TWI569461B - Photovoltaic cell element, production method thereof and photovoltaic cell module - Google Patents

Description

Solar battery component, manufacturing method thereof and solar battery module

The present invention relates to a solar cell element, a method of manufacturing the same, and a solar cell module.

The manufacturing steps of the conventional tantalum solar cell element will be described.

First, in order to promote the light-blocking effect and achieve high efficiency, a p-type germanium substrate having a textured structure formed on the light-receiving surface side is prepared, followed by a mixed gas atmosphere of phosphorus oxychloride (POCl ₃ ), nitrogen, and oxygen. The treatment was carried out at 800 ° C to 900 ° C for several tens of minutes to uniformly form an n-type diffusion layer. In this conventional method, since phosphorus is diffused by using a mixed gas, an n-type diffusion layer is formed not only on the surface as the light-receiving surface but also on the side surface and the back surface. Therefore, side etching for removing the n-type diffusion layer formed on the side surface is performed. In addition, the n-type diffusion layer formed on the back surface must be converted into a p ⁺ -type diffusion layer. Therefore, an aluminum paste containing aluminum powder, glass frit, a dispersion medium, an organic binder, or the like is applied to the entire back surface, and heat-treated (calcined) to form an aluminum electrode, thereby adjusting the n-type diffusion layer. It is a p ⁺ type diffusion layer, and an ohmic contact is obtained.

However, the aluminum electrode formed of the aluminum paste has a low electrical conductivity. So in order to descend Low sheet resistance, the aluminum electrode usually formed on the entire back surface must have a thickness of about 10 μm to 20 μm after heat treatment. Further, since the thermal expansion coefficients of bismuth and aluminum differ greatly, large internal stresses are generated in the ruthenium substrate during heat treatment and cooling, resulting in damage of grain boundaries, growth of crystal defects, and warpage.

In order to solve this problem, there is a method of reducing the amount of the aluminum paste applied and making the thickness of the back electrode layer thin. However, when the amount of the aluminum paste applied is reduced, the amount of aluminum diffused from the surface of the p-type germanium semiconductor substrate to the inside becomes insufficient. As a result, there is a problem that the desired back surface field (BSF) effect (the effect of increasing the collection efficiency of the carrier by the presence of the p ⁺ -type diffusion layer) cannot be achieved, so that the characteristics of the solar cell are lowered.

In the above, a point contact method is proposed in which an aluminum paste is applied to a part of the surface of the substrate, and a p ⁺ -type diffusion layer and an aluminum electrode are partially formed (for example, refer to Japanese Patent No. 3107287). .

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

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

Such a passivation layer is usually formed by an atomic layer deposition (ALD) method or a chemical vapor deposition (CVD) method (for example, refer to the Journal of Applied Physics, 104 (2008), 113703-1~113703-7). Further, as a simple method for forming an aluminum oxide layer on a semiconductor substrate, a method using a sol-gel method has been proposed (for example, refer to "Thin Solid Films", 517 (2009), 6327 to 6330, "Chinese Physics". Chinese Physics Letters, 26 (2009), 088102-1~088102-4).

The method described in Journal of Applied Physics, 104 (2008), and 113703-1 to 113703-7 includes complicated manufacturing steps such as vapor deposition, and thus it may be difficult to improve productivity. In addition, it is used in the methods described in "Thin Solid Films", 517 (2009), 6327~6330, and "Chinese Physics Letters", 26 (2009), 088102-1~088102-4. The composition for forming a passivation layer causes a problem such as gelation over time, and it is difficult to say that the storage stability is sufficient. Further, studies on the use of an oxide containing a metal element other than aluminum to form a passivation layer having an excellent passivation effect have not been sufficiently hitherto.

The present invention has been made in view of the above conventional problems, and an object thereof is to provide a A solar cell element having excellent conversion efficiency and suppressed deterioration of solar cell characteristics over time and a simple manufacturing method thereof, and a reduction in solar cell characteristics with excellent conversion efficiency and with time-lapse are suppressed Solar battery module.

The specific means for solving the above problems are as follows.

<1> A solar cell element comprising: a semiconductor substrate having a light-receiving surface and a back surface opposite to the light-receiving surface; 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; a passivation layer provided on a part or all of the back surface of the semiconductor substrate and containing a group 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 One or more of the first metal electrodes are provided on at least a portion of the p-type diffusion region; and the second metal electrode is provided on at least a portion of the n-type diffusion region.

(2) The solar cell element according to the above aspect, wherein the p-type diffusion region and the n-type diffusion region are disposed apart from each other, and each of the plurality of rectangular portions having a short side and a long side includes the plurality of rectangular portions, and the p-type diffusion The plurality of rectangular portions included in the region are disposed such that the direction of the long sides of the plurality of rectangular portions is along the direction of the long sides of the plurality of rectangular portions of the n-type diffusion regions, and the p-type diffusion regions are The plurality of rectangular portions are arranged alternately with the plurality of rectangular portions of the n-type diffusion region.

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

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

The solar cell element according to any one of the above aspects, wherein the passivation layer is a heat-treated product of a composition for forming a passivation layer.

The solar cell element according to the above aspect, wherein the passivation layer forming composition contains Nb ₂ O ₅ , Ta ₂ O ₅ , V ₂ O ₅ , Y ₂ O ₃ , HfO ₂ and the following One or more of the groups consisting of the compounds represented by the formula (I), M(OR ¹ ) _m (I)

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

The solar cell element according to the above aspect, wherein the composition for forming a passivation layer further contains one selected from the group consisting of Al ₂ O ₃ and a compound represented by the following formula (II). The above aluminum compound, [Chemical 1]

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

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

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

The solar cell element according to any one of the above aspects, wherein the composition for forming a passivation layer contains one or more selected from the group consisting of Al ₂ O ₃ and the above-mentioned aluminum compound. The content of the aluminum compound in the composition for forming a passivation layer is 0.1% by mass to 80% by mass.

The solar cell element according to any one of the above aspects, wherein the composition for forming a passivation layer contains a compound selected from Nb ₂ O ₅ and M in the above formula (I) as Nb. The total content of the above-mentioned cerium compound in the composition for forming a passivation layer is 0.1% by mass to 99.9% by mass in terms of Nb ₂ O ₅ .

The solar cell element according to any one of the above aspects, wherein the composition for forming a passivation layer contains a liquid medium.

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

The solar cell element according to any one of <1> to <13> wherein the passivation layer has a density of 1.0 g/cm ³ to 10.0 g/cm ³ .

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

The method for producing a solar cell element according to any one of the aspects of the present invention, comprising the step of providing a light receiving surface and a side opposite to the light receiving surface At least a part of the p-type diffusion region of the semiconductor substrate having the p-type diffusion region and the n-type diffusion region on the back surface, forming a first metal electrode, and forming a second metal in at least a portion of the n-type diffusion region a step of forming a composition layer by providing a composition for forming a passivation layer in a part or all of a region of the back surface of the semiconductor substrate, wherein the composition for forming a passivation layer contains a material selected from the group consisting of Nb ₂ O ₅ and Ta ₂ O ₅ And one or more of a group consisting of V ₂ O ₅ , Y ₂ O ₃ , HfO ₂ and a compound represented by the following formula (I); and heat-treating the composition layer to form a content selected from the group consisting of Nb a step of one or more passivation layers in a group consisting of ₂ O ₅ , Ta ₂ O ₅ , V ₂ O ₅ , Y ₂ O ₃ and HfO ₂ ; M(OR ¹ ) _m (I)

Wherein M contains at least one metal element selected from the group consisting of Nb, Ta, V, Y, and Hf; and R ¹ independently represents an alkyl group having 1 to 8 carbon atoms or an aromatic group having 6 to 14 carbon atoms; Base; m represents an integer from 1 to 5.

The method for producing a solar cell element according to the above aspect, wherein the composition for forming a passivation layer further contains a group selected from the group consisting of Al ₂ O ₃ and a compound represented by the following formula (II). One or more of them,

In the formula, R ² each independently represents an alkyl group having 1 to 8 carbon atoms; n represents an integer of 0 to 3; and X ² and X ³ each independently represent an oxygen atom or a methylene group; and R ³ , R ⁴ and R ⁵ Each independently represents 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>, wherein the temperature of the heat treatment is 400 ° C or higher.

The method for producing a solar cell element according to any one of <16>, wherein the forming the composition layer comprises: applying a passivation layer by a screen printing method or an inkjet method. Use the composition.

<20> A solar cell module according to any one of <1> to <15>, wherein the solar cell element is disposed on the electrode of the solar cell element.

According to the present invention, it is possible to provide a solar cell element having excellent conversion efficiency and suppressed deterioration of solar cell characteristics over time, a simple manufacturing method thereof, and a solar cell characteristic having excellent conversion efficiency and temporal properties. Reduce the suppressed solar cell module.

11‧‧‧n type semiconductor substrate

12‧‧‧n type diffusion zone

12a, 14a‧‧‧ short side

12b, 14b‧‧‧ long side

12c, 14c‧‧‧ rectangular part

13‧‧‧Anti-reflective film

14‧‧‧p-type diffusion zone

15‧‧‧First metal electrode

16‧‧‧ Passivation layer

17‧‧‧Second metal electrode

101, 111‧‧‧矽 substrate

102, 112‧‧‧ diffusion layer

103, 113‧‧‧Lighted anti-reflection film

104‧‧‧BSF layer

105, 115‧‧‧ first electrode

106‧‧‧2nd electrode

107‧‧‧passivation film

114‧‧‧p ⁺ layer

116‧‧‧electrode

OA‧‧‧ openings

Fig. 1 is a plan view schematically showing an example of a structure of a back surface electrode of a solar cell element having a back contact structure according to the present embodiment.

FIG. 2 is a cross-sectional view schematically showing an example of a method of manufacturing a solar cell element having a back contact structure according to the embodiment.

Fig. 3 is a cross-sectional view schematically showing another example of the solar cell element having the back contact structure of the embodiment.

4 is a cross-sectional view schematically showing an example of a solar cell element having a via-hole type back contact structure according to the embodiment.

FIG. 5 is a plan view schematically showing an example of a back electrode structure of a solar cell element having a via hole type back contact structure according to the present embodiment.

Fig. 6 is a cross-sectional view showing the structure of a double-sided electrode type solar cell element.

Fig. 7 is a cross-sectional view showing a first configuration example of a solar battery element according to the embodiment.

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

FIG. 9 is a cross-sectional view showing a third configuration example of the solar battery element according to the embodiment.

FIG. 10 is a cross-sectional view showing a fourth configuration example of the solar battery element according to the embodiment.

Fig. 11 is a cross-sectional view showing another configuration example of a solar battery element according to the embodiment.

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

<Solar battery component>

The solar cell element of the present invention 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, and a passivation layer provided on the back surface of the semiconductor substrate One or more of the group consisting of Nb ₂ O ₅ , Ta ₂ O ₅ , V ₂ O ₅ , Y ₂ O _{3 ,} and HfO ₂ (hereinafter also referred to as "specific a metal oxide "a metal element contained in each metal oxide is also referred to as a "specific metal element"); a first metal electrode is provided on at least a part of the p-type diffusion region; and a second metal electrode is provided on At least a portion of the n-type diffusion region.

The solar cell element having an electrode and a passivation layer containing a specific metal oxide on the back surface of the semiconductor substrate is excellent in conversion efficiency, and the deterioration of the solar cell characteristics over time is suppressed. The reason for this is considered to be that, by including a specific metal oxide in the passivation layer, an excellent passivation effect is exhibited, and the life of the carrier in the semiconductor substrate is increased, so that high efficiency can be achieved. Further, it is considered that by suppressing the passivation effect of the passivation layer by containing a specific metal oxide, it is possible to suppress a decrease in solar cell characteristics (for example, conversion efficiency) over time. Here, the deterioration of the characteristics of the solar cell over time can be evaluated by the characteristics of the solar cell after standing for a predetermined period of time in the constant temperature and humidity chamber.

Regarding having an electrode on a back surface of a semiconductor substrate and containing a specific metal The reason why the conversion efficiency of the solar cell element of the oxide passivation layer is excellent and the deterioration of the solar cell characteristics over time is suppressed is considered as follows. That is, the specific metal oxide is a compound having a fixed charge. It is considered that band friction is generated by the presence of a compound having a fixed charge on the surface of the semiconductor substrate, and recombination of carriers is suppressed. Further, even a compound having a small fixed charge or a non-fixed charge may exhibit a passivation effect such as a function of repairing a defect on the surface of the semiconductor substrate.

The fixed charge of the compound present on the surface of the semiconductor substrate can be evaluated by Capacitance Voltage Measurement (CV). When the surface energy density of the passivation layer formed by heat-treating the composition for forming a passivation layer to be described later is evaluated by the CV method, it may become more inferior to the case of the passivation layer formed by the ALD method or the CVD method. Big value. However, the passivation layer of the solar cell element of the present invention has a large electric field effect, and the concentration of a minority carrier decreases, and the surface lifetime τ _s becomes large. Therefore, the surface energy density is relatively unproblematic.

In the present specification, the passivation effect of the semiconductor substrate can be evaluated by using a device such as WT-2000PVN of the company Semilab Co., Ltd., by forming a passivation layer by a reflective microwave conduction attenuation method. The effective lifetime of a minority carrier in the semiconductor substrate is measured.

Here, the effective lifetime τ is expressed by the following formula (A) by the body life τ _b inside the semiconductor substrate and the surface life τ _{s of the} surface of the semiconductor substrate. When the surface energy density of the surface of the semiconductor substrate is small, τ _s becomes long, and as a result, the effective lifetime τ becomes long. Further, even if defects such as dangling bonds in the semiconductor substrate are reduced, the body life τ _{b is} also long, and the effective life τ is long. That is, the internal characteristics of the semiconductor substrate such as the interface characteristics between the passivation layer and the semiconductor substrate and the dangling bonds can be evaluated by measuring the effective lifetime τ.

1/τ=1/τ _b +1/τ _s (A)

In addition, the longer the effective life, the slower the recombination speed of a few carriers. Further, by using a semiconductor substrate having a long effective life to constitute a solar cell element, conversion efficiency is improved.

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

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

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 may be appropriately selected depending on the purpose and the like. The p-type diffusion region and the n-type diffusion region are preferably arranged to be spaced 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 they are the number and shape of the effect of the present invention. For example, the p-type diffusion region and the n-type diffusion region preferably each have a plurality of rectangular portions having long sides and short sides. Furthermore, the short side and the long side of the rectangular portion may be all straight lines, respectively, and may also include portions that are not straight lines.

When the p-type diffusion region and the n-type diffusion region respectively include a plurality of rectangular portions having long sides and short sides, the arrangement of the rectangular portion of the p-type diffusion region and the rectangular portion of the n-type diffusion region is not particularly limited. Choose according to the purpose and the like. For example, it is preferable that the plurality of rectangular portions included in the p-type diffusion region are disposed such that a longitudinal direction of the plurality of rectangular portions is along a longitudinal direction of a plurality of rectangular portions of the n-type diffusion region. More preferably, the rectangular portion of the plurality of p-type diffusion regions is alternately arranged with the rectangular portions of the plurality of n-type diffusion regions.

When the p-type diffusion region and the n-type diffusion region each include a plurality of rectangular portions having long sides and short sides, a plurality of rectangular portions of the p-type diffusion region may be connected. For example, it may be connected by a rectangular p-type diffusion region which is disposed so that one end of the plurality of rectangular portions of the p-type diffusion region is in contact with each other in the longitudinal direction. Similarly, a plurality of rectangular portions of the n-type diffusion region may be joined. For example, it may be connected by a rectangular n-type diffusion region which is disposed so that one end of the plurality of rectangular portions of the n-type diffusion region is in contact with each other in the longitudinal direction.

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. Set. The p-type diffusion region 14 includes a plurality of rectangular portions having a short side 14a and a long side 14b, and the plurality of rectangular portions are connected by a rectangular p-type diffusion region 14c disposed at one end in the direction of each long side 14b.

The n-type diffusion region 12 also includes a plurality of rectangular portions having a short side 12a and a long side 12b, and the plurality of rectangular portions are connected by a rectangular n-type diffusion region 12c disposed at one end in the direction of each long side 12b.

In FIG. 1, the rectangular portion 14c that connects the plurality of rectangular portions of the p-type diffusion region 14 and the rectangular portion 12c that connects the plurality of rectangular portions of the n-type diffusion region 12 are disposed on the opposite side in the longitudinal direction. Thereby, 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 can be respectively connected, and the plurality of rectangular portions of the p-type diffusion region 14 and the plurality of rectangles of the n-type diffusion region 12 Partially alternately configured. Such a back electrode structure is also referred to as an "interdigitated type". Moreover, the solar cell element which has the structure shown in FIG. 1 is a back surface contact type solar cell element.

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, it is preferably contained in the p-type diffusion region from the viewpoint of conversion efficiency and long life of the carrier. The concentration of the p-type impurity is 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 preferably 10 ¹⁸ atoms/cm ³ or more, and the concentration of the p-type impurity originally contained in the p-type semiconductor substrate is 10 ⁵ atoms/cm ³ or more and 10 ¹⁷ atoms/cm ³ or less, more preferably, the concentration of the p-type impurity contained in the p-type diffusion region is 10 ¹⁹ atoms/cm ³ or more and 10 ²² atoms/cm ³ or less, and the p-type semiconductor substrate originally contains p-type The concentration of the impurities 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, it is preferably contained in the n-type diffusion region from the viewpoint of conversion efficiency and long life of the carrier. The concentration of the n-type impurity is 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 preferably 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 atoms/cm ³ or less, more preferably, the concentration of the n-type impurity contained in the n-type diffusion region is 10 ¹⁹ atoms/cm ³ or more and 10 ²² atoms/cm ³ or less, and the n-type originally contained in the n-type semiconductor substrate The concentration of the impurities 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 portion 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 portion 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 thickness of the first metal electrode and the second metal electrode is not particularly limited, and is preferably from 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, in the total area of the p-type diffusion region, the size of the region in which the first metal electrode is formed is preferably 50% or more, more preferably 80% or more.

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

From the viewpoint of forming an electrode and diffusing aluminum atoms into the semiconductor substrate to form a p ⁺ -type diffusion layer, the first metal electrode preferably contains aluminum, and its thickness is preferably from 0.1 μm to 50 μm.

The first metal electrode and the second metal electrode can be produced by a method generally used. For example, it is produced by applying a paste for forming an electrode such as a silver paste, an aluminum paste or a copper paste to a desired region of a semiconductor substrate, and heat-treating as necessary.

The solar cell element may further have an electrode that collects a current on the light receiving surface of the semiconductor substrate as needed. 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 thereof 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 via a via electrode penetrating through the semiconductor substrate. The electrode provided on the light receiving surface can be manufactured by a method generally used. For example, it can be manufactured by applying a paste for forming an electrode such as a silver paste, an aluminum paste or a copper paste to a desired region of a semiconductor substrate, and heat-treating as necessary.

The solar cell element of the present invention has a passivation layer containing a specific metal oxide on a part or all of the back surface of the semiconductor substrate.

When the passivation layer is provided on a partial region of the back surface of the semiconductor substrate, the passivation layer is preferably provided in 50% or more of the area of the region of the back surface of the semiconductor substrate, more preferably 80% or more.

Further, for example, the passivation layer may be provided on a 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 a part of the light receiving surface. Or all.

The shape and size of the region in which the passivation layer is formed in the surface of the semiconductor substrate are not particularly limited, and may be appropriately selected depending on the purpose and the like. In the case where the passivation layer is formed on a part of the back surface of the semiconductor substrate, for example, it is preferable that at least a part or all of the region other than the region in which the first metal electrode and the second metal electrode are formed is formed with a passivation layer, and It is preferable that a passivation layer is formed in at least all regions other than the region in which the first metal electrode and the second metal electrode are formed.

From the viewpoint of more sufficiently obtaining a passivation effect, it is preferable that there is no region in which any of the following regions, that is, the electrode or the passivation layer, does not exist between the electrode and the passivation layer. In this case, there may be a region where the electrode overlaps the passivation film.

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

The content of the specific metal oxide contained in the passivation layer can be measured as follows. That is, the ratio of the inorganic substance is calculated by a thermogravimetric analysis method using atomic absorption spectrometry, inductively coupled plasma luminescence spectrometry, thermogravimetric analysis, X-ray photoelectron spectroscopy, or the like. Then, the ratio of the compound containing a specific metal element in the inorganic substance is calculated by atomic absorption spectrometry, inductively coupled plasma luminescence spectrometry, or the like, and the specific metal is calculated by X-ray photoelectric spectroscopy, X-ray absorption spectroscopy, or the like. The ratio of the specific metal oxide in the compound of the element, whereby the content ratio of the specific metal oxide can be obtained.

The passivation layer may also contain metal oxides other than specific metal oxides. Things. Such a metal oxide is preferably a compound having a fixed charge similarly to a specific metal oxide, and examples thereof include alumina, cerium oxide, titanium oxide, gallium oxide, zirconium oxide, boron oxide, indium oxide, phosphorus oxide, and zinc oxide. , cerium oxide, cerium oxide, cerium oxide, cerium oxide, cerium oxide, cerium oxide, cerium oxide, cerium oxide, cerium oxide, cerium oxide, cerium oxide, cerium oxide, cerium oxide, cerium oxide, and the like. From the viewpoint of obtaining a high passivation effect and a stable passivation effect, the metal oxide other than the specific metal oxide contained in the passivation layer is preferably alumina, yttria, titania, zirconia and yttria, more preferably It is alumina.

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

<Composition for forming a passivation layer>

The passivation layer of the solar cell element of the present invention is preferably a heat-treated product of a composition for forming a passivation layer. The passivation layer-forming composition is not particularly limited as long as it can form a passivation layer containing a specific metal oxide by heat treatment, and may contain a specific metal oxide itself or a metal alkoxide containing a specific metal element. A precursor to a particular metal oxide. Hereinafter, a specific metal oxide and its precursor are also referred to as specific metal compounds.

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

M(OR ¹ ) _m (I)

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

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

In the formula (I), R ¹ each independently represents an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 14 carbon atoms, preferably an alkyl group having 1 to 4 carbon atoms or a carbon number of 6 to 9 carbon atoms. Aryl. The alkyl group represented by R ¹ may be linear or branched. Specific examples of the alkyl group represented by R ¹ include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a 2-butyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, and a octyl group. Base, 2-ethylhexyl, 3-ethylhexyl, phenyl, and the like. Specific examples of the aryl group represented by R ¹ include a phenyl group. The alkyl group and the aryl group represented by R ¹ may have a substituent, and examples of the substituent of the alkyl group include a halogen atom, an amine group, a hydroxyl group, a carboxyl group, a decyl group, a nitro group and the like. The substituent of the aryl group may, for example, be a halogen atom, a methyl group, an ethyl group, an isopropyl group, an amine group, a hydroxyl group, a carboxyl group, a decyl group or a nitro group.

Among them, from the viewpoint of storage stability and passivation effect, R ^{1 is} preferably an unsubstituted alkyl group having 1 to 8 carbon atoms, more preferably an unsubstituted alkyl group having 1 to 4 carbon atoms.

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

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

The compound of formula (I) may be either solid or liquid. The compound of the formula (I) is preferably a viewpoint of the storage stability of the composition for forming a passivation layer and the mixing property of the organoaluminum compound in the case of using the organoaluminum compound represented by the following formula (II). liquid.

The compound of the formula (I) may, for example, be hydrazine hydride, hydrazine ethoxide, hydrazine isopropoxide, hydrazine n-propoxide, hydrazine n-butoxide, hydrazine tert-butoxide, hydrazine isobutoxide, hydrazine hydrazine, hydrazine ethoxide or hydrazine isopropoxide. , n-propanol oxime, n-butanol oxime, t-butanol oxime, isobutanol oxime, methanol oxime, ethanol oxime, isopropyl hydrazine, n-propanol oxime, n-butanol oxime, t-butanol oxime, iso- Butanol oxime, methanol oxidized vanadium, ethanol oxidized vanadium, isopropanol vanadium oxide, n-propanol vanadium oxide, n-butanol vanadium oxide, third butanol vanadium oxide, isobutanol vanadium oxide, methanol oxime, ethanol hydrazine, different A propanol propionate, a n-propanol oxime, a n-butanol oxime, a third butanol oxime, an isobutanol oxime or the like. Among them, ethanol oxime, n-propanol oxime, n-butanol oxime, ethanol ruthenium, n-propanol is preferred. Antimony, n-butanol oxime, bismuth isopropoxide and n-butanol oxime. From the viewpoint of obtaining a negative fixed charge density, ethanol oxime, ruthenium n-propoxide, ruthenium n-butoxide, ruthenium ethoxide, N-propanol oxime, n-butanol oxime, ethanol vanadium oxide, n-propanol vanadium oxide, n-butanol vanadium oxide, ethanol ruthenium, n-propanol oxime and n-butanol ruthenium.

As the compound of the formula (I), a preparation can be used, and a commercially available product can also be used. Commercially available products include: pentoxide oxime, pentaethoxy ruthenium, pentaisopropoxy ruthenium, penta-n-propoxy ruthenium, penta-isobutoxy ruthenium, and ruthenium of High Purity Chemical Research Institute Co., Ltd. Butoxy oxime, penta-2-butoxy fluorene, pentamethoxy fluorene, pentaethoxy hydrazine, pentaisopropoxy fluorene, penta-n-propoxy fluorene, penta-isobutoxy fluorene, penta-n-butyl Oxime, penta-2-butoxyfluorene, penta-butoxybutane, trimethyloxoxide vanadium (V), triethoxy vanadium oxide (V), triisopropoxide vanadium oxide (V), Tri-n-propanol vanadium oxide (V), triisobutanol vanadium oxide (V), tri-n-butanol vanadium oxide (V), tri-2-butanol vanadium oxide (V), tri-tert-butoxide vanadium oxide (V), triisopropoxy ruthenium, tri-n-butoxy ruthenium, tetramethoxy ruthenium, tetraethoxy ruthenium, tetraisopropoxy ruthenium, tetra-tert-butoxy fluorene; Beixing Chemical Industry Co., Ltd. Co., Ltd.'s pentaethoxy ruthenium, pentaethoxy ruthenium, pentabutoxy ruthenium, n-butanol oxime, t-butanol oxime; Nichia Chemicals Co., Ltd. Vanadium propoxide, vanadium oxy-n-butoxide, vanadium oxytriisobutoxide, vanadium oxy-t-butoxide, etc. .

In the case of preparing the compound of the formula (I), the preparation method can be carried out by a known method such as the presence of a halide of the metal element (M) contained in the compound of the formula (I) and an alcohol in an inert organic solvent. In the next step, a method of adding an ammonia or an amine compound to obtain a halogen is also known (for example, see JP-A-63-227593, JP-A-3-291247, and the like).

The content of the compound of the formula (I) contained in the composition for forming a passivation layer is appropriately selected as needed. In terms of preservation stability and passivation effect In the composition for forming a passivation layer, the content of the compound of the formula (I) may be set to 0.1% by mass to 80% by mass, preferably 0.5% by mass to 70% by mass, more preferably 1% by mass to 60% by mass. %, and further preferably 1% by mass to 50% by mass.

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

Specific examples of the β-diketone compound include acetamidineacetone, 3-methyl-2,4-pentanedione, 2,3-pentanedione, 3-ethyl-2,4-pentanedione, and 3-butyl Base-2,4-pentanedione, 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 the β-ketoester compound include methyl ethyl acetate, ethyl acetate, ethyl acetoacetate, isobutyl acetate, butyl acetate, and butyl acetate. Amyl acetate, isoamyl acetate, hexyl acetate, n-octyl acetate, heptyl acetate, 3-pentyl acetate, ethyl 2-ethylhydrazine heptanoate, 2- Ethyl butyl acetate, ethyl 4,4-dimethyl-3-oxopentanoate, ethyl 4-methyl-3-oxopentanoate, ethyl 2-ethylacetate, hexyl Ethyl acetate, methyl 4-methyl-3-oxopentanoate, isopropyl acetate, ethyl 3-oxohexanoate, ethyl 3-oxopentanoate, 3-oxopentane Methyl ester, methyl 3-oxohexanoate, 2-methylacetamidineacetic acid Ethyl ester, ethyl 3-oxoheptanoate, methyl 3-oxoheptanoate, methyl 4,4-dimethyl-3-oxopentanoate and the like.

Specific examples of the malonic acid diester include dimethyl malonate, diethyl malonate, dipropyl malonate, diisopropyl malonate, dibutyl malonate, and malonic acid di- Third butyl ester, dihexyl malonate, tert-butyl ethyl malonate, diethyl methyl malonate, diethyl ethyl malonate, diethyl isopropyl malonate, Diethyl butyl malonate, diethyl 2-butylmalonate, diethyl isobutylmalonate, diethyl 1-methylbutylmalonate, and the like.

In the case where the compound of the formula (I) has a chelate structure, the presence of its chelate structure can be confirmed by the analysis method generally used. For example, it can be confirmed using an infrared spectroscopic spectrum, a nuclear magnetic resonance spectrum, a melting point, or the like.

The compound of the formula (I) can also be used in the form of hydrolysis and dehydration polycondensation. In order to carry out hydrolysis and dehydration polycondensation, the reaction may be carried out in the presence of water and a catalyst, and water and a catalyst may be distilled off after hydrolysis and dehydration condensation. The catalyst can be exemplified by 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, and salicylate. Organic acids such as acid, benzoic acid, phthalic acid, oxalic acid, lactic acid, and succinic acid. Further, a base such as ammonia or an amine may be added as a catalyst.

The passivation layer forming composition may further contain a precursor of a specific metal oxide other than the compound of the formula (I). The precursor of the specific metal oxide is not particularly limited as long as it forms a specific metal oxide by heat treatment. Specific examples thereof include citric acid, cerium chloride, cerium oxide, cerium carbide, cerium hydroxide, ceric acid, cerium chloride, Antimony pentabromide, vanadium oxychloride, vanadium trioxide, vanadium oxybis(2,4-pentanedionate), barium chloride, barium nitrate, barium oxalate, barium stearate, barium carbonate, naphthenic Barium acid, barium propionate, barium nitrate, barium octoate, barium chloride, tetrakis(2,4-pentanedionate), and the like.

The composition for forming a passivation layer may further contain a metal oxide other than a specific metal compound or a precursor thereof. Examples of such a metal oxide or a precursor thereof include alumina, cerium oxide, titanium oxide, gallium oxide, zirconium oxide, boron oxide, indium oxide, phosphorus oxide, zinc oxide, cerium oxide, cerium oxide, cerium oxide, and cerium oxide. , cerium oxide, cerium oxide, cerium oxide, cerium oxide, cerium oxide, cerium oxide, cerium oxide, cerium oxide, cerium oxide, cerium oxide and precursors of such oxides. From the viewpoint of stability of the passivation effect, alumina, cerium oxide, titanium oxide, zirconium oxide, cerium oxide or precursors of these oxides are preferred, and oxidation is more preferable from the viewpoint of high passivation effect. Aluminum or its precursors.

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

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

[Chemical 3]

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

In the formula (II), R ² each independently represents an alkyl group having 1 to 8 carbon atoms, 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 a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a 2-butyl group, a tert-butyl group, a hexyl group, an octyl group, an ethylhexyl group, and the like. . In view of the storage stability and the passivation effect, the alkyl group represented by R ² is preferably an unsubstituted alkyl group having 1 to 8 carbon atoms, more preferably an unsubstituted carbon group having 1 to 4 carbon atoms. alkyl.

In the 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, more preferably 1 or 3. X ² and X ³ each independently represent an oxygen atom or a methylene group. From the viewpoint of storage stability, at least one of X ² and X ³ is preferably an oxygen atom.

R ³ , R ⁴ and R ⁵ in the formula (II) each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. The alkyl group represented by R ³ , R ⁴ and R ⁵ may be linear or branched. The alkyl group represented by R ³ , R ⁴ and R ⁵ may have a substituent or may be unsubstituted, and is preferably unsubstituted. The alkyl groups represented by R ³ , R ⁴ and R ⁵ are each independently an alkyl group having 1 to 8 carbon atoms, preferably an alkyl group having 1 to 4 carbon atoms. Specific examples of the alkyl group represented by R ³ , R ⁴ and R ⁵ include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, 2-butyl group, tert-butyl group, hexyl group and octyl group. Base, 2-ethylhexyl and the like. In view of the storage stability and the passivation effect, R ³ and R ⁴ in the formula (II) are preferably independently a hydrogen atom or an unsubstituted alkyl group having 1 to 8 carbon atoms, more preferably Preferably, it is a hydrogen atom or an unsubstituted alkyl group having 1 to 4 carbon atoms.

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

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

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

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

Specific examples of the trialkoxy aluminum compound represented by the general formula (II) and having an organoaluminum compound of 0 are: trimethoxy aluminum, triethoxy aluminum, triisopropoxy aluminum, and tri-2-butene. Aluminium oxyaluminum, mono-2-butoxydisisopropoxyaluminum, tri-t-butoxyaluminum, tri-n-butoxyaluminum, and the like.

Further, specific examples of the organoaluminum compound represented by the formula (II) and having n to 1 to 3 include aluminum ethylacetate diisopropylate and tris(ethylacetamethyleneacetate) aluminum (aluminum ethylacetoacetate diisopropylate). Tris(ethylacetoacetato)aluminum) and the like.

Further, the organoaluminum compound represented by the formula (II) and having n to 1 to 3 can be used as a preparation, and a commercially available product can also be used. Commercially available products include, for example, trade names ALCH, ALCH-50F, ALCH-75, ALCH-TR, and ALCH-TR-20 of Kawasaki Seika Co., Ltd.

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

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

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

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

The organoaluminum compound represented by the formula (II) and having n to 1 to 3 can be produced by mixing the above trialkoxyaluminum with a chelating agent. The chelating agent may be a compound having a specific structure of two carbonyl groups. Specifically, when the above aluminum trialkoxide is mixed with a compound having a specific structure of two carbonyl groups, at least a part of the alkoxide group of the trialkoxy aluminum is replaced with a compound having a specific structure to form a chelate aluminum structure. . At this time, a solvent may be present as needed, and heat treatment or addition of a catalyst may be performed. By combining at least a portion of the aluminum alkoxide structure with a chelated aluminum structure, organoaluminum compound The stability of the hydrolysis and polymerization reaction is improved, and the storage stability of the composition for forming a passivation layer containing the same is further improved.

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

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

In the organoaluminum compound represented by the formula (II), in terms of the passivation effect and compatibility with a solvent to be added as needed, specifically, it is preferred to use a mixture selected from ethyl acetoacetate At least one of the group consisting of aluminum propoxide and aluminum triisopropoxide is more preferably ethyl acetoacetate aluminum diisopropylate.

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

In the case where 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 above-described organoaluminum compound, the total amount of the above-mentioned aluminum compound in the composition for forming a passivation layer is The content ratio is preferably from 0.1% by mass to 80% by mass, more preferably from 10% by mass to 70% by mass. In view of the high passivation effect, the total ratio of the specific metal compound and the aluminum compound in the total amount of the aluminum compound is preferably 0.1% by mass or more and 99.9% by mass or less, more preferably 0.5% by mass or more and 99% by mass. % or less is further preferably 1% by mass or more and 95% by mass or less.

In the case where the composition for forming a passivation layer contains the above-described aluminum compound, the composition of the specific metal oxide in the passivation layer obtained by heat-treating the composition for forming a passivation layer may be, for example, Nb ₂ O ₅ -Al ₂ O ₃ , a binary composite oxide 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 or Al ₂ O ₃ —HfO ₂ ; Nb ₂ O ₅ − Al ₂ O ₃ -Ta ₂ O ₅ , Al ₂ O ₃ -Y ₂ O ₃ -Ta ₂ O ₅ , Nb ₂ O ₅ -Al ₂ O ₃ -V ₂ O ₅ , Al ₂ O ₃ -HfO ₂ -Ta ₂ O ₃ and other ternary composite oxides.

The passivation layer forming composition preferably contains a compound selected from the group consisting of Nb ₂ O ₅ and the compound of the above formula (I), wherein N is Nb, from the viewpoint of a high passivation effect and a temporal stability of the passivation effect. At least one indole compound in the group. In addition, the total content of the ruthenium compound in the composition for forming a passivation layer is preferably from 0.1% by mass to 99.9% by mass, more preferably from 1% by mass to 99% by mass, in terms of Nb ₂ O ₅ , more preferably from 1% by mass to 99% by mass. It is 5 mass% to 90 mass%. Specific metal oxidation in a passivation layer obtained by heat-treating a passivation layer-forming composition containing at least one antimony compound selected from the group consisting of Nb ₂ O ₅ and the compound of the above formula (I) wherein M is Nb Examples of the composition of the material include Nb ₂ O ₅ -Al ₂ O ₃ , Nb ₂ O ₅ -Ta ₂ O ₅ , Nb ₂ O ₅ -Y ₂ O ₃ , Nb ₂ O ₅ -V ₂ O ₅ , Nb ₂ O _a binary composite oxide such as _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 -Al ₂ O _a ternary composite oxide such as ₃ -V ₂ O ₅ or Nb ₂ O ₅ -HfO ₂ -Ta ₂ O ₅ .

A composition for forming a passivation layer containing a specific metal compound is applied onto a semiconductor substrate to form a composition layer of a desired shape, and the composition layer is subjected to heat treatment, whereby a passivation layer having an excellent passivation effect can be formed into a The shape you need.

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

(liquid medium)

The composition for forming a passivation layer preferably contains a liquid medium. Since the composition for forming a passivation layer contains a liquid medium, the adjustment of the viscosity becomes easier, the impartability is further improved, and a more uniform passivation layer can be formed. The liquid medium is not particularly limited as long as it can dissolve or disperse a specific metal compound, and may be appropriately selected as needed. Choose.

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, and methyl n-amyl ketone. Methyl n-hexyl ketone, diethyl ketone, dipropyl ketone, diisobutyl ketone, trimethyl fluorenone, cyclohexanone, cyclopentanone, methylcyclohexanone, 2,4-pentanedione, Ketone solvent such as acetone-acetone; diethyl ether, methyl ethyl ether, methyl n-propyl ether, diisopropyl ether, tetrahydrofuran, methyl tetrahydrofuran, dioxane, dimethyl dioxane, ethylene glycol Ether, ethylene glycol diethyl ether, ethylene glycol di-n-propyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, two 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, triethyl Diol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol methyl ethyl ether, triethylene glycol methyl n-butyl ether, triethylene glycol di-n-butyl ether, triethylene glycol methyl Ether, tetraethylene glycol dimethyl ether, tetraethylene glycol 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 methyl n-butyl ether, two Propylene 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, three Propylene glycol di-n-butyl ether, tripropylene glycol methyl n-hexyl ether, tetrapropylene glycol dimethyl ether, tetrapropylene glycol diethyl ether, tetrapropylene glycol methyl ethyl ether, tetrapropylene glycol methyl n-butyl ether, tetrapropylene glycol di-n-butyl ether, Ether solvent such as tetrapropylene glycol methyl n-hexyl ether; methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, 2-butyl acetate, n-amyl acetate, 2-pentyl acetate, 3-methoxybutyl acetate, methyl amyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, 2-(2-butoxyethoxy) acetate Ethyl ester, benzyl acetate, cyclohexyl acetate, methylcyclohexyl acetate, decyl acetate, methyl acetate, ethyl acetate, diethylene glycol methyl ether, diethylene glycol monoethyl acetate , dipropylene glycol methyl ether acetate, dipropylene glycol ethyl ether, diacetate glycol, methoxy triethylene 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-amyl lactate, ethylene glycol methyl ether propionate, ethylene glycol ether propionate, ethylene glycol Ether acetate, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, propylene glycol diethyl ether acetate, propylene glycol propyl ether acetate, γ-butyrolactone, γ-valerolactone Ester solvent; acetonitrile, N-methylpyrrolidone, N-ethylpyrrolidone, N-propylpyrrolidone, N-butylpyrrolidone, N-hexylpyrrolidone, N-cyclohexylpyrrolidone, N,N-dimethylformamidine Aprotic polar solvent such as amine, N,N-dimethylacetamide, dimethylhydrazine; dichloromethane, chloroform, dichloroethane, benzene, toluene, xylene, hexane, octane, Hydrophobic organic solvents such as benzene, 2-ethylhexanoic acid, methyl isobutyl ketone, methyl ethyl ketone; methanol, ethanol, n-propanol, 2-propanol, n-butanol, isobutanol, 2- Butanol, tert-butanol, n-pentanol, isoamyl alcohol, 2-methylbutanol, 2-pentanol, third pentanol, 3-methoxybutanol, n-hexanol, 2-methylpentanol , 2-hexanol, 2-ethylbutanol, 2-heptanol, n-octanol, 2-ethylhexanol, 2-octanol, n-nonanol, n-nonanol, 2-undecyl alcohol, three Methyl nonyl alcohol, 2-tetradecanol, 2-heptadecanol, ring Hexanol, methylcyclohexanol, isobornylcyclohexanol, benzyl alcohol, ethylene glycol, 1,2-propanediol, 1,3-butanediol, diethylene glycol, dipropylene glycol, triethylene glycol, Alcohol solvent such as 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, Glycol monoethers such as diethylene glycol mono-n-hexyl ether, ethoxy triethylene glycol, tetraethylene glycol mono-n-butyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, tripropylene glycol monomethyl ether Solvent; terpene solvent such as terpinene, terpineol, myrcene, allophymene, limonene, dipentene, decene, carbon, ocimene, and phellandrene Water, etc. These liquid mediums may be used alone or in combination of two or more.

The liquid medium preferably contains a solvent selected from the group consisting of terpene solvents, from the viewpoint of impartability to the semiconductor substrate and pattern formation property (suppression of the formation of the composition for forming the passivation layer and the coarsening of the pattern during drying). At least one of the group consisting of an ester solvent and an alcohol solvent is more preferably at least one selected from the group consisting of terpene solvents.

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

(resin)

The composition for forming a passivation layer preferably further contains at least one resin. a group formed by imparting a composition of the passivation layer to a semiconductor substrate by containing a resin The shape stability of the formed layer is further improved, and it is easier to selectively form the passivation layer in a desired shape in the region in which the above-described composition layer is formed.

The type of the resin is not particularly limited, and when the composition for forming a passivation layer is applied to the semiconductor substrate, the viscosity can be adjusted to a resin in a range in which good pattern formation can be performed. Specific examples of the resin include polyvinyl alcohol, polypropylene decylamine, polyvinyl decylamine, polyvinylpyrrolidone, polyethylene oxide, polyfluorene, polypropylene decylalkyl hydrazine, cellulose, and carboxymethyl group. Cellulose derivatives such as cellulose ethers such as cellulose, hydroxyethyl cellulose, and ethyl cellulose; gelatin and gelatin derivatives, starch and starch derivatives, sodium alginate and sodium alginate derivatives, and xanthan ) and Sanxian gum derivatives, guar gum and guar derivatives, scleroglucan and scleroglucan derivatives, tragacanth gum and xanthan gum derivatives , dextrin and dextrin derivatives, (meth)acrylic resins, (meth) acrylate resins (eg alkyl (meth) acrylate resin, dimethylaminoethyl (meth) acrylate) Resin, etc.), butadiene resin, styrene resin, decane resin, copolymers of these, and the like. These resins may be used alone or in combination of two or more.

Among these resins, from the viewpoint of storage stability and pattern formation, it is preferred to use a neutral resin having no acidic or basic functional groups, and it is easy to adjust even when the content is small. From the viewpoint of viscosity and thixotropy, it is more preferred to use a cellulose derivative.

The molecular weight of the resin is not particularly limited, and it is preferably appropriately adjusted in consideration of the desired viscosity as a composition for forming a passivation layer. View on preservation stability and pattern formation The weight average molecular weight of the above resin is preferably from 1,000 to 10,000,000, more preferably from 3,000 to 5,000,000. Further, the weight average molecular weight of the resin was determined by conversion using a calibration curve of standard polystyrene by a molecular weight distribution measured by Gel Permeation Chromatography (GPC). The calibration curve was obtained in a three-times approximation using five sample sets of standard polystyrene (PStQuick MP-H, PStQuickB [Tosoh Corporation, trade name]). The measurement conditions of GPC are shown below.

Device: (Pump: L-2130 [Hitachi High-Technologies Co., Ltd.])

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

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

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

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

Dissolution: tetrahydrofuran

Sample concentration: 10mg/2mL

Injection volume: 200μL

Flow rate: 2.05mL/min

Measuring temperature: 25 ° C

When the composition for forming a passivation layer contains a resin, the passivation layer is formed. The content of the resin in the composition can be appropriately selected as needed. For example, the total mass of the composition for forming a passivation layer is preferably 0.1% by mass to 30% by mass. The content ratio is preferably from 1% by mass to 25% by mass, more preferably from 1.5% by mass to 20% by mass, even more preferably 1.5% by mass, from the viewpoint of exhibiting thixotropy such as pattern formation more easily. ~10% by mass.

In the case where the composition for forming a passivation layer contains a resin, the content ratio of the organoaluminum compound to the resin in the composition for forming a passivation layer may be appropriately selected as necessary. In the viewpoint of pattern formation property and storage stability, the total amount of one or more selected from the group consisting of alumina and its precursor, which is contained in a specific metal compound and optionally, is set to 1. In the case, the ratio of the resin is preferably from 0.001 to 1,000, more preferably from 0.01 to 100, and still more preferably from 0.1 to 1.

The composition for forming a passivation layer may also contain an acidic compound or a basic compound. When the composition for forming a passivation layer contains an acidic compound or a basic compound, the content of the acidic compound or the basic compound in the composition for forming a passivation layer is preferably 1 in terms of storage stability. The mass% or less is more preferably 0.1% by mass or less.

The acidic compound may be listed as a Brilliant acid and a Lewis acid. Specific examples thereof include inorganic acids such as hydrochloric acid and nitric acid; and organic acids such as acetic acid. Further, examples of the basic compound include a Bruce base and a Lewis base. Specific examples thereof include inorganic bases such as alkali metal hydroxides and alkaline earth metal hydroxides; and organic bases such as trialkylamine and pyridine.

The composition for forming a passivation layer may optionally contain various additives such as a thickener, a wetting agent, a surfactant, an inorganic powder, a halogen-containing resin, and a thixotropic agent. Additives as other ingredients.

The inorganic powder may, for example, be cerium oxide (cerium oxide), clay, cerium carbide, cerium nitride, montmorillonite, bentonite, carbon black or the like. Among these inorganic powders, a filler containing cerium oxide as a component is preferably used. Here, the so-called clay means a layered clay mineral, and specific examples thereof include kaolinite, imagolite, montmorillonite, smectite, sericite, and illite. ), talc, stevensite, zeolite, and the like. When the composition for forming a passivation layer contains an inorganic powder, the imparting property of the composition for forming a passivation layer tends to be improved.

Examples of the surfactant include a nonionic surfactant, a cationic surfactant, and an anionic surfactant. Among them, a nonionic surfactant or a cationic surfactant is preferred in that the amount of impurities such as heavy metals introduced into the semiconductor element is small. Examples of the nonionic surfactant include a fluorene-based surfactant, a fluorine-based surfactant, and a hydrocarbon-based surfactant. When the composition for forming a passivation layer contains a surfactant, the thickness of the composition layer formed by the composition for forming a passivation layer and the uniformity of composition tend to be improved.

The ruthenium-containing resin can be exemplified by an amino acid-modified fluorenone, a polyamido-fluorenone alternating copolymer, a side chain alkyl fluorenone, a side chain polyether fluorenone, and a terminal alkyl group. The fluorenone, the fluorenone modified polytriglucose, the fluorenone modified acrylic resin, and the like. When the composition for forming a passivation layer contains a resin containing ruthenium, the thickness of the composition layer formed by the composition for forming a passivation layer and the uniformity of composition tend to be improved.

The thixotropic agent may, for example, be a polyether compound, a fatty acid decylamine, a smoked cerium oxide, a hydrogenated castor oil, a urea amide decylamine, a polyvinylpyrrolidone, an oil gelling agent or the like. When the composition for forming a passivation layer contains a thixotropic agent, the pattern formation property at the time of providing a composition for forming a passivation layer tends to be improved. The polyether compound can be exemplified by polyethylene glycol, polypropylene glycol, poly(ethylidene-propyl) 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 the method of applying the semiconductor substrate or the like. For example, the viscosity of the composition for forming a passivation layer can be set to 0.01 Pa. s~10000Pa. s. Among them, the viscosity of the composition for forming a passivation layer is preferably 0.1 Pa from the viewpoint of pattern formation. s~1000Pa. s. Further, the above viscosity was a value measured by using a rotary shear viscometer at a shear rate of 1.0 s ^-1 at 25 °C.

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

The method for producing the composition for forming a passivation layer is not particularly limited. For example, it can be produced by mixing a specific metal compound with a liquid medium or the like which is optionally contained by a method generally used. Alternatively, it may be produced by mixing a liquid medium in which a resin is dissolved with a specific metal compound.

Further, the specific metal compound may also be a compound of the formula (I), and the formula (I) The compound in which the metal element is formed into a chelate compound is mixed and prepared. In this case, a solvent may be used as appropriate or may be subjected to heat treatment. The composition for forming a passivation layer can also be produced using the specific metal compound thus prepared.

Further, the components contained in the composition for forming a passivation layer and the content of each component may be subjected to thermal analysis such as thermogravimetric-differential thermal analysis (TG/DTA) or nuclear magnetic resonance (Nuclear Magnetic Resonance). , NMR, infrared spectroscopy (IR) and other spectral analysis, high performance liquid chromatography (HPLC), gel permeation chromatography (GPC) and other chromatographic analysis to confirm .

<Method of Manufacturing Solar Cell Element>

The method for producing a solar cell element according to the present invention includes the step of diffusing the p-type diffusion on 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. a step of forming a first metal electrode on at least a portion of the region and forming a second metal electrode on at least a portion of the n-type diffusion region; and forming a passivation layer in a portion or all of a region of the back surface of the semiconductor substrate a step of forming a composition layer comprising at least one selected from the group consisting of a specific metal oxide and a compound represented by the general formula (I); and the composition layer A heat treatment is performed to form a passivation layer containing at least one specific metal oxide. The method of manufacturing the solar cell element of the present invention may further include other steps as needed.

According to the above method, a passivation layer having an excellent passivation effect can be formed on a semiconductor substrate. Further, the passivation layer can be formed by a simple and highly productive method which does not require a vapor deposition device or the like, and can be formed into a desired shape without complicated steps such as masking treatment. Therefore, according to the above method, a solar cell element excellent in conversion efficiency can be manufactured by a simple method.

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

The method of forming the composition layer by providing a composition for forming a passivation layer containing a specific metal compound on a part or all of the back surface of the semiconductor substrate is not particularly limited. Specific examples thereof include a printing method such as a dipping method and a screen printing method, a spin coating method, a brush coating method, a spray method, a doctor blade method, a roll coating method, and an inkjet method. Among these methods, from the viewpoint of pattern formability, a printing method and an inkjet method are preferred, and a screen printing method is more preferred.

The amount of the composition for forming a passivation layer to the semiconductor substrate can be appropriately selected depending on the purpose. For example, the thickness of the passivation layer formed can be the desired thickness The way is properly adjusted.

The composition layer formed by applying the composition for forming a passivation layer onto the semiconductor substrate is heat-treated to form a heat-treated material layer derived from the composition layer, whereby a passivation layer can be formed on the semiconductor substrate.

The heat treatment conditions of the composition layer are not particularly limited as long as the specific metal compound contained in the composition for forming a passivation layer can be converted into a specific metal oxide. For example, there is no particular limitation as long as the compound represented by the formula (I) contained in the composition layer can be converted into a specific metal oxide as a heat-treated product thereof. Among them, a condition in which an amorphous specific metal oxide layer having no crystal structure is formed is preferable. By forming the passivation layer from an amorphous specific metal oxide, the passivation layer can be more effectively negatively charged, so that 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 further preferably 600 ° C to 800 ° C. The heat treatment time can be appropriately selected depending on the heat treatment temperature and the like. For example, it can be set to 5 seconds to 10 hours, preferably 10 seconds to 5 hours.

Density of the passivation layer is preferably ^{1.0g / cm 3 ~ 10.0g / cm} 3, more preferably ^{2.0g / cm 3 ~ 8.0g / cm} 3, and thus good for the ^{3.0g / cm 3 ~ 7.0g / cm} 3. When the density of the passivation layer is from 1.0 g/cm ³ to 10.0 g/cm ³ , a sufficient passivation effect can be obtained, and a high passivation effect tends to be difficult to change with time. It is presumed that the reason is that if the density of the passivation layer is 1.0 g/cm ³ or more, external moisture and impurity gases are less likely to reach the interface between the semiconductor substrate and the passivation layer, so that it is easy to maintain the passivation effect; if the density of the passivation layer is 10.0 g When it is /cm ³ or less, the interaction with the semiconductor substrate tends to increase. The method for measuring the density of the passivation layer includes a method of measuring the mass and volume of the passivation layer to calculate the density; X-ray reflectance method is used to make the X-ray incident on the surface of the sample at a very shallow angle, which is at the incident angle pair. The X-ray intensity distribution reflected in the mirror direction is measured, and the measured distribution is compared with the simulation result, and the simulation parameters are optimized to determine the film thickness and density of the sample.

The average thickness of the passivation layer is preferably from 5 nm to 50 μm, more preferably from 20 nm to 20 μm, and still more preferably from 30 nm to 5 μm. When the average thickness of the passivation layer is 5 nm or more, a sufficient passivation effect is easily obtained, and when it is 50 μm or less, the element structure tends to be designed in consideration of other members constituting the solar cell element.

The average thickness of the passivation layer was set to an arithmetic mean of the thickness of 5 points measured using an interferometric film thickness meter.

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

Fig. 2 is a cross-sectional view showing a step diagram schematically showing an example of a method of manufacturing a solar cell element having the passivation layer of the present embodiment. However, this step chart does not limit the invention in any way.

As shown in FIG. 2(a), an n ⁺ -type diffusion layer 12 is formed on the light-receiving surface side of the n-type semiconductor substrate 11, and an anti-reflection film 13 is formed on the outermost surface of the light-receiving surface side. There is formed a p-type diffusion region of p ⁺ -type diffusion layer 14 and an n-type diffusion region of n ⁺ type diffusion layer 12 on the back surface. In addition, (a) of FIG. 2 is a cross-sectional view when the semiconductor substrate having the back electrode structure shown in FIG. 1 is cut along the line AA.

The p-type diffusion region 14 can be formed by, for example, imparting 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. In addition, the n-type diffusion region 12 can be formed by, for example, imparting an n-type diffusion layer forming composition capable of forming an n ⁺ -type diffusion layer by thermal diffusion treatment to a desired region. The composition for forming an n-type diffusion layer may, for example, be a composition containing a substance containing a donor element and a glass component. Examples of the antireflection film 13 include a tantalum nitride film, a titanium oxide film, and the like. Further, a surface protective film (not shown) such as a ruthenium oxide film may be further present between the anti-reflection film 13 and the p-type semiconductor substrate 11. Further, the above passivation layer can also be used as the surface protective film.

Then, as shown in FIG. 2(b), the first metal electrode 15 and the 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-treating a paste for electrode formation which is generally used, such as a silver electrode paste, an aluminum electrode paste, and a copper electrode paste. Further, the first metal electrode 15 and the p-type diffusion region 14 may be formed by heat-treating a material for forming an electrode such as an aluminum electrode paste.

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

Then, as shown in (c) of FIG. 2, on the back of the n-type semiconductor substrate 11 In the region other than the region in which the first metal electrode 15 and the second metal electrode 17 are formed, a composition for forming a passivation layer is formed to form a composition layer. The method of imparting is not particularly limited and can be selected from known methods. Specific examples thereof include a printing method such as a dipping method and a screen printing method, a spin coating method, a brush coating method, a spray method, a doctor blade method, a roll coating method, and an inkjet method. Among these methods, from the viewpoint of pattern formability, a printing method and an inkjet method are preferred, and a screen printing method is more preferred. The amount of the composition for forming the passivation layer can be appropriately selected depending on the purpose. For example, it can be appropriately adjusted so that the thickness of the formed passivation layer becomes the above-mentioned preferable thickness.

Further, between the step of imparting a composition for forming a passivation layer and the step of forming a passivation layer by heat treatment, a step of drying the composition layer containing the composition for forming a passivation layer may be further included. By having a step of drying the composition layer, there is a tendency to form a passivation layer having a more uniform passivation effect.

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

Finally, the composition layer formed on the back surface of the n-type semiconductor substrate 11 is subjected to heat treatment to form a passivation layer 16. The heat treatment conditions of the composition layer are as described above. The solar cell element of the present invention can thus be fabricated.

Since the solar cell element having the structure shown in FIG. 2 does not have an electrode on the light-receiving surface side, the area of the light-receiving region can be increased, and the power generation efficiency is excellent. Further, by By forming a passivation layer on the back surface using the composition for forming a passivation layer, a solar cell element having more excellent power generation efficiency can be obtained.

In FIG. 2(c), a passivation layer is formed only on the back surface of the n-type semiconductor substrate 11, but a passivation layer (not shown) may be further formed on the side surface (edge) in addition to the back surface. Thereby, a solar cell element having more excellent power generation efficiency can be manufactured. When the passivation layer is used for a portion having many crystal defects such as a side surface, the effect is particularly large.

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

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

After the via holes are formed, the damaged layer generated by irradiating the semiconductor substrate with the laser light is removed by etching, and the p-type diffusion region 14 is formed on the desired region on the back surface. Then, an n-type diffusion region 12 is formed on the light receiving surface. P-type diffusion region The first metal electrode 15 and the second metal electrode 17 are formed on the domain 14 and the n-type diffusion region 12, respectively. Then, a passivation layer 16 is formed in the region of the back surface where the electrode is not formed. The method of forming the p-type diffusion region, the n-type diffusion region, the electrode, and the passivation layer can be set to be the same as the above method. The passivation layer 16 may be formed on the back surface of the semiconductor substrate or 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 a solar cell element having a via hole type back contact structure shown in Fig. 4; The cross-sectional view taken along line BB in Fig. 5 corresponds to Fig. 4. The description of the passivation layer 16 is omitted in FIG.

<Solar battery module>

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

[Examples]

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

<Example 1>

(Preparation of a composition for forming a passivation layer)

Al ₂ O ₃ film coating material (High Purity Chemical Research Institute Co., Ltd., SYM-A104, Al ₂ O ₃ : 2% by mass, xylene: 87% by mass, 2-propanol: 5% by mass, stabilizer) : 6 mass %) 1.0 g, Nb ₂ O ₅ film coating material (High Purity Chemical Research Institute Co., Ltd., Nb-05, Nb ₂ O ₅ : 5 mass%, n-butyl acetate: 56% by mass, stabilizer : 16.5 mass%, viscosity adjuster: 22.5 mass%) 1.0 g of the mixture, and the composition 1 for passivation layer formation was prepared.

(formation of passivation layer)

A single crystal type p-type ruthenium substrate (Mitsubishi Sumitomo (SUMCO) Co., Ltd., 50 mm square, thickness: 625 μm) having a mirror-shaped surface was used as the semiconductor substrate. The ruthenium substrate was immersed at 70 ° C for 5 minutes and washed with an RCA cleaning solution (Kanto Chemical Co., Ltd., Frontier Cleaner - A01) to carry out pretreatment.

Thereafter, the passivation layer-forming composition 1 obtained above was applied to the pretreated ruthenium substrate at a temperature of 4000 rpm (min ^-1 ) for 30 seconds using a spin coater (Sanken Co., Ltd., MS-100). The single side of the single face. Thereafter, drying treatment was performed at 150 ° C for 3 minutes. Then, after heat-treating at 700 ° C for 10 minutes in the air, it was left to cool at room temperature (25 ° C) to prepare a substrate for evaluation having a passivation layer.

(Measurement of effective life)

The life measuring device (Semilab Co., Ltd., WT-2000PVN) was passivated by the reflection microwave photoconduction attenuating method at room temperature (25 ° C) to form the substrate for evaluation obtained above. The effective life (μs) of the layer area was measured. The effective life is 480μs.

(measurement of average thickness)

Using an interferometric film thickness meter (Filmetrics, Inc., F20 film thickness measurement system) The thickness of the passivation layer was measured at five points in the plane, and the average value was calculated. The average value is 82 nm.

(Measurement of density)

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

(Manufacturing method of solar cell element)

Using the composition for forming a passivation layer obtained above, a solar cell element having a via-type back contact structure as shown in FIG. 4 was produced. Specifically, a penetrating hole was used to form a 0.2/cm ² penetrating n-type semiconductor substrate 11 (Advantec Co., Ltd., 125 mm square, thickness: 200 μm, after slicing (as-sliced) A through hole having a diameter of 100 μm on both sides of the n-type ruthenium substrate). 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. Thereafter, it was treated with an 8 mass% aqueous sodium hydroxide solution at 60 ° C for 10 minutes to form a texture on both faces. Then, using a diffusion furnace (Guangyang Thermal Systems Co., Ltd., 206A-M100), the n-type diffusion layer 12 was formed on the entire surface by treatment with POCl ₃ at 870 ° C for 20 minutes. 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, an inkjet device (Microjet Co., Ltd., MJP-1500V, inkjet head: IJH-80, nozzle size: 50 μm × 70 μm) was used to impart a composition for forming a passivation layer to the entire light-receiving surface. The surface of the surface and the back surface were formed in a region other than the predetermined region, and dried at 150 ° C to form a composition layer. Thereafter, heat treatment was performed at 700 ° C to form a passivation layer 16 containing Nb ₂ O ₅ and Al ₂ O ₃ .

Then, tantalum nitride is vapor-deposited on the light-receiving semiconductor passivation layer 16, whereby the anti-reflection film 13 is formed. Furthermore, the n-type diffusion regions 12 are also formed on a portion of the inside and the back of the via hole, respectively. Then, a silver electrode paste (DuPont Co., Ltd., PV159A) diluted with terpineol was added to the inside of the through-hole by an inkjet method, and the electrodes inside the through-hole were also screen-printed on the light-receiving side. The conductive pattern is applied to the silver electrode paste.

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

Using a tunnel furnace (Noritake Co., Ltd.), the n-type ruthenium substrate 11 to which the silver electrode paste and the aluminum electrode paste were applied was subjected to a maximum temperature of 800 ° C and a holding time of 10 seconds in an atmosphere. The heat treatment is performed to produce a solar cell element in which the first metal electrode 15 and the second metal electrode 17 are formed. The first metal electrode 15 is formed on the portion to which the aluminum electrode paste is applied, and the p-type diffusion region 14 is formed by diffusion of aluminum into the inside of the n-type germanium substrate 11.

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

The evaluation is to simulate sunlight (device name: WXS-155S-10, Wacom Electric Co., Ltd.) and voltage-current (IV) evaluation tester (device name: IV curve plotter (IV CURVE) The measurement device of TRACER) MP-160, Yinghong Seiki Co., Ltd.) was combined. Jsc (short-circuit current density), Voc (open circuit voltage), FF (shape factor), and Eff1 (conversion efficiency) which are power generation performances of solar cells are respectively based on Japanese Industrial Standards (JIS)-C-8913 ( It was obtained by measuring in fiscal year 2005 and JIS-C-8914 (2005).

The results are shown in Table 2. Furthermore, the mask was covered so that the light receiving area became 125 mm × 125 mm. In addition, the produced solar cell element was evaluated for its power generation characteristics after being stored in a constant temperature and humidity chamber of 50° C. and 80% RH for one month. The results are shown in Table 3. The conversion efficiency after storage of the solar cell element was 98.8% of the conversion efficiency Eff2 before storage, and the conversion efficiency was reduced by 1.2%.

<Example 2>

(Preparation of a composition for forming a passivation layer)

Ta ₂ O ₅ film coating material (High Purity Chemical Research Co., Ltd., Ta-10-P, Ta ₂ O ₅ : 10% by mass, n-octane: 9% by mass, n-butyl acetate: 60% by mass) Stabilizer: 21% by mass) as the composition 2 for forming a passivation layer.

A passivation layer was formed on the pretreated ruthenium substrate in the same manner as in Example 1 except that the above-described passivation layer-forming composition 2 was used, and an evaluation substrate was produced, and evaluation was performed in the same manner as in Example 1. The effective life is 450 μs. The average thickness and density of the passivation layer were 75 nm and 3.6 g/cm ³ , respectively.

A solar cell element was produced in the same manner as in Example 1 except that the composition 2 for passivation layer formation was used instead of the composition for forming the passivation layer, and the power generation characteristics were evaluated. The results are shown in Tables 2 and 3. The conversion efficiency of the solar cell element after storage was 98.2% of the conversion efficiency before storage, and the conversion efficiency was reduced by 1.8%.

<Example 3>

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

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

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

<Example 4>

Y ₂ O ₃ film coating material (High Purity Chemical Research Institute Co., Ltd., Y-03, Y ₂ O ₃ : 3 mass%, 2-ethylhexanoic acid: 12.5% by mass, n-butyl acetate: 22.5 mass %, ethyl acetate: 8 mass%, terpinic oil: 45 mass%, viscosity modifier: 9 mass%) was used as the composition 4 for passivation layer formation.

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

A solar cell element was produced in the same manner as in Example 1 except that the composition for forming the passivation layer 4 was used instead of the composition for forming the passivation layer, and the power generation characteristics were evaluated. The results are shown in Tables 2 and 3. The conversion efficiency of the solar cell element after storage was 97.6% of the conversion efficiency before storage, and the conversion efficiency was reduced by 2.4%.

<Example 5>

Ethylacetamidine acetate diisopropoxide aluminum (Kawasaki Seiki Co., Ltd., ALCH), pentaethoxy bismuth (Beixing Chemical Industry Co., Ltd.), acetamidine acetone (Wako Pure Chemical Industries Co., Ltd.), Xylene (Wako Pure Chemical Industries Co., Ltd.), 2-propanol (Wako Pure Chemical Industries Co., Ltd.), and terpineol (Nippon Terpene Chemical Co., Ltd.) were mixed in such a manner as to show the ratio shown in Table 1. It is used as the composition 5 for forming a passivation layer.

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

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

<Comparative Example 1>

In the first embodiment, the substrate for evaluation was produced in the same manner as in Example 1 except that the composition for forming the passivation layer was not applied, and the evaluation was carried out in the same manner as in Example 1. The effective life is 20μs.

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

<Comparative Example 2>

6.0 g of ethyl cellulose (The Dow Chemical Company, STD200) and 34.0 g of terpineol (manufactured by Nippon Terpene Chemical Co., Ltd., terpineol-LW) were mixed and mixed at 150 ° C. After dissolving for 2 hours, 15 parts by mass of an ethylcellulose/terpineol solution was prepared. Then, Al ₂ O ₃ particles (High Purity Chemical Research Co., Ltd., average particle diameter: 1 μm) 2.00 g, terpineol 3.9 g, and 15 parts by mass of the ethyl cellulose/terpineol solution prepared above were prepared. Composition 4.1 was mixed to prepare a composition C2.

A passivation layer was formed on the pretreated ruthenium substrate in the same manner as in Example 1 except that the composition C2 prepared above was used to prepare an evaluation substrate, and evaluation was performed in the same manner as in Example 1. The effective life is 21 μs. The average thickness and density of the passivation layer were 2.1 μm and 1.4 g/cm ³ , respectively. The average thickness of the passivation layer was measured using a stylus type step meter (Ambios, XP-2). Specifically, a part of the passivation layer was shaved with a small shovel, and the step of the remaining portion of the passivation layer and the cut portion was measured under the conditions of a speed of 0.1 mm/s and a needle load of 0.5 mg. Three measurements were performed, and the average value was calculated as the film thickness.

A solar cell element was produced in the same manner as in Example 1 except that the composition C2 prepared above was used instead of the composition 1 for forming a passivation layer, and the power generation characteristics were evaluated. The results are shown in Tables 2 and 3. The conversion efficiency of the solar cell element after storage was 93.0% of the conversion efficiency before storage, and the conversion efficiency was reduced by 7.0%.

<Comparative Example 3>

2.01 g of tetraethoxy decane, the above-prepared 15 parts by mass of ethylcellulose/terpineol solution 4.02 g, and terpineol 3.97 g were mixed to prepare a colorless transparent composition C3.

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

A solar cell element was produced 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 the power generation characteristics were evaluated. The results are shown in Tables 2 and 3. The conversion efficiency of the solar cell element after storage was 92.4% of the conversion efficiency before storage, and the conversion efficiency was reduced by 7.6%.

As described above, the solar cell element of the present invention contains a passivation layer having an excellent passivation effect, so that high conversion efficiency is exhibited, and deterioration of temporal solar cell characteristics is suppressed. It is then known that the passivation layer of the solar cell element of the present invention can be formed into a desired shape by a simple procedure.

<Reference Embodiment 1>

The following is a passivation film, a coating material, a solar cell element, and a tantalum substrate with a passivation film according to the first embodiment.

<1> A passivation film containing aluminum oxide and cerium oxide for use in a solar cell element having a ruthenium substrate.

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

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

The passivation film of any one of <1> to <3> further contains an organic component.

The passivation film according to any one of <1> to <4> which is a heat-treated material of a coating material containing an alumina precursor and a cerium oxide precursor.

<6> A coating type material comprising an alumina precursor and a cerium oxide precursor for forming a passivation film of a solar cell element having a ruthenium substrate.

<7> A solar cell element comprising: a p-type germanium substrate comprising a single crystal germanium or a polycrystalline germanium, having a light receiving surface and a back surface opposite to the light receiving surface; and an n-type impurity diffusion layer formed on the light receiving surface side of the germanium substrate a first electrode formed on a surface of the n-type impurity diffusion layer on the light-receiving surface side of the ruthenium substrate, and a passivation film formed on a surface on the back surface side of the ruthenium substrate, having a plurality of openings and containing alumina And the second electrode is electrically connected to a surface on the back side of the tantalum substrate via the plurality of openings.

<8> A solar cell element comprising: a p-type germanium substrate comprising a single crystal germanium or a polycrystalline germanium, having a light receiving surface and a back surface opposite to the light receiving surface; and an n-type impurity diffusion layer formed on the light receiving surface side of the germanium substrate a first electrode formed on a surface of the n-type impurity diffusion layer on a light-receiving surface side of the germanium substrate; The p-type impurity diffusion layer is formed on a part or all of the back surface side of the tantalum substrate, and impurities are added at a higher concentration than the tantalum substrate; and the passivation film is formed on the surface on the back side of the tantalum substrate. The openings include aluminum oxide and ruthenium oxide, and the second electrode is electrically connected to the surface of the p-type impurity diffusion layer on the back side of the ruthenium substrate via the plurality of openings.

<9> A solar cell element comprising: an n-type germanium substrate comprising a single crystal germanium or a polycrystalline germanium, having a light receiving surface and a back surface opposite to the light receiving surface; and a p-type impurity diffusion layer formed on the light receiving surface side of the germanium substrate a second electrode formed on a back surface side of the ruthenium substrate, and a passivation film formed on a surface of the ruthenium substrate on the light-receiving surface side, having a plurality of openings, containing aluminum oxide and ruthenium oxide, and a first electrode formed The surface of the p-type impurity diffusion layer on the light-receiving surface side of the ruthenium substrate is electrically connected to the surface on the light-receiving surface side of the ruthenium substrate via the plurality of openings.

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

The solar cell element according to any one of the above aspects, wherein the total content of the cerium oxide and the aluminum oxide in the passivation film is 90% by mass or more.

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

According to the above-described reference embodiment, the passivation film which has a carrier life of the ruthenium substrate and has a negative fixed charge can be realized at 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 germanium substrate with a passivation film which has a long carrier life and a negative fixed charge can be realized at low cost.

The passivation film of this embodiment is a passivation film used for a tantalum solar cell element, and contains aluminum oxide and ruthenium oxide.

Further, in the present embodiment, the amount of fixed charge of the film can be controlled by changing the composition of the passivation film.

Further, from the viewpoint of stabilizing the negative fixed charge, it is more preferable that the mass ratio of cerium oxide to aluminum oxide is 30/70 to 80/20. Further, from the viewpoint of making the negative fixed charge more stable, it is preferable that the mass ratio of cerium oxide to aluminum oxide is 35/65 to 70/30. Further, from the viewpoint of improving the life of the carrier and the negative fixed charge, the mass ratio of cerium oxide to aluminum oxide is preferably 50/50 to 90/10.

The mass ratio of cerium oxide to aluminum oxide in the passivation film can be determined by Energy Dispersive X-ray spectroscope (EDX), Secondary Ion Mass Spectrometer (SIMS) and high frequency. Inductively coupled plasma-mass Spectrometry, ICP-MS). The specific measurement conditions are as follows. Dissolving the passivation film in an acid or alkaline aqueous solution, forming the solution into a mist and introducing it into the Ar plasma, and splitting the light emitted by the excited element back to the ground state to measure the wavelength and intensity, according to the obtained The wavelength is used to characterize the element, and the amount is quantified based on the obtained intensity.

The total content of cerium 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 of cerium oxide and aluminum oxide in the passivation film are increased, the effect of negatively fixing charges becomes large.

The total content of cerium oxide and aluminum oxide in the passivation film can be determined by combining thermogravimetric analysis, fluorescent X-ray analysis, ICP-MS, and X-ray absorption spectroscopy. The specific measurement conditions are as follows. The ratio of the inorganic component was calculated by thermogravimetric analysis, and the ratio of cerium to aluminum was calculated by fluorescence X-ray or ICP-MS analysis, and the ratio of the oxide was examined by X-ray absorption spectroscopy.

Further, in the passivation film, from the viewpoint of improving the film quality or adjusting the elastic modulus, components other than cerium oxide and aluminum oxide can be contained in the form of an organic component. The presence of the organic component in the passivation film can be confirmed by elemental analysis and Fourier transform infrared spectroscopy (FT-IR) measurement of the film.

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

The passivation film can also be coated with an alumina precursor and a cerium oxide precursor. Obtained in the form of a heat treated material of the cloth material. The coating type material will be described in detail below.

The coating material of the present embodiment contains an alumina precursor and a cerium oxide precursor, and is used to form a passivation film for a solar cell element having a ruthenium substrate.

The alumina precursor can be used without particular limitation as long as it forms alumina. The alumina precursor preferably uses an organic alumina precursor in terms of uniform dispersion of alumina on the tantalum substrate and chemical stability. Examples of the organic alumina precursors include aluminum triisopropoxide (structural formula: Al(OCH(CH ₃ ) ₂ ) ₃ ), SYM-AL04 of High Purity Chemical Research Institute Co., Ltd., and the like.

The cerium oxide precursor can be used without particular limitation as long as it forms cerium oxide. From the viewpoint of uniformly dispersing cerium oxide on the cerium substrate and chemical stability, the cerium oxide precursor is preferably an organic cerium oxide precursor. Examples of the organic cerium oxide precursor include cerium (V) (structural formula: Nb(OC ₂ H ₅ ) ₅ , molecular weight: 318.21), and Nb-05 of the High Purity Chemical Research Institute.

A coating type material containing an organic cerium oxide precursor and an organic alumina precursor is formed into a film by a coating method or a printing method, and the organic component is removed by heat treatment (calcination) thereafter. Passivation film. Therefore, the result may also be a passivation film containing an organic component.

<Structure Description of Solar Cell Components>

The structure of the solar cell element of the present embodiment will be described with reference to Figs. 7 to 10 . 7 to 10 show the use of the blunt surface on the back surface of this embodiment. A cross-sectional view of a first configuration example to a fourth configuration example of a solar battery element of a chemical film.

As the tantalum substrate (crystalline germanium substrate, semiconductor substrate) 101 used in the present embodiment, any of single crystal germanium or polycrystalline germanium can be used. Further, as the tantalum substrate 101, any of a crystalline germanium having a p-type conductivity type or a crystalline germanium having a conductivity type n-type can be used. From the viewpoint of further exerting the effects of the present embodiment, it is more preferable that the conductivity type is a p-type crystal ruthenium.

In the following FIGS. 7 to 10, an example in which a p-type single crystal germanium is used as the germanium substrate 101 will be described. In addition, the single crystal germanium or polycrystalline germanium used in the germanium substrate 101 may be any, preferably having a resistivity of 0.5 Ω. Cm~10Ω. Cm single crystal germanium or polycrystalline germanium.

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

Further, the solar cell element of the present embodiment may have the light-receiving surface anti-reflection film 103 or may not have the light-receiving surface anti-reflection film 103. Further, in order to reduce the reflectance of the surface on the light-receiving surface of the solar cell element, it is preferable to form a concavo-convex structure (texture structure), and the solar cell element of the present embodiment may have a texture structure or may not have Has a texture structure.

On the other hand, a back surface field (BSF) layer which is a layer doped with a group III element such as aluminum or boron is formed on the back side (the lower side, the second surface, and the back surface of the substrate) 101. 104. However, the solar cell element of the present embodiment may have the BSF layer 104 or may not have the BSF layer 104.

In order to contact (electrically connect) the BSF layer 104 (the surface on the back side of the ruthenium substrate 101 when the BSF layer 104 is not present) on the back surface side of the ruthenium substrate 101, a second layer made of aluminum or the like is formed. Electrode 106 (electrode on the back side, second surface electrode, back surface electrode).

Then, in FIG. 7 (the first configuration example), a contact region electrically connected to the second electrode 106 is provided in addition to the BSF layer 104 (the surface on the back side of the ruthenium substrate 101 when the BSF layer 104 is not present). A passivation film (passivation layer) 107 containing aluminum oxide and cerium oxide is formed in a portion other than the opening OA). The passivation film 107 of the present embodiment may have a negative fixed charge. By this fixed electric charge, electrons, which are a minority carrier in the carrier generated in the crucible substrate 101 by light, are reflected back to the surface side. Therefore, the short-circuit current is increased, and the photoelectric conversion efficiency can be expected to be improved.

Next, a second configuration example shown in FIG. 8 will be described. In FIG. 7 (first configuration example), the second electrode 106 is formed on the entire surface of the contact region (opening portion OA) and the passivation film 107, and in FIG. 8 (second configuration example), only the contact is made. The second electrode 106 is formed in the region (opening OA). It is also possible to adopt a configuration in which the second electrode 106 is formed on only a part of the contact region (opening OA) and the passivation film 107. Even if it is a solar cell element having the structure shown in FIG. 8, it can be obtained and The same effect is shown in Fig. 7 (the first configuration example).

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 on only a part of the back surface side including the contact region (the opening portion OA portion) of the second electrode 106, instead of FIG. 7 (the first configuration) Example) is formed on the entire surface on the back side. Even in the solar cell element (FIG. 9) having such a configuration, the same effects as those of FIG. 7 (the 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 is doped with a group III element such as aluminum or boron, and a region having a higher concentration than the germanium substrate 101 is doped with impurities. Photoelectric conversion efficiency higher than that of Fig. 7 (first configuration example) can be obtained.

Next, a fourth configuration example shown in FIG. 10 will be described. In FIG. 9 (the third configuration example), the second electrode 106 is formed on the entire surface of the contact region (opening OA) and the passivation film 107, and in FIG. 10 (fourth configuration example), only the contact is made. The second electrode 106 is formed in the region (opening OA). It is also possible to adopt a configuration in which the second electrode 106 is formed on only a part of the contact region (opening OA) and the passivation film 107. Even in the solar cell element having the configuration shown in Fig. 10, the same effects as those in Fig. 9 (the third configuration example) can be obtained.

In addition, when the second electrode 106 is applied by a printing method and is formed on the entire surface on the back side by firing at a high temperature, warping of the upward convexity is likely to occur during the temperature lowering process. Such warpage sometimes causes damage to the solar cell components, and the yield may be lowered. In addition, the problem of warpage during the development of the thin film of the tantalum substrate becomes large. The reason for this warpage is that the second electrode 106 containing a metal (for example, aluminum) has a thermal expansion coefficient larger than that of the ruthenium substrate, so that the shrinkage during the cooling process is large, so Raw stress.

Based on the above, as shown in Figure 8 (the second configuration example) and Figure 10 (the fourth structure)

In the case where the second electrode 106 is not formed on the entire surface on the back side, the electrode structure is likely to be vertically symmetrical, and stress due to the difference in thermal expansion coefficient is less likely to occur, which is preferable. In this case, it is preferable to further provide a reflective layer.

<Method of Manufacturing Solar Cell Components>

Next, an example of a method of manufacturing the solar cell element (Figs. 7 to 10) of the present embodiment having the above configuration will be described. However, the present embodiment is not limited to the solar cell element produced by the method described below.

First, a texture structure is formed on the surface of the ruthenium substrate 101 shown in FIG. 7 and the like. The formation of the texture structure may be formed on both surfaces of the ruthenium substrate 101, or may be formed only on one side (the light-receiving surface side). In order to form a texture structure, the tantalum substrate 101 is first immersed in a solution of heated potassium hydroxide or sodium hydroxide to remove the damaged layer of the tantalum substrate 101. Thereafter, it is immersed in a solution containing potassium hydroxide and isopropyl alcohol as a main component, whereby a texture structure is formed on both surfaces or one side (light-receiving surface side) of the ruthenium substrate 101. Further, as described above, the solar cell element of the present embodiment may have a textured structure or a textured structure, and this step may be omitted.

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

Thereafter, a solution containing a coating type doping material such as boron or aluminum is applied to the back surface side of the tantalum substrate 101, and heat treatment is performed to form the BSF layer 104 on the back side. At the time of application, methods such as screen printing, inkjet, dispensing, and spin coating can be used. After the heat treatment, a layer such as borosilicate glass or aluminum formed on the back surface is removed by hydrofluoric acid, hydrochloric acid or the like to form the BSF layer 104. The method of forming the BSF layer 104 is not particularly limited. It is preferable that the BSF layer 104 is formed in such a manner that the concentration of boron, aluminum, or the like is in the range of 10 ¹⁸ cm ^-3 to 10 ²² cm ^-3 , and it is preferable to form the BSF layer 104 in a dot shape or a line shape. . Further, the solar cell element of the present embodiment may have the BSF layer 104 or may not have the BSF layer 104, and 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 solution of a coating-type dopant, the solution of the dopant may be applied to the substrate 101, respectively. On both sides, a phosphorus diffusion layer (n ⁺ layer) as the diffusion layer 102 is formed together with the BSF layer 104, and thereafter phosphorus glass, borosilicate glass or the like formed on the surface is removed together.

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

Then, a passivation film 107 is formed on the back side of the germanium substrate 101. The passivation film 107 contains aluminum oxide and cerium oxide, and is formed, for example, by imparting heat treatment (calcination) to a material (passivation material) containing an organic material which can be obtained by heat treatment (calcination) to obtain alumina. An alumina precursor represented by a metal decomposition coating type material and a cerium oxide precursor represented by a commercially available organometallic decomposition coating type material which can be obtained by heat treatment (calcination) to obtain cerium oxide.

The formation of the passivation film 107 can be performed, for example, as follows. The coating type material was spin-coated on a single 吋 (20.32 cm) p-type ruthenium substrate (8 Ω cm to 12 Ω cm) having a thickness of 725 μm in which the natural oxide film was 725 μm, which was previously prepared by using hydrofluoric acid having a concentration of 0.049% by mass. On the surface, prebaking was carried out on a hot plate at 120 ° C for 3 minutes. Thereafter, heat treatment was performed at 650 ° C for 1 hour under a nitrogen atmosphere. In this case, a passivation film containing aluminum oxide and cerium oxide can be obtained. The film thickness of the passivation film 107 formed by the method described above by an ellipsometer is usually about several tens of nanometers (nm).

The coating material is applied to a predetermined pattern including a contact region (opening OA) by a method such as screen printing, pattern printing, inkjet printing, or printing by a dispenser. In addition, the coating type material is preferably pre-baked in a range of 80 ° C to 180 ° C after the application, and the solvent is evaporated, and the atmosphere is exposed to nitrogen. Or heat treatment (annealing) in the air at 600 ° C to 1000 ° C for about 30 minutes to 3 hours to form a passivation film 107 (film of an oxide).

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

The passivation film 107 used in the above solar cell element preferably has a mass ratio of cerium oxide to aluminum oxide (yttria/alumina) of 30/70 to 90/10, more preferably 30/70 to 80/20, and further preferably It is 35/65~70/30. Thereby, the negative fixed charge can be stabilized. Further, from the viewpoint of improving the life of the carrier and the negative fixed charge, the mass ratio of cerium oxide to aluminum oxide is preferably 50/50 to 90/10.

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

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

Then, the second electrode 106 which is an electrode on the back side is formed. The second electrode 106 is formed by applying a paste containing aluminum as a main component using a screen printing or a dispenser, and heat-treating the same. Further, the shape of the second electrode 106 is preferably the same shape as that of the BSF layer 104, the shape of the entire surface covering the back surface side, a comb shape, a lattice shape, or the like. In addition, printing of a paste for forming the second electrode 106 of the first electrode 105 as an electrode on the light-receiving surface side may be performed first, respectively. Thereafter, heat treatment (burn-through) is performed to form the first electrode 105 and the second electrode 106 together.

Further, when the second electrode 106 is formed, aluminum is diffused as a dopant by using a paste containing aluminum (Al) as a main component, and the contact portion between the second electrode 106 and the ruthenium substrate 101 is self-aligned. A BSF layer 104 is formed. Further, as described above, a solution containing a coating type doping material such as boron or aluminum may be applied to the back surface side of the tantalum substrate 101, and the BSF layer 104 may be separately formed by heat treatment.

Further, the above shows a configuration example and a manufacturing example in which a p-type germanium is used for the germanium substrate 101, and an n-type germanium substrate can be used as the germanium 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. In this case, it is necessary to pay attention to the fact that the negative electrode formed on the interface and the portion in contact with the metal on the back side communicate with each other and the leakage current flows, and the conversion efficiency is hard to be improved.

Further, in the case of using an n-type germanium substrate, the passivation film 107 containing cerium oxide and aluminum oxide can be used for the light-receiving surface side as shown in FIG. FIG. 11 is a cross-sectional view showing a configuration example of a solar cell element using the light-receiving surface passivation film of the embodiment.

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

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

Hereinafter, reference is made to the reference embodiment and the reference comparative example of the present embodiment. One side will explain in detail.

[Reference Example 1-1]

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

The passivation material (a-1) was spin-coated on a single surface of an 8-inch p-type tantalum substrate (8 Ωcm to 12 Ωcm) having a thickness of 725 μm of a natural oxide film removed by using hydrofluoric acid having a concentration of 0.049% by mass. Prebaking was carried out on a hot plate at 120 ° C for 3 minutes. Thereafter, heat treatment (calcination) was carried out at 650 ° C for 1 hour in a nitrogen atmosphere to obtain a passivation film containing alumina and cerium oxide [cerium oxide/alumina = 68/32 (mass ratio)]. The film thickness was measured by an ellipsometer and found to be 43 nm. The FT-IR of the passivation film was measured, and as a result, a very weak peak derived from an alkyl group was observed in the vicinity of 1200 cm ^-1 .

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

In the same manner as described above, the passivation material (a-1) was applied to both surfaces of a p-type ruthenium substrate of 8 Å, prebaked, and heat-treated (calcined) at 650 ° C for 1 hour in a nitrogen atmosphere to prepare a ruthenium substrate. A sample covered on both sides by a passivation film. The measurement of the carrier lifetime of these samples was carried out by a life measuring device (Kobelco Research Institute Co., Ltd., RTA-540). The resulting carrier lifetime was 530 μs. For comparison, the same 8-inch p-type ruthenium substrate was passivated and measured by iodine passivation, and the carrier lifetime was 1100 μs.

From the above, it is known that the passivation film obtained by subjecting the passivation material (a-1) to heat treatment (calcination) exhibits a certain degree of passivation performance and exhibits a negative fixed charge.

[Reference Example 1-2]

In the same manner as in Reference Example 1-1, a commercially available organometallic decomposition coating material which can be obtained by heat treatment (calcination) of alumina (Al ₂ O ₃ ) [High Purity Chemical Research Institute Co., Ltd., SYM -AL04, a concentration of 2.3% by mass], and a commercially available organometallic decomposition coating material capable of obtaining cerium oxide (Nb ₂ O ₅ ) by heat treatment (calcination) [High Purity Chemical Research Institute Co., Ltd., Nb -05, a concentration of 5% by mass] was mixed and changed, and the passivation material (a-2) to passivation material (a-7) shown in Table 4 was prepared.

In the same manner as in Reference Example 1-1, the passivation material (a-2) to the passivation material (a-7) were respectively applied to one surface of the p-type germanium substrate, and heat treatment (calcination) was performed to prepare a passivation film. The voltage dependence of the capacitance of the obtained passivation film was measured, and the fixed charge density was calculated based on this.

Further, in the same manner as in Reference Example 1-1, a passivation material was applied to both surfaces of the p-type ruthenium substrate, and heat treatment (calcination) was performed, and the obtained sample was used to measure the carrier lifetime. The results obtained are summarized in Table 4.

Depending on the ratio (mass ratio) of cerium oxide/alumina after heat treatment (calcination), the results are different, but regarding the passivation material (a-2) to passivation material (a-7), the carrier life after heat treatment (calcination) It also shows a certain degree of value, so it is suggested to function as a passivation film. It is known that the passivation film obtained from the passivation material (a-2) to the passivation material (a-7) stably exhibits a negative fixed charge, and can also be preferably used as a passivation film of a p-type germanium substrate.

[Reference Example 1-3]

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

The passivation material (c-1) was spin-coated on a single surface of an 8-inch p-type tantalum substrate (8 Ωcm to 12 Ωcm) having a thickness of 725 μm of a natural oxide film removed by using hydrofluoric acid having a concentration of 0.049% by mass. Prebaking was carried out on a hot plate at 120 ° C for 3 minutes. Thereafter, heat treatment (calcination) was performed at 600 ° C for 1 hour in a nitrogen atmosphere to obtain a passivation film containing aluminum oxide and cerium oxide. The film thickness was measured by an ellipsometer and found to be 50 nm. As a result of performing elemental analysis, it was found that Nb/Al/C = 81/14/5 (% by mass). The FT-IR of the passivation film was measured, and as a result, a very weak peak derived from an alkyl group was observed in the vicinity of 1200 cm ^-1 .

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

In the same manner as described above, the passivation material (c-1) was applied to both surfaces of a p-type ruthenium substrate of 8 Å, prebaked, and heat-treated (calcined) at 600 ° C for 1 hour in a nitrogen atmosphere to prepare a ruthenium substrate. A sample covered by a passivation film on both sides. The measurement of the carrier lifetime of these samples was carried out by a life measuring device (Kobelco Research Institute Co., Ltd., RTA-540). The resulting carrier lifetime was 330 μs. For comparison, the same 8 吋 p is obtained by iodine passivation. The ruthenium substrate was passivated and measured, and the carrier lifetime was 1100 μs.

From the above, it is known that the passivation film obtained by subjecting the passivation material (c-1) to heat treatment (calcination) exhibits a certain degree of passivation performance and exhibits a negative fixed charge.

[Reference Examples 1-4]

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

The passivation material (c-2) was spin-coated on a single surface of an 8-inch p-type ruthenium substrate (8 Ωcm to 12 Ωcm) having a thickness of 725 μm of a natural oxide film removed by using hydrofluoric acid having a concentration of 0.049% by mass. Prebaking was carried out on a hot plate at 120 ° C for 3 minutes. Thereafter, heat treatment (calcination) was performed at 600 ° C for 1 hour in a nitrogen atmosphere to obtain a passivation film containing aluminum oxide and cerium oxide. The film thickness was measured by an ellipsometer and found to be 14 nm. As a result of elemental analysis, Nb/Al/C = 75/17/8 (% by mass) was obtained. The FT-IR of the passivation film was measured, and as a result, a very weak peak derived from an alkyl group was observed in the vicinity of 1200 cm ^-1 .

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

In the same manner as described above, the passivation material (c-2) was applied to both surfaces of a p-type ruthenium substrate of 8 Å, prebaked, and heat-treated (calcined) at 600 ° C for 1 hour in a nitrogen atmosphere to prepare a ruthenium substrate. A sample covered by a passivation film on both sides. The measurement of the carrier lifetime of the sample was carried out by a life measuring device (Kobelco Research Institute Co., Ltd., RTA-540). The resulting carrier lifetime was 200 μs. For comparison, the same 8-inch p-type ruthenium substrate was passivated and measured by iodine passivation, and the carrier lifetime was 1100 μs.

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

[Reference Examples 1-5 and Reference Comparative Example 1-1]

In the same manner as in Reference Example 1-1, a commercially available organometallic decomposition coating material which can obtain alumina (Al ₂ O ₃ ) by heat treatment (calcination) [SYM of High Purity Chemical Research Institute Co., Ltd.] -AL04, a concentration of 2.3% by mass], and a commercially available organometallic decomposition coating material capable of obtaining cerium oxide (Nb ₂ O ₅ ) by heat treatment (calcination) [Nb of High Purity Chemical Research Institute Co., Ltd. -05, the concentration was changed to 5% by mass], and the ratio was changed to prepare a passivation material (b-1) to a passivation material (b-7) shown in Table 5.

In the same manner as in Reference Example 1-1, the passivation material (b-1) to the passivation material (b-7) were respectively applied to one surface of the p-type germanium substrate, and heat treatment (calcination) was performed. A passivation film was produced, and the passivation film was used to measure the voltage dependence of the capacitance, and the fixed charge density was calculated based on this.

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

It was found that the passivation film obtained from the passivation material (b-1) to the passivation material (b-6) has a large carrier life and functions as a passivation layer. Further, in the case where the cerium oxide/alumina is 10/90 and 20/80, the value of the fixed charge density is largely deviated, and the negative fixed charge density cannot be stably obtained, but it can be confirmed that alumina and cerium oxide can be used. Achieve a negative fixed charge density. It has been found that when a passivation material having yttria/alumina of 10/90 and 20/80 is used for measurement by the CV method, it may become a passivation film which exhibits a positive fixed charge, and thus does not stably exhibit a negative fixation. Charge. Further, a passivation film exhibiting a positive fixed charge can be used as a passivation film of an n-type germanium substrate. On the other hand, the passivation material (b-7) in which the alumina reaches 100% by mass cannot obtain a negative fixed charge. density.

[Reference Comparative Example 1-2]

A commercially available organometallic decomposition coating material which can be obtained as a passivation material (d-1) by heat treatment (calcination) to obtain titanium oxide (TiO ₂ ) [Ti-03- of High Purity Chemical Research Institute Co., Ltd. P, a concentration of 3% by mass], a commercially available organometallic decomposition coating material capable of obtaining barium titanate (BaTiO ₃ ) by heat treatment (calcination) as a passivation material (d-2) [High Purity Chemistry Research] BT-06 of the company, a concentration of 6% by mass], and commercially available organometallic decomposition coating of lanthanum oxide (HfO ₂ ) which can be obtained by heat treatment (calcination) as a passivation material (d-3) Type material [Hf-05 of High Purity Chemical Research Institute Co., Ltd., concentration of 5% by mass].

In the same manner as in Reference Example 1-1, the passivation material (d-1) to the passivation material (d-3) were respectively applied to one surface of the p-type germanium substrate, and then heat treatment (calcination) was performed to prepare a passivation film. The passivation film measures the voltage dependence of the electrostatic capacitance, and calculates the fixed charge density based on this.

Further, in the same manner as in Reference Example 1-1, a passivation material was applied to both surfaces of the p-type ruthenium substrate, and a sample obtained by heat treatment (calcination) was used to measure the carrier lifetime. The results obtained are summarized in Table 6.

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

[Reference Examples 1-6]

A solar cell element having the structure shown in Fig. 9 was produced by using a single crystal germanium substrate doped with boron as the germanium substrate 101. After the surface of the ruthenium substrate 101 is subjected to a texture treatment, a coating-type phosphorus diffusion material is applied to the light-receiving surface side, and a diffusion layer 102 (phosphorus diffusion layer) is formed by heat treatment. Thereafter, the coated phosphorus diffusion material was removed using dilute hydrofluoric acid.

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

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

Then, on the light-receiving surface anti-reflection film 103 (SiN film) formed on the light-receiving surface side of the ruthenium substrate 101, a paste containing silver as a main component is screen-printed in the shape of a predetermined finger electrode and a bus bar electrode. On the back side, a paste with aluminum as a main component was screen printed onto the entire surface. Thereafter, heat treatment (burn-through) was performed at 850 ° C to form electrodes (first electrode 105 and second electrode 106), and aluminum was diffused into a portion of the opening OA of the back surface to form BSF layer 104, and FIG. 9 was formed. The structure of the sun shown Battery component.

In the silver electrode of the light-receiving surface, a burn-through step that does not open a hole in the SiN film is described. However, the opening portion OA may be formed in advance in the SiN film by etching or the like, and then a silver electrode may be formed.

For comparison, in the above-described fabrication step, the formation of the passivation film 107 is performed, and the aluminum paste is printed on the entire surface on the back side, and the p ⁺ layer 114 and the second electrode corresponding to the BSF layer 104 are formed on the entire surface. The corresponding electrode 116 forms a solar cell element having the structure shown in FIG. The solar cell elements were evaluated for characteristics (short circuit current, open circuit voltage, curve factor, and conversion efficiency). The evaluation of the characteristics was carried out in accordance with JIS-C-8913 (2005) and JIS-C-8914 (2005). The results are shown in Table 7.

As shown in Table 7, the solar cell element having the passivation film 107 containing the yttrium oxide and the aluminum oxide layer has an increase in the short-circuit current and the open-circuit voltage, and the conversion efficiency (photoelectric conversion efficiency) is the largest as compared with the solar cell element having no passivation film 107. Increase by 1%.

<Reference Embodiment 2>

The following is a passivation film, a coating material, a solar cell element, and a tantalum substrate with a passivation film according to the second embodiment.

<1> A passivation film containing an oxide of at least one vanadium element selected from the group consisting of vanadium oxide and cerium oxide, for use in a solar cell element having a ruthenium substrate.

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

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

The passivation film according to any one of <1> to <3> containing an oxide of two or three kinds of vanadium elements selected from the group consisting of vanadium oxide, cerium oxide and cerium oxide. It is an oxide of the above-mentioned vanadium group element.

The passivation film according to any one of <1> to <4> which is a heat-treated material of a coating material containing a precursor of alumina and a precursor selected from vanadium oxide. A precursor of an oxide of at least one vanadium element in the group consisting of precursors of cerium oxide and cerium oxide.

<6> A coating material comprising a precursor of alumina, a precursor of an oxide of at least one vanadium element selected from the group consisting of a precursor of vanadium oxide and a precursor of cerium oxide, A passivation film for forming a solar cell element having a germanium substrate.

<7> A solar cell element comprising: a p-type germanium substrate; the n-type impurity diffusion layer is formed on the first surface side as the light-receiving surface side of the germanium substrate; the first electrode is formed on the impurity diffusion layer; and the passivation film is formed on the germanium substrate and receives light The second surface is provided on the second surface side opposite to the surface side, and the second electrode is formed on the second surface side of the ruthenium substrate, and is electrically connected to the second surface side of the ruthenium substrate via the opening of the passivation film And the passivation film contains alumina and an oxide of at least one vanadium group element selected from the group consisting of vanadium oxide and cerium oxide.

<8> The solar cell element according to <7>, which has a p-type impurity diffusion layer formed on a part or all of the second surface side of the tantalum substrate, and is more dense than the tantalum substrate The high concentration is added with impurities, and the second electrode is electrically connected to the p-type impurity diffusion layer through the opening of the passivation film.

<9> A solar cell element comprising: an n-type germanium substrate; a p-type impurity diffusion layer formed on a first surface side of the light-receiving surface side of the germanium substrate; a first electrode formed on the impurity diffusion layer; and passivation The film is formed on the second surface side of the tantalum substrate opposite to the light receiving surface side, and has an opening; The second electrode is formed on the second surface side of the tantalum substrate, and is electrically connected to the second surface side of the tantalum substrate via an opening of the passivation film; and the passivation film contains alumina and is selected from vanadium oxide and An oxide of at least one vanadium element in the group consisting of cerium oxide.

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

The solar cell element according to any one of the above aspects, wherein the mass ratio of the oxide of the vanadium group element to the aluminum oxide in the passivation film is 30/70 to 90/10.

The solar cell element according to any one of the above aspects of the present invention, wherein the total content of the oxide of the vanadium group element and the aluminum oxide of the passivation film is 90% or more.

The solar cell element according to any one of <7> to <12> containing oxidation of two or three kinds of vanadium elements selected from the group consisting of vanadium oxide, cerium oxide and cerium oxide. The substance acts as an oxide of the above vanadium group element.

<14> A solar cell element according to any one of <1> to <5>, wherein: Passivation film.

According to the above-described reference embodiment, the passivation film which has a carrier life of the ruthenium substrate and has a negative fixed charge can be realized at 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 passivation film-attached germanium substrate having a negative carrier charge and a negative fixed charge can be realized at low cost.

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

Further, in the present embodiment, the amount of the fixed charge which the passivation film has can be controlled by changing the composition of the passivation film. Here, the vanadium group element refers to a group 5 element of the periodic table of elements, and is an element selected from the group consisting of vanadium, niobium and tantalum.

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

The mass ratio of the oxide of the vanadium group element to the aluminum oxide in the passivation film can be determined by energy dispersive X-ray spectroscopy (EDX), secondary ion mass spectrometry (SIMS), and high frequency inductively coupled plasma mass spectrometry ( ICP-MS) to determine. The specific measurement conditions are as follows, for example, in the case of ICP-MS. Dissolving the passivation film in an acid or alkaline aqueous solution, forming the solution into a mist and introducing it into the Ar plasma, and splitting the light emitted by the excited element back to the ground state to measure the wavelength and intensity, according to the obtained The wavelength is used to characterize the element, and the amount is quantified based on the obtained intensity.

The total content of the oxide of the vanadium group element and the 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 oxide of the vanadium group element and the components other than the alumina in the passivation film are increased, the effect of negatively fixing the charge becomes large.

Further, in the passivation film, from the viewpoint of improving the film quality and adjusting the elastic modulus, an oxide other than a vanadium element and a component other than alumina can be contained as an organic component. The presence of the organic component in the passivation film can be confirmed by elemental analysis and Fourier transform infrared spectroscopy (FT-IR) measurement of the film.

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

The passivation film may further contain, as an oxide of a vanadium group element, an oxide of two or three kinds of vanadium elements selected from the group consisting of vanadium oxide, cerium oxide, and cerium oxide.

The passivation film is preferably obtained by heat-treating a coating type material, and is more preferably obtained by coating a coating type material by a coating method or a printing method, and thereafter by heat treatment. Organic ingredients are removed. That is, the passivation film can also be obtained as a heat-treated product of a coating material containing a precursor of an oxide of an alumina precursor and an oxide of a vanadium group. The details of the coating material will be described later.

The coating material of the present embodiment is a coating material for a passivation film for a solar cell element having a ruthenium substrate, and includes a precursor of alumina and a precursor selected from a precursor of vanadium oxide and ruthenium oxide. A precursor of an oxide of at least one vanadium element in the constituent group. From the viewpoint of the negative fixed charge of the passivation film formed of the coating material, the precursor of the oxide of the vanadium element contained in the coating type material is preferably a precursor of selecting vanadium oxide (V ₂ O ₅ ). . The coating material may also contain a precursor of an oxide of two or three kinds of vanadium elements selected from the group consisting of a precursor of vanadium oxide, a precursor of cerium oxide, and a precursor of cerium oxide as a vanadium group. The precursor of the oxide of the element.

The alumina precursor can be used without particular limitation as long as it forms alumina. From the viewpoint of uniformly dispersing alumina on the ruthenium substrate and chemical stability, the alumina precursor is preferably an organic alumina precursor. Examples of the organic alumina precursors include 1,3-Misopropoxide (structural formula: Al(OCH(CH ₃ ) ₂ ) ₃ ), and SYM-AL04 of the Institute of High Purity Chemicals.

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

Examples of the organic vanadium oxide precursor include vanadium oxyacetate (V) (structural formula: VO(OC ₂ H ₅ ) ₃ , molecular weight: 202.13), and V- of the High Purity Chemical Research Institute (share). 02. Examples of the precursor of the organic cerium oxide include methanol oxime (V) (structural formula: Ta(OCH ₃ ) ₅ , molecular weight: 336.12), and Ta-10-P of the High Purity Chemical Research Institute. Examples of the organic cerium oxide precursor include cerium (V) (structural formula: Nb(OC ₂ H ₅ ) ₅ , molecular weight: 318.21), and Nb-05 of the High Purity Chemical Research Institute.

A coating material containing an organic oxide-containing vanadium element oxide precursor and an organic alumina precursor coating film is formed by a coating method or a printing method, and the organic component is removed by heat treatment thereafter. This gives a passivation film. Therefore, the passivation film can also be a passivation film containing an organic component. The content of the organic component in the passivation film is preferably less than 10% by mass, more preferably 5% by mass or less, and still more preferably 1% by mass or less.

The solar cell element (photoelectric conversion device) of the present embodiment has the passivation film (insulating film, protective insulating film) described in the above embodiment in the vicinity of the photoelectric conversion interface of the germanium substrate, that is, contains alumina and is selected from vanadium oxide. And a film of an oxide of at least one vanadium element in the group consisting of cerium oxide. By using an oxide containing at least one vanadium element selected from the group consisting of alumina and vanadium oxide and cerium oxide, the carrier life of the ruthenium substrate can be extended and a negative fixed charge can be obtained, thereby improving solar cell elements. Characteristics (photoelectric conversion efficiency).

The description of the structure and the manufacturing method of the solar cell element of the present embodiment can be referred to the description of the structure and the manufacturing method of the solar cell element according to the first embodiment.

Hereinafter, the reference embodiment and the reference comparative example of the present embodiment will be described in detail.

<Case of using vanadium oxide as an oxide of a vanadium group element> [Reference Example 2-1]

A commercially available organometallic thin film coating type material which can obtain alumina (Al ₂ O ₃ ) by heat treatment (calcination) [High Purity Chemical Research Institute, SYM-AL04, concentration: 2.3% by mass] 3.0 g, a commercially available organometallic thin film coating type material capable of obtaining vanadium oxide (V ₂ O ₅ ) by heat treatment (calcination) [High Purity Chemical Research Institute, V-02, concentration 2% by mass ] 6.0 g of a mixture was used to prepare a passivation material (a2-1) as a coating type material.

The passivation material (a2-1) was spin-coated on a 8-inch p-type tantalum substrate (8 Ω.cm to 12 Ω.cm) having a thickness of 725 μm of a natural oxide film removed by using hydrofluoric acid having a concentration of 0.49% by mass in advance. On one side, it was placed on a hot plate and prebaked at 120 ° C for 3 minutes. Thereafter, heat treatment (calcination) was performed at 700 ° C for 30 minutes in a nitrogen atmosphere to obtain a passivation film containing alumina and vanadium oxide [vanadium oxide / alumina = 63 / 37 (% by mass)]. The film thickness was measured by an ellipsometer and found to be 51 nm. The FT-IR of the passivation film was measured, and as a result, a very weak peak derived from an alkyl group was observed in the vicinity of 1200 cm ^-1 .

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

In the same manner as described above, the passivation material (a2-1) was applied to both surfaces of a 8 Å p-type ruthenium substrate, prebaked, and heat-treated (calcined) at 650 ° C for 1 hour in a nitrogen atmosphere to prepare ruthenium. A sample covered by a passivation film on both sides of the substrate. borrow The carrier life of the sample was determined by a life measuring device (Kobelco Research Institute, RTA-540). The resulting carrier lifetime was 400 μs. For comparison, the same 8-inch p-type ruthenium substrate was passivated and measured by iodine passivation, and the carrier lifetime was 1100 μs. Further, after 14 days from the preparation of the sample, the carrier life was measured again, and as a result, the carrier lifetime was 380 μs. From this, it was found that the decrease in carrier lifetime (400 μs to 380 μs) was within -10%, and the decrease in carrier lifetime was small.

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

[Reference Example 2-2]

In the same manner as in Reference Example 2-1, a commercially available organometallic thin film coating type material (High Purity Chemical Research Institute, SYM) which can obtain alumina (Al ₂ O ₃ ) by heat treatment (calcination) is used. -AL04, a concentration of 2.3% by mass], and a commercially available organometallic thin film coating type material capable of obtaining vanadium oxide (V ₂ O ₅ ) by heat treatment [High Purity Chemical Research Institute, V-02, The passivation material (a2-2) to the passivation material (a2-7) shown in Table 8 were prepared by mixing at a concentration of 2% by mass.

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

Then, the passivation material was applied to the p-type in the same manner as in Reference Example 2-1. The both sides of the substrate were subjected to heat treatment (calcination), and the obtained sample was used to measure the carrier lifetime.

The results obtained are summarized in Table 8. Further, after 14 days from the preparation of the sample, the carrier life was measured again, and as a result, the carrier lifetime of the passivation film using the passivation material (a2-2) to the passivation material (a2-7) shown in Table 8 was reduced - Within 10%, the decrease in carrier lifetime is small.

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

[Reference Example 2-3]

Commercially available vanadium oxyacetate (V) as a compound which can be obtained by heat treatment (calcination) to obtain vanadium oxide (V ₂ O ₅ ) (structural formula: VO(OC ₂ H ₅ ) ₃ , molecular weight: 202.13) 1.02 g (0.010 mol), and commercially available triisopropoxy aluminum as a compound which can be obtained by heat treatment (calcination) to obtain alumina (Al ₂ O ₃ ) (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 (b2-1) having a concentration of 5% by mass.

The passivation material (b2-1) was spin-coated on a 8-inch p-type tantalum substrate (8 Ω.cm to 12 Ω.cm) having a thickness of 725 μm of a natural oxide film removed by using hydrofluoric acid having a concentration of 0.49% by mass in advance. On one side, prebaking was carried out on a hot plate at 120 ° C for 3 minutes. Thereafter, heat treatment (calcination) was performed at 650 ° C for 1 hour in a nitrogen atmosphere to obtain a passivation film containing aluminum oxide and vanadium oxide. The film thickness was measured by an ellipsometer and found to be 60 nm. As a result of elemental analysis, it was found that V/Al/C = 64/33/3 (% by mass). The FT-IR of the passivation film was measured, and as a result, a very weak peak derived from an alkyl group was observed in the vicinity of 1200 cm ^-1 .

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

The passivation material (b2-1) was applied to both surfaces of a 8 Å p-type ruthenium substrate in the same manner as above, prebaked, and subjected to a nitrogen atmosphere at 600 ° C for 1 hour. The heat treatment (calcination) was performed to prepare a sample covered by a passivation film on both sides of the tantalum substrate. The carrier life of the sample was measured by a life measuring device (Kobelco Research Institute, RTA-540). The resulting carrier lifetime was 400 μs. For comparison, the same 8-inch p-type ruthenium substrate was passivated and measured by iodine passivation, and the carrier lifetime was 1100 μs.

From the above, it is known that the passivation film obtained by subjecting the passivation material (b2-1) to heat treatment (calcination) exhibits a certain degree of passivation performance and exhibits a negative fixed charge.

[Reference Example 2-4]

Commercially available vanadium oxyacetate (V) (structural formula: VO(OC ₂ H ₅ ) ₃ , molecular weight: 202.13) 1.52 g (0.0075 mol), commercially available triisopropoxy aluminum (structural formula: Al (OCH(CH ₃ ) ₂ ) ₃ , molecular weight: 204.25) 1.02 g (0.005 mol), and 10 g of novolac resin were dissolved in 10 g of diethylene glycol monobutyl ether acetate and 10 g of cyclohexane to prepare a passivation material ( B2-2).

The passivation material (b2-2) was spin-coated on a 8-inch p-type tantalum substrate (8 Ω.cm to 12 Ω.cm) having a thickness of 725 μm of a natural oxide film removed by using hydrofluoric acid having a concentration of 0.49% by mass in advance. On one side, it was placed on a hot plate and prebaked at 120 ° C for 3 minutes. Thereafter, the film was heated at 650 ° C for 1 hour in a nitrogen atmosphere to obtain a passivation film containing aluminum oxide and vanadium oxide. The film thickness was measured by an ellipsometer and found to be 22 nm. As a result of elemental analysis, it was found that V/Al/C = 71/22/7 (% by mass). The FT-IR of the passivation film was measured, and as a result, a very weak peak derived from an alkyl group was observed in the vicinity of 1200 cm ^-1 .

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

In the same manner as described above, the passivation material (b2-2) was applied to both surfaces of a 8 Å p-type ruthenium substrate, prebaked, and heat-treated (calcined) at 600 ° C for 1 hour in a nitrogen atmosphere to prepare ruthenium. A sample covered by a passivation film on both sides of the substrate. The carrier life of the sample was measured by a life measuring device (Kobelco Research Institute, RTA-540). The resulting carrier lifetime was 170 μs. For comparison, the same 8-inch p-type ruthenium substrate was passivated and measured by iodine passivation, and the carrier lifetime was 1100 μs.

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

<Case of using cerium oxide as an oxide of a vanadium group element> [Reference Example 2-5]

A commercially available organometallic thin film coating type material (high purity chemical research institute, SYM-AL04, concentration: 2.3% by mass) which can obtain alumina (Al ₂ O ₃ ) by heat treatment (calcination), A ratio of change in a commercially available organometallic thin film coating type material (high purity chemical research institute, Ta-10-P, concentration: 10% by mass) which can be obtained by heat treatment to obtain cerium oxide (Ta ₂ O ₅ ) While mixing, the passivation material (c2-1) to passivation material (c2-6) shown in Table 9 was prepared.

The passivation material (c2-1) to the passivation material (c2-6) were spin-coated on the 8-inch p-type germanium substrate having a thickness of 725 μm in which the natural oxide film was removed by using hydrofluoric acid having a concentration of 0.49% by mass in advance ( One side of 8 Ω.cm~12 Ω.cm) was placed on a hot plate and pre-baked at 120 ° C for 3 minutes. Thereafter, heat treatment (calcination) was performed at 700 ° C for 30 minutes in a nitrogen atmosphere to obtain a passivation film containing aluminum oxide and cerium oxide. The passivation film was used to measure the voltage dependence of the electrostatic capacitance, and the fixed charge density was calculated based on this.

Then, the passivation material (c2-1) to the passivation material (c2-6) were respectively applied to both surfaces of a 8 Å p-type ruthenium substrate, prebaked, and subjected to a nitrogen atmosphere at 650 ° C for 1 hour. Heat treatment (calcination), and a sample covered with a passivation film on both sides of the tantalum substrate was prepared. The carrier life of the sample was measured by a life measuring device (Kobelco Research Institute, RTA-540).

The results obtained are summarized in Table 9. Further, after 14 days from the preparation of the sample, the carrier lifetime was measured again, and as a result, it was found that the carrier lifetime of the passivation film using the passivation material (c2-1) to the passivation material (c2-6) shown in Table 9 was lowered. Within -10%, the decrease in carrier lifetime is small.

Depending on the ratio (mass ratio) of yttria/alumina after heat treatment (calcination), the results are different, but the passivation material (c2-1)~passivation material (c2-6) is hot After the treatment (calcination), the negative fixed charge is exhibited, and the carrier lifetime also shows a certain value, so it is suggested to function as a passivation film.

[Reference Example 2-6]

Commercially available methanol oxime (V) (structure: Ta(OCH ₃ ) ₅ , molecular weight: 336.12) 1.18 g (0.0025 mol) as a compound capable of obtaining cerium oxide (Ta ₂ O ₅ ) by heat treatment (calcination) And commercially available triisopropoxy aluminum as a compound which can be obtained by heat treatment (calcination) to obtain alumina (Al ₂ O ₃ ) (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.

The passivation material (d2-1) was spin-coated on a 8-inch p-type tantalum substrate (8 Ω.cm to 12 Ω.cm) having a thickness of 725 μm of a natural oxide film removed by using hydrofluoric acid having a concentration of 0.49% by mass in advance. On one side, it was placed on a hot plate and prebaked at 120 ° C for 3 minutes. Thereafter, the film was heated at 700 ° C for 1 hour in a nitrogen atmosphere to obtain a passivation film containing aluminum oxide and cerium oxide. The film thickness was measured by an ellipsometer and found to be 40 nm. As a result of elemental analysis, it was found that Ta/Al/C = 75/22/3 (wt%). The FT-IR of the passivation film was measured, and as a result, a very weak peak derived from an alkyl group was observed in the vicinity of 1200 cm ^-1 .

Then, on the passivation film, a plurality of aluminum electrodes having a diameter of 1 mm were formed by vapor deposition to form a capacitor of a metal-insulator-semiconductor (MIS) structure. The voltage dependence (CV characteristic) of the capacitance of the capacitor was measured by a commercially available prober and an LCR meter (HP company, 4275A). The results show that the flat band voltage (Vfb) is shifted from the ideal value of -0.81V to -0.30V. From the amount of movement, it was found that the passivation film obtained from the passivation material (d2-1) showed a fixed charge having a fixed charge density (Nf) of -6.2 × 10 ¹⁰ cm ^-2 and a negative value.

In the same manner as described above, the passivation material (d2-1) was applied to both surfaces of a 8 Å p-type ruthenium substrate, prebaked, and heat-treated (calcined) at 600 ° C for 1 hour in a nitrogen atmosphere to prepare ruthenium. A sample covered by a passivation film on both sides of the substrate. The carrier life of the sample was measured by a life measuring device (Kobelco Research Institute, RTA-540). The resulting carrier lifetime was 610 μs. For comparison, the same 8-inch p-type ruthenium substrate was passivated and measured by iodine passivation, and the carrier lifetime was 1100 μs.

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

[Reference Examples 2-7]

Commercially available methanol oxime (V) which is a compound which can obtain yttrium oxide (Ta ₂ O ₅ ) by heat treatment (calcination) (structural formula: Ta(OCH ₃ ) ₅ , molecular weight: 336.12) 1.18 g (0.005 mol) As a commercially available compound of aluminum oxide (Al ₂ O ₃ ) which can be obtained by heat treatment (calcination), aluminum triisopropoxide (structural formula: Al(OCH(CH ₃ ) ₂ ) ₃ , molecular weight: 204.25 1.02 g (0.005 mol) and 10 g of a novolac resin were dissolved in a mixture of 10 g of diethylene glycol monobutyl ether acetate and 10 g of cyclohexane to prepare a passivation material (d2-2).

The passivation material (d2-2) was spin-coated on a 8-inch p-type ruthenium substrate (8 Ω.cm to 12 Ω.cm) having a thickness of 725 μm of a natural oxide film removed by using hydrofluoric acid having a concentration of 0.49% by mass in advance. On one side, prebaking was carried out on a hot plate at 120 ° C for 3 minutes. Thereafter, the film was heated at 650 ° C for 1 hour in a nitrogen atmosphere to obtain a passivation film containing aluminum oxide and cerium oxide. The film thickness was measured by an ellipsometer and found to be 18 nm. As a result of elemental analysis, it was found that Ta/Al/C = 72/20/8 (wt%). The FT-IR of the passivation film was measured, and as a result, a very weak peak derived from an alkyl group was observed in the vicinity of 1200 cm ^-1 .

Then, on the passivation film, a plurality of aluminum electrodes having a diameter of 1 mm were formed by vapor deposition to form a capacitor of a metal-insulator-semiconductor (MIS) structure. The voltage dependence (CV characteristic) of the capacitance of the capacitor was measured by a commercially available prober and an LCR meter (HP company, 4275A). The results show that the flat band voltage (Vfb) is shifted from the ideal value of -0.81V to -0.43V. From the amount of movement, it was found that the passivation film obtained from the passivation material (d-2) showed a fixed charge having a fixed charge density (Nf) of -5.5 × 10 ¹⁰ cm ^-2 and a negative value.

The passivation material (d2-2) was applied to 8 吋 p-type 同样 in the same manner as described above. Both sides of the substrate were prebaked, and heat-treated (calcined) at 600 ° C for 1 hour in a nitrogen atmosphere to prepare a sample covered with a passivation film on both sides of the substrate. The carrier life of the sample was measured by a life measuring device (Kobelco Research Institute, RTA-540). The resulting carrier lifetime was 250 μs. For comparison, the same 8-inch p-type ruthenium substrate was passivated and measured by iodine passivation, and the carrier lifetime was 1100 μs.

From the above, it is known that the passivation film obtained by subjecting the passivation material (d2-2) to heat treatment (calcination) exhibits a certain degree of passivation performance and exhibits a negative fixed charge.

<Case of using two or more oxides of vanadium elements> [Reference Example 2-8]

A commercially available organometallic thin film coating type material (high purity chemical research institute, SYM-AL04, concentration: 2.3% by mass) which can obtain alumina (Al ₂ O ₃ ) by heat treatment (calcination), A commercially available organometallic thin film coating type material capable of obtaining vanadium oxide (V ₂ O ₅ ) by heat treatment (calcination) [High Purity Chemical Research Institute, V-02, concentration: 2% by mass], and A commercially available organometallic thin film coating type material obtained by heat treatment (calcination) of lanthanum oxide (Ta ₂ O ₅ ) [High Purity Chemical Research Institute, Ta-10-P, concentration: 10% by mass] The passivation material (e2-1) as a coating type material was prepared by mixing (refer to Table 10).

A commercially available organometallic thin film coating type material (high purity chemical research institute, SYM-AL04, concentration: 2.3% by mass) which can obtain alumina (Al ₂ O ₃ ) by heat treatment (calcination), A commercially available organometallic thin film coating type material capable of obtaining vanadium oxide (V ₂ O ₅ ) by heat treatment (calcination) [High Purity Chemical Research Institute, V-02, concentration: 2% by mass], and A commercially available organometallic thin film coating type material (high purity chemical research institute, Nb-05, concentration: 5% by mass) which can obtain cerium oxide (Nb ₂ O ₅ ) by heat treatment (calcination), A passivation material (e2-2) as a coating type material was prepared (refer to Table 10).

A commercially available organometallic thin film coating type material (high purity chemical research institute, SYM-AL04, concentration: 2.3% by mass) which can obtain alumina (Al ₂ O ₃ ) by heat treatment (calcination), A commercially available organometallic thin film coating type material obtained by heat treatment (calcination) of lanthanum oxide (Ta ₂ O ₅ ) [High Purity Chemical Research Institute, Ta-10-P, concentration: 10% by mass] And a commercially available organometallic thin film coating type material which can obtain cerium oxide (Nb ₂ O ₅ ) by heat treatment (calcination) [High Purity Chemical Research Institute, Nb-05, concentration: 5% by mass] The passivation material (e2-3) as a coating type material was prepared by mixing (refer to Table 10).

A commercially available organometallic thin film coating type material (high purity chemical research institute, SYM-AL04, concentration: 2.3% by mass) which can obtain alumina (Al ₂ O ₃ ) by heat treatment (calcination), A commercially available organometallic thin film coating type material capable of obtaining vanadium oxide (V ₂ O ₅ ) by heat treatment (calcination) [High Purity Chemical Research Institute, V-02, concentration: 2% by mass], A commercially available organometallic thin film coating type material obtained by heat treatment (calcination) of lanthanum oxide (Ta ₂ O ₅ ) [High Purity Chemical Research Institute, Ta-10-P, concentration: 10% by mass], And a commercially available organometallic thin film coating type material (high purity chemical research institute, Nb-05, concentration: 5% by mass) which can obtain cerium oxide (Nb ₂ O ₅ ) by heat treatment (calcination) A passivation material (e2-4) as a coating type material was prepared (refer to Table 10).

The passivation material (e2-1) to the passivation material (e2-4) were spin-coated in the same manner as in Reference Example 2-1, respectively, and the thickness of the natural oxide film was 725 μm by using hydrofluoric acid having a concentration of 0.49% by mass in advance. On one side of a 8 inch p-type ruthenium substrate (8 Ω.cm to 12 Ω.cm), it was placed on a hot plate and prebaked at 120 ° C for 3 minutes. Thereafter, heat treatment (calcination) was performed at 650 ° C for 1 hour in a nitrogen atmosphere to obtain a passivation film containing an oxide of alumina and two or more kinds of vanadium group elements.

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

Then, the passivation material (e2-1) to the passivation material (e2-4) were respectively applied to both surfaces of a 8 Å p-type ruthenium substrate, prebaked, and subjected to a nitrogen atmosphere at 650 ° C for 1 hour. Heat treatment (calcination), and a sample covered with a passivation film on both sides of the tantalum substrate was prepared. The carrier life of the sample was measured by a life measuring device (Kobelco Research Institute, RTA-540).

The results obtained are summarized in Table 10.

Depending on the ratio (mass ratio) of oxides of two or more kinds of vanadium elements after heat treatment (calcination), the results are different, but passivation using passivation material (e2-1) to passivation material (e2-4) The film showed a negative fixed charge after heat treatment (calcination), and the carrier lifetime also showed a certain value, so it was suggested to function as a passivation film.

[Reference Example 2-9]

In the same manner as in Reference Example 2-1, a commercially available organometallic thin film coating type material (High Purity Chemical Research Institute, SYM) which can obtain alumina (Al ₂ O ₃ ) by heat treatment (calcination) is used. -AL04, a concentration of 2.3% by mass], a commercially available organometallic thin film coating type material capable of obtaining vanadium oxide (V ₂ O ₅ ) by heat treatment (calcination) [High Purity Chemical Research Institute, V- 02, a concentration of 2% by mass], or a commercially available organometallic thin film coating type material which can obtain cerium oxide (Ta ₂ O ₅ ) by heat treatment (calcination) [High Purity Chemical Research Institute, Ltd., Ta- 10-P, a concentration of 10% by mass] was mixed, and a passivation material (f2-1) to passivation material (f2-8) as a coating material was prepared (refer to Table 10).

Further, a passivation material (f2-9) using alumina alone was prepared (refer to Table 11).

In the same manner as in Reference Example 2-1, the passivation material (f2-1) to the passivation material (f2-9) were applied to one surface of the p-type germanium substrate, respectively, and then heat-treated (calcined) to prepare a passivation film. Using the passivation film to measure the voltage dependence of the electrostatic capacitance, Based on this, the fixed charge density is calculated.

Further, in the same manner as in Reference Example 2-1, the passivation material (f2-1) to the passivation material (f2-9) were respectively applied to both surfaces of the p-type germanium substrate, and heat treatment (calcination) was performed, and the obtained sample was used. To determine the carrier lifetime. The results obtained are summarized in Table 11.

As shown in Table 11, when the alumina/vanadium oxide or yttrium oxide in the passivation material is 90/10 and 80/20, the deviation of the value of the fixed charge density is large, and the negative fixed charge density cannot be stably obtained. However, it was confirmed that a negative fixed charge density can be achieved by using alumina and cerium oxide. It has been found that when a passivation material using alumina, vanadium oxide or yttrium oxide of 90/10 and 80/20 is measured by the CV method, it may become a passivation film which exhibits a positive fixed charge, and thus is not stably Showing a negative fixed charge. Further, a passivation film exhibiting a positive fixed charge can be used as a passivation film of an n-type germanium substrate. On the other hand, the passivation material (f2-9) in which the alumina reaches 100% by mass cannot obtain a negative fixed charge density.

[Reference Example 2-10]

A single crystal germanium substrate using boron as a dopant was used as the germanium substrate 101, and a solar cell element having the structure shown in Fig. 9 was produced. After the surface of the ruthenium substrate 101 is subjected to a texture treatment, only the coating-type phosphorus diffusion material is applied to the light-receiving surface side, and the diffusion layer 102 (phosphorus diffusion layer) is formed by heat treatment. Thereafter, the coated phosphorus diffusion material was removed using dilute hydrofluoric acid.

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

Then, on the light-receiving surface anti-reflection film 103 (SiN film) formed on the light-receiving surface side of the ruthenium substrate 101, a paste containing silver as a main component is screen-printed in the shape of a predetermined finger electrode and a bus bar electrode. On the back side, a paste with aluminum as a main component was screen printed onto the entire surface. Thereafter, heat treatment (burn-through) was performed at 850 ° C to form electrodes (first electrode 105 and second electrode 106), and aluminum was diffused into a portion of the opening OA of the back surface to form BSF layer 104, and FIG. 9 was formed. The solar cell element of the structure shown.

Further, in the formation of the silver electrode on the light-receiving surface, a burn-through step in which the SiN film is not formed is described. However, the opening portion OA may be formed in advance in the SiN film by etching or the like, and then the silver electrode may be formed. .

For comparison, in the above-described fabrication step, the formation of the passivation film 107 is performed, and the aluminum paste is printed on the entire surface on the back side, and the p ⁺ layer 114 and the second electrode corresponding to the BSF layer 104 are formed on the entire surface. The corresponding electrode 116 forms the solar cell element of the structure of Fig. 6. The solar cell elements were evaluated for characteristics (short circuit current, open circuit voltage, curve factor, and conversion efficiency). The evaluation of the characteristics was carried out in accordance with JIS-C-8913 (2005) and JIS-C-8914 (2005). The results are shown in Table 12.

As shown in Table 12, the solar cell element having the passivation film 107 was increased in both the short-circuit current and the open-circuit voltage as compared with the solar cell element having no passivation film 107, and the conversion efficiency (photoelectric conversion efficiency) was increased by 0.6% at the maximum.

Japanese Patent Application No. 2012-160336, Japanese Patent Application No. 2012-218389, Japanese Patent Application No. 2013-011934, Japanese Patent Application No. 2013-040153, and Japanese Patent Application No. 2013-040154 All disclosures are incorporated herein by reference. All the documents, Japanese patent application, and technical standards described in the present specification are incorporated herein by reference in the same manner as the following. The literature, Japanese patent applications, and technical standards are incorporated by reference.

12‧‧‧n type diffusion zone

12a, 14a‧‧‧ short side

12b, 14b‧‧‧ long side

12c, 14c‧‧‧ rectangular part

14‧‧‧p-type diffusion zone

Claims (17)

A solar cell element comprising: a semiconductor substrate having a light-receiving surface and a back surface opposite to the light-receiving surface; and 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; and a passivation layer Provided in a part or all of the back surface of the semiconductor substrate, and 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 first metal electrode disposed at least a portion of the p-type diffusion region; and a second metal electrode disposed at least a portion of the n-type diffusion region, wherein the passivation layer is a heat-treated material, and the heat-treated material is formed of a passivation layer The composition for forming a passivation layer further contains one or more selected from the group consisting of Al ₂ O ₃ and a compound represented by the following general formula (II), which is obtained by heat-treating the composition. In the formula (II), R ² each independently represents an alkyl group having 1 to 8 carbon atoms; n represents an integer of 0 to 3; and X ² and X ³ each independently represent an oxygen atom or a methylene group; and R ³ and R; ⁴ and R ⁵ each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. The solar cell element according to claim 1, wherein the p-type diffusion region and the n-type diffusion region are disposed apart from each other, and each includes a plurality of rectangular portions having short sides and long sides, and the p-type The plurality of rectangular portions included in the diffusion region are disposed such that a longitudinal direction of the plurality of rectangular portions is along a longitudinal direction of the plurality of rectangular portions of the n-type diffusion region, and the p-type diffusion region has The plurality of rectangular portions are alternately arranged with the plurality of rectangular portions of the n-type diffusion region. The solar cell element according to claim 1 or 2, wherein the solar cell element has a back contact structure. The solar cell element according to claim 1, wherein the passivation layer forming composition contains a material selected from the group consisting of Nb ₂ O ₅ , Ta ₂ O ₅ , V ₂ O ₅ , Y ₂ O ₃ , HfO ₂ and the following One or more of the groups consisting of the compounds represented by the formula (I), wherein M has a group selected from the group consisting of Nb, Ta, V, Y and Hf, in the formula M(OR ¹ ) _m (I) At least one metal element; R ¹ independently represents an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 14 carbon atoms; and m represents an integer of 1 to 5. The solar cell element according to claim 1, wherein in the above formula (II), R ^{2 is} independently an alkyl group having 1 to 4 carbon atoms. The solar cell element according to claim 1 or 5, wherein in the above formula (II), n is an integer of 1 to 3, and R ^{5 is} independently a hydrogen atom or a carbon number of 4 or 5 Alkyl. The solar cell element according to the first aspect of the invention, wherein the composition for forming a passivation layer contains one or more selected from the group consisting of a compound represented by Al ₂ O ₃ and the above formula (II). In the aluminum compound, the content of the aluminum compound in the composition for forming a passivation layer is from 0.1% by mass to 80% by mass. The solar cell element according to claim 4, wherein the passivation layer forming composition contains one selected from the group consisting of Nb ₂ O ₅ and a compound of the above formula (I) wherein M is Nb. In the above-mentioned ruthenium compound, the total content of the ruthenium compound in the composition for forming a passivation layer is 0.1% by mass to 99.9% by mass in terms of Nb ₂ O ₅ . The solar cell element according to claim 1, wherein the composition for forming a passivation layer contains a liquid medium. The solar cell element according to claim 9, wherein the liquid medium contains a group selected from the group consisting of a hydrophobic organic solvent, an aprotic organic solvent, a terpene solvent, an ester solvent, an ether solvent, and an alcohol solvent. At least one of them. The solar cell element according to claim 1, wherein the passivation layer has a density of 1.0 g/cm ³ to 10.0 g/cm ³ . The solar cell element according to claim 1, wherein the passivation layer has an average thickness of 5 nm to 50 μm. A method of manufacturing a solar cell element, wherein the solar cell element according to any one of claims 1 to 12, further comprising: a light receiving surface and a back surface opposite to the light receiving surface; and having the back surface a step of forming a first metal electrode on at least a portion of the p-type diffusion region and the p-type diffusion region of the semiconductor substrate of the n-type diffusion region, and forming a second metal electrode on at least a portion of the n-type diffusion region; and the semiconductor substrate a part of or all of the back surface is provided with a composition for forming a passivation layer to form a composition layer, and the composition for forming a passivation layer contains a material selected from the group consisting of Nb ₂ O ₅ , Ta ₂ O ₅ , V ₂ O ₅ , and Y. One or more of a group consisting of ₂ O ₃ , HfO ₂ and a compound represented by the following formula (I); and heat-treating the above-mentioned composition layer to form a content selected from the group consisting of Nb ₂ O ₅ and Ta ₂ O ₅ , a step of one or more passivation layers in a group consisting of V ₂ O ₅ , Y ₂ O ₃ and HfO ₂ ; M(OR ¹ ) _m (I) wherein M contains a group selected from Nb, Ta, V In the group consisting of Y, Y and Hf One metal element; R & lt each independently represent ^a C 1-10 alkyl or aryl group having a carbon number of 6 to 14, 1 to 8; m represents an integer of 1 to 5. The method for producing a solar cell element according to claim 13, wherein the passivation layer forming composition further contains a group selected from the group consisting of Al ₂ O ₃ and a compound represented by the following formula (II). One or more of them, In the formula, R ² each independently represents an alkyl group having 1 to 8 carbon atoms; n represents an integer of 0 to 3; and X ² and X ³ each independently represent an oxygen atom or a methylene group; and R ³ , R ⁴ and R ⁵ Each independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. The method for producing a solar cell element according to claim 13 or claim 14, wherein the temperature of the heat treatment is 400 ° C or higher. The method for producing a solar cell element according to claim 13, wherein the step of forming the composition layer includes providing the composition for forming a passivation layer by a screen printing method or an inkjet method. A solar cell module according to any one of claims 1 to 12, and a wiring material disposed on an electrode of the solar cell element.