrate may be a p-type semiconductor substrate or an n-type semiconductor substrate.

  The thickness in particular of a semiconductor substrate is not restrict | limited, According to the objective, it can select suitably. 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, and can be, for example, a square having a side of 125 mm to 156 mm.

  The semiconductor substrate has a p-type diffusion region and an n-type diffusion region on the back surface. The shape and size of the p-type diffusion region and the n-type diffusion region are not particularly limited and can be appropriately selected according to the purpose. The p-type diffusion region and the n-type diffusion region are preferably arranged apart from each other.

  The number and shape of the p-type diffusion region and the n-type diffusion region are not particularly limited as long as the effect and the shape of the present invention are achieved. For example, the p-type diffusion region and the n-type diffusion region preferably have a plurality of rectangular portions each having a long side and a short side. Note that the short side and the long side of the rectangular portion may each be a straight line or may include a non-straight part.

  When the p-type diffusion region and the n-type diffusion region have a plurality of rectangular portions each having a long side and a short side, the arrangement of the rectangular portion of the p-type diffusion region and the rectangular portion of the n-type diffusion region is particularly limited. However, it can be appropriately selected depending on the purpose. For example, the plurality of rectangular portions included in the p-type diffusion region are arranged such that the long sides of the plurality of rectangular portions are aligned with the long sides of the plurality of rectangular portions included in the n-type diffusion region. It is preferable that the rectangular portions of the plurality of p-type diffusion regions and the rectangular portions of the plurality of n-type diffusion regions are arranged alternately.

  When the p-type diffusion region and the n-type diffusion region have a plurality of rectangular portions each having a long side and a short side, the plurality of rectangular portions of the p-type diffusion region may be connected. For example, you may connect with the rectangular p-type diffusion area | region arrange | positioned so that the end of the long side direction of the several rectangular part of a p-type diffusion area | region may contact | connect. Similarly, a plurality of rectangular portions of the n-type diffusion region may be connected. For example, you may connect with the rectangular n-type diffusion area | region arrange | positioned so that the end of the long side direction of the several rectangular part of an n-type diffusion area | region may contact | connect.

FIG. 1 is a plan view schematically showing an example of the shape and arrangement of a p-type diffusion region and an n-type diffusion region provided on the back surface of a semiconductor substrate.
As shown in FIG. 1, the p-type diffusion region 14 is spaced apart from the n-type diffusion region 12. The p-type diffusion region 14 has a plurality of rectangular portions having short sides 14a and long sides 14b, and the plurality of rectangular portions are rectangular p-types arranged at one end in the direction of each long side 14b. The diffusion regions 14c are connected.
The n-type diffusion region 12 also has a plurality of rectangular portions having a short side 12a and a long side 12b, and the plurality of rectangular portions are rectangular n-type diffusions arranged at one end in the direction of each long side 12b. They are connected in the region 12c.
In FIG. 1, the rectangular portion 14 c connecting the plurality of rectangular portions of the p-type diffusion region 14 is opposite to the rectangular portion 12 c connecting the plurality of rectangular portions of the n-type diffusion region 12 when viewed in the long side direction. Arranged on the side. Accordingly, the plurality of rectangular portions of the p-type diffusion region 14 and the plurality of rectangular portions of the n-type diffusion region 12 are connected to each other while the plurality of rectangular portions of the p-type diffusion region 14 and the plurality of rectangular portions of the n-type diffusion region 12 are connected to each other. The parts can be arranged alternately. Such a back electrode structure is also referred to as “intersecting finger type”. Moreover, a back contact type solar cell element is mentioned as a solar cell element which has a structure shown in FIG.

When the semiconductor substrate having the p-type diffusion region and the n-type diffusion region on the back surface is a p-type semiconductor substrate, the concentration of the p-type impurity contained in the p-type diffusion region is as follows from the viewpoint of conversion efficiency and lifetime extension of carriers. The concentration is preferably higher than the concentration of the p-type impurity originally contained in the p-type semiconductor substrate. For example, the concentration of the p-type impurity contained in the p-type diffusion region is 10 ¹⁸ atoms / cm ³ or more, and the concentration of the p-type impurity contained originally in the p-type semiconductor substrate is 10 ⁵ atoms / cm ³ or more and 10 ^17. preferably atoms / cm ³ or less, the concentration of the p-type impurity contained in the p-type diffusion region is at ¹⁰ 19 atoms / cm ³ or more ¹⁰ 22 atoms / cm ^3, originally contained in the p-type semiconductor substrate More preferably, the concentration of the p-type impurity is 10 ¹⁰ atoms / cm ³ or more and 10 ¹⁶ atoms / cm ³ or less.

When the semiconductor substrate having the p-type diffusion region and the n-type diffusion region on the back surface is an n-type semiconductor substrate, the concentration of the n-type impurity contained in the n-type diffusion region is from the viewpoint of conversion efficiency and long life of carriers. The concentration is preferably higher than the concentration of the n-type impurity originally contained in the n-type semiconductor substrate. For example, the concentration of the n-type impurity contained in the n-type diffusion region is 10 ¹⁸ atoms / cm ³ or more, and the concentration of the n-type impurity originally contained in the n-type semiconductor substrate is 10 ⁵ atoms / cm ³ or more and 10 ^17. preferably atoms / cm ³ or less, the concentration of the n-type impurity contained in the n-type diffusion region is at ¹⁰ 19 atoms / cm ³ or more ¹⁰ 22 atoms / cm ^3, originally contained in the n-type semiconductor substrate More preferably, the concentration of the n-type impurity is 10 ¹⁰ atoms / cm ³ or more and 10 ¹⁶ atoms / cm ³ or less.

  A first metal electrode is provided on at least a part of the p-type diffusion region on the back surface of the semiconductor substrate, and a second metal electrode is provided on at least a part of the n-type diffusion region. The material of the first metal electrode and the second metal electrode is not particularly limited, and examples thereof include silver, copper, and aluminum. The thicknesses of the first metal electrode and the second metal electrode are not particularly limited, and are preferably 0.1 μm to 50 μm from the viewpoint of conductivity and homogeneity.

The shape and size of the first metal electrode are not particularly limited. For example, the size of the region where the first metal electrode is formed is preferably 50% or more and more preferably 80% or more in the entire area of the p-type diffusion region.
The shape and size of the second metal electrode are not particularly limited. For example, the size of the region where the second metal electrode is formed is preferably 50% or more, and more preferably 80% or more in the entire area of the n-type diffusion region.

The first metal electrode preferably contains aluminum from the viewpoint of forming an electrode and forming a p ⁺ -type diffusion layer by diffusing aluminum atoms in the semiconductor substrate, and the thickness thereof is 0.1 μm to 50 μm. It is preferable that
The first metal electrode and the second metal electrode can be produced by a commonly used method. For example, it can be manufactured by applying an electrode forming paste such as a silver paste, an aluminum paste, or a copper paste to a desired region of a semiconductor substrate and performing a heat treatment as necessary.

  The solar cell element may further include an electrode that collects current on the light receiving surface of the semiconductor substrate as necessary. The material, shape, and thickness of the electrode that collects current on the light receiving surface are not particularly limited, and examples thereof include a silver electrode, a copper electrode, and an aluminum electrode, and the thickness is preferably 0.1 μm to 50 μm. The electrode provided on the light receiving surface may be connected to the first metal electrode or the second metal electrode on the back surface through a through-hole electrode penetrating the semiconductor substrate. The electrode provided on the light receiving surface can be produced by a commonly used method. For example, it can be manufactured by applying an electrode forming paste such as a silver paste, an aluminum paste, or a copper paste to a desired region of a semiconductor substrate and performing a heat treatment as necessary.

The solar cell element of this invention has the passivation layer containing a specific metal oxide in the one part or all area | region of the back surface of a semiconductor substrate.
When the passivation layer is provided in a partial region on the back surface of the semiconductor substrate, the passivation layer is preferably provided in 50% or more of the region area on the back surface of the semiconductor substrate, and more preferably in 80% or more.
Further, for example, the passivation layer may be provided on part or all of the side surface of the semiconductor substrate in addition to the back surface of the semiconductor substrate, or may be provided on part or all of the light receiving surface.

  The shape and size in the surface direction of the region where the passivation layer is formed on the back surface of the semiconductor substrate are not particularly limited and can be appropriately selected according to the purpose and the like. When the passivation layer is formed on a part of the back surface of the semiconductor substrate, for example, at least the passivation layer is formed in a part or all of the region other than the region where the first metal electrode and the second metal electrode are formed. It is preferable that at least a passivation layer is formed in all regions other than the region where the first metal electrode and the second metal electrode are formed.

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

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

The passivation layer may further contain a metal oxide other than the specific metal oxide. As such a metal oxide, a compound having a fixed charge like the specific metal oxide is preferable. Aluminum oxide, silicon oxide, titanium oxide, gallium oxide, zirconium oxide, boron oxide, indium oxide, phosphorus oxide, zinc oxide Lanthanum oxide, praseodymium oxide, neodymium oxide, promethium oxide, samarium oxide, europium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, lutetium oxide, and the like. The metal oxides other than the particular metal oxide passivation layer comprises aluminum oxide from the viewpoint of obtaining a high passivation effect and stable passivation effect, silicon oxide, titanium oxide, zirconium oxide and neodymium oxide, more aluminum oxide preferable.

  In the case where the passivation layer contains a metal oxide other than the specific metal oxide, the content is preferably 99.9% by mass or less, more preferably 80% by mass or less of the passivation layer. The content rate of metal oxides 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 a passivation layer>
It is preferable that the passivation layer of the solar cell element of the present invention is a heat-treated product of the composition for forming a passivation layer. The composition for forming a passivation layer is not particularly limited as long as it can form a passivation layer containing a specific metal oxide by heat treatment. Even if it contains the specific metal oxide itself, the metal containing the specific metal element A precursor of a specific metal oxide such as alkoxide may be included. 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 includes 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.

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

In general formula (I), each R ¹ independently represents an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 14 carbon atoms, and an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 9 carbon atoms. It is preferable that 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, t-butyl, pentyl, hexyl, and heptyl groups. Octyl group, 2-ethylhexyl group, 3-ethylhexyl group, phenyl group 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, and examples of the substituent of the alkyl group include a halogen atom, an amino group, a hydroxyl group, a carboxyl group, a sulfone group, and a nitro group. Can be mentioned. Examples of the substituent for the aryl group include a halogen atom, a methyl group, an ethyl group, an isopropyl group, an amino group, a hydroxyl group, a carboxyl group, a sulfone group, and a nitro group.
Among these, R ¹ is preferably an unsubstituted alkyl group having 1 to 8 carbon atoms, and more preferably an unsubstituted alkyl group having 1 to 4 carbon atoms, from the viewpoint of storage stability and a passivation effect.

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

In the compound represented by the general formula (I), M is preferably Nb, Ta or Y from the viewpoint of the passivation effect, and R ¹ has ¹ to 4 carbon atoms from the viewpoint of storage stability and the passivation effect. It is more preferably an unsubstituted alkyl group, and m is preferably an integer of 1 to 5 from the viewpoint of storage stability. From the viewpoint of making the fixed charge density of the passivation layer negative, M preferably contains at least one metal element selected from the group consisting of Nb, Ta, V, and Hf, and Nb, Ta, VO And at least one selected from the group consisting of Hf.

  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 represented by the general formula (II) described later, the compound of the formula (I) may be a liquid. preferable.

  Compounds of formula (I) include niobium methoxide, niobium ethoxide, niobium isopropoxide, niobium n-propoxide, niobium n-butoxide, niobium t-butoxide, niobium isobutoxide, tantalum methoxide, tantalum ethoxide, tantalum Isopropoxide, tantalum n-propoxide, tantalum n-butoxide, tantalum t-butoxide, tantalum isobutoxide, yttrium methoxide, yttrium ethoxide, yttrium isopropoxide, yttrium n-propoxide, yttrium n-butoxide, yttrium t -Butoxide, yttrium isobutoxide, vanadium methoxide oxide, vanadium ethoxide oxide, vanadium isopropoxide oxide, vanadium n-propoxide oxide, vana Um n-butoxide oxide, vanadium t-butoxide oxide, vanadium isobutoxide oxide, hafnium methoxide, hafnium ethoxide, hafnium isopropoxide, hafnium n-propoxide, hafnium n-butoxide, hafnium t-butoxide, hafnium isobutoxide, etc. Among them, niobium ethoxide, niobium n-propoxide, niobium n-butoxide, tantalum ethoxide, tantalum n-propoxide, tantalum n-butoxide, yttrium isopropoxide and yttrium n-butoxide are preferable. From the viewpoint of obtaining a negative fixed charge density, niobium ethoxide, niobium n-propoxide, niobium n-butoxide, tantalum ethoxide, tantalum n-propoxide, tantalum n-butoxide, vanadium ethoxide oxide, vanadium n-propoxy Preference is given to oxides, vanadium n-butoxide oxide, hafnium ethoxide, hafnium n-propoxide and hafnium n-butoxide.

  As the compound of formula (I), a prepared product or a commercially available product may be used. Commercially available products include, for example, pentamethoxyniobium, pentaethoxyniobium, penta-i-propoxyniobium, penta-n-propoxyniobium, penta-i-butoxyniobium, penta-n-butoxyniobium, penta 2-butoxy niobium, pentamethoxy tantalum, pentaethoxy tantalum, penta-i-propoxy tantalum, penta-n-propoxy tantalum, penta-i-butoxy tantalum, penta-n-butoxy tantalum, penta-2-butoxy tantalum, penta T-butoxy tantalum, vanadium (V) trimethoxide oxide, vanadium (V) triethoxy oxide, vanadium (V) tri-i-propoxide oxide, vanadium (V) tri-n-propoxide oxide, vanadium (V ) Tri-i-but Sid oxide, vanadium (V) tri-n-butoxide oxide, vanadium (V) tri-2-butoxide oxide, vanadium (V) tri-t-butoxide oxide, tri-i-propoxy yttrium, tri-n-butoxy yttrium, tetra Methoxyhafnium, tetraethoxyhafnium, tetra-i-propoxyhafnium, tetra-t-butoxyhafnium; pentaethoxyniobium, pentaethoxytantalum, pentabutoxytantalum, yttrium-n-butoxide, hafnium-t-butoxide from Hokuko Chemical Co., Ltd. ; Vanadium oxytriethoxide, vanadium oxytri-normal propoxide, vanadium oxytri-normal butoxide, vanadium oxytriisobutoxide, vanadium from Nichia Corporation It can be given beam oxy tri secondary butoxide and the like.

  When preparing the compound of formula (I), the preparation method includes reacting a halide of the metal element (M) contained in the compound of formula (I) with an alcohol in the presence of an inert organic solvent, and further adding halogen. Known methods such as a method of adding ammonia or an amine compound for extraction (see, for example, JP-A Nos. 63-227593 and 3-291247) can be used.

  The content rate of the compound of Formula (I) contained in the said composition for formation of a passivation layer can be suitably selected as needed. The content of the compound of formula (I) can be 0.1% by mass to 80% by mass in the composition for forming a passivation layer from the viewpoint of storage stability and a passivation effect, and 0.5% by mass to 70% by mass. The mass is preferably 1% by mass, more preferably 1% by mass to 60% by mass, and still more preferably 1% by mass to 50% by mass.

  When the composition for forming a passivation layer contains the compound of formula (I), a chelating reagent (chelating agent) may be added. As a chelating reagent, dicarboxylic acid compounds such as EDTA (ethylenediaminetetraacetic acid), bipyridine, heme, naphthyridine, benzimidazolylmethylamine, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, tartaric acid, maleic acid, phthalic acid, etc. , Β-diketone compounds, β-ketoester compounds, and malonic acid diester compounds. From the viewpoint of chemical stability, β-diketone compounds and β-ketoester compounds are preferred.

  Specific examples of the β-diketone compound include acetylacetone, 3-methyl-2,4-pentanedione, 2,3-pentanedione, 3-ethyl-2,4-pentanedione, and 3-butyl-2,4-pentane. Examples include dione, 2,2,6,6-tetramethyl-3,5-heptanedione, 2,6-dimethyl-3,5-heptanedione, 6-methyl-2,4-heptanedione, and the like.

  Specific examples of β-ketoester compounds include methyl acetoacetate, ethyl acetoacetate, propyl acetoacetate, isobutyl acetoacetate, butyl acetoacetate, t-butyl acetoacetate, pentyl acetoacetate, isopentyl acetoacetate, hexyl acetoacetate, acetoacetic acid n-octyl, heptyl acetoacetate, 3-pentyl acetoacetate, ethyl 2-acetylheptanoate, ethyl 2-butylacetoacetate, ethyl 4,4-dimethyl-3-oxovalerate, ethyl 4-methyl-3-oxovalerate , Ethyl 2-ethylacetoacetate, ethyl hexylacetoacetate, methyl 4-methyl-3-oxovalerate, isopropyl acetoacetate, ethyl 3-oxohexanoate, ethyl 3-oxovalerate, methyl 3-oxovalerate, 3- Methyl oxohexanoate, 2-methylacetoacetate Le, ethyl 3-oxo heptanoic acid, 3-oxo heptanoic acid methyl, can be mentioned 4,4-dimethyl-3-oxo-valerate, such as methyl.

  Specific examples of the malonic acid diester compound include dimethyl malonate, diethyl malonate, dipropyl malonate, diisopropyl malonate, dibutyl malonate, di-t-butyl malonate, dihexyl malonate, t-butylethyl malonate, and methylmalon. Examples include diethyl acid, diethyl ethylmalonate, diethyl isopropylmalonate, diethyl butylmalonate, diethyl 2-butylmalonate, diethyl isobutylmalonate, diethyl 1-methylbutylmalonate, and the like.

  When the compound of formula (I) has a chelate structure, the presence of the chelate structure can be confirmed by a commonly used analytical method. For example, it can be confirmed using an infrared spectrum, a nuclear magnetic resonance spectrum, a melting point, or the like.

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

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

  The composition for forming a passivation layer may further contain a metal oxide other than the specific metal compound or a precursor thereof. Examples of such metal oxides or precursors thereof include aluminum oxide, silicon oxide, titanium oxide, gallium oxide, zirconium oxide, boron oxide, indium oxide, phosphorus oxide, zinc oxide, lanthanum oxide, praseodymium oxide, neodymium oxide, and oxidation. Mention may be made of promethium, samarium oxide, europium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, lutetium oxide, and precursors thereof. From the viewpoint of the stability of the passivation effect, aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, neodymium oxide or a precursor thereof is preferable, and from the viewpoint of a high passivation effect, aluminum oxide or a precursor thereof is more preferable. .

  It is preferable that the said composition for passivation layer formation contains 1 or more types selected from the group which consists of aluminum oxide and its precursor further in addition to a specific metal compound. As a precursor of aluminum oxide, a compound represented by the following general formula (II) (hereinafter also referred to as an organoaluminum compound) is preferable.

The organoaluminum compound is a compound called aluminum alkoxide, aluminum chelate or the like. As described in Nippon Seramikkusu Kyokai Gakuju u tsunbunshi, 97 (1989) 369-399, the organoaluminum compound becomes aluminum oxide (Al ₂ O ₃ ) by heat treatment.

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

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

In general formula (II), n represents an integer of 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, at least one of X ² and X ³ is preferably an oxygen atom.

In general formula (II), R < ³ >, R < ⁴ > and R < ⁵ > represent a hydrogen atom or a C1-C8 alkyl group each independently. 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 a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a 2-butyl group, a t-butyl group, and a hexyl group. Octyl group, 2-ethylhexyl group and the like. Among these, from the viewpoint of storage stability and a passivation effect, R ³ and R ⁴ in the general formula (II) are preferably each independently a hydrogen atom or an unsubstituted alkyl group having 1 to 8 carbon atoms. Or it is more preferable that it is a C1-C4 unsubstituted alkyl group.
R ⁵ in the general formula (II) is preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 8 carbon atoms from the viewpoint of storage stability and a passivation effect, and is a hydrogen atom or 1 to 4 carbon atoms. It is more preferably an unsubstituted alkyl group.

In the organoaluminum compound represented by the general formula (II), n is an integer of 1 to 3 from the viewpoint of storage stability, and R ⁵ is independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. A certain compound is preferable.

The organoaluminum compound represented by the general formula (II) is a compound in which n is 0 and R ² is each independently an alkyl group having 1 to 4 carbon atoms from the viewpoint of storage stability and a passivation effect, n is 1 to 3, R ² is each independently an alkyl group having 1 to 4 carbon atoms, at least one of X ² and X ³ is an oxygen atom, and R ³ and R ⁴ are each independently It is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ⁵ is at least one selected from the group consisting of a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

Furthermore, in the organoaluminum compound represented by the general formula (II), n is 0, R ² is each independently an unsubstituted alkyl group having 1 to 4 carbon atoms, and n is 1 to 3 R ² is each 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 or R ⁴ bonded to the oxygen atom is A group consisting of a compound having an alkyl group having 1 to 4 carbon atoms and 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; More preferably, it is at least one selected from more.

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

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

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

  The organoaluminum compound preferably has n of 1 to 3, that is, an aluminum chelate structure in addition to the aluminum alkoxide structure. When n is 0, that is, when it exists in the composition for forming a passivation layer in the state of an aluminum alkoxide structure, it is preferable to add a chelating reagent (chelating agent) to the composition for forming a passivation layer. Examples of chelating reagents include those described above.

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

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

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

  The organoaluminum compound represented by the general formula (II) and n is 1 to 3 can be prepared by mixing the aluminum trialkoxide and a chelating reagent. Examples of the chelating reagent include compounds having a specific structure having two carbonyl groups. Specifically, when the aluminum trialkoxide is mixed with a compound having a specific structure having two carbonyl groups, at least a part of the alkoxide group of the aluminum trialkoxide is substituted with a compound having a specific structure, thereby forming an aluminum chelate structure. Form. At this time, if necessary, a solvent may be present, or heat treatment or addition of a catalyst may be performed. By replacing at least a part of the aluminum alkoxide structure with an aluminum chelate structure, the stability of the organoaluminum compound to hydrolysis and polymerization reaction is improved, and the storage stability of the composition for forming a passivation layer containing this is further improved. To do.

  The compound having a specific structure having two carbonyl groups may be at least one selected from the group consisting of a β-diketone compound, a β-ketoester compound, and a malonic acid diester from the viewpoint of reactivity and storage stability. preferable. Specific examples of the β-diketone compound, β-ketoester compound and malonic acid diester include the compounds described above as chelating reagents.

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

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

  The organoaluminum compound may be liquid or solid and is not particularly limited. From the viewpoint of the passivation effect and storage stability, the uniformity of the passivation layer formed can be achieved by using an organoaluminum compound that is stable at room temperature (about 10 ° C. to 40 ° C.) and has good solubility or dispersibility. It can improve further and can acquire the desired 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 content of the aluminum compounds in the composition for forming a passivation layer The 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 a 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, The content is more preferably no less than 99% by mass and no greater than 99% by mass, and still more preferably no less than 1% by mass and no greater than 95% by mass.

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 includes Nb ₂ O ₅ —Al ₂ O ₃ , Binary complex 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 Examples thereof include ternary complex oxides such as ₂ O ₅ .

From the viewpoint of the high passivation effect and the temporal stability of the passivation effect, the composition for forming a passivation layer is selected from the group consisting of Nb ₂ O ₅ and a compound in which M is Nb in the general formula (I). It is preferable to contain at least one niobium compound. The total content of the niobium compound of the passivation layer forming composition is preferably a 0.1 wt% to 99.9 wt% calculated as _Nb 2 _{O 5,} with 1 wt% to 99 wt% More preferably, it is more preferably 5% by mass to 90% by mass. Identification in a passivation layer obtained by heat-treating a composition for forming a passivation layer containing Nb ₂ O ₅ and at least one niobium compound selected from the group consisting of compounds in which M is Nb in the general formula (I) Examples of the composition of the metal oxide 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 , Binary complex oxides such as Nb ₂ O ₅ —HfO ₂ ; 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 such as _{-Al 2 O 3 -V 2 O 5} , Nb 2 O 5 -HfO 2 -Ta 2 O ternary composite oxide such as ₅ can be mentioned.

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

  The inventors consider the reason why a passivation layer having an excellent passivation effect can be formed by heat-treating the composition for forming a passivation layer as follows. It is considered that when the composition for forming a passivation layer containing a specific metal compound is heat-treated, defects such as metal atoms and oxygen atoms are generated and a large fixed charge is generated in the vicinity of the interface with the semiconductor substrate. This large fixed charge generates an electric field in the vicinity of the interface of the semiconductor substrate, so that the concentration of minority carriers can be reduced. As a result, the carrier recombination rate at the interface is suppressed, so that it has an excellent passivation effect. It is believed that a passivation layer can be formed. Furthermore, it is thought that the composition for forming a passivation layer is excellent in storage stability over time because the occurrence of problems such as gelation is suppressed.

(Liquid medium)
The composition for forming a passivation layer preferably contains a liquid medium. When the composition for forming a passivation layer contains a liquid medium, the viscosity can be adjusted more easily, the applicability can be 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 can be appropriately selected as necessary.

Specific examples of the liquid medium include acetone, methyl ethyl ketone, methyl n-propyl ketone, methyl isopropyl ketone, methyl n-butyl ketone, methyl isobutyl ketone, methyl n-pentyl ketone, methyl n-hexyl ketone, diethyl ketone, Ketone solvents such as dipropyl ketone, diisobutyl ketone, trimethylnonanone, cyclohexanone, cyclopentanone, methylcyclohexanone, 2,4-pentanedione, acetonylacetone; diethyl ether, methyl ethyl ether, methyl-n-propyl ether, diisopropyl Ether, tetrahydrofuran, methyltetrahydrofuran, dioxane, dimethyldioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol Rudi-n-propyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol methyl n-propyl ether, diethylene glycol methyl n-butyl ether, diethylene glycol di-n-propyl ether, diethylene glycol di- n-butyl ether, diethylene glycol methyl-n-hexyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol methyl ethyl ether, triethylene glycol methyl-n-butyl ether, triethylene glycol di-n-butyl ether, triethylene Glycolme Ru-n-hexyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol methyl ethyl ether, tetraethylene glycol methyl n-butyl ether, tetraethylene glycol di-n-butyl ether, tetraethylene glycol methyl n- Hexyl ether, tetraethylene glycol di-n-butyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol di-n-propyl ether, propylene glycol dibutyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, dipropylene glycol methyl Ethyl ether, dipropylene glycol Cyl-n-butyl ether, dipropylene glycol di-n-propyl ether, dipropylene glycol di-n-butyl ether, dipropylene glycol methyl-n-hexyl ether, tripropylene glycol dimethyl ether, tripropylene glycol diethyl ether, tripropylene glycol methyl Ethyl ether, tripropylene glycol methyl-n-butyl ether, tripropylene glycol di-n-butyl ether, tripropylene glycol methyl-n-hexyl ether, tetrapropylene glycol dimethyl ether, tetrapropylene glycol diethyl ether, tetrapropylene glycol methyl ethyl ether, tetra Propylene glycol methyl-n-butyl ether, tetrapropylene glycol Ruji -n- butyl ether, ethers such as tetrapropylene glycol methyl -n- hexyl ether solvents; methyl acetate, ethyl acetate, n- propyl, isopropyl acetate, n- butyl acetate, isobutyl acetate 2-butyl acetate n- Pentyl, 2-pentyl acetate, 3-methoxybutyl acetate, methyl pentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, 2- (2-butoxyethoxy) ethyl acetate, benzyl acetate, cyclohexyl acetate, methylcyclohexyl acetate, nonyl acetate , Methyl acetoacetate, ethyl acetoacetate, diethylene glycol methyl ether acetate, diethylene glycol monoethyl ether acetate, dipropylene glycol methyl ether acetate, dipropylene glycol ethyl ether acetate, glycoacetate , Methoxytriethylene glycol acetate, isoamyl acetate, ethyl propionate, n-butyl propionate, isoamyl propionate, diethyl oxalate, di-n-butyl oxalate, methyl lactate, ethyl lactate, n-butyl lactate, n-lactate Amyl, ethylene glycol methyl ether propionate, ethylene glycol ethyl ether propionate, ethylene glycol methyl ether acetate, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, propylene glycol propyl ether acetate, γ- Ester solvents such as butyrolactone and γ-valerolactone; acetonitrile, N-methylpyrrolidinone, N-ethylpyrrolidinone, N Aprotic polar solvents such as propylpyrrolidinone, N-butylpyrrolidinone, N-hexylpyrrolidinone, N-cyclohexylpyrrolidinone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide; 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, isobutanol, 2- Butanol, t-butanol, n-pentanol, isopentanol, 2-methylbutanol, 2-pentanol, t-pentanol, 3-methoxybutanol, n-hexanol, 2 -Methylpentanol, 2-hexanol, 2-ethylbutanol, 2-heptanol, n-octanol, 2-ethylhexanol, 2-octanol, n-nonyl alcohol, n-decanol, 2-undecyl alcohol, trimethylnonyl alcohol, 2-tetradecyl alcohol, 2-heptadecyl alcohol, cyclohexanol, methylcyclohexanol, isobornylcyclohexanol, benzyl alcohol, ethylene glycol, 1,2-propylene glycol, 1,3-butylene glycol, diethylene glycol, dipropylene glycol , Alcohol solvents such as triethylene glycol and tripropylene glycol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol Monophenyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol mono-n-hexyl ether, ethoxytriglycol, tetraethylene glycol mono-n-butyl ether, propylene glycol monomethyl ether, dipropylene glycol Glycol monoether solvents such as monomethyl ether, dipropylene glycol monoethyl ether, and tripropylene glycol monomethyl ether; terpene solvents such as terpinene, terpineol, myrcene, alloocimene, limonene, dipentene, pinene, carvone, osymene, and ferrandrene; Can be mentioned. These liquid media can be used alone or in combination of two or more.

  The liquid medium is a group consisting of a terpene solvent, an ester solvent, and an alcohol solvent from the viewpoint of impartability to a semiconductor substrate and pattern formability (inhibition of pattern enlargement during application of a passivation layer forming composition and drying). It is preferable to include at least one selected from the above, and it is more preferable to include at least one terpene solvent.

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

(resin)
It is preferable that the composition for forming a passivation layer further contains at least one resin. By including the resin, the shape stability of the composition layer formed by applying the passivation layer-forming composition on the semiconductor substrate is further improved, and the passivation layer is desired in the region where the composition layer is formed. It becomes easier to selectively form with this shape.

  The type of the resin is not particularly limited, and is preferably a resin whose viscosity can be adjusted within a range where a good pattern can be formed when the composition for forming a passivation layer is applied onto a semiconductor substrate. Specific examples of the resin include cellulose derivatives such as polyvinyl alcohol, polyacrylamide, polyvinylamide, polyvinylpyrrolidone, polyethylene oxide, polysulfone, polyacrylamide alkylsulfone, cellulose ether such as cellulose, carboxymethylcellulose, hydroxyethylcellulose, ethylcellulose, gelatin, and gelatin. Derivatives, starch and starch derivatives, sodium alginate and sodium alginate derivatives, xanthan and xanthan derivatives, guar gum and guar gum derivatives, scleroglucan and scleroglucan derivatives, tragacanth and tragacanth derivatives, dextrin and dextrin derivatives, (meth) acrylic acid resins, (Meth) acrylic ester resins (eg, alkyl (meta Acrylate resins, dimethylaminoethyl (meth) acrylate resin, etc.), butadiene resins, styrenic resins, siloxane resins, and the like of these copolymers. These resins can be used alone or in combination of two or more.

Among these resins, from the viewpoint of storage stability and pattern formation, it is preferable to use a neutral resin having no acidic or basic functional group, and the viscosity and thixotrope can be easily used even when the content is small. From the viewpoint of adjusting the properties, it is more preferable to use a cellulose derivative.
The molecular weight of the resin is not particularly limited, and is preferably adjusted appropriately in view of the desired viscosity as the composition for forming a passivation layer. The weight average molecular weight of the resin is preferably 1,000 to 10,000,000, more preferably 3,000 to 5,000,000, from the viewpoints of storage stability and pattern formation. In addition, the weight average molecular weight of resin is calculated | required by converting using the analytical curve of a standard polystyrene from molecular weight distribution measured using GPC (gel permeation chromatography). The calibration curve is approximated by a cubic equation using 5 standard polystyrene sample sets (PStQuick MP-H, PStQuick B [trade name, manufactured by Tosoh Corporation)]. The measurement conditions for GPC are shown below.

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

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

  When the composition for forming a passivation layer contains a resin, the content ratio of the organoaluminum compound and the resin in the composition for forming a passivation layer can be appropriately selected as necessary. Above all, from the viewpoint of pattern formability and storage stability, the ratio of the resin when the total amount of one or more selected from the group consisting of the specific metal compound and the aluminum oxide and precursor thereof contained as necessary is 1. Is preferably 0.001 to 1000, more preferably 0.01 to 100, and still 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 of the acidic compound or the basic compound in the composition for forming a passivation layer is 1% by mass or less, respectively. It is preferable that the content is 0.1% by mass or less.

  Examples of acidic compounds include Bronsted acid and Lewis acid. Specific examples include inorganic acids such as hydrochloric acid and nitric acid, and organic acids such as acetic acid. Examples of basic compounds include Bronsted bases and Lewis bases. Specific examples include inorganic bases such as alkali metal hydroxides and alkaline earth metal hydroxides; organic bases such as trialkylamines and pyridines.

  The composition for forming a passivation layer contains various additives such as a thickener, a wetting agent, a surfactant, an inorganic powder, a resin containing a silicon atom, a thixotropic agent, as other components, as necessary. Also good.

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

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

  Examples of the resin containing silicon atoms include lysine-modified silicones at both ends, polyamide-silicone alternating copolymers, side-chain alkyl-modified silicones, side-chain polyether-modified silicones, terminal alkyl-modified silicones, silicone-modified pullulans, and silicone-modified acrylic resins. It can be illustrated. When the composition for forming a passivation layer contains a resin containing silicon, the thickness and composition uniformity of the composition layer formed from the composition for forming a passivation layer tend to be improved.

  Examples of thixotropic agents include polyether compounds, fatty acid amides, fumed silica, hydrogenated castor oil, urea urethane amide, polyvinyl pyrrolidone, and oil-based gelling agents. When the composition for forming a passivation layer contains a thixotropic agent, the pattern formability when applying the composition for forming a passivation layer tends to be improved. Examples of the polyether compound include polyethylene glycol, polypropylene glycol, poly (ethylene-propylene) glycol copolymer, and the like.

The viscosity of the composition for forming a passivation layer is not particularly limited, and can be appropriately selected depending on a method for applying the composition to a semiconductor substrate. For example, the viscosity of the composition for forming a passivation layer can be 0.01 Pa · s to 10000 Pa · s. Among these, from the viewpoint of pattern formability, the viscosity of the composition for forming a passivation layer is preferably 0.1 Pa · s to 1000 Pa · s. The viscosity is a value measured at 25 ° C. and a shear rate of 1.0 s ⁻¹ using a rotary shear viscometer.

It is preferable that the composition for forming a passivation layer has thixotropy. In particular, if the passivation layer forming composition comprising a resin, from the viewpoint of pattern formability is calculated by dividing the shear viscosity eta ₁ at a shear rate of 1.0 s ^-1 at shear viscosity eta ₂ at a shear rate of 10s ^-1 The thixo ratio (η ₁ / η ₂ ) is preferably 1.05 to 100, more preferably 1.1 to 50. The shear viscosity is measured at a temperature of 25 ° C. using a rotary shear viscometer equipped with a cone plate (diameter 50 mm, cone angle 1 °).

There is no restriction | limiting in particular in the manufacturing method of the composition for formation of a passivation layer. For example, a specific metal compound and a liquid medium or the like contained as necessary can be mixed and produced by a commonly used method. Moreover, you may manufacture by mixing the liquid medium and resin which dissolved resin, and a specific metal compound.
Further, the specific metal compound may be prepared by mixing the compound of formula (I) and a compound capable of forming a chelate with the metal element contained in the compound of formula (I). At that time, a solvent may be appropriately used or heat treatment may be performed. A composition for forming a passivation layer may be produced using the specific metal compound thus prepared.
The components contained in the composition for forming a passivation layer and the content of each component are determined by thermal analysis such as thermo-thermogravimetric simultaneous measurement (TG / DTA), nuclear magnetic resonance (NMR), infrared spectroscopy. It can be confirmed by spectral analysis such as (IR), chromatographic analysis such as high performance liquid chromatography (HPLC), gel permeation chromatography (GPC) and the like.

<Method for producing solar cell element>
The method for manufacturing a solar cell element according to the present invention includes a light receiving surface and a back surface opposite to the light receiving surface, the p type diffusion region of the semiconductor substrate having a p type diffusion region and an n type diffusion region on the back surface. Forming a first metal electrode on at least a portion and forming a second metal electrode on at least a portion of the n-type diffusion region, and a specific metal oxide on a portion or all of the back surface of the semiconductor substrate. Forming a composition layer by applying a composition for forming a passivation layer containing at least one selected from the group consisting of a compound and a compound represented by formula (I);
And 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 the semiconductor substrate. Furthermore, the passivation layer can be formed by a simple and highly productive method that does not require a vapor deposition apparatus or the like, and can be formed in a desired shape without requiring a complicated process such as mask processing. Therefore, according to the said method, the solar cell element excellent in conversion efficiency can be manufactured by a simple method.

  A semiconductor substrate having a p-type diffusion region and an n-type diffusion region on the back surface can be manufactured by a commonly used method. For example, it can be produced according to the method described in Japanese Patent No. 3522940. As a method of forming a metal electrode in at least a part of the p-type diffusion region and at least a part of the n-type diffusion region, for example, for forming an electrode such as silver paste or aluminum paste in a desired region on the back surface of the semiconductor substrate. It can be formed by applying a paste and heat-treating it as necessary. In the present invention, the step of forming the metal electrode in at least part of the p-type diffusion region and at least part of the n-type diffusion region may be performed before the step of forming the passivation layer, and the passivation layer is formed. It may be performed after the process.

The method for forming the composition layer by applying the passivation layer-forming composition containing the specific metal compound to a part or all of the back surface of the semiconductor substrate is not particularly limited. Specifically, a dipping method, a printing method such as screen printing, spin coating, brushing, spraying, doctor blade method, Roruko method, a an inkjet method. Among these, from the viewpoint of pattern formability, a printing method and an inkjet method are preferable, and a screen printing method is more preferable.

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

The passivation layer is formed on the semiconductor substrate by heat-treating the composition layer formed by applying the passivation layer-forming composition on the semiconductor substrate to form a heat-treated material layer derived from the composition layer. be able to.
The heat treatment conditions for the composition layer are not particularly limited as long as the specific metal compound contained in the composition for forming a passivation layer is converted into the specific metal oxide. For example, there is no particular limitation as long as the compound represented by the general formula (I) contained in the composition layer can be converted into a specific metal oxide that is the heat-treated product. Among these, it is preferable that the conditions are such that an amorphous specific metal oxide layer having no crystal structure can be formed. When the passivation layer is made of an amorphous specific metal oxide, the passivation layer can effectively have a negative charge, and a more excellent passivation effect can be obtained. Specifically, the heat treatment temperature is preferably 400 ° C. or higher, more preferably 400 ° C. to 900 ° C., and still more preferably 600 ° C. to 800 ° C. The heat treatment time can be appropriately selected according to the heat treatment temperature and the like. For example, it can be 5 seconds to 10 hours, and is preferably 10 seconds to 5 hours.

Preferably the density of the passivation layer is ^{1.0g / cm 3 ~10.0g / cm 3} , more preferably from ^{2.0g / cm 3 ~8.0g / cm 3} , 3.0g / cm 3 More preferably, it is ˜7.0 g / cm ³ . If the density of the passivation layer is ^{1.0g / cm 3 ~10.0g / cm 3} , sufficient passivation effect can be obtained, its high passivation effect tends to hardly change over time. The reason is that when the density of the passivation layer is 1.0 g / cm ³ or more, the moisture and impurity gas in the outside world do not easily reach the interface between the semiconductor substrate and the passivation layer, and the passivation effect is easily sustained. It is presumed that the interaction with the semiconductor substrate tends to increase when the concentration is 0.0 g / cm ³ or less. As a method for measuring the density of the passivation layer, a method of measuring and calculating the mass and volume of the passivation layer, an X-ray reflectivity method, and making X-rays incident on the sample surface at a very shallow angle, the incident angle versus the mirror surface direction. A method of determining the film thickness and density of the sample by measuring the X-ray intensity profile reflected on the surface, comparing the profile obtained by the measurement with the simulation result, and optimizing 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 still more preferably 30 nm to 5 μm. If the average thickness of the passivation layer is 5 nm or more, a sufficient passivation effect can be easily obtained, and if it is 50 μm or less, the element structure can be designed in consideration of other members constituting the solar cell element. is there.
The average thickness of the passivation layer is an arithmetic average value of five thicknesses measured using an interference film thickness meter.

Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 2 is a sectional view schematically showing an example of a method for manufacturing a solar cell element having a passivation layer according to the present embodiment. However, this process diagram does not limit the present invention.

As shown in FIG. 2A, an n ⁺ -type diffusion layer 12 is formed on the light-receiving surface side of the n-type semiconductor substrate 11, and an antireflection film 13 is formed on the outermost surface on the light-receiving surface side. A p ⁺ type diffusion layer which is a p type diffusion region 14 and an n ⁺ type diffusion layer which is an n type diffusion region 12 are formed on the back surface. 2A is a cross-sectional view when the semiconductor substrate having the back electrode structure shown in FIG. 1 is cut along line AA.
The p-type diffusion region 14 can be formed, for example, by applying a p-type diffusion layer forming composition or an aluminum electrode paste capable of forming a p ⁺ -type diffusion layer by thermal diffusion treatment to a desired region and then performing a heat treatment. . The n-type diffusion region 12 can be formed by, for example, applying a composition for forming an n-type diffusion layer capable of forming an n ⁺ -type diffusion layer to a desired region by a thermal diffusion treatment and then performing a heat treatment. As a composition for n type diffused layer formation, the composition containing a donor element containing material and a glass component can be mentioned, for example. Examples of the antireflection film 13 include a silicon nitride film and a titanium oxide film. A surface protective film (not shown) such as a silicon oxide film may further exist between the antireflection film 13 and the p-type semiconductor substrate 11. Moreover, you may use the said passivation layer as a surface protective film.

  Next, as shown in FIG. 2B, a first metal electrode 15 and a second metal electrode 17 are formed on the p-type diffusion region 14 and the n-type diffusion region 12 on the back surface, respectively. These metal electrodes can be formed by heat treatment after applying a commonly used electrode forming paste such as a silver electrode paste, an aluminum electrode paste, or a copper electrode paste. The first metal electrode 15 and the p-type diffusion region 14 may be formed by applying a material for forming an electrode such as an aluminum electrode paste, followed by heat treatment.

  The surface of the n-type semiconductor substrate 11 is preferably washed with an alkaline aqueous solution before applying the passivation layer forming composition. By washing with an alkaline aqueous solution, organic substances, particles and the like present on the surface of the semiconductor substrate can be removed, and the passivation effect tends to be further improved. As a method for cleaning with an alkaline aqueous solution, generally known RCA cleaning and the like can be exemplified. For example, the organic substance and particles can be removed by immersing the semiconductor substrate in a mixed solution of ammonia water and hydrogen peroxide water and treating the substrate at 60 ° C. to 80 ° C. The treatment time is preferably 10 seconds to 10 minutes, and more preferably 30 seconds to 5 minutes.

Next, as shown in FIG. 2 (c), the passivation layer forming composition is applied to a region other than the region where the first metal electrode 15 and the second metal electrode 17 are formed on the back surface of the n-type semiconductor substrate 11. To form a composition layer. The imparting method is not particularly limited, and can be selected from known methods. Specifically, a dipping method, a printing method such as screen printing, spin coating, brushing, spraying, doctor blade method, Roruko method, a an inkjet method. Among these, from the viewpoint of pattern formability, a printing method and an inkjet method are preferable, and a screen printing method is more preferable. The application amount of the composition for forming a passivation layer can be appropriately selected according to the purpose. For example, the thickness of the passivation layer to be formed can be appropriately adjusted so as to be the above-described preferable thickness.

  You may further have the process of drying the composition layer which consists of a composition for passivation layer formation between the process of providing the composition for passivation layer formation, and the process of forming a passivation layer by heat processing. By having a step of drying the composition layer, a passivation layer having a more uniform passivation effect tends to be formed.

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

  Finally, the passivation layer 16 is formed by heat-treating the composition layer formed on the back surface of the n-type semiconductor substrate 11. The heat treatment conditions for the composition layer are as described above. As described above, the solar cell element of the present invention can be manufactured.

  Since the solar cell element having the structure as shown in FIG. 2 has no electrode on the light receiving surface side, the area of the light receiving region can be increased and the power generation efficiency is excellent. Furthermore, it can be set as the solar cell element which is more excellent in power generation efficiency by forming a passivation layer in the back surface using the composition for formation of a passivation layer.

  In FIG. 2C, the passivation layer is formed only on the back surface of the n-type semiconductor substrate 11, but a passivation layer may be further formed on the side surface (edge) in addition to the back surface (not shown). Thereby, the solar cell element excellent in power generation efficiency can be manufactured. The effect of the passivation layer is particularly great when used in a place where there are many crystal defects such as side surfaces.

  As shown in FIG. 3, the solar cell element of the present invention may have a passivation layer 16 on the light receiving surface side. In the example of the manufacturing method shown in FIG. 2, the passivation layer is formed after the electrode is formed. However, the electrode may be formed after the passivation layer is formed. Further, although an example in which an n-type semiconductor substrate is used as a semiconductor substrate is shown in FIG. 2, a solar cell element having excellent conversion efficiency can be manufactured by a similar method even when a p-type semiconductor substrate is used.

The solar cell element of the present invention may have a via hole type back contact structure. FIG. 4 schematically shows an example of a via hole type back contact structure. As shown in FIG. 4, the solar cell element with the via-hole type back contact structure has a through hole penetrating from the light receiving surface to the back surface of the semiconductor substrate. The through hole is formed, for example, by irradiating a semiconductor substrate with laser light. The diameter of the opening of the through hole can be about 50 μm to 150 μm, for example, and the density of the opening of the through hole on the surface of the semiconductor substrate can be about 100 / cm ² , for example.

  After the formation of the through hole, the damaged layer generated by the laser beam irradiation to the semiconductor substrate is removed by etching, and a p-type diffusion region 14 is formed in a desired region on the back surface. Next, the n-type diffusion region 12 is formed on the light receiving surface. A first metal electrode 15 and a second metal electrode 17 are formed on the formed p-type diffusion region 14 and n-type diffusion region 12, respectively. Further, a passivation layer 16 is formed in a region where the back electrode is not formed. The method for forming the p-type diffusion region, the n-type diffusion region, the electrode, and the passivation layer can be the same as described above. The passivation layer 16 may be formed other than the back surface of the semiconductor substrate, and may also be formed on the side surface and the wall surface of the through hole (not shown).

  FIG. 5 is a plan view schematically showing an example of an electrode pattern on the back surface of the solar cell element having the via-hole back contact structure shown in FIG. A cross-sectional view taken along line BB in FIG. 5 corresponds to FIG. In FIG. 5, the description of the passivation layer 16 is omitted.

<Solar cell module>
The solar cell module of this invention has the solar cell element of this invention, and the wiring material arrange | positioned on the electrode of the said solar cell element. The solar cell module may include a plurality of solar cell elements connected via a wiring material, and may be sealed with a sealing material. The wiring material and the sealing material are not particularly limited, and can be appropriately selected from materials usually used in this technical field. There is no particular restriction on the size of the solar cell module can be, for example, 0.5m ² ~3m ^2.

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

<Example 1>
(Preparation of a composition for forming a passivation layer)
Al ₂ O ₃ thin film coating material (High-Purity Chemical Laboratory, SYM-Al04, 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 Laboratory, Nb-05, Nb ₂ O ₅ : 5% by mass, n-butyl acetate: 56% by mass, stabilizer: 16. The composition 1 for forming a passivation layer 1 was prepared by mixing 1.0 g of 5 mass%, viscosity modifier: 22.5 mass%).

(Formation of passivation layer)
As the semiconductor substrate, a single crystal p-type silicon substrate (SUMCO, 50 mm square, thickness: 625 μm) having a mirror-shaped surface was used. The silicon substrate was pre-treated by immersing and cleaning at 70 ° C. for 5 minutes using an RCA cleaning solution (Kanto Chemical Co., Ltd., Frontier Cleaner-A01).
Thereafter, a spin coater (Mikasa Co., Ltd., MS-100) is used for 30 seconds at 4000 rpm (min ⁻¹ ) over the entire surface of one side of the silicon substrate pretreated with the passivation layer forming composition 1 obtained above. Granted on condition. Then, it dried at 150 ° C. for 3 minutes. Subsequently, after heat-treating in the air at 700 ° C. for 10 minutes, the substrate was allowed to cool at room temperature (25 ° C.) to produce an evaluation substrate having a passivation layer.

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

(Measurement of average thickness)
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 value was 82 nm.

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

(Method for manufacturing solar cell element)
A solar cell element having a via-hole type back contact structure as shown in FIG. 4 was produced using the composition for forming a passivation layer obtained above. Specifically, 0.2 through-holes having a diameter of 100 μm penetrating both sides of an n-type semiconductor substrate 11 (Advantech Co., Ltd., 125 mm square, thickness: 200 μm, n-type silicon substrate after as-slicing) with a laser drill / Cm ^{2 was} formed. The n-type semiconductor substrate 11 was immersed in a 40% by mass aqueous sodium hydroxide solution (Wako Pure Chemical Industries, Ltd.) and treated at 60 ° C. for 10 minutes to remove the damaged layer. Then, it processed for 10 minutes at 60 degreeC with 8 mass% sodium hydroxide aqueous solution, and formed the texture on both surfaces. Next, using a diffusion furnace (Koyo Thermo System Co., Ltd., 206A-M100), the treatment was performed at 870 ° C. for 20 minutes using POCl ₃ to form the n-type diffusion layer 12 on the entire surface. Thereafter, the substrate was floated on a 40% by mass aqueous sodium hydroxide solution (Wako Pure Chemical Industries, Ltd.) and treated at 80 ° C. for 10 minutes to etch only the back surface. Thereafter, the composition for forming a passivation layer is applied to an area other than the electrode formation scheduled area on the entire light receiving surface and on the back surface with an ink jet device (Microjet Corporation, MJP-1500V, head: IJH-80, nozzle size: 50 μm × 70 μm). Used and dried at 150 ° C. to form a composition layer. Then heat treated at 700 ° C., to form a passivation layer 16 containing _Nb 2 _{O 5} and _Al 2 _{O 3.}

  Next, the antireflection film 13 was formed by depositing silicon nitride on the semiconductor passivation layer 16 on the light receiving surface. The n-type diffusion region 12 was also formed inside the through hole and part of the back surface. Next, a silver electrode paste (DuPont Co., Ltd., PV159A) diluted 5 times with terpineol is filled into the through hole by an ink jet method, and the silver electrode paste is also connected to the inside of the through hole on the light receiving surface side. The shape was applied by screen printing.

  On the other hand, in the n-type diffusion region on the back surface derived from the n-type silicon substrate 11, a silver electrode paste (DuPont, PV159A) is formed in the shape of the second metal electrode 17 shown in FIG. 5 so as to cover the opening of the through hole. ). Further, an aluminum electrode paste (PVG Solutions, PVG-AD-02) was applied to the shape of the first metal electrode 15 shown in FIG. An ink jet apparatus (Microjet Co., Ltd., MJP-1500V, head: IJH-80, nozzle size: 50 μm × 70 μm) was used for applying the silver electrode paste and the aluminum electrode paste.

  The n-type silicon substrate 11 provided with the silver electrode paste and the aluminum electrode paste is subjected to a heat treatment using a tunnel furnace (Noritake Co., Ltd.) at a maximum temperature of 800 ° C. and a holding time of 10 seconds. A solar cell element in which one metal electrode 15 and second metal electrode 17 were formed was produced. A first metal electrode 15 was formed in the portion to which the aluminum electrode paste was applied, and the p-type diffusion region 14 was formed by diffusing aluminum into the n-type silicon substrate 11.

Immediately after production of the solar cell element (one hour later), the power generation characteristics were evaluated using a solar cell element solar simulator (Wacom Denso Co., Ltd., XS-155S-10).
Evaluation was made using simulated sunlight (device name: WXS-155S-10, Wacom Electric Co., Ltd.) and a voltage-current (IV) evaluation measuring device (device name: IV CURVE TRACER MP-160, Eihiro Seiki). This was performed in combination with a measuring device of Co., Ltd. Jsc (short circuit current density), Voc (open circuit voltage), FF (fill factor), and Eff1 (conversion efficiency) indicating the power generation performance as solar cells are JIS-C-8913 (2005) and JIS-C-8914, respectively. It was obtained by measuring according to (2005).
The results are shown in Table 2. The evaluation was performed with a mask so that the light receiving area was 125 mm × 125 mm. Moreover, the produced solar cell element was put in a constant temperature and humidity chamber at 50 ° C. and 80% RH, and power generation characteristics after storage for 1 month were evaluated. The results are shown in Table 3. Conversion efficiency after storage solar cell element is 98.8% efficiency Eff2 before storage, conversion efficiency was lowered 1.2%.

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

A substrate for evaluation was prepared by forming a passivation layer on a pretreated silicon substrate in the same manner as in Example 1 except that the above-described composition 2 for forming a passivation layer was used. And evaluated. The effective lifetime was 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 passivation layer forming composition 2 was used instead of the passivation layer forming composition 1, and power generation characteristics were evaluated. The results are shown in Tables 2 and 3. Conversion efficiency after storage solar cell element is 98.2% of the conversion efficiency before storage, conversion efficiency was reduced by 1.8%.

<Example 3>
HfO ₂ thin film coating material (High Purity Chemical Laboratory, Hf-05, HfO ₂ : 5% by mass, isoamyl acetate: 73% by mass, n-octane: 10% by mass, 2-propanol: 5% by mass, stabilization Agent: 7% by mass) was used as the passivation layer forming composition 3.

A substrate for evaluation was prepared by forming a passivation layer on a pretreated silicon substrate in the same manner as in Example 1 except that the composition 3 for forming a passivation layer prepared above was used. Evaluation was performed in the same manner. The effective lifetime was 380 μs. 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 passivation layer forming composition 3 was used instead of the passivation layer forming composition 1, and power generation characteristics were evaluated. The results are shown in Tables 2 and 3. Conversion efficiency after storage solar cell element is 98.3% of the conversion efficiency before storage, conversion efficiency was reduced by 1.7%.

<Example 4>
Y ₂ O ₃ thin film coating material (High-Purity Chemical Laboratory, Y-03, Y ₂ O ₃ : 3% by mass, 2-ethylhexanoic acid: 12.5% by mass, n-butyl acetate: 22.5% by mass %, ethyl acetate: 8 wt%, terpine oil: 45 wt%, a viscosity adjustment agent: 9% by mass) was used as a passivation layer forming composition 4.

A substrate for evaluation was prepared by forming a passivation layer on a pretreated silicon substrate in the same manner as in Example 1 except that the composition 4 for forming a passivation layer prepared above was used. Evaluation was performed in the same manner. The effective lifetime was 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 passivation layer forming composition 4 was used instead of the passivation layer forming composition 1, and power generation characteristics were evaluated. The results are shown in Tables 2 and 3. Conversion efficiency after storage solar cell element is 97.6% of the conversion efficiency before storage, conversion efficiency was reduced by 2.4%.

<Example 5>
Aluminum ethyl acetoacetate diisopropylate (Kawaken Fine Chemical Co., Ltd., ALCH), pentaethoxyniobium (Hokuko Chemical Co., Ltd.), acetylacetone (Wako Pure Chemical Industries, Ltd.), xylene (Wako Pure Chemical Industries, Ltd.), 2- Propanol (Wako Pure Chemical Industries, Ltd.) and terpineol (Nippon Terpene Chemical Co., Ltd.) were mixed so as to have the ratio shown in Table 1 and used as the passivation layer forming composition 5.

A substrate for evaluation was prepared by forming a passivation layer on a pretreated silicon substrate in the same manner as in Example 1 except that the composition 5 for forming a passivation layer prepared above was used. Evaluation was performed in the same manner. The effective lifetime was 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 passivation layer forming composition 5 was used instead of the passivation layer forming composition 1, and power generation characteristics were evaluated. The results are shown in Tables 2 and 3. Conversion efficiency after storage solar cell element is 97.9% of the conversion efficiency before storage, conversion efficiency was reduced by 2.1%.

<Comparative Example 1>
In Example 1, an evaluation substrate was prepared in the same manner as in Example 1 except that the passivation layer forming composition 1 was not applied, and evaluated in the same manner as in Example 1. The effective lifetime was 20 μs.

In Example 1, a solar cell element was produced in the same manner as in Example 1 except that the passivation layer forming composition 1 was not applied, and power generation characteristics were evaluated. The results are shown in Tables 2 and 3. Conversion efficiency after storage solar cell element is 91.9% of the conversion efficiency before storage, conversion efficiency was lowered 8.1%.

<Comparative example 2>
Ethylcellulose (The Dow Chemical Company, STD200) 6.0g and Terpineol (Nippon Terpene Chemical Co., Ltd., Turpineol-LW) 34.0g are mixed, and it melt | dissolves by mixing for 2 hours at 150 degreeC, 15 mass parts An ethylcellulose / terpineol solution was prepared. Next, 2.00 g of Al ₂ O ₃ particles (High Purity Chemical Laboratory, average particle size 1 μm), 3.9 g of terpineol, and 4.1 g of the 15 parts by mass ethylcellulose / terpineol solution prepared above were mixed. Composition C2 was prepared.

A passivation layer was formed on a silicon substrate pretreated in the same manner as in Example 1 except that the composition C2 prepared above was used, and an evaluation substrate was produced. Evaluation was performed in the same manner as in Example 1. . The effective lifetime was 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 with a stylus type step meter (Ambios, XP-2). Specifically, a part of the passivation layer was scraped off with a spatula, and a step between the portion where the passivation layer remained and the scraped portion was measured under the conditions of a speed of 0.1 mm / s and a needle load of 0.5 mg. The measurement was performed three times, and the average value was calculated as the 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 power generation characteristics were evaluated. The results are shown in Tables 2 and 3. Conversion efficiency after storage solar cell element is 93.0% of the conversion efficiency before storage, conversion efficiency was lowered 7.0%.

<Comparative Example 3>
A colorless and transparent composition C3 was prepared by mixing 2.01 g of tetraethoxysilane, 4.02 g of the 15 parts by mass ethylcellulose / terpineol solution prepared above and 3.97 g of terpineol.

A passivation layer was formed on a silicon substrate pretreated in the same manner as in Example 1 except that the composition C3 prepared above was used, and an evaluation substrate was produced. Evaluation was performed in the same manner as in Example 1. . The effective lifetime was 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 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, and power generation characteristics were evaluated. The results are shown in Tables 2 and 3. Conversion efficiency after storage solar cell element is 92.4% of the conversion efficiency before storage, conversion efficiency was lowered 7.6%.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

<Structure explanation of solar cell element>
The structure of the solar cell element of the present embodiment will be described with reference to FIGS. 7-10 is sectional drawing which shows the 1st-4th structural example of the solar cell element which used the passivation film for the back surface of this Embodiment.

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

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

  As shown in FIG. 7 (first configuration example), an n-type diffusion layer 102 doped with a group V element such as phosphorus on the light-receiving surface side (upper side, first surface in the figure) of a p-type silicon substrate 101. Is formed. A pn junction is formed between the silicon substrate 101 and the diffusion layer 102. On the surface of the diffusion layer 102, a light receiving surface antireflection film 103 such as a silicon nitride (SiN) film, and a first electrode 105 (light receiving surface side electrode, first surface electrode, upper surface electrode) using silver (Ag) or the like. , A light receiving surface electrode) is formed. The light receiving surface antireflection film 103 may also have a function as a light receiving surface passivation film. By using the SiN film, both functions of the light receiving surface antireflection film and the light receiving surface passivation film can be provided.

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

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

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

  Further, in FIG. 7 (first configuration example), a contact region (a surface on the back side of the silicon substrate 101 when the BSF layer 104 is not provided) and the second electrode 106 are electrically connected ( A passivation film (passivation layer) 107 containing aluminum oxide and niobium oxide is formed in a portion excluding the opening OA). The passivation film 107 of this embodiment can have a negative fixed charge. With this fixed charge, electrons which are minority carriers among the carriers generated in the silicon substrate 101 by light are bounced back to the surface side. For this reason, a short circuit current increases and it is anticipated that photoelectric conversion efficiency will improve.

  Next, a second configuration example shown in FIG. 8 will be described. In FIG. 7 (first configuration example), the second electrode 106 is formed over the entire surface of the contact region (opening OA) and the passivation film 107. In FIG. The second electrode 106 is formed only in the region (opening OA). The second electrode 106 may be formed only in part on the contact region (opening OA) and the passivation film 107. Even with the solar cell element having the configuration shown in FIG. 8, the same effect as that of FIG. 7 (first configuration example) can be obtained.

  Next, a third configuration example shown in FIG. 9 will be described. In the third configuration example shown in FIG. 9, the BSF layer 104 is formed only on a part of the back surface side including the contact region (opening OA portion) with the second electrode 106, and FIG. 7 (first configuration example). Thus, it is not formed on the entire back surface side. Even with the solar cell element having such a configuration (FIG. 9), the same effect as in FIG. 7 (first configuration example) can be obtained. Further, according to the solar cell element of the third configuration example of FIG. 9, the BSF layer 104, that is, the impurity is doped at a higher concentration than the silicon substrate 101 by doping a group III element such as aluminum or boron. Since there are few areas, it is possible to obtain higher photoelectric conversion efficiency than that in FIG. 7 (first configuration example).

  Next, a fourth configuration example shown in FIG. 10 will be described. In FIG. 9 (third configuration example), the second electrode 106 is formed on the entire surface of the contact region (opening OA) and the passivation film 107, but in FIG. 10 (fourth configuration example), the contact is formed. The second electrode 106 is formed only in the region (opening OA). The second electrode 106 may be formed only in part on the contact region (opening OA) and the passivation film 107. Even with the solar cell element having the configuration shown in FIG. 10, the same effect as in FIG. 9 (third configuration example) can be obtained.

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

  From the above, when the second electrode 106 is not formed on the entire back surface side as shown in FIG. 8 (second configuration example) and FIG. 10 (fourth configuration example), the electrode structure tends to be symmetrical vertically. This is preferable because stress due to the difference in thermal expansion coefficient is not easily generated. However, in that case, it is preferable to provide a separate reflective layer.

<Description of manufacturing method of solar cell element>
Next, an example of a method for manufacturing the solar cell element (FIGS. 7 to 10) of the present embodiment having the above-described configuration will be described. However, the present embodiment is not limited to the solar cell element manufactured by the method described below.

  First, a texture structure is formed on the surface of the silicon substrate 101 shown in FIG. The texture structure may be formed on both sides of the silicon substrate 101 or only on one side (light receiving side). In order to form a texture structure, first, the damaged layer of the silicon substrate 101 is removed by immersing the silicon substrate 101 in a heated potassium hydroxide or sodium hydroxide solution. Then, a texture structure is formed on both surfaces or one surface (light receiving surface side) of the silicon substrate 101 by dipping in a solution containing potassium hydroxide and isopropyl alcohol as main components. In addition, as above-mentioned, since the solar cell element of this Embodiment does not have to have a texture structure, you may abbreviate | omit this process.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

  When an n-type silicon substrate is used, a passivation film 107 containing niobium oxide and aluminum oxide can be used on the light receiving surface side as shown in FIG. FIG. 11 is a cross-sectional view illustrating a configuration example of a solar cell element using the light-receiving surface passivation film of the present embodiment.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[Reference Example 1-6]
Using a single crystal silicon substrate doped with boron as the silicon substrate 101, a solar cell element having the structure shown in FIG. 9 was manufactured. After the surface of the silicon substrate 101 was textured, a coating type phosphorous diffusion material was applied to the light receiving surface side, and a diffusion layer 102 (phosphorus diffusion layer) was formed by heat treatment. Thereafter, the coating type phosphorus diffusing material was removed with dilute hydrofluoric acid.

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

  Next, on the light-receiving surface antireflection film 103 (SiN film) formed on the light-receiving surface side of the silicon substrate 101, a paste mainly composed of silver was screen-printed in the shape of predetermined finger electrodes and bus bar electrodes. On the back side, a paste mainly composed of aluminum was screen-printed on the entire surface. Thereafter, heat treatment (fire-through) is performed at 850 ° C. to form electrodes (first electrode 105 and second electrode 106), and aluminum is diffused into the opening OA on the back surface to form the BSF layer 104. Thus, a solar cell element having the structure shown in FIG. 9 was formed.

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

For comparison, the passivation film 107 is not formed in the above manufacturing process, aluminum paste is printed on the entire back surface, and the p ⁺ layer 114 corresponding to the BSF layer 104 and the electrode 116 corresponding to the second electrode. Was formed on the entire surface to form a solar cell element having the structure shown in FIG. In FIG. 6, reference numeral 111 denotes a silicon substrate, reference numeral 112 denotes a diffusion layer, reference numeral 113 denotes a light-receiving surface antireflection film, and reference numeral 115 denotes a first electrode. About these solar cell elements, characteristic evaluation (a short circuit current, an open circuit voltage, a fill factor, and conversion efficiency) was performed. Characteristic evaluation was measured based on JIS-C-8913 (2005) and JIS-C-8914 (2005). The results are shown in Table 7.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

  The results obtained are summarized in Table 10.

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

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

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

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

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

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

[Reference Example 2-10]
Using a single crystal silicon substrate with boron as a dopant as the silicon substrate 101, a solar cell element having the structure shown in FIG. 9 was produced. After the surface of the silicon substrate 101 was textured, a coating type phosphorous diffusion material was applied only to the light receiving surface side, and a diffusion layer 102 (phosphorus diffusion layer) was formed by heat treatment. Thereafter, the coating type phosphorus diffusing material was removed with dilute hydrofluoric acid.

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

  Next, on the light-receiving surface antireflection film 103 (SiN film) formed on the light-receiving surface side of the silicon substrate 101, a paste mainly composed of silver was screen-printed in the shape of predetermined finger electrodes and bus bar electrodes. On the back side, a paste mainly composed of aluminum was screen-printed on the entire surface. Thereafter, heat treatment (fire-through) is performed at 850 ° C. to form electrodes (first electrode 105 and second electrode 106), and aluminum is diffused into the opening OA on the back surface to form the BSF layer 104. Thus, a solar cell element having the structure shown in FIG. 9 was formed.

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

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

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

  The disclosures of Japanese Patent Application Nos. 2012-160336, 2012-218389, 2013-011934, 2013-040153, and 2013-040154 are incorporated herein by reference in their entirety. All documents, patent applications, and technical standards mentioned in this specification are to the same extent as if each individual document, patent application, and technical standard were specifically and individually stated to be incorporated by reference, Incorporated herein by reference.

Claims (7)

A semiconductor substrate having a light-receiving surface and a back surface opposite to the light-receiving surface, and having a p-type diffusion region containing a p-type impurity and an n-type diffusion region containing an n-type impurity on the back surface;
Provided in part or all of the back surface of the semiconductor substrate, containing 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 A passivation layer to
A first metal electrode provided in at least a part of the p-type diffusion region;
A second metal electrode provided in at least a part of the n-type diffusion region ,
A first metal electrode on at least a part of the p-type diffusion region of the semiconductor substrate having a light-receiving surface and a back surface opposite to the light-receiving surface, and having a p-type diffusion region and an n-type diffusion region on the back surface; Forming a second metal electrode in at least a part of the n-type diffusion region;
Forming a composition layer by applying a passivation layer-forming composition containing a compound represented by the following general formula (I) to a part or all of the back surface of the semiconductor substrate;
Heat-treating the composition layer to form a passivation layer 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 ; The manufacturing method of the solar cell element which has these.
M (OR ¹ ) m (I)
[Wherein M includes 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 p-type diffusion region and the n-type diffusion region are spaced apart from each other, and each has a plurality of rectangular portions having short sides and long sides,
The plurality of rectangular portions of the p-type diffusion region are arranged such that the long sides of the plurality of rectangular portions are along the long sides of the plurality of rectangular portions of the n-type diffusion region,
The method for manufacturing a solar cell element according to claim 1, wherein the plurality of rectangular portions included in the p-type diffusion region and the plurality of rectangular portions included in the n-type diffusion region are alternately arranged. The method for manufacturing a solar cell element according to claim 1, wherein the solar cell element has a back contact structure. The passivation layer further contains Al ₂ O _3, a method for manufacturing a solar cell device according to any one of claims 1 to 3. The passivation layer forming composition further comprises a compound represented by the following Symbol formula (II), a method for manufacturing a solar cell device according to any one of claims 1 to 4.

Wherein, R ² each independently represent an alkyl group having 1 to 8 carbon atoms. n represents an integer of 0 to 3. X ² and X ³ each independently represent an oxygen atom or a methylene group. R ³ , R ⁴ and R ⁵ each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. ] The manufacturing method of the solar cell element as described in any one of Claims 1-5 whose temperature of the said heat processing is 400 degreeC or more. The step of forming the composition layer includes applying the composition for forming a passivation layer by a screen printing method or an ink jet method, and the solar cell element according to any one of claims 1 to 6 . Production method.